digesdahl® digestion apparatus models 23130-20, -21-instrument manual (1)

23130-18

Digesdahl ® DigestionApparatus

Models 23130-20, -21

Instrument Manual

© Hach Company, 1989-91, 1995-97, 1999. All rights reserved. Printed in the U.S.A. hm/ct 2/97 8 edaa/dk Rev. 2, 9/99

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CERTIFICATION

Hach Company certifies this instrument was tested thoroughly, inspecand found to meet its published specifications when it was shipped frothe factory.

The Digesdahl has been tested and is certified as indicated to thefollowing instrumentation standards.

Product SafetyPer 73/23/EEC LVD: certified compliant by Hach Company to EN 61011 (IEC1010-1), supporting test records by ETL. Listed by ETL to UL3101-1 (Listing # H0492805390). Certified by CSA to CSA C22.2 No.1010.1 (Certification # H0492805390).

ImmunityEN 50082-1 (European Generic Immunity Standard) per 89/336/EECEMC: Supporting test records by Hach Company, certified complianceHach Company.

Standards include:EN 61000-4-2 “1995” (IEC 801-2) Electro-Static Discharge

EN 61000-4-4 “1995” (IEC 801-4) Electrical Fast Transients/Burst

EN 61000-4-5 “1995” (IEC 1000-4-5) Surge

EN 61000-4-11 “1994” (IEC 1000-4-11) Voltage Dips,Interruptions and Variations

ENV 50140 “1993” (IEC 801-3) Radiated RF Electro-Magnetic Fields

ENV 50141 “1993” Conducted Disturbances Induced by RF Fields

ENV 50204 “1995” Radiated Electro-Magnetic Field from DigitalTelephones.

EmissionsEN 50081-1 (Emissions) per 89/336/EEC EMC: Supporting test recorby TÜV Product Services and Hach Company, certified compliance byHach Company.

Standards include:EN 55014 (CISPR 14) Emissions, Class B Limits

EN 60555-2 Harmonic Disturbances Caused by Electrical Equipment

EN 60555-3 Voltage Fluctuation (Flicker) Disturbances Caused byElectrical Equipment

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CERTIFICATION, continued

Canadian Interference-Causing Equipment Regulation, IECS-003,Class A:Supporting test records by TÜV Product Services, certified compliancby Hach Company.

This Class A digital apparatus meets all requirements of the CanadianInterference- Causing Equipment Regulations.

Cet appareil numérique de la classe A respecte toutes les exigences dRèglement sur le matériel brouilleur du Canada.

FCC Part 15, Class "A" Limits: Supporting test records by TÜV ProducServices, certified compliance by Hach Company.

(1) this device complies with Part 15 of the FCC Rules. Operation issubject to the following two conditions:

(2) this device may not cause harmful interference, and (2) this devicemust accept any interference received, including interference that maycause undesired operation.

Changes or modifications to this unit not expressly approved by the paresponsible for compliance could void the user's authority to operate tequipment.

This equipment has been tested and found to comply with the limits foClass A digital device, pursuant to Part 15 of the FCC Rules. These limare designed to provide reasonable protection against harmfulinterference when the equipment is operated in a commercialenvironment. This equipment generates, uses, and can radiate radiofrequency energy and, if not installed and used in accordance with theinstruction manual, may cause harmful interference to radiocommunications. Operation of this equipment in a residential area islikely to cause harmful interference, in which case the user will berequired to correct the interference at his own expense.

The following techniques of reducing the interference problems areapplied easily:

1. Disconnect power from the Digesdahl to verify that it is the source othe interference.

2. If the Digesdahl is plugged into the same outlet as the device withwhich it is interfering, try another outlet.

3. Move the Digesdahl away from the device receiving the interferenc

4. Reposition the receiving antenna for the device receivingthe interference.

5. Try combinations of the above.

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TABLE OF CONTENTS

CERTIFICATION ................................................................................................................. iii

SPECIFICATIONS............................................................................................................... vii

SAFETY PRECAUTIONS ..................................................................................................

OPERATION

SECTION 1 GENERAL DESCRIPTION ...........................................................................1.1 Introduction ......................................................................................................................... 31.2 Scope of Instructions..................................................................................................... 3

SECTION 2 PREPARATION FOR USE .............................................................................2.1 Unpacking ........................................................................................................................... 52.2 Assembly............................................................................................................................. 6

2.2.1 Heater Assembly.................................................................................................2.2.2 Fractionating Head System.................................................................................

2.3 Selecting a Temperature Setting..................................................................................

SECTION 3 SAFETY & ENVIRONMENTAL CONSIDERATIONS ............................. 113.1 Digesdahl Digestion Apparatus....................................................................................3.2 Using Hydrogen Peroxide ............................................................................................3.3 Using Sulfuric Acid.......................................................................................................143.4 Clean Up of Spills and Leaks.......................................................................................3.5 Waste Management .....................................................................................................

CONSIDERATIONS DE SECURITE ET D’ENVIRONNEMENT....................................... 13.6 Minéralisateur Digesdahl .............................................................................................3.7 Utilisation de l’eau oxygénée.......................................................................................3.8 Utilisation de l’acide sulfurique ....................................................................................3.9 Nettoyage des déversements et fuites.........................................................................

SECTION 4 OPERATION .................................................................................................4.1 Apparatus Preparation.................................................................................................14.2 Digestion ........................................................................................................................... 21

4.2.1 Appropriate Sample Size ....................................................................................4.2.2 Proper Digestion Solution Temperature ..............................................................4.2.3 Sufficient Sulfuric Acid ........................................................................................4.2.4 Carbonization Period ..........................................................................................4.2.5 Adequate Peroxide Concentration for Sufficient Time.........................................4.2.6 Containment of Sample ......................................................................................

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TABLE OF CONTENTS, continued

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4.2.7 Sampling and Storage.........................................................................................4.2.8 Accuracy Check ..................................................................................................

DIGESTION PROCEDURES

GENERAL DIGESDAHL DIGESTION .............................................................................

SAMPLE TYPE AND SIZE.................................................................................................

DIGESTION PROCEDURE FOR AQUEOUS LIQUIDS ................................................. 3

DIGESTION PROCEDURE FOR OILS .............................................................................

DIGESTION PROCEDURE FOR SOLIDS .......................................................................

MAINTENANCE

SECTION 5 MAINTENANCE ...........................................................................................5.1 Fuse Replacement .......................................................................................................815.2 Kit Replacement Parts .................................................................................................

GENERAL INFORMATION

REPLACEMENT PARTS....................................................................................................

HOW TO ORDER ..............................................................................................................

REPAIR SERVICE .............................................................................................................8

WARRANTY.......................................................................................................................... 89

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SPECIFICATIONS

Temperature Range:Variable from 100 to 480° C (212 to 896° F)

Temperature Control:Within ±15 ° C of set point*

Power Requirements:115 and 230 Vac models, 50/60 Hz, 250 W** (use only single phasefor 230 V)

Aspirator Capacity:11.5 L/min (3.0 gal/min) at water flow rate of 6.5 L/min (1.7 gal/min).Minimum pressure 51.7 kPa (7.5 psi). Drain required.

Dimensions:14 cm x 16.5 cm x 33.6 cm (5.5” x 6.5” x 13.25”).Total height: approximately 61 cm (24”) when assembled for use.

Weight:Net: 3.85 kg (8.5 lbs)Shipping: 4.8 kg (10.6 lbs)

Operating Conditions:15-35° C (59-95° F); 0-85% relative humidity

* The Digesdahl apparatus may be influenced by electric field radiation of 3 volts per meter or greater atfrequencies of 100 ±15 MHz and 180 ±15 MHz. The temperature specification of ±15° C was not exceeded bymore than 10° C at these radio frequencies.** Use only single phase power for 230 V models. The over-temperature protection device may not interrupt pwhen using poly-phase power.

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SAFETY PRECAUTIONS

NoticeBefore attempting to unpack, set up or operate this instrument, pleasethis entire manual.

Pay particular attention to Section 3! Failure to do so could result inserious injury to the operator or damage to the equipment.

The digestion procedures in this manual involve the use of strong acidand oxidizer at high temperatures. To avoid personal injury, observeall warning messages.

Use of Danger Messages, Cautions and NotesDanger messages, warnings, cautions and notes used in this manuathe following significance:

DANGERIndicates either a potentially or imminently hazardous situation which,

if not avoided, could result in death or serious injury.

CAUTIONIndicates either a potentially or imminently hazardous situation which,

if not avoided, could result in minor or moderate injury.

NOTEInformation that requires special emphasis.

Precautionary LabelsPlease pay particular attention to labels and tags attached to the instrum

Personal injury or damage to the instrument could occur if not observe

This symbol, if noted on the instrument, references the InstructionManual for operational and/or safety information.

3.1 Digesdahl Digestion Apparatus

3.2 Using Hydrogen Peroxide

3.3 Using Sulfuric Acid

3.4 Clean Up of Spills and Leaks

4.2 Digestion

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OPERATION

DANGER

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Handling chemical samples, standards, and reagents can be dangerous. Review thenecessary Material Safety Data Sheets and become familiar with all safety proceduresbefore handling any chemicals.

DANGERLa manipulation des échantillons chimiques, étalons et réactifs peut être dangereuse.Lire les fiches de données de sécurité des produits nécessaires et se familiariser avectoutes les procédures de sécurité avant de manipuler tout produit chimique.

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SECTION 1 GENERAL DESCRIPTION

1.1 IntroductionThe Hach Digesdahl Digestion Apparatus shown inFigure 1 is designedto digest a wide variety of sample types for subsequent determinationtotal Kjeldahl nitrogen, several minerals, and nutrients. Sample typesinclude food products, feeds, grains, wastewater sludges, plating bathplant tissues, fertilizers, beverages, and oils.

Digestion takes a fraction of the time required for traditional methods.The digest is used with colorimetric, turbidimetric or titrimetricprocedures for final measurements. Digesdahl test results comparefavorably in accuracy and precision with those obtained by traditionalanalytical methods.

DANGERThis product does not have thermal run-away protection when usingpolyphase AC main power systems. Use this instrument only with singphase 230 VAC systems.

DANGERCe produit n’a pas de protection contre la surchauffe lorqu’il est utilisésur une alimentation électrique en triphasé. Utiliser cet appareilseulement sur alimentation 230 V monophasé.

1.2 Scope of InstructionsThis manual is a guide and reference for safety recommendations,assembly, general operation, replacement parts, service and warrantyinformation. Digestion procedures for the Digesdahl Digestion Apparavary according to the type and form of the sample. Digestions for liquidoils and solids are found in this manual.

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Figure 1 Digesdahl Digestion Apparatus

CAPILLARYFUNNEL

VENT TRAPCAP

HEATERASSEMBLY

CAPILLARYFUNNELADAPTOR

POWERSWITCH

TEMPERATURECONTROL

DIGESTIONFLASK

FLASKWEIGHT

SAFETYSHIELD

COLLUMNBAFFLE

VENT TRAPBODY

FRACTIONATINGCOLUMN

COLUMNRECEPTACLE

VERTICALSUPPORT

HEATSHIELD

TEMPERATUREINDICATOR

MODESWITCH

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SECTION 2 PREPARATION FOR USE

2.1 UnpackingRemove the Digesdahl Digestion Apparatus and accessories fromshipping container and inspect each item for any damage that mayoccurred during shipping.

