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Analytica Chimica Acta 599 (2007) 177–190

Towards the development of a fossil bone geochemical standard:An inter-laboratory study

V. Chavagnac a,∗,1, J.A. Milton a, D.R.H. Green a, J. Breuer b, O. Bruguier c, D.E. Jacob d,T. Jong e, G.D. Kamenov f, J. Le Huray g, Y. Liu h, M.R. Palmer a, S. Pourtales c,

I. Roduhskin i, A. Soldati d, C.N. Trueman a, H. Yuan j

a National Oceanography Centre Southampton, University of Southampton, European Way, Southampton SO14 3ZH, UKb University of Hohenheim, Landesanstalt fur Landswirtschaftliche Chemie (710), 70593 Stuttgart, Germany

c Geosciences Montpellier, CNRS-Universite de Montpellier II, Place E. Bataillon, 34090 Montpellier Cedex 5, Franced University of Mainz, Department of Geosciences, Becherweg 21, 55099 Mainz, Germany

e Environmental Analytical Geochemistry, Department of Earth Sciences, The University of Queensland, Brisbane, Qld 4072, Australiaf University of Florida, Department of Geological Sciences, 241 Williamson Hall, Gainesville, FL 32611, USA

g CANTEST LTD., 309-267 West Esplanade, North Vancouver, BC V7M 1A5, Canadah State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China

i ALS Analytica AB, Aurorum 10, 977 75 Lulea, Swedenj Department of Geology, State Key Laboratory of Continental Dynamics, Northwest University, Xi’an 710069, China

Received 14 June 2007; received in revised form 6 August 2007; accepted 10 August 2007Available online 15 August 2007

bstract

Ten international laboratories participated in an inter-laboratory comparison of a fossil bone composite with the objective of producing a matrixnd structure-matched reference material for studies of the bio-mineralization of ancient fossil bone. We report the major and trace elementompositions of the fossil bone composite, using in-situ method as well as various wet chemical digestion techniques.

For major element concentrations, the intra-laboratory analytical precision (%RSDr) ranges from 7 to 18%, with higher percentages for Ti and. The %RSDr are smaller than the inter-laboratory analytical precision (%RSDR; <15–30%). Trace element concentrations vary by ∼5 ordersf magnitude (0.1 mg kg−1 for Th to 10,000 mg kg−1 for Ba). The intra-laboratory analytical precision %RSDr varies between 8 and 45%. Theeproducibility values (%RSDR) range from 13 to <50%, although extreme value >100% was found for the high field strength elements (Hf, Th, Zr,b). The rare earth element (REE) concentrations, which vary over 3 orders of magnitude, have %RSDr and %RSDR values at 8–15% and 20–32%,

espectively. However, the REE patterns (which are very important for paleo-environmental, taphonomic and paleo-oceanographic analyses) are

uch more consistent.These data suggest that the complex and unpredictable nature of the mineralogical and chemical composition of fossil bone makes it difficult to

et-up and calibrate analytical instruments using conventional standards, and may result in non-spectral matrix effects. We propose an analyticalrotocol that can be employed in future inter-laboratory studies to produce a certified fossil bone geochemical standard.

2007 Elsevier B.V. All rights reserved.

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eywords: Chemical composition; Biogenic phosphate; Reference material; Fo

. Introduction

There has been increasing interest over the last three decadesn using biogenic phosphate in human prosthetic implants [1], to

∗ Corresponding author. Tel.: +44 23 8059 6467.E-mail address: vmcc@noc.soton.ac.uk (V. Chavagnac).

1 Present address: CNRS-University of Paul Sabatier, LMTG, 14 Avenuedouard Belin, 31400 Toulouse, France.

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003-2670/$ – see front matter © 2007 Elsevier B.V. All rights reserved.oi:10.1016/j.aca.2007.08.015

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revent leakage of material from radioactive nuclear waste sites2], as remediation material for heavy metal polluted land [3–5],s a proxy in paleo-oceanographic studies [6–15] and in geo-hemical analyses in archaeology and palaeontology [16–21].n the field of earth sciences, the study of biogenic phosphates

as increased over the last few years because they can providealuable information on the pore water chemical compositiont the time of their mineralization/fossilisation, enabling thessessment of paleo-environmental changes [6–9,15,22].

1 Chimica Acta 599 (2007) 177–190

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Table 1List of laboratories and instrumentation

Laboratory ID Instrument

A ICP-OESB ICP-MSC SF-ICP-MSD ICP-MSE ICP-OESF ICP-MSG SF-ICP-MSH ICP-MSI ICP-MSJ LA-ICP-MSK ICP-MSLM

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A major problem in studies of geochemical biogenic phos-hate is the lack of well-characterised reference materials thatre closely matched in matrix (chemical composition and min-ralogical structure) to the sample being analysed. The closesteference materials currently available to the community arerovided by the National Institute of Standards and Technol-gy (NIST, USA) as (a) a phosphate rock, i.e. NIST SRM 120clorida Phosphate or (b) modern bone (bone ah NIST SRM 1400r bone meal NIST SRM 1486). Modern bone (SRM 1400 and486) is composed of carbonated apatite, whereas ancient bonesre typically fluorinated (carbonate) apatites. The concentrationf many elements of interest such as REE and U in SRM 1400ay be 4–5 orders of magnitude lower than those commonly

ound in ancient bio-apatites [22,23]. SRM 1400 is thereforeoorly suited as a standard material for comparison with ancientio-apatites (particularly bones). The bulk composition of NISTRM 120c is carbonated fluorapatite and is analogous miner-logically to ancient bio-apatites. In addition, the concentrationf elements such as the REE and U in NIST SRM 120c isomparable to those found in ancient bio-apatites. However,ncient bio-apatites are typically multi-minerallic, with abun-ant authigenic mineral phases present both within large porepaces in cancellous bone, and disseminated throughout smallerascular pores, making their physical separation from apatitextremely difficult. As the mineral suite present in any fos-il bone is frequently diverse and generally unknown prior tonalysis, chemical separation of apatite is also compromised.n summary, analytical and particularly preparation protocolseveloped and tested against existing certified reference materi-ls may not be appropriate for extension to ancient bio-apatites.

NIST SRM 120c is therefore a useful reference material in theontext of ancient bio-apatites. However, the crystal structuref sedimentary apatites is very different to that of fossil bio-patites. This is a problem because recent studies have shownhat non-spectral matrix effects can have a detrimental influencen the accuracy and reproducibility of element concentrationnalysis.

Here, we report the first results of chemical composition onproposed reference material composed of fossil bio-apatites

bones) derived from a range of sedimentary environments,hich were acquired through an inter-laboratory exercise. Weave characterised this material for major and trace elementoncentrations using in-situ and wet chemical techniques. Thisriginal objective of this study was to generate a fossil bonetandard that could be distributed to laboratories active in thetudy of the geochemistry of ancient biogenic phosphates.

