ASTM D3590-2011 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:D359002 (Reapproved 2006) Designation: D3590 11Standard 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 yea

2、r of last revision. A number in parentheses 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 total Kjeldahl nitrogen. The following test methods are included:S

3、ectionsTest Method AManual Digestion/Distillation 8 to 14Test Method BSemiautomated Colorimetric Bertholt 15 to 231.2 The analyst should be aware that precision and bias statements included may not necessarily apply to the water being tested.1.31.3 The values stated in SI units are to be regarded as

4、 standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine th

5、e applicability of regulatorylimitations prior to use.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 Bias of Applicable Test Methods o

6、f Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis3. Terminology3.1 DefinitionsFor definitions of terms used in these test me

7、thods, refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 total Kjeldahl nitrogen, nthe sum of the nitrogen contained in the free ammonia and other nitrogen compounds, whichare converted to ammonium sulfate (NH4)2SO4 under the specified digestion conditions.4. Signif

8、icance and Use4.1 These test methods are useful for measuring organic nitrogen and ammoniacal nitrogen, which are essential growthnutrients.4.2 Nitrogen compounds are widely distributed in the environment. Sources of nitrogen include surface-applied fertilizers,cleaning products, and drinking water

9、treatment aids. Because nitrogen is a nutrient for photosynthetic organisms, it may beimportant to monitor and control discharge into the environment.5. Interferences5.1 Nitrate is known to cause a serious negative interference in the test. Reportedly, a concentration of 250 mg/L NO3resultsin zero r

10、ecovery of some level of N added as some N compound.1These test methods are under the jurisdiction of ASTM Committee D19 on Water and are the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Dec. 15, 2006. Published February 2007. Originally app

11、roved in 1977. Last previous edition approved in 2002 as D359002. DOI:10.1520/D3590-02R06.Current edition approved April 1, 2011. Published April 2011. Originally approved in 1977. Last previous edition approved in 2006 as D3590 02(2006). DOI:10.1520/D3590-11.2For referenced ASTM standards, visit th

12、e ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard

13、 an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is

14、 to be considered the official document.*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.5.2 The analyst is cautioned that ammonia in the laboratory may easily become an

15、 interference in these test methods fromcontamination of reagents, caps, or from the laboratory atmosphere. Care should be taken that ammonium hydroxide, either as areagent or as a cleaning substance, is not used in the same room.6. Purity of Reagents6.1 Reagent-grade chemicals shall be used in all

16、tests. Unless otherwise indicated, it is intended that all reagents shall conformto the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications areavailable.3Other grades may be used, provided it is first ascertained that the reagent is of s

17、ufficient high purity to permit its usewithout lessening the accuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, reference to water shall be understood to mean reagent water conforming toSpecification D1193, Type I. Other reagent water types may be used provided it is first

18、ascertained that the water is of sufficientlyhigh purity to permit its use without adversely affecting the precision and bias of the test method. Type III water was specified atthe time of round-robin testing of this test method7. Sampling and Preservation7.1 Collect the sample in accordance with ap

19、plicable Practices D3370.7.2 Samples may be preserved up to 28 days by adding concentrated sulfuric acid to adjust to pH 2 or less and storing at 4C.2 6C. The preserved sample should be analyzed as soon as possible; data on decomposition are not available.TEST METHOD AMANUAL DIGESTION/DISTILLATION8.

20、 Scope8.1 This test method covers the determination of total Kjeldahl nitrogen in water. It measures free ammonia or ammonia formedfrom the conversion of nitrogen components of biological origin such as amino acids and proteins. However, the procedure maynot convert the nitrogenous compounds of some

21、 wastes to ammonia. Examples of such compounds that may not be measured arenitro compounds, hydrozones, oximes, nitrates, semicarbazones, pyridines, and some refractory tertiary amines.8.2 Three alternatives are described for the final determination of the ammonia: a titrimetric method, which is app

22、licable toconcentrations above 1 mg N/L; a Nesslerization method, which is applicable to concentrations below 1 mg N/L; and apotentiometric method which is applicable to the range from 0.04 to 1000 mg N/L.8.3 This test method is described for micro and macro systems. Micro determination can be made

