ABSTRACT
The source of a mass spectrometer is where the gaseous ions are produced from the introduced molecules. The nature of the used source depends on the physical state of the substance to be analyzed.1 One can therefore use an ionization-desorption source when the analyte is a solid substance and an ionization-desolvation source when it is a liquid.2-5 In coupling with a gas chromatograph in which the eluted compounds arrive into the mass spectrometer in gaseous form, the sources that are used are said to be in electron ionization (EI) or chemical ionization (CI).6,7 Their use is reserved for the analysis of gaseous or easily volatizable compounds (boiling points not exceeding 400°C). The source is maintained at a high temperature (generally ranging from 100 to 250°C) to avoid the condensation of the analytes. The boiling points and sublimation points of the analytes are, however, much lower under secondary vacuum than under atmospheric pressure.
