digesdahl® digestion apparatus models 23130-20, manual

7/28/2019 Digesdahl Digestion Apparatus Models 23130-20, Manual

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23130-18

Digesdahl DigestionApparatus

Models 23130-20, -21

Instrument Manual

Hach Company, 1989-91, 1995-97, 1999. All r ights r eserved. Pr inted 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, inspectedand found to meet its published specifications when it was shipped fromthe 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 61010-1 (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 compliance byHach 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 recordsby TV Product Services and Hach Company, certified compliance by

Hach 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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Canadian Interference-Causing Equipment Regulation, IECS-003,

Class A:

Supporting test records by TV Product Services, certified complianceby Hach Company.

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

Cet appareil numrique de la classe A respecte toutes les exigences duRglement sur le matriel brouilleur du Canada.

FCC Part 15, Class "A" Limits: Supporting test records by TV ProductServices, 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 may

cause undesired operation.

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

This equipment has been tested and found to comply with the limits for aClass A digital device, pursuant to Part 15 of the FCC Rules. These limitsare designed to provide reasonable protection against harmfulinterference when the equipment is operated in a commercialenvironment. This equipment generates, uses, and can radiate radio

frequency 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 ofthe 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 interference.

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

5. Try combinations of the above.

CERTIFICATION, continued


5/100v

TABLE OF CONTENTS

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

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

SAFETY PRECAUTIONS .................................................................................................... viii

OPERATION

SECTION 1 GENERAL DESCRIPTION ............................................................................ 3

1.1 Introduction......................................................................................................................... 3

1.2 Scope of Instructions........................................................................................................... 3

SECTION 2 PREPARATION FOR USE .............................................................................. 5

2.1 Unpacking ........................................................................................................................... 5

2.2 Assembly............................................................................................................................. 6

2.2.1 Heater Assembly........................................................................................................ 62.2.2 Fractionating Head System........................................................................................ 7

2.3 Selecting a Temperature Setting.......................................................................................... 9

SECTION 3 SAFETY & ENVIRONMENTAL CONSIDERATIONS ............................. 11

3.1 Digesdahl Digestion Apparatus......................................................................................... 11

3.2 Using Hydrogen Peroxide ................................................................................................. 12

3.3 Using Sulfuric Acid........................................................................................................... 14

3.4 Clean Up of Spills and Leaks............................................................................................ 143.5 Waste Management ........................................................................................................... 15

CONSIDERATIONS DE SECURITE ET DENVIRONNEMENT....................................... 16

3.6 Minralisateur Digesdahl .................................................................................................. 16

3.7 Utilisation de leau oxygne............................................................................................ 17

3.8 Utilisation de lacide sulfurique ........................................................................................ 19

3.9 Nettoyage des dversements et fuites................................................................................ 20

SECTION 4 OPERATION ................................................................................................... 21

4.1 Apparatus Preparation....................................................................................................... 214.2 Digestion ........................................................................................................................... 21

4.2.1 Appropriate Sample Size ......................................................................................... 224.2.2 Proper Digestion Solution Temperature .................................................................. 224.2.3 Sufficient Sulfuric Acid ........................................................................................... 224.2.4 Carbonization Period ............................................................................................... 244.2.5 Adequate Peroxide Concentration for Sufficient Time............................................ 244.2.6 Containment of Sample ........................................................................................... 25


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TABLE OF CONTENTS, continued

4.2.7 Sampling and Storage.............................................................................................. 254.2.8 Accuracy Check ...................................................................................................... 25

DIGESTION PROCEDURES

GENERAL DIGESDAHL DIGESTION ............................................................................. 29

SAMPLE TYPE AND SIZE................................................................................................... 35

DIGESTION PROCEDURE FOR AQUEOUS LIQUIDS................................................. 39

DIGESTION PROCEDURE FOR OILS............................................................................. 53

DIGESTION PROCEDURE FOR SOLIDS ....................................................................... 67

MAINTENANCE

SECTION 5 MAINTENANCE............................................................................................ 81

5.1 Fuse Replacement ............................................................................................................. 81

5.2 Kit Replacement Parts ...................................................................................................... 81

GENERAL INFORMATION

REPLACEMENT PARTS....................................................................................................... 85

HOW TO ORDER .................................................................................................................. 87

REPAIR SERVICE ................................................................................................................. 88

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 powerwhen using poly-phase power.


8/100viii

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

Pay particular attention to Section 3! Failure to do so could result in

serious injury to the operator or damage to the equipment.

The digestion procedures in this manual involve the use of strong acid

and oxidizer at high temperatures. To avoid personal injury, observe

all warning messages.

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

DANGER

Indicates either a potentially or imminently hazardous situation which,

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

CAUTION

Indicates either a potentially or imminently hazardous situation which,

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

NOTE

Information that requires special emphasis.

Precautionary Labels

Please pay particular attention to labels and tags attached to the instrument.

Personal injury or damage to the instrument could occur if not observed.

