ASTM D8001-2016 3904 Standard Test Method for Determination of Total Nitrogen Total Kjeldahl Nitrogen by Calculation and Total Phosphorus in Water Wastewater by Ion Chromatography《.pdf

1、Designation: D8001 16Standard Test Method forDetermination of Total Nitrogen, Total Kjeldahl Nitrogen byCalculation, and Total Phosphorus in Water, Wastewater byIon Chromatography1This standard is issued under the fixed designation D8001; the number immediately following the designation indicates th

2、e year oforiginal adoption or, in the case of revision, the year 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. Scope1.1 This test method is applicable for the analysis to

3、talnitrogen (organic nitrogen + ammonia-N + nitrate-N +nitrite-N) as nitrate and total phosphorus as orthophosphate inunfiltered water samples by alkaline persulfate digestion fol-lowed by ion chromatography (IC).1.2 Total Kjeldahl nitrogen (TKN) is determined by thecalculation. To determine TKN sub

4、tract the nitrate-N andnitrite-N in a digested sample from a non-digested sample (seeSection 4, Summary of Test Method).1.3 The limit of detection (LOD), limit of quantitation(LOQ), and reporting range in Table 1 are based on thetwo-step process for this test method: digestion and analyticalstep. Be

5、cause the digestion step requires a sample dilution, theLOD and LOQ are higher than undigested samples. Thereporting range, LOD, and LOQ can be modified and perhapsimproved depending on several factors (see Section 6, Inter-ferences).1.4 The method detection limits (MDL) are shown forreference. The

6、digestion reagent contains background nitrateand results in higher detection limits. MDL will be shown afterthe interlaboratory study (ILS) is completed.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does

7、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 determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standa

8、rds:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3856 Guide for Management Systems in LaboratoriesEngaged in Analysis of WaterD4327 Test Method for Anions in Water b

9、y Suppressed IonChromatographyD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisD5810 Guide for Spiking into Aqueous SamplesD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement Sy

10、stem PerformanceD6792 Practice for Quality System in Petroleum Productsand Lubricants Testing Laboratories3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 total Kjeldahl nitrogen (TK

11、N), nthe sum of organicnitrogen plus ammonia (NH3).3.2.2 total nitrogen (TN), nthe sum of all nitrate, nitrite,ammonia, and organic nitrogen, as N, in water or wastewatersamples.3.2.3 total phosphorus (TP), nthe sum oforthophosphates, polyphosphates, and organically boundphosphates, as P, in water o

12、r wastewater samples.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved July 15, 2016. Published August 2016. DOI: 10.1520/D8001-16.2For refer

13、enced 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 page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West

14、Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 A water sample is digested with alkaline persulfate at a2:1 ratio, the initial pH is 12. This sample is heated at 120Cfor 60 min. Initial alkaline conditions oxidize dissolved/suspended nitrogen to nitrate. Over time the solutio

15、n becomesacidic according to the following calculation:S2O8221H2O2HSO42112O2(1)The acidic conditions (pH 2) result in the hydrolysis ofdissolved/suspended phosphorus to orthophosphate.4.2 The determinative step using IC is equivalent to TestMethod D4327.5. Significance and Use5.1 This test method al

16、lows the simultaneous determinationof total nitrogen and total phosphorous from one sampledigestion step.5.2 This test method measures oxidized ammonia and or-ganic nitrogen (as nitrate) and soluble nitrate simultaneously.By subtracting the nitrate + nitrite value from a non-digestedsample gives a T

17、KN:TN 5 TKN1NO3-N!1NO2-N! (2)TKN 5 NH3-N1Organic N (3)When using this test method:TKN 5 Digested Sample 2 Non-Digested Sample (4)TKN 5 TN 2 NO3-N 1 NO2-N# (5)where:TN = total nitrogen, andTKN = total Kjeldahl nitrogen.6. Interferences6.1 Interferences can be caused by substances with similarion chro

18、matographic retention times, especially if they are inhigh concentration compared to the analyte of interest. Follow-ing digestion, samples contain high concentrations of sulfatethat can cause column overloading and obscure nitrate andphosphate peaks. The use of columns with high capacity isrequired

19、 to overcome these limitations.6.2 Samples high in chloride from brackish, seawater andbrines may also result in column overloading. Chloride is alsooxidized to chlorate during the digestion step, and thuscontributes to depletion of the persulfate digestion reagent.These can either be diluted or pre

20、-treated to remove excesschloride. Pretreatment usingAg+precipitation or the use of Cl-removal cartridges are accepted for this test method. Dilutionwill increase the detection limits for total nitrogen and phos-phate. The use of pretreatment cartridges may remove particu-lates if performed prior to

