volume 19 january - june 2004 numbers 1-2 volume 19 october - … 19, no.4.pdf · certification of...

Volume 19 January - June 2004 Numbers 1-2Volume 19 October - December 2004 Number 4

EDITORIAL BOARD

Dr. Joachim FischerDepartment of Temperature and HeatPhysikalisch-Technische Bundesanstalt (PTB)Abbestrasse 2-1210587, BerlinGERMANYFax : +49 30 3481 508e-mail : [email protected]

Dr. Ashok Kumar GuptaNational Physical LaboratoryDr. K.S. Krishnan MargNew Delhi-110 012INDIAFax : +91-11-25726938e-mail : [email protected]

Dr. Werner HaesselbarthFederal Institute for Materials Research and Testing(BAM)Referat I.0112200, BerlinGERMANYFax : +49 30 8104 5577e-mail : [email protected]

Dr. Leonard HanssenOptical Technology DivisionNational Institute of Standards and Technology100 Bureau Dr., Stop 8442Gaithersburg, MD 20899-8442U.S.A.Fax : 301-840-8551e-mail : [email protected]

Dr. M.K. HossainNational Physical LaboratoryQueens RoadTeddington, Middlesex TW 11 0LWUNITED KINGDOMFax : 020 8943 6407e-mail : [email protected]

Dr. Krishan LalNational Physical LaboratoryDr. K.S. Krishnan MargNew Delhi-110 012INDIAFax : +91-11-25726938e-mail : [email protected]

Dr. B.S. MathurNational Physical LaboratoryDr. K.S. Krishnan MargNew Delhi-110 012INDIAFax : +91-11-25726938e-mail : [email protected]

Dr. Baldev RajIndira Gandhi Centre for Atomic ResearchKalpakkam-603 102, TamilnaduINDIAFax : +91-4114-480301/480060/480356e-mail : [email protected]

Prof. A.R. Verma160, Deepali EnclaveNear Saraswati ViharPitam PuraDelhi-110 034INDIA

Prof. Dr. Franz WäldelePhysikalisch - Technische Bundesanstalt (PTB)Bundesallee 10038116, BraunschweigGERMANYFax : +49 531 5925305e-mail : [email protected]

Dr. Sam-Yong WooDivision of Physical MetrologyKorea Research Institute of Standards and Science(KRISS)POB 102 YuseongDaejeon 305-600REPUBLIC OF KOREAFax : ++82 42 868 5117e-mail : [email protected]

Preface

This special issue is devoted to current topics in metrology in chemistry, i.e. thescience of chemical measurements. This statement is not likely to go unchallenged, becausecurrent interpretations of the term "metrology in chemistry" cover a wide range, from dis-semination of the "chemical" base unit "mol" by national metrology institutes over qualityassurance and quality control in chemical analysis focussing on measurement uncertaintyand traceability to a synonym for the entire field of (quantitative) chemical analysis.

Judging from the number of publications utilizing the key words "metrology", "un-certainty" and "traceability" in conjunction with topics of analytical chemistry, metrology inchemistry is a rapidly developing field. This may in particular be due to the impact of ISO/IEC 17025, which requires testing laboratories to assess the uncertainty and traceability of(quantitative) test results, while in ISO Guide 25 this was only required from calibrationlaboratories. As to implementations of these requirements, currently expectations on chemicaltesting laboratories are comparatively high, because chemical measurements are generallyfelt to be closer to calibrations than most other (quantitative) tests.

Metrology in chemistry has also been a rapidly developing field for national metrol-ogy institutes, many of which have established departments dedicated to this topic. Thisdevelopment is reflected in that of the Comité Consultatif de la Quantité de Matière (CCQM),which after 10 years is by far the largest sectorial committee of the International Committeefor Weights and Measures (CIPM), comprising seven active working groups, having carriedout more than 120 intercomparisons and supervising approximately 3000 entries in the CMCdata base maintained by the BIPM. Responding to these developments, the regional metrol-ogy organizations such as APMP and EUROMET have established mirror committees formetrology in chemistry.

Among other merits, metrology in chemistry has re-introduced the concept of "abso-lute" or "definitive" methods of analysis, now called "primary methods of measurement".These are measurement methods, which are completely understood, and for which a com-plete measurement equation and uncertainty budget are available. The key feature of thesemethods is that they do not require any empirical corrections or calibrations. The CCQMhas identified a number of chemical measurement methods, which have a primary poten-tial. The scientific debate of this concept has resulted in further differentiation (absolutevs. ratio methods) and clarified that the primary potential is dependent on the target level ofmeasurement uncertainty.

The articles in this special issue were contributed by a number of lead scientists inthe field of metrology in chemistry, whom the Guest Editor of this special issue has thebenefit to know personally, as invited papers on topics agreed with the Publication & Infor-mation Committee of Metrology Society of India (MSI). The extraordinary support for thisproject received from all of the authors and the invitation from the Society to be the GuestEditor of this special issue are gratefully acknowledged.

Dated: December, 2004 Guest EditorWERNER HAESSELBARTH

Federal Institute for Materials Research and Testing (BAM)Berlin, Germany

MAPAN - Journal of Metrology Society of India, Vol. 19, No. 4, 2004; pp. 189

189

Published by :

Metrology Society of India

Printed by :

Alpha PrintersCB-94, Naraina, Ring RoadNew Delhi-110 028Mobile : 9313781811

9313781749

ISSN 0970 — 3950RNI Regn. No. 45863/86

MAPAN — Journal of Metrology Society of IndiaEditorMr. S.U.M. Rao

Associate EditorsDr. Ashok KumarDr. R.K. GargMr. V.K. Rustagi

Managing EditorMr. Anil Kumar

Editor EmeritusDr. P.C. Jain

Guest EditorDr. W. Haesselbarth

Publication &InformationCommitteeChairmanDr. R.K. Garg

MembersDr. Ashok KumarDr. P.C. JainDr. Mahavir SinghMr. S.U.M. RaoMr. V.K. RustagiDr. Sanjay YadavMr. A.K. SaxenaDr. R.P. SinghalDr. Sukhvir SinghMr. N.K. WadhwaDr. Yudhisther Kumar

SecretaryMr. Anil Kumar

CONTENTS

Preface 189

Recent Developments in Metrology in Chemistry 191Robert Kaarls

Metrological Challenges in Bioanalysis 197Helen Parkes

Update on COMAR - the Internet Database for 203Certified Reference MaterialsThomas Steiger and Rita Pradel

Present Status of Certified Reference Materials in India 209A.K. Agrawal

The Provision of Reference Materials in Japan 219Toshiaki Asakai

The Reference Materials Programme at the Australian 239National Measurement InstituteL.M. Besley

Certification of In-house Reference Materials 245Ilya Kuselman

Correlation in Chemical and Other Measurements 253Werner Haesselbarth and Wolfram Bremser

Volume Contents 264

Author Index 267

Volume 19 October - December 2004 Number 4

Publication of MAPAN-JMSI is financiallysupported by Depart-ment of Science andTechnology (DST),Government of India.

Abstracted byINSPEC

Copyright Reserved

Address for Correspondence :

Mr. Anil KumarManaging Editor, MAPAN-JMSIMetrology Society of IndiaNPL Premises, Dr. K.S. Krishnan MargNew Delhi-110 012, Indiae-mail : [email protected] : 91-11-25726938, 25732965

Focal Theme : Metrology in Chemistry

191

Recent Developments in Metrology in Chemistry

1. Introduction

Since the establishment of the ConsultativeCommittee for Amount of Substance - Metrologyin Chemistry (CCQM) in 1993, enormous progresshas been made in establishing worldwidecomparability of measurement results in chemistry.In the mean time the CCQM, being one of the ten

© Metrology Society of India, All rights reserved.


ROBERT KAARLSSecretary CIPM, President CCQM

National Metrology InstituteSchoemakerstraat 97, 2600 AR Delft

The Netherlandse-mail: [email protected]

[Received : 08.07.2004]

Abstract

The work and progress made by the CCQM and its working groups since its creation in 1993 isdescribed. The scope of work of the recently established working groups on surface analysis andbio analysis is given. The rapid development by the Joint Committee on Traceability in LaboratoryMedicine - JCTLM is an example of the urgent need for more accurate, comparable and traceablemeasurements in chemistry. Comparability through traceability to the SI, and if not (yet) feasible toother internationally agreed references, is now required in many other fields as well. Cooperationwith the Codex Alimentarius Commission has been established and further cooperation with otherintergovernmental and international organization will soon be broadened. The importance ofmetrology in chemistry has been recognized by the Member States of the Metre Convention and hasled to the decision to establish a small chemical laboratory at the BIPM. The CCQM will continueto work on better understanding and definition of the measurands to be measured and the developmentand validation of primary and other methods of "higher order". The metrological approach chosenby the CCQM to improve the comparability and accuracy of measurements in chemistry has provento be successful.

MAPAN - Journal of Metrology Society of India, Vol. 19, No. 4, 2004; pp. 191-196

Consultative Committees of the InternationalCommittee for Weights and Measures - CIPM,operating under the Inter-Governmental Treatyof the Metre Convention, has grown to be thelargest Consultative Committee. It now has 7CCQM Working Groups, covering all aspects andfields of metrology in chemistry. The scopes ofthese CCQM Working Groups have beendefined as follows :

192

Robert Kaarls

• Gas Analysis, chaired by Dr. E. de Leer,NMi-VSL, The Netherlands;

• Organic Analysis, chaired by Dr. W. May,NIST, USA;

• Inorganic Analysis, chaired by Dr. M.Sargent, LGC, UK;

• Electrochemical Analysis, chaired by Dr. M.Mariassy, SMU, Slovak Republic;

• Bio analysis, chaired by Dr. H. Parkes, LGC,UK and Dr. V.Vilkert, NIST, USA;

• Surface analysis, Dr. M. Seah, NPL, UK; and• Key Comparisons and CMC Quality

(Calibration and Measurement Capabili-ties), chaired by Dr. J. McLaren, NRC-INMS, Canada.

Members of these working groups are theexperts from the National Metrology Institutes(NMIs) and other designated institutes, as wellas from other intergovernmental andinternational organizations having activitiesand interest in reliable chemical measurements.Among these institutes are the IAEA, IRMM,IFCC, WHO, WMO, ISO REMCO, CodexAlimentarius Commission, CITAC and ILAC.

Moreover, named individuals whocontribute with their excellent expertise tothe aims of the CCQM may be invited toattend the meetings of the CCQM. As thefield of metrology in chemistry is extremelywide and most NMIs are not able to coverthe whole field, the Governments of mostcountries in the world have decided tonominate also other expert institutes as adesignated institute having nationalresponsibil ity for certain quantities,measurands and measurement ranges in thechemical area. These designated institutesoperate within their scope of designationas a NMI and participate in the regionalmetrology activities and global activitiesunder the CCQM.

2. The Need for Comparability and Traceability

The only way to realize global comparability

of measurement results is through traceabilityto the long term stable reference standards ofthe International System of Units - SI. As forsome measurements in chemistry, in particularthose of biological activity, traceability to theSI is not (yet) feasible, traceability to otherinternationally agreed references will beestablished, for example to those established bythe WHO.

Although by expressing their measurementresults in SI units (mol, kg, l) analytical chemistsalways have claimed implicitly traceability tothe SI, doubts on the reliability of the resultsremained, as it was not very clear whether anunbroken chain of calibrations or comparisonsto international references existed and what therelated measurement uncertainty was. Tointerpret the value of a measurement result itis essential to know the measurementuncertainty of the result.

Reference to long-term stable measurementstandards is essential for determining smallchanges in global climate or the quality of waterover a long period of time. Comparability ofmeasurement results is essential for takingaway non-tariff barriers to trade, like TechnicalBarriers to Trade (TBT) and consequences ofSanitary and Phyto-Sanitary measures (SPS).

The whole process starting with the (sub-)sampling, sample preparation like dilution,extraction, digestion, etc. and calibrationthrough the final measurement has to be takeninto account for the determination of themeasurement uncertainty.

3. The Consultative Committee forMetrology in Chemistry - CCQM

The main activities of the CCQM WorkingGroups consist of the execution of Pilot Studiesand Key Comparisons. In particular the oldestCCQM Working Groups on Gas, Organic,Inorganic and Electrochemical Analysis havean ongoing broad programme, covering allareas of metrology in chemistry, like health

193


(clinical diagnostic markers and electrolyteelements, steroids and hormones in serum andurine), food, pesticide residues and drinkingwater, environment (water, atmosphericpollutants, contaminants in soils andsediments), primary standard gas mixtures,metal alloys, commodities, alcohol content,forensics and general analytical applications(purity of metals, salts and organics; calibrationsolutions; pH standards and electrolyticconductivity).

New work covers PAHs in solution andin soils and sediments, chlorinatedpesticides in solution, PCB congeners insolution, tissue and tissue extract, volatileorganic compounds in solution, anabolicsteroids in urine, constituents of aluminumalloy, organo-mercury in salmon fish, tracemetals in sewage sludge, trace analysis ofhigh purity nickel, platinum group elementsin automotive catalysts, trace elements insoya bean powder, chemical compositionof clay and metals in fertilizer and H2S innitrogen.

It has now clearly been proven that whenvalidated measurement procedures are rightlyapplied, global comparability of measurementresults can be obtained within generalaccuracies of 1% or (much) better dependingon the measurand to be measured and thematrix environment in which the analyte is.

To assist in the assessment of the reliabilityof Key Comparison results and conclusions,recently some statistical procedures have beendeveloped to test the robustness of the resultsof Key Comparisons.

4. The CCQM and the CIPM MRA

The CIPM Mutual RecognitionArrangement has been created in order toestablish and demonstrate the existence of atransparent international system of reliablenational measurement standards of knownequivalence and to be able to recognize

internationally the calibration andmeasurement results as issued by the NMIs andother designated institutes.

The recognized calibration andmeasurement capabilities and other means ofdelivering traceability to the customers of theNMIs and other designated institutes, inparticular CRMs, are based on the results ofthe Key Comparisons and the implementationof quality systems in conformity with ISO17025 and ISO Guide 34 or equivalent. In asmuch as the field of metrology in chemistry isrelatively new, an on-site peer review of thecapabilities and competences in this fieldclaimed by the NMIs and other designatedinstitutes is highly desirable, because the reportsof these peer review visits are very valuable inmaking final decisions on the acceptability ofthe claimed CMCs of the NMIs and the otherdesignated institutes.

The recently established CCQM WorkingGroup on Key Comparisons and CMC Qualitycombines all the available expertise andknowledge in making final decisions on thereliability of these claimed CMCs and relatedservices like CRMs.

5. Surface Analysis

The CCQM Working Group on SurfaceAnalysis has been established in 2000. Workundertaken since, shows remarkable progresswith respect to measuring, comparingdifferent measurement methods and definingthe best approaches to measure silicon dioxidethickness layers on Si. New projects plannedcover measurements of Fe-Ni and Co-Pt alloythin films, Zn content of Zn/Fe coatings, N andC stoichiometry of metal nitride and carbidehard coatings, C and N amounts in precipitatesin and surface layers of Fe, standard-freequantification in EPMA, B dopant distributionin Si, C amount in different chemical states atpolymer surfaces, OH group density atpolymer surfaces, multilayer thickness andphase stability. In almost all cases different

194

Robert Kaarls

methods will be applied, like AES, XPS, EPMA,RBS, MEIS, SIMS, ICPMS, GDOES, ellipso-metry, etc. depending on the type ofmeasurement.

Important applications of surface analysiscan be found in thin film compositions,coatings, surface layers, contaminations,polymer surfaces, thin film multilayer systems,Si wafers, etc. Therefore the work can becharacterized as surface- and micro-/nano-analysis.

6. Bio-Analysis

The CCQM Working group on Bio Analysishas also been established in 2000.

The area of work covers gene, protein (asfar as not covered by the CCQM WorkingGroup on Organic Analysis) and cellmeasurements.

Priority has been given to the developmentof SI traceable methods for nucleic acids.Projects started and planned concern DNAQuantification (Quantitative PCR calibration),DNA profiling, DNA primary quantificationand DNA extraction.

The purpose of the Quantitative PCRcalibration is to quantify a DNA sequence andto determine factors contributing to QPCRmeasurement variability by providing plasmid-based DNA calibration and testing materials.The comparability of measurement results fromparticipating laboratories using differentplatforms and detection systems is to be tested.First results show consistency of effects withinand between laboratories. However, results arewide spread. We also have observed in thebeginning of metrology in chemistry one of thereasons of wide spread results is the lack ofcarefully following of a validated procedure,which now will be studied. The further studywill also look into the effects of freeze driedsamples, the DNA length and DNA absorptionby tube walls, and of course the different

approaches to the calculation of themeasurement uncertainty have to be studied.

The DNA primary quantification methodis based on the quantification of oligonucleo-tides by phosphodiesterase digestion followedby Isotope Dilution Mass Spectrometry.Potential applications are in the field of in-vitrodiagnostic/clinical measurements.

Other studies are proposed on protein/peptide quantification by Mass Spectrometry,production and characterization of syntheticpeptides as standards for biomolecularinteraction analysis and protein structuralanalysis by Circular Dichroism, used in thebiopharmaceutical industry.

7. The Chemistry Section of the BIPM

The Chemistry Section of the BIPM has beenestablished in 2000.

With the assistance of NIST the BIPM isnow acting, except for the USA, as the worldreference laboratory for ozone measurements.Close cooperation is established with the WMOglobal atmospheric watch programme.

Recent projects undertaken are focusing onthe development of organic pure substances,in particular those needed in the area of clinicalchemistry and not yet available, like forexample aldosterone and theophylline. Alsomethod development and validation will be oneof the aims. The Chemistry section will beequipped with some direct (DSC) as well aswith a number of indirect measurementmethods. The laboratory will work together ina network of other NMIs and designatedinstitutes.

An important activity of the BIPM is tocoordinate and organize global issues ofmetrology and to act as the liaison and globalspokesman of the NMIs and designatedinstitutes with respect to otherintergovernmental and international

195


organizations. In particular in the field ofchemistry many other organizations haveinterest in reliable measurements. So, theChemistry Section spends also a lot of time inliaising with these other organizations.

8. Joint Committee on Traceability inLaboratory Medicine - JCTLM

Developments in the field of clinicalchemistry with the aim to improve thecomparability of the results of clinical,diagnostic measurements have already for sometime been on the agenda of the InternationalFederation of Clinical Chemistry andLaboratory Medicine - IFCC. However, thedecision by the European Commission toimplement the EU In Vitro DiagnosticsDirective by the 1st of January 2004 hascertainly triggered a globally coordinatedaction. This has led to the establishment in 2002of the Joint Committee on Traceability inLaboratory Medicine - JCTLM by the BIPM,IFCC and ILAC. This development has got thesupport of the WHO. In this development allthe interested parties, like the regulators, IVDindustry associations, CRM producers, PTscheme providers, standardization bodies, etc.,are involved.

The JCTLM is chaired by the IFCC, whilethe secretariat is maintained by the BIPM.

Under the JCTLM two working groupshave been established:

• Working Group 1: in charge with ReferenceMaterials and Reference Procedures

• Working Group 2: in charge with ReferenceLaboratory Networks

The JCTLM Working Group 1 is chargedwith establishing a process for identifying,reviewing against agreed criteria, andpublishing a List of "higher order" CertifiedReference Materials and ReferenceMeasurement Procedures required for IVDindustry compliance with the EU IVD Directive.

The review process of "higher order" CRMs hasbeen carried out by eight sub-groups coveringcoagulation factors, drugs (therapeutic and "ofabuse"), electrolytes, enzymes, metabolites andsubstrates, nucleic acids, non-peptide hormonesand proteins. Five new sub-groups will soonbe established, looking to blood gases, bloodgroupings, microbial serology, non-electrolytemetals and vitamins.

The criteria used for reviewing CRMs areformulated in the ISO standards ISO/FDIS15193 and 15194 that describe the essentialrequirements for higher order referencematerials and methods. The important issue ofthe "commutability" of the CRMs underconsideration is still a point needing furtherstudy.

Two lists of CRMs will be established: onewith CRMs of "higher order" traceable to theSI and one with CRMs not (yet) traceable tothe SI and/or no internationally recognizedreference measurement procedure is available(for example WHO reference materials forcoagulation factors, nucleic acids and someproteins) . A first list of SI traceable CRMs hasnow been published and can be accessed onthe website of the BIPM (www.bipm.org) andon the website of the IFCC.

The JCTLM Working Group 2 will soonpublish criteria and processes for assessing theneeded competencies of candidate ReferenceLaboratories, including the establishment ofnetworks for "ring trials" in order to check thecompetence of laboratories to act as a ClinicalReference Laboratory. Criteria for competencehave been formulated in ISO/FDIS 15195.

9. Reference Measurement System for FoodAnalysis

In November 2003 a CCQM Workshop ontraceability in food and feed analysis has beenheld at the BIPM, with input of all stakeholdersconcerned. Presentations have been givenamong others by the Codex Alimentarius

196

Robert Kaarls

Commission on the issues of concern,regulators, NMIs, official food testing referencelaboratories, private food testing laboratories,CRM producers, ILAC, two sector specificschemes on wine and olive oil and the industryon GMO testing. The presentations areavailable on the BIPM website www.bipm.org

The conclusion of the workshop was thatimprovements in the existing situation withrespect to the reliability, comparability andtraceability are necessary. Examples have beenpresented of results of inter-laboratorycomparisons where just taking the mean of theobtained results have led to wrong decisionswith respect to the competence of the testinglaboratories involved. So, there is a clear needfor traceability and traceable reference valuesin PT schemes. Therefore, in September 2004,in close cooperation with the otherstakeholders, a programme of CCQM activitieswill be drafted aiming:

• to identify key measurands in the foodanalysis area;

• to consolidate links between CIPM MRAlaboratories and organizationsimplementing the criteria based approachfor the evaluation of acceptable methodsfor food analysis; and

• to enable PT scheme organizers to provideinput on their requirements for sampleswith traceable reference values.

In order to reach out to the "fieldlaboratories" also the establishment of networksof national and international referencelaboratories will be fostered.

10. Major Reasons for Lack of Comparability

In order to obtain reliable measurementresults it is essential that the wholemeasurement chain starting with the (sub-)sampling through the final measurement iscompletely described and well understood. Inmany cases the uncertainty componentsinvolved in the preparation of the sample are

considerably larger than those caused by themeasurement itself. Reasons for a lack ofcomparability of measurement results are inmany cases found by the fact that themeasurand is not well defined or notunderstood at all in its matrix environment oras caused by changes during the samplepreparation and measurement. Also, as inmany cases the result is also dependent on theprocedure applied, if this procedure is notcompletely and correctly followed deviatingresults have to be expected. In principle itshould be possible to formulate a completemeasurement equation including all theinfluence parameters, but in many cases thismay become a very complicated formula andtherefore is for practical reasons almost notdone.

So, calibration of the whole chain isessential, including all measuring devices usedin the sample preparation, and of course bythe pure elemental solution calibrants used forthe calibration of the final analytic chemicalmeasurement device. Certainly also the certifiedmatrix reference material, used to check thewhole chain, is part of the calibration when arecovery correction is applied.

11. Future Developments

The CCQM will continue its work on keycomparisons and pilot studies as well as on thefurther development and validation of primarymethods and other methods of "higher order"in all areas covered by its working groups. Inas much as purity analysis are crucial for thecalibration it is expected that more focus willbe given on this issue. During the next meetingof the CCQM in April 2004, the CCQM willalso organize again a workshop on the topic ofprimary methods and methods of "higher or-der". Further, the cooperation between theCCQM and the BIPM with other relevant in-tergovernmental and international organiza-tion will of course be continued and broadenedwith sectors like the Pharmacopeia and theWorld Anti-Doping Agency - WADA.

197

Metrological Challenges in Bioanalysis

1. Introduction

The world's principal economic powershave identified biotechnology as a key growthtechnology of the 21st century :

"The importance of biotechnology for wealthcreation and the quality of life is widely ac-knowledged, and measurement plays an indis-pensable role in research, development andregulation for its safe and sustainable innova-



HELEN PARKESLaboratory of the Government Chemist (LGC)

Queens Road, TeddingtonMiddlesex, TW11 0LY, U.K.

e-mail: [email protected]

[Received : 13.08.2004]

Abstract

The importance of biotechnology for wealth creation and the quality of life is widely acknowledged,and measurement plays an indispensable role in research, development and regulation for its safeand sustainable innovation and exploitation. Biomeasurements are complex, with a progression indifficulty and complexity from genes, through proteins to cells and tissues. While there are significantchallenges in meeting the technical requirements for bioanalytical measurement techniques, thereis also a requirement for their parallel validation to ensure accuracy, analytical robustness andfitness for purpose. The development of a biometrology infrastructure is also a priority, withappropriate reference standards to underpin traceability and measurement uncertaintydeterminations moving towards internationally comparable biomeasurements and mutualrecognition. This paper will review some key biomeasurement challenges facing the internationalmetrology community, and the current activity of the CCQM Bio Analysis Working Group aimed ataddressing generic biometrology issues.


tion and exploitation." [1]

Biomeasurements are critical in a numberof areas, which both influence quality of lifeand have economic impact, including: targeteddrug design; genetic diagnostics; biopharma-ceutical safety and efficacy; infectious diseasediagnosis; biowarfare and environmental moni-toring; animal husbandry and forensic profil-ing (Table 1).

