1、Designation: D1687 12Standard Test Methods forChromium in Water1This standard is issued under the fixed designation D1687; 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 These test methods cover the determination of hexava-lent and total chromium in wate
3、r. Three test methods areincluded as follows:Test Method ConcentrationRangeSectionsAPhotometric Diphenyl-carbohydrazide0.01 to 0.5mg/L7-15BAtomicAbsorption, Direct0.1to10mg/L16-24CAtomic Absorption,Graphite Furnace5to100g/L25-331.2 Test Method A is a photometric method that measuresdissolved hexaval
4、ent chromium only. Test Methods B and Care atomic absorption methods that are generally applicable tothe determination of dissolved or total recoverable chromiumin water without regard to valence state.1.3 Test Method A has been used successfully with reagentgrade water Types I, II, and III, tap wat
5、er, 10 % NaCl solution,treated water from a synthetic organic industrial plant thatmeets National Pollution Discharge Elimination System(NPDES) permit requirements, and EPA-extraction procedureleachate water, process water, lake water, effluent treatment,that is, lime neutralization and precipitatio
6、n of spent pickleliquor and associated rinse water from stainless steel pickling.Test Method C has been used successfully with reagent water,stock scrubber water, lake water, filtered tap water, river water,well water, production plant water, and a condensate from amedium BTU coal gasification proce
7、ss. Matrices used, exceptfor reagent water, are not available for Test Method B. It is theusers responsibility to ensure the validity of these test methodsfor waters of untested matrices.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values
8、 stated ineach system are mathematical conversions and may not beexact equivalents; therefore, each system shall be used inde-pendently of the other.1.5 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 s
9、tandard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see 4.2 and Note 6 and Note 7.2. Referenced Documents2.1 ASTM Standards:2D858 Test Methods for Manganese in WaterD1066 Practice for Sa
10、mpling SteamD1068 Test Methods for Iron in WaterD1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD1688 Test Methods for Copper in WaterD1691 Test Methods for Zinc in WaterD1886 Test Methods for Nickel in WaterD2777 Practice for Determination of Precision and Bias ofApplicable
11、Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3557 Test Methods for Cadmium in WaterD3558 Test Methods for Cobalt in WaterD3559 Test Methods for Lead in WaterD3919 Practice for Measuring Trace Elements in Water byGraphite Furnace Atomic Absorption Spec
12、trophotometryD4691 Practice for Measuring Elements in Water by FlameAtomic Absorption SpectrophotometryD4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Sp
13、ecificationsfor Standard Test Methods for Water AnalysisE60 Practice for Analysis of Metals, Ores, and RelatedMaterials by SpectrophotometryE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers1These test methods are under the jurisdiction of ASTM Commit
14、tee D19 onWater and are the direct responsibility of Subcommittee D19.05 on InorganicConstituents in Water.Current edition approved Sept. 1, 2012. Published August 2007. Originallyapproved in 1959. Last previous edition approved in 2007 as D1687 02(2007)E01.DOI: 10.1520/D1687-12.2For referenced ASTM
15、 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 standardCopyright ASTM I
16、nternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 DefinitionsFor definitions of terms used in these testmethods, refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 Laboratory Control Sample, na solutio
17、n with thecertified concentration(s) of the analytes.4. Significance and Use4.1 Hexavalent chromium salts are used extensively inmetal finishing and plating applications, in anodizingaluminum, and in the manufacture of paints, dyes, explosives,and ceramics. Trivalent chromium salts are used as morda
18、nts intextile dyeing, in the ceramic and glass industry, in the leatherindustry as a tanning agent, and in photography. Chromiummay be present in wastewater from these industries and mayalso be discharged from chromate-treated cooling waters.4.2 The hexavalent state of chromium is toxic to humans,an
19、imals, and aquatic life. It can produce lung tumors wheninhaled and readily induces skin sensitization.5. Purity 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 Analy
20、ticalReagents of the American Chemical Society3where suchspecifications are available. Other grades may be used, pro-vided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.5.2 Purity of WaterUnless otherwise i
21、ndicated, referencesto water shall be understood to mean reagent water conformingto Specification D1193, Type I, II, or III water. Type I ispreferred and more commonly used. Type II water wasspecified at the time of round robin testing of these testmethods.NOTE 1The user must ensure the type of reag
