Ions of different mass to charge (m/z) ratios are deflected to a different extent, resulting in a ‘sorting’ of ions by mass (virtually all ions have charges of z = +1, so sorting by the mass to charge ratio is the same thing as sorting by mass). ![]() This tube is curved, and the ions are deflected by a strong magnetic field. In the mass analyzer component, the positively charged fragments and any remaining unfragmented molecular ions are accelerated down a tube by an electric field. The neutral fragments are either adsorbed onto the walls of the chamber or are removed by a vacuum source. Because a great deal of energy is transferred by this bombardment process, the radical cation quickly begins to break up into smaller fragments, some of which are positively charged and some of which are neutral. In the ionization source, the sample molecule is bombarded by a high-energy electron beam, which has the effect of knocking a valence electron off of the molecule to form a radical cation. One of the more common types of MS techniques used in the organic laboratory is electron ionization. Next in line there is a mass analyzer, where the cationic fragments are separated according to their mass.įinally, there is a detector, which detects and quantifies the separated ions. In the figure below, some of the sample molecules remain whole, while others fragment into smaller pieces. Depending on the ionization method used, the ionized molecule may or may not break apart into a population of smaller fragments. First, there is an ionization source, where the molecule is given a positive electrical charge, either by removing an electron or by adding a proton. ![]() There are many different types of MS instruments, but they all have the same three essential components. The basics of a mass spectrometry experiment
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