2023學(xué)年完整公開課版Determinationmethodofopticalrotation

PharmaceuticalanalysisDeterminationmethodofopticalrotationDeterminationmethodofopticalrotationAuthor:XuYingqianContentsSectionIOverviewSectionIIInstrumentanddeterminationmethodSectionIIIApplicationofpolarimetryKeyanddifficultpointsMasterFamiliarDeterminationmethodofopticalrotationandcalculationofspecificrotation.PolarimeteranditsapplicationmethodUnderstandApplicationofpolarimetrySectionIOverviewThestructureoforganiccompoundcontainschiralcarbonatomofopticalrotation.Theanalyticalmethodofdeterminingtheopticalrotationofmedicineforqualitative,impuritytestandquantitativeanalysisiscalledopticalrotationdetermination.Chiralcarbonatomsrefertocarbonatomsconnectedwithfourdifferentatomsorgroups,whichareoftenmarkedwith"*"1.Basicconcept(1)OpticalrotationWhenplanepolarizedlightpassesthroughliquidorsolutioncontainingsomeopticallyactivecompounds,itcancauseopticalrotation,whichmakestheplaneofpolarizedlightrotateleftorright.Thedegreeofrotationiscalledopticalrotation(expressedbyα).(2)SpecificrotationWhenplanepolarizedlightpassesthroughthesolutionwithalengthof1dmandcontaining1gofopticallyactivesubstanceper1ml,itsopticalrotationmeasuredatcertainwavelengthandtemperatureiscalledspecificrotation(expressedby).2.FactorsaffectingthedeterminationofopticalrotationOpticalrotationisnotonlyrelatedtochemicalstructure,butalsorelatedtosolutionconcentration,liquidlayerthickness,temperature,lightwavelengthandsolvent.DisDlineofsodiumspectrum;tisthetemperaturefordeterminationαismeasuredopticalrotation;Lislengthofdeterminationtube(dm)Cistheweightofthesubstancetobemeasuredin100mlsolution(g,basedondryoranhydrousmatter)2.Factorsaffectingthedeterminationofopticalrotation(1)ChemicalstructureofsubstanceDifferentchemicalstructuresofsubstanceleadtodifferentopticalactivity.Underthesameconditions,somerotationanglesarelarge,andsomerotationanglesaresmall;someareleft-handed("-")andsomeareright-handed("+"),andsomesubstanceshavenochiralcarbonatomsandnoopticalactivity.(2)Solutionconcentration①Thegreaterthesolutionconcentrationis,thegreatertheopticalrotationis;②Inacertainconcentrationrange,thereisalinearrelationshipbetweentheconcentrationofmedicinesolutionandtheopticalrotation;③Themeasurementofspecificrotationshouldbecarriedoutinacertainconcentrationofsolution.(3)SolventTheeffectofsolventonopticalrotationiscomplex,whichvarieswithsolventsandmedicines:somesolventshavenoeffectonmedicines,whileothersaffectthedirectionandmagnitudeofopticalrotation.Thenameofsolventshouldbemarkedwhendeterminingtheopticalrotationandspecificrotationofmedicine.(4)ThicknessoflightpassingthroughliquidlayerAsthethicknessoflightpassingthroughliquidlayerrises,theopticalrotationincreases.2.Factorsaffectingthedeterminationofopticalrotation(5)LightwavelengthTheshorterthewavelengthis,thegreatertheopticalrotationis.ChinesePharmacopoeia(2015)adoptsDline(589.3nm)ofsodiumspectrumtodeterminetheopticalrotation.(6)TemperatureIngeneral,theeffectcausedbythetemperatureisnotgreat.Formostsubstances,undertheyellowsodiumlight,whenthetemperaturerisesby1℃,thespecificrotationdecreasesbyabout1‰.SectionIIInstrumentanddeterminationmethod1.InstrumentChinesePharmacopoeia(2015)stipulatesthatacalibratedpolarimeterwithareadingof0.01°shouldbeusedCommonlyusedpolarimeter2.OperationmethodDeterminationofspecificrotation①Preparethetestsolutionandcompletedeterminationwithinthespecifiedtemperatureandstoragetime.Adjusttheroomtemperaturetothespecifiedtemperaturebeforedetermination.Usetheblanksolutionofthepreparedtestproducttocorrectormeasurethezeropoint,soastodeducttheblankreading,andthendeterminethetestproduct.②Theoperationmethodistowashthedeterminationtubeseveraltimeswiththetestproductorsolution,slowlyinjectaproperamountofthetestliquidorsolution,avoidbubbleswhenpouringliquid.Donotusetoomuchforcetoavoidstressanderrorwhentighteningthenutsonbothendsoftheopticalrotationtube.Placetheopticalrotationtubeintothepolarimetertodetectthereadingwhichistheopticalrotationoftestproduct.③Polarizedlightrotatingtoright(clockwise)iscalledright-handedrotation,whichisindicatedby"+";Polarizedlightrotatingtoleft(counterclockwise)iscalledleft-handedrotation,whichisindicatedby"-";Todeterminetheopticalrotation,repeatreadingfor3times,taketheaveragevalue,andcalculatetheresultaccordingtothespecifiedformula.2.OperationmethodCalculatethespecificrotation[α]oftestproductaccordingtothefollowingformulaForliquidtestproduct=α/l.dForsolidtestproduct=100α/ldwhere:[α]---specificrotationD---Dlineofsodiumspectrumt---temperaturefordeterminationl---lengthofdeterminationtube,dmα---measuredopticalrotation