21、 the digestion step, giving a possiblenegative bias.6.3 If very low g/L concentrations are required, blanksubtraction may be used provided the spike recoveries meet themethods detection limits. Approximately 92.5 g/L nitratewere found in the potassium persulfate digestion chemical.This test method p

22、rovides an MDL calculation where a peak isfound in the blank samples/digestion reagent. (See Section 13.)6.4 High levels of organic carbon concentrations greaterthan 800 mg/L of TOC, reducing agents, reduced forms ofmetals, etc. will consume the oxidative reagent that may limitoxidation of reduced n

23、itrogen and phosphorous. (See Fig. 6 andTable 6.)7. Instrumentation7.1 Digestion StepMany techniques exist for heated di-gestion of water samples. Regardless of the instrumentationused, such as UV or microwave, the digestion must proceedlong enough to consume all persulfate.7.1.1 Autoclave or heatin

24、g block or alternative, capable of120C for 60 minutes.7.2 Digestion TubesOD L: 16 125 mm disposableglass tubes with screw caps.7.3 Analytical balance, capable of weighing up to 200 gaccurately to 60. 01 g.7.4 Pipettes or Volumetric Transfer1- and 5-mL Class Avolumetric pipettes or calibrated variabl

25、e volume automaticpipettes fitted with disposable polypropylene tips.TABLE 1 Calibration, Linearity, Limits of Detection, and Quantitation from the Single Lab Validation StudyAnalyteCalibration Range(g/L)LinearityA(r2)System Digested SampleLODB(g/L)LOQC(g/L)LOD(g/L)LOQ(g/L)Nitrate-N 2.5300 0.9999 0.

26、76 2.5 Nitrate-N 2.5300 0.9999 1.0 3.4 171D171Phosphate-P 2.5300 0.9999 1.3 4.2 19.5E63EATen calibration levels, each injected in duplicate.BLODcalculatedas3S/N.CLOQ calculated as 10 S/N.DNitrate MDLb5 A1tsn 2 1,12 5 0.99dSbwhere:A = the average method blank concentration,tsn 2 1,12 5 0.99d= the stu

27、dents t-value for the single-tailed 99th percentile t statistic a standard deviation estimate with n 1 degrees of freedom, andSb= the sample standard deviation of the replicate blank analyses.EPhosphate LOD/LOQ was calculated based on a dilution factor of 15 relative to the system concentrations.D80

28、01 1627.5 Filter paper, 0.45 m, required for removing particu-lates from samples prior to injection into the ion chromato-graph.7.6 Volumetric Flasks25-, 50-, 100-, and 1000-mL ClassA volumetric flasks.7.7 Sample collection container, standard HDPE plastic orglass 100-mL bottle with cap.7.8 Sonicato

29、r.7.9 Ion ChromatographAnalytical system with all re-quired accessories, columns, high-pressure dual piston pump,suppressor, and conductivity detector.7.9.1 Injection system, capable of delivering 5 500 Lwitha precision better than 1 %.7.9.2 Pumping system, capable of delivering mobile phaseflows be

30、tween 0.1 and 5.0 mL/min with a precision better than2 %. Due to the corrosive nature of the eluent, a PEEK(polyether ether ketone) pump head is recommended.7.9.3 Guard column, for protection of the analytical columnfrom strongly retained constituents.7.9.4 Anion exchange column, capable of producin

31、g satis-factory analyte separation of anions.7.9.5 Anion suppressor device, capable of using electrolyticor chemical suppression technology.NOTE 1Sequential suppressor device, when using carbonate basedeluent, helps reducing background to achieve lower detection levels.7.9.6 Conductivity detector, (

32、low volume), temperature con-trolled to 0.01C, capable of at least 0 to 3000 S/cm or greateron a linear scale.7.9.7 Chromatography data system software, capable ofmeasuring peak areas or peak heights, retention times, andbaseline correction capability.7.10 Refrigerator, capable of holding 6C7.11 Bor

33、osilicate medicine bottle, 100 mL.FIG. 1 Separation of Nitrite, Nitrate, and Phosphate Standards in Reagent Water by Ion ChromatographyNOTE 1See Fig. 1 for chromatographic conditions.FIG. 2 Separation of a Nitrate (101 g/L) and Phosphate (105 g/L) from an Alkaline Persulfate Digested Sample of Glyci

34、ne and Glycer-olphosphateD8001 1638. Reagents8.1 Purity of Reagents3Reagent grade or higher puritychemicals and water shall be used for the preparation of allsamples, standards and eluent solutions. See SpecificationD1193; type II water should be used.8.2 Sodium hydroxide, 1.5 M. In a 100-mL volumet

