Mass spectrometry: Instrumental aspect-The source

Abstract

The authors have discussed the analyzer part under instrumental aspect. A mass spectrometer has several vital sections but the source and the analyzer are the two parameters, which dictates the design of other sections. One can interface different type of source with an analyzer or a same type of source with different type of analyzer. Invariably it is the nature of the sample to be analyzed determines the choice of the source. There are several types of sources like the Electron-Impact (EI), Chemical Ionization (CI), Field Ionization (FI), Field Desorption (FD), Secondary ion/Fast atom bombardment (SIMS/FAB), and used for combined gas chromatography-mass spectrometry beam to monitor a GC-MS run. Some basic similarity can be found in each type of mass spectrometer sources. They are the sample evaporation followed by ionization and subsequent passing out of the source area by these ionized particles as a beam to analyzer. Normally, the source and the analyzer both have separate pumping system to create vacuum. This creates a total non-dependence of the mean free path in the analyzer of the ion source pressure.