Spectrometry rapid-scan

Welham, K. J. Domin, M. A. Scanned, D. E. Cohen, E. Ashton, D. S. The characterization of micro-organisms by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Rapid Comm. Mass. Spectrom. 1998, 12, 176-180. 

In the past decade, as systems have become simpler to operate, mass spectrometry (MS) has become increasingly popular as a detector for GC. Of all detectors for GC, mass spectrometry, often termed mass selective detector (MSD) in bench-top systems, offers the most versatile combination of sensitivity and selectivity. The fundamentals of MS are discussed elsewhere in this text. Quadrupole (and ion trap, which is a variant of quadrupole) mass analyzers, with electron impact ionization are by far (over 95%) the most commonly used with GC. They offer the benefits of simplicity, small size, rapid scanning of the entire mass range and sensitivity that make an ideal detector for GC. 

The aquated iron(III) ion is an oxidant. Reaction with reducing ligands probably proceeds through complexing. Rapid scan spectrophotometry of the Fe(III)-cysteine system shows a transient blue Fe(lII)-cysteine complex and formation of Fe(II) and cystine. The reduction of Fe(lII) by hydroquinone, in concentrated solution has been probed by stopped-flow linked to x-ray absorption spectrometry. The changing charge on the iron is thereby assessed. In the reaction of Fe(III) with a number of reducing transition metal ions M in acid, the rate law... 

Mondello, L., Casilli, A., Tranchida, P.Q., Dugo, G., Dugo, P. (2005) Comprehensive two-dimensional gas chromatography in combination with rapid scanning quadrupole mass spectrometry in perfixme analysis. J. Chromatogr. A 1067 235-243. 

In general, the quadrupole instruments do not achieve the mass range and the high resolution of sector instruments. However, the mass range and resolution are adequate for unit-resolution mass spectrometry, and the rapid scan and sensitivity make them especially suitable for use with capillary gas chromatography (Fig. 2.46). 

The Frankfort LPA instrument (51-53) departs from both of these instruments in two principal ways it achieves the necessary path length within a 6-m folded-path cell, and it rapidly scans a narrow-band frequency-doubled dye laser across the spectral region of interest (the Qi(2) line group) in a process sometimes called differential optical absorption spectrometry (DOAS). The scanning rate is sufficient to ensure that the observed air volume is chemically and physically stationary during each scan (the baseline standard deviation is less than 2 x 10-4 for a 0.2-ms scan). The laser output is actively feedback-stabilized to provide a flat spectral baseline, and a detection limit better than 10"5 in optical density has been claimed. A summary of published LPA configurations is given in Table II. 

King, R. C., Gundersdorf, R., and Femandez-Metzler, C. L. (2003). Collection of selected reaction monitoring and full scan data on a time scale suitable for target compound quantitative analysis by liquid chromatography/tandem mass spectrometry. Rapid Commun. Mass Spectrom. 17 2413-2422. 

Barcelo, D., G. Durand, V. Bouvot, and M. Nielen (1993). Use of extraction disks for trace enrichment of various pesticides from river water and simulated seawater samples followed by liquid chromatography-rapid-scanning UV-visible and thermospray-mass spectrometry detection. Environ. Sci. Technol., 27(2) 271-277. 

Mazzarino M et al (2010) Mass spectrometric characterization of tamoxifene metabolites in human urine utilizing different scan parameters on liquid chromatography/tandem mass spectrometry. Rapid Commun Mass Spectrom 24 749-760... 

Temporal Devices. A temporal dispersive device uses a single channel which is scanned as a function or time to yield information on the intensities present in various resolution elements. Two basic approaches are possible (1) the detector may be scanned across a fixed spectrum or (2) the spectrum may be scanned across a fixed detector. In addition, these systems may be further differentiated on the basis of the manner in which the spectrum is scanned. Thus, linear-scan systems scan the spectrum at a constant, fixed rate. In contrast, programmed-scan systems have the capability of momentarily stopping at wavelengths of analytical interest, while spectral regions of little interest are rapidly scanned. For a complete review of the area of rapid-scanning spectrometry up to 1968, the interested reader should consult Volume T of Applied Optics which was entirely devoted to this subject. 

Fourier transform mass spectrometry (FTMS) was first described by Comisarow and Marshall in 1974 [59,60] and was reviewed by Amster [61] in 1996 and by Marshall et al. [62] in 1998. This technique consists of simultaneously exciting all of the ions present in the cyclotron by a rapid scan of a large frequency range within a time span of about 1 ps. This induces a trajectory that comes close to the wall perpendicular to the orbit and also puts the ions in phase. This allows transformation of the complex wave detected as a time-dependent function into a frequency-dependent intensity function through a Fourier transform (FT), as shown in Figures 2.60 and 2.61. 

Reepmeyer, J. C., Revelle, L. K., and Vidavsky, I. (1998), Detection of clobetasol propionate as an undeclared steroid in zinc pyrithione formulations by high-performance liquid chromatography with rapid-scanning ultraviolet spectroscopy and mass spectrometry. Journal of Chromatography A, Vol. 828, Number 1,18 December 1998, pp. 239-246(8). 

The determination of trace metal impurities in pharmaceuticals requires a more sensitive methodology. Flame atomic absorption and emission spectroscopy have been the major tools used for this purpose. Metal contaminants such as Pb, Sb, Bi, Ag, Ba, Ni, and Sr have been identified and quantitated by these methods (59,66-68). Specific analysis is necessary for the detection of the presence of palladium in semisynthetic penicillins, where it is used as a catalyst (57), and for silicon in streptomycin (69). Furnace atomic absorption may find a significant role in the determination of known impurities, due to higher sensitivity (Table 2). Atomic absorption is used to detect quantities of known toxic substances in the blood, such as lead (70-72). If the exact impurities are not known, qualitative as well as quantitative analysis is required, and a general multielemental method such as ICP spectrometry with a rapid-scanning monochromator may be utilized. Inductively coupled plasma atomic emission spectroscopy may also be used in the analysis of biological fluids in order to detect contamination by environmental metals such as mercury (73), and to test serum and tissues for the presence of aluminum, lead, cadmium, nickel, and other trace metals (74-77). 

Other Specific Detectors. The most elegant of the specific detectors used for gas chromatography is the mass spectrometer. (This application of mass spectrometry was discussed in Chapter 16.) Infrared spectrometry has become a practical detection method, now that rapid-scan infrared systems have made collecting samples unnecessary. In fact, part of the impetus behind developing both these techniques was the difficulty in collecting gas chromatographic fractions vapor samples entering cold... 

Numerous, wide-ranging spectroscopic techniques will be presented in this volume, with the exception of nuclear magnetic resonance (NMR), which was the subject of Volumes 176, 177, and 239 of Methods in Enzy-mology, and mass spectrometry, which was the subject of Volume 193. Examples of techniques from each of three major areas, ultraviolet/visible spectroscopy, vibrational spectroscopy, and electron or electron/nuclear magnetic resonance, are presented in this volume. Also included are special topics like rapid-scan diode-array spectroscopy, terbium labeling of chromopeptides, and deconvolution of complex spectra that are covered in chapters in Section IV of this volume. 

Why is it important to use a rapid-scanning mass spectrometry system for data collection from a high-resolution separation device ... 

Paglia G, D Apolito O, Corso G. Precursor ion scan profiles of acylcarnitines by atmospheric pressure thermal desorption chemical ionization tandem mass spectrometry. Rapid Commun Mass Spectrom 2008 22 3809-3815. 

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