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1、CALCIUMDISODIUMETHYLENEDIAMINETETRAACETATEPreparedatthe30thJECFA(1986),publishedinFNP37(1986)andinFNP52(1992).Metalsandarsenicspecificationsrevisedatthe61stJECFA(2003).AnADIof0-2.5mg/kgbwwasestablishedatthe17thJECFA(1973)SYNONYMSCalciumdisodiumEDTA,calc
2、iumdisodiumedetate;INSNo.385DEFINITIONChemicalnamesN,N'-1,2-Ethanediylbis[N-(carboxymethyl)-glycinate](4-)-NNN,N',O,O',O,O]calciate(2-)disodium;Calciumdisodiumethylenediaminetetraacetate;Calciumdisodium(ethylene-dinitrilo)-tetraacetate.C.A.S.number662-3
3、3-9ChemicalformulaC10H12CaN2Na2O8·2H2OStructuralformulaFormulaweight410.31AssayNotlessthan97%andnotmorethantheequivalentof102%calculatedontheanhydrousbasisDESCRIPTIONWhite,odourlesscrystallinegranulesorawhitetonearlywhitepowder;slightlyhygroscopicFUNCTI
4、ONALUSESSequestrant,preservativeCHARACTERISTICSIDENTIFICATIONSolubility(Vol.4)Freelysolubleinwater,practicallyinsolubleinethanol.Testforcalcium(Vol.4)PassestestTestforsodium(Vol.4)PassestestChelatingactivitytometalTo5mlofwaterinatesttubeadd2dropsofammon
5、iumthiocyanateTSandions2dropsofferricchlorideTS.Adeepredsolutiondevelops.Addabout50mgofthesampleandmix.Thedeepredcolourdisappears.PURITYpH(Vol.4)6.5-7.5(1in100soln).MagnesiumchelatingTransfer1gofthesample,accuratelyweighed,toasmallbeaker,andsubstancesdi
6、ssolveitin5mlofwater.Add5mlofbuffersolutionpreparedbydissolving67.5gofammoniumchloridein200mlofwater,adding570mlofstrongammoniaTS,anddilutingwithwaterto1000ml.Tothebufferedsolutionadd5dropsoferiochromeblackTS,andtitratewith0.1Mmagnesiumacetatetotheappea
7、ranceofadeepwine-redcolour.Notmorethan2.0mlshouldberequired.Lead(Vol.4)Notmorethan2mg/kgDetermineusinganatomicabsorptiontechniqueappropriatetothespecifiedlevel.Theselectionofsamplesizeandmethodofsamplepreparationmaybebasedontheprinciplesofthemethoddescr
8、ibedinVolume4,“InstrumentalMethods.”METHODOFASSAYTransferabout1.2gofthesample,accuratelyweighed,intoa250-mlbeaker,anddissolvein75mlofwater.Add25mlofdiluteaceticacidTSand1.0mlofdiphenylcarbazonesolution(1gin100mlethanol).Titratesl