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

SAFETY PRECAUTIONS


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OPERATION

DANGERHandling chemical samples, standards, and reagents can be dangerous. Review thenecessary Material Safety Data Sheets and become familiar with all safety procedures

before handling any chemicals.

DANGERLa manipulation des chantillons chimiques, talons et ractifs peut tre dangereuse.

Lire les fiches de donnes de scurit des produits ncessaires et se familiariser avec

toutes les procdures de scurit avant de manipuler tout produit chimique.


10/1002


11/1003

SECTION 1 GENERAL DESCRIPTION

1.1 IntroductionThe Hach Digesdahl Digestion Apparatus shown in Figure 1 is designedto digest a wide variety of sample types for subsequent determination oftotal Kjeldahl nitrogen, several minerals, and nutrients. Sample typesinclude food products, feeds, grains, wastewater sludges, plating baths,

plant 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.

DANGER

This product does not have thermal run-away protection when using

polyphase AC main power systems. Use this instrument only with singlephase 230 VAC systems.

DANGER

Ce produit na pas de protection contre la surchauffe lorquil est utilis

sur une alimentation lectrique en triphas. Utiliser cet appareil

seulement sur alimentation 230 V monophas.

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 Apparatusvary according to the type and form of the sample. Digestions for liquids,oils and solids are found in this manual.


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Figure 1 Digesdahl Digestion Apparatus

CAPILLARY

FUNNEL

VENT TRAPCAP

HEATERASSEMBLY

CAPILLARYFUNNELADAPTOR

POWERSWITCH

TEMPERATURECONTROL

DIGESTIONFLASK

FLASKWEIGHT

SAFETYSHIELD

COLLUMNBAFFLE

VENT TRAPBODY

FRACTIONATINGCOLUMN

COLUMNRECEPTACLE

VERTICALSUPPORT

HEATSHIELD

TEMPERATUREINDICATOR

MODESWITCH


13/1005

SECTION 2 PREPARATION FOR USE

2.1 UnpackingRemove the Digesdahl Digestion Apparatus and accessories from theshipping container and inspect each item for any damage that may haveoccurred 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 ServiceDepartment, Hach Company, Loveland, Colorado (the toll-free number is800-227-4224). For customers outside the U.S.A., contact the Hach officeor authorized distributor serving you. Please do not return the instrumentwithout prior authorization from Hach.


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2.2 Assembly2.2.1 Heater Assembly

Assemble the heater assembly as shown in Figure 2.

Figure 2

Heater Assembly


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2.2.2 Fractionating Head System

The fractionating head system is shown in Figure 3 and includes thefractionating column, column baffle, the capillary funnel, and the exhaustsystem components. Assemble as follows:

1. Place the fractionating column in the column receptacle (shown in

Figure 2) and place the column baffle in the top of the column with thetapered end up.

2. Insert the capillary funnel adapter into the largest opening of the venttrap 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 activated

carbon filter. This filter is replaced when the absorbing capacity is exhausted. The

Fume 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 on thefractionating 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 hosebarb fitting in the aspirator side port and install the extension tube.

DANGERThe Hach Fume Scrubber Apparatus can only be used with the

Digesdahl Digestion Apparatus for sulfuric acid digestions. Hazardousconditions could develop if fumes from an alternate acid are vented withthe Fume Scrubber. It is important to clean the Fume Scrubber aftereach use to prevent corrosion (see Operation section of FumeScrubber manual).

DANGERL'purateur de fumes Hach peut seulement tre utilis avec leminralisateur Digesdahl pour des minralisarions l'acide sulfurique.Des conditions de risque peuvent tre cres par l'aspiration de vapeursd'un autre acide dans l'purateur de fumes. Il est important de

nettoyer l'purateur de fumes aprs chaque utilisation pour viterla corrosion.

7. A 6.25-foot length of C-flex tubing is supplied with the aspirator. Cuta segment approximately 16 inches long and connect the top stem ofthe column receptacle to the vent trap body. Cut another segment fromthe remaining tubing to connect the aspirator to the lower stem of thecolumn 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 3

Fractionating Column andExhaust Assembly


17/1009

2.3 Selecting a Temperature Setting

Note: During adigestion, the

temperature

reading will vary

slightly above and

below theselected

temperature. This

will not affect the

digestion or theaccuracy of the

final analysis.

When idling (no

digestion flask in

place), the

temperature may

fluctuate15C

from the set point.

The particular temperature applicable for the sample to be digested isgiven in the appropriate analysis procedure manual. The steps belowexplain how to set the heater temperature.

1. Connect the power cord to the line voltage receptacle and set the

POWER 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. With theMode switch in the READ position, the temperature display shows the

current operating temperature.


18/10010


19/10011

SECTION 3 SAFETY & ENVIRONMENTAL

CONSIDERATIONS

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 Apparatus

For 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 procedures.

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 andcool 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 Digesdahls safety shield inplace during use.

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

For respiratory protection, use a fume hood or Hachs Fume ScrubberApparatus (Cat. No. 23266).

Always wear safety glasses or goggles- be sure they have side shields.

