ASTM D2972-2003 Standard Test Methods for Arsenic in Water《水中砷的标准试验方法》.pdf

1、Designation: D 2972 03Standard Test Methods forArsenic in Water1This standard is issued under the fixed designation D 2972; 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 parentheses indicate

2、s the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods2cover the photometric and atomicabsorption determination of arsenic in most waters and waste-waters. Three test methods are given as follows:Con

3、centrationRangeSectionsTest Method ASilver Diethyldithio-carbamate Colorimetric5 to 250 g/L 7 to 15Test Method BAtomic Absorption,Hydride Generation1to20g/L 16to24Test Method CAtomic Absorption,Graphite Furnace5to100g/L 25to331.2 The analyst should direct attention to the precision andbias statement

4、s for each test method. It is the users responsi-bility to ensure the validity of these test methods for waters ofuntested matrices.1.3 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 establ

5、ish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see Note 1 and Note 6.2. Referenced Documents2.1 ASTM Standards:D 1129 Terminology Relating to Water3D 1193 Specification for Reagent Water3D 2777 Prac

6、tice for Determination of Precision and Bias ofApplicable Methods of Committee D19 on Water3D 3370 Practices for Sampling Water from Closed Con-duits3D 3919 Practice for Measuring Trace Elements in Water byGraphite Furnace Atomic Absorption Spectrophotometry3D 4841 Practice for Estimation of Holding

7、 Time for WaterSamples Containing Organic and Inorganic Constituents3D 5810 Guide for Spiking into Aqueous Samples3D 5847 Practice for the Writing Quality Control Specifica-tions for Standard Test Methods for Water Analysis3E60 Practice for Photometric and SpectrophotometricMethods for Chemical Anal

8、ysis of Metals4E 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible, and Near Infrared Spectrophotom-eters53. Terminology3.1 Definitions of Term Specific to This Standard:3.1.1 For definitions of terms used in these test methodsrefer to Terminology D 1129.3.2 Definitions of

9、 Terms Specific to This Standard:3.2.1 total recoverable arsenican arbitrary analytical termrelating to the forms of arsenic that are determinable by thedigestion method which is included in the procedure. Someorganic-arsenic compounds, such as phenylarsonic acid, diso-dium methane arsonate, and dim

10、ethylarsonic acid, are notrecovered completely during the digestion step.4. Significance and Use4.1 Herbicides, insecticides, and many industrial effluentscontain arsenic and are potential sources of water pollution.Arsenic is significant because of its adverse physiologicaleffects on humans.5. Puri

11、ty of Reagents5.1 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 are available.6Other grades may be us

12、ed, pro-vided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.1These test methods are under the jurisdiction of ASTM Committee D19 onWater and are the direct responsibility of Subcommittee D 19.05 on Inorgani

13、cConstituents in Water.Current edition approved Jan. 10, 2003. Published January 2003. Originallyapproved in 1993. Last previous edition approved in 1997 as D 2972 97.2Similar to that appearing in Standard Methods for the Examination of Waterand Wastewater, 12th edition, APHA, Inc., New York, NY, 19

14、65, and identical withthat in Brown, Eugene, Skougstad, M. W., and Fishman, M. J., “Methods forCollection and Analysis of Water Samples for Dissolved Minerals and Gases,”Techniques of Water-Resources Investigations of the U.S. Geological Survey, Book5, Chapter , 1970 p. 46.3Annual Book of ASTM Stand

15、ards, Vol 11.01.4Annual Book of ASTM Standards, Vol 03.05.5Annual Book of ASTM Standards, Vol 03.06.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Anala

16、r Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United 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 Dri

17、ve, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 Purity of Water Unless otherwise indicated, refer-ences to water shall be understood to mean reagent waterconforming to Specification D 1193 Type I. Other reagentwater types may be used provided it is first ascertained that thewate

18、r is of sufficiently high purity to permit its use withoutadversely affecting the bias and precision of the test method.Type II water was specified at the time of round robin testingof this test method.6. Sampling6.1 Collect the sample in accordance with Practices D 3370.6.2 Preserve the samples wit

19、h HNO3(sp gr 1.42) to a pH of2 or less immediately at the time of collection; normally about2 mL/L is required. If only dissolved arsenic is to be deter-mined, filter the sample through a 0.45-m membrane filterbefore acidification. The holding times for the samples may becalculated in accordance wit

20、h Practice D 4841.TEST METHOD ASILVERDIETHYLDITHIOCARBAMATE COLORIMETRIC7. Scope7.1 This test method covers the determination of dissolvedand total recoverable arsenic in most waters and waste watersin the range from 5 to 250 g/L of arsenic.7.2 The precision and bias data were obtained on reagentwat

