Fast Atom Bombardment Ionization

Fast atom bombardment (FAB) uses high-energy xenon or argon atoms (6-10 keV) to bombard samples dissolved in a liquid of low vapor pressure (e.g., glycerol). The matrix protects the sample from excessive radiation damage. A related method, liquid secondary 

FIGURE 1.4 The electron impact (El), chemical ionization (Cl), and field desorption (FD) mass spectra of cholest-5-ene-3,16,22,26-tetrol. 

FAB was introduced in 1981 by Barber et al. [17, 18]. In FAB [17-20], the analyte of interest is dissolved in an appropriate matrix solvent, such as glycerol, diethanolamine and other rather polar solvents with low vapor pressure. The solution is applied as a thin film onto a metal target, which subsequently is brought in a beam of high-energy particles (see Fig. 7.2). FAB differed from the already existing SIMS method [21] in two experimental aspects, i.e., the use of abeam of atoms instead of a beam of ions as primary particles, and the use of a hquid matrix for dissolving the 

In FAB spectra, mostly even-electron species are detected formed by protonation or cationization with alkali-metal ions in positive-ion mode and by deprotonation in negative-ion mode. The (few) fragment ions observed can be explained by elimination of neutral molecules from the initial even-electron species. Next to analyte-related peaks, (abundant) background peaks are observed, which can be attributed to protonated matrix clusters, e.g., [(Glycerol)jj+H]+ with n=1-10. A high chemical noise, also called peak-at-eveiy-mass or incoherent fragmentation, is a characteristic feature of FAB, the origin of which is not well understood. 

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The full potential of LC-MS could not be exploited until it was possible to study involatile and thermally labile compounds for which electron and chemical ionization are not appropriate. A relatively small number of reports of the use of the moving-belt interface with fast-atom bombardment ionization for the study of these types of compound have appeared. 

H. Y. Lin, G. Gonyea, S. Killeen, and S. K. Chowdhury. Negative Fast Atom Bombardment Ionization of Aromatic Sulfonic Acids Unusual Sample-Matrix Interaction. Rapid Commun. Mass Spectrom., 14(2000) 520-522. 

Fast-atom bombardment ionization [27,28] was introduced in the early 1980s and was the first widely used desorption ionization technique. Its universal appeal stemmed from its ability to ionize polar,... 

Most of the direct and indirect (transport) interfaces described here use chemical ionization (c.i.) ion-sources, which are not well suited to such polar, non-volatile compounds as tri- and higher oligosaccharides. The thermospray interface, which can operate on an ion-evaporative mode, is capable of producing intact molecular ions from such nonvolatile, polar molecules and should be useful in oligosaccharide analysis. Molecules of this type, however, can also be easily analyzed by fast-atom-bombardment ionization, and use of this technique, coupled to direct liquid introduction and moving-belt interfaces, has been reported. The latter system has been applied to complex oligosaccharide analysis. ... 

The fast atom bombardment ionization (FAB) technique is a soft ionization method, typically requiring the use of a direct insertion probe for sample introduction in which a high energy beam of Xe atoms, Cs+ ions, or massive glycerol-NH4+ clusters sputter the sample and matrix from the probe surface (Figure 8). 

McLafferty et al. (37) studied the collisionally activated dissociation (CAD) of the ions resulting from the fast-atom bombardment ionization of cyano- and methylcobalamins, using a tandem mass spectrometer. They showed that mlz 1329 is produced only from the quasi-molecular ion. Similar CAD spectra are produced by both the quasi-molecular ions and the 1329 peak, indicating that essentially all fragmentation arises from this latter ion. CAD spectra produced for the 1329 ion derived from methylcobalamin or vitamin B12 coenzyme are also similar. This is consistent with the work of Taylor (10), who used linked-scan metastable ion techniques in a conventional double-focusing mass spectrometer to show the same thing. The sequential... 

FAB Spectrum obtained with fast atom bombardment ionization. 

Phospholipids are hydrophobic molecules present in all living organisms. They are applied as building blocks of cellular membranes, but serve several other functions as well. The most important classes of phospholipids in eukaryotic cells are the sphingomyelins (SM, Figure 21.4) and glycerophospholipids (GPL, Table 21.2), while phosphoglycolipids are found in prokaryotic cells. Fast-atom bombardment ionization (FAE) first enabled the use of MS and MS-MS for the structural characterization of phospholipids. ESI-MS further facilitated this. ESI-MS characterization of phospholipids was reviewed by Pulfer and Murphy [3]. 

Figure 2.6. Conceptual depiction of fast atom bombardment ionization process. (Reproduced from C. Dass, Principles and Practice of Biological Mass Spectrometry, Wiley-Interscience, 2001.)...

Highly reactive platinum carbene species have been generated in the gas phase via the fast atom bombardment ionization of ethyl diazoethanoate complex 136 (Scheme 33). " Elimination of dinitrogen leads to carbene species 137, which are implicated in the reactivity of the precursor complexes, but had not previously been detected in solution. 

TOF-TOF Instruments. A simple design for a tandem (TOF-TOF) instrument that incorporates two drift regions separated by a collision chamber has been reported by Jardine et al. As shown in Figure 9.5, the instrument uses fast-atom bombardment ionization. Because this is a continuous ionization technique, a deflection gating system is used to define the initial ion packet, while a second set of deflectors (located close to the collison chamber) is used for mass selection. In addition, the collision cell is raised to a voltage that is intermediate between ground and the source potential, so that product ions will be reaccelerated and will have velocities different from their precursors. 

Fast Atom Bombardment Ionization in Mass Spectrometry... 

Fast Atom Bombardment Ionization in Mass Spectrometry Field Ionization Kinetics in Mass Spectrometry Glow Discharge Mass Spectrometry, Methods... 

See also Chemical Ionization in Mass Spectrometry Fast Atom Bombardment Ionization in Mass Spectrometry Fragmentation in Mass Spectrometry Ion Structures in Mass Spectrometry Ion Trap Mass Spectrometers Ionization Theory Ion Energetics in Mass Spectrometry Ion Collision Theory Metastable Ions Quadrupoles, Use of in Mass Spectrometry Sector Mass Spectrometers Statistical Theory of Mass Spectra Time of Flight Mass Spectrometers. 

FAST ATOM BOMBARDMENT IONIZATION IN MASS SPECTROMETRY 505... 

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