The significance of measurement for the

198

Helen Parkes

successful exploitation of biotechnology is sec-tor-dependent. In pharmaceuticals, better mea-surement will reduce time-to-market throughspeeding the identification, development andregulatory clearance of new products. Mea-surement is the focus of competition in the di-agnostics sector, and verification of the perfor-mance of new diagnostic devices would be fa-cilitated by reference samples of key analytes.In the agri-food sector, public perception is aserious barrier to biotechnology innovation andthe key question is the relation between mea-surement and regulation of health, safety andenvironmental impact. The chemicals sectorpresents biomeasurement issues in utilising validin vitro cell based tests for toxicity measure-ments. In characterising pollutants and patho-gens, the environment sector faces measure-ment difficulties like those in diagnostics, withthe additional problem of measurement in verycomplex matrices. In bioprocessing, the needis for better measurements for process controland demonstrating regulatory conformance.

Measurement in the biosciences presents aneven greater challenge for the identificationand application of appropriate metrologysystems than chemical measurements. There is

a steep gradient of difficulty, frommeasurements at the level of the gene, throughthe protein to the cell (Table 2). The scope andcomplexity of biomeasurement summarised inTable 2 is only part of the story. There areadditional challenges of measurement indynamic systems, where metabolic pathwaysare interdependent, where subtle processes ofmolecular recognition and interaction areoccurring and where protein denaturation andpost-translational modification are possible.

In spite of the obvious need, the measure-ment infrastructure for biotechnology is patchyand immature, and there is an absence of ap-propriate reference materials and standards.The establishment of a formal measurementinfrastructure, that facilitates traceabilitythrough the provision of primary methods andstandards, would greatly enhance the confi-dence and international comparability of keybiotechnology measure-ments.

2. International Biometrology Activity

2.1. CCQM Bio Analysis Working Group

The Comité Consultatif pour la Quantitéde Matière (CCQM) is an international com-

Table 1Examples of Bioanalytical applications

Pharmaceutical Development Clinical AnalysisGenomics / proteomics. Prenatal diagnosisDisease understanding / targeted drug Tissue/blood typingdesign / gene therapy Infectious disease diagnosisImproved pharmaceuticals Disease monitoringBioprocess monitoringToxicity testing

Agriculture EnvironmentGM - enhanced nutrient quality/ Water qualitydecreased chemicals Biodiversity monitoringAnimal husbandry Bioremediation

Bioterrorism Law EnforcementMonitoring of biowarfare agents Labelling authentication

Paternity identificationForensic profiling

199


mittee which focuses on developing interna-tional traceability and comparability of chemi-cal measurement. In 2000 the CIPM (ComitéInternational des Poids et Mesures) recognisedthe need to establish a CCQM working groupfor "biometrology" to develop a global infra-structure to underpin biomeasurements. In re-sponse LGC, the designated UK National Mea-surement Institute (NMI) for bioanalysis, andNIST, the US National Institute for Standardsand Technology, were instrumental in settingup the CCQM BioAnalysis Working Group(BAWG). The group aims to develop and main-tain critical enabling infrastructural measure-ments and standards to support internationalbiotechnology industry through developmentof :

i. Validated [primary] biomeasurement meth-ods

ii. High order traceability reference standards

iii. Uncertainty values derived from expert in-ter laboratory studies

The CCQM BAWG has grown rapidly, sinceit was established in 2001, reflecting strong in-ternational support for developing biomeasure-ment comparability and standardisation. Na-

tional Measurement Institutes (NMI's) and ex-pert laboratories from 18 different countries -including US, Japan, China, S.Africa, Austra-lia, Germany, Mexico, Russia now participatein its studies.

2.2. Biometrology Issues

A strategy for fostering internationalbiomeasurement was developed at a novel"thinkshop" (2003), jointly organised by LGC,NIST and the IRMM ( EU Institute for Refer-ence Materials and Methods), which drew to-gether metrologists and bioscientists fromaround the world, including a strong represen-tation from industry.

A number of international regulatory re-quirements were identified as significant indriving biomeasurement requirements. ICHand FDA guidelines impact on the pharmaceu-tical industry in developing and producingbiopharmaceuticals. Codex Alimentarius andISO are developing standards for GM foodanalysis. The EU in vitro diagnostics directive[2] requires higher order traceability in diag-nostics. The EU REACH directive [3], proposesRegistration, Evaluation and Authorisation ofChemicals and demands valid in vitro cell

Table 2Key biomeasurements

Target of Measurement What is Measured

Nucleic Acid Sequence of basesLength of base sequenceAmount [quantification]

Protein Identity, through aminoacid / peptide fragment sequenceAmount [quantification]Size - peptide fragment size, massFunction - receptor, signal transduction, bindingActivity - enzyme catalysis, antibody affinityStructure - primary through quaternary

Cell / Tissue Identity - cell typing, profiling, growth characteristicsQuantity - cell countingSize - cell sortingViability - growth / responseCellular functionality - gene expression, metabolismInteractions - adhesion, recognition, toxicity

200

Helen Parkes

based assays as alternatives for chemical toxic-ity testing. Significant international consensusis also required by the International OlympicCommittee in drugs of abuse test requirements- increasingly these are aimed at the detectionof complex biologicals such as erythropoietin(EPO) and peptide hormones (e.g. humanchorionic gonadotropin and human growthhormone). Furthermore, there is a need foranalytical laboratories to develop an under-standing of measurement uncertainty in a bio-logical context [4] to comply with the accredi-tation requirements of ISO17025.

A number of common biomeasurement is-sues were raised in the specific context of gene,protein and cell analyses including:

• Specific identification of the relevantmeasurand(s)

• No universally accepted terms/definitionsor measurement unit harmonisation

• Unknown and highly variable influence ofextraction and in matrix measurements

• The relative contribution of the method tomeasurement uncertainty

• Measurements were likely to be complex,multiparametric and usually relative notabsolute

• Difficulty of measurement comparabilityacross different technology platforms

All of these considerations impact signifi-cantly on how to define "fit for purpose" trace-ability and determine measurement uncer-tainty. Particular attention was given to trace-ability and uncertainty issues with the differ-ences between SI traceable standards and in-ternational Biological standards (WHO) beinghighlighted. All participants recognised andaccepted the requirement to have internation-ally accepted traceability in biomeasurement -but there was considerable debate over the wayin which this could best be realised. A signifi-cant question for the international biometrologycommunity to address is what level of SI, or

other, traceability is realistic and of value ?

On the basis of the thinkshop discussionsthe CCQM BAWG strategy for prioritisationof effort in its work programme was deter-mined:

• Design pilot studies in [regulatory] criticalanalytical areas

• Build up "step by step" picture of "uncer-tainty" (with direct measurements wherepossible/realistic)

• Generate uncertainty value for whole pro-cess (derive biological equation)

• Enable key comparisons for key measure-ments

• Initiate discussion on "unit" harmonisation

• Identify realistic routes to traceability (i.e.measurand units with assigned uncertaintyvalue)

2.3. Current Programme of BAWG Activity

In line with the determined strategy, theBAWG selected DNA quantification as its firstarea of work. The aim was to improve the com-parability of these measurements across theworld by determining factors and practices thatcontribute to accurate quantification and mea-surement uncertainty. Accurate quantitativenucleic acid measurements are particularlyimportant, for example, in underpinning legis-lation (detection of GM ingredients in foods)and in disease management (monitoring patho-genic load with respect to disease progressionor efficacy of treatment). Nucleic acid amplifi-cation and quantitative real time PCR (QPCR)in particular, are key technologies for thesebiomeasurements. However, there are manyvariables which contribute to the reliability androbustness, and hence measurement accuracyand precision, of these techniques. Sector spe-cific groups such as the Codex Alimentarius,have already started to tackle the issue to someextent, in developing normative "standards" forapplication of QPCR to GM food analysis. More

201


Fig. 1. Method performance of each participating group(group means and 95% confidence levels are displayed on the graph)

0

50

100

150

200

250

300

350

400

450

1 2 3a 3b 4 5a 5b 5c 5d 6a 6b 7a 7b 8 9 10 11 12 13 14 15 16c 17a

Group

Est

imat

ed c

once

ntra

tion

(pg/

ul)

generic, cross-sectoral biometrology issues withrespect to QPCR are now being addressed bythe BAWG.

2.4. QPCR Pilot Study

The first stage of an international pilotstudy, on quantitative PCR (QPCR), was un-dertaken by the CCQM Bio Analysis workinggroup in 2003 and was devised and led jointlyby LGC (UK) and NIST (US). The study aimedto determine the factors which contribute tointerlaboratory variability in quantification ofa DNA sequence (eg. GM insert, viral nucleicacid) using QPCR. Participants were providedwith plasmid-based DNA calibration and "un-known" materials and were required to createa calibration curve and determine the quantityof each of the unknowns.

There was enthusiastic participation byNMI's and nominated expert laboratories (17groups with a global spread). Three of the ma-jor QPCR platforms were used in combination

with several different chemistries includingTaqman®. A comprehensive statistical analy-sis of the study results was undertaken to de-termine the major influences on QPCR com-parability and to determine the associated mea-surement uncertainty. The data was analysedusing z-scores based on both a consensus andexpert lab approach according to ISO guide-lines. The repeatability of the assay within labo-ratories was, in general, very good, howeverthe reproducibility of the assay between labo-ratories was poor (Fig. 1).

Consistent trends regarding some commonfactors accounting for some of the variationbetween laboratories were evident. Samplehomogeneity, stability, dilution and storagewere considered to be factors contributing sig-nificantly to the variability, and this is beinginvestigated further. However, in order to de-termine more clearly the statistical contributionof other experimental variables e.g. technologyplatform and chemistry, more information was

202

Helen Parkes

required. The next stage of the study is nowbuilding on the previous results by incorporat-ing more rigid experimental design, a moreprescriptive protocol and a structured question-naire, to enable the more effective identifica-tion of factors contributing towards uncertaintyin the assay. This study will provide a valuablecontribution to the international debate on thevalidity of QPCR measurements [5].

Studies in a number of other significant ar-eas are commencing including: DNA profiling;an Isotope Dilution Mass Spectrometry pri-mary method for DNA quantification [6]; pro-tein/peptide quantification by mass spectrom-etry; fluorescence in ELISA, developing a DNAextraction method reference method and vali-dation of Circular Dichroism spectroscopy forprotein structural analysis

3. Conclusion

The rapid growth and increasing level ofactivity of the CCQM Bio Analysis workinggroup reflects both very significant interest bythe international metrology community andthe importance of developing a biometrologyinfrastructure. The CCQM BAWG faces a num-ber of challenges in developing its ongoing workprogramme, particularly as biomeasurement isa broad and complex area with rapidly evolv-ing regulatory challenges. Prioritisation of ef-fort and collaboration with other internationalorganisations, such as WHO and OECD, iscritical to ensure BAWG standardisation activityremains relevant to the requirements of the rap-idly evolving biotechnology industry. The aimis to work towards internationally comparablebiomeasurements, with the principle "mea-sured once accepted everywhere" as applicable

to bioanalysis as to the more quantitative disci-plines of physics and chemistry.

References

[1] Biotechnology for the 21st Century : NewHorizons, A Report from the Biotechnol-ogy Research Subcommittee on Funda-mental Science, National Science andTechnology Council, U.K., 1995.

[2] Directive 98/79/EC of the European Par-liament and of the Council of 27 October1998 on “In Vitro Diagnostic Medical De-vices,” Official Journal of the EuropeanCommunities, L331 (1998) 1-37.

[3] White Paper Strategy for a Future Chemi-cals Policy, COM (2001) 88 final, Brussels,27.2.2001.

[4] M. Burns, Current Practice for the Assess-ment and Control of Measurement Uncer-tainty in Bio-analytical Chemistry, Trendsin Analytical Chemistry, 23 (2004) 393-398.

[5] M. Burns, J. Blasic, F. Qureshi, A. Woolfordand M. Holden, Determination of Factorsand Practices that Contribute towards Sig-nificant Measurement Uncertainty in Real-time Quantitative PCR (2004) Paper inpreparation.

[6] G. O'Connor, C. Dawson, A. Woolfordand T. Catterick, Quantitation of Oligo-nucleotides by Phosphodiesterase Diges-tion followed by Isotope Dilution MassSpectrometry (DMS) : Proof of ConceptAnalytical, Chemistry, 74 (2002) 3670-3676.

203

Update on COMAR - the Internet Database for Certified Reference Materials

1. Introduction

The usefulness of certified referencematerials (CRMs) is beyond question. Chemicalanalysis and materials testing are becomingever more important as science, trade andsociety are getting more complex andworldwide. The number and significance ofdecisions based on the results of chemicalanalysis and materials testing is ever increasingin all spheres of life including science,economy, trade, health care, environmentaland consumer protection, sports andjurisdiction. For this purpose results of analysisand testing have to be reliable and comparableas well as acceptable worldwide. The use ofcertified reference materials is an efficient andproper tool to achieve these goals. CRMs playan important role in establishing traceabilityin chemical analysis. The use of CRMs is a basicand mandatory requirement in internationallyaccepted quality systems (ISO 9000, ISO/IEC17025).

2. CRM Database

Potential users of CRMs are quickly


Update on COMAR - the Internet Database for CertifiedReference Materials

THOMAS STEIGER and RITA PRADELCOMAR Central Secretariat

Federal Institute for Materials Research and Testing (BAM)12200 Berlin, Germany

e-mail: [email protected]

[Received : 21.09.2004]


confronted with the problem how to find theproper CRM they need. The internationaldatabase for certified reference materialsCOMAR has been developed to assist analyticaland testing laboratories, scientific andtechnological institutes, industrial enterprisesand technical authorities to address this everincreasing demand.

Even nowadays in the web age, there is stillneed for a worldwide CRM database. Ofcourse, a good deal of information is availablefrom the internet pages of the variousproducers, but this information is not providedin a consistent and uniform manner. Thereforedirect search of producers' web pages orcatalogues may waste a lot of time.

Recently COMAR has substantially beenimproved and redeveloped into an internet-based version. This work was accomplished bythe COMAR central secretariat at BAM in co-operation with a professional software house.The web-based version of COMAR takesaccount for the modern trends in informationtechnology and the need for faster, user-friendlyand more up-to-date dissemination ofinformation on available CRMs from the

204

Thomas Steiger and Rita Pradel

world's major producers. The internet versionof COMAR is running since March 2003.

COMAR is freely accessible via the COMARhomepage : http://www.comar.bam.de.

3. Advantages of COMAR

The advantages of the new COMARversion as well as a detailed description of thesearch tools and of the information providedhas been published recently [1, 2]. CRMinformation is much more current becauseCOMAR provides, and even implies, thepossibility of regular and direct updates viainternet. COMAR enables to add referencematerials certificates and certification reports,or to set links to the corresponding web pagesof the producers. A comprehensive user guidecan be downloaded from the COMARhomepage.

4. Coding Centres

COMAR is maintained by appointed (so-called) coding centres, which co-operate on avoluntary basis. These coding centres are wellexperienced and renowned national orinternational CRM institutes. They areresponsible for the selection, input and updateof appropriate CRMs of producers in theirassigned countries. CRMs selected for COMARshould comply with the ISO Guides 30 - 35.Presently COMAR is supported by thefollowing 15 coding centres:

• BAM - Federal Institute for MaterialResearch and Testing, Germany,

• CANMET - Mining and Mineral SciencesLaboratory, Canada,

• CENAM - Centro Nacional de Metrologia,Mexico,

• CMI - Czech Metrology Institute, CzechRepublic,

• GUM - Central Office of Measure, Poland,

• IRMM - Institute of Reference Materials andMeasurement, JRC, European Commission,

• LNE - Laboratoire National d'Essais, France,

• LGC - VAM Helpdesk, United Kingdom,

• NIST - National Institute of Standards andTechnology, United States,

• NITE - National Institute of Technology andEvaluation, Japan,

• NMIA - National Measurement Institute ofAustralia, Australia,

• NRCCRM - Chinese National ResearchCentre for Certified Reference Materials,China,

• SMU - Slovak Institute of Metrology,Slovakia,

• SP - Swedish National Testing andResearch Institute, Sweden and

• UNIIM - Ural Research Institute forMetrology, Russian Federation.

5. Web-based COMAR Version

Starting in March 2003, the web-basedCOMAR version made available the completestock of data of its precursory floppy disc versionof 1999 and some data amendment andupgrading, that was made during the testperiod of the new version. Since March 2003,COMAR update has been performed by theresponsible coding centres according to theirresources. The update process is still in progress.Presently COMAR contains information onsome 11 000 CRMs of 256 producers in 25countries. Table 1 gives an overview byproducer countries.

The summary numbers do not represent thereal changes and update of data. Since March2003 several thousand CRM entries have beenmodified, about 500 cancelled and somethousand new entries added. Nevertheless thefull update of the complete CRM data is a hugechallenge and will take some time.

The internet version of COMAR is wellaccepted by the reference materials community.The demand for CRM information provided by

205


Table 1Number of CRMs and producers contained in COMAR

Country or Number of Number of Number ofinternational CRMs CRMs producersorganisation 15 April 2003 15 Sept 2004 15 Sept 2004

United Kingdom 2407 2265 13

France 1188 1113 17

USA 1027 1048 2

China 1008 1034 81

Germany 916 976 9

Japan 870 895 13

IRMM 671 760 1

Russian Federation 623 627 16

Canada 377 351 9

Czech Republic 0 326 7

Switzerland 253 253 1

Slovakia 233 229 7

Brazil 61 105 1

Australia 4 88 2

IAEA 93 80 1

WHO 206 206 1

Others (12 countries) 589 661 75

Total 10526 11017 256

Fig. 1. Development of registered COMAR users

0

500

1000

1500

2000

Mar2003

May2003

Jul2003

Sep2003

Nov2003

Jan2004

Mar2004

May2004

Jul2004

Sep2004

registered COMAR users

206


Fig. 2. Use of COMAR database

COMAR is demonstrated by Fig. 1 and 2. Fig.1shows the development of the registeredCOMAR users. Presently there are more than1 900 registered users from more than 50countries.

Fig. 2 demonstrates the utilisation ofCOMAR in terms of user logins and the numberof displayed search results (i.e. number ofdisplayed internet pages with detailed CRMinformation for selected search hits). On anaverage, there are about 350 user logins andabout 1 200 displayed search results monthly.

COMAR covers a very broad scope of CRMapplications ranging from analytical chemistryvia physical measurements and testing toindustrial technologies. For historical reasons,metallic CRMs still dominate in COMAR. Theincreasing importance of biological andenvironmental CRMs is also reflected inCOMAR. Related CRMs are mainly assignedto the COMAR fields of application "Biologyand Clinical Chemistry" and "Quality of Life".Presently they cover only about 16% of allCRMs in COMAR, but not surprisingly, inrecent years these CRM categories have been

Table 2COMAR main fields of application and percentage distribution of CRMs

Ferrous reference materials 13%

Non ferrous metallic reference materials 24%

Inorganic reference materials 11%

Organic reference materials 5%

Reference materials of physical properties 14%

Reference materials for biology and clinical chemistry 3%

Quality of life reference materials 13%

Industrial reference materials 18%

0500

100015002000

25003000350040004500

March-Jun

2003

July-Sept2003

Oct-Dec

2003

Jan-March2004

April-June2004

July-Sept2004

COMAR logins

viewed search results

207


the fastest growing. Table 2 shows the 8 mainfields of application as used in COMAR forCRM classification (each main field containsup to 10 sub-fields), and the percentagedistribution of CRMs.

6. Concluding Remarks

Despite the information provided viainternet by the various producers and theavailability of reference materials databases ofregional orientation (e.g. the European VIRM[3] or the Japanese RMinfo system [4]) or forspecial kinds of materials (e.g. IAEA NaturalMatrix Reference Material Database [5]),COMAR is the only database enabling aproducer-independent worldwide search forCRMs. The demand for information aboutavailable CRM is still growing.

In summary, COMAR has been a key sourceof information about CRMs, covering a broadscope of application fields. COMAR is well pre-pared to meet this challenge also in the future.

References

[1] R. Pradel, T. Steiger and H. Klich,Availability of Reference Materials :COMAR the Database for CertifiedReference Materials, Accred. Qual Assur,8 (2003) 317-318.

[2] T. Steiger and R. Pradel, COMAR - TheInternet Database for Certified ReferenceMaterials, Anal Bioanal Chem, 378 (2004)1145-1146.

[3] European 'Virtual Institute for ReferenceMaterials' (VIRM), http://www.virm.net

[4] Reference Materials Total InformationService of Japan (RMinfo), http://w w w . r m i n f o . n i t e . g o . j p / e n g l i s h /index.htm

[5] IAEA Natural Matrix Reference MaterialDatabase, http://www-naweb.iaea.org/nahu/external/e4/nmrm

208


209

Present Status of Certified Reference Materials in India

1. Introduction

Certified reference materials (CRMs) are© Metrology Society of India, All rights reserved.


A.K. AGRAWALNational Physical Laboratory

Dr. K.S. Krishnan MargNew Delhi - 110 012, India

e-mail : [email protected]

[Received : 05.08.2004]

Abstract

In the present scenario of globalization of economy, use of Certified Reference Materials (CRMs) inmeasurements is essential for global acceptance of products and test reports. Use of certified referencematerials also ensures high quality in measurements and provides traceability to the analyticalmeasurements with national /international measurement system (SI unit). Their use fulfills a mandatoryrequirement of international level quality systems (ISO 9000, ISO/IEC standard 17025) includingIndia’s national accreditation body, National Accreditation Board for Testing and CalibrationLaboratories (NABL) and of World Trade Organization (WTO). Large number of certified referencematerials/ reference materials including biological and environmental CRMs are being required/used in India for quality control in industries, accredited testing laboratories, monitoring andcontrol of various environmental and health parameters. In India, National Accreditation Boardfor Testing and Calibration Laboratories (NABL) has granted accreditation to nearly 500 testinglaboratories including the areas of biological, chemical and clinical testing. Their activitiesenhanced the demand of the CRMs in the country tremendously. At present, the internationalmanufacturers of CRMs are meeting the requirement of CRMs of the country. Import of CRMs is acostly affair and taking longer time in supply. To eliminate the problems of import and meeting thedemand of CRMs indigenously at a reasonable cost, National Physical Laboratory, India (NPLI)initiated a national programme on preparation and dissemination of certified reference materials.Nearly 30 Indian laboratories are participating in this collaborative programme. NPLI initiatedthe programme by the preparation and dissemination of CRMs of mono and multi-elemental solutionsof various elements. Later it created satellite groups for preparation of CRMs in the areas of gasmixture, X-ray diffraction, pesticides, petroleum, metal & alloys, food, building materials and oresto enhance the scope of the programme. 21 CRMs of various categories including water, pesticides,gas mixture, X-ray diffraction have been prepared so far.


required for quality control of measurementdata being generated in any laboratory forglobal acceptance. Their use in calibration ofanalytical equipment and validation of test

210

A.K. Agrawal

methods enhances the quality of measurementsand provides traceability to the national andinternational measurement systems. It ismandatory requirement of all the national/international accreditation bodies and WorldTrade Organization (WTO) for globalacceptance of test/calibration reports andproducts [1]. Following definitions of referencematerials and certified reference materials asgiven by International Standards Organizationare universally accepted [2].

1.1. Reference Materials (RM)

A material or substance one or more ofwhose property values are sufficientlyhomogenous and well established to be usedfor calibration of an apparatus, the assessmentof measurement method, or for assigningvalues to the materials.

1.2. Certified Reference Material (CRM)

A reference material, accompanied by acertificate, one or more of whose property

values are certified by a procedure whichestablished its traceability to accuraterealization of the unit in which the propertyvalues are expressed, and for which eachcertified value is accompanied by anuncertainty at a standard level of confidence.

