EPA METHOD 9012B Total and Amenable Cyanide

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1、METHOD9012BTOTALANDAMENABLECYANIDE(AUTOMATEDCOLORIMETRIC,WITHOFF-LINEDISTILLATION)1.0SCOPEANDAPPLICATION1.1Thismethodisusedtodeterminetheconcentrationofinorganiccyanide(CASRegistryNumber57-12-5)inwastesorleachate.Thismethoddetectsinorganiccyanidesthatarepresentaseithersolublesaltsorcomplexes.I

2、tisusedtodeterminevaluesforbothtotalcyanideandcyanideamenabletochlorination.The"reactive"cyanidecontentofawasteisnotdeterminedbythismethod.Referto40CFR261.23forinformationonthecharacteristicofreactivity.2.0SUMMARYOFMETHOD2.1Thecyanide,ashydrocyanicacid(HCN),isreleasedfromsamplescontainingcyani

3、debymeansofareflux-distillationoperationunderacidicconditionsandabsorbedinascrubbercontainingsodiumhydroxidesolution.ThecyanideionintheabsorbingsolutionisthendeterminedbyautomatedUVcolorimetry.2.2Intheautomatedcolorimetricmeasurement,thecyanideisconvertedtocyanogenchloride(CNCl)byreactionwithC

4、hloramine-TatapHlessthan8withouthydrolyzingtothecyanate.Afterthereactioniscomplete,colorisformedontheadditionofpyridine-barbituricacidreagent.TheconcentrationofNaOHmustbethesameinthestandards,thescrubbersolutions,andanydilutionoftheoriginalscrubbersolutiontoobtaincolorsofcomparableintensity.3.

5、0INTERFERENCES3.1Interferencesareeliminatedorreducedbyusingthedistillationprocedure.Chlorineandsulfideareinterferencesinthismethod.3.2Oxidizingagentssuchaschlorinedecomposemostcyanides.Chlorineinterferencescanberemovedbyaddinganexcessofsodiumarsenitetothewastepriortopreservationandstorageofthe

6、sampletoreducethechlorinetochloridewhichdoesnotinterfere.3.3Sulfideinterferencecanberemovedbyaddinganexcessofbismuthnitratetothewaste(toprecipitatethesulfide)beforedistillation.Samplesthatcontainhydrogensulfide,metalsulfides,orothercompoundsthatmayproducehydrogensulfideduringthedistillationsho

7、uldbetreatedbytheadditionofbismuthnitrate.3.4Highresultsmaybeobtainedforsamplesthatcontainnitrateand/ornitrite.Duringthedistillation,nitrateandnitritewillformnitrousacid,whichwillreactwithsomeorganiccompoundstoformoximes.Thesecompoundso