波谱分析课件 chapter 5 MS

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1、Chapter5MassSpectrometryMassSpectrometryBasicsWhatinformationcanbedetermined?MolecularweightMolecularformula(HRMS)Structure(fromfragmentationfingerprint)Isotopicincorporation/distributionProteinsequence(MS-MS)MassSpectrometryBasicsMassspectrometryhas4basicoperations:Sampleintroduction(analytemustb

2、einvaporphase)IonizationMassanalysis(separatingionsbymass/chargeratio)DetectionandquantitationSampleIntroductionMethodApplicationsBatch(reservoir)gases,volatileliquidsDirectinsertionprobeverylowvaporpressuresolidsandliquidsMembraneaqueoussolutions,airsamplesChromatographyeluentLC-MS,GC-MS,etc.Ioni

3、zationMethods1.ElectronIonization(EI)mostcommonionizationtechnique,limitedtorelativelylowMWcompounds(<600amu)2.ChemicalIonization(CI)ionizationwithverylittlefragmentation,stillforlowMWcompounds(<800amu)3.DesorptionIonization(DI)forhigherMWorverylabilecompounds4.Sprayionization(SI)forLC-MS,biomolec

4、ules,etc.ElectronIonization(EI)vaporizedsampleisbombardedwithhighenergyelectrons(typically70eV)“hard”ionizationmethodleadstosignificantfragmentationionizationisefficientbutnon-selectivePLKChapter8iswrittenfromanEIMSperspectiveElectronIonizationAdvantagesinexpensive,versatileandreproduciblefragment

5、ationgivesstructuralinformationlargedatabasesifEIspectraexistandaresearchableDisadvantagesfragmentationatexpenseofmolecularionsamplemustberelativelyvolatileChemicalIonization(CI)Vaporizedsamplereactswithpre-ionizedreagentgasviaprotontransfer,chargeexchange,electroncapture,adductformation,etc.commo

6、nCIreagents:methane,ammonia,isobutane,hydrogen,methanol“soft”ionizationgiveslittlefragmentationselectiveionization--onlyexothermicorthermoneutralion-moleculereactionswilloccurchoiceofreagentallowstuningofionizationDesorptionIonization(DI)Allowsanalysisofnon-volatileorthermallylabilematerialsSample

7、hitwithlargeamountofenergyinshorttimeSecondaryionmassspectrometry(SIMS)Fastatombombardment(FAB)Plasmadesorption(PD)Laserdesorption(LD)Matrix-assistedlaserdesorption(MALDI)SIMSandFABSampleinsolidorliquidmatrixbomb