22、ent water chosen issufficiently free of interferences. The water should be analyzed using thetest method.6. Sampling6.1 Collect the sample in accordance with the applicableASTM standard as follows: Practice D1066, or PracticeD3370. The holding time for the samples may be calculated inaccordance with
23、 Practice D4841.6.2 Samples to be analyzed by Test Method A should bestabilized upon collection by addition of sodium hydroxidesolution to a pH greater than or equal to 8, or analyzedimmediately. Minor delays in stabilization or analyses ofsamples containing sulfur reduction compounds can producesig
24、nificant loss in hexavalent chromium. Acidic samples con-taining hypobromite, persulfate, or chlorine could oxidizetrivalent chromium, if present, to hexavalent form uponpreservation, resulting in a positive interference. When thepresence of these oxidizing compounds is suspected, samplesshould not
25、be preserved but analyzed immediately. It will beevident that in this case, the simultaneous presence of reducingcompounds could not be anticipated.6.3 Samples to be analyzed by Test Methods B and C shallbe preserved by addition of HNO3(sp gr 1.42) to pH of 2 orless immediately at the time of collec
26、tion, normally about 2 mLHNO3/L. If only dissolved chromium is to be determined, thesample shall be filtered through a 0.45-m membrane filterbefore acidification.NOTE 2Alternatively, the pH may be adjusted in the laboratory if thesample is returned within 14 days. This could reduce hazards of workin
27、gwith acids in the field when appropriate.TEST METHOD APHOTOMETRICDIPHENYLCARBOHYDRAZIDE7. Scope7.1 This test method covers the determination of dissolvedhexavalent chromium in water.7.2 The test method is applicable in the range from 0.01 to0.5 mg/L chromium. The range may be extended by appropri-a
28、te sample dilution.7.3 This test method has been used successfully withreagent grade water Types I, II, and III, tap water, 10 % NaClsolution, treated water from a synthetic organic industrial plantthat meets NPDES permit requirements, EPA-extraction pro-cedure leachate water, process water, lake wa
29、ter, effluent fromtreatment that is, lime neutralization and precipitation of spentpickle liquor and associated rinse water from stainless steelpickling. It is the responsibility of the user to ensure thevalidity of the test method to waters of untested matrices.8. Summary of Test Method8.1 Hexavale
30、nt chromium reacts with 1.5-diphenylcarbohydrazide (s-diphenylcarbazide) in an acid me-dium to produce a reddish-purple color. The intensity of thecolor formed is proportional to the hexavalent chromiumconcentration.9. Interferences9.1 Vanadium, titanium, or iron present at concentrations of5 mg/L y
31、ield a 10 to 30 % reduction in recovery of chromium.Copper at 100 mg/L yields a 20 to 30 % reduction in recoveryin the presence of sulfate. Mercury gives a blue-purple color,but the reaction is not very sensitive at the pH employed for thetest.9.2 Nitrite concentrations in excess of 10 mg/Las NO2yie
32、ldlow test results. Sulfamic acid may be added (;10.1 g) prior tothe addition of diphenylcarbazide solution to minimize nitriteinterference. Add sulfamic acid only when the presence ofnitrite has been positively established. Excess sulfamic aciditself creates a slightly positive interference.3Reagen
33、t 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 United States Pharmacopeiaand
34、National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D1687 1229.3 Sulfide and sulfite reduce chromate in an acid mediumto give low results.9.4 Several sample matrices have been identified whichproduce a yellow-orange complex that interferes with thisquantification. When this
35、occurs, it may be remedied byinverting the indicator-buffer sequence. In these cases theanalyst should evaluate the matrix effect with the additions ofspikes. (Guide D5810)9.5 Although each interferent has been reported, most of thecommon interferences are eliminated by the preservationprocedure at
36、the time of collection. The potentially interferingmetals are precipitated and the reducing effect of sulfurcompounds has been overcome.10. Apparatus10.1 PhotometerSpectrophotometer or filter photometersuitable for use at 540 nm and equipped with a cell having aminimum path length of 10 mm. The phot
37、ometers and photo-metric practice prescribed in this test method shall conform toPractice E60. Spectrophotometers and spectrophotometricpractice shall conform to Practice E275.11. Reagents11.1 Chromium Solution, Stock (1 mL = 0.10 mg Cr)Dissolve 0.2828 g of potassium dichromate (K2Cr2O7that hasbeen
38、oven dried at 105C for 1 h) in water. Dilute to 1 L withwater. Alternatively, certified stock solutions are commerciallyavailable through chemical supply vendors and may be used.11.2 Chromium Solution, Standard (1 mL = 0.001 mg Cr)Dilute 10.0 mL of chromium stock solution (see 11.1)to1Lwith water.11
39、.3 Diphenylcarbazide Indicator SolutionDissolve 0.25g of powdered 1,5-diphenylcarbohydrazide in 100 mL ofacetone. Store in an amber glass-stoppered flask at 4C whennot in use. This solution is stable for about one week when keptrefrigerated. Prepare fresh reagent when the solution becomesdiscolored.