2. Indian Programme on Preparation andDissemination of the CRMs

A large number of CRMs are required inthe country for quality management in all thesectors of science and technology includingaccredited laboratories in accordance to ISOand WTO requirements. In India, NationalPhysical Laboratory is coordinating a nationalprogramme on preparation and disseminationof certified reference materials (CRMs) to meetthe requirement of CRMs in the countryindigenously. It created a network of thirty topranking laboratories of the country includingseventeen CSIR laboratories. Network of thelaboratories participating in the programme isshown in Fig. 1. Names and addresses of

Fig. 1. Network of the laboratories

211


Table 1Laboratories participating in programme on preparation and dissemination of CRMs

S. No. Participating laboratories

1 National Physical Laboratory, New Delhi - Nodal Laboratory2 AES Testing & Research laboratory, Noida.3 Bhabha Atomic Research Centre, Mumbai.4 Central Building Research Institute, Roorkee.5 Central Food Technological Research Institute, Mysore.6 Central Fuel Research Institute, Dhanbad.7 Central Glass & Ceramic Research Institute, Kolkata.8 Central Rice Research Institute, Cuttack.9 Central Salt & Marine Chemicals Research Institute, Bhavnagar.10 Gharda Chemicals Ltd., Dombivli.11 Indian Agricultural Research Institute, New Delhi.12 Indian Institute of Chemical Technology, Hyderabad.13 Indian Institute of Petroleum, Dehradun.14 Indian Oil Corporation, Faridabad.15 Industrial Toxicology Research Centre, Lucknow.16 National Aeronautical Laboratory, Bangalore.17 National Botanical Research Institute, Lucknow.18 National Center for Compositional Characterization of Materials, Hyderabad.19. National Chemical Laboratory, Pune.20 National Environmental Engineering Research Institute, Nagpur.21 National Geophysical Research Institute, Hyderabad.22 National Institute of Oceanography, Goa.23 National Metallurgical Laboratory, Jamshedpur.24 National Remote Sensing Agency (NRSA), Hyderabad.25 National Thermal Power Corporation, Noida.26 Physical Research Laboratory, Ahemdabad.27 Regional Research Laboratory, Bhubaneswar.28 Regional Research Laboratory, Jorhat.29 Regional Research Laboratory, Thiruvananthapuram.30 Tata Energy Research Institute, New Delhi

participating laboratories are given in Table 1.

3. CRMs of Social Importance

In the first phase of the programme, NPLinitiated the work on preparation of CRMs oftoxic elements in water due to its societalimportance [3-8]. Large amount of water isrequired for day to day activities like humanconsumption, agriculture, industries, etc.Surface and underground water is beingcontaminated with various toxic elements bythe untreated discharge of industrial effluentand sewage water. Excessive use of pesticides

and fertilizers also contaminates theunderground water. Sometimes withdrawal ofunderground water in large quantity causesthe lowering of water level resulting intoexcessive contamination of toxic elements. It isa worldwide problem. For example, in someparts of West Bengal in India and coastal areasof Bangladesh arsenic contents has increasedto an alarming level in the underground water[9]. Recently, it is reported that in some partsof the Indian states namely Rajasthan, Orissaand Delhi problem of excessive fluoride andiron in groundwater has emerged. A large

212

A.K. Agrawal

section of rural population is depending onwells, hand pumps, tube wells, rivers andponds for drinking water. Most of these sourcesof water are found unfit for humanconsumption due to contamination of heavymetals and other constituents like residualpesticides and biological species. It causesserious health problems on short term andlong-term basis. In view of it, it is required thatwater supply agencies should monitor thequality of water more professionally andregularly to ensure its quality. A small error inmeasurement can vitiate the correctivemeasures. Therefore, in decision-making,whether water from a particular source is fitfor human consumption or not, the role ofaccurate measurements becomes very vital. Thepermissible limits of most of the impurities arevery low and these can be measured byspecialized techniques, which requirecalibration in lower range of the lower

concentration. For example, the safe limit ofarsenic in drinking water is 10 ppb as perIndian Standard Specification [10] and 50 ppbas per guidelines of World Health Organization[11]. Most of the CRM producers are marketingthe CRMs of elemental solution in higher rangeof concentration i.e. 1000 to 10000 mg/l.Analysts have to dilute them many folds forcalibration of the equipment for use at tracelevel testing and it causes error inmeasurements. To eliminate the chances oferror due to dilution of the CRMs ofconcentrated elemental solution, NPL hasprepared the CRMs of elemental solutions inthe lower concentration range in accordanceto the requirement of the measurement ofelements in water [12-15]. NPL is also supplyingdiluting mediums to minimize the error indilution. Details of the CRMs of the elementalsolutions prepared and certified under thisprogramme so far are given in Table 2.

Table 2Details of the CRMs of elemental solutions prepared at NPL

S. No. CRM Code Elemental Solution Certified Values

1. BND 101.03 Lead 1.00 ± 0.02 mg/L

2. BND 102.03 Lead 2.00 ± 0.02 mg/L

3. BND 201.03 Cadmium 1.00 ± 0.02 mg/L

4. BND 301.02 Arsenic 1.00 ± 0.02 mg/L

5. BND 401.02 Chromium 1.00 ± 0.02 mg/L

6. BND 402.02 Chromium 2.00 ± 0.02 mg/L

7. BND 601.02 Mercury 1.00 ± 0.02 mg/L

8. BND 701.02 Selenium 1.00 ± 0.02 mg/L

9. BND 801.02 Fluoride 1.00 ± 0.02 mg/L

10. BND 1001.02 Nickel 1.00 ± 0.02 mg/L

11. BND 1201 Zinc 1.00 ± 0.02 mg/L

12. BND 1301 Iron 1.00 ± 0.02 mg/L

13. BND 1401 Copper 1.00 ± 0.02 mg/L

14. BND 901 Nitrate 49.94 ± 0.48 mg/L

15. BND 1801 Calcium 50.24 ± 0.42 mg/L

16. BND 1901 Manganese 1.00 ± 0.02 mg/L

17. BND 1101.02 Consisting of copper, 99.69 ± 0.94, 100.12±0.78 &iron and zinc 99.95 ± 0.84 mg/L

213


4. Expansion of the Programme

After acquisition of experience onpreparation of CRMs of elemental solutionsand creation of required infrastructure, thescope of the work has been expanded in otherareas of measurement namely gas mixture, X-ray diffraction, SEM-TEM resolution,petroleum, pesticides, food, alloys and ores.Complete programme of preparation anddissemination of CRMs in India is shown inFig. 2.

Certified Reference Materials

Pesticides

Gas Mixture

X-ray Diffraction

Mono Elemental Solutions Multi

Elemental Solutions

Ores

Petroleum

Alloys

Food

SEM-TEM resolution

Fig. 2. Areas of the certified reference materials covered under CRM programme

Required infrastructure and experts for allthe areas are not available at NPL, hence itcreated satellite groups for these activitiesunder leadership of the expert laboratory. Theselaboratories have been nominated as leadlaboratories to prepare the CRMs in the areasof their specialization on the basis of their longexperience in that area. The details are givenin Table 3.

Table 3Lead laboratories identified for preparation of CRMs in different areas

S. No. Area of CRM Name of the Lead Laboratory

1 Mono elemental solutions National Physical Laboratory2 Multi elemental solutions National Physical Laboratory3 Silicon powder for X-ray diffraction National Physical Laboratory4 Gas Mixture National Physical Laboratory5 SEM/TEM resolution National Physical Laboratory6 Pesticides Indian Institute of Chemical Technology7 Petroleum Indian Institute of Petroleum8 Food Central Food Technology Research Institute9 Alloys National Metallurgical Laboratory10 Ores National Geophysical Research Institute

214

A.K. Agrawal

NPL is closely monitoring the metrologicalaspects of the CRMs developed by theselaboratories and certifying the value of theproperty. These lead laboratories have alreadyinitiated the preparation of CRMs in theirrespective areas. Following CRMs have beenprepared in the expanded areas so far :

4.1. X-ray Diffraction

CRM of high purity polycrystalline siliconpowder (BND 1501) has been prepared at NPLwith the particle size in the range of 5 - 15 mm.Following are the certified values of its d-spacing of first five reflections :

Table 4CRMs under preparation

S. No. CRM Lead laboratory preparing the CRM

Elemental Solutions1 Magnesium National Physical Laboratory, New Delhi2 Cobalt National Physical Laboratory, New Delhi3 Strontium National Physical Laboratory, New Delhi

Pesticides4 Fenvelarate Indian Institute of Chemical Technology, Hyderabad5 Cypermethrin Indian Institute of Chemical Technology, Hyderabad

Ores6. Gold Ore National Geophysical Research Institute, Hyderabad

Petroleum7. Trace Elements in Fuel and Lubricating Oil Indian Institute of Petroleum, Dehradun

Food8. Trace Elements in Skimmed Milk Powder Central Food Technology Research Institute, Mysore

Alloys9. Plain Steel (Low Carbon Steel) National Metallurgical Laboratory, Jamshedpur

hkl d(Ao) sd

111 3.1340 0.0073220 1.9194 0.0029311 1.6371 0.0022400 1.3576 0.0014331 1.2459 0.0011

4.3. Pesticides

CRMs of chlorpyriphos and isoproturonpesticides have been prepared and purified atIndian Institute of Chemical Technology(IICT),Hyderabad. The certified concentration ofchlropyriphos (BND 1701) and isoproturon(BND 2001) is 99.15 ± 0.90% and 98.79 ± 1.42%respectively.

5. Future Programme

Various CRMs are under preparation inthis network programme and likely to bereleased in future. The details are given inTable 4.

6. Traceability

NPL is continuously participating ininternational comparison programmes todemonstrate its measurement capability and toprovide the traceability and acceptability ofCRMs developed under this programme. Theseinter-comparison programmes are beingorganized by various internationalorganizations namely National Institute ofStandards and Technology (NIST), NationalAssociation of Testing Authorities (NATA),

4.2. Gas Mixture

CRM of methane in nitrogen (BND 1601)has been prepared at NPL. The certifiedconcentration of methane is 9.65 ± 0.66 ppmv.

215


Institute of Reference Materials andMeasurement (IRMM), etc. on behalf ofConsultative Committee for Amount ofSubstance (CCQM), Asian Pacific MetrologyProgramme (APMP), European MetrologyProgramme (EUORMET), or independently.Findings of these comparisons are available ontheir websites. Following are the results of someof the inter-comparisons:

6.1. Consultative Committee for Amount ofSubstance (CCQM)

Key Comparison CCQM K-8 has beenorganized jointly by EMPA, Switzerland andBNN-LNE, France, USA for CCQM. Fourmono-elemental solutions of aluminium,copper, iron and manganese have beenreceived for determination of theirconcentration. Values reported by NPL and keycomparison reference values (KCRV) are givenin Table 5.

6.2. Joint Research Centre of European Union

Institute for Reference Materials andMeasurement (IRMM), Belgium has organizeda comparison programme IMEP 12 for JointResearch Centre of European Commission. Amulti-elemental solution consisting boron,cadmium, chromium, copper, iron, magnesium,manganese and nickel have been received fordetermination of their concentration.Comparative values are given in Table 6 [17].

6.3. National Association of TestingAuthorities (NATA)

NATA, Australia is regularly organizingproficiency testing programmes in chemicaltesting on a large scale. NPL has participatedin its four programmes on water testing forvarious physical and chemical characteristics.In one of the programmes named as WatersSub-program 26 four multi-elemental solutions

Table 5Results of CCQM K-8 key comparison

Sample Element NPL Values Key Comparison Reference ValuesNo. (g/kg) (g/kg)

1. Aluminium 0.9875 ± 0.0059 0.99685 ± 0.00042. Copper 0.9739 ± 0.00519 0.98819 ± 0.000033. Iron 1.0455 ± 0.0054 1.01966 ± 0.00014. Magnesium 1.1896 ± 0.0072 1.00428 ± 0.0009

Note : These results are available on BIPM website under Appendix B [16]

Table 6Results of IMEP - 12 key comparison

S. No. Elements NPL Values Key Comparison Reference Values(mol.mL-1) (mol.mL-1)

1. Boron 11.5x10-9 ± 0.334x10-9 12.11x10-9 ± 0.24x10-9

2. Cadmium 41.8x10-12 ± 10.7x10-12 40.78x10-12 ± 0.82x10-12

3. Chromium 1.08x10-9 ± 0.0456x10-9 1.010x10-9 ± 0.029x10-9

4. Copper 3.13x10-9 ± 0.0918x10-9 3.142x10-9 ± 0.068x10-9

5. Iron 3.77x10-9 ± 0.114x10-9 3.805x10-9 ± 0.091x10-9

6. Magnesium 1.82x10-6 ± 0.212x10-6 1.590x10-6 ± 0.032x10-6

7. Manganese 1.27x10-9 ± 0.0388x10-9 1.30x10-9 ± 0.13x10-9

8. Nickel 0.46x10-9 ± 0.3951x10-9 0.3951x10-9 ± 0.0079x10-9

216

A.K

. Agraw

al

Fig. 3. NATA's comparisons results for waters sub-programme 26 (PTAC No. 204)

Iron (mg/L) - Samples NO81 & No 82

Laboratory Code Number

217


i.e sample Nos. 81-84 containing aluminium,cadmium, chromium, cobalt, copper, iron, lead,nickel and zinc has been received formeasurement of concentration. These elementsare in the concentration range of ppb-ppm. 151laboratories from 11 countries had participatedin this programme. The results of thisprogramme had been compiled as a report No.PTAC 204, Waters Sub-Programme 26 Metals[18]. NPL India code number is 524. It wasobserved that the results reported by NPL areclose to the median values. For example, themedian value of the iron in sample numbers81 and 82 has been found to be 0.027 mg/L,while reported value of NPL is 0.28 mg/L forboth the solutions. Comparison with otherlaboratories is shown in Fig. 3.


Use of certified reference materials incalibration of equipment and for validation oftest methods is essential to generate precise andaccurate measurements. Their use ensurestraceability of measurement to national andinternational measurement systems, whichenhances the global acceptability of test/calibration reports, industrial and agricultureproducts.

References

[1] ISO/IEC 17025 - 1999, GeneralRequirements for the Competence ofTesting and Calibration Laboratories,International Standards Organization(ISO), Geneva.

[2] ISO Guide 30 (1992), Terms and Defnitionsused in Connection with ReferenceMaterials, International StandardsOrganization (ISO), Geneva.

[3] A.K. Agrawal, R.K. Saxena, AbhaBhatnagar, Sunita Ganju and Krishan Lal,Assessment of Quality of Water inEnvironmental Pollution, Eds. V.P. Singhand R.N. Yadava, ISBN 81-7764-550-1,Allied Publishers, New Delhi (2003) 3-9.

[4] P.K. Gupta, A.K. Agrawal and KrishanLal, An Improved Apparatus Useful forUltra-purification of Liquids by Sub-boilDistillation and a Process Therefore,Indian Patent No. 187019, 2002.

[5] A.K. Agrawal and Krishan Lal,Preparation and Dissemination ofCertified Reference Materials: IndianExperience in Advances in Metrology andGlobal Trade, Eds. A.K. Agrawal, A.K.Saxena, A. Sen Gupta. P.C. Jain and P.C.Kothari, MAPAN-Journal of MetrologySociety of India, Supplementary Issue 1(2001) 393-400.

[6] V. Balaram, K. Chandrasekhar, A.K.Agrawal et al, Analysis of Sub-boilDistilled Water, Hydrochloric and NitricAcids by ICP-MS, Ind. J. Chem., 39A(2000) 567-570.

[7] P.K. Gupta, Chetna Kaw, Sunita Ganju,A.K. Agrawal, R. Ramchandran, A.K.Sarkar and Krishan Lal, Preparation ofCertified Reference Materials of Traces ofChromium and Arsenic in Water and MilkPowder, Fresenius J Anal Chem., 345(1993) 278-281.

[8] P.K. Gupta, A.K. Agrawal, R.Ramchandran., A.K. Sarkar and KrishanLal, Preparation of Ultra-pure Water andCertified Aqueous Solution of Lead asReference Materials, Proceedings ISCRM89, China, Pergamon Press, New York(1989) 82-89.

[9] Krishan Lal and A.K. Agrawal, Report onOne Year Village Level Trial of Filter Tabletfor Arsenic Removal from Ground Water,National Physical laboratory, New Delhi,2002.

[10] IS: 10500 - 1991, Drinking WaterSpecification, Bureau of Indian Standards(BIS), New Delhi.

[11] Guidelines for Drinking Water Quality,Vol. 2, World Health Organization

218

A.K. Agrawal

(WHO), Geneva, 1996.

[12] ISO Guide 35 (1989), Certification ofReference Materials - General andStatistical Principles, InternationalStandards Organization (ISO), Geneva.

[13] Guidelines for Estimation and Statementof Overall Uncertainty in MeasurementResults, National Accreditation Board forTesting and Calibration Laboratories,India, 1996.

[14] EURACHEM/CITAC Guide onQuantifying Uncertainty in Analytical

Measurement, Second Edition, Webaddress www.vtt.fi/ket/eurachem/quam2000-p1.pdf, 2000.

[15] New Statistics to NATA's ProficiencyProgrammes, National Association ofTesting Authorities, Australia, 1997.

[16] BIPM website: www.bipm.fr

[17] IMEP website: www.imep.ws

[18] PTAC Report No. 204 on WaterProficiency Testing Sub-programme 26,National Association of TestingAuthorities, Australia, September 1996.

219

The Provision of Reference Materials in Japan

1. Introduction

The importance of establishing commonintellectual assets and systematized scientificand technical information has rapidly increasedwith the developments in R&D and industrialactivity in recent years. In particular, laboratoryaccreditation based on the ISO/IEC 17025Quality System and mutual recognition havebecome more common in order to eliminate



TOSHIAKI ASAKAINational Institute of Technology and Evaluation2-49-10, Nishihara, Shibuya-ku, Tokyo 151-0066


[Received : 06.07.2004]

Abstract

The importance of constructing an intellectual infrastructure has increased in recent years due tothe globalization of industrial activities and advancement of R&D in areas in which a large numberof chemical substances are handled. The development of an intellectual infrastructure consisting ofa wide variety of reference materials and standard reference data is essential. Reflecting the growingneed for highly reliable chemical substances in Japan, a strategic plan for its supply was establishedmainly by the Ministry of Economy, Trade and Industry in 1998. The plan included the supply systemfor national metrological standards through the Japan Calibration Service System (JCSS), thepromotion of a chemical database, the distribution of biological standards and related databases,and other industrial reference materials. The reference materials such as standard gases and solutionsare provided by JCSS based on the Measurement Law of Japan. Other standards, as well as referencematerials for iron and steel, fine ceramics and cements, are provided by not only the NationalMetrology Institute of Japan (NMIJ) but also by several private companies and industrialassociations. JCSS and the other schemes such as an interlaboratory certification have progresseddue to the effective use of results of proficiency testing and accreditation.


technical barriers to international trade.Therefore, it is essential to provide reliablereference materials that have traceability to SIunits or meet ISO/IEC guides. Japaneseindustries depend almost entirely on the variousresources imported from abroad; however, thesignificance of intellectual infrastructureimprovement at home is reaffirmed in light ofeconomic globalization, leading to thedevelopment of sustainable industry andintelligence sharing.

220

Toshiaki Asakai

In Japan, the development of metrologicalstandards, reference materials, biologicalresources and related databases for improvedintellectual infrastructure is lagging far behindother developed countries. One of the reasonsfor this situation is that emphasis is placed onbasic research and innovative research inuniversities and national laboratories ratherthan on the development of intellectual assets.Most metrological standards are presentlyprovided through the Japan Calibration ServiceSystem (JCSS) based on the Measurement Law[1], although there are problems concerninglack of quantity and scope of supply. Enhancedsystems of national laboratories, collaboratorsand a traceability system are eagerlyanticipated, but there are challenges toproviding diverse reference materials withinJCSS and most reference materials for industrialuse are provided by other organizations suchas national laboratories, independentadministrative institutions, aggregatecorporations and private companies. Atraceability system of certified referencematerials provided only by private companies,and a lack of organic and environmentalreference materials are urgent problems thatmust be solved. In addition, the collection andacquisition of biological resources areconsiderable issues for biological industriesconsidered to be a next-generation key industry.The promotion and acquisition of biologicalresources at home is quite importantconsidering the difficulties in accessing overseasinformation infrastructures under certaintreaties such as the biodiversity treaty.

The Basic Program for Science andTechnology adopted in 1996 and the ActionPlan for Change and Creation of the EconomicStructure proposed in 1997 at a Cabinetmeeting mentioned the importance of intensiveimprovement of intellectual infrastructure.Reflecting such a situation, the SpecialCommittee for Intellectual InfrastructureDevelopment was established by a Joint Sessionof the Industrial Technology Council and the

Japanese Industrial Standards Committee. Thisspecial committee laid out the framework for anational project on the progression ofintellectual infrastructure [2]. Emphasis wasplaced on the need to establish the frameworkfor industry-government-academia collabora-tion and clarify role sharing. In particular, itclarified the government-centered structure toimprove metrological standards and referencematerials, and strategic positive support forbiological standards and resources by thegovernment through various industries andacademies. Furthermore, the enrichment ofconformity assessment based on ISO/IECguides and other international standards, andthe guarantee of a stable traceability system areessential to the reference materials provided byprivate companies.

2. Japan Calibration Service System basedon the Measurement Law of Japan

Metrological units require a high degree ofaccuracy in order to facilitate economic, socialand foreign trade activity. Qualitymanagement systems employed bymanufacturers demand that measurementinstrumentation be linked to national orinternational metrological standards. TheJapan Calibration Service System (JCSS) is thenational measurement standards provisionsystem and also the calibration laboratoryaccreditation system. [1-3]. It has beenestablished to carry out thorough qualitycontrol, ensure accurate measurement,promote smooth global trade and secure ahighly reliable traceability system on industrialproduction processes. InternationalAccreditation Japan (IAJapan), NITE, acts asthe accreditation body of JCSS and conductsaccreditation processes conforming to ISO/IECGuide 58 and relevant international criteria.Under the JCSS calibration laboratoryaccreditation system, calibration laboratoriesare assessed and registered as accreditedcalibration laboratories meeting therequirements of the Measurement Law,

221


relevant regulations and ISO/IEC 17025.Through the accreditation of the technicalcompetence of calibration laboratories, JCSSplays an important role in establishingconfidence in measurement or test data throughthe calibration service and measurementtraceability to the national standards. As ofSeptember 2003, calibration fields covered 20areas, such as length, mass, force, pressure,electricity, temperature, hardness andhumidity. Reference materials (concentrations)are included in one of accreditation areas [4].

2.1. Standard Solutions and Standard Gases

Primary standards of standard solutionsinclude pH [5-7], metal [8-12] and non-metalstandard solutions [13-14]. Standard gases areprepared on the basis of the gravimetricblending method and include organic,inorganic, zero-point control gases and gasmixtures [15-17]. The National Institute ofAdvanced Industrial Science and Technology(AIST mainly, former National Institute ofMaterials and Chemical Research, the NationalResearch Laboratory of Metrology and theElectrotechnical Laboratory) handles theprovision of standard solutions based oninternational comparisons. The supplysituation for reference materials as of June 2002is shown in Table 1 [18]. It should be notedthat this table shows the supply plan proposedby the Special Committee for IntellectualInfrastructure Development, and includes theJCSS provision plan and other national plans.

In May 2004, the Minister of Economy,Trade and Industry appointed the ChemicalsEvaluation and Research Institute, Japan(CERI) as a designated calibration body inaccordance with the traceability system basedon the Measurement Law. In this capacity,CERI produces reference materials that includestandard gases, pH standard solutions, metalstandard solutions and ion standard solutionscalibrated directly to national standards byaccredited calibration laboratories. In the pH

solution field, Kanto Chemical Co., KishidaChemical Co., Ltd., Katayama ChemicalIndustries Co., Ltd., Nacalai Tesque, Inc. andWako Pure Chemical Industries, Ltd., Inc. havebeen accredited. Kanto Chemical Co. andWako Pure Chemical Industries, Ltd., Inc. havealso been accredited in metal and ion standardsolutions [4].

Accredited calibration laboratories providestandard gases calibrated by CERI as well.Kawasaki Sogo Gas Center, Japan FineProducts K.K., Sumitomo Seika Chemicals Co.,Ltd. and Takachiho Chemical Industrial Co.,Ltd. are accredited calibration laboratories inthe standard gas fields.

JCSS is an efficient system for providingplenty of reference materials linked to nationalstandards. In addition, the Special Committeefor Intellectual Infrastructure Developmentcreated a provision plan and a developmentproject for highly reliable reference materialsbased on the needs of analysts and society ingeneral. However, there is a problem with alack of accredited calibration laboratories forspecific reference materials because manycorporate managers have yet to realize thesubstantive benefits. Therefore, severalreference materials such as organic standardsolutions are not marketed through accreditedcalibration laboratories. Reflecting such asituation, the Special Committee for IntellectualInfrastructure Development has established aWorking Group in which the members discussa more effective provision system and newaccreditation scheme involving particular kindsof materials. In addition, Table 1, SupplySituation of Reference Materials, is beingrevised.

2.2. Standards of Physical Properties

JCSS was primarily established for thepurpose of ensuring the traceability ofmeasurement to measuring instruments ortesting machines used at the working level.

