Collisional activation mass spectra

Abstract

Collision with gas molecules can be used to add internal energy to gaseous ions in transit through a mass spectrometer, causing their subsequent unimolecular decomposition. Mass analysis of the resulting fragment ions produces a collisional activation mass spectrum whose utility is basically similar to that of a normal mass spectrum. Promising applications to date have been found in ion structure characterization for fundamental studies and molecular structure determination, for which the insensitivity of the collisional activation mass spectrum to the ion’s internal energy is a unique advantage; examples are given for structure determination of C ₇ H ₇ + and CSH ₃ + isomers. An additional application attracting increasing attention is as a separation/identification technique for complex mixtures; this involves mass spectrometric separation of the ionized mixture components followed by their identification from the corresponding collisional activation (or metastable ion) mass spectra. This two-dimensional mass spectrometry (‘m.s.-m.s.’) technique is complementary to g.c.-m.s. and liquid chromatography - mass spectrometry, and its use is illustrated by the determination of trace components in gasoline and the chirality of organophosphates.