Fast-atom bombardment LSIMS ionization

Fast-Atom Bombardment (FAB) and Liquid-Phase Secondary Ion Mass Spectrometry (LSIMS) Ionization... 

Mass Spectrometry. Mass spectrometry holds great promise for low-level toxin detection. Previous studies employed electron impact (El), desorption chemical ionization (DCI), fast atom bombardment (FAB), and cesium ion liquid secondary ion mass spectrometry (LSIMS) to generate positive or negative ion mass spectra (15-17, 21-23). Firm detection limits have yet to be reported for the brevetoxins. Preliminary results from our laboratory demonstrated that levels as low as 500 ng PbTx-2 or PbTx-3 were detected by using ammonia DCI and scans of 500-1000 amu (unpublished data). We expect significant improvement by manipulation of the DCI conditions and selected monitoring of the molecular ion or the ammonia adduction. 

Fast-atom bombardment (FAB) and liquid secondary-ion mass spectrometry (LSIMS) methods make up the category of the particle bombardment ionization. In both methods the analyte is dissolved in a liquid such as glycerol, thioglycerol, m-nitrobenzyl alcohol, or diethanolamine and about 1 1 is placed on a... 

Mass spectrometer or tandem mass spectrometer (JEOL, Micromass, MAT from ThermoFinnigan) equipped with direct insertion probe and fast atom bombardment (FAB) or liquid secondary ion mass spectrometry (LSIMS) for LC/MS or flow injection using continuous-flow FAB, mass spectrometer must be equipped with continuous-flow ionization source... 

There are numerous other ionization methods, but they have limited applications. Fast atom bombardment (FAB), also known as liquid secondary ion mass spectrometry (LSIMS), was one of the early methods developed for the ionization of polar molecules. FAB is based on bombarding analytes in a matrix of low volatility, such as glycerol, with accelerated energetic neutral atoms (argon or xenon) or ions (cesium) that wiU sputter [M + H]+ ions from the surface. Although of major importance during its heyday, FAB has been superseded by ESI. 

The techniques of fast-atom bombardment (FAB)/ liquid secondary ionization (LSIMS), developed in the early 1980s, revolutionized the range of compounds amenable to analysis by MS and opened up the field to many areas of biomedical research. Although now considered insensitive by comparison with more recently introduced ionization modes, FAB still has a role as a rapid, reliable, and robust... 

Chapter 6, titled Selection of Ionization Methods of Analytes in the TLC-MS Techniques provides an overview of mass spectrometric techniques that can be coupled with TLC and act as specific detectors in this hyphenated approach. The mass spectrometric techniques discussed in this chapter are secondary mass spectrometry (SIMS), liquid secondary ion mass spectrometry (LSIMS), fast atom bombardment (FAB), matrix-assisted laser desorption/ionization (MALDI), atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI), electrospray ionization (ESI), desorption electrospray ionization (DESI), electrospry-assisted laser desorption/ionization (ELDI), easy ambient sonic spray ionization (EASI), direct analysis in real time (DART), laser-induced acoustic desorption/electrospray ionization (LIAD/ESI), plasma-assisted multiwavelength laser desorption/ionization (PAMLDI), atmospheric-pressure chemical ionization (APCI), and dielectric barrier discharge ionization (DBDI). For the sake of illustration, the authors introduce practical examples of implementing TLC separations with detection carried out by means of individual mass spectrometric techniques for the systematically arranged compounds belonging to different chemical classes. 

Fast atom bombardment MS (FAB-MS) and liquid secondary ion MS (LSIMS) are matrix-mediated desorption techniques that use energetic particle bombardment to simultaneously ionize samples such as carotenoids and transfer them to the gas... 

Older soft ionization methods that are related to MALDl—such as fast atom bombardment (FAB), hquid secondary ion mass spectrometry (LSIMS), or field desorption (FD)— in principle have potential for the generation of intact gas-phase ions from noncovalent complexes. In particular, the extensive clustering often found in FAB-MS, which is generally thought of as a nuisance, can be viewed as evidence for this. However, the limitation of these methods lies in their inabiUty to ionize very large molecules. It is generally very difficult or impossible to obtain useful mass spectra from compounds with molecular weights above a few thousand daltons. For this reason, FAB-MS, LSIMS, and FD-MS only play a very minor role in this field. 

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. 

In widespread use since 1982 (Barber et al., 1982), FAB and LSIMS are matrix-mediated techniques. The most effective matrix for static FAB/LSIMS analysis of chlorophylls and their derivatives is 3-nitrobenzyl alcohol (van Bree-men et al., 1991a), whereas glycerol provides adequate sensitivity and a more robust system during continuous-flow FAB/LSIMS (van Breemen et al., 1991b). Ionization and desorption of the chlorophyll analyte occur together during the bombardment of the matrix by fast atoms (or ions) to produce molecular ions, M+-, and protonated molecules, [M+H]+. 

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