23、on sample aliquots containingup to 10 mg of nitrogen.9. Summary of Test Method9.1 The sample is heated in the presence of concentrated H2SO4,K2SO4, and HgSO4, and is digested until SO3fumes areobtained and the solution becomes colorless or pale yellow. The residue is cooled, diluted, and is treated

24、and alkalized with ahydroxide-thiosulfate solution. The ammonia is distilled into a boric acid solution and total Kjeldahl nitrogen is determined bycolorimetry, titrimetry, or potentiometry.10. Apparatus10.1 Digestion ApparatusAKjeldahl digestion apparatus with 800 to 100-mL flasks and suction takeo

25、ff to remove SO3fumesand water.10.2 Distillation Apparatus4A macro Kjeldahl flask connected to a condenser and an adaptor so that the distillate can becollected.10.3 Spectrophotometer or Colorimeter, for use at 425 nm with a spectral band path of not more than 6 20 nm and a light pathof 1 cm or long

26、er.10.4 Electrometer (pH Meter), with expanded millivolt scale, 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 mL = 1.0 mg ammonia nitrogen)Dissolve 3.819 g of ammonium chloride (NH4Cl) in

27、water and dilute to 1 L in a volumetric flask with water.3Reagent Chemicals, American Chemical Society Specifications , American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH

28、 Ltd., Poole, Dorset, U.K., and the , American Chemical Society, Washington, DC.For suggestions on the testing of reagents not listed by the American Chemical Society, and the United States Pharmacopeia and National Formulary, U.S. PharmaceuticalConvention, Inc. (USPC), Rockville, MD.4Micro Kjeldahl

29、 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 found satisfactoryfor this purpose. Also, Orion Model 95-12 has been found satisfactory for this purp

30、ose.D3590 11211.2 Ammonia Solution, Standard (1.0 mL = 0.01 mg ammonia nitrogen)Dilute 10.0 mLof the stock solution (see 11.1) withwater 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 volumetric flask.11.4 Mer

31、curic Sulfate SolutionDissolve8gofredmercuric oxide (HgO) in a mixture of 10 mL of sulfuric acid (H2SO4,spgr 1.84) and 40 mL of water, and dilute solution to 100 mL.NOTE 1Mercury is a toxic metal and requires special diposal requirements. See Occupational Health and Safety Act (OSHA) regulations for

32、 specificinstructions on handling and disposal of mercury compounds. Alternate catalysts may be used but it is the users responsibility to determine the validityof other catalysts.11.5 Mixed Indicator SolutionMix 2 volumes of 0.2 % methyl red in 95 % ethanol with 1 volume of 0.2 % methylene bluein e

33、thanol. Prepare fresh every 30 days.11.6 Methyl Purple Indicator Solution (1 g/L)Dissolve 0.4 g of dimethyl-aminoazobenzene-o-carboxylic acid, sodium salt,in approximately 300 mL of water. To this solution add 0.55 g of a water-soluble blue dyestuff, Color Index No. 714,6dissolve,and dilute to 1 L w

34、ith water. This indicator is available commercially in a prepared form.711.7 Nessler ReagentDissolve 100 g of mercuric iodide (HgI2) and 70 g of potassium iodide (KI) in a small volume of water.Add this mixture slowly, with stirring, to a cooled solution of 160 g of sodium hydroxide (NaOH) in 500 mL

35、 of water. Dilute themixture to 1 L. This solution is stable for at least one year if stored in a thick amber polyethylene bottle out of direct sunlight.NOTE 2Mercury is a toxic metal and requires special diposal requirements. See Occupational Health and Safety Act (OSHA) regulations for specificins

36、tructions on handling and disposal of mercury compounds. Alternate reagents may be used but it is the users responsibility to determine the validityof other reagents.11.8 Phenolphthalein Indicator SolutionDissolve5gofphenolphthalein in 500 mL of 95 % ethyl alcohol or isopropanol andadd 500 mL of wat

