Ionization-trap mass spectrometr

The mass spectrometric behavior of the isomeric 2-oxo-2H- and 4-oxo-4 -6,7,8,9-tetrahydropyrido[l,2-<3]pyrimidines was studied under electron-impact induced polarization (97RCM664). The molecular ion of the 2-OXO-2H isomer appeared to be much more stable than that of the 4-oxo-4 isomer. The fragmentation of the molecular ion (M+) of the 4-oxo-4 isomer is related mostly to the saturated piperidine ring, whereas that of the 2-oxo-2H isomer is much more selective, the only significant process is the primary loss of a CO molecule from the pyrimidinone ring via contraction of the ring. Electrospray ionization quadrupole ion-trap mass spectrometric characterization of risperidon (11) was presented and a possible mechanism for the observed fragmentation pattern was... 

Hsu, RR, Turk, J., Rhoades, E.R., Russell, D.G., Shi, Y.X. and Groisman, E.A., Structural characterization of cardiohpin by tandem quadrupole and mulhple-stage quadrupole ion-trap mass spectrometry with electrospray ionization. J. Am. Soc. Mass Spectrom., 16, 491-504 (2005). Hsu, RR and Turk, J., Characterization of cardiohpin from Escherichia coli by electrospray ionization with multiple stage quadrupole ion-trap mass spectrometric analysis of [M — 2H -I Na](—) ions. J. Am. Soc, Mass Spectrom., 17, 420-429 (2006). 

Simitsek, ED., Giannikopoulou, R, Katsoulas, H., et al Electrophoretic, size-exclusion high-performance liquid chromatography and liquid chromatography-electrospray ionization ion trap mass spectrometric detection of hemoglobin-based oxygen carriers. Analytica Chimica Acta, 583,223-230. 

A direct mass spectrometric method for simultaneous detection of five benzimidazoles including levamisole, thiabendazole, mebendazole, fenbendazole, and febantel in sheep milk was reported (377). The method, which involves injection of crude milk extracts and selection and collision of the most abundant ionic species obtained under electron impact ionization, was highly sensitive and rapid. Another direct mass spectrometric approach for rapid and quantitative determination of phenothiazine in milk was also described (323). This method involves an extraction step using a Cig microcolumn disc, followed by thermal desorption of the analyte from the disc directly into an ion trap mass spectrometer. 

Because of the importance of the biphenyl scaffold, as a structure of pharmaceutical and active therapeutic compounds, the mass spectrometric behavior of a series of 6,6-disubstituted dibenzo[r//][l,3]dioxepins 36 has been studied. The electron ionization-induced fragmentation patterns were discussed based on use of labeled compounds, accurate mass measurements, and collisionally induced dissociation experiments using an ion trap <2006JMP577>. 

Considerable insight about fundamental aspects of the behavior of simple Ge, Sn and Pb species can be obtained from studies aimed at characterizing the reactivity of gas-phase ions. Reactions of the primary ions obtained by electron ionization of GelTj with the neutral monogermane precursor have been characterized both by low- and high-pressure mass spectrometric techniques , and more recently by ion trap techniques (ITMS). The ability to select a particular isotopic species (usually the Ge-containing ion) in low pressure studies carried out by Fourier Transform Mass Spectrometry (FTMS) has been essential in understanding the mechanism of these processes. The main results can be summarized as follows ... 

Mass analyzers use physical principles to separate the generated ions coming from the ionization source. Many physical principles have been tested for that purpose but only a few of them have become successful and are still enhanced to achieve better results in mass spectrometric analysis. The most common mass analyzers are listed in Table 5.2. Although in principle any source can be connected with any analyzer, some combinations are more common. For example, MALDI as a discontinuously working ion source can easily be coupled with time-of-flight analyzers, while ESI sources are often combined with quadrupoles and ion traps. Therefore, we restrict the discussion here to those analyzers which are typically available together with MALDI and ESI ion sources. 

Hernando, M. D., Aguera, A., Eemandez-Alba, A. R., Piedra, L., and Contreras, M., Gas chromatographic determination of pesticides in vegetable samples by sequential positive and negative chemical ionization and tandem mass spectrometric fragmentation using an ion trap analyzer. Analyst, 26, 46-51, 2001. 

Ions prcxluced in the center of the trap (usually by electron impact) are constrained by the magnetic field and applied potentials on the trapping plates to follow orbits within the cell and only slowly diffuse toward the walls. During the time the ions are trapped, they may have maiy collisions with neutral molecules in the trap, and these collisions can lead to thermalization of the ions and may result in chemical reactions. At a neutral pressure of 10 torr, the approximate pseudo first-order rate constant for ion-molecule collisions is 30 s. The ionic products of ionization and subsequent reactions in the cell can be detected at aiy time mass spectrometrically application of a broad range of radio frequencies and detection of resonance at cyclotron frequencies corresponding to m/z values of the ions present. Techniques are available that allow isolation of one or more m/z value in the ion population by ejection of all other ions, and this allows the reactions of a particular ion to be followed directly. Fourier transform methods, intrcxluced by Marshall and... 

Tbe reader new to mass spectrometry is advised to consult an appropriate introductory text [2-9]. A few mass spectrometric terms will be explained here by way of background and to outline the principles of choosing a flame ionization detector, ions are produced in the mass spectrometric detector, but the mass spectrometer is able to analyze these ions further according to their molecular weights or rather, mass-to-charge ratios (m/z, see below) to provide a mass spectrum. Different principles are employed to achieve this in a variety of types of mass spectrometer. The instruments most commonly used in GC—MS are known as magnetic sector, quadrupole and ion trap mass spectrometers. Their differences are not further described here. Bench-top systems are of the quadrupole or ion trap type. 

Hopfgartner G, Varesio E, Stoeckli M. Matrix-assisted laser desorption/ionization mass spectrometric imaging of complete rat sections using a triple quadrupole linear ion trap. Rapid Commtm Mass Spectrom 2009 23(6) 733—736. 

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