UTILITY OF EXACT MASS MEASUREMENTS

This chapter discusses utility of exact mass measurements. High-resolution mass spectrometry and exact mass measurement have been synonymous with the determination of elemental composition of an organic compound or a fragment ion ever since Beynon, in the early 1960s, demonstrated the practical utility of these techniques. By precisely measuring (to about 1–10 ppm) the relative ratio of the accelerating voltages required to focus, at fixed magnetic field, an ion of unknown mass and a reference ion onto the collector slit of a double-focusing mass spectrometer, it is possible to measure the m/z value of the unknown ion with an accuracy that permits the calculation of its elemental composition. Such measurements serve a variety of purposes: the elucidation of fragmentation pathways of compounds of known structures; the determination of the elemental composition of synthetic compounds in lieu of combustion analysis; the determination of the structure of natural products; etc. Both the information content of an exact mass measurement and the experimental difficulties in obtaining the data, change dramatically as the mass of the molecule or the fragment increases. © 1990, Elsevier Inc. All rights reserved.