Dynamic fast-atom bombardment

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

The LC/TOF instmment was designed specifically for use with the effluent flowing from LC columns, but it can be used also with static solutions. The initial problem with either of these inlets revolves around how to remove the solvent without affecting the substrate (solute) dissolved in it. Without this step, upon ionization, the large excess of ionized solvent molecules would make it difficult if not impossible to observe ions due only to the substrate. Combined inlet/ionization systems are ideal for this purpose. For example, dynamic fast-atom bombardment (FAB), plas-maspray, thermospray, atmospheric-pressure chemical ionization (APCI), and electrospray (ES)... 

This method is still in use but is not described in this book because it has been superseded by more recent developments, such as particle beam and electrospray. These newer techniques have no moving parts, are quite robust, and can handle a wide variety of compound types. Chapters 8 through 13 describe these newer ionization techniques, including electrospray, atmospheric pressure ionization, plasmaspray, thermospray, dynamic fast-atom bombardment (FAB), and particle beam. 

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. 

LC can be combined with all kinds of mass spectrometers, but for practical reasons only quadrapolar, magnetic/electric-sector, and TOP instruments are in wide use. A variety of interfaces are used, including thermospray, plasmaspray, electrospray, dynamic fast-atom bombardment (FAB), particle beam, and moving belt. 

The Continuous-Flow/Frit (Dynamic) Fast-Atom-Bombardment Interface... 

Thus as a starting point for understanding the bombardment process we have developed a classical dynamics procedure to model the motion of atomic nuclei. The predictions of the classical model for the observables can be compared to the data from sputtering, spectrometry (SIMS), fast atom bombardment mass spectrometry (FABMS), and plasma desorption mass spectrometry (PDMS) experiments. In the circumstances where there is favorable agreement between the results from the classical model and experimental data It can be concluded that collision cascades are Important. The classical model then can be used to look at the microscopic processes which are not accessible from experiments In order to give us further insight into the ejection mechanisms. 

R. M. Caprioli, On-line fast atom bombardment analysis of dynamic biological systems, Biomed. Environ. Mass Spectrom. 16, 35-39 (1988). 

In the 1980s, attempts were made to enable continuous introduction of liquid samples (especially aqueous buffer solutions) to ion sources of mass spectrometers. An early con-tiuous flow interface was based on the fast atom bombardment (FAB) ion source [70]. However, it was the ESI interface that greatly facilitated temporal profiling of dynamic... 

On-line MS methods enable continuous kinetic profiles to be obtained but they cannot easily accommodate complex sample preparation steps. In the 1980s, enzymatic reactions were monitored by a popular - at that time - ionization technique, namely fast atom bombardment (FAB)-MS [12, 13]. Heidmann etal. [14] used FAB-MS to identify conjugation products of reactive quinones with glutathione by conducting dynamic mass spectral analysis. Soon after the introduction of ESI to MS, its potential in the monitoring of biochemical reactions was recognized, especially in the detection of labile intermediates (cf. [15,16]). Nowadays ESI and MALDI are prime tools for the analysis of biomolecules. Both techniques are also suitable for the investigation of biocatalytic processes with diverse temporal resolutions [17]. 

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. 

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