Dynamic fast-atom bombardment technique

This method is still in use but is not described in this book because it has been superseded by more recent developments, such as particle beam and electrospray. These newer techniques have no moving parts, are quite robust, and can handle a wide variety of compound types. Chapters 8 through 13 describe these newer ionization techniques, including electrospray, atmospheric pressure ionization, plasmaspray, thermospray, dynamic fast-atom bombardment (FAB), and particle beam. 

To achieve sufficient vapor pressure for El and Cl, a nonvolatile liquid will have to be heated strongly, but this heating may lead to its thermal degradation. If thermal instability is a problem, then inlet/ionization systems need to be considered, since these do not require prevolatilization of the sample before mass spectrometric analysis. This problem has led to the development of inlet/ionization systems that can operate at atmospheric pressure and ambient temperatures. Successive developments have led to the introduction of techniques such as fast-atom bombardment (FAB), fast-ion bombardment (FIB), dynamic FAB, thermospray, plasmaspray, electrospray, and APCI. Only the last two techniques are in common use. Further aspects of liquids in their role as solvents for samples are considered below. 

On-line MS methods enable continuous kinetic profiles to be obtained but they cannot easily accommodate complex sample preparation steps. In the 1980s, enzymatic reactions were monitored by a popular - at that time - ionization technique, namely fast atom bombardment (FAB)-MS [12, 13]. Heidmann etal. [14] used FAB-MS to identify conjugation products of reactive quinones with glutathione by conducting dynamic mass spectral analysis. Soon after the introduction of ESI to MS, its potential in the monitoring of biochemical reactions was recognized, especially in the detection of labile intermediates (cf. [15,16]). Nowadays ESI and MALDI are prime tools for the analysis of biomolecules. Both techniques are also suitable for the investigation of biocatalytic processes with diverse temporal resolutions [17]. 

By allowing any solution, but particularly the eluant from a liquid chromatographic column, to flow continuously (dynamically) across a target area under bombardment from fast atoms or ions (FAB or FIB), any eluted components of a mixture are ionized and ejected from the surface. The resulting ions are detected and recorded by a mass spectrometer. The technique is called dynamic FAB or dynamic LSIMS. 

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