Principle : Mass spectrometry is an analytical technique which allows the determination of molecular masses of compounds analyzed as well as their identification and quantification.
This technique is based on the separation and detection of ions formed in an ionization source or in a collision chamber. these ions originate from the molecule to analyze. in the case of ionization methods, so-called » soft « , the molecular ion or pseudomoléculaire formed can be attributed to the addition of an ion (h+) or the subtraction of an electron to the molecule. in the case of ionization methods, less sweet, or in a collision chamber, ions to pseudo-molecular or molecular fragment to give ions son by following the rules of fragmentation are known, and characteristics of the structures of the molecules to be analyzed. it is therefore possible, with this method, to obtain structural information. the graph representing the intensity of the ions according to their m/z ratio is called the mass spectrum.
The mass spectrometer consists of several parts, arranged in series, for successively : the introduction of the sample ; the evaporation and ionization of molecules in an element called source (conversion of molecules to the natural state of ions in the gaseous state) ; the acceleration of the ions formed ; the separation of these ions in an element called mass analyzer according to their m/z ratio (mass to charge) ; the detection, that is to say the obtaining of the mass spectrum.
For several years, the mass spectrometry is coupled to methods of separating, such as chromatography in the gas phase and in the liquid phase. the mass spectrometer functions as a detector classic by giving an answer, the area of the chromatographic peak, proportional to the amount of product injected. however, in quantitative studies, it is essential to use an internal standard, preferably similar to the heavy (labeled with c13 or d2) of the product to be analyzed and which has the same retention time in chromatography.