222

Toshiaki Asakai

Table 1The supply situation of reference materials, as of June 2002

Category 2001

Standard gas Zero point control standard gas Ethanol standard gasMethane standard gas Chloroform standard gasPropane-air standard gas Dichloromethane standard gasPropane-nitrogen standard gas Tetrachloroethylene standard gasCarbon monoxide standard gas Trichloroethylene standard gasCarbon dioxide standard gas Benzene standard gasSulphur dioxide standard gas 1,2-Dichloroethane standard gasNitrogen dioxide standard gas 1,3-Butadiene standard gasNitrogen monoxide standard gas Acrylonitrile standard gasOxygen standard gas Vinyl chloride standard gasAmmonia standard gas o-Xylene standard gasN2 Low Conc. NOx. Zerogas m-Xylene standard gasAir Low Conc. SOx. Zerogas Toluene standard gasLow Conc. NO standard gas Ethylbenzene standard gasLow Conc. SO2 standard gasZero gas (VOC free)

Inorganic standard Sodium standard solution Molybdenum standard solutionsolution Potassium standard solution Strontium standard solution

Calcium standard solution Rubidium standard solutionMagnesium standard solution Thallium standard solutionAluminium standard solution Tin standard solutionCopper standard solution Fluoride Ion standard solutionZinc standard solution Chloride Ion standard solutionLead standard solution Sulfoxide Ion standard solutionCadmium standard solution Ammonium Ion standard solutionManganese standard solution Nitrous Ion standard solutionIron standard solution Nitric Ion standard solutionNickel standard solution Phosphoric Ion standard solutionCobalt standard solution Bromide Ion standard solutionArsenic standard solution Cyanide Ion standard solutionAntimonial standard solution Oxalic Acid Salt pH standard solutionBismuth standard solution Phthalic Acid Salt pH standard solutionChromium standard solution Neutral Phosphoric Salt pH standard solutionMercury standard solution Boric Acid Salt pH standard solutionSelenium standard solution Carboxylic Acid Salt pH standard solutionLithium standard solution Phosphoric Acid Salt pH standard solutionBarium standard solution

Organic Standard Dichloromethane standard solution Tribromomethane standard solutionsolution (VOCs) Tetrachloromethane standard solution Bromodichloromethane standard solution(Endocrine disrupters)Chloroform standard solution Dibromochloromethane standard solution(PCBs) (Pesticides Tetrachloroethylene standard solution t-1,2-Dichloroethylene standard solution and the deriva- Trichloroethylene standard solution 1,2-Dichloropropane standard solutiontives) (PAHs) Benzene standard solution 1,4-Dichlorobenzene standard solution

1,2-Dichloroethane standard Di-2-ethylhexyl phthalate standard solutionsolution

Contd...

223


1,1,1-Trichloroethane standard Di-n-buthyl phthalate standard solutionsolutionToluene standard solution Diethyl phtalate standard solutiono-Xylene standard solution Buthyl benzyl phthalate standard solutionm-Xylene standard solution Bisphenol A standard solutionp-Xylene standard solution Nonylphenol standard solution1, 1-Dichloroethylene standard 4-t-Octylphenol standard solutionsolutionc-1,2-DichloroethyIene standard 4-t-Butylphenol standard solutionsolution1,1,2-Trichloroethane standard 4-n-Heptylphenol standard solutionsolutiont-1,3-Dichioropropene standard 2,4-Dichlorophenol standard solutionsolutionc-i 3-Dichloropropene standardsolution

High purity materials Ethanol 1,2-dichloroethaneEthylbenzeneToluene

Reference materialsfor temperaturefixed point

Organic matrix Sediment for organotin analysis Soil for High Conc. Dioxins analysisreference materials High Conc. PCB sediment Soil for Low Conc. Dioxins analysisfor environmental Low Conc. PCB sedimentanalysis Field soil for High Conc.

Residual Pesticides analysisField soil for Low Conc.Residual Pesticides analysis

Inorganic matrix Marine sediment for toxicreference materials metal elements analysis

Multilayer standards GaAs/AlAs Superlatticeof the advanced (25nm each, 4 layers)materials

Thin films

Advanced materials

Ion implantation

Lattice defect

Polymer Reference material for modulusof elasticity in tensile test of plastics

Non-ferrous metal

Metal reference Pb-free solder reference materialmaterials

ceramics

Table 1 contd...

Contd...

224

Toshiaki Asakai

Category 2002

Standard gas 3 VOCs standard gas mixture

Inorganic standard Boron standard solutionsolution Cesium standard solution

Indium standard solutionTellurium standard solutionGallium standard solutionVanadium standard solutionIodide Ion standard solution

Organic Standard 23 VOCs standard solutionsolution (VOCs) mixture (JIS K 0125)(Endocrine disrupters)6 Alkylphenols standard(PCBs) (Pesticides solution mixture and the deriva-tives) (PAHs)

High purity materials Benzene Diethyl phthalateo-xylenem-xylene


Organic matrix Fly ash, Dioxins in Low levelreference materials Fly ash, Dioxins in High levelfor environmentalanalysis

Inorganic matrix Lake sediment for toxicreference materials metal elements analysis

Multilayer standards SiO2 thin multilayerof the advanced (20nm each, 5 layers)materials

Thin films

Advanced materials

Ion implantation

Lattice defect

Polymer Polystyreneoligomer reference Polymer viscoelasticity standardmaterial (PS1000)Polycarbonate reference material Reference test pieces for charpy impact strength

Contd...

Table 1 contd...

225


Non-ferrous metal Iron-chromium alloy (Cr 5%) Iron-nickel alloy (Ni 40%)Iron-chromium alloy (Cr 10%) Iron-nickel alloy (Ni 60%)Iron-chromium alloy (Cr 20%) Iron-carbon alloy (C 0.1%)Iron-chromium alloy (Cr 30%) Iron-carbon alloy (C 0.2%)Iron-chromium alloy (Cr 40%) Iron-carbon alloy (C 0.3%)Iron-nickel alloy (Ni 5%) Iron-carbon alloy (C 0.5%)Iron-nickel alloy (Ni 10%) Iron-carbon alloy (C 0.7%)Iron-nickel alloy (Ni 20%) Iron-chromium alloy (Cr 40%)

Metal referencematerials

ceramics

Category 2005

Standard gas Acetoaldehyde standard gasSF6 standard gasHigh Conc. 5 BTX standard gasmixtureLow Conc. 5 BTX standard gasmixtureHigh conc 9 VOCs standard gasmixtureLow Conc. 9 VOCs standard gasmixtureHigh conc 22 VOCs standard gasmixtureLow Conc. 22 VOCs standard gasmixtureHigh conc 16 VOCs standard gasmixtureLow Conc. 16 VOCs standard gasmixtureHFC standard gas mixtureHCFC standard gas mixturePFC standard gas mixture

Inorganic standard Titanium standard solutionsolution Scandium standard solution

Yttrium standard solution

Organic Standard Acetoaldehyde (DNPH p,p'-DDE standard solutionsolution (VOCs) derivative) standard solution g-HCH standard solution(Endocrine disrupters)Formaldehyde (DNPH derivative)(PCBs) (Pesticides standard solution and the deriva- Phenol standard solutiontives) (PAHs) Dipropyl phthalate standard

solution

Table 1 contd...

Contd...

226

Toshiaki Asakai

Dipentyl phthalate standardsolutionDihexyl phthalate standardsolutionDicyclohexyl phthalate standardsolution8 Phthalates standard solutionmixtureDi(2-ethylhexyl)adipate standardsolution2,4,4'-Trichlorobiphenyl standardsolution2,2',4,4',5,5'-Hexachlorobiphenylstandard solution2,2',3,3',4,4',5,-Heptachlorobiphenylstandard solution2,2',3,3',4,4',5,5'-Octachlorobiphenylstandard solution2,3'4',5-Tetrachlorobiphenyl(PCB70)standard solition2,3,3',4,4'-Pentachlorobiphenyl(PCB105) standard solition6 PCBs standard solition mixturep,p'-DDT standard solution

High purity materials Thiuram CholesterolSimazine High purity material for NMRThiobenecarb

Reference materials Benzene for thermal analysis Toluene for thermal analysisfor temperature o-xylene for thermal analysis Ethanol for thermal analysisfixed point m-xylene for thermal analysis

Organic matrix Fish oil for DDE, DDT, HCH Sediment for DDT, DDE analysisreference materials analysis Soil for DDT, DDE analysisfor environmental Sediment for organotin analysis Water for Low Conc. Dioxins analysisanalysis Biological standard for arsenic Water for High Conc. Dioxins analysis

compound analysisSoil for PCBs analysisSediment for PCBs analysis

Inorganic matrix Riverine water for Low Conc.reference materials toxic metal elements analysis

Riverine water for High Conc.toxic metal elements analysis

Multilayer standards GaAs/AlAs multilayerof the advanced (10nm or less each layer)materials

Table 1 contd...

Contd...

227


Thin films SiO2 on the silicon wafers(3nm - 10nm)

Advanced materials Scale in-plane (25nm-100nm)

Ion implantation

Lattice defect

Polymer Polystyreneoligomer reference Polycarbonate reference materialmaterial (PS300)Polystyreneoligomer reference Super fine grain reference materialmaterial (PS2500) (<100nm)

Non-ferrous metal

Metal reference Potassium chloride Noble metal alloymaterials

ceramics Alpha silicon carbide Thermal diffusivity (silicon nitride)Beta silicon carbide Thermal conductivityThermal diffusivity Modulus of elasticity

Category 2010

Standard gas Formaldehyde standard gasChloromethyl methyl ether standard gasEthylene oxide standard gasHigh conc 44 VOCs standard gas mixtureLow Conc. 44 VOCs standard gas mixtureLow conc short-chain hydrocarbon standard gas mixtureNatural gas standardNon-methane hydrocarbon standard gas mixtureStandard gas mixture for sick house analysis4 sulphur compounds standard gas mixtureDinitrous monoxide stndard gas

Inorganic standard Beryllium standard solutionsolution Germanium standard solution

Palladium standard solutionHafnium standard solutionZirconium standard solutionTungsten standard solutionNiobium standard solutionGold standard solutionSilver standard solution

Organic Standard Naphthalene standard solutionsolution (VOCs) Fluorene standard solution(Endocrine disrupters)Anthracene standard solution(PCBs) (Pesticides Phenanthrene standard solution

Table 1 contd...

Contd...

228

Toshiaki Asakai

and the deriva- Fluoroanthene standard solutiontives) (PAHs) Chrysene standard solution

Benzo[a]pyrene standard solutionPerylene standard solution

High purity materials Benzo[a]pyrene


Organic matrix Sediment for organomercury Fine particles for Low Conc. PAHsreference materials analysis analysisfor environmental Biological standard for PCB Fine particles for High Conc. PAHs analysisanalysis analysis

Biological standard for DDT,DDE analysisSoil for Low Conc. PAHs analysisSoil for High Conc. PAHs analysis

Inorganic matrix Nearshore seawater for toxic trace Fine particles for volatile elements analysisreference materials metal analysis

Open ocean seawater for toxic tracemetal analysis

Multilayer standards Ta2O3/SiO2 multilayerof the advanced (5nm or less each layer)materials

Thin films Ta2O3 on the silicon wafers , thin Au on the silicon wafers (2nm or less)films with concentration properties

Advanced materials Polydisperse polymer reference Ultrafine particle reference materialmaterial (<50nm)

Ion implantation Silicon ion implantation

Lattice defect Defective standard in silicon Hyperfine vacancy standard in polymeroxide film

Polymer Polyethyleneglycol reference Polymer reference material with addition agentmaterial (PEG1000) (PC, Bisphenol A)Polymer reference material with Water-soluble polymer reference materialaddition agent (PVC, Phthalate)

Non-ferrous metal

Metal reference Ta (Tantalum)materials

ceramics

Table 1 contd...

229


Therefore, there are barely any referencematerials based on JCSS from the point of viewof providing standards with physicalproperties despite the wide range ofaccreditation fields. Several laboratories dealingwith heat (benzoic acid for calorimetry), densityand hardness have been accredited [4].

The Japan Quality Assurance Organization(JQA) provides the Benzoic Acid CalorimetricStandard with 0.01 kJ/(g•20 °C) (k = 2)uncertainty in calibration level. In the densityarea, most of the laboratories mainly providethe calibration service for density instrumentsbased on the law of harmonic oscillation. Someof the laboratories provide buoy and densitystandard solutions. JQA calibrates buoy from0.60 g/cm3 to 2.00 g/cm3 with less than 0.00015g/cm3 (k = 2) uncertainty, buoy for spirits ofwine from 0 vol% to 100 vol% with 0.09 vol%(k = 2). The National Research Institute ofBrewing also calibrates buoy for spirits of wine.Kyoto Electronics Manufacturing Co., Ltd.supplies density standard solutions from 0.69g/cm3 to 1.50 g/cm3 with less than 0.00005g/cm3 (k = 2) uncertainty. The Japan BearingInspection Institute and Fuji Testing MachineCo., Ltd. play a role in the traceability ofinstruments for Rockwell hardness. The formercalibrates the standard test blocks for Rockwellhardness from 20 HRC to 65 HRC with lessthan 0.44 HRC (k = 2) uncertainty.

The national system for the provision ofreference materials for physical properties hasyet to reach a satisfactory level. On thataccount, JCSS is being restructured and thereare movements to provide various referencematerials outside JCSS. Reflecting the lattermove, the restructuring of JCSS at an early stageor the development of a new system is needed.

3. Status on the Provision of ReferenceMaterials other than from JCSS

JCSS was primarily established for thepurpose of ensuring the traceability ofmetrological standards such as length and

mass. It is an explicit traceability systemcentered on the National Metrology Instituteof Japan (NMIJ in AIST); however, thereference materials provision system ispresently inadequate due to the rapidlyincreasing demand for an immense variety ofreliable reference materials. Thus, mostreference materials needed by laboratories andindustries are presently provided by AIST, othernational laboratories, foundations,incorporated associations and privatecompanies. A list of the major providers ofreference materials is shown in Table 2 [2, 18-20].

AIST proactively supplies the latest certifiedreference materials in demand. High-purityorganic materials, 1,2-dichloroethane, m-xylene, o-xylene, ethanol, ethylbenzene,toluene, diethyl phthalate, benzene and so onare provided by using freezing pointdepression, the primary method ofmeasurement. Heat capacity was determinedby adiabatic calorimeter and the total amountof impurities was calculated by van't Hoff plot.These certified reference materials includeindicative values determined by Karl-Fischertitration, GC-MS, GC-FID and ICP-MS. Severalstandard gas mixtures such as cis-1,2-dichloroethylene, 1,1,1-trichloroethane and p-xylene are also supplied by gravimetric methodusing purity-determined materials that are SItraceable and have uncertainty and stabilitydata. In inorganic materials, Fe-Cr alloy, Fe-Nialloy and Fe-C alloy reference materials forElectron Probe Micro Analyzer (EMPA) werereleased in 2003. These were assigned by thetitration method and their uncertainties weredetermined by analyzing the titration andEMPA results. Iron-chromium alloy (Cr40%)for X-ray fluorescence analysis was alsoreleased. This is used for calibration of the X-ray fluorescence spectrometer and evaluationof the secondary excitation effect, and wasassigned by the method of titration and isotopedilution mass spectrometry. Informative valuesmeasured by monochromatic X-ray

230

Toshiaki Asakai

Table 2List of major providers of reference materials in Japan

Providers Type of materials

The Japan Iron and Steel Federation Iron and steelJapan Copper and Brass Association RMs for analyzing brassJapan Aluminium Association RMs for analyzing alminumJapan Aluminium Alloy Refiners Association RMs for analyzing alminum alloyThe Ceramic Society of Japan CeramicsJapan Fine Ceramics Center CeramicsJapan Cement Association CementThe Japan Petroleum Institute PetroleumJapan Chemical Innovation Institute PlasticsJapan Bearing Inspection Institute Standard pieces for hardnessThe Japanese Society for Non-Destructive Standard pieces for analyzing ultrasonicInspection examinationThe Japan Institute of Energy CokesJapan Fertilizer and Feed Inspection Association Standards for analyzing fertilizerThe Technial Association of Refractories RefractoriesThe Japan Society for Analytical Chemistry RMs for environmental analysisThe Japan Titanium Society TitaniumHealth Care Technology Foundation Clinical RMsSociety of Japanese Pharmacopoeia PharmacopoeiaNational Institute for Environmental Studies EnvironmentalJapan Quality Assurance Organization Optical filter, microscale, thermal analysisNational Institute of Advanced Science and Technology Gases, geochemical, organic, inorganic, etc.National Institute of Technology and Evaluation RMs for volumetric analysis

fluorescence spectrometer were shown as well,and the certified value is in good agreementwith the informative value. Since June 2004,AIST has also provided polychlorinatedbiphenyls and organochlorine pesticides (highpollutant concentrations) and trace elementsreference materials in marine sediment.Furthermore, Geological Survey of Japan inAIST supplies 37 kinds of mineral referencematerials such as andesite, basalt, chert,granodiorite, gabbro and feldspar [21-22].

In the iron and steel, and nonferrous metalfields, corporations and federations play asignificant role in the provision of referencematerials. Since June 2004, the Japan Iron andSteel Federation, the largest producer of ironand steel reference materials, has provided 345kinds of reference materials. The method ofcertification, mainly of elements, is

interlaboratory comparison. The Federationalso takes part in international standardizationactivities. The Japan Copper and BrassAssociation, Japan Aluminium Association,Japan Aluminium Alloy Refiners Associationand the Japan Titanium Society providereference materials for analyzing brass,aluminum, aluminum alloy and titanium in thenonferrous metal field, respectively.

The importance of reference materials forenvironmental analysis is especially increasingdue to the complexity of environmental issuesand difficulty of analyzing environmentalsubstances. The National Institute forEnvironmental Studies certifies elementsincluding environmental substances andprovides 13 kinds of reference materials forenvironmental analysis: pepperbush, rice flour-unpolished (high, medium, low Cd content),

231


fish tissue, marine sediment, pond sediment,human hair, human urine, fish otolith,chlorella, vehicle exhaust particulates andsargasso. Certification adopts several methodsincluding atomic absorption spectrometry,flame emission spectroscopy, ICP-AES, X-rayfluorescence analysis, isotope dilution massspectrometry, neutron activation analysis,photon activation analysis, gravimetric analysisand absorption spectroscopy. In anotherexample, the Japan Society for AnalyticalChemistry (JSAC) proactively providesenvironmental materials based oninterlaboratory certification. Marine and riversediment for analysis of dioxins and PCBcongeners (high/low level content), fly ash andforest soil including several levels of dioxins,river water containing trace metals, volcanicash soil and so on are provided by JSAC usingICP-MS, isotope dilution-ICP-MS, ICP-AES,hydride generation-ICP-AES, ionchromatography, etc. Another example is theJapan Fertilizer and Feed InspectionAssociation that releases standards foranalyzing fertilizer.

The National Institute of Health, JapanRadioisotope Association, Japan PetroleumInstitute, Japan Bearing Inspection Institute, JapanInstitute of Energy, JQA and the Ceramic Societyof Japan provide the standards used for dye analysis,radioactivity, petroleum, hardness, cokes, filters andmicroscales and 37 kinds of ceramics, respectively.In addition, the National Institute of Technologyand Evaluation (NITE) certifies and providesreference materials for volumetric analysis. Thestoichiometric standards are consist of 11 materialsused in oxidimetric, acidimetric, chelatometric andprecipitation titration. High-purity substances areprepared by several manufacturers in Japanand certificated by NITE.

4. Clinical Standards and BiologicalResources

Biotechnology is a fundamental sciencecovering a wide range of academic fields such

as medicine, agronomy, pharmacology,physiology, science and engineering, and is ahigh-priority industry expecting widespreadapplication in the fields of healthcare, chemical,machinery and environment protection. InJapan, the Action Plan / Basic Plan approvedin a Cabinet meeting in 1997 definedintellectual infrastructure improvement,application and commercialization ofbiotechnology as the objectives. In 2003, thesubcommittee of the Science Council of Japancompiled a report on the development ofreference materials concerning biotechnology-based medicines and human healthcare [23].Reflecting the growth of MRA activities ofmetrological standards (physical propertiesand chemical properties), emphasis has beenplaced on the immediate establishment oftraceability of biological and clinical standards.A strategic provision scheme in this area ispractical in consideration of the difficultiesestablishing a SI traceable system in manycases. On the other hand, comparisonmeasurement between real samples andreference materials is generally used inmeasuring biotechnology-based medicine, e.g.measuring of electrolytes and low-molecular-weight compounds. Therefore, there is a strongneed for providing reference materials withreliable stability data and matrix substances.

The Health Care Technology Foundation(HECTEF) is one of the largest laboratoriesproviding clinical standards. Three kinds ofclinical standards (10 concentrations) certifiedby HECTEF have been registered on theinternational database for certified referencematerials (COMAR) [19]. The first type is acertified reference material for measurement oftotal cholesterol in human serum [24]. It isintended for use in evaluating the accuracy oftotal cholesterol assays as part of clinicallaboratory tests and validating secondary orworking reference materials. When stored at atemperature below -70°C, its expiration date is6 months. The total cholesterol concentrationswere obtained by isotope dilution / mass

232

Toshiaki Asakai

spectrometry performed by the StandardReference Center in HECTEF. The second typeis a reference material for ion selective electrode(ISE) meeting the requirements for certifiedreference material as a calibrant for ISE asdefined in the Recommendation forMeasurement of and Conventions for ReportingSodium and Potassium by Ion-selectiveElectrode in Undiluted Serum, Plasma orWhole Blood, established by the InternationalFederation for Clinical Chemistry (IFCC), Ion-selective Electrode Working Group [25-26]. Itis intended for use in evaluating the accuracyof serum, plasma Na, K and Cl measurementsobtained by ISE in clinical laboratory tests. Thecertified Na values were measured bygravimetry-based ion exchange separationmethod, the K values by isotope dilution massspectrometry, and the Cl values by internalstandard ion chromatography and coulometrictitration. The last type is a reference materialfor measurement of HbA1c [27-28]. The HbA1cconcentrations were measured using the KO500method, which is a high-resolution high-performance liquid chromatography technique.Analyses were performed by Keio University,HECTEF and a pathology laboratory approvedby the Committee on Standardization ofLaboratory Testing Related to Diabetes Mellitus.HECTEF also supplies standard serum (frozen)used for fat analysis with the values of totalcholesterol (T-CHO), HDL-C and triglyceride(TG), and glucose standard serum, artificialstandard used for blood gas analysis andstandard serum used for serum iron except forregistered materials on COMAR.

In the pharmaceutical industry, theJapanese Pharmacopoeia was set up andproduced by the Committee on JapanesePharmacopoeia in order to ensure appropriatemedical descriptions and medicinal qualities.The Japanese Pharmacopoeia is a standard ofqualities and descriptions, and includes generalnotices, general rules for preparations, andgeneral tests, processes and apparatus, officialmonographs, and general rules for crude drugs.

The National Institute of Infectious Diseasesand the Society of Japanese Pharmacopoeiadistribute standards used in the JapanesePharmacopoeia. The former provides morethan 200 kinds of standards used for medicalanalysis. The latter provides over 150 standardsused in the Japanese Pharmacopoeia, tar dyestandards for thin-layer chromatography andfood additive standards.

For enzyme properties, the JapaneseCommittee for Clinical Laboratory Standards(JCCLS) supplies enzymatic activity standards.ALT (L-alanine:2-oxyglutarate amino-transferase), AST (L-aspartate:2-oxyglutarateaminotransferase), AMY (amylase), CKcreatinekinase), GGT (gamma-GT, gamma-glutamyl transpeptidase), LDH (lactatedehydrogenase), ALP (ortho phosphoric-monoester phosphohydrolase) have beenprovided [23].

In the meantime, infrastructuredevelopment of biological resources has beenplanned in parallel with the progression ofbiological and clinical standards, which meansthe establishment of culture collection, DNAsequence of chromosomes, proteome analysisand their databases. Commercial items such asdatabases, software and instruments areexpected through private-sector-centereddevelopment because there is a high possibilityof return on investment. The collection of basicbiological, genetic and protein information andanalytical data requires government-centereddevelopment. Information on the DNA andproteins of useful pathogenic microorganismsand microorganisms in extreme environmentalconditions, e.g. thermophilic and alkalophilicmicroorganisms, is an intensive subject. In lightof the increasing need for biologicalinformation, a plan was designed for thepurpose of establishing a core organization tomaintain and supply about 50 000 biogeneticresources by the year 2005 and about 100 000resources by 2010. Furthermore, databases onthe biological characteristics of resources and

233


produced substances are scheduled fordevelopment. The National Institute ofTechnology and Evaluation (NITE) promotesgenomic analysis of microorganisms used forhuman healthcare and industrial processes,and intends to release more than 85 Mbps ofgenomic information by 2005. In the humangenome project, several laboratories conductcDNA and SNP mapping of Japanese, and by2002 had defined 300 000 cDNA and 100 000- 150 000 SNPs. By the end of 2010, theinformation obtained from several researcheswill have been comprehensively managed [18].