Verify that the following items are present:

• Heater Assembly, with power cord, fuse

• Vertical Support, shielded

• Column Receptacle

• Digestion Flasks (2)

• Flask Weight

• Heat Shield

• Aspirator

• Cooling Pad

• Finger Cots (2)

• Goggles, safety

• Instruction Manual

• Fractionating Head System parts:

• Fractionating Column, w/protector• Capillary Funnel• Capillary Funnel Adapter• Vent Trap Body• Vent Trap Cap• Column Baffle Tubing, C-Flex, 6.25 feet

If any items are missing or damaged, please contact the Customer SeDepartment, Hach Company, Loveland, Colorado (the toll-free numbe800-227-4224). For customers outside the U.S.A., contact the Hach oor authorized distributor serving you. Please do not return the instrumwithout prior authorization from Hach.

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2.2 Assembly2.2.1 Heater Assembly

Assemble the heater assembly as shown inFigure 2.

Figure 2Heater Assembly

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2.2.2 Fractionating Head SystemThe fractionating head system is shown inFigure 3 and includes thefractionating column, column baffle, the capillary funnel, and the exhasystem components. Assemble as follows:

1. Place the fractionating column in the column receptacle (shown inFigure 2) and place the column baffle in the top of the column with thtapered end up.

2. Insert the capillary funnel adapter into the largest opening of the vetrap body.

Note: The Hach Fume Scrubber Apparatus can be used in place of the aspirator.Fumes are drawn into a chemical absorber module and absorbed by an activatedcarbon filter. This filter is replaced when the absorbing capacity is exhausted. TheFume Scrubber is designed for running up to six digestions simultaneously. .

3. Place the vent trap cap on the capillary funnel adapter .

4. Place the assembled capillary funnel adapter and vent trap parts onfractionating column.

5. Insert the capillary funnel stem into the hole in the vent trap cap.

6. Install the aspirator in a suitable water tap over a sink. Install the hobarb fitting in the aspirator side port and install the extension tube.

DANGERThe Hach Fume Scrubber Apparatus can only be used with theDigesdahl Digestion Apparatus for sulfuric acid digestions. Hazardousconditions could develop if fumes from an alternate acid are vented witthe Fume Scrubber. It is important to clean the Fume Scrubber aftereach use to prevent corrosion (see Operation section of FumeScrubber manual).

DANGERL'épurateur de fumées Hach peut seulement être utilisé avec leminéralisateur Digesdahl pour des minéralisarions à l'acide sulfurique.Des conditions de risque peuvent être créées par l'aspiration de vapeud'un autre acide dans l'épurateur de fumées. Il est important denettoyer l'épurateur de fumées après chaque utilisation pour éviterla corrosion.

7. A 6.25-foot length of C-flex tubing is supplied with the aspirator. Cua segment approximately 16 inches long and connect the top stemthe column receptacle to the vent trap body. Cut another segment frthe remaining tubing to connect the aspirator to the lower stem of thcolumn receptacle. This segment should be kept taut with no drapethat can collect condensate. The fractionating head system is nowassembled for use.

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Figure 3Fractionating Column andExhaust Assembly

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2.3 Selecting a Temperature Setting

Note: During adigestion, thetemperaturereading will varyslightly above andbelow theselectedtemperature. Thiswill not affect thedigestion or theaccuracy of thefinal analysis.When idling (nodigestion flask inplace), thetemperature mayfluctuate ± 15 ° Cfrom the set point.

The particular temperature applicable for the sample to be digestegiven in the appropriate analysis procedure manual. The steps beexplain how to set the heater temperature.

1. Connect the power cord to the line voltage receptacle and set thePOWER switch to ON. The TEMPERATURE indicator will light.

2. Set the Mode switch to SET. The TEMPERATURE indicator willdisplay the current temperature set point in degrees Celsius.

3. If a different temperature is desired, adjust the Temperature ADJcontrol for the desired temperature in the digital display.

4. Set the Mode switch to READ and allow time (approximately10 minutes) for the heater to reach the selected temperature. WithMode switch in the READ position, the temperature display shows tcurrent operating temperature.

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SECTION 3 SAFETY & ENVIRONMENTALCONSIDERATIONS

Each person performing laboratory tests is responsible for safety. Theanalyst should develop and practice good safety habits to minimizechances for accidents by practicing good laboratory techniques.

3.1 Digesdahl Digestion ApparatusFor safe Digesdahl operation, observe the following precautions:

• Sample size -- Never digest a sample which contains over 0.5 g ofmaterial which is not water.

• Oils and organic liquids should be considered as solids whendetermining sample size.

• Acid type -- Only use acid specified in Hach step-by-step procedure

• Acid volume -- Never use less than 3 mL.

• Always follow the order of steps indicated.

• If the sample goes to dryness, remove it from the heat immediately acool at room temperature.Never add hydrogen peroxide to a drysample flask; an explosion could occur. If you are not sure enoughsulfuric acid is present in the digestion flask, STOP. Do not addhydrogen peroxide. Begin the digestion again with less sample ormore sulfuric acid.

• Be sure to keep the heat shield and the Digesdahl’s safety shield inplace during use.

• Always perform digestion behind a safety shield (Cat. No. 20974-00) oa closed fume hood.

• For respiratory protection, use a fume hood or Hach’s Fume ScrubApparatus (Cat. No. 23266).

• Always wear safety glasses or goggles- be sure they have side shie

• Wear protective gloves for during digestion procedures. Use tongsfinger cots to transfer hot apparatus.

• Do not add alcohol, acetone or other organic solvents to the digestiflask before or after digestion.

• During digestion, use the heat setting and digestion time specifiedthe instructions. Do not leave the Digesdahl unattended during use

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• When digesting a new substance for the first time, begin with a smasize and work up to the optimum quantity for digestion.Do not permitthe flask to boil to dryness.

• Use laboratory coats or aprons to protect skin and clothingfrom splashes.

• Wear appropriate shoes to protect feet from spills. Open-toed shoeshould not be worn.

• Do not use damaged glassware or apparatus. Discard all damagedequipment and replace it.

• Allow the Digesdahl to cool naturally (in ambient air). Cold water macause hot glassware to shatter.

3.2 Using Hydrogen Peroxide

DANGERHydrogen peroxide is an explosion hazard.

Use these additional specific safety precautions when using hydrogenperoxide in the Digesdahl digestion applications:

• Do not mix hydrogen peroxide with any chemical reagents except aspecified in the Hach instructions.

• Do not add hydrogen peroxide directly to the column on the digestioflask. Always add hydrogen peroxide in a slow and controlled mannuse the capillary funnel.

• Hydrogen peroxide should be added to the organic materials in theflask only when sulfuric acid is present.

• Do not use hydrogen peroxide in concentrations greater than 50%.

Hydrogen peroxide (30% or 50%) is a powerful oxidant and should nevbe stored near flammable materials. Like sulfuric acid, it can cause buand eye damage.In case of eye or skin contact, flush eyes and/or skinwith water for 15 minutes. Immediately call a physician.

Hydrogen peroxide is highly corrosive and should be cleaned up withwater if spilled on instruments or a counter top. Read and observe allwarnings on the reagent labels and Material Safety Data Sheets.

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Proper handling and storage procedures involving hydrogen peroxideshould always address two major characteristics of the product:

• It is a strong oxidizing agent. The chemical nature of hydrogenperoxide makes it an strong irritant to skin, mucous membranes anparticularly to the eyes. It will cause chemical burns at industrialconcentrations and may cause spontaneous combustion uponimmediate or prolonged contact with combustibles

• It can decompose, releasing heat and oxygen. Normally this rate isvery slow for industrial-grade product, but it will accelerate whencontaminated by materials such as dust, metallic ions, or alkali.

Please observe the following precautions for handling and storing ofhydrogen peroxide:

• Do store in a cool place away from direct sunlight (preferably ina refrigerator).

• Do store in the original containers with closures as supplied and keepclosed when not in use. (Be sure the containers are vented. Hach hydrperoxide bottles are shipped with a special vented cap liner.)

• Do wear gloves and safety glasses when handling the material.

• Do use silicon carbide boiling chips when digesting liquid samples.

• Do wash contaminated skin and body quickly with plenty of water.Remove contaminated clothing and wash well before using again.

• Do wash eyes with plenty of water if contaminated and get medicalattention quickly.

• Do get medical advice without delay if the material is ingested.

• Do flush all spills with large amounts of water.

• Do not store near heat sources or in contact with combustible ororganic materials.

• Do not inhale vapors or ingest the material.

• Do not allow contact with eyes or skin.

• Do not allow contact with decomposition catalysts (metals, dust,alkali, etc.).

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• Do not use unapproved materials (brass, copper, carbon steel, rubetc.) for transfer or storage systems.

Caps on the reagent bottles are made with a special porous liner thatallows venting of gas. The venting cap always must be used on the boof hydrogen peroxide. As a precaution, the reagent bottles are shippedplastic bag. If there is evidence of leakage during shipment, wear glovwhen removing the bottle from the bag and rinse the bottle with waterwhen removed from the bag. Rinse the bag before disposal.

3.3 Using Sulfuric AcidRead and observe all warnings on the reagent labels and Material SafData Sheets that accompany the sulfuric acid.

Concentrated sulfuric acid used in the digestion process should behandled correctly and with caution. Sulfuric acid is a strong acid andstrong oxidizer; it can cause burns if splashed on the skin and permandamage if eye contact occurs. This caustic action is much more severthe acid is hot.In case of eye or skin contact, flush eyes and/or skinwith water for 15 minutes. Immediately call a physician.

Sulfuric acid mist or vapor has been classified by the InternationalAgency for Research on Cancer (IARC) as a possible human carcinog

Sulfuric acid is a strong oxidizer. It may ignite or explode on contact wimany different chemicals. Follow proper storage regulations.

3.4 Clean Up of Spills and LeaksUse extreme caution when cleaning spills and leaks throughout the endigestion procedure. Your facility may require that only trainedindividuals wearing appropriate protective equipment (gloves, gogglesface shields and chemical resistant clothing) respond to a spill or leakensure the Digesdahl is properly cleaned.

A spill, overflow, or eruption from the Digesdahl apparatus may leaveresidue on the equipment or other surfaces. Cleaning the residue musdone cautiously. Do not use alternative cleaning methods or cleaningagents not authorized or endorsed by Hach Company; they may damathe equipment.

While cleaning a spill or leak, please follow the safety measures below

1. DO NOT attempt to clean the apparatus if it is hot; this could causeglass to shatter. Let the apparatus cool before cleaning it.

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2. Unplug the Digesdahl before cleaning.

3. Wear gloves and goggles when handling the glassware. Carefully rithe glassware several times with water to decontaminate it.

4. Wipe the exterior surfaces of the Digesdahl apparatus (heating manelectrical controls, etc.) and other laboratory surfaces several timeswith a damp or wet cloth or paper towel.

5. Do not rinse or spray the apparatus directly; this could damagethe equipment.

6. Discard any paper towels or cloths in an appropriate manner; they mbe contaminated from the sample or chemical residues.