21、er, river water, and process water. The information onprecision and bias may not apply to other waters. It is the usersresponsibility to ensure the validity of this test method forwaters of untested matrices.8. Summary of Test Method8.1 Organic arsenic-containing compounds are decomposedby adding su

22、lfuric and nitric acids and repeatedly evaporatingthe sample to fumes of sulfur trioxide. The arsenic (V) soproduced, together with inorganic arsenic originally present, issubsequently reduced to arsenic (III) by potassium iodide andstannous chloride, and finally to gaseous arsine by zinc inhydrochl

23、oric acid solution. The resulting mixture of gases ispassed through a scrubber containing borosilicate wool im-pregnated with lead acetate solution and then into an absorp-tion tube containing a solution of silver diethyldithiocarbamatein pyridine. Arsine reacts with this reagent to form a red-color

24、ed silver sol having maximum absorbance at about 540nm. The absorbance of the solution is measured photometri-cally and the arsenic determined by reference to an analyticalcurve prepared from standards.9. Interferences9.1 Although many samples are relatively free of interfer-ences, several metals, n

25、otably cobalt, nickel, mercury, silver,platinum, copper, chromium, and molybdenum, may interferewith the evolution of arsine and with the recovery of arsenic.The presence of any or all of these metals in a sample beinganalyzed must be considered as a potential source of interfer-ence, and the analys

26、t must fully determine the extent of actualinterference, if any. This could be accomplished by spiking.9.2 Hydrogen sulfide and other sulfides interfere, but com-monly encountered quantities are effectively removed by thelead acetate scrubber and the digestion.9.3 Antimony interferes by forming stib

27、ine, which distillsalong with the arsine. Stibine reacts with the color-formingreagent to form a somewhat similar red sol having maximumabsorbance near 510 nm. The sensitivity for antimony at 540nm is only about 8 % that of arsenic (1 mg/L of antimony willshow an apparent presence of 0.08 mg/L of ar

28、senic).9.4 Nitric acid interferes with the test and must be com-pletely eliminated during the digestion.10. Apparatus10.1 Arsine Generator, Scrubber, and Absorber7, assembledas shown in Fig. 1.10.2 Spectrophotometer or Filter Photometer, suitable foruse at 540 nm and providing a light path of at lea

29、st 10 mm. Thefilter photometer and photometric practice prescribed in thismethod shall conform to Practice E60. The spectrophotometershall conform to Practice E 275.11. Reagents11.1 Arsenic Solution, Stock (1.00 mL = 1.00 mg As)Dissolve 1.320 g of arsenic trioxide (As2O3)(Warning, see7Available comm

30、ercially.FIG. 1 Arsine Generator, Scrubber, and Absorber7D2972032Note 1), dried for at least1hat110C, in 10 mL of NaOHsolution (420 g/L) and dilute to 1 L with water. This solution isstable.NOTE 1Warning: Arsenic trioxide is extremely toxic. Avoid inges-tion or inhalation of dry powder during standa

31、rd preparation. Wash handsthoroughly immediately after handling arsenic trioxide. Under no circum-stances pipet any arsenic solutions by mouth.11.2 Arsenic Solution, Intermediate (1.00 mL = 10.0 gAs) Dilute 5.00 mL of arsenic stock solution to 500 mL withwater.11.3 Arsenic Solution, Standard (1.00 m

32、L = 1.00 g As)Dilute 10.0 mLof arsenic intermediate solution to 100 mLwithwater. Prepare fresh before each use.11.4 Hydrochloric Acid (sp gr 1.19)Concentrated hydro-chloric acid (HCl). Use analytical grade acid with an arseniccontent not greater than 1 3 106%.11.5 Lead Acetate Solution (100 g/L)Diss

33、olve 10 g oflead acetate (Pb(C2H3O2)23H2O) in 100 mL of water. Storereagent in a tightly stoppered container.11.6 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3). Use analytical grade acid with an arsenic content notgreater than 1 3 106%.11.7 Nitric Acid (1 + 1)Add 250 mL of concentratednitri

34、c acid (sp gr 1.42) to 250 mL of water.11.8 Potassium Iodide Solution (150 g/L)Dissolve 15 g ofpotassium iodide (KI) in 100 mL of water. Store in an amberbottle.11.9 Silver Diethyldithiocarbamate SolutionDissolve 1 gof silver diethyldithiocarbamate (AgDDC) in 200 mL ofpyridine. This solution is stab

35、le for at least several monthswhen stored in an amber bottle.11.10 Sodium Hydroxide Solution (420 g/L)Dissolve 42 gof sodium hydroxide (NaOH) pellets in 100 mL of water.11.11 Stannous Chloride SolutionDissolve 40 g ofarsenic-free stannous chloride (SnCl22H2O) in 100 mLof HCl(sp gr 1.19). Add a few s

