ASTM D3590-2002(2006) Standard Test Methods for Total Kjeldahl Nitrogen in Water《水中氮总数的基耶达尔标准试验方法》.pdf

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1、Designation: D 3590 02 (Reapproved 2006)Standard Test Methods forTotal Kjeldahl Nitrogen in Water1This standard is issued under the fixed designation D 3590; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision

2、. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods cover the determination of totalKjeldahl nitrogen. The following test methods are included:SectionsTest Method

3、 AManual Digestion/Distillation 8 to 14Test Method BSemiautomated Colorimetric Bertholt 15 to 231.2 The analyst should be aware that precision and biasstatements included may not necessarily apply to the waterbeing tested.1.3 This standard does not purport to address all of thesafety concerns, if an

4、y, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 1193 Specifi

5、cation for Reagent WaterD 1426 Test Methods for Ammonia Nitrogen In WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD 3370 Practices for Sampling Water from Closed ConduitsD 5810 Guide for Spiking into Aqueous SamplesD 5847 Practice for

6、 Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3. Terminology3.1 DefinitionsFor definitions of terms used in these testmethods, refer to Terminology D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 total Kjeldahl nitrogenthe sum of the nitrogenconta

7、ined in the free ammonia and other nitrogen compoundswhich 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 Nitro

8、gen compounds are widely distributed in the envi-ronment. Sources of nitrogen include surface-applied fertiliz-ers, cleaning products, and drinking water treatment aids.Because nitrogen is a nutrient for photosynthetic organisms, itmay be important to monitor and control discharge into theenvironmen

9、t.5. Interferences5.1 Nitrate is known to cause a serious negative interferencein the test. Reportedly, a concentration of 250 mg/L NO3results in zero recovery of some level of N added as some Ncompound.5.2 The analyst is cautioned that ammonia in the laboratorymay easily become an interference in t

10、hese test methods fromcontamination of reagents, 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.6. Purity of Reagents6.1 Reagent-grade chemicals shall be used in all tests.Unless other

11、wise indicated, it is intended that all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society, where suchspecifications are available.3Other grades may be used,provided it is first ascertained that the reagent is of sufficienthigh purity

12、to permit its use without lessening the accuracy ofthe determination.6.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Specification D 1193, Type I. Other reagent water types maybe used provided it is first ascertained that the wa

13、ter is ofsufficiently high purity to permit its use without adversely1These test methods are under the jurisdiction of ASTM Committee D19 onWater and are the direct responsibility of Subcommittee D19.05 on InorganicConstituents in Water.Current edition approved Dec. 15, 2006. Published February 2007

14、. Originallyapproved in 1977. Last previous edition approved in 2002 as D 3590 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary pag

15、e onthe ASTM website.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the Uni

16、ted States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.affecting the

17、precision and bias of the test method. Type IIIwater was specified at the time of round-robin testing of thistest method7. Sampling and Preservation7.1 Collect the sample in accordance with applicable Prac-tices D 3370.7.2 Samples may be preserved up to 28 days by addingconcentrated sulfuric acid to

18、 adjust to pH 2 or less and storingat 4C. The preserved sample should be analyzed as soon aspossible; data on decomposition are not available.TEST METHOD AMANUAL DIGESTION/DISTILLATION8. Scope8.1 This test method covers the determination of totalKjeldahl nitrogen in water. It measures free ammonia o

19、rammonia formed from the conversion of nitrogen componentsof biological origin such as amino acids and proteins. How-ever, the procedure may not convert the nitrogenous com-pounds of some wastes to ammonia. Examples of such com-pounds that may not be measured are nitro compounds,hydrozones, oximes,

20、nitrates, semicarbazones, pyridines, andsome refractory tertiary amines.8.2 Three alternatives are described for the final determina-tion of the ammonia: a titrimetric method, which is applicableto concentrations above 1 mg N/L; a Nesslerization method,which is applicable to concentrations below 1 m

21、g N/L; and apotentiometric method which is applicable to the range from0.04 to 1000 mg N/L.8.3 This test 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 prese

22、nce of concentratedH2SO4,K2SO4, and HgSO4, and is digested until SO3fumesare obtained and the solution becomes 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 Kjel

23、dahl nitrogen is determinedby colorimetry, titrimetry, or potentiometry.10. Apparatus10.1 Digestion ApparatusA Kjeldahl digestion apparatuswith 800 to 100-mL flasks and suction takeoff to remove SO3fumes and water.10.2 Distillation Apparatus4A macro Kjeldahl flask con-nected to a condenser and an ad

24、aptor so that the distillate canbe collected.10.3 Spectrophotometer or Colorimeter, for use at 425 nmwith a spectral band path of not more than 6 20 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 Electro

25、de.510.6 Magnet Stirrer, thermally insulated.11. Reagents and Materials11.1 Ammonia Solution Stock, (1.0 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 nit

26、rogen)Dilute 10.0 mL of the stock solution (see11.1) with water to 1 L in a volumetric flask.11.3 Boric 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 SolutionDissolve8gofredmer-curic oxide (HgO) in a mixture of