5. Physical Properties

5.1. Reference Materials with PhysicalProperties

Data on the physical properties andfunctions of various new and similar materialsis essential in the research of new materials,new measurement methods and evaluation ofnovel substances. In particular, using materialswith reliable values and properties is crucialfor the prevention of excessive loss and highrisks in product evaluation. The importance ofestablishing assessment procedures, supplyingaccurate reference materials and systematicaccumulation of data on physical properties isincreasing. However, a system to providereference materials with physical properties hasnot yet been completely established at a nationallevel. For the provision of data on standardproperties, academic society and nationallaboratories have collected extensiveinformation on metal, mechanical andchemical properties; however, the informationis not systematically and broadly available.

Reflecting such a situation, AIST hasdeveloped reference materials with physicalproperties outside JCSS over the past severalyears. For example, reference materials for theCharpy impact strength of plastics and theirdynamic mechanical properties have beenreleased. The former plastics are PVC, PMMAand ABS for Charpy impact strength and

homogeneities, the stabilities of which weredetermined by 16 laboratories. The latterplastics are PEEK, PE-UHMW, PMMA andPVC, the certified values of which wereassigned by an interlaboratory comparison at12 laboratories. Another interesting material,polystyrene, used for evaluating molecularweight distribution and average molecularweight is provided. The polymerization degreeof each component was determined by matrix-assisted laser desorption/ionization - time offlight mass spectrometry (MALDI-TOFMS),and mass fraction, molar fraction, weight-average molecular weight, number-averagemolecular weight and polydisperse degree weredetermined by supercritical fluidchromatography. In addition, AIST alsosupplies 13 kinds of standard solutions usedfor calibration of viscometers, and releasesinformation on kinetic viscosity at varioustemperatures.

The Japan Fine Ceramics Center (JFCC) isa core foundation that releases fine ceramicsreference materials and their database. JFCCreleases 5 kinds of reference materials. The firstone is a thermal history sensor, mainly madefrom silicon oxide and aluminum oxide, usedfor measuring thermal history in calcinationsprocesses ranging from 600-1700°C. Measuringthermal history is important for the control ofceramic properties, and is determined bymeasuring shrinkage. The second type ofmaterials is silicon nitride sintered body andzirconia sintered body, used for evaluation ofmachine work testing. Density, fracturetoughness, bending strength, Vickers hardness,thermal conductivity, thermal expansion andelemental properties are assigned. The thirdtype is 5 different reference powders forparticle-size distribution, and is made frombarium titanate, silicon nitride, boron nitride,silicon carbide and alumina. The next one is areference material for thermal diffusivityanalysis, certifying the values of thermaldiffusivity and uncertainty, at roomtemperature and 1000 K. It is made from

234

Toshiaki Asakai

alumina polycrystal used mainly in the laserflash method. The last one is used for complexpermittivity in microwaves (5 GHz). It leads tohigh-accuracy evaluation of relativepermittivity and dielectric tangent of low-loss-dielectric material. The dielectric tangent andrelative permittivity are certified, and the waterabsorption coefficient, insulation resistance,linear expansion, thermal conductivity, specificheat, density, Vickers hardness and bendstrength are indicated. JFCC also developsstandard reference data (hereinafter).

Another producer of materials withphysical properties is the Japan Seger ConeAssociation, which supplies seger cones. Segercones are used not only in the ceramic industrybut also in controlling calcined substances andrefractory testing as standard cones. Segercones provided by the Japan Seger ConeAssociation consist of 42 kinds of large conesand 17 kinds of small cones at various meltingtemperatures. In the cement industry, theJapan Cement Association provides standardreference cement materials for strength testsand fineness analysis. The former is certifiedby interlaboratory testing (12 laboratories) andis assigned compression strength 3-28 daysafter preparation. The latter is measured at 9laboratories that certify the value of specificsurface areas.

5.2. Database for Physical Properties

The improvement of the extensively useddatabase on material properties is an importantissue in parallel with the progression ofreference materials with physical properties.Academic society and national laboratorieshave collected a great deal of information onthe mechanical and chemical properties ofmetal materials and have establishedmeasuring methods. The Institute for MaterialsResearch (IMR), Tohoku University, releases thedatabase on metal, KIND. As of 2003,information on over 70 000 papers presentedby IMR, on high-temperature superconductors,

magnetic material, amorphous alloys and soon has been released on the Internet. TheNational Institute for Materials Science (NIMS)also provides materials information. CCT (370weld CCT, 2500 singular points and 2500micrograms), over 10 000 thermo andsuperconductor properties, 30 000 propertiesrelated to superconductors, 160 electronicstructures from ab initio calculation, 4 800strength properties, about 30 000 crystalstructures used in the analysis of interaction ofmetals, 3000 X-ray diffraction data items, 15000 mechanical properties for the utilizationof nuclear power, 3500 diffusion coefficientsof metals and alloys and creep data areavailable.

JFCC intends to strategically develop theinformation on fine ceramics in cooperationwith industry, government, and academia.Establishment of evaluation methods of innerfriction, fatigue, elastic coefficient, bendstrength, madreporite character and powderproperties is planned, and their databases havebeen released as well. There is no broaddatabase on fine ceramics; however, theinformation on material properties is increasingas basic evaluation methods are developed.JFCC established a database on 25 000materials, the data extracted from about 7000papers on fine ceramics and classified basedon international collaboration with VAMAS.

In light of traceability of material properties,AIST (mainly NMIJ) is committed to theestablishment of measuring physical propertiesand traceability, and has compiled a database.A Japanese national project for developing newmeasurement methods and reference materialsfor solids, and compilation of a database wasstarted in over 10 laboratories in 1997 with a5-year term. The major goals of this projectwere the development of precisionmeasurement methods for solid materials andstandardization of methods for evaluating theuncertainty, and included a new networkdatabase system. AIST, NIMS (National

235


Institute for Materials Science), Nippon SteelCorporation, Keio University, IbarakiUniversity, JFCC, JUTEM (Japan Ultra-HighTemperature Materials Research Institute),Toray Research Center, Kyoto University, NAL(National Aerospace Laboratory) and ISIJ (Ironand Steel Institute of Japan) reported the resultson the development of new methods such asdensity, molar mass, thermal conductivity,thermal diffusivity, specific heat capacity,emissivity, sound velocity, elastic constant, etc.and released over 10 related papers [29]. Inaddition, NMIJ/AIST is developing a networkdatabase system for thermophysical propertydata in collaboration with scientists,researchers, and engineers who produce databy measurement and/or evaluation. Thus far,databases for physical property and referencedata have developed systematically; however,several databases are scattered throughoutlaboratories and universities. In most cases,there are many difficulties involved inmaintaining a database system by a singlegroup because new thermophysical data of abroad range of solid materials is produced daily.A novel alternative to independent databasesis a network database system. Independentdatabases in the personal computers ofcollaborators are merged into a master databasefile stored in the database server at a key stationand available for worldwide access via theInternet. This system will encourage dataregistrants to construct their own databasesand accumulate thermophysical property datafor a huge variety of materials. A networkdatabase has the benefits of guarantee ofownership, establishment of a light-loaddatabase and preservation of incentives for eachcollaborator.

The concept is to leverage a distributeddatabase system for compiling a database ofmaterials for atomic energy. This project, Data-Free-Way, is the construction of a distributeddatabase system for the design or selection ofadvanced nuclear materials [30], and was builtwith the cooperation of many institutes. As of

June 2004, NIMS (National Institute forMaterials Science), JAERI (Japan AtomicEnergy Research Institute), JNC (Japan NuclearCycle Development Institute), JST (JapanScience and Technology Corporation), AIST(former National Research Laboratory ofMetrology) and SRI (Ship Research Institute)are participating, and compiling their ownnuclear materials data, which is shared via theInternet. A notable feature of Data-Free-Wayis that the search results are retrieved from thedatabase without regard to distributed data,operating as a single huge database.

Regarding other databases, theInternational Medical Center of Japan and theJapan Science and Technology Agency releaseinformation such as names, structures,biological activities and physicochemicalproperties concerning fats. AIST and NIMSprovide data on over 30 000 compounds and100 000 spectrums, and information related topolymers, respectively.

6. Further Intellectual InfrastructureDevelopment

The Special Committee for IntellectualInfrastructure Development in conjunctionwith the numerous ministries including theMinistry of Education, Culture, Sports, Scienceand Technology, the Health, Labor and WelfareMinistry, the Agriculture, Forestry and FisheriesMinistry, the Ministry of the Environment, andthe Ministry of Economy, Trade and Industry,have planned intellectual infrastructuredevelopment in Japan.

By 2005-2010, in metrological standardsand reference materials, it is intended to supplyover 250 metrological standards and more than250 reference materials, especially electrical,nanotechnology and environmental standards.In biological genetic resources, it is planned tocollect 600 varieties of human cell strains, 5000pharmaceutical plants and 100 000 biologicalmicroorganism resources. In material sciences,ultrasensitive analytical methods using GC-MS,

236

Toshiaki Asakai

LC-MS and ICP-MS, and new evaluatingmethods for biomaterials, superconductivity,ultracold materials, surface and thin layers arebeing developed. In database infrastructures,databases of human genome, Japanese SNPsand over 3000 kinds of protein structures arebeing compiled.

Moreover, AIST has established aninvestigative committee for reference materials,which has finalized an investigative reportcarried out in 2002 to keep up on users' needs.This investigation consisted of a questionnairesurvey on user needs, interviews withproducers involved in highly needed referencematerials and research infrastructures relatedto reference materials in laboratories.Questionnaires were distributed to 1828 usersand answered by 738 users. The results of thequestionnaire survey on reference materialsusers indicate the reference materials urgentlyneeded, and include advanced materials andbiological standards, and comments on CCQMinternational comparison. The interviews with20 producers show the practical view ofdeveloping reference materials for the future.Basic information and new measurementmethods were received from the survey ofseveral laboratories. In accordance with theresults of the survey, the development plan hasbeen revised.

Finally, reference materials databasescovered a wide variety of materials have a partto play in advancement of industrial activitiesand high-accurate measurements through theproper use of reference materials. Informationof some reference materials producers andreference data can be reviewed throughReference Materials Total Information Servicesof Japan (RMinfo) provided by NationalInstitute of Technology and Evaluation (NITE)[20] and The International Database forCertified Reference Materials (COMAR)provided by Federal Institute for MaterialsResearch and Testing (BAM) [19].

7. Conclusion

There is an increasing need to supply high-quality diverse reference materials in responseto the high demand from academic society,manufacturers and laboratories. Existingsystems, JCSS and the scheme of interlaboratorycertification have progressed due to the effectiveuse of results of proficiency testing andaccreditation. Construction of intellectualinfrastructure in Japan is being promoted on anational level and greater availability ofreference data has been achieved in a user-friendly manner. Advancement of industrialactivity, science and technology is expected inaccordance with the advancement inknowledge and supplying of reference materialsfrom the national level to the user level.

8. Acknowledgements

The author is grateful to the member of TheReference Materials Division of NITE. Fruitfuldiscussions with Dr. Hidetaka Imai, Dr.Takashi Arai and Ms. Mariko Murayama atNITE are greatly appreciated.

References

[1] M. Kubota et al., Development and SupplySystem of Reference Materials Based on theMeasurement Law in Japan, Accred. Qual.Assur., 2(1997)130-136.

[2] For Improvement of IntellectualInfrastructure in Japan (in Japanese),Special Committee for IntellectualInfrastructure Development, 1998.

[3] M. Kubota, Report on the CITAC '99Japan Symposium (Held in Tsukuba) andPresent Status of Chemical Metrology inJapan, Analytical Sciences, 16(2000)445-447.

[4] IAJAPAN, Specific ApplicationDocuments on JCSS (in Japanese), 2004.

[5] S. Nakamura et al., Primary pH Standardand Reliability of pH Standard Solution,

237


Internal Report (in Japanese),83(1988)365-371.

[6] K. Shikakume et al., PreservationConditions of pH Standard Solutions (inJapanese), Bunseki Kagaku, 37(1988)17-21.

[7] S. Nakamura and M. Kubota, Accuracyof pH Standard Solutions (in Japanese),Bunseki Kagaku, 36(1987)58-60.

[8] A. Hioki et al., Electrothermal AtomicAbsorption Spectrometric Detemination ofCopper and Zinc in High-Purity Bismuthafter Thiocyanate Extraction, AnalyticaChimica Acta, 209(1988)281-285.

[9] A. Hioki et al., Examination of the EDTATitration of Manganese(II) taking intoConsideration Formation of 1:1 and 1:2Complexes with Eriochrome Black TIndicator, Talanta, 36(1989)1203-1208.

[10] A. Hioki, Precise Coulometric Titration ofAntimony(III) in a Highly Acidic Solution,Analyst, 117(1992)997-1001.

[11] E. Toda et al., Determination of Impuritiesin High-purity Selenium by InductivelyCoupled Plasma Mass Spectrometry afterAcetate-form Anion-exchangeSeparation, Analytica Chimica Acta,333(1996)51-58.

[12] E. Toda and A. Hioki, Determination ofImpurities in High-purity Selenium byInductively Coupled Plasma MassSpectrometry after Matrix Separation withThiourea, Analytical Sciences February,11(1995)115-118.

[13] A. Hioki et al., Accuracy in GravimetricDetermination of Nitrate and Nitrite asNitron Nitrate, Analytical Sciences,6(1990)757-762.

[14] A. Hioki et al., Accuracy in the PreciseCoulometric Titration of Ammonia andAmmonium Ion with Electrogenerated

Hypobromite, Talanta, 38(1991)397-404.

[15] Minutes of the Third Meeting of the CCQMWorking Group on Gas Analysis, held atthe BIPM, Monday 29th and Tuesday 30thNovember 1999.

[16] S. Nakao et al., Intercomparison Tests ofthe NRLM Transfer Standard with thePrimary Standards of NIST, BNM-LNE,OFMET and PTB for Small Mass FlowRates of Nitrogen Gas, Proceedings of theMetrologie '99 Conference, Paris, France,1999.

[17] C. Takahashi et al., Some Problems on theEvaluation of Measurement Uncertaintyin Gas Analysis, CCQM - Workshop onMeasurement Uncertainty/WorkingGroup Meeting on Gas Analysis, 1999.

[18] Special Committee for IntellectualInfrastructure Development Report 2002Revision (in Japanese), Special Committeefor Intellectual InfrastructureDevelopment, 2002.

[19] The International Database for CertifiedReference Materials (COMAR) providedby Federal Institute for Materials Researchand Testing (BAM), http://www.comar.bam.de/

[20] Reference Materials Total InformationServices of Japan (RMinfo) provided byNational Institute of Technology andEvaluation (NITE), http://w w w . r m i n f o . n i t e . g o . j p / e n g l i s h /index.htm

[21] T. Okai et al., Collaborative Analysis of GSJGeochemical Reference Materials, BunsekiKagaku, 51(2002)973-977.

[22] N. Imai et al., 1998 Compilation ofAnalytical Data for Five GSJ ReferenceSamples, Geostandards Newsletter,23(1999)223-250.

[23] Science Council of Japan, Development of

238

Toshiaki Asakai

Reference Materials ConcerningBiotechnology-based Medicines andHuman Healthcares (in Japanese), 2003.

[24] Y. Kayamori et al., Endpoint ColorimetricMethod for Assaying Total Cholesterol inSerum with Cholesterol Dehydrogenase,Clin. Chem., 45 (1999) 2158-2163.

[25] Committee on Blood Gases/Electrolytes,An Investigative Report on theStandardization of Blood ElectrolyteMeasurements Obtained Using DomesticIon Selective Electrode Devices (inJapanese), 1985.

[26] Chemicals Inspection and TestingInstitute, Japan, Preparation andMeasurement Methods of CertifiedPrimary Reference Materials for ISE (in

Japanese), 1986.

[27] Glycohemoglobin StandardizationCommittee Report, J. Japan DiabetesSociety, 37 (1994) 855-864.

[28] Review of KO500 Method and JSCCPractical Standard Method, Abstract fromthe Japan Society of Clinical Chemistry,Kanto District Convention, 2000.

[29] Akira Ono et al., Traceable Measurementsand Data of Thermophysical Properties forSolid Materials : a Review, Meas. Sci.Technol., 12 (2001) 2023-2030.

[30] M. Fujita et al., A Computer NetworkSystem for Mutual Usage of MaterialsInformation (Data-Free-Way), Proc. ofInter. Symp. on Material ChemistryNuclear Env. Mc'96, (1996)875-884.

239

The Reference Materials Programme at the Australian National Measurement Institute

1. Introduction

The chemical standards programme of theAustralian National Measurement Institute(NMI) has grown from its long history ofinvolvement with analytical chemistry throughits forebears, the laboratories of the New SouthWales (later Australian) Customs Department(1896) and the Australian GovernmentAnalytical Laboratories (AGAL), founded in1973. In both the supply of reference materialsto Australian analytical chemists became a


The Reference Materials Programme at the AustralianNational Measurement Institute

L.M. BESLEYNational Measurement InstitutePymble, NSW 2073, Australia


[Received : 15.07.2004]

Abstract

The National Measurement Institute (NMI) is Australia's major source of reference materials asstandards for qualitative and quantitative analytical chemistry. The Australian programme hasconcentrated on the production of pure-substance organic certified reference materials (CRMs),with particular emphasis on steroids, forensic drugs and agricultural and veterinary chemicals.Some matrix CRMs are also being produced, particularly in the area of gas mixtures. The techniqueused for all CRMs is a multi-method one, with the employment of primary measurement or productiontechniques where possible to provide traceability of the material property values to the internationalsystem of units. The assignment of property values to the CRMs is reviewed by a panel of externalexperts before the materials are certified. NMI is accredited against ISO Guide 34 as a referencematerials producer. The NMI reference materials programme has resulted in some 200 CRMs beingavailable.


significant activity. In 1997 AGAL set up aspecialist chemical metrology group entitled theNational Analytical Reference Laboratory(NARL), part of the role of which was todevelop and maintain a suite of referencematerials for the Australian nation. This rolewas given great momentum by the decision tocommission NARL to develop CertifiedReference Materials (CRMs) for the testing ofathletes for banned drugs at the OlympicGames in Sydney in 2000. In recent times, afurther organisational development has takenplace. In July 2004, AGAL combined with the

240

L.M. Besley

National Measurement Laboratory (NML) andthe National Standards Commission to formthe NMI. NML had its own programme toproduce gas composition standards. Thechemical metrology programmes of AGAL andNML, including those for reference materials,have been incorporated as a vital part of thenew NMI's functions.

2. Scope of Activities

In theory NMI is charged through nationallegislation with the responsibility to providenational Australian standards for all areas ofmeasurement, including the many and variedfields of analytical chemistry. In practice,however, this is an impossible task because ofthe virtually infinite combinations of analytesand matrices for which chemical analyses arerequired, and the definitely finite nature ofresources available to the NMI. Moreover,reference materials are in general relativelyeasily transported so that where available theycan be sourced from suppliers outside Australiawithout undue inconvenience. Therefore NMIis focussing its activities in reference materialson areas where the following factors apply:

• accuracy and traceability of measurementare particularly important to the Australianeconomy and/or the Australiancommunity, and

• mechanisms exist in Australia whereby theadvantages to be gained by having referencematerials available can be transferred intothe community,

and one or more of the following are true :

• there are no alternative national orinternational suppliers,

• transport or other issues make theavailability of CRMs from those suppliersdifficult or impractical.

At the present time, this has meant that NMI isconcentrating on producing CRMs for the fieldsof :

• agricultural and veterinary chemicals,

• forensic drugs,

• steroids, and

• gas composition.

There are two basic types of referencematerials needed by the analytical chemistrycommunity. The first type comprises pure-substance reference materials that consist of asingle major component and are accompaniedby a certified statement of purity. These CRMsare used in two ways, to provide unequivocalidentification of a chemical species, and to actas the source material to make up standards ofknown concentration for the calibration ofquantitative measuring equipment. The secondtype comprises matrix reference materials inwhich the concentration of an analyte or anumber of analytes within a particular matrixis certified to be at stated levels. Such CRMsare used for analytical method validation andfor calibration purposes in quantitativeanalytical chemistry.

In the past, NMI has concentrated almostsolely on producing pure-substance CRMs,largely because this was where the need wasclearly identified and because the resourcesavailable to produce them were within thebounds of the NMI's finances. Thus theoverwhelming majority of the NMI's catalogueconsists of these materials. However, in recenttimes the demand for matrix CRMs has becomemore insistent and despite the very high costof doing so, NMI is now also undertaking someactivity in this area. Notable amongst thesematrix CRMs are gas composition standardsin the areas of petroleum natural gas mixtures,urban air pollutants and greenhouse gasmixtures.

In addition to its activities in producing andcharacterising CRMs, NMI maintains the so-called "National Reference Collection" ofagricultural and veterinary chemicals.

241


Materials in this collection are not characterisedby NMI and are not CRMs. However, they doact as valuable reference materials (RMs) toenable the qualitative identification ofunknown chemicals in plants and animals ofinterest to Australian primary industries. TheRMs are sourced from suppliers who arerequired by Australian law to lodge sampleswith NMI as part of the registration processmandated before such materials can be usedin Australia.

Other lower-grade RMs are produced asby-products of NMI's chemical proficiencytesting (PT) activities. NMI offers clients PTservices in a number of fields, including analysesof illicit drugs, pesticides in vegetables and soil,petroleum hydrocarbons in soil and water, andtrace metals in cereals. The test samplesproduced for these studies are extremely wellcharacterised, both by several NMI methods,and by the consensus of values returned by thePT participants. Therefore at the end of anyparticular scheme what remains of the samplematerial is available for sale to users as a RM.Because the studies of homogeneity andstability undertaken by NMI for these materialsare limited, and because normally a primarymethod is not used for their characterisation,they cannot qualify as CRMs but can have avaluable role to play in analytical laboratoryquality processes.

All RMs and CRMs held by NMI areavailable for sale from NMI both within andoutside Australia, though the distribution ofsome controlled substances in the forensic andsporting drugs areas is tightly proscribedthrough the use of permits.

3. The NMI Reference Materials Resource

NMI has a staff of about 12 in the referencematerials area, supported by a staff of about 8in the primary methods group that suppliessome of the characterisation services andanother 5 in the proficiency testing group thatgenerates some lower-level RMs. The reference

materials group has skills in organic synthesis,gravimetric preparation and chemical analysis,thus providing a complete skillset for theproduction of CRMs in the areas covered. Theyare supported by analytical equipment thatincludes gas chromatographs, high-performance liquid chromatographs, massspectrometers, thermal analysers, differentialscanning calorimeters and high-precisionbalances, and by a range of equipment to assistin material synthesis and sample preparation.Some (a minor proportion) of the synthesis andanalytical services are outsourced to externalsuppliers

The activity is paid for largely by directAustralian government funding, though therecovery of some (and for some CRMs, all) ofthe cost is achieved through revenue derivedfrom the sale of the materials to clients. Inaddition, some of the CRMs are producedunder contract to agencies external to NMI andtheir development and production are fullyfunded by those agencies.

4. Accreditation

The NMI reference materials facility isaccredited by the Australian NationalAssociation of Testing Authorities (NATA)against ISO Guide 34 as a reference materialsproducer. This accreditation is held for pure-substance organic CRM production and hasbeen in place since 1998. This accreditationwas sought partly to bolster NMI's own internalquality procedures, and partly to give ourclients additional confidence in our capability.

5. Certification Methods Used

5.1. Pure-substance CRMs

For pure-substance CRMs, we use acombination of what are known as the "direct"and "indirect" approaches. The details of thisapproach have been given in several recentpublications [1,2]. The major method is the"indirect" one, in which the amount of

242

L.M. Besley

substance fraction of every impurity ismeasured by a variety of different methods, themost important of which is gaschromatography in combination with a flameionisation detector (GC-FID). These separateimpurity amount of substance fractions are thenadded together and the result is subtracted from1 to give an overall purity specification for themajority component.

The equation for the amount of substancefraction of the major component, Xpurity, istherefore :

Xpurity = 1-(XDet+XNR+XND+XOther) (1)

where :

XDet = amount of substance fraction of theimpurities directly identified andquantified with GC-FID,

XNR = estimated amount of substancefraction of impurities that could bedetected by GC-FID but were notresolved from the active compound bythe chromatographic process,

XND = estimated amount of substancefraction of impurities whoseconcentration is below the detectionlimit of the GC-FID apparatus,

XOther = amount of substance fraction of otherimpurities not able to be quantified byGC-FID but quantified by othermethods.

The "indirect" result is confirmed with the"direct" approach, in which the total level ofimpurities is evaluated independently by usingat least two assay techniques, chosen for theirsuitability for the material in question. Theresult is a "direct" value for the total impuritylevel. If this is consistent with the sum of thevarious impurity terms explored above, withinthe limits of the respective calculateduncertainties, the "indirect" values are assumedto be the definitive purity measurements.