36、mall pieces of mossy tin.11.12 Sulfuric Acid (1 + 1)Cautiously, and with constantstirring and cooling, add 250 mL of concentrated H2SO4(sp gr1.84) to 250 mL of water.11.13 Zinc, Granular, 20-mesh. Arsenic content must notexceed 1 3 106%.12. Standardization12.1 Clean all glassware before use by rinsi

37、ng first with hotHNO3(1 + 1) and then with water. The absorbers must beadditionally rinsed with acetone and then air-dried.12.2 Prepare, in a 250-mL generator flask, a blank andsufficient standards containing from 0.0 to 25.0 g of arsenicby diluting 0.0 to 25.0-mL portions of the arsenic standardsol

38、ution to approximately 100 mL with water.12.3 Proceed as directed in 13.3-13.9.12.4 Construct an analytical curve by plotting the absor-bances of standards versus micrograms of arsenic.NOTE 2The response is linear up to 15 g of arsenic; however,because the curve is nonlinear above 15 g, it is necess

39、ary to havesufficient standards above 15 g to permit constructing an accurate curve.13. Procedure13.1 Clean all glassware before use by rinsing first with hotHNO3(1 + 1) and then with water. The absorbers must beadditionally rinsed with acetone and then air-dried.13.2 Pipet a volume of well-mixed ac

40、idified sample con-taining less than 25 g of arsenic (100 mL maximum) into agenerating flask and dilute to approximately 100 mL.NOTE 3If only dissolved arsenic is to be determined use a filtered andacidified sample (see 6.2).13.3 To each flask, add 7 mL of H2SO4(1+1)and5mLofconcentrated HNO3. Add a

41、small boiling chip and carefullyevaporate to dense fumes of SO3, maintaining an excess ofHNO3until all organic matter is destroyed. This preventsdarkening of the solution and possible reduction and loss ofarsenic. Cool, add 25 mL of water, and again evaporate todense fumes of SO3. Maintain heating f

42、or 15 min to expeloxides of nitrogen.13.4 Cool, and adjust the volume in each flask to approxi-mately 100 mL with water.13.5 To each flask add successively, with thorough mixingafter each addition, 8 mL of concentrated HCl, 4 mL of KIsolution, and 1 mL of SnCl2solution. Allow about 15 min forcomplet

43、e reduction of the arsenic to the trivalent state.13.6 Place in each scrubber a plug of borosilicate wool thathas been impregnated with lead acetate solution. Assemble thegenerator, scrubber, and absorber, making certain that all partsfit and are correctly adjusted. Add 3.00 mL of silverdiethyldithi

44、ocarbamate-pyridine solution to each absorber.Addglass beads to the absorbers until the liquid just covers them.NOTE 4Four millilitres of silver diethyldithiocarbamate-pyridine so-lution may be used with some loss of sensitivity.13.7 Disconnect each generator, add6gofzinc, andreconnect immediately.1

45、3.8 Allow 30 min for complete evolution of arsine. Warmthe generator flasks for a few minutes to make sure that allarsine is released.13.9 Pour the solutions from the absorbers directly intoclean spectrophotometer cells and within 30 min measure theabsorbance of each at 540 nm.14. Calculation14.1 De

46、termine the weight of arsenic in each sample byreferring to the analytical curve. Calculate the concentration ofarsenic in the sample in micrograms per litre, using Eq 1:Arsenic, g/L 5 1000 W/V (1)where:V = volume of sample, mL, andW = weight of arsenic in sample, g.15. Precision and Bias815.1 The s

47、ingle-operator and overall precision of thismethod for three laboratories, which included a total of sixoperators analyzing each sample on three different days, within8Supporting data are available from ASTM Headquarters. RequestRR:D 19 1049.D2972033its designated range varies with the quantity bein

48、g tested inaccordance with Table 1.15.2 Recoveries of known amounts of arsenic (arsenictrioxide) in a series of prepared standards are given in Table 1.15.3 The precision and bias data were obtained on reagentwater, river water, and process water. The information onprecision and bias may not apply t

49、o other waters. It is the usersresponsibility to ensure the validity of this test method forwaters of untested matrices.15.4 Three independent laboratories participated in theroundrobin study. Precision and bias for this test methodconform to Practice D 2777 77, which was in place at thetime of collaborative testing. Under the allowances made in 1.4of Practice D 2777 98, these precision and bias data do meetexisting requirements for interlaboratory studies of CommitteeD19 test methods.16. Quality Control16.1 In order to be certain that