. Experimental design

The study included 10 separate laboratories from eight dif-erent countries. Each laboratory received 3 g of a fossil boneomposite, which was made in Southampton from a diverseet of fossil bone samples (see below). The identification let-

er along with the instruments used by each laboratory is listedn Table 1. In most cases, laboratories used either inductivelyoupled plasma-optical emission spectroscopy (ICP-OES), andnductively coupled plasma-quadrupole or sector field mass

msmr

ICP-MSICP-OES

pectrometry (ICP-MS and SF-ICP-MS). Only, laboratory J usedaser ablation ICP-MS (LA-ICP-MS). The purpose of this studys to characterise a matrix-structure-matched standard for fossilone that could be used as an independent standard to assessccuracy and precision on major and trace element analyses onhis type of material.

.1. Sample preparation, distribution and storage

We produced ∼400 g of a fossil bone composite sample ofncient bio-apatite composed of fossil bone apatite and asso-iated authigenic and detrital minerals. The bones within theample are derived from different environments (marine and ter-estrial) chosen to reflect a wide range of depositional settingsnd associated mineralogy (e.g., authigenic minerals). The fossilones were collected in sedimentary formations aged between5 and 180 Myr old. We believe that a fossil bone compos-te approach is more suitable as a reference material than aarge single fossil bone based on the following arguments. First,ossil bones can contain a wide range of authigenic mineralssuch as carbonates, oxides, silicates and sulphates). Bio-apatite,uthigenic and detrital phases are typically intimately associ-ted on the micron scale in fossil bones and (to a lesser extent)eeth and mechanical separation is generally impossible. The

ineralogical composition of fossil bone samples is generallynknown prior to dissolution in the majority of cases. Second,ossil bones derived from different animals and preserved in dif-erent environments are characterised by distinct chemical andineralogical compositions [24]. Hence, unless a wide range

f standards were produced that were characteristic of all theossible fossil bone occurrences, any single sample would beecessarily unrepresentative of the range in possible composi-ions.

XRD analyses of the fossil bone composite powder indicatehat the major mineral is flourapatite with relatively low carbon-te content. Detrital quartz and authigenic calcite are only other

inerals present in concentrations greater than 1% of the total

ample and thus clearly identified on XRD diffractograms. Usingacroscopic observation, we also identified pyrite, clay and fer-

omanganese oxides. The fossil bone composite was prepared by

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nitially crushing large chunks of bone, adhering sediment andssociated authigenic minerals using a tungsten carbide rock-rusher. Sub-samples were then powdered in an agate ball-millt 9000 rpm for 45 min. The powders from each sub-sample werehen combined and mixed in a previously cleaned glass jar fortorage. This jar was then agitated on a shaker table to obtain aomogeneous powder. A sub-sample of ∼3 g was then sent toach laboratory for geochemical analysis.

.2. Statistical treatment of the data

The resulting data are expected to be normally distributedo in principle “outlier tests” such as Grubbs’ test for out-ying mean and Cochran’s test for outlying variance can bepplied. However, considering the novelty of the material anal-sed and the small number of laboratories participating perarticular element in this study, it is dangerous to remove val-es from the data set on statistical grounds alone. Hence, noata points have been removed for this reason alone. Outlyingata points were only removed from subsequent statistical anal-ses when a clear scientific reason for the outlying results wasdentified. Each of these removals is justified explicitly withinection 4.

The statistical analysis is performed using one-way analy-is of variance (ANOVA) coefficients. This analytical schemes equivalent to that commonly used in inter-laboratory analyt-cal studies for geological samples, which follow (to differentxtents) the ISO standard 1994–5725. This technique providesn estimate of the gross average, the repeatability, the repro-ucibility, the inter-laboratory variance, and the intra-laboratoryepeatability variance. The relevant equations are detailed ineinberg [25].

Repeatability and reproducibility are defined as the close-ess of agreement between two measurements obtained under,espectively, intra-laboratory conditions (repeatability) andnter-laboratory conditions (reproducibility). The repeatabilitynd reproducibility limits are defined at the 95% confidenceevel, being 2.8 times their respective standard deviations asetermined by Nilsson et al. [26].

. Analytical techniques

.1. Laser ablation inductively coupled plasma masspectrometer (LA-ICP-MS)

A New Wave Research UP-213 (wavelength = 213 nm) laserystem combined with an Agilent 7500ce ICP-MS was used ataboratory J. Prior to analysis, the sample material was furtherround in an agate mortar and pressed into a pellet. The sam-le was ablated in lines. Laser ablation parameters were: lineiameter = 100 �m, speed = 20 �m s−1, repetition rate = 10 Hz,nergy density = 2.24 J cm−2, and He–Ar mixture carrier gas.lasma torch conditions were optimized so that ThO/Th ratios

ere <0.5%. The NIST Standard Reference Material (SRM)12 glass (GeoReM preferred values: http://georem.mpch-ainz.gwdg.de/) was used for calibration. Calcium, measured

s 43Ca, was the internal standard element for each analysis.

absi

ica Acta 599 (2007) 177–190 179

ccuracy of the results was tested by the analyses of the USGSeference glass BCR-2G [27].

.2. Sample dissolution procedure

In order to facilitate reproducible comparisons, each labora-ory was encouraged to follow a common chemical procedure forhe total digestion of the fossil bone material, which is describedelow. However, when this was not possible, other wet dissolu-ion techniques were used.

For laboratories A, B, C, D, K, and M, a weighed amountf the fossil bone material was fully dissolved using a two-tage sequential dissolution procedure. The first step consistsf adding 10 ml of 3 M HNO3 to sample in a sealed 17 mlavillex® Teflon® beaker that was left on a hot plate at 130 ◦Cor 24 h. The beaker was then centrifuged and the supernatantas transferred to another Teflon® beaker. The residue was

hen rinsed three times with ultra-pure water. The supernatantas evaporated to dryness and converted to the chloride formy adding 15 ml of 6 M HCl. A mixture of concentrated HF:NO3 (3:1 proportion) was added to the residue from the initialNO3 digestion and the sealed Teflon® beaker was left for aeriod of 2 days on hotplate at 130 ◦C. The solution was driedown and converted to chloride form by adding 10 ml of 6 MCl. The two 6 M HCl solutions were then combined and thor-ughly mixed to ensure a homogeneous solution. Laboratories

and M followed the same sequential dissolution procedureut used Ultra Clave III high pressure microwave digestionystem (MWS GmbH, Leutkirch, Germany) with 10 ml PFAigestion tubes rather than sealed Savillex® Teflon® beaker.hen high-quality HCl was not available, the laboratory usedNO3.A microwave apparatus was used by laboratories E andto fully dissolve the fossil bone material as described in

etails by Engstrom et al. [28]. Approximately 250 mg of sam-le was weighed and mixed with a reagent mixture composedf 5 ml concentrated HNO3, 0.5 ml H2O2, and 0.1 ml concen-rated HF. The sample was digested at 600 W in 60 min using

microwave digestion unit (MARS-5, CEM Microwave Cor-oration, Matthews, USA) equipped with 12 perfluoroalkoxyPFA)-lined vessels (ACV 125) with safety rupture membranesmaximum operating pressure 1380 kPa). After cooling to roomemperature, sample digests were transferred to graduated auto-ampler tubes. The lids and inner surfaces of the digestionessels were rinsed with approximately 3 ml of ultra-pure waternto the auto-sampler tubes, followed by ultra-pure water addi-ion to 10.0 ± 0.1 ml. This digestion resulted in transparentellow solutions without any visible solid residues for any ofhe materials tested.