35、ric flaskadd approximately 80 mL of filtered degassed deionized (DI)water. Add 8.0 mL of 50 % NaOH solution and swirl to mix.Fill to the mark with DI water, cap, and invert at least threetimes to mix. Transfer the solution to a polypropylene bottle inwhich it is stable for six months at 4C.8.3 Alkal

36、ine Persulfate Digestion ReagentIna50mLvolumetric flask add 40 mL of DI water. Add 5 mL of the1.5-M stock NaOH solution followed by 2.0 g of potassiumpersulfate. Cap and sonicate for 10 min. Bring to mark with DIwater, cap, and invert at least three times to mix. Do not heat.This solution should las

37、t at least three days if kept refrigerated.Excellent recoveries were achieved even with the formation ofa precipitate after a few days as long as care is taken to nottransfer any precipitate to the samples prior to digestion.8.4 IC Eluent Buffer SolutionContinuous Eluent Genera-tion (optional), to a

38、utomatically prepare and purify the eluentused in the ion chromatography. Electrolytic eluent generationand auto-burette preparation of eluent by means of in-linedilution of a stock solution have been found satisfactory forthis test method. Other continuous eluent generation devicesmay be used if th

39、e precision and accuracy of the method are notdegraded.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.

40、, Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.NOTE 1See Fig. 1 for chromatographic conditions.FIG. 3 Separation of Anions, Including Nitrate (5 g/L) and Phosphate (22 g/L), from an Undigested, Sewage SampleNO

41、TE 1See Fig. 1 for chromatographic conditions.FIG. 4 Separation of Anions, Including Nitrate (262 g/L) and Phosphate (30 g/L) from an Alkaline Persulfate Digested, Raw SewageSampleD8001 1648.5 IC Eluent Suppression Anion Suppressor Device, re-duces the background conductivity of the eluent after sep

42、ara-tion by the anion separator column. Both chemical (sequential)and continuous electrolytic suppressors have been found sat-isfactory for this test method. Other anion suppressor devicesmay be used as long as the precision and accuracy of themethod are not degraded.8.6 Suppressor Regeneration solu

43、tion (if needed)Prepare0.5-M SulfuricAcid Solution by adding 28 mL of concentratedsulfuric acid into 1 L of DI water. Sulfuric acid is not neededwhen using electrolytic eluent generation. (WarningSolution will get hot, so use proper PPE while preparing thissolution.) Alternatively, commercially avai

44、lable 0.5 M sulfuricacid may be used.9. Preparation of Standard Solutions9.1 Solutions used to calibrate the IC system:9.1.1 Potassium Nitrate Stock Calibrant Solution, 1 mL=1.0 mg-NDissolve 0.72 g of potassium nitrate (KNO3,FW= 101.1) in about 80 mL of DI water in a 100-mL volumetricflask. Dilute t

45、his solution to the mark with DI water and mix itthoroughly by manual inversion and shaking. Transfer thestock calibrant to a 100-mL borosilicate media bottle in whichit is stable for 6 months at 4C (see Note 2).9.1.2 Potassium Di-Hydrogen Phosphate Stock CalibrantSolution, 1 mL =1.0 mg-PDissolve 0.

46、44 g potassium di-hydrogen phosphate (KH2PO4, FW = 136.09) in about 80 mLof DI water in a 100-mL volumetric flask. Dilute this solutionto the mark with DI water and mix it thoroughly by manualinversion. Transfer the stock calibrant to a 100-mL borosilicatemedia bottle in which it is stable for 6 mon

47、ths at 4C (see Note3).9.1.3 Mixed IC Calibration Stock Solution 10 mg/L N and10 mg/L PIn a 100 mL volumetric flask add 1.0 mL of theFIG. 5 Isocratic Separation of Nitrate (25 g/L) and Phosphate (25 g/L) from an Alkaline Persulfate Digested with Carbonate/Bicarbonate EluentNOTE 1See Fig. 1 for chroma

48、tographic conditions.FIG. 6 Separation of Nitrate and Phosphate in the Presence of 1000 mg/L ChlorideD8001 165stock N and 1.0 mL of the stock P solution. Fill to the markwith DI water, cap and mix thoroughly by manual inversion.Prepare this solution fresh each time calibration solutions areprepared.

49、NOTE 2Alternatively, commercial stock calibration solutions can beused, provided that the solutions are traceable to primary stock solutionsor certified reference materials, and are free from other analytes.NOTE 3In case of trace level of phosphorous contamination inreagents, it is highly recommended to matrix match the standardspreparation in order to nullify the effect of phosphorous in reagent. (SeeSection 11 for additional information.)9.1.4 Working Calibration SolutionsUse the amounts inTable 2 to