第八章质谱法

第八章质谱法MassSpectroscopy(MS)质谱仪的一般结构真空系统进样系统离子检测器数据系统质量分析器离子源大气样品机械泵，分子涡轮泵，扩散泵，离子泵，升华泵气体：气相色谱仪(GC/MS)液体：液相色谱仪(LC/MS)固体：固体进样杆(DIP,DCI)电子倍增器，多通道板检测器光电倍增管，阵列检测器通常的离子化方法电子轰击离子化EI化学电离离子化CI–正化学电离离子化PCI–负化学电离离子化NCI大气压力离子化API•电喷雾离子化ESI•大气压化学电离离子化APCIGC/MSLC/MS离子化方式分子量非极性极性EI/CIESIAPCI100,0001000离子化和碎片离子化硬无碎片有碎片APIEICI软质量分析器•四极杆–~80%的台式质谱仪(~3000/年)•HP,PE,TMQ,Shimadzu•离子阱–~20%的台式质谱仪(~700/年)•Varian,TMQ•飞行时间(ToF)–目前用户较少(50-60/年)•Leco,Micromass,TMQ•扇形磁场–通常不是台式仪器四极质量分析器++++离子阱原理与四极杆的非常相似，离子被存储在RF和DC场中，扫描场逐出精确m/z的离子。飞行时间质量分析器++++所有离子同时启动小的离子移动速度快测量已知距离下的速度(飞行时间)扇形磁场质量分析器++离子通过变化的磁场和电场被传输zmVBzemBVRBevRmvFZeVmvEk1442221ElectronImpactIonization(EI)e-e-e-e-e-SamplefromGCfilament++++FragmentionQPElectronImpactIonization(EI)•Thermalelectrons(ca.70eV)hitmoleculesandionizethem.•Amplefragmentions=amplestructuralinformationFingerprintEIspectrumMethylstearateM.W.298PositiveChemicalIonization(PCI)fromgascylinderfilamente-e-e-e-e-QPCH4CH5+C2H5+SamplefromGCH+-CH4[M+1]-C2H4PositiveChemicalIonization(PCI)•Reagentgasmoleculesareionizedfirst.Samplemoleculesareionizedmainlyby損rotontransfer?•Quasimolecularionseasilyproducedusefulformolecularweightverification.+PCIspectrumMethylstearateM.W.298ComparisonofEIandPCIEImodePCImodeFragmentMolecularweightNegativeChemicalIonization(NCI)•Negativeionformationbyelectroncapture–associativeresonancecapture–dissociativeresonancecapture–ion-pairproduction•Negativeionformationbyion-moleculereactions–protontransfer–chargeexchange–nucleophilicaddition–nucleophilicdisplacementNegativeionformationbyelectroncapture(associativeresonancecapture)•MX+e-(~0eV)MX-.X:positiveelectronaffinitypartCH4e-MXCH4+CH3+HCH4CH4CH4e-MX-质谱图的样子?EI和CI的质谱图50100150200250300350400450500550m/z0100%51051151250100150200250300350400450500550m/z0100%241213510242EIOOOCF3CF3CH3NCI…扫描50到300amu流入质谱仪的化合物质谱图...60801001201401601802002202402602803000100%240241断裂机理CH3C+CH3CH3CH2CH3CH3C+CH3CH3+CH2CH31.σ断裂2.α断裂RRY+RY+RRCH+CH2CH2CH2+R+CCH+RCH+CH2+3.i断裂RY+R1R++YR1CH3O+CH3CH3O+CH2+CH3CH3CH2+CH3O+αi4.逆Diels-Alder反应+。CH2+CH2+CH2CH25.Mclafferty重排OO+CH3HCH2CH2+OH+CH3OConfigurationofGCMSMassSpectrometerGasChromatographInterfaceIonsourceboxIonSourceDesign-Increasedionizationefficacy-InterfaceThesampleseparatedbyGCwillbeintroducedthroughthisinterface.FilamentIongeneratedbyfilamentwillgivetheelectronimpacttothesampletoproducethesampleionization.IonsourceboxIonLens-Highionintroductiontomassanalyzer-Thisionlensisfunctioningforeffectiveintroductiontomassanalyzer.OptimizationforadjustmentofthisionlenswillbedonebyPCautomatically.QuadrupoleRod-MinimizelossesintransittotheQuadrupole-MainRodSpecificiononlycanbepassedbytheelectronicfieldintoQuadrupoleRodwhichiscontrolledbyPC.PreRodFromionsourceTodetectorrotarypumpturbomolecularpump(151L/sec)turbomolecularpump(151L/sec)rotarypumpGoodvacuumsystem-MinimizelossesintransittotheQuadrupole-TurboMolecularPumpAircooledandoilfreeTurbomolecularPump(TMP)withlubricantimpregnatedceramicbearingsismaintenancefreeforupto25,000hours.Provideshighqualityvacuuminlessthan5mins.Iondetection+7.5kV-+e--0.7~3.0kVAMP-7.5KV+e--0.7~3.0kVAMPe-NegativeiondetectionPositiveiondetectionGCMS-QP5050ANCIsensitivity•200fgHexachlorbenzeneNCIspectrumMasschromatogramofm/z284OFN(octafluoronaphthalene)NCIscanmodeOutstandingHighSensitivityscanrangem/z60-310,0.5secinterval200fgS/N30GCMS-QP5050ANCIpesticidesdate310pgCyanophosNCImassspectrumphosphoruspesticides10pgComparisonbetweenEIandNCIextractfromcabbage(pesticidesadded)EIscanningmodeNCIscanningmodeComparisonbetweenEIandNCIextractfromcabbage(pesticidesadded)PrincipleofProgramedtemperaturevaporize(PTV)PTV100CsplitMS50-250CSolventwillbevaporizedandexhausted.Samplewillbeconcentrated.OptimizationofPTVconditions•Selectionofpackingmaterials–TenaxGC–20%OV-1–20%OV-17–20%Dexil300–ShincarbonA–CarbopackC•Traptemperature•Desorptiontemperature•TemperatureprogramVery-Large-VolumeInjectionusingPTVEffectofTemperatureonTrapefficiencyVery-Large-VolumeInjectionusingPTVTemperatureandSplitratioProgramVery-Large-VolumeInjectionusingPTV2ppbeachPesticidesinn-hexane1000uLInjection•AnalyticalConditionsGC17AVer.2DB130mX0.25mm50C(4)-160C-280C20C/min5C/minPTV70C(1)-100C(1)-280C30C/min250C/minWiderangeFTD1pA280CCarriergasHe150kPaPrecolumnTenaxGCFeaturesofGCMSQP-5050AOutstandinghighsensitivityExtendedmassrangeupto900amuVersatileMode-EI/PCI/NCI/DICompactDesignEasyOperationusingWindowsSoftwareEasytuning-PFTBAbuiltinstandardEasymaintenanceAnalysisofCoconutoilMSSpectrumofC48DIoptionThedirectinletoptionallowslessvolatileorthermallylabilesamplestobedirectlyintroducedintothemassspectrometer.MixturesofcompoundswhichhavedifferentboilingpointscanbepositivelyidentifiedbyprogrammingtheDIprobetemperature.ApplicationusingdirectinletprobeFront-openionchambersystem-easymaintenance-DualFilamentsSystem-easymaintenance-LCMS-QP8000Validation,ProductivityandMassDetectionWhatkindofbenefitsLC/MSuserscanget?•Powerfulqualitativecapability•SelectivequantitativecapabilityM/ZM/ZM/ZWhatkindofbenefitsLC/MSuserscanget?•Powerfulqualitativecapability•Selective