The sample digestion procedure employed at laboratory Has performed on three batches of ∼100 mg each and broadly

ollowed the procedure described in Ionov et al. [29]. The fossilone samples were dissolved twice on a hot plate at 150 ◦C with

mixing of 48% HF/HClO4 (2.5:1) for 48 h in closed Teflon®

eakers. After evaporation the samples were subjected to threeteps of evaporation with decreasing HClO4 quantities and atncreasing temperatures up to 180 ◦C to remove fluorides. They

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ere then dissolved in 2% HNO3 and diluted shortly beforenalysis to a final dilution factor of ∼40,000.

Laboratories F, I and L used a Teflon® bomb for the bulk dis-olution of the fossil bone material. Approximately 50–100 mgf sample powder was weighed into a Teflon® bomb, andoistened with a few drops of ultra-pure water. A mixture of

oncentrated HF:HNO3 was then added in a 1:1 or 3:1 propor-ion and the sealed bomb heated in an oven at 190 ◦C. After8 h, the bomb was opened and the solution was evaporated onhotplate at 110 ◦C. The residue was then treated twice withml concentrated HNO3. The resultant salt was re-dissolved bydding 3 ml 30% HNO3, resealed and heated in the bomb at90 ◦C for 24 h. The solution was then diluted to 100 g with 2%NO3 for ICP-MS analyses.Laboratory L employed a lithium metaborate fusion for bulk

ecomposition of the fossil bone standard for the determinationf major cations (i.e. Mg, Na, Si, Ca, Ti, P, Al, Mn, Fe and K).amples were fused with lithium metaborate (1:4 sample/flux)

n graphite crucibles and re-dissolved in 10% HNO3, containingppm Lutetium as internal standard, prior to direct Si analysisy ICP-OES. The lithium metaborate fusion method allows for

he determination of Si as no Si is lost (as SiF4) during the sampleissolution, compared to HF/HNO3/HCl digestions.

Up to three different bulk dissolutions were performedy each laboratory, with five replicate analyses to assess

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able 2ajor element concentration determined by each laboratory

aboratory ID Repeats Na% Ca% Mg% A

15 Mean 0.56 23.83 0.35 1Median 0.56 23.93 0.35 1σ 0.01 0.65 0.01 0%RSD 2 3 2 2

15 Mean 0.51 25.87 0.30 1Median 0.50 25.96 0.30 1σ 0.02 0.73 0.01 0%RSD 4 3 3 2

9 Mean 0.54 26.78 0.32 0Median 0.53 26.77 0.32 0σ 0.03 0.15 0.00 0%RSD 6 1 2 2

15 Mean 0.53 25.88 0.34 0Median 0.52 26.04 0.34 0σ 0.01 0.42 0.00 0%RSD 1 2 1 1

10 Mean 0.51 n.d. 0.41 nMedian 0.51 n.d. 0.41 nσ 0.01 n.d. 0.03 n%RSD 2 n.d. 8 n

3 Mean 0.66 24.40 0.33 0Median 0.60 24.30 0.33 0σ 0.05 0.26 0.01 0%RSD 7 1 2 2

15 Mean 0.55 26.30 0.35 nMedian 0.55 26.08 0.35 nσ 0.00 0.41 0.01 n%RSD 0 2 3 n

e report the mean, median, standard deviation (σ), and percentage relative standard

ica Acta 599 (2007) 177–190

he reproducibility, accuracy and precision of the chemicalnalyses.

.3. Inductively coupled plasma optical emissionpectrometer analyses (ICP-OES)

An aliquot of the product of each dissolution experiment,orresponding to ∼8 to 10 mg of the original bone compos-te, was either dried down on hot plate and then taken up with% HNO3 or directly diluted with 2% HNO3 in preparationor ICP-OES analyses. Dilution factors vary between 1000 and300. ICP-OES measurements were calibrated using either aatrix-matched international rock standard, NIST 120c (phos-

hate rock) which was prepared at different dilution factors toover the entire concentration range of the sample, or othernternational rock standards.

.4. Inductively coupled plasma mass spectrometernalyses (ICP-MS quadrupole and sector field)

Following complete sample dissolution, a weighed aliquot

f the fossil bone solution was evaporated to dryness and re-issolved in 2% HNO3 (spiked with 10 ppb In and Re for internalorrection). A dilution factor of 2000–400,000 (depending onhe instrument) was applied to each sample and rock standards

l% P% K% Ti% S% Mn% Fe% Si%

.07 8.22 0.23 0.08 0.35 0.82 8.77 n.d.

.08 8.25 0.23 0.08 0.35 0.82 8.85 n.d.

.03 0.26 0.00 0.00 0.02 0.02 0.26 n.d.3 1 3 5 2 3 n.d.

.02 9.86 0.23 0.13 n.d. 0.79 8.48 n.d.

.01 9.86 0.23 0.13 n.d. 0.79 8.57 n.d.

.02 0.18 0.01 0.01 n.d. 0.02 0.20 n.d.2 3 5 n.d. 2 2 n.d.

.81 8.53 0.17 0.02 0.39 0.72 7.81 n.d.

.82 8.49 0.17 0.02 0.39 0.73 7.85 n.d.

.02 0.06 0.01 0.00 0.02 0.01 0.15 n.d.1 3 1 4 1 2 n.d.

.81 9.74 0.17 0.02 0.35 0.82 7.77 n.d.

.81 9.71 0.17 0.02 0.36 0.82 7.76 n.d.

.01 0.06 0.00 0.00 0.01 0.01 0.08 n.d.1 2 3 3 1 1 n.d.

.d. n.d. 0.23 0.05 n.d. 0.79 n.d. n.d.

.d. n.d. 0.23 0.05 n.d. 0.79 n.d. n.d.

.d. n.d. 0.05 0.00 n.d. 0.04 n.d. n.d.

.d. n.d. 23 9 n.d. 5 n.d. n.d.

.92 9.93 0.20 0.08 n.d. 0.77 8.09 4.51

.93 9.91 0.20 0.08 n.d. 0.76 8.05 4.56

.02 0.06 0.00 0.00 n.d. 0.01 0.11 0.091 2 6 n.d. 2 1 2

.d. 9.55 0.20 n.d. n.d. 0.77 7.81 n.d.

.d. 9.46 0.21 n.d. n.d. 0.79 7.66 n.d.