3.5 Waste ManagementHazardous waste disposal regulations were promulgated in accordanwith the Resource Conservation and Recovery Act (RCRA) and are givin Title 40 Code of Federal Regulations (CFR), parts 260 to 280. Wastmust be managed and disposed of in accordance with federal, state alocal regulations. Refer to Section VIII of the Hach Material Safety DatSheet that come with reagents for basic disposal information on HachProducts. The USEPA maintains a hotline number for questions regardRCRA. It is 1-800-424-9346

This manual does not contain all the regulatory requirements. Additionstate and local laws may apply to waste that you generate. It is eachgenerator’s responsibility to know which regulations apply to them andadhere to these regulations. Check with your environmental complianstaff for specific instructions.

Section 3 summarizes basic requirements for safely handling thechemicals used in the Digesdahl digestion. It is a guide only and is nocomprehensive for all parties. The information is not intended to providany express or implied warranties to readers. This information is notintended to form any type of obligation upon Hach Company orits agents.

For further information, please contact the Hach Environmental Safetyand Health Department at (515) 232-2533.

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CONSIDERATIONS DE SECURITE ET D’ENVIRONNEMENT

Chaque personne effectuant des analyses de laboratoire est responsala sécurité. L’analyste doit développer et appliquer de bonnes habitudde sécurité pour minimiser les risques d’accidents en pratiquant de bontechniques de laboratoire.

3.6 Minéralisateur DigesdahlPour une utilisation du Digesdahl en toute sécurité, observer lesprécautions suivantes :

• Poids d’échantillon : Ne jamais minéraliser un échantillon qui contieplus de 0,5 g de produit qui ne soit pas de l’eau.

• Les huiles et liquides organiques doivent être considérés comme dsolides pour la détermination du poids d’échantillon.

• Type d’acide : Utiliser seulement l’acide spécifié dans les techniquedétaillées de Hach.

• Volume d’acide : Ne jamais utiliser moins de 3 ml.

• Toujours suivre l’ordre des opérations indiqué.

• Si la fiole va à sec, la retirer immédiatement du système de chauffaet la laisser refroidir à la température ambiante.Ne jamais ajouterd’eau oxygénée à une fiole d’échantillon à sec, une explosionpourrait se produire. Si vous n’êtes pas sûr que la fiole contienneassez d’acide sulfurique, ARRETEZ. Ne pas ajouter d’eau oxygénéRecommencer l’opération avec une quantité d’échantillon plus petiou plus d’acide.

• Prendre soin de maintenir en place la cheminée et le manchon desécurité du Digesdahl pendant l’utilisation.

• Toujours effectuer les minéralisations derrière un écran de protecti(# 20974-00) ou sous une hotte fermée.

• Pour une protection respiratoire, utiliser une hotte ou l’épurateur defumées Hach (réf. n° 23266).

• Toujours porter des lunettes de sécurité avec protections latérales.

• Porter des gants pour la protection pendant les opérations de digesUtiliser des pinces ou des doigtiers de protection pour déplacer lesobjets chauds.

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• NE PASajouter d’alcool, d’acétone ou autre solvant organique dansfiole de digestion avant ou après minéralisation.

• Pendant la digestion, utiliser le réglage de température et le tempsdigestion spécifié dans les instructions. Ne pas laisser le Digesdahsans surveillance pendant l’utilisation.

• Lors de la minéralisation d’une nouvelle substance pour la premièrfois, commencer avec une quantité plus petite avant d’utiliser laquantité optimale pour l’analyse.Ne paslaisser le contenu de la fioles’évaporer à sec.

• Porter une blouse ou un tablier de laboratoire pour protéger la peales vêtements des projections.

• Porter des chaussures appropriées pour protéger les pieds desdéversements de produits. Ne pas porter de chaussures à bout ou

• Ne pas utiliser de verrerie ou appareils endommagés. Eliminer etremplacer tous les équipements endommagés.

• Laisser le Digesdahl refroidir naturellement (dans l’air ambiant). L’eafroide peut briser le verre chaud.

3.7 Utilisation de l’eau oxygénée

DANGERL’eau oxygénée(peroxyded’hydrogène)sous formeconcentréeprésente unrisqued’explosion.

Utilisez ces précautions de sécurité supplémentaires spécifiques pourl’utilisation de l’eau oxygénée dans les minéralisations par le Digesda

• NE PAS mélanger l’eau oxygénée avec d’autres réactifs saufindication précisée dans les procédures d’analyse Hach.

• NE PAS ajouter d’eau oxygénée directement dans la colonne defractionnement sur la fiole de digestion. Ajouter toujours l’eauoxygénée avec un débit lent et régulier, utiliser l’entonnoir àcapillaire Hach.

• L’eau oxygénée doit être ajoutée à la matière organique carboniséedans la fiole,seulementen présence d’acide sulfurique.

• NE PAS utiliser d’eau oxygénée à des concentrations supérieuresà 50%.

17

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La

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L’eau oxygénée (30% ou 50%) est un oxydant puissant et ne doit jamaêtre stocké près de matières inflammables. Comme l’acide sulfuriqueil peut provoquer des brûlures à la peau et aux yeux.En cas de contactavec les yeux ou la peau, laver les yeux et/ou la peau à l’eau pendant15 minutes. Retirer les vêtements contaminés. Appeler un médecin.

L’eau oxygénée est extrêmement corrosive et doit être lavée à l’eau siest répandue sur des appareils ou sur la paillasse. Lire et observer touavertissements sur les étiquettes des réactifs et les fiches de donnéessécurité des produits.

Les procédures de manipulations et de stockage concernant l’eauoxygénée doivent tenir compte de deux caractéristiques importantesdu produit :

• C’est un agent fortement oxydant. La nature chimique de l’eauoxygénée en fait un produit irritant pour la peau, les muqueuseset particulièrement les yeux. Il provoque des brûlures graves auxconcentrations auxquelles il est utilisé dans l’industrie et peutprovoquer une combustion spontanée au contact immédiat ou prolodes combustibles.

• Il peut se décomposer avec dégagement de chaleur et d’oxygène.vitesse de décomposition naturelle du produit de qualité industriellecourante est très lente, mais elle s’accélère lorsqu’elle est contamipar des substances telles que poussière, ions métalliques, ou alca

Prendre les précautions suivantes pour la manipulation et le stockagel’eau oxygénée :

• Stocker dans un endroit frais à l’abri de la lumière directe du soleil(de préférence dans un réfrigérateur).

• Stocker dans les récipients d’origine avec les bouchons fournis et lmaintenir fermés lorsqu’ils ne sont pas utilisés. (S’assurer que lesrécipients sont ventilés. Les flacons d’eau oxygénée Hach sont livravec un joint de bouchon perméable spécial).

• Porter des gants et des lunettes de sécurité lors de la manipulationdu produit.

• Utiliser des grains de carbure de silicium pour régulariser l’ébullitiolors de la digestion d’échantillons liquides.

18

ent

,desconc

es

cidet/

• Laver la peau contaminée rapidement à grande eau. Retirer rapidemles vêtements contaminés et les laver soigneusement avant de lesréutiliser. Les laver régulièrement.

• Laver les yeux à grande eau s’ils sont contaminés et consulter unmédecin immédiatement.

• Consulter immédiatement un médecin si le produit est ingéré.

• Laver toute trace répandue à grande eau.

• NE PAS stocker près des sources de chaleur ou au contact decombustibles ou de produits organiques.

• NE PAS laisser le produit stocké ou enfermé dans un espace clos.

• NE PAS inhaler les vapeurs ou ingérer le produit.

• NE PAS mettre le produit au contact des yeux et de la peau.

• NE PAS laisser au contact avec des catalyseurs de décomposition(métaux, poussières, produits alcalins, etc.).

• NE PAS utiliser de matériaux de construction inadaptés (laiton,cuivre, acier, caoutchouc, etc.) pour les systèmes de stockageet tuyauteries.

Les bouchons des flacons de réactifs sont prévus avec un joint poreuxspécial qui permet l’échappement de gaz. Le bouchon d’origine doittoujours être utilisé sur le flacon d’eau oxygénée. A titre de précautionles flacons de réactifs sont expédiés dans un sac plastique. S’il existetraces de fuites pendant le transport, porter des gants pour retirer le fladu sac et rincer le flacon à l’eau après l’avoir sorti du sac. Rincer le saavant élimination.

3.8 Utilisation de l’acide sulfuriqueLire et observer tous les avertissements sur les étiquettes desproduits et la fiche de données de sécurité du produit qui accompagnel’acide sulfurique.

L’acide sulfurique concentré utilisé dans l’opération de minéralisationdoit être manipulé correctement et avec précaution. L’acide sulfuriqueest un acide fort et un oxydant puissant qui peut provoquer des brûlurgraves au contact de la peau et des lésions irréversibles s’il est mis aucontact des yeux. Cette action corrosive est beaucoup plus grave si l’aest chaud.En cas de contact avec les yeux ou la peau, laver les yeux e

19

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uits

etione

re

s

deour

été

ou la peau à l’eau pendant 15 minutes. Retirer les vêtementscontaminés. Appeler un médecin.

L’acide sulfurique sous forme de brouillard ou de vapeur a été classécomme cancérigène possible pour l’homme par l’Agence Internationade Recherche sur le Cancer (IARC).

L’acide sulfurique est un oxydant puissant. Il peut provoquer un feu ouexploser au contact de nombreux produits chimiques différents. Suivrerègles de stockage appropriées.

3.9 Nettoyage des déversements et fuitesPrendre les plus grandes précautions pour nettoyer des fuites ou prodrépandus pendant toute la technique de digestion. Votre société peutexiger que seules des personnes habilitées portant les équipements dprotection appropriés (gants, lunettes de sécurité, masques de protecet vêtements résistants aux agents chimiques) interviennent en cas ddéversement ou de fuite.

Un déversement, débordement ou une projection par le minéralisateuDigesdahl peut laisser un résidu sur le matériel ou d’autres surfaces. Lnettoyage du résidu doit être fait avec précaution. Veuillez observer lemesures de sécurité ci-dessous :

1. NE PAS tenter de nettoyer l’appareil pendant qu’il est chaud, cecipeut causer la rupture du verre. Laisser refroidir l’appareil avant dele nettoyer.

2. Débrancher le Digesdahl avant de le nettoyer.

3. Porter des gants et des lunettes de protection pour la manipulationla verrerie. Rincer soigneusement la verrerie plusieurs fois à l’eau pla décontaminer.

4. Essuyer les surfaces extérieures de l’appareil Digesdahl(plaque chauffante, commandes électriques, etc.) et autressurfaces du laboratoire plusieurs fois avec un tissu humide ouun papier d’essuyage.

5. Ne pas rincer ou arroser l’appareil directement, ceci pourraitle détériorer.

6. Eliminer les papiers et tissus de façon appropriée, ils peuvent avoircontaminés par l’échantillon ou les résidus chimiques.

20

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SECTION 4 OPERATION

4.1 Apparatus PreparationSeeSECTION 3for more safety information. Prepare to perform thedigestion either behind a laboratory safety shield or inside a fume hooda fume hood is used, check the fume exhaust system to verify it isworking property.

