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1、WuhanInstituteofTechnology13.DeterminationofironbyPhenanthrolinephotometricmethodⅠ.PrincipleAbserptionspectrophotometricdeterminationoftraceironisoneofthecommonlyusedmethod.AtpH=1.5~9.5undertheconditions,Fe2+ionandphenanthroline(Phen)generatedverystableorange-redcomplexwithFe(Phen)32+: Sta
2、bilityofthiscomplexlgK=21.3,molarabsorptioncoefficientε=1.1×104L/mol•cm.HaircolorbeforethefirstuseofhydroxylaminehydrochloridetoFe3+ionsreducedtoFe2+ions,thereactionisasfollows: 4Fe3++2NH2OH=4Fe2++N2O+H2O+4H+Determination,thecontrolsolutionacidityismoreappropriateinthepH=3-9wit
3、hhighacidity,thereactionisslow;acidityistoolowthenthehydrolysisofFe3+ionsaffectthecolor.Bi3+,Cd2+,Hg2+,Ag+,Zn2+andotherionswiththereagentgeneratedprecipitation,Ca2+,Cu2+,Ni2+andotherionsformacolorcomplex,sowhentheseionscoexist,itshouldbenotedtheirinterference.Ⅱ.theinstrumentsandreagents1.U
4、V-2100spectrophotometer,50mLvolumetricflaskof8；2.Ironstandardsolution(100μg/mL)；3.Ironstandardsolution(10μg/mL)；4.Phenanthroline(1.5g/L)；5.Hydroxylaminehydrochloride(100g/L)；6.NaAc(1mol/L)；7.NaOH(1mol/L)；8.HCl(6mol/L)；9.Ironsampletestsolution.Ⅲ.procedures1.Absorptioncurveofproductionandthe
5、choiceofmeasurementwavelengthWuhanInstituteofTechnologyLessonswithapipette0.0mLand1.0mLironstandardsolution(100μg/mL)wereinjectedintotwo50mLvolumetricflask,add1mLofthehydroxylaminehydrochloridesolution,shakewell.Thenadd2mLPhen,5mLNaAc,dilutedwithwatertothemark,shakewell.10minafterplacement
6、,withthe1cmcuvettetoreagentblank(ie,0.0mLironstandardsolution)asreferencesolution,betweenthe470-560nm,measuredonceevery10nmabsorbanceA,atthemaximumabsorptionpeaknearmeasuredonceevery2nmA.Inthegraphpaperatthewavelengthλisthehorizontalaxis,theabsorbanceAfortheverticalaxis,drawthecurveofthere
7、lationshipbetweenAandλ,theabsorptioncurve.Absorptioncurveobtainedfromthemaximumabsorptionwavelengthλmax,DeterminationofFeandasappropriatewavelength.Instrumentspecificoperationisasfollows:2.Workingcurve(standardcurve)productionIronstandardsolutionswerePipette(1