.d. 0.25 0.01 n.d. n.d. 0.03 0.52 n.d.

.d. 3 5 n.d. n.d. 4 7 n.d.

deviation (%RSD); n.d.: not determined.

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V. Chavagnac et al. / Analytica

o avoid detector saturation. This solution was analyzed for metalnd large ion lithophile elements by ICP-MS and SF-ICP-MS.pectral interferences (resulting from the plasma gas, solventnd major elements from the sample matrices) have long beenecognized as one of the major obstacles to obtaining accurate

ata by ICP–MS. A variety of mechanisms have been employedn an effort to improve the data accuracy. This includes the use oflternative plasma gases, ‘cold plasma’ conditions, mathemat-

ig. 1. Compilation of the mean results with one standard deviation from theajor element composition in fossil bone material for each laboratory. Theeighted mean and its standard deviation are also reported. Elements Ca, P ande are reported in (a); Al, Mn and Na in (b); Mg, S, K and Ti in (c).

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ica Acta 599 (2007) 177–190 181

cal corrections, collision (reaction) cell techniques and highass resolution. A matrix-matched standard can also be used

ig. 2. Histogram of replicate measurements from each laboratory for the anal-sis of Na in (a), Mg in (b) and Al in (c) in the fossil bone material. The intervalf Al concentration covered by each bar is 0.02%, while being 0.01% for Mg anda. The solid curve represents the normal distribution of the data. The dotted

ine indicated the mean value and the tick line the weighted average. Note thata and Mg concentration distribution is normal while Al histogram is bi-modal.

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he laboratories in this study calibrated their instrument againstseries of other (non-matrix matches) international rock stan-ards (AGV-1, AGV-2, BCR-2, BIR-1, JB-3, JGB-1, JA-1, JA-2,HVO-2, W-2 and JB-1A), multi-element synthetic calibration

olutions, and/or other reference materials such SRM1640 (Nat-ral water) and SRM 1486 (Bone meal). The standards wereypically run before, during, and after each group of analy-es. Ba/REE oxide and hydroxide interference species were

orrected for based on the artificial peaks found in four addi-ional elemental standards (Ba, Ce, Pr–Nd, and Sm–Tb). Theata processing procedures employed by the different labora-ories included linear drift correction, interference corrections,

able 3ummary of the statistic parameters obtained on the major and trace element compos

lement n p Weighted mean σ2 1σ %RSD Gross average G

ajor element in wt.%Na 79 6 0.53 0.00 0.02 4 0.53Mg 79 6 0.37 0.00 0.04 10 0.34Al 54 4 0.96 0.02 0.14 14 0.94P 69 5 9.14 0.57 0.75 8 9.59K 79 6 0.22 0.00 0.03 14 0.20Ca 69 5 25.44 1.27 1.13 4 25.64Ti 64 5 0.09 0.00 0.05 50 0.07S 39 3 0.36 0.00 0.02 6 0.36Mn 79 6 0.79 0.00 0.03 4 0.79Fe 69 5 8.13 0.22 0.47 6 8.16

race element in mg kg−1

Cr 51 4 23.1 39.9 6.3 27 19.83Co 67 5 14.2 1.0 1.0 7 13.95Ni 67 5 25.0 48.7 3.6 14 27.91Cu 82 6 19.4 4.7 2 2 11 18.23Zn 92 7 74 129 11 15 72Mo 35 3 4.7 0.7 0.8 17 4.21Ba 123 10 6958 2366844 1538 22 6540 2Sr 114 9 1492 6989 84 6 1462V 61 5 66.9 46.1 6.8 10 65.14Y 91 7 504 9622 98 19 543Li 57 4 8.9 1.0 1.0 11 9.02B 44 4 22.4 13.8 3.7 17 22.47Be 71 6 7.40 0.4 0.7 9 8.28Cd 30 2 1.3 0.0 0.0 2 1.3Sc 61 5 21.1 1.8 1.3 6 20.7Rb 91 7 7.5 0.9 1.0 13 7.5Zr 90 7 100 557 24 24 77Nb 82 6 3.4 1.4 1.2 35 2.0Cs 91 7 0.4 0.0 0.0 10 0.4Hf 96 7 1.6 0.5 0.7 43 1.0Ta 65 5 0.4 0.0 0.2 42 0.2Pb 95 7 30.6 24.0 4.9 16 31.1Th 90 7 1.6 0.1 0.3 21 1.5U 90 7 25.2 4.6 2.1 9 25.2La 116 9 336 456 21.4 6 327.5Ce 101 9 634 1350 36.7 6 613Pr 107 9 70 11.8 3.4 5 69Nd 107 9 283 285 16.9 6 285Sm 107 9 61 8 3 5 59Eu 107 9 16.2 0.8 0.9 6 15.9Gd 107 9 81 49 7 9 78Tb 107 9 11.7 0.6 0.8 7 11.6Dy 107 9 74 26 5 7 73Ho 107 9 15.9 1.5 1.2 8 15.5Er 107 9 41 7 3 7 40Tm 97 8 5.2 0.6 0.8 15 5.1Yb 107 9 29.2 8.9 3.0 10 28.4Lu 107 9 3.9 0.1 0.3 7 3.9

: number of repeats; p: number of laboratory. Values of gross average, repeatabilittandard deviation; %RSD: percentage relative standard deviation; r: repeatability;eviation; R: reproducibility; SR: reproducibility variance; %RSDR: relative reproduc

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ica Acta 599 (2007) 177–190

lank subtraction, calibration with international standards, anddilution correction.

. Results and discussion

.1. Major element compositions

Table 2 reports the element concentration determined by each

ition of the fossil bone material

ross variance r Sr %RSDr R SR %RSDR

0.0009 0.06 0.00 12 0.09 0.00 160.0014 0.06 0.00 16 0.11 0.00 300.0152 0.07 0.00 7 0.40 0.02 410.5221 0.72 0.07 8 2.23 0.63 240.0014 0.08 0.00 35 0.11 0.00 501.4585 1.92 0.47 8 3.65 1.70 140.0018 0.02 0.00 21 0.13 0.00 1470.0006 0.06 0.00 18 0.08 0.00 220.0018 0.09 0.00 12 0.12 0.00 160.2743 0.89 0.10 11 1.57 0.32 19

39.8 8.1 8.3 35 20 52 871.2 1.7 0.4 12 3.4 1.4 24

12.9 3.1 1.2 12 11 16 455.0 2.2 0.6 11 7 6 35

125 10 13 13 34 174 450.7 1.1 0.2 24 2.8 1.0 59

562220 1754 392688 25 4691 2807105 677342 122 1907 8 251 8031 17

42.24 5.3 3.65 8 20 53 308976 47 283 9 287 10474 57

1.44 2.4 0.8 27 3.6 1.7 4112.92 2.4 0.7 11 11.7 17.4 520.70 1.4 0.3 19 2.5 0.8 340.0 0.2 0.00 13 0.2 0.0 131.5 2.0 0.5 9 3.7 1.7 181.0 1.1 0.2 15 3.1 1.2 41

