Principes de la spectrométrie de masse

The mass spectrometry is an analysis method, which allows the molecular weight determination of compounds, their identification and quantification. It is based on the separation and the detection of ions appeared in the ion source or in a collision cell. These ions come from the molecule to analyze. In the case of soft ionization, ion is consecutive to the addition or the subtraction of an ion (such as H+) or an electron. This ion is called pseudomolecular ion or molecular ion and allows the molecular weight determination. In the case of hard ionization or in a collision cell, the molecular ions are fragmented to lead to the daughter ions. The fragmentations occur following well-known rules characteristic to the structure of compound to analyze. The variation of the ion intensity versus their m/z ratio is called the mass spectrum. For several years, mass spectrometry has been coupled with gas and liquid chromatography. The chromatographic behavior of the molecule brings another dimension in the molecule identification. The mass spectrometer coupled to a chromatograph works as a classical detector and gives for each peak an area proportional to the injected quantity of compound. However, it is essential to use an internal standard, generally the heavy standard.