Organic Mass Spectrometry Analyzers and MS-MS or MSn methods

If we focus on a field of application dedicated to molecular analysis, it is possible to consider that mass spectrometry possesses a specific characteristic that distinguishes it from spectroscopic methods of analysis involving the absorption of radiation in the microwave, infrared (IR) [P 2 845] , ultraviolet (UV) or nuclear magnetic resonance (NMR) context [P 1 092] . These techniques for identifying molecules or quantifying their presence in a given medium are physical measurement methods. They are based on the principle of temporarily modifying the properties of the chemical bodies under study, with the absorption (or scattering for the Raman effect [P 2 865] ) of energy leading to the formation of an excited state of part or all of the molecule. The principle of these spectroscopic analysis techniques is then to measure the energy absorbed or restituted after the excited species returns to a more energetically stable state, which may be the initial state. In mass spectrometry, the measurement consists of obtaining the m/z value of a charged chemical entity by linking the operating parameters of a part of the system, called the analyzer, to the ion's molecular mass and charge characteristics. But, unlike the spectroscopic analysis techniques referred to above, mass spectrometry is best understood as a method requiring the chemical creation of new bodies (by ionization of molecules or charge separation of a salt) in addition to physical measurements, because it involves a step of producing charged species (by ionization reactions) before separating them and measuring their m/z ratio. The description of the chemical ionization step is the subject of an article dedicated to this process [P 2 645] . This article focuses on the two...