1、Designation: D2972 15Standard Test Methods forArsenic in Water1This standard is issued under the fixed designation D2972; 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 indicates
2、the year of last reapproval. Asuperscript epsilon () 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:Concen
3、trationRangeSectionsTest Method ASilver Diethyldithio-carbamate Colorimetric5 to 250 g/L 7 to 16Test Method BAtomic Absorption,Hydride Generation1to20g/L 17 to 26Test Method CAtomic Absorption,Graphite Furnace5 to 100 g/L 27 to 361.2 The analyst should direct attention to the precision andbias state
4、ments for each test method. It is the users responsi-bility to ensure the validity of these test methods for waters ofuntested matrices.1.3 The values stated in SI units are to be regarded asstandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided f
5、or informa-tion only and are not considered standard.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 determine the applica-bility o
6、f regulatory limitations prior to use. For specific hazardstatements, see 11.1 and 20.2.2. Referenced Documents2.1 ASTM Standards:3D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19
7、 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3919 Practice for Measuring Trace Elements in Water byGraphite Furnace Atomic Absorption SpectrophotometryD4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD5810 Guide for Spiki
8、ng into Aqueous SamplesD5673 Test Method for Elements in Water by InductivelyCoupled PlasmaMass SpectrometryD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisE60 Practice for Analysis of Metals, Ores, and RelatedMaterials by SpectrophotometryE275 Pr
9、actice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in these test methods,refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 total recoverable arsenic, na descri
10、ptive term relat-ing to the arsenic forms recovered in the acid-digestionprocedure specified in these test methods.3.2.1.1 DiscussionSome organic-arsenic compounds,such as phenylarsonic acid, disodium methane arsonate, anddimethylarsonic acid, are not recovered completely during thedigestion step.4.
11、 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. Purity of Reagents5.1 Reagent grade chemicals shall be used in all tests.Unless
12、 otherwise indicated, it is intended that all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society, where such1These test methods are under the jurisdiction of ASTM Committee D19 onWater and are the direct responsibility of Subcommittee
13、D19.05 on InorganicConstituents in Water.Current edition approved Feb. 1, 2015. Published March 2015. Originallyapproved in 1993. Last previous edition approved in 2008 as D2972 08. DOI:10.1520/D2972-15.2Similar to that appearing in Standard Methods for the Examination of Waterand Wastewater, 12th e
14、dition, APHA, Inc., New York, NY, 1965; and identical withthat in Brown, E., Skougstad, M. W., and Fishman, M. J., “Methods for Collectionand Analysis of Water Samples for Dissolved Minerals and Gases,” Techniques ofWater-Resources Investigations of the U.S. Geological Survey, Book 5, 1970, p. 46.3F
15、or 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 page onthe ASTM website.*A Summary of Changes section appears at the end of this standa
16、rdCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1specifications are available.4Other grades may be used, pro-vided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accurac
17、y ofthe determination.5.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto 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
18、 use without adverselyaffecting the bias and precision of the test method. Type IIwater was specified at the time of round robin testing of thesetest methods.6. Sampling6.1 Collect the sample in accordance with Practices D3370.6.2 Preserve the samples with HNO3(sp gr 1.42) to a pH of2 or less immedi
19、ately at the time of collection; normally about2 mL/L is required. If only dissolved arsenic is to bedetermined, filter the sample through a 0.45-m membranefilter before acidification. The holding times for the samplesmay be calculated in accordance with Practice D4841.NOTE 1Alternatively, the pH ma
20、y be adjusted in the laboratory if thesample is returned within 14 days. However, acid must be added at least24 hours before analysis to dissolve any metals that adsorb to the containerwalls. This could reduce hazards of working with acids in the field whenappropriate.TEST METHOD ASILVERDIETHYLDITHI
21、OCARBAMATE 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 reagentwater, river water, and process water. The informati
22、on 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 sulfuric and nitric acids and repeatedly evaporatin
23、gthe 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 inhydrochloric acid solution. The resulting mixture of gase
24、s 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-colored silver sol having maximum absorbance at about
25、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 ofinterferences, several metals, notably cobalt, nickel, mercury,silver, platinum, co
26、pper, chromium, and molybdenum, mayinterfere with the evolution of arsine and with the recovery ofarsenic. The presence of any or all of these metals in a samplebeing analyzed must be considered as a potential source ofinterference, and the analyst must fully determine the extent ofactual interferen
27、ce, if any. This could be accomplished byspiking.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 stibine, which distillsalong with the arsine. Stibine reac
28、ts 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 arsenic).9.4 Nitric acid interferes with the test and mu
