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1、9/9USP35<231>HEAVYMETALS<231>重金属Thistestisprovidedtodemonstratethatthecontentofmetallicimpuritiesthatarecoloredbysulfideion,underthespecifiedtestconditions,doesnotexceedtheHeavymetalslimitspecifiedintheindividualmonographinpercentage(byweight)ofleadinthetestsubstance,asdeterminedbyconcomitantvisualc
2、omparison(seeVisualComparisoninthesectionProcedureunderSpectrophotometryandLight-Scattering851)withacontrolpreparedfromaStandardLeadSolution.[NOTE—Substancesthattypicallywillrespondtothistestarelead,mercury,bismuth,arsenic,antimony,tin,cadmium,silver,copper,andmolybdenum.]本检验用以证实供试品中与硫离子作用显色的金属杂质含量，
3、在规定检验条件下，不超过个论中规定的供试品重金属限度，以铅百分含量（重量比）计，与用标准铅溶液配制的对照进行目测比较（参看分光光度法和光散射法<851>中操作步骤部分的视觉比较）测定。[注意：与本检验起反应的代表性物质为铅、汞、铋、砷、锑、锡、镉、银、铜和钼。]DeterminetheamountofheavymetalsbyMethodI,unlessotherwisespecifiedintheindividualmonograph.MethodIisusedforsubstancesthatyieldclear,colorlesspreparationsunderthespecified
4、testconditions.MethodIIisusedforsubstancesthatdonotyieldclear,colorlesspreparationsunderthetestconditionsspecifiedforMethodI,orforsubstancesthat,byvirtueoftheircomplexnature,interferewiththeprecipitationofmetalsbysulfideion,orforfixedandvolatileoils.MethodIII,awet-digestionmethod,isusedonlyinthoseca
5、seswhereneitherMethodInorMethodIIcanbeused.除个论另有规定外，用方法I测定重金属含量。方法I用于规定条件下可生成无色的、透明的制品的物质。方法II适用于在方法I规定条件下无法生成无色透明制9/9品的物质，或由于自身复杂特性，会对硫离子生成的金属沉淀造成干扰的物质，以及不挥发油和挥发油。方法III湿消化法，仅在方法I和方法II均不适用时使用。SpecialReagents专用试剂LeadNitrateStockSolution—Dissolve159.8mgofleadnitratein100mLofwatertowhichhasbeenadded1mL
6、ofnitricacid,thendilutewithwaterto1000mL.Prepareandstorethissolutioninglasscontainersfreefromsolubleleadsalts.硝酸铅贮备液：取硝酸铅159.8mg，加已加硝酸1mL的水100mL，溶解，加水稀释至1000mL。于不含可溶铅盐的玻璃容器中配制和贮存该溶液。StandardLeadSolution—Onthedayofuse,dilute10.0mLofLeadNitrateStockSolutionwithwaterto100.0mL.EachmLofStandardLeadSoluti
7、oncontainstheequivalentof10µgoflead.Acomparisonsolutionpreparedonthebasisof100µLofStandardLeadSolutionpergofsubstancebeingtestedcontainstheequivalentof1partofleadpermillionpartsofsubstancebeingtested.
