EPA METHOD 7197 Chromium, Hexavalent (Chelation-Extraction)

《EPA METHOD 7197 Chromium, Hexavalent (Chelation-Extraction)》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、METHOD7197CHROMIUM,HEXAVALENT(CHELATION/EXTRACTION)1.0SCOPEANDAPPLICATION1.1Method7197isapprovedfordeterminingtheconcentrationofdissolvedhexavalentchromium[Cr(VI)]inExtractionProcedure(EP)toxicitycharacteristicextractsandgroundwaters.Thismethodmayalsobeapplicabletocertaindomesticandindustrialwast

2、es,providedthatnointerferingsubstancesarepresent(seeParagraph3.1).1.2Method7197maybeusedtoanalyzesamplescontainingfrom1.0to25ugofCr(VI)perliter.2.0SUMMARYOFMETHOD2.1Method7197isbasedonthechelationofhexavalentchromiumwithammoniumpyrrolidinedithiocarbamate(APDC)andextractionwithmethylisobutylketone

3、(MIBK).Theextractisaspiratedintotheflameofanatomicabsorptionspectrophotometer.3.0INTERFERENCES3.1Highconcentrationsofothermetalsmayinterfere.4.0APPARATUSANDMATERIALS4.1Atomicabsorptionspectrophotometer:Singleordualchannel,single-ordouble-beaminstrument,havingagratingmonochromator,photomultiplierd

4、etector,adjustableslits,andprovisionsforbackgroundcorrection.4.2Chromiumhollowcathodelamp.4.3Strip-chartrecorder(optional).5.0REAGENTS5.1ASTMTypeIIwater(ASTMD1193):Watershouldbemonitoredforimpurities.5.2Ammoniumpyrrolidinedithiocarbamate(APDC)solution:Dissolve1.0gAPDCinTypeIIwateranddiluteto100mL

5、.Preparefreshdaily.5.3Bromphenolblueindicatorsolution:Dissolve0.1gbromphenolbluein100mL50%ethanol.71971CD-ROMRevision0DateSeptember19865.4PotassiumdichromatestandardsolutionI(1.0mL=100ugCr):Dissolve0.2829gpuredriedpotassiumdichromate,K2Cr207,inTypeIIwateranddiluteto1,000mL.5.5Potassiumdichromates

6、tandardsolutionII(1.0mL=10.0ugCr):Dilute100mLchromiumstandardsolutionIto1literwithTypeIIwater.5.6PotassiumdichromatestandardsolutionIII(1.0mL=0.10ugCr):Dilute10.0mLchromiumstandardsolutionIIto1literwithTypeIIwater.5.7Methylisobutylketone(MIBK),analyticalreagentgrade:Avoidorredistillmaterialthatco

7、mesincontactwithmetalormetal-linedcaps.5.8Sodiumhydroxidesolution,1M:Dissolveto40gsodiumhydroxide,NaOH(ASCreagentgrade),inTypeIIwateranddiluteto1liter.5.9Sulfuricacid,0.12M:Slowlyadd6.5mLdistilledreagentgradeorspectrog