Mass spectrometry has become a very important tool for the inorganic chemist, having been extensively applied particularly in the fields of organometallic and coordination chemistry. However, for the inorganic chemist dealing with ionic materials, thermally labile systems, or polymeric systems not readily volatilized in the “organic” mass spectrometer, mass spectrometry remained a dream for a long time. The exceptions were those with access to “inorganic” mass spectrometers, with thermionic and spark sources, designed primarily for elemental analysis or isotope ratio determination and the surface scientists with access to secondary ion mass spectrometers (SIMS), ion microprobes, and related devices. Most of these were low mass, low-resolution devices, not particularly adaptable to the problems of the inorganic chemist, i.e., problems analogous to those for which the organic chemists have so widely applied mass spectrometry. In addition, there was the widely held belief that SIMS was only applicable to conducting samples and that surface charging effects precluded application to neutral molecules. Early attempts at molecular SIMS suggested that the sample lifetime would also be exceedingly short.
This article deals primarily with fast-atom bombardment (FAB) mass spectrometry. It is basically an outgrowth of SIMS, except that it uses an energetic beam of fast neutral atoms of an inert gas, rather than 2- to 8-keV ions, as the means of sputtering charged species from a surface. This technique, which was readily adapted to high-mass, high-resolution (organic) mass spectrometers, together with the discovery that dissolving the sample in a matrix liquid, such as glycerol, gave long-lived signals, burst onto the mass spectrometry scene in 1980-1981 -initially finding its greatest application to biological molecules that were polar and thermally labile. However, from the earliest papers on FAB, the inorganic applications were apparent. Since FAB mass spectra were able to show a parent quasi-molecular ion for vitamin B12 (mlz 1355) and its coenzyme (mlz 1579), almost everyone with early access to the technique tried these cobalamins as ideal model compounds. The observation of vitamin B12 by mass spectrometry has been described as a “milestone”. Many people, myself included, saw or used commercial prototype FAB sources before the first paper on the subject appeared in print.