Fast ion bombardment

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. 

The terms surface ionization mass spectrometry (SIMS) and ion sputtering are often used when accelerated atoms such as Xe or ions such as Ar+ strike a surface causing ionization of the material on the surface. The surface can be solid or liquid in the form of a solution or a suspension in the solvent. In this section, the terms fast atom bombardment (FAB) and fast ion bombardment (FIB) will be used. 

The standard MAT 90 ion source is used for optimized FD/FI mode by means of the newly designed FD/FI probe. Conversion from electron impact (El), chemical ionization (Cl) or fast ion bombardment (FAB) to FD/FI operation does not require the exchange of the ion source. The FD/FI probe accommodates both the field emitter and the extraction electrodes, mounted at the probe tip. Both are introduced as a unit into the ion source through the ionization volume exchange lock without breaking vacuum. The fast and simple changeover illustrates the versatility of the Finnigan MAT 90 with no compromise on the performance. 

Wong, D.C.L. van Compemolle, R. Nowlin, J.G. O Neal, D.L. Johnson, G.M. Use of supercritical fluid extraction and fast ion bombardment mass spectrometry to identify toxic chemicals from a refinery effluent adsorbed onto granular activated carbon. Chemosphere 1996, 32, 621. 

Smith, R. D., Burger, J. E., and Johnson, A. L. (1981). Liquid chromatography-mass spectrometry with electron impact and fast ion bombardment with a ribbon storage interface. Anal. Chem. 53, 1603-1611. 

The earliest applications of MS/MS that utilized LSI methods (FAB or FIB) required placing a few microliters of a viscous glycerol/methanol matrix on a stainless steel probe, insertion into the fast-atom bombardment/ fast-ion bombardment (FAB/FIB) source housing, removal of air from the source, then further insertion of the probe to expose the sample and matrix to the atom or ion beam. Although this procedure was tedious, a... 

Attempts at direct MS characterisation of additives in bulk polymer samples have centred on direct thermal adsorption of additives for the bulk polymer, followed by EI-MS, chemical ionisation (CI-MS) or field ionisation (FI-MS). However, this approach is linked to polymer additives that are stable or can provide meaningful fragment ions at elevated temperatures. Desorption/ionisation methods such as fast ion bombardment (FAB) [41], laser desorption [42, 43] and secondary ion MS (SIMS) have also been applied to the analysis of additives in bulk polymer samples. However, these single step techniques suffer to varying degrees from matrix interferences in the resulting mass spectra. 

Analysis of carnitine and acylcarnitines by MS/MS is now considered routine in those laboratories that possess the appropriate technology. The ionization techniques commonly used with MS/MS are fast atom (or fast ion) bombardment and electrospray. Both are sufficiently sensitive to detect abnormally elevated concentrations of specific metabolites in all types of specimen, although the latter is much more widespread and is the more sensitive of the two, especially for long-chain acylcarnitines. The method is quantitative or at least semi-quantitative for most analytes, and uses stable isotope-labeled forms of the analytes as internal standards. The acylcarnitines are analyzed simultaneously in the positive ion mode as their methyl or butyl esters using a precursor ion scan function [14, 23] that detects the parent (molecular) ions. Free carnitine and total carnitine are determined by assaying the same specimen before and after alkaline hydrolysis, without derivatization, using Hs-carnitine as internal standard [17]. The value for acylcarnitine is determined by difference. This value includes the contribution of short, medium and long-chain acylcarnitines. Analysis time for each method is approximately 2 min. 

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