Safety glasses and protective clothing are mandatory.

Turn on the water to the aspirator to maximum flow. Remove thecapillary funnel and place a finger over the opening in the vent trap capdistinct suction should be felt.

4.2 DigestionProcedures for using the Digesdahl Digestion Apparatus vary with samtype. Most procedures use a two-phase digestion process involvingconcentrated sulfuric acid and 50% hydrogen peroxide. Sulfuric aciddehydrates and chars the sample. Hydrogen peroxide is added via thecapillary flow funnel to complete sample decomposition. The capillaryfunnel feeds hydrogen peroxide into the digestion flask at a rate of 3 mper minute. This allows the analyst to control the amount of time sampis exposed to the hydrogen peroxide (digestion time) by varying thevolume of hydrogen peroxide used.

DANGERWear protective eye glasses and clothing. A strong acid (concentrated sulfuric acid) aa strong oxidant (50% hydrogen peroxide) are used in the digestion reaction. Thesechemicals can cause burns if splashed on the skin or permanent eye damage if allowto contact the eyes. If the chemicals are hot, effects are considerably more severe.Immediately rinse any affected area thoroughly with water and contact a physician.

DANGERPorter des lunettes et vêtements de protection. Un acide fort (acide sulfurique concenet un oxydant puissant (peroxyde d'hydrogène à 50%) sont utilisés dans la réactionminéralisation. Ces produits chimiques peuvent causer des brûlures s'ils sont projetésla peau ou des blessures irréversibles aux yeux s'ils sont mis au contact des yeux. Siproduits sont chauds, les effets sont considérablement plus graves. Immédiatement rintoute partie atteinte abondamment à l'eau et consulter un médecin.

Use the Digesdahl Digestion Apparatus only behind a laboratory safeshield or in a closed fume hood.

Some samples are more difficult to digest completely. In a careful studof the minimal time required to digest a variety of materials, completenitrogen recovery was achieved for many samples immediately uponclearing of the digest (when the digest becomes colorless). However,resistant or refractory materials such as nicotinic acid require severalminutes of continued peroxide digestion after clearing to obtain 100%nitrogen recovery.

21

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A general procedure, incorporating application specific requirements,provided in this section of the manual. To ensure complete sampledigestion, consider the variables described in the following paragraph

4.2.1 Appropriate Sample SizeFor solid or organic liquid samples, less than 0.5 grams of anhydrousmaterial can usually be digested effectively. (As a routine practice, 0.2of sample is used.) Samples that contain water may be scaled up by aproportional amount. There is no restriction or minimum sample size. Fsamples of aqueous solutions or suspensions, the maximum volume imL. When the percent solids exceeds 1% of the sample volume, themaximum sample volume should be reduced using the formula:

4.2.2 Proper Digestion Solution TemperatureDigestion temperature is critical. If the hydrogen peroxide is added tocold digestion mixture followed by heating, the hydrogen peroxidedecomposes before the digest reaches the proper temperature. Additihydrogen peroxide to a digest that is too hot volatilizes most of theoxidant with little benefit. Also, excessive heat contributes to spray losof sample as a fine mist. The temperature recommended for most samis 440° C (825° F). For oils, fuels and lubricants, the temperature mayneed to be decreased.

4.2.3 Sufficient Sulfuric AcidThe amount of concentrated (specific gravity 1.84) sulfuric acid usedmust besufficient to prevent the digestion from going to dryness. Anyportion of the flask bottom that becomes dry will overheat and may cauthe flask to explode. Also, too little acid will cause the sample tooverheat, which may cause thermal decomposition of desired analyte(i.e., ammonium compounds) and result in sample loss. Use an amounsulfuric acid that will leave at least 2 mL of residual acid when digestiois complete. Refer toTable 1for recommended volumes.

sample 40% solids--------------------=

22

Table 1 Digestion Guidelines of Specific Sample Types

SampleType

Sample WeightVol. ofAcid

PreheatTime

(Step 5)

Vol. ofPeroxide

Special Instructions

Plant tissue 0.25 to 0.5 g 4 mL 4 min. 10 mL Use Nitrogen-free paper toweigh samples.

Meat &Poultry

0.5 g orpredigestion

4 mL or as inpredigest

4 min. 10 mL —

FluidFertilizers

0.1 to 0.25 g 4 mL 4 min. 10 mL Add 0.4 g Kjeldahl ReductionPowder to flask before addingsulfuric acid. Place the flask inan 80 °C oven 15 minutes beforedigestion. Use N-free paper toweigh samples.

Feed &Forage

0.25 g 4 mL 4 min. 10 mL —

Dairy 0.25 to 2.0 g 4 mL 4 min. 10 mL —

Cereal 0.25 to 0.5 g 4 mL 4 min. 10 mL Use Nitrogen-free paper toweigh samples.

Beverage about 5 g(pipet into funnel

4 mL 1 min. 10 mL Preheat acid for 1 minute thenadd sample through funnel. Heatflask for 30 seconds after sampleis in the flask.

Sludge <2.5 g wet sludge<0.5 g dried sludge

4 mL 3-5 min. 10 mL ofincrease in 5

mL increments

Heat the diluted digest for 15minutes and filter.

Water &Wastewater

not more than 0.5 gsolid (mL = 40/C;

C= % solids)

3 mL until acidis refluxing

10 mL orincrease in 5

mL increments

Water must evaporate beforeacid will reflux. Boiling chipsrequired.

BathSolutions

0.3 to 10 mL 4 mL 4 min. 10 mL Water must evaporate beforeacid will reflux. Boiling chipsrequired.

Edible Oils 0.25 to 0.5 g 4-6 mL 4 min. 5 mLimmediately

and 5 mL later

Weigh samples into flake andrecord exact weight.

IonExchange

Resins

equivalent of 0.25 gdry resin

10-15 mL 12 min. 20 mL Digest will be clear with particleson bottom if metal oxides are notsoluble in H2SO4. Add aquareagia or suitable solvent todissolve particles. If particles arefloating, start again using 15 mLH2SO4 and longer char time.

Soil 0.25 to 0.5 g 6 mL 4 min. 10-20 mL —

Fuels 0.25 to 0.5 g 6 mL 4 min. 20 mL Heat the diluted digest for 15min. and filter. Lower heatertemperature if foaming orburning occurs.

23

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20

and

Sulfuric acid (H2SO4) consumption depends on the anhydrous mass ofmaterial and the chemical composition of the substance. Use of 4 mLH2SO4 is suitable for many materials, but not all. Therefore, the analysmust pay attention to the amount of residual H2SO4 for the type of sampledigested, and adjust the amount of acid or sample accordingly. Neverless than 3 mL of concentrated sulfuric acid. Larger volumes of H2SO4

may be used, but avoid a large excess since sample pH adjustment isrequired in most subsequent determinations.

4.2.4 Carbonization PeriodA carbonization period prior to the addition of hydrogen peroxideprovides a reducing environment which helps convert organic nitrogenammonia. In the presence of oxidizable carbon compounds, sulfuric areacts to produce sulfur dioxide, which is the active reducing agent.

The reaction is:

H2SO4 → H2O + SO2 + ½ O2

A preheat period of 2 to 5 minutes is recommended for routine digestio

4.2.5 Adequate Peroxide Concentration for Sufficient TimeResearchers believe that hydrogen peroxide (H2O2) reacts immediatelywith H2SO4 at digestion temperature to give H2SO5 (peroxymonosulfuricacid) by the reaction:

H2SO4 + H2O2 → H2SO5 + H2O

This is an extremely powerfuloxidizing agent toward carbonaceousmaterial. The objective is to maintain an adequate concentration of H2SO5

in the hot digestion mixture for a long enough time to complete oxidatiof the carbonaceous material. The H2O2 is metered into the flask at3 mL/min. using the capillary funnel.

The amount of peroxide that must be added for complete digestion candetermined by digesting a sample multiple times with incrementalincreases in the amount of peroxide added (i.e., 5 mL, 10 mL, 15 mL,mL). Results of the analysis for the parameter of interest may then begraphed to determine the minimum amount of peroxide needed foroptimum sample digestion.

The preferred and recommended peroxide reagent is 50% hydrogenperoxide. Research studies have shown that the best recovery andreproducibility are achieved using the 50% peroxide reagent. The 50%hydrogen peroxide reagent produces dependable results in researchactual applications. The optimal rate of peroxide addition has beendetermined as 3 mL/minute using the 50% reagent. This may not holdtrue if other strengths of hydrogen peroxide are used.

24

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er

If 50% hydrogen peroxide is not available, 30% peroxide may be useda last resort with caution. Because of the lesser strength, at least1.67 times more volume must be used (i.e., 16.7 mL of 30% vs. 10 mL50% peroxide). Always run a digestion standard, either glycinep-toluenesulfonate or nicotinic acid p-toluenesulfonate, when using30 percent peroxide to check completion of the digestion. Allrecommended safety precautions apply to both strengths of the hydroperoxide. SeeSection 3, Safety Considerations.

4.2.6 Containment of SampleLoss of sample from the digestion flask can occur in two ways:

(1) foaming or boiling over, and

(2) mist or spray in the ventilation air stream.

Foaming is a serious problem with certain sample types, so specialtechniques have been developed. Some liquid samples, especially thcontaining sugars, cannot be digested by the standard procedure, whconsists of placing a given volume in the flask, adding sulfuric acid anheating. Under those conditions, foaming cannot be controlled. Insteathe sulfuric acid is heated in the flask and the liquid sample is addedthrough the capillary funnel. Carbonization proceeds in a controlledmanner. When all the sample has been added, the peroxide treatmenbegins and the digestion continues normally. Other ways to controlfoaming include early addition of hydrogen peroxide and reducing thetemperature during carbonization.

Sample loss as spray or mist occurs when small droplets of liquid areswept out of the flask along with gases, and escape in the ventilation astream. The current fractionating column design reduces spray loss toinsignificant level.

4.2.7 Sampling and StorageSamples must be homogeneous to ensure that a representative portioanalyzed. Liquid samples should be homogenized via stirring or blendinSolid samples should be finely ground or chopped and well mixed. Aftdigestion, samples should be diluted to the mark, mixed, and tightlysealed. The diluted digestate will be stable for 2 to 3 days, as long asevaporation does not occur.

4.2.8 Accuracy CheckComplete digestion is necessary for accurate results. The Digesdahlsystem may be checked with Primary Standards for Kjeldahl Nitrogenusing one of the following methods.

25

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,

.ts

,

26

Solid Samples1. Weigh 0.25 grams of a Primary Standard for Kjeldahl Nitrogen.

Digest the standard following the general digestion procedure.

2. Any of the three standards may be used. Ammonium p-toluenesulfona(185.5 mg/L TKN) is the least difficult to digest. Glycinep-toluenesulfonate (141.63 mg/L TKN) is moderately difficult to digestand Nicotinic Acid p-toluenesulfonate (118.58 mg/L TKN) is the mostdifficult to digest.

Liquid Samples1. Weigh 10.000 grams of a Primary Standard for Kjeldahl Nitrogen.

