有机波谱分析双语课件 (7).pdf

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1、质谱仪 II 有机波谱分析 Organic Spectroscopic Analysis Mass Spectrometer II SCUEC(Li TC)2 Components of MS(III):Mass Analyzers 1.Magnetic sector 2.Quadrupole MS filter 3.Time-of-Flight 4.Ion trap analyzers 5.FT-MS 6.MS/MS(Tandem MS)MS Analyzer 3 Magnetic Sector:Double Focusing Molecular weight to 4 decimals,R

2、esolution 60,000 MS Analyzer 4 Quadrupole Mass Analyzer Uses a combination of RF and DC voltages to operate as a mass filter.Has four parallel metal rods.Lets one mass pass through at a time.MS Analyzer 5 Quadrupole Mass Analyzer+Ions scanned by varying the DC/RF voltages across the quadrupole rods

3、Compact,Inexpensive GC/MS MS Analyzer 6 Ion Trap MS Analyzer 7 Time-of-Fight(TOF)Measure the time it takes an ion to travel a specific distance.The ion is initially accelerated by a high potential 20-30kV,different mass ions will be accelerated into the analyser with initial velocities proportional

4、to their masses and subsequently arrive at the detector at different times.+Source Drift region(flight tube)detector V MS Analyzer MALDI-TOF-MS MALDI ionization,Time-of-flight Mass Spectrometer MS Analyzer 10 Fourier Transform Ion Cyclotron Resonance(FT-ICR)-Very High Precision most expensive Ion as

5、sumes a circular orbit in a B-field,frequency v/r (m/q)-1 When excited with RF with the characteristic frequency,ions absorb energy,v,but unchanged,thus r.MS Analyzer SCUEC(Li TC)11 FT-ICR MS Analyzer Resolution for the m/z 131 peak of perfluorotributylamine(PFTBA)can reach 1 million using FT-ICR.(m

6、0.00012 Da)FWHH(000,090,100012.0131mmR The resolving power decreases linearly with increasing mass,a drop to m/m=10000 can be expected for an ion of m/z 100,000.MS Analyzer SCUEC(Li TC)13 MS/MS(Tandem Mass Spectrometry)1.Ions are separated in the first MS 2.Specific ions(parent ions)pass one at a ti

7、me in a field-free collision chamber 3.Collisions with He result in Daughter Ions 4.Second MS produces mass spectrum of each parent ion in the first MS.MS Analyzer Quadrupole/Quadrupole Tandem-MS 1st Quadrupole:select specific parent ion 2nd Quadrupole(RF only,no DC):collision induced decomposition

8、3rd Quadrupole:separation spectrum of daughter ions Quadrupole-Quadupole Tandem-MS MS Analyzer 15 Features of Different Mass Analyzers m/z range resolution sensitivity Price Magnetic Sector 15,000 0.0001(double focusing)Low High Quadrupole 5,000 1 High Low Ion Trap 5,000 1 High Low Time of Flight no limit 0.0001 High FT-ICR 70,000 0.0001 High High MS Analyzer