27、10 mL of sulfuric acid(H2SO4, sp gr 1.84) and 40 mL of water, and dilute solution to100 mL.NOTE 1Mercury is a toxic metal and requires special diposal require-ments. See Occupational Health and Safety Act (OSHA) regulations forspecific instructions on handling and disposal of mercury compounds.Alter

28、nate catalysts may be used but it is the users responsibility todetermine the validity of other catalysts.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 (

29、1 g/L)Dissolve0.4 g of dimethyl-aminoazobenzene-o-carboxylic acid, sodiumsalt, in approximately 300 mL of water. To this solution add0.55 g of a water-soluble blue dyestuff, Color Index No. 714,6dissolve, and dilute to 1 L with water. This indicator isavailable commercially in a prepared form.711.7

30、Nessler ReagentDissolve 100 g of mercuric iodide(HgI2) 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 ye

31、ar if stored in a thick amber polyethylene bottle outof direct sunlight.NOTE 2Mercury is a toxic metal and requires special diposal require-ments. See Occupational Health and Safety Act (OSHA) regulations forspecific instructions on handling and disposal of mercury compounds.Alternate reagents may b

32、e used but it is the users responsibility todetermine the validity of other reagents.11.8 Phenolphthalein Indicator SolutionDissolve5gofphenolphthalein in 500 mL of 95 % ethyl alcohol or isopro-panol and add 500 mL of water. Add NaOH (0.8 g/L) solutiondropwise until a faint pink color appears.4Micro

33、 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 found satisfactoryfor th

34、is purpose.6Refers to compounds, bearing such number, as described in “Color Index,”Society of Dyers and Colourists, Yorkshire, England (1924). American CyanamidCompanys “Calcocid Blux AX Double” has been found satisfactory for thispurpose.7TM Fleisher Methyl Purple indicator, U. S. Patent No. 24169

35、9, is availablefrom Fleisher Chemical Co., P. O. Box 616, Ben Franklin Station, Washington, DC20004, or from any chemical supply company handling Fleisher Methyl Purple.D 3590 02 (2006)211.9 Sodium Hydroxide Solution (400 g/L)Dissolve 400 gof NaOH in 800 mLof water, cool, and dilute to 1 Lwith water

36、.11.10 Sodium Hydroxide Solution (0.8 g/L)Dilute 2 mLofNaOH 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 Sulfuric Acid Solution, Standard (0.02 N, 1 mL = 0.28mg ammonia

37、 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 against 0.0200 N Na2CO3solution. This last solutionis prepared by d

38、issolving 1.060 g of anhydrous Na2CO3, ovendried at 140C, and diluting to 1 L with water.11.13 Digestion SolutionDissolve 267 g of K2SO4in1300 mL water and 400 mL of concentrated H2SO4. Add 50mL of mercuric sulfate solution (see 11.4) and dilute to 2 Lwith water. A digestion packet8may be used in pl

39、ace of thedigestion solution 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 distillate is ammonia-free. Repeat this operation each time the app

40、aratus 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 table:Kjeldahl Nitrogen in Sample,mg/L Sample Size, mL0to5 500

41、5to10 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 3) and digest the mixture in the Kjeldahl apparatus untilSO3fumes are given off and the solution turns colorless or paleyellow. Continue heating for an ad

42、ditional 30 min. Cool theresidue and add 300 mL of water. Mix well.NOTE 3Digesting the sample with a packet8and 20 mL of concen-trated H2SO4is acceptable. Cut the end of the package and empty thecontents into the digestion flask.12.2.3 Alkalize the digestate by careful addition of 100 mLof sodium hy

43、droxide-thiosulfate solution (see 11.11). Do notmix until the digestion flask has been connected to thedistillation apparatus (see 12.2.4).NOTE 4Slow addition of the heavy caustic solution down the tiltedneck of the digestion flask will cause the heavier solution to underlay theaqueous H2SO4without

44、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. Distill 300 mL at therate of 6 to 10 mL/min.12.2.5 Transfer

45、 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. Use the remaining 250 mL for this determi-nation.12.3 Mic

46、ro 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 given off and thesolution turns colorless or pale yellow

47、. 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 4).12.3.3 Connect the

48、 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 flask. Distill 30 mL at the rateof 6 to 10 mL/min.12.3.4 Transfer to a 50-mL volumetric flask, dilute tovolume wi

49、th water, and mix. Pipet 25 mL to an Erlenmeyerflask and titrate with H2SO4(see 12.4.1). If the concentrationis found to be below 1 mg/L determine the value colorimetri-cally. Use 20 mL of the remaining solution for this determina-tion.12.4 Determination of Ammonia DistillateDetermine theammonia content of the distillate titrimetrically, colorimetri-cally, or potentiometrically.12.4.1 Titrimetric DeterminationAdd 3 drops of themixed indicator (see 11.5) to the distillate and titrate theammonia with 0.02 N H2SO4(see 11.12), matching the endpoint agains