2. Transfer to a 1-liter volumetric flask and dilute to the mark.

3. Using a volumetric pipet, add 15 mL of the prepared solution to thedigestion flask and digest the standard following the generaldigestion procedure.

4. Any of the three standards may be used. Ammoniump-toluenesulfonate (111.03 mg/L TKN) is the least difficult to digestGlycine p-toluenesulfonate (84.98 mg/L TKN) is moderately difficulto digest, and Nicotinic Acid p-toluenesulfonate (71.15 mg/L TKN) ithe most difficult to digest.

A primary standard set, containing one bottle of each of the standardsmay be purchased from Hach Company.Table 2lists some of theproperties of the three primary standards.

Table 2 Some Properties of Kjeldahl Nitrogen Standards (#22778-00)

Ammonia PTSA Glycine PTSA Nicotinic Acid PTSA

Formula C7H11O3SN C9H13O5SN C13H13O5SN

Structure

Molecular Weight 189.235 247.277 295.316

Melting Point, °C — 199 179

% Nitrogen 7.402 5.664 4.743

% Protein 46.261 35.403 29.643

Digestability Index 0 3 10

MoistureAbsorptionat 25 % RHat 50% RHat 90% RH

0.04%0.07%0.14%

0.03%0.047%0.15%

0.00%0.01%0.08%

DIGESTION PROCEDURES

27

DangerReview Section 3 for important safety information before

performing this digestion procedure.

DangerLire au chapitre 3 les informations importantes pour lasécurité avant d’effectuer cette technique de digestion.

28

GENERAL DIGESDAHL DIGESTION

1. Transfer apreweighed or apremeasured amount ofsample into a 100-mLDigesdahl digestionflask; seeTable 1onpage22. The amounttransferred should notcontain more than 0.5 gof solids or organicliquids. The maximumvolume for watersamples is 40 mL. Insamples with more than1% solids present, usethe formula below:

Water Sample Volume= 40 ÷ % solids

Note: Use only Hachdigestion flasks. Volumetricflasks with concave bottomsshould not be used.

Note: If solids are 10% oftotal volume of sample, themaximum volume of liquidsample would be 4 mL.

Note: Several 40-mLsample aliquots of thesample may be digested insuccession to concentratea sample.

Note: If liquid is tooviscous to measure,preweigh the sample intothe digestion flask.

2. Add concentratedsulfuric acid (accordingto Table 1on page22) tothe volumetric flask andat least two siliconcarbide boiling chips forliquid samples.

Note: Pretreat boilingchips by soaking in 1:1Nitric Acid and rinsingthoroughly with deionizedwater. Treatment is veryimportant in low-levelwork. Hach recommendssilicon carbide boilingchips.

3. Turn on the water tothe aspirator and makesure there is suction tothe fractionatingcolumn. Turn thetemperature dial to aheat setting of 440° C(825° F). For meatdigestion, set to 468° C(875° F).

Note: Wait for the propertemperature to be reachedbefore the sample is placedon the heater.

4. Place the flaskweight followed by thefractionating columnwith funnel on the flask.Place the flask on theheater and heat until thesulfuric acid boils(refluxing sulfuric acidwill be visible).

Note: White acid vaporsusually will be present, buttheir presence alone doesnot indicate that the boilingpoint of sulfuric acid hasbeen reached.

Note: Liquid samplesrequire total evaporation ofwater before vaporsare visible.

Note: If sample foams upinto the neck of the flask,lower temperature to335° C (635° F). Continueheating at lowertemperature until all wateris evaporated. Then returnto original digestiontemperature.

Note: If foaming orbumping is not stopped bylowering temperature orvolume, then liquid samplesthat will not clog thecapillary funnel may beadded to the flask via thecapillary funnel, 10 mL at atime. Decrease amountadded if foaming persists.

29

GENERAL DIGESDAHL DIGESTION, continued

5. Heat 3-5 minutes.Do not boil sampleto dryness. If sulfuricacid is not present afterheating, do not proceedwith Step 6. Discard thesample if it evaporates todryness. Start over anduse a larger volume ofsulfuric acid in Step 2 ofthis procedure. Or chosea smaller sample amountfor digestion.

Note: Some organicsamples may need morethan five minutes forcomplete digestion. SeeTable 1 on page 22.

6. Do not proceed ifsulfuric acid is notvisible in the flask. Add10 mL of 50% HydrogenPeroxide to the charredsample via the funnel onthe fractionating head.

Note: Visually confirm thepresence of sulfuric acid inthe flask before addinghydrogen peroxide.

Note: If the digest does notturn colorless, add5 mL increments ofperoxide until the digestbecomes clear.

Note: Use long-neckglassware or a pipetto transfer thehydrogen peroxide.

7. After addition ofhydrogen peroxide iscomplete, boil off excesshydrogen peroxide byheating for one moreminute. Do not heatto dryness.

Note: If the sample goesto dryness, turn off theDigesdahl and air cool toroom temperature. Addwater to flask beforehandling. Repeat thedigestion from the Step 1using a new sample.

8. Take the hot flask offthe heater and allow theflask to cool. Removethe fractionating columnfrom the digestion flask.

Note: Use finger cots toremove the digestion flask.Place it on a cooling padfor at leastone minute.Then remove the column.

3-5 minutes

30


9. Dilute the digest withapproximately 70 mL ofdeionized water. If notanalyzing for aluminum,nickel or iron, dilute tothe100-mL mark withdeionized water; skipStep 10 and proceed toStep 11. If analyzing fornickel, aluminum oriron, go to Step 10.

Note: Add deionizedwater slowly at first. Coolthe flask if necessaryfor handling.

10.Turn thetemperature dial to aheat setting of 204° C(400° F). Add 150 mL ofwater to a 400-mLbeaker. Place the beakeron the heater. Place theflask in the beaker andboil for 15 minutes.Air cool to roomtemperature and dilute tothe 100-mL mark withdeionized water. Invertseveral times to mix.

11. If the sample hasvisible turbidity, filteror wait until theturbidity settles, and theupper portion of thesample is clear.

Filter as follows:

a) Place a filter paper intothe filter holder withwrinkled surface upward.

b) Place the filter holderassembly in the filteringflask and wet the filter withdeionized water to ensureadhesion to the holder.

c) While applying avacuum to the filteringflask, transfer the sample tothe filtering apparatus.

d) Slowly release thevacuum from the filteringflask and transfer toanother container.

12.Continue theanalysis using one of thefollowing procedures.

Use metals orTKN procedure

31

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ted


Metals ProcedureNote: If analyzing aliquots smaller than 0.5 mL, pH adjustment is unnecessary.

1. Pipet the appropriate analysis volume into the appropriate mixinggraduate cylinder. See Sample and Analysis Volume Tables followithe specific digestion for liquids, solids or oils to determine theanalysis volume.

Note: Some methods require pipetting into a volumetric flask or a regulargraduate cylinder.

2. Dilute to about 20 mL with deionized water.

3. Add one drop of 2,4 Dinitrophenol Indicator Solution.

4. Add one drop of 8 N Potassium Hydroxide (KOH) Standard Solutioswirling between each addition, until the first flash of yellow appear(pH 3). If analyzing for potassium, use 5 N sodium hydroxide insteaDo not use a pH meter if analyzing for potassium or silver.

5. Add one drop of 1 N KOH. Stopper the cylinder and invert severaltimes to mix. If analyzing for potassium, use 1 N sodium hydroxideinstead.

Note: Use pH paper to insure the pH is 3. If it is higher than 4, do not readjustwith acid; start over with a fresh aliquot.

6. Continue to add 1 N KOH in this manner until the first permanentyellow color appears (pH 3.5-4.0).

Note: High iron content will cause precipitation (brown cloud) which will co-precipitate other metals. Repeat this procedure with a smaller aliquot volume.

7. Add deionized water to the volume indicated in the colorimetricprocedure for the parameter you are analyzing. Fill a second graduamixing cylinder to the same volume with deionized water.

8. Continue with the colorimetric procedure for the parameter youare analyzing.

32

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er.

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e


TKN, Colorimetric MethodsConsult the spectrophotometer or colorimeter procedure to completeTKN analysis. The following is only a guide to use if a procedure isnot available.

1. Pipet an appropriate analysis volume into a graduated mixing cylind

2. Add one drop of TKN Indicator.

3. Add one drop of 8 N KOH Standard Solution, swirling between eacaddition, until the first flash of pale blue appears (pH 3).

4. Add one drop of 1 N KOH. Stopper the cylinder and invert severaltimes to mix.

Note: View the cylinder from the top against a white background. Compare thecylinder against a second cylinder filled to the same volume with deionized water.

5. Continue to add 1 N KOH in this manner until the first permanent blucolor appears.

6. Add deionized water to the volume indicated in the colorimetricprocedure.

7. Continue with the colorimetric procedure.

33

cificas ate

beingbles

ze.

SAMPLE TYPE AND SIZE

Although the Digesdahl can digest many types of samples, a spedigestion is required for specific sample types. To classify the sampleliquid, oil or solid, use the following charts. Follow the appropriaprocedure indicated for each sample type.

Sample size varies, depending on the sample type and the parametermeasured. Once the correct sample type is decided, use the tafollowing each of the digestion procedures to determine the sample si

Chart 1For Aqueous Liquids

35

SAMPLE TYPE AND SIZE, continued

Chart 2For Oils

36

SAMPLE TYPE AND SIZE, continued

*High levels of iron may interfere with analysis of some parameters.

Chart 3For Solids*

37




38

DIGESTION PROCEDURE FOR AQUEOUS LIQUIDS

1. Transfer apremeasured amount ofsample into a 100-mLDigesdahl digestionflask; see Sample andAnalysis Volume Tablesfor Aqueous Liquidsfollowing thisprocedure. The amounttransferred should notcontain more than 0.5 gof material which is notwater. The maximumvolume for watersamples is 40 mL. Insamples with more than1% solids present, usethe formula below:

Water Sample Volume= 40 ÷ %solids

Note: Use only HachDigesdahl flasks.Volumetric flasks withconcave bottoms should notbe used.

Note: If solids are 10% oftotal volume of sample, themaximum volume of liquidsample would be 4 mL.

Note: Oils and organicsshould be considered assolids when determiningsample size.

Note: If liquid is tooviscous to measure,preweigh the sample intothe digestion flask.

2. Add 3 mL ofconcentrated sulfuricacid (spec. gravity 1.84)to the volumetric flaskand two or more siliconcarbide (carborundum)boiling chips for liquidsamples.

Note: Pretreat boilingchips by soaking in 1:1Nitric Acid and rinsingthoroughly with deionizedwater. Treatment is veryimportant in low-levelwork. Hach recommendsusing silicon carbideboiling chips.

3. Turn the temperaturedial to a heat setting of440° C (825° F). Whenthe proper temperature isreached, turn on thewater to the aspiratorand make sure there issuction to thefractionating column.

Note: Wait for the propertemperature to be reachedbefore sample is placed onthe heater.

Note: Always operate theDigesdahl apparatus witha safety shield in place orinside a closed fumehood. Safety glassesare mandatory.

4. Place the flaskweight followed by thefractionating columnwith funnel on the flask.Place the flask on theheater and heat until thesulfuric acid boils(refluxing sulfuric acidwill be visible).