473 19 45 19 65 547 661.5 1.5 0.3 45 3.7 1.7 1080.0 0.1 0.0 29 0.2 0.0 400.4 0.4 0.0 27 2.0 0.5 1240.0 0.1 0.0 13 0.4 0.0 119

22.6 3.5 1.5 11 14.3 26.2 470.1 0.7 0.05 40 1.11 0.16 686.2 4.0 2.0 16 7.3 6.9 29

553 35 156 10 69 603 202098 85 925 13 133 2271 21

23 10 13 15 14 24 20510 43 240 15 66 549 2317 9.1 10.6 15 12.0 18.2 201.4 2.2 0.6 13 3.4 1.5 21

61 10 13 13 23 68 290.8 1.4 0.2 12 2.6 0.8 22

35 9 11 13 17 39 241.8 2.0 0.5 12 4.0 2.0 25

10 5 3 13 9 11 230.3 0.4 0.0 8 1.6 0.3 32

10.2 3.7 1.8 13 9.4 11.4 320.1 0.5 0.04 13 1.0 0.1 26

y and reproducibility are based on the ANOVA coefficients. σ2: variance; σ:Sr: repeatability variance; %RSDr: percentage relative repeatability standardibility standard deviation.

aboratory as a mean of up to 15 runs with standard devia-ions (1σ) and percentage relative standard deviation (%RSD).he standard deviation obtained by the different laboratories isighly variable according to the element analysed, but the %RSD

V.Chavagnac

etal./Analytica

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icaA

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(2007)177–190

183

Table 4Trace element concentrations determined by each laboratoryLaboratory ID Repeats Cr Co Ni Cu Zn Mo Ba Sr V Y Li B Be Sc Cd Rb Zr Nb Cs Br Hf Ta Pb Th U As W

A 15 Mean 12.7 24.5 14.9 83.8 4610 1356 74.5 26.11σ 0.8 0.9 0.5 2.8 880 36 3.0 0.8%RSD 6 4 3 3 19 3 4 3

D 13 Mean 5966 1602 9.2 48.5 4.1 0.50 1.0 0.47 28.7 2.0 21.41σ 1254 84 0.4 7.3 1.3 0.05 0.3 0.03 0.8 0.1 0.7%RSD 21 5 4 15 31 9 26 6 3 4 3

B 15 Mean 14.2 36.9 20.8 75.2 4.9 7946 1441 519 8.2 17.8 7.2 20.3 1.3 7.7 91.1 1.8 0.39 1.6 0.23 33.8 1.6 28.31σ 0.7 3.6 1.3 4.4 0.6 375 51 12 0.5 1.0 0.3 0.7 0.1 0.3 3.5 0.1 0.02 0.1 0.03 1.1 0.1 1.5%RSD 5 10 6 6 12 5 4 2 7 6 5 4 6 4 4 4 5 7 11 3 5 5

E 9 Mean 4606 1331 56.0 513 7.8 19.6 56.91σ 71 6 0.8 5 0.2 0.3 0.6%RSD 2 0 1 1 3 2 1

G 15 Mean 11.2 13.4 20.4 16.6 62.8 3.4 4561 1467 61.1 523 8.2 24.3 9.0 21.9 1.3 5.9 58.9 0.44 0.4 7.1 0.45 27.4 1.2 26.1 32.0 0.91σ 0.3 0.2 0.5 0.3 1.2 0.1 56 22 0.7 4 0.2 0.8 0.1 0.6 0.0 0.1 1.3 0.01 0.1 0.5 0.03 0.7 0.1 0.4 1.0 0.0%RSD 2 2 2 2 2 3 1 2 1 1 2 3 1 3 2 2 2 3 18 6 6 3 5 1 3 4

F 17 Mean 23.8 15.1 28.2 20.0 57.3 7743 1477 65.7 605 9.9 8.8 20.2 7.6 102.4 2.0 0.43 1.9 0.20 29.5 1.5 25.21σ 3.9 0.7 1.7 0.9 3.4 487 41 1.9 17 1.2 0.8 0.8 0.2 12.6 0.1 0.01 0.2 0.01 1.1 0.4 1.0%RSD 16 5 6 4 6 6 3 3 3 12 9 4 2 12 4 1 13 4 4 30 4

H 15 Mean 7876 1499 670 7.4 80.2 1.7 0.41 0.83 0.07 28.1 1.8 23.81σ 184 16 6 0.1 0.8 0.0 0.01 0.02 0.00 0.3 0.2 0.4%RSD 2 1 1 2 1 2 3 3 4 1 13 2

I 5 Mean 25.0 14.9 26.4 19.2 68.6 4.8 7754 1510 65.0 636 24.6 8.4 22.8 7.5 106.2 1.9 0.37 1.7 0.12 26.9 1.22 25.91σ 6.2 0.4 1.0 0.3 1.1 0.1 443 42 1.7 16 0.8 0.5 1.0 0.1 8.4 0.1 0.01 0.2 0.00 0.4 0.03 0.7%RSD 25 3 4 2 2 1 6 3 3 2 3 6 4 2 8 3 2 12 2 1 3 3

K 15 Mean 378 23.81σ 32 0.4%RSD 8 2

J 10 Mean 89.4 6545 1494 9.9 8.5 7.2 0.4 1.1 25.71σ 7.3 865 43 1.2 0.6 1.0 0.1 0.2 3.5%RSD 8 13 3 13 7 14 18 18 14

L 3 Mean 21.9 13.7 23.1 22.2 76.7 5.4 4420 1330 56.2 851 7.7 18.6 60.1 2.2 10.7 24.2 1.04 0.57 0.41 0.09 25.6 3.1 21.4 54.4 54.4 0.441σ 0.3 0.3 0.5 1.5 2.8 0.0 67 19 1.1 17 0.5 0.6 1.4 0.2 0.2 0.7 0.01 0.04 0.02 0.00 0.6 0.1 0.5 1.6 1.6 0.03%RSD 1 2 2 7 4 0 2 1 2 2 6 3 2 9 2 3 .1 6 6 5 2 3 2 3 3 8

M 15 Mean 22.5 19.8 18.2 70.2 8130 40.61σ 1.4 1.0 0.6 0.8 272 2.4%RSD 6 5 3 1 3 6

We report the mean, standard deviation (σ), and percentage relative standard deviation (%RSD).

1 Chim

vlobS

adaaMpt

disudmaah

FmP

84 V. Chavagnac et al. / Analytica

alue is generally better than 5%. The exception is provided byaboratory J, which employed the LA-ICP-MS technique. Lab-ratory L provides the sole data of Si concentration on the fossilone composite. Further Si analyses are needed to constrain thei concentration.