Wear protective gloves for during digestion procedures. Use tongs orfinger cots to transfer hot apparatus.

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

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


20/10012

When digesting a new substance for the first time, begin with a smallersize 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 shoesshould 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 maycause hot glassware to shatter.

3.2 Using Hydrogen PeroxideDANGERHydrogen 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 asspecified in the Hach instructions.

Do not add hydrogen peroxide directly to the column on the digestionflask. Always add hydrogen peroxide in a slow and controlled manner;use 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 never

be stored near flammable materials. Like sulfuric acid, it can cause burnsand 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.


21/10013

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 andparticularly to the eyes. It will cause chemical burns at industrial

concentrations 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 hydrogenperoxide 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.).


22/10014

Do not use unapproved materials (brass, copper, carbon steel, rubber,etc.) 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 bottleof hydrogen peroxide. As a precaution, the reagent bottles are shipped in a

plastic bag. If there is evidence of leakage during shipment, wear gloveswhen 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 SafetyData 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 and

strong oxidizer; it can cause burns if splashed on the skin and permanentdamage if eye contact occurs. This caustic action is much more severe ifthe 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 carcinogen.

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

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

A spill, overflow, or eruption from the Digesdahl apparatus may leave aresidue on the equipment or other surfaces. Cleaning the residue must be

done cautiously. Do not use alternative cleaning methods or cleaningagents not authorized or endorsed by Hach Company; they may damagethe 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 cause theglass to shatter. Let the apparatus cool before cleaning it.


23/10015

2. Unplug the Digesdahl before cleaning.

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

4. Wipe the exterior surfaces of the Digesdahl apparatus (heating mantle,electrical controls, etc.) and other laboratory surfaces several times

with 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 maybe contaminated from the sample or chemical residues.

3.5 Waste ManagementHazardous waste disposal regulations were promulgated in accordance

with the Resource Conservation and Recovery Act (RCRA) and are givenin Title 40 Code of Federal Regulations (CFR), parts 260 to 280. Wastemust be managed and disposed of in accordance with federal, state andlocal regulations. Refer to Section VIII of the Hach Material Safety DataSheet that come with reagents for basic disposal information on HachProducts. The USEPA maintains a hotline number for questions regardingRCRA. It is 1-800-424-9346

This manual does not contain all the regulatory requirements. Additionalstate and local laws may apply to waste that you generate. It is each

generators responsibility to know which regulations apply to them and toadhere to these regulations. Check with your environmental compliancestaff for specific instructions.

Section 3 summarizes basic requirements for safely handling thechemicals used in the Digesdahl digestion. It is a guide only and is notcomprehensive for all parties. The information is not intended to provideany 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.


24/10016

CONSIDERATIONS DE SECURITE ET DENVIRONNEMENT

Chaque personne effectuant des analyses de laboratoire est responsable dela scurit. Lanalyste doit dvelopper et appliquer de bonnes habitudesde scurit pour minimiser les risques daccidents en pratiquant de bonnestechniques de laboratoire.

3.6 Minralisateur Digesdahl

Pour une utilisation du Digesdahl en toute scurit, observer lesprcautions suivantes :

Poids dchantillon : Ne jamais minraliser un chantillon qui contientplus de 0,5 g de produit qui ne soit pas de leau.

Les huiles et liquides organiques doivent tre considrs comme dessolides pour la dtermination du poids dchantillon.

Type dacide : Utiliser seulement lacide spcifi dans les techniquesdtailles de Hach.

Volume dacide : Ne jamais utiliser moins de 3 ml.

Toujours suivre lordre des oprations indiqu.

Si la fiole va sec, la retirer immdiatement du systme de chauffageet la laisser refroidir la temprature ambiante. Ne jamais ajouterdeau oxygne une fiole dchantillon sec, une explosion

pourrait se produire. Si vous ntes pas sr que la fiole contienneassez dacide sulfurique, ARRETEZ. Ne pas ajouter deau oxygne.

Recommencer lopration avec une quantit dchantillon plus petiteou plus dacide.

Prendre soin de maintenir en place la chemine et le manchon descurit du Digesdahl pendant lutilisation.

Toujours effectuer les minralisations derrire un cran de protection(# 20974-00) ou sous une hotte ferme.

Pour une protection respiratoire, utiliser une hotte ou lpurateur de

fumes Hach (rf. n 23266).

Toujours porter des lunettes de scurit avec protections latrales.

Porter des gants pour la protection pendant les oprations de digestion.Utiliser des pinces ou des doigtiers de protection pour dplacer lesobjets chauds.


25/10017

NE PAS ajouter dalcool, dactone ou autre solvant organique dans lafiole de digestion avant ou aprs minralisation.

Pendant la digestion, utiliser le rglage de temprature et le temps dedigestion spcifi dans les instructions. Ne pas laisser le Digesdahlsans surveillance pendant lutilisation.

Lors de la minralisation dune nouvelle substance pour la premirefois, commencer avec une quantit plus petite avant dutiliser laquantit optimale pour lanalyse. Ne pas laisser le contenu de la fiolesvaporer sec.

