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1、ElectrosprayIonizationMassSpectrometryJessicaGilmanCourtneyMashburn17September2002Chemistry5181“ManyuserstendtoviewESIasa‘BlackBox,’becausesourcesofinstability,background,interference,competition,andsuppressionarenotalwaysunderstood.”1OutlinelIntroductionlIoni
2、zationProcesslIntroductionofIonsintoMSlOperationalConditionsandParameterslSolventandAnalyteCharacteristicslSensitivityandDetectionLimitslTandemTechniqueslSummaryIntroductionlESIallowsforlarge,non-volatilemoleculestobeanalyzeddirectlyfromtheliquidphaselUsedfor:
3、lMassdeterminationofbiomoleculeslAnalysisandsequencingofproteinsandoligonucleotideslAnalyzingdrugs,pesticides,andcarbohydrateslLongchainfattyacids2ElectrosprayIonizationChamberAPI-Electrosprayoccursat760torrProducts=neutrals,ions,andclustersofionsIonizationMec
4、hanismslCoulombFission:lAssumesthattheincreasedchargedensity,duetosolventevaporation,causeslargedropletstodivideintosmallerdropletseventuallyleadingtosingleions.lIonEvaporation:lAssumestheincreasedchargedensitythatresultsfromsolventevaporationcausesCoulombicre
5、pulsiontoovercometheliquid’ssurfacetension,resultinginareleaseofionsfromdropletsurfaces3ChargingtheAnalytelChargeSeparationlAdductFormationlGas-phaseionsareformedlPolarmoleculesthatdonotwhenthedropletsfromthehaveacidicorbasicgroupsTaylorConeevaporateandcanbech
6、argedthroughtheionscarryingexcessformationofadductswithchargearereleasedintothevariousions.gas-phase.lNegativeionESI:formadductswithCl-ionslPositiveionESI:formadductswithNa+,Li+,NH4+,orothercationicspecieslProblem:High[salt]causesbackgroundinterference.Chargin
7、gtheAnalyte,Cont’dlGas-PhaseReactions:lElectrochemRedoxRxns:lIonizedatatmosphericl“Thecontinuousflowofpressure.chargefromthemetalliclGenerallythroughgas-contacttothesamplephaseprotontransfer.solutionmustoccurviaanelectrochemicalreactionatlProtongoestospeciesth
8、atcontact.”withhighergas-phaseprotonaffinitylPositiveionESI:oxidationlAnalytemusthavelNegativeionESI:reductionhigherprotonaffinitythanthesolvent.4Pneumatically-AssistedESIlMustsepa