Note: White acid vaporswill usually be present buttheir presence alone doesnot indicate that the boilingpoint of sulfuric acid hasbeen reached.

Note: Aqueous samplesrequire total evaporationof water before vaporsare visible.

Note: If sample foams upinto the neck of the flask,lower temperature to335° C (635° F). Continueheating at a lowertemperature until all wateris evaporated. Then returnto original digestiontemperature.

Note: If foaming orbumping is not stopped bylowering temperature orvolume, then liquid samplesthat will not clog thecapillary funnel may beadded to the flask via thecapillary funnel, 10 mL at atime. Decrease amountadded if foaming persists.

39

DIGESTION PROCEDURE FOR AQUEOUS LIQUIDS, continued

5. Boil 4 more minutes.Do not boil the sampleto dryness. If sulfuricacid is not present in theflask after the 4 minuteheating,do not proceedwith Step 6! Discardsample if it evaporates todryness. Start over anduse a larger volume ofsulfuric acid in Step 2 ofthis procedure. Orchoose a smaller sampleamount for digestion.

6. Do not proceed ifsulfuric acid is notvisible in the flask! Add10 mL of 50% HydrogenPeroxide to the charredsample via the funnel onthe fractionating column.


Note: If the digest does notturn colorless, add 5 mLincrements of hydrogenperoxide until the digestbecomes clear or does notchange color.

Note: If sample foamsduring peroxide addition,remove the Digesdahldigestion flask andfractionating column (usefinger cots). Starting withStep 1, repeat the digestionadding only 2 mL ofhydrogen peroxide. Thenfollow with 8 mL ofhydrogen peroxide.

Note: Do not heatto dryness.


Note: If the sample goesto dryness, turn off theDigesdahl and air cool toroom temperature. Addwater to flask beforehandling. Repeat thedigestion from thebeginning using a newsample.

8. Take the hot flask offthe heater and allow theflask to cool. Removethe fractionating columnfrom the digestion flask.

Note: Use finger cots toremove the digestion flask.Place it on a cooling padfor at leastone minute.Then remove the column.Do not add water to theflask until it has cooled.

4:00

40


Metals MethodNote: If analyzing aliquots smaller than 0.5 mL, pH adjustment is not necessary.

1. Pipet the appropriate analysis volume into the appropriate mixinggraduate cylinder. See Sample and Analysis Volume Tables forAqueous Liquids following this procedure to determine theanalysis volume.


9. Dilute the digest toapproximately 70 mLwith deionized water.

Note: Add deionized waterslowly at first. Cool theflask if necessaryfor handling.

10. If analyzing foraluminum, nickel oriron, continue to Step 11.If analyzing for othersubstances, dilute to the100-mL mark withdeionized water; skipStep 11 and go toStep 12.

11. Turn thetemperature dial to aheat setting of 204° C(400° F). Add 150 mL ofwater to a 400-mLbeaker. Place the beakeron the heater. Place theflask in the beaker andboil for 15 minutes. Aircool to roomtemperature and dilute tothe 100-mL mark withdeionized water. Invertseveral times to mix.

12. If the sample hasvisible turbidity, filter orwait until the turbiditysettles, and the upperportion of the sampleis clear.

Filter as follows:


b) Place the filter holderassembly in the filteringflask and wet the filter withdeionized water to ensureadhesion to the holder.



Continue with theanalysis using theappropriate procedurebelow.

41

n,sd.

ted

the

er.

n

e






Note: Use pH paper to insure the pH is 3. If it is higher than 4, do not readjust withacid; start over with a fresh aliquot.


Note: High iron content will cause precipitation (brown cloud) which will co-precipitate other metals. Repeat this procedure with a smaller aliquot volume.






3. Add 8 N KOH Standard Solution, one drop at a time, swirling betweeeach addition, until the first flash of pale blue appears (pH 3).




42

the


6. Add deionized water to the volume indicated in thecolorimetric procedure.


Sample and Analysis Volume Tables for Aqueous LiquidsThe values in these tables reflect the Hach Spectrophotometer withnarrowest concentration range.

Aluminum, Aluminon (Method 8012)

A = mg/L reading from instrument

B = mL sample amount from table

C = mL analysis volume from table

Aluminum, ECR (Method 8326)




Expected Alconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.1-5 40.0 20.0 50.0 mL

0.5-20 20.0 10.0 50.0 mL

2.0-80 10.0 5.00 50.0 mL

20-800 5.00 1.00 50.0 mL

200-8000 1.00 0.50 50.0 mL

Expected Alconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.05-1.3 40.0 20.0 50.0 mL

0.2-5.5 20.0 10.0 50.0 mL

0.8-22 10.0 5.00 50.0 mL

8.0-220 5.00 1.00 50.0 mL

80-2200 1.00 0.50 50.0 mL

A 5000×B C×

------------------------ mg/L Total Al=

A 5000×B C×

------------------------ mg/L Total Al=

43


Cadmium, Dithizone (Method 8017)

A = µg/L reading from instrument



Chromium, Total (Method 8024)




Expected Cdconc. (µg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.05-2.5 40.0 20.0 250 mL

0.2-10 20.0 10.0 250 mL

1-40 10.0 5.00 250 mL

10-400 5.00 1.00 250 mL

100-4000 1.00 0.50 250 mL

Expected Crconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.05-1.8 40.0 20.0 25.0 mL

0.20-7.5 20.0 10.0 25.0 mL

0.75-30 10.0 5.00 25.0 mL

7.5-300 5.00 1.00 25.0 mL

75-3000 1.00 0.50 25.0 mL

A 25×B C×----------------- µg/L Total Cd=

A 2500×B C×

------------------------ mg/L Total Cr=

44


Cobalt (Method 8078)




Copper, Bicinchoninate (Methods 8026 and 8506)




Expected Coconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.1-6.0 40.0 20.0 25.0 mL

0.5-25 20.0 10.0 25.0 mL

2.0-100 10.0 5.00 25.0 mL

20-1000 5.00 1.00 25.0 mL

200-10000 1.00 0.50 25.0 mL

Expected Cuconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.25-15 40.0 20.0 25.0 mL

1-60 20.0 10.0 25.0 mL

4-240 10.0 5.00 25.0 mL

40-2400 5.00 1.00 25.0 mL

400-24000 1.00 0.50 25.0 mL

A 2500×B C×

------------------------ mg/L Total Co=

A 2500×B C×

------------------------ mg/L Total Cu=

45


Iron, 1,10 Phenanthroline (Method 8008)




Iron, Ferrozine (Method 8147)




Expected Feconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.15-8 40.0 20.0 25.0 mL

0.6-35 20.0 10.0 25.0 mL

2.5-125 10.0 5.00 25.0 mL

25-1250 5.00 1.00 25.0 mL

250-12500 1.00 0.50 25.0 mL

Expected Feconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.07-4 40.0 20.0 25.0 mL

0.3-15 20.0 10.0 25.0 mL

1.1-65 10.0 5.00 25.0 mL

11-650 5.00 1.00 25.0 mL

110-6500 1.00 0.50 25.0 mL

A 2500×B C×

------------------------ mg/L Total Fe=

A 2500×B C×

------------------------ mg/L Total Fe=

46


Lead, Dithizone (Method 8033)

A = µg/L reading from instrument



Manganese, PAN (Method 8149)




Expected Pbconc. (µg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.1-5.0 40.0 20.0 250 mL

0.4-20 20.0 10.0 250 mL

1.5-80 10.0 5.00 250 mL

15-800 5.00 1.00 250 mL

150-8000 1.00 0.50 250 mL

Expected Mnconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.05-2.1 40.0 20.0 25.0 mL

0.2-8.7 20.0 10.0 25.0 mL

0.8-35 10.0 5.00 25.0 mL

8-350 5.00 1.00 25.0 mL

80-3500 1.00 0.50 25.0 mL

A 25×B C×----------------- µg/L Total Pb=

A 2500×B C×

------------------------ mg/L Total Mn=

47


Nickel, PAN (Method 8150)




Nitrogen TKN (Method 8075)

*These are guidelines only. See the spectrophotometer procedure manual.




Expected Niconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.05-3 40.0 20.0 25.0 mL

0.2-12 20.0 10.0 25.0 mL

0.8-47 10.0 5.00 25.0 mL

8-470 5.00 1.00 25.0 mL

80-4700 1.00 0.50 25.0 mL

ExpectedNitrogen

conc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.5-28 40.0 10.0* 25.0 mL*

2-112 20.0 5.00* 25.0 mL*

11-560 10.0 2.00* 25.0 mL*

45-2250 5.00 1.00* 25.0 mL*

425-22500 1.00 0.50* 25.0 mL*

A 2500×B C×

------------------------ mg/L Total Ni=

A 75×B C×----------------- mg/L TKN=

48


Phosphorus, Ascorbic Acid (Method 8048)




Potassium (Method 8049)




Expected PO 4conc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.12-6 40.0 20.0 25.0 mL

0.5-23 20.0 10.0 25.0 mL

2-90 10.0 5.00 25.0 mL

20-900 5.00 1.00 25.0 mL

200-9000 1.00 0.50 25.0 mL

Expected Kconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

4-20 40.0 20.0 25.0 mL

15-80 20.0 10.0 25.0 mL

60-300 10.0 5.00 25.0 mL

200-1000 5.0 3.00 25.0 mL

600-3000 5.00 1.00 25.0 mL

2000-10000 3.0 0.500 25.0 mL

6000-30000 1.00 0.50 25.0 mL

A 2500×B C×

------------------------ mg/L Total PO4=

A 2500×B C×

------------------------ mg/L Total K=

49


Silver (Method 8120)




Zinc (Method 8009)




Expected Agconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.08-3.7 40.0 20.0 50.0 mL

0.3-15 20.0 10.0 50.0 mL

1.0-60 10.0 5.00 50.0 mL

12-600 5.00 1.00 50.0 mL

120-6000 1.00 0.50 50.0 mL

Expected Znconc. (mg/L)

Sampleamount (mL)

AnalysisVolume (mL)

Dilute to

0.2-12.5 40.0 20.0 50.0 mL

0.8-50 20.0 10.0 50.0 mL

3.0-200 10.0 5.00 50.0 mL

30-2000 5.00 1.00 50.0 mL

300-20000 1.00 0.50 50.0 mL

A 5000×B C×

------------------------ mg/L Total Ag=

A 5000×B C×

------------------------ mg/L Total Zn=

50




52

DIGESTION PROCEDURE FOR OILS

1. Transfer 0.25 g orless of sample into a100-mL Digesdahldigestion flask; seeSample and AnalysisVolume Tables for Oilsfollowing thisprocedure.

Note: Take care toensure you have ahomogenous sample.

2. Add 4 mLconcentrated sulfuricacid (spec. gravity 1.84)to the digestion flask.

Note: Use only HachDigesdahl digestion flasks.Volumetric flasks withconcave bottom should notbe used.

Note: Safety glasses anda safety shield placedbetween the operator andthe Digesdahl are required.



