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1、DISODIUMPYROPHOSPHATEPreparedatthe41stJECFA(1993),publishedinFNP52Add2(1993)supersedingspecificationspreparedatthe37thJECFA(1990),publishedinFNP52(1992).Metalsandarsenicspecificationsrevisedatthe55thJECFA(2000).AgroupMTDIof70mg/kgbw,asphosphorusfromallfoodsources,wa
2、sestablishedatthe26thJECFA(1982)SYNONYMSDisodiumdihydrogendiphosphate,disodiumdihydrogenpyrophosphate,acidsodiumpyrophosphate,INSNo.450(i)DEFINITIONChemicalnamesDisodiumdihydrogendiphosphate,disodiumdihydrogenpyrophosphateC.A.S.number7758-16-9ChemicalformulaNa2H2P2O
3、7Formulaweight221.94AssayNotlessthan95.0%DESCRIPTIONWhite,crystallinepowder,orgranulesFUNCTIONALUSESRaisingagent,bufferingagent,sequestrantCHARACTERISTICSIDENTIFICATIONSolubility(Vol.4)SolubleinwaterTestforphosphatePassestest(Vol.4)Testforsodium(Vol.4)PassestestpH(V
4、ol.4)3.7-5.0(1in100soln)PURITYLossondrying(Vol.4)oNotmorethan0.5%(105,4h)Water-insolublematterNotmorethan1%Dissolve10gofthesamplein100mlofhotwater,andfilterthroughataredofilteringcrucible.Washtheinsolubleresiduewithhotwater,dryat105for2h,coolandweigh.Fluoride(Vol.4)
5、Notmorethan10mg/kg(MethodIorIII)Arsenic(Vol.4)Notmorethan3mg/kg(MethodII)Lead(Vol.4)Notmorethan4mg/kgDetermineusinganatomicabsorptiontechniqueappropriatetothespecifiedlevel.Theselectionofsamplesizeandmethodofsamplepreparationmaybebasedontheprinciplesofthemethoddescr
6、ibedinVolume4,“InstrumentalMethods.”oMETHODOFWeighaccuratelyabout400mgofthesample,previouslydriedat105for4ASSAYh,anddissolvein100mlofwaterina400-mlbeaker.AdjustthepHofthesolutionto3.8withdilutehydrochloricacidTSorsodiumhydroxideTS,usingapHmeter,thenadd50mlofa1in8sol
7、utionofzincsulfate(125gofZnSO4·7H2Odissolvedinwater,dilutedto1000ml,filtered,andadjustedtopH3.8)andallowtostandfor2min.Titratetheliberatedacidwith0.1NsodiumhydroxideuntilapHof3.8isagainreached.Aftereachadditionofsodiumhydroxideneartotheend-point,timeshouldbeallowedf
8、oranyprecipitatedzinchydroxidetoredissolve.Eachmlof0.1Nsodiumhydroxideisequivalentto11.10mgofNa2H2P2O7.