37、er. Add NaOH (0.8 g/L) solution dropwise until a faint pink color appears.11.9 Sodium Hydroxide Solution (400 g/L)Dissolve 400 g of NaOH in 800 mL of water, cool, and dilute to 1 L with water.11.10 Sodium Hydroxide Solution (0.8 g/L)Dilute 2 mL of NaOH solution (400 g/L) (see 11.9) with water to 1 L

38、.11.11 Sodium Hydroxide-Sodium Thiosulfate SolutionDissolve 500 g of NaOH and 25 g of Na2S2O35H2O in water and diluteto1L.11.12 Sulfuric Acid Solution, Standard (0.02 N, 1 mL = 0.28 mg ammonia nitrogen)Prepare a stock solution of approximately0.1 N acid by diluting 3 mL of concentrated H2SO4(sp gr 1

39、.84) to 1 L with water. Dilute 200 mL of this solution to 1 L with water.Standardize the approximately 0.02 N H2SO4solution against 0.0200 N Na2CO3solution. This last solution is prepared bydissolving 1.060 g of anhydrous Na2CO3, oven dried at 140C, and diluting to 1 L with water.11.13 Digestion Sol

40、utionDissolve 267 g of K2SO4in 1300 mL water and 400 mL of concentrated H2SO4. Add 50 mL ofmercuric sulfate solution (see 11.4) and dilute to 2 L with water.Adigestion packet8may be used in place of the digestion solutionin the macro Kjeldahl system.12. Procedure12.1 Clean the distillation apparatus

41、 with steam before use by 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 apparatus is out of servicelong enough to accumulate ammonia (usually4hormore).12.2 Macro Kjeldahl System:12.2

42、.1 Place a measured sample into an 800-mL Kjeldahl flask and dilute to 500 mL. The sample size can be determined usingthe following table:Kjeldahl Nitrogen in Sample,mg/L Sample 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

43、digestion solution (see 11.13) (see Note 3) and digest the mixture in the Kjeldahl apparatus until SO3fumes are given off and the solution turns colorless or pale yellow. Continue heating for an additional 30 min. Cool the residueand add 300 mL of water. Mix well.NOTE 3Digesting the sample with a pa

44、cket8and 20 mL of concentrated H2SO4is acceptable. Cut the end of the package and empty the contentsinto the digestion flask.6Refers to compounds, bearing such number, as described in “Color Index,” Society of Dyers and Colourists, Yorkshire, England (1924). American Cyanamid Companys“Calcocid Blux

45、AX Double” has been found satisfactory for this purpose.7TM Fleisher Methyl Purple indicator, U. S. Patent No. 241699, is available from Fleisher Chemical Co., P. O. Box 616, Ben Franklin Station, Washington, DC 20004,or from any chemical supply company handling Fleisher Methyl Purple.8Digestion pac

46、ket, Kel Pak No. 5, available from the Curtin-Matheson Scientific Co., has been found satisfactory for this purpose.D3590 11312.2.3 Alkalize the digestate by careful addition of 100 mL of sodium hydroxide-thiosulfate solution (see 11.11). Do not mixuntil the digestion flask has been connected to the

47、 distillation apparatus (see 12.2.4).NOTE 4Slow addition of the heavy caustic solution down the tilted neck of the digestion flask will cause the heavier solution to underlay the aqueousH2SO4without loss of free ammonia.12.2.4 Connect the Kjeldahl flask to the condenser with the tip of the condenser

48、 (or an extension of the condenser tip) belowthe level of 50 mL of 2 % boric acid solution (see 11.3) contained in a 500-mL Erlenmeyer flask. Distill 300 mL at the rate of 6to 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

49、 to anErlenmeyer flask and titrate with H2SO4(see 12.4.1). If the concentration is found to be below 1 mg/L, determine the valuecolorimetrically. Use the remaining 250 mL for this determination.12.3 Micro Kjeldahl System:12.3.1 Place 50.0 mL of sample or an aliquot in a 100-mL Kjeldahl flask and add 10 mL of digestion solution (see 11.13). Atthe same time start a reagent blank. Evaporate the mixture in the Kjeldahl apparatus until SO3fumes are given off and the solutionturns colorless or pale yellow. Digest for an additional 30 min. Cool the resi