Porter une blouse ou un tablier de laboratoire pour protger la peau etles vtements des projections.

Porter des chaussures appropries pour protger les pieds desdversements de produits. Ne pas porter de chaussures bout ouvert.

Ne pas utiliser de verrerie ou appareils endommags. Eliminer etremplacer tous les quipements endommags.

Laisser le Digesdahl refroidir naturellement (dans lair ambiant). Leaufroide peut briser le verre chaud.

3.7 Utilisation de leau oxygne

DANGER

Leau oxygne

(peroxyde

dhydrogne)

sous forme

concentre

prsente un

risque

dexplosion.

Utilisez ces prcautions de scurit supplmentaires spcifiques pourlutilisation de leau oxygne dans les minralisations par le Digesdahl :

NE PAS mlanger leau oxygne avec dautres ractifs saufindication prcise dans les procdures danalyse Hach.

NE PAS ajouter deau oxygne directement dans la colonne defractionnement sur la fiole de digestion. Ajouter toujours leauoxygne avec un dbit lent et rgulier, utiliser lentonnoir capillaire Hach.

Leau oxygne doit tre ajoute la matire organique carbonisedans la fiole, seulement en prsence dacide sulfurique.

NE PAS utiliser deau oxygne des concentrations suprieures 50%.


26/10018

Leau oxygne (30% ou 50%) est un oxydant puissant et ne doit jamaistre stock prs de matires inflammables. Comme lacide sulfurique,il peut provoquer des brlures la peau et aux yeux. En cas de contactavec les yeux ou la peau, laver les yeux et/ou la peau leau pendant

15 minutes. Retirer les vtements contamins. Appeler un mdecin.

Leau oxygne est extrmement corrosive et doit tre lave leau si elleest rpandue sur des appareils ou sur la paillasse. Lire et observer tous lesavertissements sur les tiquettes des ractifs et les fiches de donnes descurit des produits.

Les procdures de manipulations et de stockage concernant leauoxygne doivent tenir compte de deux caractristiques importantesdu produit :

Cest un agent fortement oxydant. La nature chimique de leau

oxygne en fait un produit irritant pour la peau, les muqueuseset particulirement les yeux. Il provoque des brlures graves auxconcentrations auxquelles il est utilis dans lindustrie et peutprovoquer une combustion spontane au contact immdiat ou prolongdes combustibles.

Il peut se dcomposer avec dgagement de chaleur et doxygne. Lavitesse de dcomposition naturelle du produit de qualit industriellecourante est trs lente, mais elle sacclre lorsquelle est contaminepar des substances telles que poussire, ions mtalliques, ou alcalines.

Prendre les prcautions suivantes pour la manipulation et le stockage deleau oxygne :

Stocker dans un endroit frais labri de la lumire directe du soleil(de prfrence dans un rfrigrateur).

Stocker dans les rcipients dorigine avec les bouchons fournis et lesmaintenir ferms lorsquils ne sont pas utiliss. (Sassurer que lesrcipients sont ventils. Les flacons deau oxygne Hach sont livrsavec un joint de bouchon permable spcial).

Porter des gants et des lunettes de scurit lors de la manipulationdu produit.

Utiliser des grains de carbure de silicium pour rgulariser lbullitionlors de la digestion dchantillons liquides.


27/10019

Laver la peau contamine rapidement grande eau. Retirer rapidementles vtements contamins et les laver soigneusement avant de lesrutiliser. Les laver rgulirement.

Laver les yeux grande eau sils sont contamins et consulter unmdecin immdiatement.

Consulter immdiatement un mdecin si le produit est ingr.

Laver toute trace rpandue grande eau.

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

NE PAS laisser le produit stock ou enferm dans un espace clos.

NE PAS inhaler les vapeurs ou ingrer le produit.

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

NE PAS laisser au contact avec des catalyseurs de dcomposition(mtaux, poussires, produits alcalins, etc.).

NE PAS utiliser de matriaux de construction inadapts (laiton,cuivre, acier, caoutchouc, etc.) pour les systmes de stockageet tuyauteries.

Les bouchons des flacons de ractifs sont prvus avec un joint poreuxspcial qui permet lchappement de gaz. Le bouchon dorigine doittoujours tre utilis sur le flacon deau oxygne. A titre de prcaution,les flacons de ractifs sont expdis dans un sac plastique. Sil existe destraces de fuites pendant le transport, porter des gants pour retirer le flacondu sac et rincer le flacon leau aprs lavoir sorti du sac. Rincer le sacavant limination.

3.8 Utilisation de lacide sulfuriqueLire et observer tous les avertissements sur les tiquettes des

produits et la fiche de donnes de scurit du produit qui accompagnelacide sulfurique.