4. Place the flask weightfollowed by thefractionating columnwith funnel on the flask.Place the flask on theheater and boil 4minutes.Do not boil todryness! If sulfuric acidis not present in theflask after the boilingperiod, do not proceedto Step 5!Discard thesample and use moresulfuric acid for thedigestion procedure inStep 2. Or choose asmaller sample size fordigestion from theSample and AnalysisVolume Tables for Oils,following this procedure.

Note: If sample foams upinto the neck of the flask,lower temperature to335° C (635° F). Continueheating at lowertemperature until allwater is evaporated. Thenreturn to originaldigestion temperature.

53

DIGESTION PROCEDURE FOR OILS, continued

5. Do not proceed ifsulfuric acid is not visiblein the flask. Add 10 mLof 50% hydrogenperoxide to the charredsample via the funnel onthe fractionating head.


Note: If the digest does notturn colorless, add 5 mLincrements of peroxide untilthe digest becomes clear ordoes not change color.

Note: If sample foamsduring hydrogen peroxideaddition, stop the peroxideflow and remove thedigestion flask andfractionating column (usefinger cots). Cool for30 seconds and returnapparatus to the heatingblock. Start peroxideaddition with 2 mL,then follow with theremaining peroxide.


Note: If the sample goes todryness, turn off theDigesdahl and air coolcompletely. Add waterto flask before handling.Repeat digestion from thebeginning using a newsample.

7. Take the hot flask offthe heater and allow theflask to air cool. Removethe fractionating columnfrom the digestion flask.


8. Dilute the digestto approximately 70 mLwith deionized water.

Note: Add demineralizedwater slowly at first. Coolthe flask if necessaryfor handling.

54


Metals Method

Note: If analyzing aliquots smaller than 0.5 mL, pH adjustment is not necessary.

1. Pipet the appropriate analysis volume into the appropriate mixinggraduate cylinder. See Sample and Analysis Volume Tables for Oilsfollowing the specific digestion to determine the analysis volume.

Note: Some methods require pipetting into a volumetric flask or a regulargraduated cylinder.


9. If analyzing foraluminum, nickel oriron, continue to Step10. If analyzing for othersubstances, dilute to the100-mL mark withdeionized water; SkipStep 10 and go toStep 11.

10. Turn thetemperature dial to aheat setting of 204° C(400° F). Add 150 mL ofwater to a 400-mLbeaker. Place the beakeron the heater. Place theflask in the beaker andboil for15 minutes. Coolto room temperature anddiluteto the mark withdemineralized water.Invert several timesto mix.

Note: When using aDigesdahl DigestionApparatus system withouttemperature control dials,reset to a lower setting thatgently boils the water.

11. If the sample isvisibly turbidity, filter orwait until the turbiditysettles, and the upperportion of the sample isclear.

Filter as follows:


b) Place the filter holderassembly in the filteringflask and wet the filterwith demineralized waterto ensure adhesion tothe holder.



12.Continue theanalysis using theappropriate procedurebelow.

55

n,sd.

ted

the

er.

n

e







Note: High iron content will cause precipitation (brown cloud) which will co-precipitateother metals. Repeat this procedure with a smaller aliquot volume.










56

the


6. Add deionized water to the volume indicated in thecolorimetric procedure.


Sample and Analysis Volume Tables for OilsThe values in these tables reflect the Hach Spectrophotometer withnarrowest concentration range.



B = g sample amount from table






Expected Alconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

15-800 0.250 20.0

40-2000 0.200 10.0

100-5300 0.150 5.00

1000-40000 0.100 1.00


Sampleamount (g)

AnalysisVolume (mL)

7-220 0.250 20.0

20-550 0.200 10.0

50-1400 0.150 5.00

400-11000 0.100 1.00

A 5000×B C×

------------------------ mg/kg Total Al=

A 5000×B C×

------------------------ mg/kg Total Al=

57



A = µg/l reading from instrument



Chromium, Total (Method 8024)




Expected Cdconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

10-400 0.250 20.0

25-1000 0.200 10.0

65-2600 0.150 5.00

480-20000 0.100 1.00

Expected Crconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

8-300 0.250 20.0

20-750 0.200 10.0

50-2000 0.150 5.00

350-15000 0.100 1.00

A 25×B C×----------------- mg/kg Total Cd=

A 2500×B C×

------------------------ mg/kg Total Cr=

58










Expected Coconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

15-950 0.250 20.0

45-2400 0.200 10.0

120-6200 0.150 5.00

880-46000 0.100 1.00

Expected Cuconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

40-2300 0.250 20.0

100-6000 0.200 10.0

320-15000 0.150 5.00

2000-110000 0.100 1.00

A 2500×B C×

------------------------ mg/kg Total Co=

A 2500×B C×

------------------------ mg/kg Total Cu=

59










Expected Feconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

25-1400 0.250 20.0

60-3500 0.200 10.0

160-9300 0.150 5.00

1200-70000 0.100 1.00


Sampleamount (g)

AnalysisVolume (mL)

11-650 0.250 20.0

30-1600 0.200 10.0

75-4300 0.150 5.00

560-32000 0.100 1.00

A 2500×B C×

------------------------ mg/kg Total Fe=

A 2500×B C×

------------------------ mg/kg Total Fe=

60










Expected Pbconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

15-800 0.250 20.0

38-2000 0.200 10.0

100-5300 0.150 5.00

750-40000 0.100 1.00

Expected Mnconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

7-350 0.250 20.0

20-870 0.200 10.0

50-2300 0.150 5.00

400-17000 0.100 1.00

A 25×B C×----------------- mg/kg Total Pb=

A 2500×B C×

------------------------ mg/kg Total Mn=

61











Expected Niconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

7-470 0.250 20.0

20-1200 0.200 10.0

50-3100 0.150 5.00

350-23000 0.100 1.00

Expected Nitrogenconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

85-4500 0.250 10.0*

210-11000 0.200 5.00*

2100-110000 0.100 1.00*

A 2500×B C×

------------------------ mg/kg Total Ni=

A 75×B C×----------------- mg/kg TKN=

62










Expected PO 4conc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

20-900 0.250 20.0

50-2300 0.200 10.0

130-6200 0.150 5.00

1000-45000 0.100 1.00

Expected Kconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

600-3400 0.250 20.0

1500-8500 0.200 10.0

4100-22000 0.150 5.00

15500-85000 0.100 2.00

31000-170000 0.100 1.00

A 2500×B C×

------------------------ mg/kg Total PO4=

A 2500×B C×

------------------------ mg/kg Total K=

63






Zinc (Method 8009)




Expected Agconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

12-600 0.250 20.0

30-1500 0.200 10.0

80-4000 0.150 5.00

620-30000 0.100 1.00

Expected Znconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

30-2000 0.250 20.0

80-5000 0.200 10.0

200-13000 0.150 5.00

1600-100000 0.100 1.00

A 5000×B C×

------------------------ mg/kg Total Ag=

A 5000×B C×

------------------------ mg/kg Total Zn=

64




66

DIGESTION PROCEDURE FOR SOLIDS

1. Transfer 0.50 g orless of sample into a100-mL Digesdahldigestion flask; seeSample and AnalysisVolume Tables forSolids followingthis procedure.

Note: Be sure you have ahomogenous sample. Solidsample should be finelyground or chopped andmixed well.

2. Add 4 mLconcentrated sulfuricacid (spec. gravity 1.84)to the digestion flask.

Note: Use only HachDigesdahl digestion flasks.Volumetric flasks withconcave bottom should notbe used.

Note: Safety glasses and asafety shield placedbetween the operator andthe Digesdahl are required.



4. Place the flask weightfollowed by thefractionating columnwith funnel on the flask.Place the flask on theheater and boil 4minutes.Do not boil todryness! If sulfuric acidis not present in theflask after the boilingperiod, do not proceedto Step 5!Discard thesample and use moresulfuric acid for thedigestion procedure inStep 2. Or choose asmaller amount from theSample and AnalysisVolume Tables forSolids.

Note: If sample foams upinto the neck of the flask,lower temperature to335° C (635° F). Continueheating at lowertemperature until allwater is evaporated. Thenreturn to originaldigestion temperature.

Note: White acid vaporsaccompanied with a refluxline indicate that thesulfuric acid is boiling

Note: Some organicsamples may need morethan 5 minutes forcomplete digestion.

67

DIGESTION PROCEDURE FOR SOLIDS, continued

5. Do not proceed ifsulfuric acid is notvisible in the flask. Add10 mL of 50% hydrogenperoxide to the charredsample via the funnel onthe fractionatingcolumn.

Note: Do not heat to dryness.


Note: If the digest does notturn colorless, add 5 mLincrements of peroxide untilthe digest becomes clear ordoes not change color.

Note: If sample foamsduring hydrogen peroxideaddition, stop the peroxideflow and remove thedigestion flask andfractionating column(use finger cots). Cool for30 seconds and returnapparatus to the heatingblock. Start peroxideaddition with 2 mL,then follow with theremaining peroxide.

6. After addition ofhydrogen peroxide iscomplete, boil off excesshydrogen peroxide byheating for one moreminute .Do not heat todryness.Note: If the sample goes todryness, turn off theDigesdahl and air cool toroom temperature. Addwater to flask beforehandling. Repeat thedigestion from thebeginning using a newsample.

7. Take the hot flask offthe heater and allow theflask to air cool.Remove thefractionating columnfrom the digestion flask.


8. Dilute the digest toapproximately 70 mLwith deionized water.

Note: Add deionizedwater slowly at first. Coolthe flask if necessaryfor handling.

68

ids


Metals MethodNote: If analyzing aliquots smaller than 0.5 mL, pH adjustment is not necessary.

1. Pipet the appropriate analysis volume into the appropriate mixinggraduate cylinder. See Sample and Analysis Volume Tables for Solfollowing the specific digestion to determine the analysis volume.


9. If analyzing foraluminum, nickel oriron, continue to Step10. If analyzing for othersubstances, dilute to the100-mL mark withdeionized water; skipStep 10 and go toStep 11.

10. Turn the temperaturedial to a heat setting of204° C (400° F). Add150 mL of water to a400-mL beaker. Placethe beaker on the heater.Place the flask in thebeaker and boil for 15minutes. Air cool toroom temperature anddilute to the mark withdeionized water. Invertseveral times to mix.

Note: When using aDigesdahl DigestionApparatus system withouttemperature control dials,reset to a lower setting thatgently boils the water.

11. If the sample hasvisible turbidity, filter orwait until the turbiditysettles, and the upperportion of the sampleis clear.

Filter as follows:


b) Place the filter holderassembly in the filteringflask and wet the filterwith deionized water toensure adhesion tothe holder.



Note: If small aliquots(≤ 1.0 mL) are analyzed,filtration is not needed.

12.Continue with theanalysis using theappropriate procedurebelow.

69

n,sd.

ted

the

er.

n

e








Note: High iron content will cause precipitation (brown cloud) which will co-precipitateother metals. Repeat this procedure with a smaller aliquot volume.










70

the


6. Add deionized water to the volume indicated in the colorimetricprocedure.


Sample and Analysis Volume Tables for SolidsThe values in these tables reflect the Hach Spectrophotometer withnarrowest concentration range.










