Components of a Mass Spectrometer

Transcription

1 Components of a Mass Spectrometer Sample Introduction Inlet GC LC Direct Insertion (Syringe/Probe) Ionization Ion Separation Ion Detection Ion Source EI,CI,,, MALDI Mass Analyzer Under vacuum TOF, Quadrupole, Ion Trap Detector Electron Multiplier, Multi-Channel Plate Data System Relative Abundance; 100 % Mass Spectrum m/z Data Output 72

2 Summary of Mass Spectrometers Ion Source Ionization Technique Mass Analyzer Mass Range / gmol -1 Resolution Location Training Available Agilent GC-MSD HP5975 EI Hard Quadrupole < 800 Low SB 134 Yes Agilent GC-MSD HP5973N EI Hard Quadrupole < 800 Low SA 219 Yes Agilent Q-TOF 6520 Bruker Esquire 3000 Waters GC-TOF Premier Thermo Finnegan SSQ 7000 EI CI EI CI Hard Hard Quadrupole-TOF < 65,000 < 1500 Quadrupole-Ion Trap < 2000 < 2000 High SB 134 No Low SB 132 No TOF < 800 High SB 134 No Quadrupole < 800 Low SB 038 No Bruker MALDI-TOF MALDI TOF < 30,000 High SB 034 No

3 High-Resolution Electron Impact/Chemical Ionization using Waters GC-TOF Works best for neutral small molecule organics (MW < 1000 gmol -1 ; most success < 600 gmol -1 ). Must be volatile without decomposition. Submit neat samples (no solvent); need ~1 mg, but larger quantities (10 20 mg) are easier to work with to allow for repeat analyses. 99+% of samples submitted are run under EI conditions; CI used for confirmation if molecular ion very weak or absent. Electron Impact (EI): Hard Ionization Technique; formation of molecular ion (M + ), followed by fragmentation. MM + ee MM + + 2ee MM + AA + BB Chemical Ionization (CI): Ionization Technique; reagent gas, e.g., CH 4 or NH 3, forms adduct ions with sample, little fragmentation. + NNNN 3 NNNN 3 NNNN NNNN 3 NNNN NNNN 2 MM + NNNN 4 + MMMM + + NNNN 3 MM + NNNN 4 + (MMNNNN 4 ) + Example of Methyl Stearate

4 High-Resolution Electrospray Ionization () and Atmospheric Pressure Chemical Ionization () using Agilent Q-TOF is a soft ionization technique. -MS works best for polar samples that can dissolve in solvents such as water, methanol, acetonitrile or chloroform. Compounds containing easily protonated functional groups, such as alcohols, amines, ethers, carbonyls or thiols, or deprotonated, such as carboxylic acids, are good candidates for -MS. Organometallic complexes with labile charged ligands and ionic compounds are also suitably ionized by -MS. Sample quantity of mg is required for analysis; submit either neat or in solution. Mass Range for is ,000 gmol -1. is a soft ionization technique. -MS is suitable for less polar molecules which are only soluble in less polar solvents such as benzene, toluene, tetrahydrofuran and dichloromethane. -MS can also be useful for organometallic complexes that do not ionize suitably by. Sample quantity of mg is required for analysis; submit either neat or in solution. Mass Range for is gmol -1. For both and, samples in solution are injected through a nebulizer, either directly via a syringe or using HPLC if separation is required.

5 Bruker Autoflex III Smartbeam MALDI-TOF Best for compounds with functional groups ionization technique Mass ranges: Da, high resolution (Reflector Detector) ,000 Da, low resolution (Linear Detector) Sample can be submitted in any forms: solid (preferred) or solution Matrix Laser (Matrix) + (Matrix) + Sample (Sample + H)