ASTM D3590-17 Standard Test Methods for Total Kjeldahl Nitrogen in Water.pdf

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1、Designation: D3590 17Standard Test Methods forTotal Kjeldahl Nitrogen in Water1This standard is issued under the fixed designation D3590; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parent

2、heses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods cover the determination of totalKjeldahl nitrogen. Section 24 on Quality Control pertains tothese test methods. The following test

3、methods are included:SectionsTest Method AManual Digestion/Distillation 814Test Method BSemiautomated Colorimetric Bertholt 15231.2 The analyst should be aware that precision and biasstatements included may not necessarily apply to the waterbeing tested.1.3 The values stated in SI units are to be re

4、garded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and deter

5、mine the applica-bility of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendati

6、ons issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD1426 Test Methods for Ammonia Nitrogen In WaterD2777 Practice for Determination of Precision and B

7、ias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3. Terminology3.1 Definitions:3.1.1 For defin

8、itions of terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 continuing calibration blank, na solution containingno analytes (of interest) which is used to verify blank responseand freedom from carryover.3.2.2 continuing calibration verifi

9、cation, na solution (orset of solutions) of known concentration used to verify freedomfrom excessive instrumental drift; the concentration is to coverthe range of calibration curve.3.2.3 total Kjeldahl nitrogen, nthe sum of the nitrogencontained in the free ammonia and other nitrogen compounds,which

10、 are converted to ammonium sulfate (NH4)2SO4 underthe specified digestion conditions.4. Significance and Use4.1 These test methods are useful for measuring organicnitrogen and ammoniacal nitrogen, which are essential growthnutrients.4.2 Nitrogen compounds are widely distributed in the envi-ronment.

11、Sources of nitrogen include surface-appliedfertilizers, cleaning products, and drinking water treatmentaids. Because nitrogen is a nutrient for photosyntheticorganisms, it may be important to monitor and control dis-charge into the environment.5. Interferences5.1 Nitrate is known to cause a serious

12、negative interferencein the test. Reportedly, a concentration of 250 mg/L NO3results in zero recovery of some level of mg/LN added as somenitrogen compound.5.2 The analyst is cautioned that ammonia in the laboratorymay easily become an interference in these test methods fromcontamination of reagents

13、, caps, or from the laboratory atmo-sphere. Care should be taken that ammonium hydroxide, eitheras a reagent or as a cleaning substance, is not used in the sameroom.1These test methods are under the jurisdiction of ASTM Committee D19 onWater and are the direct responsibility of Subcommittee D19.05 o

14、n InorganicConstituents in Water.Current edition approved June 1, 2017. Published June 2017. Originallyapproved in 1977. Last previous edition approved in 2011 as D3590 11. DOI:10.1520/D3590-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at s

15、erviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Un

16、ited StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barrie

17、rs to Trade (TBT) Committee.16. Purity of Reagents6.1 Reagent-grade chemicals shall be used in all tests.Unless otherwise indicated, it is intended that all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society, where suchspecifications a

18、re available.3Other grades may be used, pro-vided it is first ascertained that the reagent is of sufficient highpurity to permit its use without lessening the accuracy of thedetermination.6.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water confo

19、rmingto Specification D1193, Type I. Other reagent water types maybe used provided it is first ascertained that the water is ofsufficiently high purity to permit its use without adverselyaffecting the precision and bias of the test method. Type IIIwater was specified at the time of round-robin testi

20、ng of thistest method.7. Sampling and Preservation7.1 Collect the sample in accordance with applicable Prac-tices D3370.7.2 Samples may be preserved up to 28 days by addingconcentrated sulfuric acid to adjust to pH 2 or less and storebetween 2 and 6C. The preserved sample should be analyzedas soon a

21、s possible; data on decomposition are not available.TEST METHOD AMANUAL DIGESTION/DISTILLATION8.1 This test method covers the determination of totalKjeldahl nitrogen in water. It measures free ammonia orammonia formed from the conversion of nitrogen componentsof biological origin such as amino acids

22、 and proteins.However, the procedure may not convert the nitrogenouscompounds of some wastes to ammonia. Examples of suchcompounds that may not be measured are nitro compounds,hydrozones, oximes, nitrates, semicarbazones, pyridines, andsome refractory tertiary amines.8.2 Three alternatives are descr

23、ibed for the final determina-tion of the ammonia: a titrimetric method, which is applicableto concentrations above 1 mg/L N; a Nesslerization method,which is applicable to concentrations below 1 mg/L N; and apotentiometric method which is applicable to the range from0.04 to 1000 mg/L N.8.3 This test