Sampleamount (g)

AnalysisVolume (mL)

10-400 0.500 20.0

25-1000 0.400 10.0

65-2600 0.300 5.00

480-20000 0.200 1.00

1900-80000 0.100 0.50


Sampleamount (g)

AnalysisVolume (mL)

4-100 0.500 20.0

10-270 0.400 10.0

25-730 0.300 5.00

180-5500 0.200 1.00

750-22000 0.100 0.50

A 5000×B C×

------------------------ mg/kg Total Al=

A 5000×B C×

------------------------ mg/kg Total Al=

71






Chromium, Total (method 8024)




Expected Cdconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

5-200 0.500 20.0

12-500 0.400 10.0

30-1300 0.300 5.00

240-10000 0.200 1.00

960-40000 0.100 0.50

Expected Crconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

4.9-150 0.500 20.0

10-370 0.400 10.0

25-1000 0.300 5.00

190-7500 0.200 1.00

750-30000 0.100 0.50

A 25×B C×----------------- mg/kg Total Cd=

A 2500×B C×

------------------------ mg/kg Total Cr=

72










Expected Coconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

10-450 0.500 20.0

20-1200 0.400 10.0

50-3000 0.300 5.00

500-20000 0.200 1.00

2000-100000 0.100 0.50

Expected Cuconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

20-1200 0.500 20.0

50-3000 0.400 10.0

120-7500 0.300 5.00

1000-60000 0.200 1.00

4000-240000 0.100 0.50

A 2500×B C×

------------------------ mg/kg Total Co=

A 2500×B C×

------------------------ mg/kg Total Cu=

73











Sampleamount (g)

AnalysisVolume (mL)

12-700 0.500 20.0

35-1700 0.400 10.0

85-4500 0.300 5.00

650-35000 0.200 1.00

2500-140000 0.100 0.50


Sampleamount (g)

AnalysisVolume (mL)

6-300 0.500 20.0

15-800 0.400 10.0

40-2000 0.300 5.00

300-15000 0.200 1.00

1200-65000 0.100 0.50

A 2500×B C×

------------------------ mg/kg Total Fe=

A 2500×B C×

------------------------ mg/kg Total Fe=

74










Expected Pbconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

8-400 0.500 20.0

20-1000 0.400 10.0

50-2600 0.300 5.00

400-20000 0.200 1.00

1500-80000 0.100 0.50

Expected Mnconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

4-170 0.500 20.0

10-430 0.400 10.0

25-1100 0.300 5.00

200-8700 0.200 1.00

750-35000 0.100 0.50

A 25×B C×----------------- mg/kg Total Pb=

A 2500×B C×

------------------------ mg/kg total Mn=

75











Expected Niconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

4-220 0.500 20.0

10-580 0.400 10.0

25-1500 0.300 5.00

200-11000 0.200 1.00

750-45000 0.100 0.50

Expected Nitrogenconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

42-2200 0.500* 10.0*

106-5600 0.400* 5.00*

350-18000 0.300* 2.00*

1000-56000 0.200* 1.00*

4200-220000 0.100* 0.50*

A 2500×B C×

------------------------ mg/kg Total Ni=

A 75×B C×----------------- mg/kg TKN=

76










Expected PO 4conc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

10-450 0.500 20.0

25-1100 0.400 10.0

67-3100 0.300 5.00

500-23000 0.200 1.00

2000-93000 0.100 0.50

Expected Kconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

300-1700 0.500 20.0

800-4200 0.400 10.0

2000-11000 0.300 5.00

15000-85000 0.200 1.00

62000-300000 0.100 0.50

A 2500×B C×

------------------------ mg/kg Total PO4=

A 2500×B C×

------------------------ mg/kg Total K=

77






Zinc (Method 8009)




Expected Agconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

6-300 0.500 20.0

15-750 0.400 10.0

40-2000 0.300 5.0

300-15000 0.200 1.00

1200-60000 0.100 0.50

Expected Znconc. (mg/kg)

Sampleamount (g)

AnalysisVolume (mL)

16-1000 0.500 20.0

40-2500 0.400 10.0

100-6600 0.300 5.00

800-50000 0.200 1.00

3000-200000 0.100 0.50

A 5000×B C×

------------------------ mg/kg Total Ag=

A 5000×B C×

------------------------ mg/kg Total Zn–

78

MAINTENANCE

79

Some of the following manual sections contain warninglabels and require special attention.

Read and follow all warning instructions carefully to avoidpersonal injury and damage to the instrument. Onlyqualified personnel should conduct maintenanceprocedures on this instrument.

ordrtheh aofsed

1-02376-647-125-42340-855-2031-20

56-0091-00398-00421-0380336-20336-2165-0165-0230-18

10-0036-00926-0073-37378-00

SECTION 5 MAINTENANCE

5.1 Fuse ReplacementThe fuse holder is located on the back panel within the power creceptacle. SeeFigure 2.To replace a fuse, turn off the instrument poweand disconnect the power cord from the back panel. Removal ofvertical support is necessary. Remove the fuse holder by prying witsmall screwdriver or other pointed tool at the small opening at the topthe fuse holder. Replace the fuse with the same type and rating uoriginally. Refer toReplacement Parts.

5.2 Kit Replacement PartsDescription Unit Cat. No.Aspirator, without check valve, 3/8” NPT ..................................................each ............213Cooling Pad .................................................................................................each ..........1800Finger Cots ................................................................................................pkg/2 ..........1402Flask, digestion, 100 mL.............................................................................each ..........23Flask Weight................................................................................................each ..........4400Fractionating Head ......................................................................................each ..........22Fractionating Column Kit..............................................................................................231

Kit includes: Fractionating Head; Capillary Flow Funnel 8.3 cm(3.25”); Column Baffle; Tubing; C-Flex, 5 feet; Vent Trap Body; andVent Trap Cap

Funnel, Capillary Flow................................................................................each ..........228Fuse, 4 A, 125 V Slow-blow, for heater assembly ......................................each ..........445Fuse, 2 A, for 250 V heater assembly .........................................................each ..........44Goggles, safety ............................................................................................each ..........180Heat Shield ..................................................................................................each ..........18-00Heater Assembly, 115 V..............................................................................each ..........44Heater Assembly, 230 V..............................................................................each ..........44Heater Element Assembly, 120 V ...............................................................each ..........185Heater Element Assembly, 240 V ...............................................................each ..........185Instruction Manual ......................................................................................each ..........231Power Cord, 115 V, UL/CSA approved ......................................................each ..........180Power Cord, 230V, VDE-approved for European operation.......................each ..........468Receptacle, column .....................................................................................each ..........45Tubing, C-flex ........................................................................................25 feet ..........232Vertical Support, heater ...............................................................................each ..........44

81

GENERAL INFORMATION

83

At Hach Company, customer service is animportant part of every product we make.

With that in mind, we have compiled the followinginformation for your convenience.

96-49

72-56

200-3832-3851-00

57-34421-0074-00

130-20130-21

44-453-04-320-4944-2682-490-265-379-26

104-00104-02500-4861-75

620-1689-0008-41

1-37-4130-00

340-00

REPLACEMENT PARTS

REQUIRED REAGENTSQuantityRequired

Description Per Digestion Unit Cat. No.Hydrogen Peroxide, 50% ................................................... 10 mL .......... 500 mL .......211Sulfuric Acid, ACS,

(concentrated, spec. gravity 1.84)..............................≥ 2.5 mL .............. 4 kg ...........979-09Water, demineralized...........................................................varies...................4 L ...........2

REQUIRED APPARATUSDispenser, pour-out, 10 mL.................................................... 1.....................each .......22Pipet, serological, 10 mL........................................................ 1.....................each ...........5Pipet filler, safety bulb ........................................................... 1.....................each .......146Boiling chips, silicon carbide..............................................varies...............500 g .......205Safety glasses ......................................................................... 1.....................each .......18Safety shield, for Digesdahl ................................................... 1.....................each .......209

Select one based on available voltage:Digesdahl Apparatus, 115 Vac .......................................................................each .......23Digesdahl Apparatus, 230 Vac .......................................................................each .......23

OPTIONAL REAGENTSDescription Unit Cat. No.Hydrogen Peroxide, 30% ......................................................................... 200 mL ...........1Kjeldahl Reduction Reagent (for fluid fertilizers) .........................................40 g .......23652, 4-Dinitrophenol Indicator Solution ............................................ 100 mL MDB .........1348Nitric Acid Solution, 1:1 .......................................................................... 500 mL .........254Potassium Hydroxide, 1 N ..............................................................50 mL SCDB .......231Potassium Hydroxide Standard Sol’n, 8 N............................................... 500 mL ...........2Sodium Hydroxide, 5 N ................................................................50 mL* SCDB .........245Sodium Hydroxide, 1 N ............................................................... 118 mL* MDB .........104TKN Indicator Solution...................................................................50 mL SCDB .......2251

OPTIONAL APPARATUSDescription Unit Cat. No.Balance, Precision, 115 V ..............................................................................each .......26Balance, Precision, 230 V ..............................................................................each .......26Beaker, 400 mL ..............................................................................................each ...........Beaker, Berzelius, 200 mL .........................................................................12/pkg .......227Bottle, Wash, 1 L............................................................................................each ...........Bulb, dropper, 2 mL ...................................................................................12/pkg .......211Cylinder, graduated, 50 mL............................................................................each ...........5Dispenser, 1-5 mL (for H2SO4, meat)............................................................each .......2312Dispenser, 10-50 mL (for H2SO4, meat)........................................................each .......23121Filter discs, glass, 47 mm.........................................................................100/pkg .........25Filter holder, membrane .................................................................................each .........2

85

46-4925-42266-00266-0289-00

289-0238-0091-33234-010-10561-64492-0053-514-004-0280-0533-3378-97

REPLACEMENT PARTS, continued

OPTIONAL APPARATUS (continued)Description Unit Cat. No.Flask, filter, 500 mL....................................................................................... each........... 5Flask, flat-bottom volumetric, 100 mL.......................................................... each....... 231Fume Scrubber Apparatus, 115 V.................................................................. each....... 23Fume Scrubber Apparatus, 230 V.................................................................. each....... 23Oven, laboratory, 120 V................................................................................. each....... 142Oven, laboratory, 230V.................................................................................. each....... 14Paper, weighing, 76 x 76 mm .................................................................. 500/pkg....... 147pH paper, pH 1-11..................................................................................5 roll/pkg........... 3Pipet, Pasteur, disposable, 229 mm.......................................................... 200/pkg....... 21sension™1 Basic Portable pH Meter, with electrode ................................... each....... 5170Spatula, stainless, 10 cm................................................................................ each...........Spoon, measuring, 0.05 g............................................................................... each...........Stir bar, PTFE, 1”........................................................................................... each....... 209Stir plate, magnetic, 7X7, 115 Vac................................................................. each....... 2344Stir plate, magnetic, 7X7, 230 Vac................................................................. each....... 2344Stopper, hollow, size #5 ............................................................................... 6/pkg....... 144Syringe, 5 mL, plastic .............................................................................. 100/pkg....... 234Watch Glass, 65 mm .................................................................................. 12/pkg........... 5

86

HOW TO ORDER

87

REPAIR SERVICE

88

WARRANTY

89

digesdahl® digestion apparatus models 23130-20, -21-instrument manual (1)

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