If the data from the "direct" and "indirect"methods do not agree, an attempt is made to

identify the causes of the disagreement andcorrect the results appropriately. If thedifferences cannot be resolved, an unrecognisedbias is assumed to be present in at least one ofthe results and a weighted mean of the data istaken for the certification value.

The certified purity result is expressed asan amount of substance fraction, or convertedto a mass percentage. The standarduncertainty associated with this value iscalculated in the usual way by the proceduresof the ISO-GUM, using as input the estimateduncertainties of each of the componentprocesses.

For every pure-substance CRM, a panel ofindependent experts drawn from Australia'sacademic community examines the assignedpurity value and the traceability of theidentification of the chemical speciesassignment. Only after this independentreview are CRMs released for distribution.

5.2. Gas Mixture CRMs

The gas mixture CRMs produced by NMIare produced by a primary method, that ofgravimetry in which the different componentsof the mixture are weighed into the containingvessel. This process in carried out in one stagefor gas concentrations greater than about 0.001mole/mole, and in multiple dilution stages forconcentrations below that level. Because theresults of all the weighings have directtraceability to the national standards of mass,no further characterisation of the mixturesproduced by this technique is strictly necessary.However, a verification step is carried out bymeans of gas chromatography to ensure thatthe gravimetric results are consistent withgravimetric results produced for other mixtures.

The uncertainty of these gravimetriccomposition values is very low. For mixtureswhose components pose no problems in termsof adsorption to, or desorption from, thecontainer walls, the uncertainty is typically of

243


the order of 0.01 to 0.05% of the gasconcentration value.

5.3. Other Matrix CRMs

One other matrix CRM has been produced,a suite of 9 organic pesticides in a matrix ofpureed tomato, and another is in preparation,of a steroid metabolite in a matrix of humanurine. Such matrix CRMs are the result ofmajor effort because, as well as the methoddevelopment, they involve lengthy andexpensive studies to demonstrate homogeneityand time-dependent stability.

The fundamental technique used whereverpossible in their characterisation is that ofexact-matching isotope dilution massspectrometry. This is a primary method forwhich NMI's approach has been described indetail elsewhere [3] and will not be discussedfurther here.

In one instance, the NMI facility has beenused to characterise the property values of amatrix material produced elsewhere, thusconverting it into a CRM. This particularexample is for aqueous ethanol standardsproduced by the Australian police authoritiesand used as the legal basis for their testing ofautomotive drivers for illegal levels of alcohol.Opportunities are being sought to utilise theNMI facility in a similar way for other purposes.

6. Conclusion

The Australian NMI program for referencematerials is highly targetted in specific areasrelevant to Australia's needs and where theskillset resident in NMI is particularly

appropriate. Great care is taken to ensure thatthe certification process is of the highest qualityby the utilisation of primary methods, multiplemethods, accreditation processes, and externalreview. The result is a reference materialsprogramme that is vigorous, supportsAustralia's national measurementinfrastructure, generates a significant cash flowfor NMI and has a strong internationalreputation. The programme will continue toexpand into new areas of need and to be mademore interactive with NMI's other activities inorganic and inorganic analysis, sports druganalysis, forensic drug analysis and proficiencytesting.

References

[1] B. King and S. Westwood, GC-FID as aPrimary Method for Establishing thePurity of Organic CRMs Used for Drugsin Sport Analysis, Fresenius J. Anal. Chem,370 (2001) 194.

[2] L. Besley and S. Westwood, Chapter 2 APractical Approach to Certifying thePurity of Single-Component ReferenceMaterials in Metrology in Chemistry:Considerations, Approaches andDevelopments on the Applicability ofMethods of "higher order", ComptesRendus (2004, in press).

[3] L.G. Mackay, C.P. Taylor, R.B. Myors, R.Hearn and B. King, High AccuracyAnalysis by Isotope Dilution MassSpectrometry Using an Iterative ExactMatching Approach, Accred. Qual.Assur., 8 (2003) 191-194.

244

L.M. Besley

245

Certification of In-house Reference Materials

1. Introduction

In-house reference materials (IHRMs) arereference materials (RMs) prepared by users "inhouse" for their own purposes. There are guidesfor laboratories developing IHRMs [1, 2].Sometimes the reason for the development isthe absence of suitable certified referencematerials (CRMs) in the market. Anotherreason is saving certain CRMs expensive forthe laboratory. Moreover, selection of thecorresponding (suitable, match, adequate)CRM having the composition and physico-chemical properties as those of the sampleunder analysis is often a knotty problem. Theguides for RM selection and use [3-7] suggest© Metrology Society of India, All rights reserved.


ILYA KUSELMANNational Physical Laboratory of Israel

Givat Ram, Jerusalem 91904, Israele-mail: [email protected]

[Received : 02.05.2004]

Abstract

Certification of in-house reference materials (IHRM) is discussed. It is emphasized that requirementsto simplicity of an IHRM certification procedure in an analytical laboratory should be harmonizedwith requirements to uncertainty of the property value carried by the IHRM and to its traceability.Three topics in the certification framework are reviewed: 1) a score of the adequacy of a certifiedreference material (CRM) to an IHRM under development, 2) usage of an adequate CRM forcharacterization of an IHRM with traceable property values, and 3) application of an inadequateCRM to achieve traceability of an IHRM property value.

Key words : In-house reference materials, Certification, Comparative approach, Traceability andAdequacy.


an algorithm of assessing RM suitability,including the definition of the measurand /analyte, measurement / concentration range,matrix match and potential interferences, unitsize, homogeneity and stability, procedures forassignment of the RM certified value and itsuncertainty. However, development of a scorefor quantitative evaluation of RM adequacy tothe sample under analysis has been proposedonly recently [8].

According to the metrological qualification[9], IHRMs are working measurementstandards that form the bottom of ametrological pyramid. Therefore, IHRMsshould be traceable to CRMs and SI unitsplaying the role of secondary and primary

246

Ilya Kuselman

measurement standards placed at the pyramidtop [10-12]. If an IHRM is compared to thecorresponding CRM, the latter is a referencemeasurement standard. Naturally, theuncertainty of a property value carried by theCRM as a reference standard is lower than thatof the IHRM.

IHRM certification is the complete processof obtaining the property values and theiruncertainties, which includes homogeneitytesting, stability testing and IHRMcharacterization, as required for any RM [10,13]. It is clear that requirements to simplicityof an IHRM certification procedure in anyanalytical laboratory should be harmonizedwith requirements to uncertainty of theproperty value carried by the IHRM and to itstraceability. Such harmonization can beachieved using a comparative approach toIHRM characterization, developed recently forcases when an adequate CRM is found in themarket [14-16]. It is shown also that inadequateCRMs are sometimes also applicable forestablishing traceability of an IHRM propertyvalue [17, 18].

The present paper is a review of the newabove mentioned proposals initiated at theNational Physical Laboratory of Israel (INPL)for: 1) evaluation of a CRM adequacy to anIHRM, 2) IHRM characterization using anadequate CRM, and 3) application of aninadequate CRM for IHRM characterization.

2. Evaluation of CRM Adequacy

To select a necessary CRM, a laboratorydeveloping an IHRM compares expectedcomposition and physico-chemical parametersof the IHRM and those of CRMs of the samenature, available in the market. One can sayintuitively that 100% adequacy is achievedwhen all the IHRM and the CRMcharacteristics coincide entirely. In the otherextreme case, the adequacy is totally absent(0%) when the IHRM and the CRM aredifferent substances or materials and / or when

the analyte is absent in the CRM. In non-extreme cases, the laboratory considers a CRMto be more adequate if the CRM compositionand properties are as close as possible to theones expected for the IHRM. Suchunderstanding of the adequacy can be reflectedin the following score [8] :

A = 100

iani,IHRM i,CRM

i,IHRM i,CRMi

min(C ,C )

max(C ,C )

∏ ,% (1)

where Õ is the symbol of multiplication; i =1, 2, …, n is the number of a component or of aphysico-chemical parameter; Ci,IHRM andCi,CRM are the concentrations of the i-thcomponent or the values of the i-th physico-chemical parameter for the IHRM and for theCRM, respectively; min(Ci,IHRM, Ci,CRM) is thesmallest and max(Ci,IHRM, Ci,CRM) is the largestvalues from Ci,IHRM and Ci,CRM; ai is thesensitivity coefficient: for analytes ai = 1, formatrix components or parameters notinterfering with the analysis ai = 0, for othersthe coefficient value should be defined in therange of 0 < ai £ 1 based on the knowledge ofthe analytical process.

It is not important here if Ci,IHRM is thesmallest and Ci,CRM the largest, or vice versa.If only one component (analyte) is considered,n = 1, a1 = 1 and the score is equal to the ratioR1 = min (C1,IHRM, C1,CRM) / max (C1,IHRM,C1,CRM) in %, i.e. A = 100R1. Since thecomponent concentrations in IHRM undercharacterization and in CRM should not differby more than a factor of two [14], theacceptable values of the adequacy score in thiscase is A ³ (100/2) = 50%.

If the i-th component is absent in the IHRMor in the CRM, min(Ci,IHRM, Ci,CRM) = 0, theratio Ri = min (Ci,IHRM, Ci,CRM)/max (Ci,IHRM,Ci,CRM) = 0 and the score A = 0 also.

If Ci,IHRM = Ci,CRM, the ratio Ri = 1.Therefore, when the certain componentconcentrations or physico-chemical properties

247


of the CRM and the IHRM are the same (Ri =1), they can be eliminated from formula (1) asnot influencing the score A value. If all n ratiovalues Ri =1, i = 1, 2, … , n, the score A =100%.

Since most often Ri < 1, the larger numbern is the smaller A value. The explanation isobvious: to reach CRM adequacy to an IHRMhaving more complicated composition andproperties is more difficult. For example, if ncomponent concentrations in IHRM undercharacterization and in CRM should not differby more than a factor of two as required in[14], R1 = R2 = … = Ri = … = Rn = 0.5, and at ai=1 the acceptable score values are A ³ 100 ×Ri

n = 100 × 0.5n, %. As shown above, for n = 1A ³ 50%, but for n = 10 significantly less valuesA ³ 0.10% are acceptable. However, for acertain analytical task CRMs of interest havethe same number n of certified components andphysico-chemical parameters. Therefore, theselection of the most adequate CRM for thistask is performed by comparison of A valuesfor the CRMs at the same n.

For example, for certification of an IHRMof coal fly ashes for the content of tencomponents (aluminium, calcium, iron,potassium, magnesium, sodium, phosphorous,silicon, sulphur and titanium) the following

CRMs developed by NIST and named"standard reference materials" (SRMs) can beused: SRMs 2689, 2690 and 2691 [19]. Expectedcomposition of the IHRM under characteri-zation, certified values of the SRMs, Ri and Avalues are shown in Table 1. Since all thecomponents are analytes (ai = 1, n = 10), andSRM 2689 is not certified for sulphurdetermination, the adequacy of this CRM is A= 0. The other two SRMs are adequate, as theiradequacy score values are A > 0.10 %.However, for SRM 2691 A = 3.7%, while forSRM 2690 it is only A = 1.2 %. Therefore, SRM2691 is the most preferable CRM in this case.

If an IHRM is developed as a blank, i.e.absence of the analyte is a part of the analyticaltask, multiplying ( Õ ) in formula (1) is replacedby averaging (å /n).

Thus, the score A = 0 - 100% and can bedefined in every case as accurately as it ispossible in view of the prior informationavailable on the composition and properties ofthe developed IHRM and on the analyticalprocess. More details of the score calculations,including situations when concentrations orphysico-chemical properties of components aregiven as ranges, as well as additional examples,are described in [8].

Table 1Evaluation of adequacy of SRM Nos. 2689 - 2691 to an IHRM of coal fly ashes

i Analyte Ci,IHRM SRM 2689 SRM 2690 SRM 2691

Ci,CRM Ri Ci,CRM Ri Ci,CRM Ri

1 Aluminium 11 12.94 0.85 12.35 0.89 9.81 0.892 Calcium 11 2.18 0.20 5.71 0.52 18.45 0.603 Iron (total) 4 9.32 0.43 3.57 0.89 4.42 0.904 Potassium 0.6 2.20 0.27 1.04 0.58 0.34 0.575 Magnesium 2 0.61 0.31 1.53 0.77 3.12 0.646 Sodium 0.6 0.25 0.42 0.24 0.40 1.09 0.557 Phosphorus 0.5 0.10 0.20 0.52 0.96 0.51 0.988 Silicon 20 24.06 0.83 25.85 0.77 16.83 0.849 Sulphur 0.5 0 0.00 0.15 0.30 0.83 0.6010 Titanium 0.7 0.75 0.93 0.52 0.74 0.9 0.78n=10 A 0.0 1.2 3.7

248

Ilya Kuselman

3. Comparative Approach

A comparative approach to IHRMcharacterization is based on transmission of themeasurement information from an adequateCRM to the IHRM [14]. A traceability chain ofthe value carried by the IHRM to the valuecarried by the adequate CRM is helpful in sucha case [20]. The chain is realized when testportions in pairs - one of the IHRM and one ofthe CRM - are analysed by the same analystand method in the same laboratory andconditions, each pair practicallysimultaneously. The concentration of the IHRMcomponent under characterization CIHRM iscompared with its certified concentrationCCRM in the CRM, using the differences in theanalysis results Ej = (CIHRM-j - CCRM-j) for allpairs: j = 1, 2, …, m (m ³ 20). From thiscomparison, the characterized value iscalculated as

CIHRM=CCRM+Eavg , where Eavg=S Ej /m. (2)

Obviously, even if CIHRM-j and CCRM-j havean additive systematic error, Ej is free from thiserror by definition. Additivity of bias is areasonable approximation for nearly identicalmatrices: the multiplicative bias component isassumed as negligible at similar concentrationsof the analyte in the CRM adequate to theIHRM. Therefore, Eavg and CIHRM by formula(2) are also unbiased. So, the certificationstandard uncertainty [21] is

u(CIHRM)=[u2(CCRM)+u2(Eavg)]½, (3)

where u2(Eavg)=S(Ej - Eavg)2/(m-1)m, (4)

and u (CCRM) is the standard uncertaintyof the value carried by the CRM. If the CRM isnot only the most adequate according toformula (1), but also corresponds to theuncertainty criteria of the guidelines [5] assatisfactory or acceptable, i.e. if u(CIHRM)/u(CCRM) > 4, the uncertainty of the valuecarried by the CRM is negligible. Otherwise, itshould be taken into account according to

formula (3). The expanded uncertainty of theIHRM assigned value is

UIHRM = k×u(CIHRM), (5)

where k is a coverage factor [21]. The kvalue is calculated as the Student's coefficientwith m - 1 degrees of freedom, and achieves 2at m ³ 20.

It should be noted that, according toformulas (2) - (5), UIHRM value includeshomogeneity uncertainties of both the IHRMand the CRM, since Ej deviations from Eavg arecaused not only by the measurementuncertainties, but also by fluctuations of theanalyte concentrations in j-th test portions ofthe IHRM and the CRM. The stabilitycomponent of uncertainty UIHRM is includedinto u (CCRM). Since adequate CRM and IHRMhave similar matrixes and close chemicalcompositions, their stability characteristics aresupposed to be identical unless any specificopposite information exists.

Two applications of the approach arediscussed below. One of them is developmentof pH IHRMs traceable to the correspondingNIST pH standards [15]. As the referencemeasurement standards, the following buffersprepared from the NIST SRMs with thestandard pH uncertainty 0.0025 were used: 1)saturated solution of potassium hydrogentartrate (SRM 188), pH = 3.557 at 25 °C; 2)potassium dihydrogen phosphate (SRM 186-Ie) and disodium hydrogen phosphate (SRM186-IIe) 0.025 molal solution, pH = 6.863 at 25°C; 3) 0.01 molal solution of sodium tetraboratedecahydrate (SRM 187c), pH = 9.180 at 25 °C;and 4) sodium bicarbonate (SRM 191a) andsodium carbonate (SRM 192a) 0.025 molalsolution, pH = 10.011 at 25 °C. Other fourbuffers of the same composition were preparedfrom the corresponding commercial reagentsproduced by BDH, England, and used asIHRMs. Homogeneity and stability of thesesalts, taken into account in the SRM

249


certification [22], are sufficient during 2-5 yearsand thus were ignored as sources of theuncertainty components in formula (3).

The same 0.05 molal potassium dihydrogencitrate solution with pH = 3.776 at 25 °C,recommended by NIST in the capacity of astandard material, was used as the fifthcommon point for both sets of calibrations"electromotive force (e.m.f.) vs. pH", based onthe reference measurement standards and onthe IHRMs.

Therefore, the experiment was designed tomeasure the e.m.f. of the test portions (in pairs)of the four kinds of buffers prepared using thestandards and IHRMs, as well as the e.m.f. ofthe dihydrogen citrate solution, i.e. 9measurements for each j =1, 2, ...., m. Theresults of these measurements allowed tocompute the j-th calibration curve "e.m.f. vs.pHSRM" and to calculate the correspondingpairs pHSRM-j and pHIHRM-j .

It has been shown that while themeasurements were being performed, astatistically detectable temporal drift of themeasurement system took place. This findingrequired limiting the lifetime of the buffersolutions down to 7-10 days. The drift did nothinder the extraction of the necessarymeasurement information by the proposedcomparative approach, since the experimentdesign provides pH measurements in testportions of each pair of the reference standardand in-house material in the same conditions.Therefore, only the differences between themeasurement results are used in furthercalculations.

The certified pH values of the IHRMs werefound to be close to the SRMs' correspondingvalues. The pH uncertainties of the IHRMs areonly 20% larger than the correspondinguncertainties of the NIST pH standards.

Another application of the comparativeapproach was used for development of an

IHRM for mometasone furoate assay [16]. Thetraceability of the value carried by the IHRMwas established to the value carried by UnitedStates Pharmacopoeia Reference Standard(USP RS) having the highest metrological statusin the field. Since the European PharmacopoeiaReference Standard (EP RS) is not certified formometasone furoate assay, it was alsocharacterized in respect to the assay value (onthe IHRM level). Thus, the experiment wasdesigned to measure practically simultaneouslyUV absorbance of the test portions of the twopairs: IHRM - USP RS and USP RS - EP RS. Tominimize the experiment cost, these pairs weretransformed into a set of three test portions : 1)IHRM ® 2) USP RS ® 3) EP RS, i.e. only threemeasurements for each j =1, 2, ...., m wereplanned. There are no data on the uncertaintyu (CUSP RS), and it was assumed in the study tobe equal to u (Eavg). Therefore, formula (3) wassimplified: u (CIHRM) = 1.4142 u (Eavg). Thesituation in general in the pharmaceuticalindustry, when the traceability ofmeasurement/analytical results to certifiedvalues of pharmacopoeial reference standardsis required without evaluating theiruncertainties, is discussed in [23].

A bias of the experimental average assayvalue for mometasone furoate USP RS from itscertified value was found. This fact shows thatthe requirement of the EP analytical methodused to compare the absorbance obtained for atest portion with the specific value (481) limitsthe method's capabilities. However, thecomparative approach provides the correctcharacterization of the IHRM even in thepresence of the bias, since the experimentdesign ensures the same conditions forabsorbance measurements of each pair of thetest portions (of the reference standard and ofthe IHRM). The certified assay values of theIHRM and EP RS for mometasone furoate assaywere found to be very close to the USP standard'corresponding value.

The approach can be applied also for the

250

Ilya Kuselman

proficiency testing objectives [17].

4. IHRM Characterization using anInadequate CRM

When adequate CRMs are not available, forexample, for analysis of unstable aqueoussystems, IHRMs can be preparedgravimetrically using the synthesis of thecorresponding matrix and pure substances orinadequate non-aqueous CRMs (for example,herbicide mixture in acetonitrile as traces in asynthetic water IHRM) [17]. The assigned valueCIHRM of an analyte concentration in a syntheticIHRM and its expanded uncertainty UIHRM arecalculated taking into account: measuredmasses mw and mCRM of the water and theCRM, respectively; mass measurementstandard uncertainties u (mw) and u (mCRM);and uncertainty u (CCRM) of the analyteconcentration certified in the CRM; by formulas

CIHRM = CCRM [mCRM /(mCRM+mw)], (6)

and

UIHRM = k{[u2(CCRM)/C2CRM + u2(mCRM)/

m2CRM + (u2(mCRM) + u2(mw))/(mCRM +

mw)2]C2IHRM + u2

hom}0.5, (7)

where uhom is the standard uncertainty of theIHRM homogeneity. The homogeneity can beevaluated by analysis of the test portionssampled after IHRM preparation (mixing) atthe beginning, in the middle and at the end ofthe IHRM removal from the mixing containerinto laboratory bottles. Value UIHRM does notinclude a stability component, since syntheticwater IHRM should be prepared and used inconditions (temperature, time etc.) required bythe Standard Methods [24], in which thesample degradation is negligible. If a puresubstance is used as a CRM, CCRM stands forits purity, while u (CCRM) is the standarduncertainty of the purity value.

Another use of an inadequate CRM is basedon traceable quantitative elemental analysisand qualitative information on purity /

degradation of the substance whoseconcentration in the IHRM is undercharacterization. In this way, IHRMs fordetermination of inorganic polysulfides inwater have been developed [18]. Thedetermination includes the polysulfides'derivatization with a methylation agentfollowed by GC/MS or HPLC analysis of thedifunctionalized polysulfides. Therefore, theIHRMs are synthesized in the form ofdimethylated polysulfides containing from fourto eight atoms of sulphur.

The composition of the compounds wasconfirmed by NMR and by the dependence ofthe HPLC retention time of thedimethylpolysulfides on the number of sulphuratoms in the molecule. Stability of the IHRMsis studied by HPLC with UV detection at 230nm. Carbon tetrachloride solutions of thedimethylpolysulfides are stable at -20 ºC for twoweeks, while their solutions in a mixture 1:1 ofacetonitrile and formic acid are stable even at+5 ºC for three weeks. The total sulphurcontent was determined by the IHRMs'oxidation with perchloric acid in high-pressurevessels (bombes), followed by determination ofthe formed sulphate using ICP-AES. Thecertified values of the dimethylpolysulfideconcentrations are in the range of 416 - 3327ppm. The IHRM certified values are traceableto SI kg, since all the test portions wereweighed, and to NIST SRM 682 via the AnionenMulti-Element Standard II from "Merck"containing sulphate ions of 1000 ± 5 ppm thatwas used for the ICP-AES calibration.Traceability of the chromatographic data wasnot important here, as these data were usedonly for identification of the polysulfidedegradation ("yes or no").

5. Traceability to SI

The assumption of the proposedapproaches is that analytical methods used bya laboratory developing IHRMs are validated,chemical measuring instruments are calibrated

251


with traceable reference materials or puresubstances, physical measurement instruments(balances, thermometers and so on) arecalibrated with their corresponding traceablestandards, and measurement uncertainties areevaluated. In other words, the basic principlesof the traceability guide [20] are fulfilled in thelaboratory. Another assumption is that CRMsused for IHRMs certification have the assignedvalues traceable to SI. In these conditions, theCRMs allow establishing traceability of thevalues carried by IHRMs under developmentto SI by the chain "SI ® CRM ® IHRM".

6. Conclusions

• The adequacy of an IHRM underdevelopment to a CRM can be evaluatedusing a score based on the comparison ofIHRM and CRM compositions and physico-chemical parameters that influence theanalytical results. Calculation of such ascore allows to finde the most adequateCRM using prior information on the IHRMand on the analytical method.

• If adequate matrix CRMs are available, thecomparative approach for development ofthe corresponding IHRMs, based onsimultaneous analysis of CRM and IHRMtest portions in pairs, is helpful.

• If adequate matrix CRMs are not available,for example, in analysis of unstable aqueoussystems, a synthetic IHRM can be preparedgravimetrically using inadequate non-aqueous CRMs or pure substances.Another use of an inadequate CRM is basedon traceable quantitative elemental analysisand qualitative information on purity /degradation of the substance whoseconcentration is the value carried by theIHRM under characterization

References

[1] B. Brookman and R. Walker, Guidelinesfor the In-house Production of Reference

Materials, LGC Report, UK, 1997.

[2] J.M. Christensen, Guidelines forPreparation and Certification of ReferenceMaterials for Chemical Analysis inOccupational Health, NORDREF (ISBN:87-7904-010-1), 1998.

[3] B. King (ed.), The Selection and Use ofReference Materials, EA-04/14, 2003.

[4] Uses of Certified Reference Materials, ISOGuide 33, 2nd ed., Geneva, 2000.

[5] Guidelines for the Selection and Use ofCertified Reference Materials, ILAC-G9,1996.

[6] B. King (ed.), The Selection and Use ofReference Materials, A Basic Guide forLaboratories and Accreditation Bodies,EEE/RM/062rev3, 2004.