40、NOTE 3Allow the indicator solution to warm to room temperaturebefore use.11.4 Phosphoric Acid (1+1)Dilute 500 mL of concen-trated phosphoric acid (sp gr 1.69) to 1 L with water.11.5 Phosphoric Acid (1 + 19)Dilute 50 mL of concen-trated phosphoric acid (sp gr 1.69) to 1 L with water.11.6 Sodium Hydro
41、xide Solution (40 mg/L)Dissolve 40mg of sodium hydroxide (NaOH) in water. Cool and dilute to1 L. This solution is used for sample preservation.11.7 Sulfamic Acid(NH2SO3H)Crystals.12. Calibration12.1 Prepare a series of at least four standard solutionscontaining from 0 to 0.50 mg/L of chromium by dil
42、utingmeasured volumes of the standard chromium solution (see11.2) to 100 mL with water in separate volumetric flasks.12.2 Transfer 50 mL of each prepared standard solution toseparate 125-mL Erlenmeyer flasks and proceed with13.3-13.6.12.3 Prepare a calibration curve by plotting milligrams perliter o
43、f chromium versus absorbance on linear graph paper.12.4 A calibration curve must be prepared for each photom-eter. A recalibration must be made if any alterations of theinstrument are made or if new reagents are prepared. At theleast, a blank and three chromium standard solutions must beanalyzed to
44、verify the original test calibration each time the testis performed.13. Procedure13.1 Filter a portion of the sample through a 0.45-mmembrane filter and adjust the pH into the 8 to 8.5 range if itis greater than 8.5 with a few drops of the phosphoric acidsolution (1 + 19).13.2 Transfer 50.0 mL of th
45、e filtered sample, or a smalleraliquot of sample diluted to 50.0 mL, to a 125-mL Erlenmeyerflask.13.3 Add 2.0 mL of the diphenylcarbazide solution to eachsolution and swirl to mix.NOTE 4If the sample is colored, prepare a separate aliquot asdescribed in 13.1 and 13.2. Add 2.0 mL of acetone instead o
46、f diphenyl-carbazide solution and proceed with 13.4 and 13.5. Use this solution as thesample blank.13.4 Immediately add 5.0 mL of phosphoric acid solution(1 + 1) to each solution and swirl to mix.13.5 Permit the solutions to stand 15 min for full colordevelopment. Measure the absorbance within 30 mi
47、n after theaddition of the diphenylcarbazide solution at 540 nm with acell having a minimum path length of 10 mm.13.6 Determine milligrams per liter of chromium as Cr+6inthe test sample by referring the absorbance to the preparedcalibration curve (see 12.3).14. Calculation14.1 Calculate the hexavale
48、nt chromium concentration asfollows:Cr16, mg/L 5 WS2 WB!50/S! (1)where:WS= chromium found in the sample, mg/L (see 13.6),WB= chromium found in the sample blank, mg/L(see 13.6),andS = volume of sample used, mL (see 13.2).15. Precision and Bias15.1 The collaborative test data were obtained on reagentg
49、rade water Types I, II, and III, tap water, 10 % NaCl solution,treated water from a synthetic organic industrial plant whichmeets NPDES permit requirements, EPA-extraction procedureleachate water, process water, lake water, effluent fromtreatment, that is, lime neutralization and precipitation of spentpickle liquor and associated rinse water from stainless steelpickling.D1687 12315.2 Single-operator and overall precision of this testmethod within its designated range and recovery data for theabove waters for 16 laboratories, which include a total of 16op