24、 method is described for micro and macrosystems. Micro determination can be made on sample aliquotscontaining up to 10 mg of nitrogen.9. Summary of Test Method9.1 The sample is heated in the presence of concentratedH2SO4,K2SO4, and HgSO4, and is digested until SO3fumesare obtained and the solution b

25、ecomes colorless or pale yellow.The residue is cooled, diluted, and is treated and alkalized witha hydroxide-thiosulfate solution. The ammonia is distilled intoa boric acid solution and total Kjeldahl nitrogen is determinedby colorimetry, titrimetry, or potentiometry.10. Apparatus10.1 Digestion Appa

26、ratusA Kjeldahl digestion apparatuswith 800 to 1000-mL flasks and suction takeoff to remove SO3fumes and water.10.2 Distillation Apparatus4A macro Kjeldahl flask con-nected to a condenser and an adaptor so that the distillate canbe collected.10.3 Spectrophotometer or Colorimeter, for use at 425 nmwi

27、th a spectral band path of not more than 620 nm and a lightpath of 1 cm or longer.10.4 Electrometer (pH Meter), with expanded millivoltscale, or a specific ion meter.10.5 Ammonia Selective Electrode.510.6 Magnet Stirrer, thermally insulated.11. Reagents and Materials11.1 Ammonia Solution Stock, (1.0

28、 mL = 1.0 mg ammonianitrogen)Dissolve 3.819 g of ammonium chloride (NH4Cl)in water and dilute to 1 L in a volumetric flask with water.11.2 Ammonia Solution, Standard (1.0 mL = 0.01 mg am-monia nitrogen)Dilute 10.0 mL of the stock solution (see11.1) with water to 1 L in a volumetric flask.11.3 Boric

29、Acid Solution (2 %)Dissolve 20 g of boric acid(H3BO3) in water and dilute to 1 L with water in a volumetricflask.11.4 Mercuric Sulfate SolutionDissolve8gofredmercu-ric oxide (HgO) in a mixture of 10 mL of sulfuric acid (H2SO4,sp gr 1.84) and 40 mL of water, and dilute solution to 100 mL.(WarningMerc

30、ury has been designated by many regulatoryagencies as a hazardous material that can cause serious medicalissues. Mercury, or its vapor, has been demonstrated to behazardous to health and corrosive to materials. Caution shouldbe taken when handling mercury and mercury containingproducts. See the appl

31、icable product Safety Data Sheet (SDS)for additional information. Users should be aware that sellingmercury and/or mercury containing products into your state orcountry may be prohibited by law.)NOTE 1Alternate catalysts such as copper sulfate (CuSO4) may beused but it is the users responsibility to

32、 determine the validity of othercatalysts.11.5 Mixed Indicator SolutionMix 2 volumes of 0.2 %methyl red in 95 % ethanol with 1 volume of 0.2 % methyleneblue in ethanol. Prepare fresh every 30 days.11.6 Methyl Purple Indicator Solution (1 g/L)Dissolve0.4 g of dimethyl-aminoazobenzene-o-carboxylic aci

33、d, sodium3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, and the United States Pharmacopeia andNational Formulary, U.S. Pharmaceutical Convention, Inc. (USPC

34、), Rockville,MD.4Micro Kjeldahl steam distillation apparatus is commercially available.5EIL Model 8002-2 of Electronics Instruments Ltd. (U. S. Representative:Cambridge Instrument Co., 73 Spring St., Ossining, NY 10562) has been foundsatisfactory for this purpose. Also, Orion Model 95-12 has been fo

35、und satisfactoryfor this purpose.D3590 172salt, in approximately 300 mL of water. To this solution add0.55 g of a water-soluble blue dyestuff, dissolve, and dilute to1 L with water. This indicator is available commercially in aprepared form.11.7 Nessler ReagentDissolve 100 g of mercuric iodide(HgI2)

36、 and 70 g of potassium iodide (KI) in a small volume ofwater. Add this mixture slowly, with stirring, to a cooledsolution of 160 g of sodium hydroxide (NaOH) in 500 mL ofwater. Dilute the mixture to 1 L. This solution is stable for atleast one year if stored in a thick amber polyethylene bottle outo

37、f direct sunlight. (WarningSee 11.4.)11.8 Phenolphthalein Indicator SolutionDissolve5gofphenolphthalein in 500 mL of 95 % ethyl alcohol or isopropa-nol and add 500 mL of water. Add NaOH (0.8 g/L) solutiondropwise until a faint pink color appears.11.9 Sodium Hydroxide Solution (400 g/L)Dissolve 400 g

