Fast atom bombardment LSIMS

E. DePauw, A. AgneUo, and F. Davva, Liquid matrices for liquid secondary ion mass spectrometry-fast atom bombardment [LSIMS-FAB] an update. Mass Spectrom. Rev.lO, 283-301 (1991). 

De Pauw, E. Agnello, A. Derwa, F. Liquid Matrices for Liquid Secondary Ion Mass Spectrometry-Fast Atom Bombardment [LSIMS-FAB] an Update. Mass Spectrom. Rev. 1991, 70, 283-301. 

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

A big step forward came with the discovery that bombardment of a liquid target surface by abeam of fast atoms caused continuous desorption of ions that were characteristic of the liquid. Where this liquid consisted of a sample substance dissolved in a solvent of low volatility (a matrix), both positive and negative molecular or quasi-molecular ions characteristic of the sample were produced. The process quickly became known by the acronym FAB (fast-atom bombardment) and for its then-fabulous results on substances that had hitherto proved intractable. Later, it was found that a primary incident beam of fast ions could be used instead, and a more generally descriptive term, LSIMS (liquid secondary ion mass spectrometry) has come into use. However, note that purists still regard and refer to both FAB and LSIMS as simply facets of the original SIMS. In practice, any of the acronyms can be used, but FAB and LSIMS are more descriptive when referring to the primary atom or ion beam. 

The basic principles of fast-atom bombardment (FAB) and liquid-phase secondary ion mass spectrometry (LSIMS) are discussed only briefly here because a fuller description appears in Chapter 4. This chapter focuses on the use of FAB/LSIMS as part of an interface between a liquid chromatograph (LC) and a mass spectrometer (MS), although some theory is presented. 

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that levels as low as 500 ng PbTx-2 or PbTx-3 were detected by using ammonia DCI and scans of 500-1000 amu (unpublished data).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) Plasma desorption (PD) Liquid secondary-ion mass spectrometry (LSIMS) Thermospray (TSP)/plasmaspray (PSP) Electrohydrodynamic ionisation (EHI) Multiphoton ionisation (MPI) Atmospheric pressure chemical ionisation (APCI) Electrospray ionisation (ESI) Ion spray (ISP) Matrix-assisted laser desorption/ionisation (MALDI) Atmospheric pressure photoionisation (APPI) Triple quadrupole (QQQ) Four sector (EBEB) Hybrid (EBQQ) Hybrid (EB-ToF, Q-ToF) Tandem ToF-ToF Photomultiplier... 

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... 

FAST ATOM BOMBARDMENT (FAB), LIQUID SECONDARY ION MASS SPECTROMETRY (LSIMS), AND CONTINUOUS-FLOW FAB OF CHLOROPHYLLS... 

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... 

Figure 5.13 Sketch of a fast atom bombardment (FAB) ion source. The potential difference between the probe tip and extraction grid (not shown) accelerates the ions (from both the Uquid matrix and analyte) into the mass spectrometer. Since a large quantity of neutral matrix is also sputtered by the fast primary beam, the source region must be provided with adequate pumping and the m/z analyzer region differentially pumped. The fast atom beam can be replaced by a beam of fast primary ions (often Cs ) and the technique is then sometimes referred to as Uquid assisted secondary ion mass spectrometry (LSIMS).

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 (FAB) and liquid secondary ion mass spectrometry (LSIMS)... 

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... 

Fast atom bombardment (FAB) mass spectrometry has been widely used for the analysis of high-MW and/or thermally labile compounds [204]. As with all ionisation techniques that use a direct insertion probe, accurate and precise quantification is difficult to achieve here. With FAB and FIB/LSIMS the sample signal often dies away when the matrix, rather than the sample, is consumed therefore, one cannot be sure that the ion signal obtained represents the entire sample. Quantification in FD or FAB-MS has been described as technically difficult, but possible when internal standards are used [205]. Lat-timer et al. [206] compared FAB and FD as ionisation techniques for mass spectrometric analysis of... 

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. 

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