Fig. 1 illustrates the mean and 1σ values for each laboratorys well as the weighted mean and 1σ values obtained for the fullataset. By way of example, the statistical distributions of Al, Mgnd Na concentrations in the fossil bone material are presented

s histograms in Fig. 2. The distributions are normal for Na andg, but the Al concentration distribution shows two separate

eaks. It is apparent that differences in set-up, dissolution pro-ocols and calibration procedures at different laboratories yield

a

as

ig. 3. Compilation of the mean results with one standard deviation from the trace eean and its standard deviation are also reported. Elements Ba, Sr and Y are reportedb, U and Sc in (e); Th, Cd, and Cs in (f).

ica Acta 599 (2007) 177–190

ifferent results. In particular, the Al concentration is highern laboratories that used a large amount of HF to dissolve theample in comparison to laboratories (e.g., E and G) whichsed microwave digestion with a limited amount of HF. Similarifferences are also observed for Ti concentrations. Note thatajor element concentrations of international rock standards

re usually determined by X-ray fluorescence and/or ICP-OESfter alkali fusion (e.g., lithium metaborate) as this technique isighly effective in dissolving all major rock-forming silicates

nd accessory refractory minerals.

The complete results of the data treatment performed inccordance with the inter-laboratory statistics (weighted mean,tandard deviation (1σ), percentage relative standard deviation

lement composition in fossil bone material for each laboratory. The weightedin (a); B, Li, Br and Mo in (b); Zn, Cr, Ni, Cu, Co in (c); Nb, Hf and Ta in (d);

Chim

(dia%(toecdie

vuitbr

4

e

McdT

eAvoit%baadiOaCe

Fci

V. Chavagnac et al. / Analytica

%RSD), repeatability, intra-laboratory variance (Sr), repro-ucibility and inter-laboratory variance (SR) values) are reportedn Table 3. The intra-laboratory analytical precision ranges over-ll from 7 to 18%, with higher values obtained for Ti and K. TheRSDr are smaller than the inter-laboratory analytical precision

%RSDR), which can be as high as 146% for Ti. The reason forhis lack of precision cannot be fully assessed due to the lackf matrix-matched standard that is fully certified for its majorlement composition. However, there is clear evidence, in thease of Al and other refractory elements (such as Ti), that theissolution procedure has a major impact on the reproducibil-ty value, even though the intra-laboratory repeatability remainsxcellent.

We believe that the relatively large inter-laboratory %RSDRalues (<15–30%) are likely due to the fact that instrument set-p was performed using different reference materials betweenndividual laboratories. As these reference materials do not con-ain the same structure and matrix composition as the fossilone composite, non-spectral matrix effects may influence theeported elemental concentrations.

.2. Trace element concentration

Data presented in Table 4 show the results of tracelement concentrations determined by ICP-OES, LA-ICP-

((

f

ig. 4. Histogram of all replicate measurements from each laboratory for the analysioncentration interval covered by each bar is 1, 20, 0.5 and 1 mg kg−1, respectively.ndicated the weighted mean value and the tick line the mean.

ica Acta 599 (2007) 177–190 185

S, ICP-MS and SF-ICP-MS from 10 laboratories. Theomplete results of the data treatment performed in accor-ance with the inter-laboratory statistics are reported inable 3.

The mean value and associated standard deviation for eachlement obtained by each laboratory are compiled in Fig. 3.s expected, the analysis of the fossil bone composite posedarying degrees of difficulty, which is reflected in the variabilityf the results (Figs. 3–5). The concentrations of trace elementn the fossil bone material vary by almost 5 orders of magni-ude (Tables 3 and 4). The intra-laboratory analytical precision

RSD is highly variable and varies from element to elementetween 8 and 45%. The spread of the data for Ba, taken asn example, is large and follows a bimodal distribution, whichgain is likely a reflection of variations in the dissolution proce-ure (Figs. 3 and 5). In contrast, the distribution of the data for Srs very narrow and follows a normal distribution (Figs. 3 and 4).verall, four elements (Sr, V, Y and Sc) show an intra-laboratory

nalytical precision below 10%, while eight elements (Co, Ni,u, Zn, B, Cd, Ta, Pb) have %RSD between 10 and 15%, fourlements (Rb, U, Zr, Be) between 15 and 20%, five elements

Mo, Ba, Li, Cs, Hf) between 20 and 30%, and three elementsTh, Cr, Nb) >30%.

We believe that these large differences likely reflect the dif-erent analytical procedures used to quantify the trace element

s of Sc in (a), Sr in (b), Co in (c) and Cu in (d) in the fossil bone material. TheThe solid curve represents the normal distribution of the data. The dotted line

1 Chim

ccrte(

Fac

tf

86 V. Chavagnac et al. / Analytica

oncentration, in addition to variations in the dissolution pro-edure noted earlier. The dispersion of the data in terms of

epeatability (r) and reproducibility (R) is not simply a func-ion of element concentration in the fossil bone material aslements present at both high and low concentrations such as Sr∼1500 mg kg−1) and Co (∼15 mg kg−1), display normal dis-

ig. 5. Histogram of all replicate measurements from each laboratory for thenalysis of Ni in (a), Ba in (b) and Li in (c) in the fossil bone material. The con-entration interval covered by each bar is 1, 100, and 0.2 mg kg−1, respectively.

e0

iessdat

brofcmaufttm(dmttfcFcFdlrtewc

4

(TwoaAad

aT

ica Acta 599 (2007) 177–190

ributions (Fig. 4). However, concentration may be an importantactor for some elements. For example, Th (Fig. 5) has lowestlement concentration of any element reported in this study at.37 ± 0.16 and one of the highest %RSDR values (119%).

Overall, there is considerable room for improvement in thenter-laboratory variability of many of the elements consid-red here, with one of the first objectives being to reduce theystematic differences between laboratories. An obvious firsttep would be to adopt a common dissolution procedure that isesigned to ensure complete dissolution of the fossil bone apatitend its associated authigenic minerals and which maintains allhe elements in a stable and long-standing dissolved state.

The reproducibility values (%RSDR) are highly variableetween elements, ranging from 13 to 124% (Table 3). Theseeflect, to a large extent, the complex and multi-minerallic naturef the fossil bone composite and highlights the potential dif-erences between ancient bio-apatites and existing standardsommonly used to set-up and calibrate the analytical instru-ents, and assess method errors. At present, we are unable to

ppraise the analytical capability and accuracy of the individ-al laboratories because the true chemical composition of theossil bone material is unknown. It is the results from this ringest, which provide the necessary element concentration rangeo address this aspect with forthcoming analyses. One of the

ajor issues is how effectively the high field strengths elementsHFSE; Th, Zr, Nb, Hf) are brought into solution during theissolution stage. HF is widely used to dissolve silicate-bearinginerals that contain significant amounts of HFSE. However,

he addition of HF to a Ca-rich solution leads to the forma-ion of calcium fluoride precipitate, which may scavenge HFSErom solution and thus lead to under estimate of the true con-entration of HFSE in the sample. This may be reflected inig. 6, which indicates that there is a very wide range of con-entrations determined for HFSE by the various laboratories.urther analyses of the fossil bone composite would help inefining threshold values below and above which analytical out-iers can be identified, and thus improve the presently very loweproducibility (%RSDR ∼40%). Finally, in any future attemptso reduce inter-laboratory dispersion in the measurements it isssential that a consensus is reached on how the instrument withhich the chemical composition will be determined is set-up and

alibrated. We will discuss this issue later on in this manuscript.