[7] Valid Analytical Measurement,Homepage. http://www.vam.org.uk,Cited 15 April, 2004.

[8] I. Kuselman, A Priory Evaluation ofAdequacy of Reference Materials, Accred.Qual. Assur., 9(2004).

[9] W. Haesselbarth, Classification ofReference Materials, In : Zschunke A. (ed.),Reference Materials in AnalyticalChemistry, A Guide for Selection and Use,Springer, Berlin (2000) 16-18.

[10] Certification of Reference Materials -General and Statistical Principles, ISOGuide 35, 2nd ed., Geneva, 1989.

[11] Guidelines for the Requirements for theCompetence of Reference MaterialsProducers, ILAC-G12, 2000.

[12] P. De Bievre, Traceability of (values carriedby) Reference Materials, Accred. Qual.Assur., 5 (2000) 224-230.

[13] A.M.H. Van der Veen, T.P.J. Linsinger, H.

252

Ilya Kuselman

Schimmel, A. Lamberty and J. Pauwels,Uncertainty Calculations in theCertification of Reference Materials, 4.Characterization and Certification,Accred. Qual. Assur., 6 (2001) 290-294.

[14] I. Kuselman, A. Weisman and W.Wegscheider, Traceable Property Valuesof In-house Reference Materials, Accred.Qual. Assur., 7 (2002) 122-124.

[15] I. Ekeltchik, E. Kardash-Strochkova andI. Kuselman, In-house pH ReferenceMaterials, Microchimica Acta, 141 (2003)195-199.

[16] A. Weisman, Y. Gafni, M. Vernik and I.Kuselman , In-house Reference Materialsof Mometasone Furoate with TraceableAssay Certified Values, Accred. Qual.Assur., 8 (2003) 263-266.

[17] I. Kuselman and M. Pavlichenko, Designsof Experiment for Proficiency Testing witha Limited Number of Participants, Accred.Qual. Assur., 9(2004).

[18] D. Rizkov, O. Lev, J. Gun, B. Anisimov andI. Kuselman, Development of In-houseReference Materials for Determination ofInorganic Polysulfides in Water, Accred.

Qual. Assur., 9 (2004).

[19] National Institute of Standards andTechnology (2004), Homepage. http://www.nist.gov, Cited 25 April 2004.

[20] Traceability in Chemical Measurement, AGuide to Achieving Comparable Resultsin Chemical Measurements,EURACHEM/CITAC, Teddington, 2003.

[21] Quantifying Uncertainty in AnalyticalMeasurement, EURACHEM/CITACGuide, 2nd edn, Teddington, 2000.

[22] Y.C. Wu, W.F. Koch and R.A. Durst,Standard Reference Materials,Standardization of pH Measurements,NBS Special publication 260-53,Washington, 1988.

[23] I. Kuselman, A. Weisman and W.Wegscheider, Traceability withoutUncertainty : Current Situation inPharmaceutical Industry, Accred. Qual.Assur., 8 (2003) 530-531.

[24] Standard Methods for the Examination ofWater and Wastewater, Ed. by L.S.Clesceri, A.E. Greenberg and A.D. Eaton,20th edn., United Book Press Inc.,Maryland, USA, 1998.

253

Correlation in Chemical and Other Measurements

1. General Principles

As a general principle, two quantities X andY (more specifically, their estimates obtainedby measurement) will be correlated if they havean input parameter in common, and if the sameestimate of that input parameter is used inestimating the values of X and Y. Then errorsin X and Y due to an error in the joint inputparameter are no longer independent, givingrise to a covariance u(X,Y) besides the standarduncertainties u(X), u(Y). This covariance hasto be accounted for in any joint application ofthe estimates obtained for X and Y, i.e. if theyare used to estimate another quantity Z. Firstand foremost, the covariance between X and Yhas to be included in the uncertainty budgetfor the derived quantity Z, where this



WERNER HAESSELBARTH and WOLFRAM BREMSERDepartment of Analytical Chemistry and Reference materialsFederal Institute for Materials Research and Testing (BAM )

Referat I.01, 12200 Berlin, Germanye-mail: [email protected]

[Received : 24.09.2004]

Abstract

The intention of this note is to explain the general principles how correlations in measurement ariseand how they are handled in uncertainty budgets, and to point out some typical cases wherecorrelations contribute significantly to the results of chemical measurements, in particular theiruncertainty. The measurement issues considered are of generic nature, and most of them are notrestricted to the field of chemical measurements.


contribution may effect a dramatic increase ordecrease. In addition, the procedure forestimating Z from X and Y may have to beamended to account for correlation between Xand Y (e.g. when using an uncertainty-weighted average), but this will often be a minoreffect.

For the purpose of expressing theseprinciples by simple equations, let us assumethat the quantity X is a function of twoindependent input quantities A and C.Similarly, let Y be a function of twoindependent input quantities B and D, whereC = D while A and B are independent. Thenaccording to the basic law of uncertaintypropagation [1, 2] the variances u2(X) andu2(Y), i.e. the squared standard uncertaintiesare given by

254

Werner Haesselbarth and Wolfram Bremser

∂ ∂ = + ∂ ∂

2 22 2 2X X

u (X) u (A) u (C)A C

(1)

(C)uCY

(B)uBY

(Y)u 22

22

2

∂∂+

∂∂= (2)

These variances are complemented by thecovariance u(X,Y), expressing the correlationof errors in X and Y due to an error in C.

(C)uCY

CX

Y)u(X, 2⋅

∂∂

∂∂= (3)

In case of several mutually independentinput quantities Ai, Bj and Ck the terms in theequations above are replaced by sums ofanalogous terms.

Alternatively, the correlation between X andY may be expressed by the correlationcoefficient r(X,Y), which is obtained bystandardizing the covariance using thecorresponding standard uncertainties.

( ))Y(u)X(u

Y,XuY)r(X,

⋅= (4)

Correlation coefficients are restricted tovalues between +1 and -1, where positive andnegative values express positive and negativecorrelation, respectively. For uncorrelatedquantities the correlation coefficient is zero.

Considering now a quantity Z whichdepends on X and Y, the variance u2(Z) isobtained as

Zu(X,Y)

Y

∂ ∂ ∂ ∂ = + + ⋅ ∂ ∂ ∂ ∂

2

2 22 2

u (Z)

Z Z Zu (X) u (Y) 2

X Y X (5)

Introducing a shorthand notation foruncertainty components*), where u(Z½X) = (¶Z/¶X)u(X) and u(Z½Y) = (¶Z/¶Y)u(Y) denote thecomponents of uncertainty u(Z) due to source Xand Y, respectively, the uncertainty budget

according to eq. (5) may be expressed as)Y Z(u)X Z(u)Y,X(r2)Y Z(u)X Z(u(Z)u 222 ⋅⋅++= (6)

The utmost level of complexity inuncertainty propagation occurs in jointlyhandling several quantities depending on acommon set of correlated input parameters.Then covariances occur on both sides - inputand output - of the uncertainty budget. For asimple setting, let us consider another quantityW depending on X and Y. Then the varianceu2(W) is obtained in complete analogy with eq.(5) or (6). However, there is also a covarianceu(Z,W) given by

2Z W Z Wu (Y)

Z W Z W u(X,Y)

∂ ∂ ∂ ∂ = ⋅ + ⋅ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ + + ⋅ ∂ ∂ ∂ ∂

2u(Z,W) u (X)X X Y Y

X Y Y X

(7)

Again using uncertainty components andcorrelation coefficients, eq. (7) may be re-written as follows

) Y W(u)Y Z(u)X W(u)X Z(uu(W)u(Z)W)r(Z, ×+×=××

u(Z X) u(W Y) u(Z Y) u(W X) r(X,Y)+ ⋅ + ⋅ (8)

Eqns. (6) and (8) are convenient fornumerical calculations, using the finite-difference approximation of uncertaintycomponents, as follows :

−

+≈

∂∂

2u(X)

-XZ2

u(X)XZu(X)

XZ

(9)

Using the equations above, uncertaintiesand correlations associated with analyticalresults may (i) be traced back to the uncertaintyof (hopefully uncorrelated) primary data, and(ii) be propagated to data derived from theseanalytical results.

Covariances (or correlation coefficients) arerequired as complements of variances to makeuncertainty budgets complete and consistent.Ref. [3] gives a nice example from the field of

*) Note that the uncertainty components can have anegative algebraic sign.

255


length measurements, where two equivalentmeasurement arrangements give differentuncertainty estimates, when correlation isoverlooked. The example starts from threegauge blocks of lenghts l1, l2, l3, all with thesame standard uncertainty u(l), and considersdifferent combinations as follows: a = l1 - l2, b= l1 + l3, c = l2 + l3, which then all have astandard uncertainty of Ö2´ u(l). However,combination c can also be expressed as c = b -a, for which uncertainty propagationaccording to u2(c ) = u2(b) + u2(a) gives u(c) =2u(l), in contradiction to the previous result.This inconsistency is due to the fact that b anda are correlated, having l1 in common. Thiscorrelation was omitted in the uncertaintybudget for the difference b - a. The completeuncertainty budget reads u2(c) = u2(b) + u2(a) -2u(a,b). Using eq. (3), the covariance is obtainedas u(a,b) = -u2(l), which leads to the correctresult for u(c).

The example above could lead to theconclusion that by using appropriate inputquantities, accounting for correlation can beavoided. In general the primary data to whichthe result of an analytical measurement can betraced back were determined independentlyand therefore are uncorrelated. However,tracing back that far will often be impractical(when the number of primary data is large andthe traceability network is complex) or evenimpossible (when the primary data are notavailable). In addition, when specifyinguncertainty for a set of analytical data havingsignificant uncertainty sources in common,there is no practical alternative to evaluatingand including relevant covariances orcorrelation coefficients. Otherwise, the supplierof the data would have to specify the completehistory and uncertainty budget of each datum,enabling the user to trace back the uncertaintyof subsequent results, obtained using thesupplied data, to their primary input. This willbe impractical in most cases.

As a final remark, it may happen that two

quantities are known to be correlated, butinformation for tracing back to relevantcommon input uncertainties is lacking. Thenin principle covariances or correlationcoefficients could be determined using a "type-A procedure" in the sense of ref. [1]: by statisticalanalysis of data series where both quantitiesare measured simultaneously at appropriatereproducibility conditions, i.e. conditions whererelevant input parameters are varied accordingto their uncertainty. However, reliableestimation of covariances or correlationcoefficients requires large data sets. Thereforeit will often be more beneficial to useuncertainty propagation with rough estimatesof missing ingredients instead of seeminglyaccurate statistical data based on fewmeasurements.

2. Occurrence of Correlations in ChemicalAnalysis

2.1. Determination of Intercept and Slope of aLinear Calibration Curve

Basic facts : Intercept g and slope d of a linearcalibration curve y = g + dx (e.g. x: analyteconcentration, y: instrumental response) arestrongly correlated, since they are estimated fromthe same set of calibration points (x1,y1), (x2,y2),... , which are subject to errors. This correlationhas to be included in the uncertainty budget of anyestimate x calculated from a measured value y.Intercept and slope are always anti-correlated, i.e.the covariance u(g, d) is always negative and willoften compensate a major part of the contributionof the uncertainties u(g) and u(d). In the standardleast squares uncertainty estimate (confidenceinterval) this correlation is included. For otherregression procedures this correlation has to betaken into account in the uncertainty budget.

In the following a linear analysis function,to be used for converting instrumental responsey into analyte concentration x, is expressed asx = a + by instead of utilising the inverted formof the calibration function, x = (y - g)/d. Herethis is done to simplify the uncertainty budgets

256


to follow, but direct determination of analysisfunction parameters (inverse calibration) hasother advantages over the standard procedure(classical calibration) [4].

The uncertainty budget for an analytecontent x, calculated from a measured responsey, is given by two components, as follows :

), x(u)y x(u(x)u 222 βα+= (10)

Here u(x/y) accounts for the uncertainty ofmeasuring y,

)y(u)y x(u 222 β= (11)

while u(x½a,b) refers to the calibrationuncertainty, i.e. the uncertainty associated withthe determination of the calibration lineparameters.

)(uy),(yu2)(u), x(u 2222 β+βα+α=βα (12)

In the last equation, the correlation term u(a,b )accounts for the joint effect of errors in thecalibration data on the intercept and slope of acalibration line determined from these data,using an interpolation or regression procedure.This correlation is always negative (r(a,b ) < 0)and most often very strong (r(a,b ) ® - 1), thuscancelling to a large degree the other twopositive terms. The balance between the twopositive variance terms and the negativecovariance term gives rise to the well-knownhyperbolic form of the uncertainty envelope ofa calibration line. Using the correlationcoefficient r(a,b ), as given by u(a,b ) =r(a,b )u(a)u(b), and introducing the point ymin= êr(a ,b) êu(a )/u(b) where the calibrationuncertainty u(y½a,b) becomes a minimum, eq.(12) takes the form

2 2 2 2min(x , ) u ( ) 1 r ( , ) (y y ) u ( ) α β = α − α β + − β

2u (13)

from which the form of the uncertaintyenvelope is apparent. For the standard leastsquares estimates of a calibration line, ymin isthe average of the calibration data y1, y2, ….

However, the considerations above are alsoapplicable to any other technique fordetermining a calibration line from a set ofcalibration points, and for estimating itsuncertainty.

Most often the standard uncertainties u(a),u(b) and the covariance u(a,b ) are determinedfrom the residual scatter of the calibrationpoints around the calibration line.Alternatively, if uncertainty estimates areavailable for the calibration data x1, x2, …. andy1, y2, …., then u(a), u(b) and u(a,b ) may bedetermined by uncertainty propagation [5].

2.2. Repeated Use of the Same CalibrationCurve

Basic facts : If a calibration curve is used tocalculate the analyte concentration of severalsamples from measured responses, the results willbe correlated since they are estimated using thesame calibration curve, which is subject to errors.This correlation has to be taken into account in anyjoint application of the results obtained, e.g. whenanalysing several samples of the same material andtaking an averaging of the results.

In the framework of the previous section,let y and y’ be the responses obtained on twodifferent samples, and let x and x’ be the valuesof the analyte concentration obtained fromthese data using the relationship x = a + by.Then a covariance arises as follows :

)(uyy),(u )yy()(u)xu(x, 22 β′+βα′++α=′ (14)

Using the same approach as in the previoussection, this covariance may be expressed inthe form

[ ] )(u )yy)(yy()(u ),(r1)xu(x, 2minmin

22 β−′−+αβα−=′ (15)

As apparent from the last equation, thiscorrelation may be positive or negative,depending on whether the responses y and y’are on the same side or on different sides relativeto ymin. In addition, eq. (15) shows that thecovariance term is relevant when calibration

257


uncertainty contributes significantly to theuncertainty of prediction.

The standard uncertainty of the mean value<x> = ½(x + x’) is given by

( ) ( ) ( ) ( )2 2 21u x u x u x 2u x,x

4 = + +′ ′ (16)

In the simple case considered previously -linear analysis function, linear combination ofresults - it would not be necessary to explicitlyaccount for correlations. Alternatively, theresponses could be averaged, the averageresponse converted in an analyte concentration,and its uncertainty be calculated according toeq. (10). However, this simplification is notapplicable when the analysis function is non-linear or when non-linear combinations ofanalytical results are utilized.

2.3. Correlation Among Calibrants

Basic facts : Correlation among calibrants mayoccur, e.g. in dilution series derived from a standardsolution, or in standard addition methods. Thiscorrelation has to be taken into account in theuncertainty budget for the parameters of thecalibration curve. In addition, it may have an impacton the parameter estimates themselves.

Common statistical methods fordetermining a calibration curve (such asstandard least squares and weighted leastsquares) neglect the uncertainty associated withthe calibrants, more specifically, the uncertaintyof the analyte concentration in the calibrationsamples. Likewise, the possibility of correlationamong calibrants is completely ignored.Fortunately, there are other techniques (e.g.maximum-likelihood techniques) which enableto account for both features, the uncertaintyof, and correlation among calibrants. This isdone by minimizing a quadratic form whoseingredients are the distances of the calibrationpoints from the candidate regression curve andthe variances and covariances of the calibrationpoints, referring to both co-ordinates of a

calibration point (xi,yi). When using thisapproach, it is beneficial to estimate theuncertainty of a calibration curve bypropagation of the uncertainty associated withthe calibration data instead from the residualscattering. If this is done, correlation amongcalibrants is easily included by adding therelevant covariance terms.

The impact of correlation among calibrantswas investigated in ref. [6], using thegeneralized least-squares approach combinedwith uncertainty propagation. As a generalfeature, correlation was found to effect a lossof reliability. This is mainly due to a virtualreduction of degrees of freedom for subsets ofcorrelated calibration points. In addition, thefit of the calibration curve to the calibrationpoints may get worse. For moderate correlationthe main effect is on the uncertainty envelopeof the calibration curve, while the curve itselfis much less affected. For weak correlation theparameters of the calibration curve may beestimated using the generalized least-squaresprocedure without correlation, whilecorrelation has to be included in estimating theuncertainty of the parameters.

As a general recommendation, correlationamong calibrants should be avoided or at leastkept to a minimum. When utilizing standardaddition or dilution series, this requirement canbe met by appropriate design of the calibrationexperiment, e.g. by using independent dilutionsinstead of successive dilutions.

2.4. Correlation Among Repeated Measure-ments

Basic facts : Most often repeated measurements,in partícular when carried out on similar measuringobjects, have major uncertainty contributions incommon, e.g. calibration uncertainty oruncertainty of measuring conditions. If theseuncertainty contributions are significant, the resultsof repeated measurements are significantlycorrelated. This correlation has to be taken intoaccount in the estimation of uncertainty for any

258


combination of measurement results such as meanvalues or differences.

Let y and y’ be measurement resultsobtained using the same measurementprocedure. Then y and y’ may be viewed asdepending on the same input variables, takingpartly the same and partly different values. Forexample, if the ambient temperature in thelaboratory (monitored on a regular basis) is aninput variable, then y and y’ could eitherdepend on the same temperature measurementor different temperature measurements.Assuming that all input quantities weredetermined independently, the covariancebetween y and y´ is given by

( ) ( ) ( ) ( )2u y, y c z c z u zy y= ⋅ ⋅∑′ ′ (17)

where the sum is over all input quantities zshared by y and y’, and the c’s are the sensitivitycoefficients concerned. Let ucom(y) anducom(y’) be that part of the combined standarduncertainty of y and y’, respectively, which isdue to the shared (common) input values, i.e.

( ) ( ) ( )u y c z u z 22

com y= ⋅∑ (18)

Then u(y, y’) £ ucom(y) ucom(y’), and the producton the right-hand side of this inequality is in fact areasonable approximation if cy(z) » cy’(z) for all z,or if the ratio cy(z) / cy’(z) is approximatelyconstant. This may be assumed if y and y’ areobtained using the same measurementprocedure on similar objects/samples.

An estimate of the covariance between y andy’ is required for proper evaluation of theuncertainty for combinations of measurementresults such as

( ) ( ) ( ) ( )u y y u y u y 2u y, y2 2 2± = + ±′ ′ ′ (19)

and analogous expressions for products andquotients, then involving relative uncertaintiesand covariances.

The estimate u(y, y’) = ucom(y) ucom(y’)obtained above is particularly suitable forreplicate measurements on the same object/sample. This may be used to evaluate thecombined standard uncertainty of a meanvalue as follows. Let x1, x2, …, xn be the resultsof replicate measurements on the same objector sample, and let <x> denote the mean valueof the xi. The standard uncertainty of this meanis given by

( ) ( ) ( )1u x u x u x , x

n

2 2i j k2 i j k

⟨ ⟩ = +∑ ∑≠

(20)

Since we are dealing with replicates, we mayassume that all the u(xi) are the same andreplace them by a common estimate u(x). Nowconsider a decomposition of the combinedstandard uncertainty u(x) of a singlemeasurement according to

( ) ( ) ( )u x u x u x2 2 2var inv= + (21)

where uvar(x) is the combined standarduncertainty accounting for all influencequantities which are effectively varied betweenreplications, while uinv(x) is the combinedstandard uncertainty accounting for allinfluence quantities which are effectivelyinvariant under replication conditions and arethus shared by all replicates. Then thecovariance between any two replicates is givenby u(x, x’) = uinv(x) uinv(x’) = uinv

2(x). Usingthis estimate and equation (22), the standarduncertainty of a mean value <x> is obtained asfollows :

( ) ( ) ( ) ( )

( ) ( )

1u x n u x n n 1 u x

n

u xu x

n

2 2 2inv2

22varinv

⟨ ⟩ = ⋅ + − ⋅

= +

(22)

It may be helpful to obtain a visualimpression on the impact of correlations on the

259


uncertainty of a mean as expressed by equation(22). Figure 1 illustrates the development of theuncertainty of a mean with increasing numberof replicates combined into the mean for thecase of a) a small (r = 0.1) and b) a considerably

1 2 3 5 10 30 50Number of replicates

(a)

1

0.8

0.6

0.4

0.2

0

without correlation

taking correlation into account

Unc

erta

inty

of t

he m

ean

r = 0.1

1 2 3 5 10 30 50Number of replicates

(b)

1

0.8

0.6

0.4

0.2

0

Unc

erta

inty

of t

he m

ean

r = 0.8

Fig. 1(a, b). Development of the uncertainty of the mean with increasing number ofreplicates for (a) small (r = 0.1) and (b) considerably large (r = 0.8) correlation

large (r = 0.8) correlation coefficient betweenthe single replicates.

It can clearly be seen from the graphs thatthe difference in the uncertainty estimates forthe mean is

260


i) insignificant for small correlationcoefficients and moderate numbers ofreplicates combined (up to a number of 5,which is a common upper limit in achemical laboratory) but becomes noticableat large numbers of replicates;

ii) significant for large correlation coefficients,and cannot be neglected even if only a smallnumber of replicates has been taken.

However, often it will be difficult to performthe separation of influence quantities indicatedabove. This will happen if the uncertaintybudget includes estimates for combinedcontributions, such as precision or recoveryestimates for major parts of the procedure, orif the uncertainty of input quantities includesrandom and systematic parts.

In absence of a clear separation, the wayforward is to utilise the intermediate-precisionstandard deviation sIR [7], referring toappropriate within-laboratory reproducibilityconditions, as obtained from regular precisionmonitoring using control charts. Estimatinguvar(x) by sIR yields u(x,y) = uinv

2(x) = u2 - sIR2

with the final result

( ) ( )( )22 2 2IR

IRs

u x u x sn

= + − (23)

Thus reduction of uncertainty by averagingis restricted to the "random part" ofmeasurement uncertainty, while the"systematic part" remains unchanged.

As another case of interest besides meanvalues, consider the difference of measurementresults obtained using the same measurementprocedure on the same object or similar objects.The combined standard uncertainty of adifference is given by

( ) ( ) ( ) ( )2 2 2u y y u y u y 2u y,y− = + −′ ′ ′ (24)

If the uncertainties of y and y' are the same,

the estimate u(x,y) = u2 - sIR2 gives

( )2 2IRu y y 2s− =′ (25)

while neglect of correlations would give a resultof 2u(y)2. This gain of accuracy is due tocancellation of systematic effects in differences(and similarly in quotients) of measurementresults, e.g in differential weighings.

2.5. Correlation in Reference MaterialCertification Studies

Basic facts : Correlation among inter-laboratorycertification study data may occur, if participants´methods of analysis include a common step whichcontributes significantly to the measurementuncertainty. This correlation has to be taken intoaccount in the uncertainty budget of consensusvalues. In the common case of an unweighted meanof laboratory means, correlation between laboratorymeans would invalidate the common factor 1/Önused in calculating the standard deviation of asample mean value from the standard deviation ofthe sample. When using uncertainty-weightedaverages instead of unweighted averages,correlation between laboratory means may have asignificant effect on the uncertainty of a consensusvalue and on the consensus value itself.

The description below refers to cases whereeach participant p in a certification studydelivers a single value zp as his best estimate ofthe property value in question, together with astandard uncertainty u(zp) of this estimate. Ifthese uncertainties are reliable, and if theparticipants results agree within uncertaintylimits, the best collaborative estimate*) zopt isobtained by minimizing the sum of squaredinverse-variance weighted deviations.

∑ =−

p p2

2optp minimum)z(u

)zz((26)

The solution of this minimization problem is

*) i.e. with minimum uncertainty

261


given by the inverse-variance weighted mean.

∑∑=

)z(u 1

)z(uzz

p2

p2

popt (27)

In case of significant correlations between theresults of different participants eq. (26) wouldbe modified as follows :

p opt pq q optp q

(z -z )W (z -z )=minimum∑ ∑ (28)

In this equation Wpq denotes elements of theinverse variance/covariance matrix Wassociated with the participants results, i.e. thematrix obtained by inversion from the matrixV made up by the variances Vpp = u2(zp) andthe covariances Vpq = u(zp,zq).