38、of NaOH in 800 mLof water, cool, and dilute to 1 Lwith water.11.10 Sodium Hydroxide Solution (0.8 g/L)Dilute 2 mL ofNaOH solution (400 g/L) (see 11.9) with water to 1 L.11.11 Sodium Hydroxide-Sodium Thiosulfate SolutionDissolve 500 g of NaOH and 25 g of Na2S2O35H2O in waterand dilute to 1 L.11.12 Su

39、lfuric Acid Solution, Standard (0.02 N, 1 mL = 0.28mg ammonia nitrogen)Prepare a stock solution of approxi-mately 0.1 N acid by diluting 3 mL of concentrated H2SO4(spgr 1.84) to 1 L with water. Dilute 200 mL of this solution to 1L with water. Standardize the approximately 0.02 N H2SO4solution agains

40、t 0.0200 N Na2CO3solution. This last solutionis prepared by dissolving 1.060 g of anhydrous Na2CO3, ovendried at 140C, and diluting to 1 L with water.11.13 Digestion SolutionDissolve 267 g of K2SO4in 1300mL water and 400 mL of concentrated H2SO4. Add 50 mL ofmercuric sulfate solution (see 11.4) and

41、dilute to 2 L withwater. A digestion packet may be used in place of the digestionsolution in the macro Kjeldahl system.12. Procedure12.1 Clean the distillation apparatus with steam before useby distilling a 1 + 1 mixture of water and sodium hydroxide-thiosulfate solution (see 11.11) until the distil

42、late is ammonia-free. Repeat this operation each time the apparatus is out ofservice long enough to accumulate ammonia (usually4hormore).12.2 Macro Kjeldahl System:12.2.1 Place a measured sample into an 800-mL Kjeldahlflask and dilute to 500 mL. The sample size can be determinedusing the following t

43、able:Kjeldahl Nitrogen in Sample,mg/LSample Size,mL0to5 5005to10 25010 to 20 10020 to 50 50.050 to 500 25.0Prepare a 500-mL reagent water blank.12.2.2 Add 100 mL of digestion solution (see 11.13) (seeNote 2) and digest the mixture in the Kjeldahl apparatus untilSO3fumes are given off and the solutio

44、n turns colorless or paleyellow. Continue heating for an additional 30 min. Cool theresidue and add 300 mL of water. Mix well.NOTE 2Digesting the sample with a packet and 20 mLof concentratedH2SO4is acceptable. Cut the end of the package and empty the contentsinto the digestion flask.12.2.3 Alkalize

45、 the digestate by careful addition of 100 mLof sodium hydroxide-thiosulfate solution (see 11.11). Do notmix until the digestion flask has been connected to thedistillation apparatus (see 12.2.4).NOTE 3Slow addition of the heavy caustic solution down the tiltedneck of the digestion flask will cause t

46、he heavier solution to underlay theaqueous H2SO4without loss of free ammonia.12.2.4 Connect the Kjeldahl flask to the condenser with thetip of the condenser (or an extension of the condenser tip)below the level of 50 mL of 2 % boric acid solution (see 11.3)contained in a 500-mL Erlenmeyer flask. Dis

47、till 300 mL at therate of 6 to 10 mL/min.12.2.5 Transfer the distillate to a 500-mL volumetric flask,dilute to volume with water, and mix. Transfer 250 mL to anErlenmeyer flask and titrate with H2SO4(see 12.4.1). If theconcentration is found to be below 1 mg/L, determine the valuecolorimetrically. U

48、se the remaining 250 mL for this determi-nation.12.3 Micro Kjeldahl System:12.3.1 Place 50.0 mL of sample or an aliquot in a 100-mLKjeldahl flask and add 10 mL of digestion solution (see 11.13).At the same time start a reagent blank. Evaporate the mixturein the Kjeldahl apparatus until SO3fumes are

49、given off and thesolution turns colorless or pale yellow. Digest for an additional30 min. Cool the residue and add 30 mL of water.12.3.2 Alkalize the digestate by careful addition of 10 mLofsodium hydroxide-thiosulfate solution (see 11.11). Do not mixuntil the digestion flask has been connected to the distillationapparatus (see Note 3).12.3.3 Connect the Kjeldahl flask to the condenser with thetip of the condenser (or an extension of the condenser tip)below the level of 5 mL of 2 % H3BO3solution (see 11.3)contained in a small Erlenmeyer fl