Lacide sulfurique concentr utilis dans lopration de minralisationdoit tre manipul correctement et avec prcaution. Lacide sulfuriqueest un acide fort et un oxydant puissant qui peut provoquer des brluresgraves au contact de la peau et des lsions irrversibles sil est mis aucontact des yeux. Cette action corrosive est beaucoup plus grave si lacideest chaud. En cas de contact avec les yeux ou la peau, laver les yeux et/


28/10020

ou la peau leau pendant 15 minutes. Retirer les vtements

contamins. Appeler un mdecin.

Lacide sulfurique sous forme de brouillard ou de vapeur a t classcomme cancrigne possible pour lhomme par lAgence Internationalede Recherche sur le Cancer (IARC).

Lacide sulfurique est un oxydant puissant. Il peut provoquer un feu ouexploser au contact de nombreux produits chimiques diffrents. Suivre lesrgles de stockage appropries.

3.9 Nettoyage des dversements et fuitesPrendre les plus grandes prcautions pour nettoyer des fuites ou produitsrpandus pendant toute la technique de digestion. Votre socit peutexiger que seules des personnes habilites portant les quipements deprotection appropris (gants, lunettes de scurit, masques de protection

et vtements rsistants aux agents chimiques) interviennent en cas dedversement ou de fuite.

Un dversement, dbordement ou une projection par le minralisateurDigesdahl peut laisser un rsidu sur le matriel ou dautres surfaces. Lenettoyage du rsidu doit tre fait avec prcaution. Veuillez observer lesmesures de scurit ci-dessous :

1. NE PAS tenter de nettoyer lappareil pendant quil est chaud, cecipeut causer la rupture du verre. Laisser refroidir lappareil avant de

le nettoyer.

2. Dbrancher le Digesdahl avant de le nettoyer.

3. Porter des gants et des lunettes de protection pour la manipulation dela verrerie. Rincer soigneusement la verrerie plusieurs fois leau pourla dcontaminer.

4. Essuyer les surfaces extrieures de lappareil Digesdahl(plaque chauffante, commandes lectriques, etc.) et autressurfaces du laboratoire plusieurs fois avec un tissu humide ouun papier dessuyage.

5. Ne pas rincer ou arroser lappareil directement, ceci pourraitle dtriorer.

6. Eliminer les papiers et tissus de faon approprie, ils peuvent avoir tcontamins par lchantillon ou les rsidus chimiques.


29/10021

SECTION 4 OPERATION

4.1 Apparatus PreparationSee SECTION 3 for more safety information. Prepare to perform thedigestion either behind a laboratory safety shield or inside a fume hood. Ifa 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 cap. Adistinct suction should be felt.

4.2 DigestionProcedures for using the Digesdahl Digestion Apparatus vary with sampletype. 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 the

capillary flow funnel to complete sample decomposition. The capillaryfunnel feeds hydrogen peroxide into the digestion flask at a rate of 3 mLper minute. This allows the analyst to control the amount of time sampleis exposed to the hydrogen peroxide (digestion time) by varying thevolume of hydrogen peroxide used.

DANGER

Wear protective eye glasses and clothing. A strong acid (concentrated sulfuric acid) and

a strong oxidant (50% hydrogen peroxide) are used in the digestion reaction. These

chemicals can cause burns if splashed on the skin or permanent eye damage if allowed

to 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.

DANGER

Porter des lunettes et vtements de protection. Un acide fort (acide sulfurique concentr)

et un oxydant puissant (peroxyde d'hydrogne 50%) sont utiliss dans la raction de

minralisation. Ces produits chimiques peuvent causer des brlures s'ils sont projets sur

la peau ou des blessures irrversibles aux yeux s'ils sont mis au contact des yeux. Si ces

produits sont chauds, les effets sont considrablement plus graves. Immdiatement rincer

toute partie atteinte abondamment l'eau et consulter un mdecin.

Use the Digesdahl Digestion Apparatus only behind a laboratory safety

shield or in a closed fume hood.Some samples are more difficult to digest completely. In a careful studyof 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.


30/10022

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

4.2.1 Appropriate Sample Size

For solid or organic liquid samples, less than 0.5 grams of anhydrous

material can usually be digested effectively. (As a routine practice, 0.25 gof sample is used.) Samples that contain water may be scaled up by aproportional amount. There is no restriction or minimum sample size. Forsamples of aqueous solutions or suspensions, the maximum volume is 40mL. 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 Temperature

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

4.2.3 Sufficient Sulfuric Acid

The amount of concentrated (specific gravity 1.84) sulfuric acid usedmust be sufficient to prevent the digestion from going to dryness. Anyportion of the flask bottom that becomes dry will overheat and may causethe flask to explode. Also, too little acid will cause the sample tooverheat, which may cause thermal decomposition of desired analytes(i.e., ammonium compounds) and result in sample loss. Use an amount ofsulfuric acid that will leave at least 2 mL of residual acid when digestionis complete. Refer to Table 1 for recommended volumes.

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


31/10023

Table 1 Digestion Guidelines of Specific Sample Types

Sample

TypeSample Weight

Vol. of

Acid

PreheatTime

(Step 5)

Vol. of

PeroxideSpecial Instructions

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

weigh samples.