The covariances u(zp,zq) would be determinedby extracting and combining joint componentsof participants uncertainty budgets.

Preliminary investigations have shown thatcorrelation may have a significant effect on theconsensus value and, predominantly, on itsuncertainty. However, this issue could onlybecome relevant after a change of paradigm inthe design and evaluation of inter-laboratorycertification studies, as currently underconsideration in the revision of ISO Guide 35[8].

2.6. Correlation Among Mixture CompositionData

Basic facts : When several or all components of amixture of substances are analysed jointly, commonanalytical steps will often cause significantcorrelation between the results. This correlation hasto be taken into account in the estimation ofuncertainty for mixture property data calculatedfrom composition. A prominent example isprovided by the analysis of natural gas.

Due to the availability of accurate andreliable analytical methods, physical properties

of gas mixtures are increasingly calculated fromanalysed composition instead of beingmeasured directly. Accounting for thisdevelopment, determination of calorific valueand density of natural gas by compositionanalysis and subsequent calculation have beenstandardised in ISO 6976 [9].

As a characteristic feature, theseapplications require the complete compositionof the gas mixture, i.e. the proportion of everyspecified mixture component, most often inmole fractions. Given the molar compositionand the component property data, the mixtureproperty is typically calculated as a weightedsum

mix i ii

P x P= ⋅∑ (29)

where Pmix and Pi denote the value of theproperty under consideration for the entiremixture and component i, while xi denotes themole fraction of component i.

The uncertainty sources for mixtureproperty estimates obtained in this manner are(a) uncertainty of the component propertydata, (b) uncertainty of the composition data,and (c) uncertainty related to errors in theequation (e.g. due to neglect of higher-orderterms). These uncertainty sources arecompletely independent. Therefore theuncertainty budget may be expressed asfollows:

( ) ( )( ) ( )

2 2mix mix

2 2mix mix

u P u P / prop

u P /comp u P /equa

= +

+(30)

Assuming that component property data weredetermined independently, u(Pmix/prop) iscalculated by a straightforward (root) sum ofsquares from the uncertainties of thecomponent property data.

( ) ( )2 2 2mix i i

i

u P / prop x u P= ∑ (31)

262


For the third term u(Pmix / equa) a priorestimate will not normally be available.Information about the magnitude of this termmay be obtained by comparing the results ofcalculations obtained without this term and theresults of direct measurements forrepresentative natural gas samples. For thecalorific value and the density this term can beneglected.

The second term u(Pmix / comp) iscalculated from the uncertainties of thecomponent mole fractions. However, completemixture composition data are always highlycorrelated. Therefore, in principle, thecalculation has to include covariances betweencomponent mole fractions as follows :

( )( ) ( )

2mix

2 2i i i k i k

i i k i

u P / comp

P u x P P u x , x≠

=

+∑ ∑ ∑ (32)

Examples show that the correlation termsoften have a large impact on the uncertainty.Currently, however, estimation andspecification of covariances u(xi,xk) is not state-of-the art in natural gas analysis. Fortunatelythere are some ways out as follows:

i. Mathematical reasons, supported byexample calculations, lead to the conclusionthat, if all property data Pi are positive, thesecond term on the right-hand side ofequation (32) will most often be negative,partly cancelling the first positive term.Therefore disregarding the correlation termwill most often result in an over-estimationof u2(Pmix / comp). If the uncertaintyestimates obtained in this manner are fit forpurpose, this procedure is acceptable.

The level of over-estimation depends on thespan of the component property data Pi. Ifthe span is small compared to the average,the terms on the right-hand side of eq. (32)will almost cancel. If the span is larger,there will be less cancellation.

ii. If the raw composition data obtained byanalysis (i.e. before any further processing)are mutually independent, then the"covariance complication" may be defusedby substituting the raw composition datainto the equation for calculating the mixtureproperty in question. However, often theraw composition data will be significantlycorrelated, with the consequence that the"covariance complication" arises on thatlevel.

iii. Often correlation among raw compositiondata will arise from variations in theamount of sample, due to variations ofpressure and temperature. As a simple case,let all the analysed components bedetermined by gas chromatography in thesame run. Then variations in sampleamount have the same effect for all thesecomponents. Therefore samplinguncertainty gives rise to a correlationbetween any two of the component molefractions. The covariances accounting forthese correlations may be determined asfollows :

Let the mole fractions be expressed as xi =ni/nS by the amount of analyte and the amountof sample, determined independently. Then theuncertainty of the mole fraction is given byu2(xi) = xi

2[v2(ni) + v2(nS)] where the symbol vis used to denote relative standard uncertainty.The covariance between mole fractions ofdifferent analytes is given by u(xi, xk) = xi xkv2(nS).

Given an estimate of the (relative) samplinguncertainty v(nS), e.g. from recorded variationsof pressure and temperature, this correlationterm is easily implemented in the calculationaccording to equation (32).

The final result depends on the mode ofprocessing the raw analytical data, i.e. whetherthe main component methane is determinedby dífference or by direct measurementfollowed by normalisation.

263


3. Outlook

In analytical chemistry, measurementresults are often strongly interrelated, wherequantities to be determined depend on severalinput quantities, and different determinandshave input quantities in common. In suchnetworks, uncertainty propagation has to takecorrelation into account. At present, however,there is not much guidance available on thehandling of correlation in uncertainty budgets.In the main reference document onmeasurement uncertainty, the "Guide to theExpression of Uncertainty in Measurement" [1],the basic equations are indeed contained, butthey are hidden in annexes and examples, andnot much explanation is provided. This is alsotrue for the Eurachem Guide "QuantifyingUncertainty in Analytical Measurement" [2].As a notable exception, going beyond the levelof the GUM, the german standard DIN 1319-4[10] provides a comprehensive description ofuncertainty estimation for multiplemeasurands. At the international level, onlyrecently the Joint Committee for Guides inMetrology (JCGM) [11] has taken up work ona suppplement to the GUM on "multivariate"uncertainty estimation.


The intention of the present paper is topoint out common measurement issues,arising in chemical analysis and othermeasurement fields, where correlationsarise and should be taken into account, andto indicate how this could be done.However, this is only a summary, and fullyworked-out examples would be needed tomake these tools effectively available.

References

[1] ISO (1995), Guide to the Expression of

Uncertainty in Measurement, ISO,Geneva.

[2] EURACHEM (2000), QuantifyingUncertainty in Analytical Measurement,Internet: http://www.eurachem.ul.pt

[3] W. Mannhart (1981), a Small Guide toGenerating Covariances of Experimental,Data Report PTB-FMRB-84, PTB,Braunschweig.

[4] J. Tellinghuisen, Fresenius J. Anal. Chem.,368 (2000), 585.

[5] W. Bremser and W. Hässelbarth, Analyt.Chim. Acta., 348 (1997) 61.

[6] W. Bremser and W. Hässelbarth, AccredQual Assur, 3 (1998) 106.

[7] ISO 5725-3 (1994), Accuracy (trueness andprecision) of Measurement Methods andResults - Part 3 : Intermediate Measuresof the Precision of a Standard Measure-ment method.

[8] ISO/IEC Guide 35 (1989), Certification ofReference Materials - General andStatistical Principles (under revision).

[9] ISO 6976 (1995), Natural Gas - Calculationof Calorific Value, Density, RelativeDensity and Wobbe Index fromComposition (under revision).

[10] DIN 1319-4 (1995), Grundlagen derMesstechnik - Auswertung vonMessungen; Messunsicherheit.

[11] JCGM (> 2005), GUM Supplement 2: TheTreatment of More Than One Measurand(provisional title, in preparation) see BIPMWebsite: www.bipm.org > Committees >Joint committees > JCGM > WG1.

264


264

MAPAN - Journal of Metrology Society of India

VOLUME CONTENTS(Volume 19, January-December 2004)

Numbers 1-2, January - June 2004


Preface 3

Evolving Needs for Metrology in Trade, Industry and Society 5Robert Kaarls

Rapid Progress made in Metrology in Chemistry by the 11Consultative Committee for Amount of Substance - CCQMRobert Kaarls

Metrology from a Practitioner's Point of View 19Bryan Kibble

Relevance of NABL Accreditation towards the Quality 23Scenario in IndiaA.K. Chakrabarty

Relevance and Adequacy of Measurements : 33Management PerspectiveS.K. Kimothi and R.P. Sondhi

Mutual Recognition of Laboratories 37Key to Meet Challenges for Automotive TradeRashmi Urdhwareshe

Metrological Equipment for Manufacturing and Testing 43Gyroscopes, Accelerometers and Inertial Navigation SystemsG.I. Djandjgava, V.L. Budkin and A.K. Salomatin

Comparison of Calibration Procedures for Force Gauges to Establish 53Traceability in Force MeasurementS.K. Jain, Kamlesh K. Jain and Anil Kumar

Design, Development and Characterization of 5 kN Force Gauge 61J.K. Dhawan, Kamlesh K. Jain, S.S.K. Titus and Rajesh Kumar

265

Investigation of Hysteresis Loop of Universal Length Measuring Machine 69and its Effect on Linear MeasurementArif Sanjid, R.P. Singhal, K.P. Chaudhary, Vijay Kumar and Sameer

Analysis of Errors for Photolithographic Mask-Wafer Alignment 83using Modified Moiré TechniqueRina Sharma, V.N. Ojha, H. Furuhashi, Y. Uchida and V.T. Chitnis

Present Status of Mass Measurement at NPL India and its Metrological 91Equivalence in Regional and Global Metrology NetworkTripurari Lal, M.L.Das, Goutam Mandal and Harish Kumar

Illuminancemeter - An Important Device for Photometry 103B.K. Yadav, D.P. Bahuguna, Jai Bhagwan and H.C. Kandpal

Measurement of the Resolving Power of Convex Lenses 109Om Prakash

Insulation Resistance Measurement of High Impedance Accelerometer Cables 117V.N. Ojha, Sudhir K. Sharma, S.K. Singhal and G.S. Lamba

HPLC Studies on Evaluation of Purity of Pesticide Reference Standard Materials 121R. Nageswara Rao and S. Naseeruddin Alvi

Estimation of Uncertainty of Measurement in Quantitative Analysis of 127Minor Constituents of SteelRashmi and R. Ramachandran

Fortyfirst List of Fellows, Members and Company Members 133

Form IV 136

Number 3, July - September 2004

Optical Setup of the Proposed Laser Cooled Cs 139Fountain at NPL, IndiaSanta Chawla and Amitava Sen Gupta

Intercomparison between NIS and IMGC Viscosity 149Scales in the Range from 14 000 mm2/s to ~70 000 mm2/sand Extension of the National Viscosity Scale from70 000 mm2/s up to 100 000 mm2/sM. Mekawy and S. Lorefice

Comparison between Stability and Reproducibility of 155Au/Pt, Pt/Pd and Pt-10%Rh/Pt ThermocouplesYasser A. Abdelaziz

Realization of Tin and Zinc Fixed Points on the ITS-90 163at the National Institute for Standards (NIS) in EgyptM.G. Ahmed and K. Ali

266

Interlaboratory Proficiency Testing : Liquid-in-Glass 169Thermometer Intercomparison-2001/02Y.P. Singh, S.K. Nijhawan, R.P. Singhal, A.K. Saxena and S.U.M. Rao

Interlaboratory Proficiency Testing : 177Thermocouple Intercomparison-2001/02Y.P. Singh, S.K. Nijhawan, R.P. Singhal, A.K. Saxena and S.U.M. Rao

MSI Committees 185

Number 4, October - December 2004

Preface 189

Recent Developments in Metrology in Chemistry 191Robert Kaarls

Metrological Challenges in Bioanalysis 197Helen Parkes

Update on COMAR - the Internet Database for 203Certified Reference MaterialsThomas Steiger and Rita Pradel

Present Status of Certified Reference Materials in India 209A.K. Agrawal

The Provision of Reference Materials in Japan 219Toshiaki Asakai

The Reference Materials Programme at the Australian 239National Measurement InstituteL.M. Besley

Certification of In-house Reference Materials 245Ilya Kuselman

Correlation in Chemical and Other Measurements 253Werner Haesselbarth and Wolfram Bremser

Volume Contents 264

Author Index 267

267

Author Index

MAPAN - Journal of Metrology Society of India, Vol. 19, No. 4, 2004; pp. 267

Abdelaziz, Yasser A. 155

Agrawal, A.K. 209

Ahamed, M.G. 163

Ali, K. 163

Alvi, Naseeruddin S. 121

Anil Kumar 53

Asakai, Toshiaki 219

Bahuguna, D.P. 103

Besley, L.M. 239

Bremser, Wolfram 253

Budkin, V.L. 43

Chakrabarty, A.K. 23

Chaudhary, K.P. 69

Chawla, Santa 139

Chitnis, V.T. 83

Das, M.L. 91

Dhawan, J.K. 61

Djandjgava, G.I. 43

Furuhashi, H. 83

Harish Kumar 91

Haesselbarth, Werner 253

Jai Bhagwan 103

Jain, Kamlesh K. 53, 61

Jain, S.K. 53

Kaarls, Robert 5,11,191

Kandpal, H.C. 103

Kibble, Bryan 19

Kimothi, S.K. 33

Kuselman, Ilya 245

Lal, Tripurari 91

Lamba, G.S. 117

Lorefice, S. 149

Mandal, Goutam 91

Mekawy, M. 149

Nijhawan, S.K. 169, 177

Ojha, V.N. 83, 117

Om Prakash 109

Parkes, Helen 197

Pradel, Rita 203

Rajesh Kumar 61

Ramachandran, R. 127

Rao, Nageswara, R. 121

Rao, S.U.M. 169, 177

Rashmi 127

Salomatin, A.K. 43

Sameer 69

Sanjid, Arif 69

Saxena, A.K. 169, 177

Sen Gupta, Amitava 139

Sharma, Sudhir K. 117

Sharma, Rina 83

Singh, Y.P. 169, 177

Singhal, R.P. 69, 169, 177

Singhal, S.K. 117

Sondhi, R.P. 33

Steiger, Thomas 203

Titus, S.S.K. 61

Uchida, Y. 83

Urdhwareshe, Rashmi 37

Vijay Kumar 69

Yadav, B.K. 103

268

MAPAN - JOURNAL OF METROLOGY SOCIETY OF INDIAInstructions to Contributors

MAPAN-Journal of Metrology Society of India is a quarterly publication. It is exclusively devoted toMetrology (Scientific, Industrial or Legal). The Metrology Society of India (MSI) invites the submission ofresearch communications or technical articles on topics of current interest. Original work, tutorials andsurvey papers, which contribute to new knowledge or understanding of any metrology principle, methodor technique are welcome.Papers are considered for publication on the clear understanding that they have not been publishedpreviously or submitted to another journal for publication. Further, papers published in MAPAN-JMSI willnot be sent for publication elsewhere. Papers should be clearly written in English and sent in duplicate tothe Managing Editor or may be submitted to any one of the Editorial Board Members.Elements of the Manuscriptsl A cover sheet consists of a short title, names, affiliations and addresses of all the authors.l Manuscript must start from the next page with title on top of the page.l An abstract of about 100-200 words should be provided on the title page. This should be readable

without reference to the article and should indicate the scope of the contribution, including the mainconclusions.

l An introduction, which may begin with what is new in the paper, not with statement that is well knownto everyone.

l Appropriate section of the text.l A conclusion.l An acknowledgement (optional).l A list of references in proper format.l A set of original figures and tables.l A list of captions for all figures and titles for all tables.ReferencesReferences must be prepared in proper format (examples of various types are given below) and numberedconsecutively in the order in which they are cited in the text.Books : Author(s) name, title of the book, publisher (year) pp. first and last page no.Periodicals : Author(s) name, title of article, name of journal, vol. no. (year) pp. first and last page no.Example :[1] G. B. Gao and X. Gui, Reliability Physics as a New Discipline, Microelectron. Reliab., 28(1988) 713-

720.Conference records : Author(s) name, title of article, name of conference, place where held (year) pp.first and last page no.Unpublished conference presentations : Author(s) name, title of article, name of conference, placewhere held, year.Technical reports : Author(s) name, title of article, report no., published by, year.CopyrightAuthors have to fill the transfer of copyright form at the time of acceptance of paper for publication.Right of PublicationThe Publication & Information Committee reserves the right of publication. The Committee is notresponsible for the views expressed by the Authors.

Metrology Society of India(Regn. No. S-15149/1984)

Executive Council (2003 - 2005)

President : Dr. Vikram Kumar

Vice Presidents : Mr. S.C. Garg(Chairman, Program Committee)

Prof. Z.H. Zaidi(Chairman, Education Committee)

General Secretary : Dr. R.P. Singhal

Joint Secretary : Dr. R.K. Garg(Chairman, Publication & Information Committee)

Treasurer : Mr. Tripurari Lal

Members : Dr. A.K. Agrawal(Chairman, Membership Committee)

Dr. Ashok Kumar(Convener, 5th International Conf. on Metrology)

Mr. A.K. GovilMr. Prabhat K. GuptaDr. P.C. JainMr. S.U.M. RaoMrs. Veena RoonwalMr. V.K. Rustagi(Secretary, Program Committee)

Mr. A.K. SaxenaDr. Y.P. Singh

Ex-officio Member : Mr. S.D. Janakiram(Chairman, Southern Regional Branch)

Co-opted Members : Mr. P.K. Aggarwal, M/s. Maruti Udyog Ltd., Gurgaon

Mr. M.L. Bagga, M/s. Bagsons, Delhi

Mr. S. Dasgupta, BIS, New Delhi

Mr. G.J. Gyani, QCI, New Delhi

Mr. S.K. Kimothi, STQC, New Delhi

Mr. M.L. Mangal, M/s. S.V. Engg. Centre, Faridabad

Mr. D.S. Tewari, New Delhi

Invitees : Mr. N.K. Aggarwal(Secretary, Education Committee)

Mr. Anil Kumar(Secretary, Publication & Information Committee)Dr. K.K. Jain(Co-Chairman, Education Committee)

Dr. Mukesh Chandra(Secretary, Membership Committee)Mr. Palyam Ramesh(Secretary, Southern Regional Branch)

RNI Regn. No. 45863/86

Metrology Society of IndiaCompany Members

27. CM 0064 : M/s Tajima ASA Bhanu Tools Ltd.302, Saaz Apts. Road No. 1, Banjara Hills, Hyderabad-500 034

28. CM 0065 : M/s Advance Technical Systems305, Pankaj Tower, Mayur Vihar, Phase-I, Delhi-110 091

29. CM 0066 : Bhilai Steel Plant, Bhilai-490 00130. CM 0067 : M/s Size Control Gauges & Tools (P) Ltd.

218, Poornima Towers, 397, Shankar Seth Road, Pune-41103731. CM 0068 : Electronics Regional Test Lab. (South)

Kettron House, Vellayambalam, Thiruvananthapuram-3332. CM 0069 : Safisticated Test & Instrumentation Centre

Cochin University, Kochi-682 02233. CM 0070 : M/s Japsin Test House, 3610-12, Japsin Mansion,

Parmanand St., Daryaganj, Delhi-110 00234. CM 0071 : M/s Maruti Udyog Ltd., Gurgaon, (Haryana)35. CM 0072 : M/s Shiva Metrology Instruments (P) Ltd.

Plot No. 65E5, Hootagallery Indl. Area, Mysore-571 18536. CM 0073 : M/s Crompton Greeves Ltd.

D-5, Industrial Area, Mandeep, Bhopal-462 04637. CM 0074 : M/s Askib Engineers (P) Ltd.

47, Lanin Sarani, P.O. Box No. 8927, Kolkata-700 01338. CM 0075 : M/s Saw Pipes Ltd., A-1, UPSIDC Indl. Area,

Nandgaon Road, Kosi-kalam, Mathura-281 40339. CM 0076 : M/s Banbros, Engg. Pvt. Ltd.,

105, Usha Chambers, New Rajdhani Enclave, Delhi-110 09240. CM 0077 : M/s Multitek

B-21, CEL Apartments, B-14, Vasundhara Enclave,Delhi-110 096

41. CM 0078 : M/s S.V. Precision InstrumentsShed No. 11A & 11B, Kukatpally, Hyderabad-500 072

42. CM 0079 : Central Institute of PlasticsMin. of Chem. & Fertil., Govt. of India, Lucknow-226 008

43. CM 0080 : M/s MCCOY Research & Calibration Lab.886, East Park Road, Karol Bagh, New Delhi-110 005

44. CM 0081 : M/s Sartorius India (P.) Ltd.No. 10, 3rd Phase Peenya, 6th Main, Bangalore-560 058

45. CM 0082 : M/s Trimos Metrology (I) Pvt. Ltd.52, Arun Talkies Building, Dapodi, Pune-411 012

46. CM 0083 : Aeronautical Development Establishment, DRDOMinistry of Defence, C.V. Raman Nagar, Bangalore-560 093

47. CM 0084 : Bharat Dynamics Ltd., Ministry of Defence,Bhanur - 508305, Dist . Medak (Andhra Pradesh)

48. CM 0085 : M/s Gatrad Engineering Corporation248, GIDC Industrial Estate, Telephone Exchange Road,Odhav, Ahmedabad - 382 425

49. CM 0086 : Electronics and Quality Development CentreB-177/178, GIDC Electronics State, Gandhi Nagar - 382 044

50. CM 0087 : M/s. Craftsman Automation Pvt. Ltd.15, LML Colony, Amman Kulam Road, Coimbatore - 641 037

51. CM 0088 : Electronic Regional Test Laboratory (North)S Block, Okhla Ind. Area, Phase II, New Delhi-110 020

52. CM 0089 : M/s. Hema Engineering Industries Ltd.1/3, K.M., Khandsa Road, Gurgaon-122 001 (Haryana)

1. CM 0003 : M/s Avery India Ltd.,50-54, Sector 25, Ballabgarh-121 004

2. CM 0004 : M/s BAGSON78, South Anarkali, P.O. Krishan Nagar, Delhi 110 051

3. CM 0007 : M/s Shanker Wires Products Industries,B. Deoghar-814112

4. CM 0011 : M/s. LEIMCO119, Madhai Industrial Estate, Khopat, Thane,(Maharashtra)

5. CM 0015 : Electronics Corpn. of India Ltd.Standards & Quality Assurance GroupIndl. Development Area, Cherlapalei, Hyderabad - 500 762.

6. CM 0016 : M/s Baker Mercer (I) Pvt. Ltd.,33/1/2, Nagar Road, Pune - 410 014

7. CM 0025 : Research, Design & Standards OrgnManak Nagar, Lucknow - 226011

8. CM 0026 : M/s Associated Instruments Mfrs (India) Ltd.A-8, Mohan Coop. Indl. Estate, Mathura Road, New Delhi-44

9. CM 0027 : Opto-electronics Factory, Ministry of DefenceRaipur, Dehra Dun - 248 008

10. CM 0028 : M/s Secure Meters Pvt. Ltd.P.O. Box. No. 20, Udaisagar Road, Udaipur - 313 001

11. CM 0029 : Senior Quality Assurance Estt. (Armament)Cossipore, Kolkata -700 002

12. CM 0036 : Bharat Heavy Electricals Ltd., Bhopal - 46202213. CM 0043 : M/s. Autometers Ltd., B-1, Sector-2, Noida-20130114. CM 0046 : Fluid Control Research Institute,

Kanjikode (West), Palghat-678 62315. CM 0049 : M/s. Sona Steering Systems

38/6, Delhi-Jaipur Road, Gurgaon-122 00116. CM 0052 : M/s Lawkin Limited

SV Road, Chitalsar, Manpada, Thane-400 60717. CM 0053 : M/s Micro Flat Datums Mfrs

25-26, GIDC, Vitthal Udyog Nagar,Vallabh-Vidyanagar-388121

18. CM 0054 : National Test House (Eastern Region)11/1 Judges Court Road, Alipore, Kolkata-700 027.

19. CM 0055 : Small Industries Testing & Research Centre,No. 25-A, Avarampalyam Road, K.R. Puram, Coimbatore-6

20. CM 0057 : M/s Senapathy Whiteley Pvt. Ltd.,P.O. Box No. 10, Achalu, Ramanagaram-571 511

21. CM 0058 : Senior Quality Assurance Establishment(Electronics),Ministry of Defence, Kolkata-700 022.

22. CM 0059 : Bharat Heavy Electricals Ltd., Jhansi-28412923. CM 0060 : M/s Alka Lab., 311-316, Ashiana Trade Centre,

P.O. Adityapur, Jamshedpur-1324. CM 0061 : M/s Ensons Gages & Tools (P) Ltd.

409, Creative Indl. Estate, NM, Joshi MargMumbai-400 011

25. CM 0062 : M/s Titan Industries Ltd., Watch Division,3 SIPCOT, Industrial Complex, Hosur-635126

26. CM 0063 : M/s Unique Instruments & Mfrs. (P) Ltd.433, Peenya Industrial AreaIV Phase, 3rd Main, 11th Cross Road, Bangalore-560 058