29、st be com-pletely eliminated during the digestion.10. Apparatus10.1 Arsine Generator, Scrubber, and Absorber,5assembledas shown in Fig. 1.10.2 Spectrophotometer or Filter Photometer, suitable foruse at 540 nm and providing a light path of at least 10 mm. Thefilter photometer and photometric practice
30、 prescribed in thismethod shall conform to Practice E60. The spectrophotometershall conform to Practice E275.11. Reagents and Materials11.1 Arsenic Solution, Stock (1.00 mL = 1.00 mg As)Commercially purchase or dissolve 1.320 g of arsenic trioxide(As2O3)(WarningArsenic trioxide is extremely toxic.Av
31、oidingestion or inhalation of dry powder during standard prepa-ration. Wash hands thoroughly immediately after handlingarsenic trioxide. Under no circumstances pipette any arsenicsolutions by mouth.), dried for at least1hat110C, in 10 mLof NaOH solution (420 g/L) and dilute to 1 L with water. Thisso
32、lution is stable. A purchased arsenic stock solution ofappropriate known purity is acceptable.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 mL = 1.00 g As)Dilute 10.0 mLof arsenic intermediat
33、e solution to 100 mLwithwater. Prepare fresh before each use.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BD
34、H Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5Available commercially.D2972 15211.4 Filter PaperPurchase suitable filter paper. Typicallythe filter papers have a pore size of 0.45-m membrane.Material su
35、ch as fine-textured, acid-washed, ashless paper, orglass fiber paper are acceptable. The user must first ascertainthat the filter paper is of sufficient purity to use withoutadversely affecting the bias and precision of the test method.11.5 Hydrochloric Acid (sp gr 1.19)Concentrated hydro-chloric ac
36、id (HCl). Use analytical grade acid with an arseniccontent not greater than 1 106%.11.6 Lead Acetate Solution (100 g/L)Dissolve 10 g of leadacetate (Pb(C2H3O2)23H2O) in 100 mLof water. Store reagentin a tightly stoppered container.11.7 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3). Use anal
37、ytical grade acid with an arsenic content notgreater than 1 106%.11.8 Nitric Acid (1+1)Add 250 mLof concentrated nitricacid (sp gr 1.42) to 250 mL of water.11.9 Potassium Iodide Solution (150 g/L)Dissolve 15 g ofpotassium iodide (KI) in 100 mL of water. Store in an amberbottle.11.10 Silver Diethyldi
38、thiocarbamate SolutionDissolve 1 gof silver diethyldithiocarbamate (AgDDC) in 200 mL ofpyridine. This solution is stable for at least several monthswhen stored in an amber bottle.11.11 Sodium Hydroxide Solution (420 g/L)Dissolve 42 gof sodium hydroxide (NaOH) pellets in 100 mL of water.(WarningThis
39、is a very exothermic reaction.)11.12 Stannous Chloride SolutionDissolve 40 g ofarsenic-free stannous chloride (SnCl22H2O) in 100 mL of HCl(sp gr 1.19). Add a few small pieces of mossy tin (which is thecommon name and is commercially available).11.13 Sulfuric Acid (1+1)Cautiously, and with constantst
40、irring and cooling, add 250 mL of concentrated H2SO4(sp gr1.84) to 250 mL of water.11.14 Zinc, Granular, 20-mesh. Arsenic content must notexceed 1 106%.12. Standardization12.1 Clean all glassware before use by rinsing first with hotHNO3(1+1)(11.7) and then with water. The absorbers mustbe additional
41、ly 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 standardsolution to approximately 100 mL with water. Analyze at leastfive or more working st
42、andards containing concentrations ofarsenic to define the nonlinear curve that bracket the expectedsample concentration, prior to analysis of samples, to calibratethe instrument. A higher order of the curve may be necessary.12.3 Proceed as directed in 13.3 13.9.12.4 Read directly the concentration o
43、r prepare an analyticalcurve by plotting the absorbances of standards versus micro-grams of arsenic.NOTE 2The response is linear up to 15 g of arsenic; however,because the curve is nonlinear above 15 g, it is necessary to havesufficient standards above 15 g to permit constructing an accurate curve.1
44、3. Procedure13.1 Clean all glassware before use by rinsing first with hotHNO3(1+1)(11.8) and then with water. The absorbers mustbe additionally rinsed with acetone and then air-dried.13.2 Pipette a volume of well-mixed acidified sample con-taining less than 25 g of arsenic (100 mL maximum) into agen
45、erating flask and dilute to approximately 100 mL.NOTE 3If only dissolved arsenic is to be determined use a filtered(11.4) and acidified sample (see 6.2).13.3 To each flask, add 7 mL of H2SO4(1+1)(11.13) and5 mL of concentrated HNO3(11.7) (sp gr 1.42). Add a smallboiling chip and carefully evaporate
46、to dense fumes of SO3,maintaining an excess of HNO3until all organic matter isdestroyed. This prevents darkening of the solution and possiblereduction and loss of arsenic. Cool, add 25 mL of water, andagain evaporate to dense fumes of SO3. Maintain heating for15 min to expel oxides of nitrogen.13.4
47、Cool, and adjust the volume in each flask to approxi-mately 100 mL with water.FIG. 1 Arsine Generator, Scrubber, and Absorber5D2972 15313.5 To each flask add successively, with thorough mixingafter each addition, 8 mL of concentrated HCl (11.5) (sp gr1.19), 4 mL of KI solution (11.9), and 1 mL of Sn
48、Cl2solution(11.12). Allow about 15 min for complete reduction of thearsenic 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 corr
49、ectly adjusted. Add 3.00 mL of silverdiethyldithiocarbamate-pyridine solution (11.10) to each ab-sorber. Add glass beads to the absorbers until the liquid justcovers them.NOTE 4Four millilitres of silver diethyldithiocarbamate-pyridinesolution may be used with some loss of sensitivity.13.7 Disconnect each generator, add6gofzinc (11.14), andreconnect immediately.13.8 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
