ASTM D5128-2009 在线测量低导电水pH的标准试验方法

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【英文标准名称】:StandardTestMethodforOn-LinepHMeasurementofWaterofLowConductivity
【原文标准名称】:在线测量低导电水pH的标准试验方法
【标准号】:ASTMD5128-2009
【标准状态】:现行
【国别】:美国
【发布日期】:2009
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:D19.03
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:highpurity;lowconductivity;on-line;pH;Acidity,alkalinity,pH--water;Automatedprocedures--wateranalysis;Calibration--wateranalysisinstrumentation;Conductanceandconductivity(electrical)--water;Fieldtesting--water;Low-conductivitywate
【摘要】:pHmeasurementsaretypicallymadeinsolutionsthatcontainrelativelylargeamountsofacid,base,ordissolvedsalts.Undertheseconditions,pHdeterminationsmaybemadequicklyandprecisely.Continuouson-linepHmeasurementsinwatersamplesoflowconductivityaremoredifficult(4,5).Theselowionicstrengthsolutionsaresusceptibletocontaminationfromtheatmosphere,samplestreamhardware,andthepHelectrodes.Variationsintheconstituentconcentrationoflowconductivitywaterscauseliquidjunctionpotentialshifts(see3.1.1)resultinginpHmeasurementerrors.Theaggressivenatureandthehighelectricalresistanceofpureandultra-pure,lowconductivitywatersmaydegradethepHmeasurementelectrodesresultinginunstableanddriftingpHoutputsignals.Itisessentialtomakeon-linepHmeasurementsoflowconductivitywaterasaccuratelyaspossibletodeterminethepropercontrolofpHadjustmentchemicals,theeffectivenessofdemineralizerequipment,theeventandnatureofimpuritycontaminationofthewater,andinformationpertainingtotheoverallstatusofthepurewatersystem.1.1Thistestmethodcoversthepreciseon-linedeterminationofpHinwatersamplesofconductivitylowerthan100x03BC;S/cm(seeTable1andTable2)overthepHrangeof3to11(seeFig.1),underfieldoperatingconditions,utilizingasealed,non-refillable,referenceelectrode.pHmeasurementsofwateroflowconductivityareproblematicalforconventionalpHelectrodes,methods,andrelatedmeasurementapparatus.1.2ThistestmethodincludestheproceduresandequipmentrequiredforthecontinuouspHmeasurementoflowconductivitywatersamplestreamsincludingtherequirementsforthecontrolofsamplestreampressure,flowrate,andtemperature.Foroff-linepHmeasurementsinlowconductivitysamples,refertoTestMethodD5464.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.TABLE1CalculatedConductivityandpHValuesat25x00B0;CofLowConcentrationsofNaOHinPureWaterANote18212;ThistabletabulatesthetheoreticalconductivityandpHvaluesoflowlevelsofNaOHinpurewaterascalculatedfromavailablethermodynamicdata.Note28212;ToillustratethehighsensitivityofthesamplepHattheselowconcentrationstocontaminants,thelastcolumnlistserrorsthatwouldresultifthesamplewerecontaminatedwithanadditional1mg/Lthroughsampleorequipmenthandlingerrors.SampleConcentration,mg/LSampleConductivity,x03BC;S/cmSamplepHx0394;pHErrorfromAdditional1mg/LNaOHContaminate0.001
0.055
7.05
x0394;2.35
0.010
0.082