.3. Rare earth element (REE) concentrations

The results of REE concentrations determined by ICP-MSquadrupole and sector field) from 10 laboratories are given inable 5. Laboratories K and L obtained REE concentrationshich are generally 20–30% lower than those obtained from thether eight laboratories, although their Yb and Lu concentrationsre more similar to those determined by the other laboratories.lthough the reason for this discrepancy is unclear, their results

re sufficiently at variance to the majority of the results for their

ata to be excluded from the statistical treatment.

The complete results of the data treatment performed inccordance with the inter-laboratory statistics are reported inable 3. Fig. 7 shows the mean and 1σ values for each labo-

V. Chavagnac et al. / Analytica Chimica Acta 599 (2007) 177–190 187

Fig. 6. Histogram of all replicate measurements from each laboratory for the analysis of Th in (a), Hf in (b), Nb in (c), and Zr in (d) in the fossil bone material.The concentration interval covered by each bar is 0.1, 0.2, 0.2, and 5 mg kg−1, respectively. It is difficult to decipher whether some outliers imply the wide HFSEconcentration distribution on the fossil bone material. The data spread could be produced by the difficulty of stabilizing HFSE in a Ca-rich solution while using HFt

rfIhMcefttcmsaiohr

Aa

Rsabtu[

4

bsibtl

o dissolve in silicate mineral.

atory as well as the weighted mean and 1σ values obtainedor the full dataset. The REE concentrations determined by LA-CP-MS produce similar REE concentrations, but with a slightlyigher %RSD (10–15%) compared to those determined by ICP-S and SF-ICP-MS (1–5%). The precise determinations of REE

oncentration in the new fossil bone composite rely on interfer-nce corrections of mass interferences and oxide and hydroxideormation during the course of the analyses. In the first instance,he precision of the Ba analyses clearly affects the precision ofhe corrections due to the BaOH+ and BaO+ species. The REEoncentrations in the fossil bone composite range from a fewg kg−1 (HREE) to several hundred mg kg−1 (LREE), hence

ome compromises are required regarding the instrument set-upnd choice of sample dilution. In addition, Ba (the main interfer-ng element on REE masses) has concentrations of 1–3 ordersf magnitude higher than the REE. One effect of the oxide andydroxide interferences is that the HREE concentrations are less

eproducible between laboratories compared to the LREE.

Fig. 8 presents the REE patterns normalised to the Post-rchean Australian Shale Composite values (PAAS; [30]). In

ll cases, the fossil bone composite present a MREE enriched

tcce

EE patterns as characterised by (Gd/Yb)N = 1.47–1.82, amall positive Eu anomaly Eu/Eu* = 1.04–1.13, and a neg-tive Ce anomaly Ce/Ce* = 0.86–0.92. The close agreementetween the REE patterns and the relative REE concentra-ions are of particular significance as these are commonlysed parameters used in geochemical analyses of fossil bone6,13,14,19–22,24].

.4. Future recommendations

Further work is needed before the fossil bone composite cane used as an international standard. In particular, it is neces-ary to establish the number of elements that might usefully bencluded in a compilation of standard concentrations. It will thene possible to move towards common dissolution and analyticalechniques that will allow us to propose a set of values that haveevels of repeatability and reproducibility suitable for an interna-

ional fossil bone geochemical standard. Meanwhile, the isotopeomposition of strontium and neodymium in the fossil boneomposite has been also assessed through an inter-laboratoryxercise, whose results are presented elsewhere [31].

188 V. Chavagnac et al. / Analytica Chimica Acta 599 (2007) 177–190

Table 5REE concentration in the fossil bone material determined by each laboratory

Laboratory ID La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er I’m Yb Lu

G Mean 311 596 66 263 54 14.4 74 10.5 66 13.6 37.1 4.5 25.0 3.51σ 3 10 1 3 1 0.2 1 0.2 1 0.2 0.7 0.0 0.4 0.0%RSD 1 2 2 1 1 2 1 2 2 1 2 1 2 1

F Mean 340 631 71 293 61 16.0 71 11.6 70 15.3 38.0 4.9 28.0 3.91σ 4 9 2 6 2 0.4 2 0.4 2 0.6 1.4 0.2 1.1 0.2%RSD 1 1 2 2 3 3 3 3 4 4 4 4 4 4

H Mean 346 653 69 296 59 15.5 79 11.2 73 15.1 40.2 4.9 26.2 4.01σ 2 3 1 5 1 0.3 1 0.2 1 0.2 0.6 0.1 0.4 0.1%RSD 1 0 1 2 2 2 2 2 2 2 1 1 1 1

I Mean 348 630 73 285 61.3 15.9 81 11.1 72 16.1 39.1 4.8 28.0 3.71σ 2 13 1 6 2.2 0.5 2 0.3 2 0.5 1.1 0.1 0.8 0.1%RSD 1 2 2 2 4 3 3 3 3 3 3 3 3 4

K Mean 194 516 49 250 42 11.9 53 8.3 49 10.4 28.4 3.5 19.4 3.91σ 7 21 1 9 1 0.3 1 0.2 1 0.2 0.6 0.1 0.4 0.2%RSD 3 4 3 4 2 2 2 2 2 2 2 2 2 5

J Mean 351 667 70 291 59 15.5 77 11.0 74 15.1 39.8 28.1 4.01σ 37 86 10 45 9 2.1 10 1.3 9 1.8 4.5 3.1 0.5%RSD 10 13 15 16 15 14 12 12 12 12 11 11 11

C Mean 291 547 63 256 57 15.9 71 11.4 69 14.3 37.9 4.9 26.5 3.81σ 4 9 1 4 1 0.2 1 0.1 1 0.1 0.3 0.1 0.4 0.1%RSD 2 2 2 1 1 1 1 1 1 1 1 1 1 2

B Mean 326 618 72 303 61 17.6 93 12.5 80 16.2 42.8 5.3 32.4 4.51σ 9 19 3 12 3 0.6 4 0.4 3 0.5 1.9 0.2 1.5 0.2%RSD 3 3 4 4 5 4 4 3 4 3 4 3 5 5

D Mean 342 611 69 298 63 16.2 81 12.8 80 17.6 44.8 6.2 33.4 3.51σ 14 27 3 12 3 0.7 3 0.4 3 0.7 2.1 0.3 1.5 0.1%RSD 4 4 4 4 4 4 3 3 4 4 5 4 4 4

L Mean 209 327 44 177 37 9.7 49 7.7 48 11.2 31.1 4.8 24.2 3.71σ 3 5 1 3 1 0.1 1 0.2 1 0.3 0.5 0.2 0.6 0.1%RSD 2 1 2 2 2 1 2 2 1 2 2 4 2 2