Meat &

Poultry

0.5 g or

predigestion

4 mL or as in

predigest

4 min. 10 mL

Fluid

Fertilizers

0.1 to 0.25 g 4 mL 4 min. 10 mL Add 0.4 g Kjeldahl Reduction

Powder to flask before adding

sulfuric acid. Place the flask in

an 80 C oven 15 minutes before

digestion. Use N-free paper to

weigh 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 to

weigh samples.

Beverage about 5 g

(pipet into funnel

4 mL 1 min. 10 mL Preheat acid for 1 minute then

add sample through funnel. Heat

flask for 30 seconds after sample

is in the flask.

Sludge


32/10024

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 analystmust pay attention to the amount of residual H2SO4 for the type of sampledigested, and adjust the amount of acid or sample accordingly. Never useless 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 Period

A carbonization period prior to the addition of hydrogen peroxideprovides a reducing environment which helps convert organic nitrogen toammonia. In the presence of oxidizable carbon compounds, sulfuric acidreacts to produce sulfur dioxide, which is the active reducing agent.

The reaction is:

H2SO4

H2O + SO2 + O2

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

4.2.5 Adequate Peroxide Concentration for Sufficient Time

Researchers 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 powerful oxidizing agent toward carbonaceousmaterial. The objective is to maintain an adequate concentration of H 2SO5in the hot digestion mixture for a long enough time to complete oxidationof 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 can bedetermined by digesting a sample multiple times with incrementalincreases in the amount of peroxide added (i.e., 5 mL, 10 mL, 15 mL, 20mL). Results of the analysis for the parameter of interest may then begraphed to determine the minimum amount of peroxide needed for

optimum 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 research andactual 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.


33/100


34/10026

Solid Samples

1. 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-toluenesulfonate(185.5 mg/L TKN) is the least difficult to digest. Glycine

p-toluenesulfonate (141.63 mg/L TKN) is moderately difficult to digest,and Nicotinic Acid p-toluenesulfonate (118.58 mg/L TKN) is the mostdifficult to digest.

Liquid Samples

1. 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 digest.Glycine p-toluenesulfonate (84.98 mg/L TKN) is moderately difficultto digest, and Nicotinic Acid p-toluenesulfonate (71.15 mg/L TKN) isthe most difficult to digest.

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

Moisture

Absorptionat 25 % RH

at 50% RH

at 90% RH

0.04%

0.07%

0.14%

0.03%

0.047%

0.15%

0.00%

0.01%

0.08%


35/10027

DIGESTION PROCEDURES


36/10028

DangerReview Section 3 for important safety information before

performing this digestion procedure.

DangerLire au chapitre 3 les informations importantes pour la

scurit avant deffectuer cette technique de digestion.


37/10029

GENERAL DIGESDAHL DIGESTION

1. Transfer apreweighed or apremeasured amount ofsample into a 100-mLDigesdahl digestionflask; see Table 1 onpage 22. The amounttransferred should not

contain 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 Hach

digestion flasks. Volumetric

flasks with concave bottoms

should not be used.

Note: If solids are 10% of

total volume of sample, the

maximum volume of liquid

sample would be 4 mL.

Note: Several 40-mL

sample aliquots of the

sample may be digested in

succession to concentrate

a sample.

Note: If liquid is too

viscous to measure,

preweigh the sample into

the digestion flask.

2. Add concentratedsulfuric acid (accordingto Table 1 on page 22) tothe volumetric flask andat least two siliconcarbide boiling chips forliquid samples.

Note: Pretreat boiling

chips by soaking in 1:1Nitric Acid and rinsing

thoroughly with deionized

water. Treatment is very

important in low-level

work. Hach recommends

silicon carbide boiling

chips.

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 meat

digestion, set to 468 C(875 F).

Note: Wait for the proper

temperature to be reached

before the sample is placed

on 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 acid

will be visible).Note: White acid vapors

usually will be present, but

their presence alone does

not indicate that the boiling

point of sulfuric acid has

been reached.

Note: Liquid samples

require total evaporation of

water before vapors

are visible.

Note: If sample foams up

into the neck of the flask,

lower temperature to

335 C (635 F). Continue

heating at lower

temperature until all water

is evaporated. Then return

to original digestion

temperature.

Note: If foaming or

bumping is not stopped by

lowering temperature orvolume, then liquid samples

that will not clog the

capillary funnel may be

added to the flask via the

capillary funnel, 10 mL at a

time. Decrease amount

added if foaming persists.


38/10030

5. Heat 3-5 minutes.Do not boil sample

to dryness. If sulfuricacid is not present afterheating, do not proceedwith Step 6. Discard thesample if it evaporates todryness. Start over and

use a larger volume ofsulfuric acid in Step 2 ofthis procedure. Or chosea smaller sample amountfor digestion.

Note: Some organic

samples may need more

than five minutes for

complete digestion. See

Table 1 on page 22.

6. Do not proceed ifsulfuric acid is not

visible in the flask. Add10 mL of 50% HydrogenPeroxide to the charredsample via the funnel onthe fractionating head.

