Mass spectrometer fast atom bombardment

A fraction of the shocked hexane recovered from the container was directly injected into TCD-GC and FID-GC to determine dissolved H2 and low-molecular-weight hydrocarbons (LHCs), respectively. Another fraction of the shocked hexane was subsequently charged with an internal standard and concentrated by a rotary evaporator. High molecular-weight hydrocarbons (HHCs) in the concentrated solution were analyzed by FID-GC and GCMS. Soot-like materials were analyzed by a fast atom bombardment mass spectrometer (FABMS). 

Smith, L.A., Caprioli, R.M. (1983) Following Enzyme Catalysis in Real-time Inside a Fast Atom Bombardment Mass Spectrometer. Biol. Mass Spectrom. 10 98-102. 

In secondary-ion mass spectrometery (SIMS) and its sister technique fast atom bombardment mass spectrometry (FARMS), a surface is bombarded with energetic particles, and the kinetic energy of the particles converts substrate and chemisorbed atoms and molecules to gas-phase species. The ejected (or sputtered) material is subsequently interrogated using various analytical tools, such as lasers and mass spectrometers, to indirectly deduce information about the initial surface. The relationships between sputtered material and the surface, however, are not always clear, and erroneous conclusions are easily made. Computer simulations have demonstrated that a fundamental understanding of the sputtering process is required to interpret experimental data fully ... 

The low-resolution mass spectrum of Indinavir sulfate was measured using fast atom bombardment mass spectrometry on a JEOL HXl lOA mass spectrometer set at a resolution of 5000. The sample was ionized from a 5 1 dithiothreitol dithioerythritol matrix using xenon as the FAB gas. The low-resolution mass spectrum [12] ofindinavir is shown in Figure 14, while the structures of the structurally significant fragment ions are illustrated in Figure 15. 

Fast atom bombardment mass spectrometry. Fast atom bom-bardment/mass spectrometry (FAB/MS) analyses were performed on a VG ZAB-HF mass spectrometer equipped with an Ion Tech fast atom gun. Xenon gas was activated to 8 kv and 1.5 mA ion current for the fast atom generation. An accelerating voltage of 8 kV was applied to the FAB source. The mass spectrometer was scanned from 800 to 80 amu using an exponential down scan mode at 5 seconds per decade with a 1 second interscan time. The data were recorded with a PDP 11/24 computer and were processed with VG 11/250 software. 

Instruments. The HPLC system for analysis of unchanged semduramicin was modeled after an LC-post column reaction system described earlier for salinomycin sodium in feeds (15-16). The mobile phase consisting of ethyl acetate, iso-octane, glacial acetic acid, triethylamine, methanol (650 + 350 + 44-2 + 1) was used in conjunction with a Dupont Zorbax silica 4.6 mm X 25 cm analytical column. NMR spectra were recorded on a Bruker WM-250 spectrometer (modified to incorporate a pulse programmer and Aspect-3000 data system) and a Bruker AM-500 spectrometer, using 50 mg samples dissolved in CDCI3. The 13C and IH chemical shifts for semduramicin were assigned as reported elsewhere (17). FAB (fast atom bombardment) mass spectra were obtained on a VG 70/250 S spectrometer at 1000 resolution. 

Murphy, R.C. and Harrison, K.A. 1994. Fast atom bombardment mass spectrometry of phospholipids, Mass Spectromet. Rev., 13, 57. 

Tetracycline antibiotics have been determined in bovine liver, kidney, and muscle, and in milk by solid-phase extraction followed by TLC7MS with FAB mass spectrometry (45,46). A reverse-phase C8 bonded phase silica TLC plate was used. Adjacent lanes of standards provided Rf values for the compounds of interest. This area of the chromatogram was cut into a trapezoidal shape, and additional solvent concentrated the sample in one end of the shape. That portion of the chromatogram was then placed on the FAB probe of a high-performance mass spectrometer. Then, the FAB support matrix (thioglycerol) was added to the plate. A detection limit of 0.1 microgram of sample per spot was reported for most of the tetracycline antibiotics. The trapezoidal slice from the TLC plate used to concentrate the sample for TLC/MS analysis was also used in an application of fast atom bombardment mass spectrometry to identify and quantitate the drug midazolam (a depressant and anaesthetic) in plasma extracts by Okamoto et al. (47). 

NMR spectra were recorded on a Briiker AM 300 instrument. IR spectra were recorded on a Perkin Elmer 1710 IR FT spectrometer. UV spectra were recorded on a Perkin-Elmer Lambda 6 spectrometer. Electrochemical measurements were conducted on a Princeton Applied Research Potentiostat/Galvanostat Model 273. Fast atom bombardment mass spectra were performed at University College, Swansea by the S.E.R.C. mass spectrometry service. All elemental analyses were carried out by the Inorganic Chemistry Laboratory, Oxford. 

Fast atom bombardment mass spectra (FAB MS) were obtained with a Kratos MS-50 mass spectrometer equipped with an RF magnet and a DS-55 data system. Fast xenon atoms of 8 keV were used and the spectra were obtained in a thioglycerol matrix. 

A connnon feature of all mass spectrometers is the need to generate ions. Over the years a variety of ion sources have been developed. The physical chemistry and chemical physics communities have generally worked on gaseous and/or relatively volatile samples and thus have relied extensively on the two traditional ionization methods, electron ionization (El) and photoionization (PI). Other ionization sources, developed principally for analytical work, have recently started to be used in physical chemistry research. These include fast-atom bombardment (FAB), matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ES). 

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. 

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. 

Fast-atom bombardment (FAB) is one of a number of ionization techniques which utilize a matrix material, in which the analyte is dissolved, to transfer sufficient energy to the analyte to facilitate ionization. In FAB, the matrix material is a liquid, such as glycerol, and the energy for ionization is provided by a high-energy atom (usually xenon) or, more recently, an ion (Cs+) beam. In conventional FAB, the solution of analyte in the matrix material is applied to the end of a probe which is placed in the source of the mass spectrometer where it is bombarded with the atom/ion beam. 

Several other interface designs were introduced over this period, including continuous flow fast atom bombardment (CFFAB)" and the particle beam interface (PBI)," but it was not until the introduction of the API source that LC/MS applications really came to the forefront for quantitative analysis. Early work by Muck and Henion proved the utility of an atmospheric pressure interface using a tandem quadrupole mass spectrometer. 

The mass spectra of mixtures are often too complex to be interpreted unambiguously, thus favouring the separation of the components of mixtures before examination by mass spectrometry. Nevertheless, direct polymer/additive mixture analysis has been reported [22,23], which is greatly aided by tandem MS. Coupling of mass spectrometry and a flowing liquid stream involves vaporisation and solvent stripping before introduction of the solute into an ion source for gas-phase ionisation (Section 1.33.2). Widespread LC-MS interfaces are thermospray (TSP), continuous-flow fast atom bombardment (CF-FAB), electrospray (ESP), etc. Also, supercritical fluids have been linked to mass spectrometry (SFE-MS, SFC-MS). A mass spectrometer may have more than one inlet (total inlet systems). 

R. S. Annan, H. J. Kochling, J. A. Hill, and K. Biemann. Matrix-Assisted Laser Desorption Using a Fast-Atom Bombardment Ion Source and a Magnetic Mass Spectrometer. Rapid Commun. Mass Spectrom., 6(1992) 298-302. 

---