ABSTRACT
In classical mass spectrometry (MS), molecules are introduced into the ion source of the mass spectrometer, where they obtain an electrical charge, that is, are converted into ions. In the classical ionization mode (electron ionization; see Section 15.1.1), the ions formed include molecular ions (the charged molecules) and fragments, produced by decomposition of the molecular ions. ›e ions then enter the analyzer part of the mass spectrometer, where they are separated according to their masses. ›e common analyzers currently used for routine work are quadrupole and ion trap (magnetic analyzers, which had been commonly used in the early days of mass spectrometry, are employed today for special applications). ›eir description can be found in many textbooks (e.g., Chapman 1993, 9-16). Following their separation, the ions pass through a slit onto a detector, which is connected to a data acquisition system. ›e result is a “mass spectrum,” in which masses of dižerent ions are plotted against their relative abundances (more accurately, it is the mass/charge [m/z] ratio that is plotted, but since the charge is usually one electron, it is convenient to refer to “masses”; throughout this chapter, the notation m/z is used to note the masses of the ions).