Note: Visually confirm the

presence of sulfuric acid inthe flask before adding

hydrogen peroxide.

Note: If the digest does not

turn colorless, add

5 mL increments of

peroxide until the digest

becomes clear.

Note: Use long-neck

glassware or a pipet

to transfer the

hydrogen peroxide.

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

Note: If the sample goes

to dryness, turn off theDigesdahl and air cool to

room temperature. Add

water to flask before

handling. Repeat the

digestion from the Step 1

using 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 to

remove the digestion flask.

Place it on a cooling pad

for at least one minute.Then remove the column.

3-5 minutes

GENERAL DIGESDAHL DIGESTION, continued


39/10031

9. Dilute the digest withapproximately 70 mL ofdeionized water. If notanalyzing for aluminum,nickel or iron, dilute tothe100-mL mark withdeionized water; skip

Step 10 and proceed toStep 11. If analyzing fornickel, aluminum oriron, go to Step 10.

Note: Add deionized

water slowly at first. Cool

the flask if necessary

for handling.

10. Turn thetemperature dial to aheat setting of 204 C(400 F).Add150mLofwater to a 400-mLbeaker. Place the beakeron the heater. Place theflask in the beaker and

boil 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 to

the filtering apparatus.

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

12. Continue theanalysis using one of thefollowing procedures.

Use metals or

TKN procedure



40/10032

Metals Procedure

Note: 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 followingthe specific digestion for liquids, solids or oils to determine the

analysis 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 Solution,swirling between each addition, until the first flash of yellow appears(pH 3). If analyzing for potassium, use 5 N sodium hydroxide instead.

Do 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 readjust

with 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 graduatedmixing cylinder to the same volume with deionized water.

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



41/10033

TKN, Colorimetric Methods

Consult the spectrophotometer or colorimeter procedure to complete theTKN analysis. The following is only a guide to use if a procedure isnot available.

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

2. Add one drop of TKN Indicator.

3. Add one drop of 8 N KOH Standard Solution, swirling between eachaddition, 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 the

cylinder 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 bluecolor appears.

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

7. Continue with the colorimetric procedure.



42/10034


43/10035

SAMPLE TYPE AND SIZE

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

Sample size varies, depending on the sample type and the parameter being

measured. Once the correct sample type is decided, use the tablesfollowing each of the digestion procedures to determine the sample size.

Chart 1

For Aqueous Liquids


44/10036

SAMPLE TYPE AND SIZE, continued

Chart 2

For Oils


45/10037

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

Chart 3

For Solids*

SAMPLE TYPE AND SIZE, continued


46/10038



DangerLire au chapitre 3 les informations importantes pour lascurit avant deffectuer cette technique de digestion.


47/10039

DIGESTION PROCEDURE FOR AQUEOUS LIQUIDS

1. Transfer apremeasured amount ofsample into a 100-mLDigesdahl digestionflask; see Sample andAnalysis Volume Tablesfor Aqueous Liquidsfollowing this

procedure. 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 Hach

Digesdahl flasks.

Volumetric flasks with

concave bottoms should not

be used.

Note: If solids are 10% of

total volume of sample, the

maximum volume of liquid

sample would be 4 mL.

Note: Oils and organicsshould be considered as

solids when determining

sample size.

Note: If liquid is too

viscous to measure,

preweigh the sample into

the 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 1:1

Nitric Acid and rinsing

thoroughly with deionized

water. Treatment is very

important in low-level

work. Hach recommends

using silicon carbide

boiling 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 the

fractionating column.Note: Wait for the proper


before sample is placed on

the heater.

Note: Always operate the

Digesdahl apparatus with

a safety shield in place or

inside a closed fume

hood. Safety glasses

are 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 acid

will be visible).Note: White acid vapors

will usually be present but

their presence alone does

not indicate that the boiling

point of sulfuric acid has

been reached.

Note: Aqueous samples

require total evaporation

of water before vapors

are visible.





heating at a lower

temperature until all water

is evaporated. Then return

to original digestion

temperature.

Note: If foaming or

bumping is not stopped by

lowering temperature orvolume, then liquid samples

that will not clog the

capillary funnel may be

added to the flask via the

capillary funnel, 10 mL at a

time. Decrease amount

added if foaming persists.


48/10040

5. Boil 4 more minutes.Do not boil the sample

to dryness. If sulfuricacid is not present in theflask after the 4 minuteheating, do not proceedwith Step 6! Discardsample if it evaporates to

dryness. 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 not

visible in the flask! Add10 mL of 50% HydrogenPeroxide to the charredsample via the funnel onthe fractionating column.



hydrogen peroxide.


turn colorless, add 5 mL

increments of hydrogen

peroxide until the digest

becomes clear or does not

change color.

Note: If sample foams

during peroxide addition,

remove the Digesdahl

digestion flask and

fractionating column (use

finger cots). Starting with

Step 1, repeat the digestion

adding only 2 mL of

hydrogen peroxide. Then

follow with 8 mL of

hydrogen peroxide.

Note: Do not heat

to dryness.


