Liquid secondary-ion mass spectrometry LSIMS

FAB has evolved, and fast atoms are being replaced by fast ions, such as cesium (Cs+). This variation is called liquid secondary ion mass spectrometry (LSIMS) because the sample solution affords the secondary ion beam while the bombarding ions constitute the primary beam. Spectra... 

Historically, the term SIMS was developed for bombardment of solid surfaces with ions, so, for greater descriptive precision, the name liquid secondary ion mass spectrometry (LSIMS) is better and can be used synonymously with FAB,... 

The term liquid secondary ion mass spectrometry (LSIMS) is sometimes used synonymously with FAB and is preferred by some as being more descriptive, since FAB could apply to bombardment of solid or liquid surfaces and does not indicate the types of secondaries investigated. In practice, little confusion is likely to result from using either term. Strictly, LSIMS can refer to the use of fast ions (FIB). 

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that levels as low as 500 ng PbTx-2 or PbTx-3 were detected by using ammonia DCI and scans of 500-1000 amu (unpublished data).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... 

In FAB, the sample is usually dispersed in a non-volatile liquid matrix, such as glycerol or diethanolamine, and deposited at the end of a sample probe that can be inserted into the ion source. The sample on the probe is ionised when bombarded by the fast atom beam. However, ionisation of the matrix also occurs, leading to a very large background signal. The technique is thus limited for the analysis of small molecules. Fast-moving ions (Cs+ or Ar+) can be used instead of fast-moving atoms, which is the basis of a technique called liquid secondary ion mass spectrometry (LSIMS). 

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... 

Modern techniques of mass spectrometry allow the determination of some polymer characteristics. The main studies are devoted to mass determinations (no standardization necessary) of polyethyleneglycols, polystyrenes and polymethylmethacrylates. However, a liquid secondary ion mass spectrometry (LSIMS) study [42] on a thermal polymer of a mononadimide model compound permits an approach to the determination of the polymer microstructure and goes some way to understanding the polymerization mechanism. 

In 1994, Oppenheimer and coworkers73 reported a study of the gas-phase generation of arabinosyl oxocarbenium ions via use of tandem positive-ion liquid secondary ion mass spectrometry (LSIMS) (Scheme 37). Plots of log ([oxocarbenium ion]/([M+] +[oxocarbenium ion])) versus rate constants for solvolysis of the same series afford a p of -6.7. While the basis for this difference in p is not clear, it is reasonable to propose that the reaction in the gas phase is similar in nature to the solution reaction. With ion trap or FTICR instrumentation, studies such as these might be extended to following the fate of the oxocarbenium ion as it reacted with nucleophiles introduced into the mass spectrometer. 

Hoffmaniolide (180) has been isolated from Prorocentrum hoffmannianum The gross structure of hoffmaniolide (180) was obtained by analyzing the liquid secondary ion mass spectrometry (LSIMS)-MS/MS spectrum as well as 2D NMR such as H- H COSY, TOCSY, and HMBC, and the relative stereochemistry of a tetrahydropyran ring was obtained from J coupling data. Isolation of hoffmanniolide (180) from P. hoffmannianum suggested a biosynthetic capability of this genus to produce either linear or macrocyclic polyethers. 

Vivas, N., Bourgeois, G., Vitry, C., Glories, Y, and de Freitas, V., Determination of the composition of commercial tannin extracts by liquid secondary ion mass spectrometry (LSIMS), J. Sci. Food Agric.,... 

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

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. 

Of the two related techniques, FAB found far greater use in studies of enantioselective discrimination as compared to other desorption/ionization methods, such as MALDI and secondary ion mass spectrometry (SIMS). Chan and coworkers demonstrated enantiodiscrimina-tion of amino acids by a-, P-, and y-cyclodextrins using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) [28]. The observed levels of enantioselectivity were found to be dependent on the size of cyclodextrin cavities, as well as on the length and functionality of the amino acid side chain. Vairamani and coworkers demonstrated discrimination of amino acid methyl esters using various monosaccharide hosts by liquid secondary ion mass spectrometry (LSIMS) [29]. It is curious that more work has not been done using these sources. MALDI, in particular, is a simple and straightforward technique. Various researchers have demonstrated the observation of noncovalent complexes [30-32], for example, between peptides and proteins, but relatively little work has been performed that focuses on studying enantioselective noncovalent interactions by MALDI-MS. 

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. 

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