EPA METHOD 9040C pH Electrometric Measurement

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1、METHOD9040CpHELECTROMETRICMEASUREMENT1.0SCOPEANDAPPLICATION1.1ThismethodisusedtomeasurethepHofaqueouswastesandthosemultiphasewasteswheretheaqueousphaseconstitutesatleast20%ofthetotalvolumeofthewaste.1.2Thecorrosivityofconcentratedacidsandbases,orofconcentratedacidsandbasesmixedwithinertsubsta

2、nces,cannotbemeasured.ThepHmeasurementrequiressomewatercontent.2.0SUMMARY2.1ThepHofthesampleisdeterminedelectrometricallyusingeitheraglasselectrodeincombinationwithareferencepotentialoracombinationelectrode.ThemeasuringdeviceiscalibratedusingaseriesofstandardsolutionsofknownpH.3.0INTERFERENCE

3、S3.1Theglasselectrode,ingeneral,isnotsubjecttosolutioninterferencesfromcolor,turbidity,colloidalmatter,oxidants,reductants,ormoderate(<0.1molarsolution)salinity.3.2SodiumerroratpHlevels>10canbereducedoreliminatedbyusingalow-sodium-errorelectrode.3.3Coatingsofoilymaterialorparticulatemattercan

4、impairelectroderesponse.Thesecoatingscanusuallyberemovedbygentlewipingordetergentwashing,followedbyrinsingwithdistilledwater.Anadditionaltreatmentwithhydrochloricacid(1:10)maybenecessarytoremoveanyremainingfilm.3.4TemperatureeffectsontheelectrometricdeterminationofpHarisefromtwosources.Thefir

5、stiscausedbythechangeinelectrodeoutputatvarioustemperatures.Thisinterferenceshouldbecontrolledwithinstrumentshavingtemperaturecompensationorbycalibratingtheelectrode-instrumentsystematthetemperatureofthesamples.ThesecondsourceoftemperatureeffectsisthechangeofpHduetochangesinthesampleasthetemp

6、eraturechanges.Thiserrorissample-dependentandcannotbecontrolled.Itshould,therefore,benotedbyreportingboththepHandtemperatureatthetimeofanalysis.4.0APPARATUSANDMATERIALS4.1pHmeter--Laboratoryorfieldmodel.Manyinstrumentsarecommerciallyavailablewithvariousspecificationsandoptionalequipment.4.2Gl

7、asselectrode.4.3Referenceelectrode--Asilver-silverchlorideorotherreferenceelectrodeofconstantpotentialmaybeused.9040C-1Revision3November2004NOTE:Combinationelectrodesincorporatingbothmeasuringandreferencedfunctionsareconvenienttouseandareavai