Note: If the sample goes

to dryness, turn off theDigesdahl and air cool to

room temperature. Add

water to flask before

handling. Repeat the

digestion from the

beginning using a new

sample.

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





Do not add water to the

flask until it has cooled.

4:00

DIGESTION PROCEDURE FOR AQUEOUS LIQUIDS, continued


49/10041

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.

Note: Some methods require pipetting into a volumetric flask or a regular

graduate cylinder.

9. Dilute the digest toapproximately 70 mLwith deionized water.

Note: Add deionized water

slowly at first. Cool the

flask if necessary

for 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 to

Step 12.


boil 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.

c) While applying avacuum to the filteringflask, transfer the sample to

the filtering apparatus.


Continue with theanalysis using theappropriate procedurebelow.



50/10042



4. Add one drop of 8 N Potassium Hydroxide (KOH) Standard Solution,swirling between each addition, until the first flash of yellow appears(pH 3). If analyzing for potassium, use 5 N sodium hydroxide instead.

Do not use a pH meter if analyzing for potassium or silver.


Note: Use pH paper to insure the pH is 3. If it is higher than 4, do not readjust with

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 graduatedmixing cylinder to the same volume with deionized water.

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

TKN, Colorimetric Methods

Consult the spectrophotometer or colorimeter procedure to complete theTKN analysis. The following is only a guide to use if a procedure isnot available.

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

2. Add one drop of TKN Indicator.

3. Add 8 N KOH Standard Solution, one drop at a time, swirling betweeneach addition, 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 bluecolor appears.



51/10043

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

7. Continue with the colorimetric procedure.

Sample and Analysis Volume Tables for Aqueous Liquids

The values in these tables reflect the Hach Spectrophotometer with thenarrowest 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 mL20-800 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=



52/10044

Cadmium, Dithizone (Method 8017)

A = g/L reading from instrument



Chromium, Total (Method 8024)




Expected Cdconc. (g/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 mL0.75-30 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----------------- g/L Total Cd=

A 2500

B C------------------------ mg/L Total Cr=



53/10045

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 mL4-240 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=



54/10046

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 mL1.1-65 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=



55/10047

Lead, Dithizone (Method 8033)

A = g/L reading from instrument



Manganese, PAN (Method 8149)




Expected Pbconc. (g/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 mL0.8-35 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----------------- g/L Total Pb=

A 2500

B C------------------------ mg/L Total Mn=



56/10048

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=



57/10049

Phosphorus, Ascorbic Acid (Method 8048)




Potassium (Method 8049)




Expected PO4conc. (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 mL2-90 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=



58/10050

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 mL3.0-200 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=



59/10051


60/10052



DangerLire au chapitre 3 les informations importantes pour lascurit avant deffectuer cette technique de digestion.


61/10053

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 to

ensure you have a

homogenous sample.

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

Note: Use only Hach

Digesdahl digestion flasks.

Volumetric flasks with

concave bottom should not

be used.Note: Safety glasses and

a safety shield placed

between the operator and

the Digesdahl are required.

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 the

fractionating column.Note: Wait for the proper


before sample is placed on

the heater.

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 acid

is not present in theflask after the boiling

period, do not proceed

to 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





heating at lower

temperature until all

water is evaporated. Then

return to original

digestion temperature.


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5. Do not proceed ifsulfuric acid is not visible

in the flask. Add 10 mLof 50% hydrogenperoxide to the charredsample via the funnel onthe fractionating head.



hydrogen peroxide.


turn colorless, add 5 mL

increments of peroxide until

the digest becomes clear or

does not change color.

Note: If sample foams

during hydrogen peroxide

addition, stop the peroxide

flow and remove the

digestion flask and

fractionating column (use

finger cots). Cool for

30 seconds and return

apparatus to the heating

block. Start peroxide

addition with 2 mL,

then follow with the

remaining peroxide.


Note: If the sample goes to

dryness, turn off theDigesdahl and air cool

completely. Add water

to flask before handling.

Repeat digestion from the

beginning using a new

sample.

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





Do not add water to the

flask until it has cooled.

8. Dilute the digestto approximately 70 mLwith deionized water.

Note: Add demineralized

water slowly at first. Cool

the flask if necessary

for handling.

DIGESTION PROCEDURE FOR OILS, continued


63/10055

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 regular

graduated 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 to

Step 11.


boil for15 minutes. Coolto room temperature anddiluteto the mark withdemineralized water.Invert several timesto mix.

Note: When using a

Digesdahl Digestion

Apparatus system without

temperature control dials,

reset to a lower setting that

gently 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.

c) While applying avacuum to the filtering

flask, transfer the sample tothe filtering apparatus.


12. Continue theanalysis using theappropriate procedurebelow.

DIGESTION PROCEDURE FOR OILS, continued


64/10056


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


Note: Use pH paper to insure the pH is 3. If it is higher than 4, do not readjust with

acid; start over with a fresh aliquot.

6. Conti

digesdahl® digestion apparatus models 23130-20, manual

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