W viatio

fwcsstfiacsdbdt[

edai

mscdiwlcc

liStptb

e report the mean, standard deviation (σ), and percentage relative standard de

We recommend a two-step procedure for the dissolution of theossil bone composite. The first step is an extraction/digestionith a 3–6 M HNO3 or HCl solution to completely dissolve the

arbonated hydroxyapatite. After centrifugation, the supernatanthould be transferred to a second beaker. If HNO3 was used, theupernatant should be evaporated to dryness and converted tohe chloride form by adding 6 M HCl. The residue from therst step should be dissolved with a 3:1 HF:HNO3 mixture insealed Teflon® savillex on a hotplate for ∼2 days to ensure

omplete dissolution of remaining material (largely silicate andulphate minerals). The solution should then be evaporated toryness and re-dissolved with 6 M HCl. The two 6 M HCl shoulde combined prior to geochemical analysis. Note, however, thatifferent dissolution procedure will be required of it is necessaryo isolate the component phases of fossil bone from one another11].

Recent studies have demonstrated that non-spectral matrix

ffects can have detrimental influence on the accuracy and repro-ucibility of element concentration during ICP-OES, ICP-AES,nd ICP-MS analyses. Hence, it is important that analyticalnstruments are calibrated with standards that closely mimic the

uwis

n (%RSD).

atrix of the samples of interest. At present there is no suitabletandard, which matches the matrix, structure and elemental con-entrations of ancient fossil bone. Therefore, it is important toevelop a consensus concerning how the analytical instruments set-up and calibrated. Until a fossil bone standard is availableith fully certified elemental concentrations, we encourage each

aboratory to use several international rock standards, whosehemical compositions are certified and cover the range andoncentration of elements in the fossil bone material.

We believe that the next stage in the process of estab-ishing the fossil bone composite as an international standards for representatives of interested laboratories to contact theouthampton authors (details given below) for a sample of

he bone composite. These individuals should then follow therotocol listed above and forward their data set to Southamp-on. Once this second stage of analyses is completed weelieve that it will then be possible to propose consensus val-

es for the elemental concentration of a suite of elementsithin the fossil bone composite of sufficient reproducibil-

ty and accuracy to allow it to be adopted as an internationaltandard.

V. Chavagnac et al. / Analytica Chimica Acta 599 (2007) 177–190 189

Fig. 7. Compilation of the mean results with one standard deviation from the trace emean and its standard deviation are also reported. Elements La, Ce and Nd are reporte

Fbc

5

ym

vcr

nvugt

o8

ETo

Wsiia

tut

ig. 8. PAAS-normalised REE patterns of the fossil bone material determinedy each laboratory. Note that laboratory K and L exhibit much lower REEoncentrations compared to other laboratories.

. Conclusions

Ten laboratories carried out major and trace element anal-ses on a new fossil bone composite, which is intended as aatrix/structure match standard for biogenic phosphate study.

Major element concentrations were determined with a %RSD

alue generally <5%. The intra and inter-laboratory analyti-al precision (%RSDr and %RSDR) are 7–18%, and <15–30%,espectively.

cbss

lement composition in fossil bone material for each laboratory. The weightedd in (a); Pr, Sm and Gd in (b); Eu Tb, Tm and Lu in (c); Dy, Er, Yb, Ho in (d).

Trace element concentrations vary by almost 5 orders of mag-itude (0.1–10,000 mg kg−1). The %RSDr is highly variable andaries from element to element between 8 and 45%. The val-es of reproducibility (%RSDR) are extremely variable, rangingenerally from 13 to <50%, with extreme value above 100% forhe high field strength elements (Hf, Th, Zr, Nb).

The rare earth element concentrations, which vary over 3rders of magnitude, present %RSDr and %RSDR values at–15% and 20–32%, respectively.

The REE patterns and intra-REE relationships (e.g., Ce andu anomalies, and MREE/HREE) show much better agreement.his is of particular relevance as the REE are important in studiesf fossil bone bio-mineralization.

The inter-laboratory comparability of the full dataset is low.e believe that this reflects the unusual nature of the fossil bone,

uch that the standards used to set-up and calibrate the analyticalnstruments are not matrix matched to the fossil bone compos-te. This, in turn, can lead to non-spectral matrix effects duringnalysis.

Although further work is needed before reference values forhe fossil bone composite can be finalised, this study has alloweds to identify the key problems that need to be addressed. Tohis, we have devised sample dissolution and analytical proto-

ol that we would advise interested laboratories to adopt. Weelieve that adoption of these protocols would allow the fos-il bone composite to be established as a certified geochemicaltandard.

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[[30] S.R. Taylor, S.M. McLennan, The Continental Crust: Its Composition and

90 V. Chavagnac et al. / Analytica

cknowledgements

This project is funded through NERC grant proposalE/C00390X/1. Kees de Groot (ECS, University of Southamp-

on) is greatly acknowledged for his support on the statisticalreatment of the data set. The authors would like to thank theomments from two anonymous reviewers.

ppendix A

A fraction of the fossil bone material powder can be obtainedy contacting: Dr. Clive N. Trueman, National Oceanographyentre, Southampton, University of Southampton, School ofcean and Earth Sciences, European Way, Southampton SO14ZH, UK.

Users are advised to contact him at trueman@noc.soton.ac.uko obtain ordering information. As the amount of the fossil boneowder exists only in limited amount, it should be requested byaboratories that have an active need for these materials and wisho contribute towards a better characterisation.

eferences

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[2] R.C. Ewing, L.M. Wang, in: M.J. Khon, J. Rakovan, J.M. Hughes(Eds.), Phosphates: Geochemical, Geobiological, and Materials Impor-tance (Review Mineralogy Geochemistry), Mineralogical Society ofAmerica and Geochemical Society, 2002, p. 673.

[3] H. Garelick, A. Dybowska, E. Valsami-Jones, J. Soils Sed. 5 (3) (2005)182.

[4] I.R. Sneddon, H. Garelick, E. Valsami-Jones, Min. Mag. 69 (5) (2005) 769.[5] I.R. Sneddon, M. Orueetxebarria, M.E. Hodson, P.F. Schofield, E. Valsami-

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37 (13) (2004) 2819.18] T.D. Price, J.H. Burton, R.A. Bentley, Archeometry 44 (2002) 117.19] C.A. Metzger, D.O. Terry, D.E. Grandstaff, Geology 32 (2004) 497.20] C.N. Trueman, A.K. Behrensmeyer, R. Potts, N. Tuross, Geochim. Cos-

mochim. Acta 70 (2004) 4343.21] C.N. Trueman, J.H. Field, J. Dortch, B. Charles, S. Wroe, Proc. Natl. Acad.

Sci. U.S.A. 102 (2005) 8381.22] C.N. Trueman, N. Tuross, in: M.J. Khon, J. Rakovan, J.M. Hughes

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