Journal of the Mass Spectrometry Society of Japan
Online ISSN : 1880-4225
Print ISSN : 1340-8097
ISSN-L : 1340-8097
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Volume 46, Issue 6
Displaying 1-4 of 4 articles from this issue
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INTEGRATED PAPER
  • Unimolecular Dissociation of Gaseous Ions in EI Mass Spectrometry
    Takae TAKEUCHI
    1998 Volume 46 Issue 6 Pages 477-482
    Published: 1998
    Released on J-STAGE: July 20, 2007
    DOIhttps://doi.org/10.5702/massspec.46.477
    JOURNAL FREE ACCESS
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    The fragmentation mechanisms of gaseous ions were studied experimentally and theoretically. In order to contribute to construction of fragmentation theory in mass spectra, the principle was examined using three separate approaches. Firstly, energy dependence on the fragmentation of molecular ions was investigated using the threshold electron-photoion coincidence (TEPICO) technique. Secondary, fragmentation mechanisms of molecular ions (n-butane, 1-propanol, n-propyl amine, and cycloglycylglycine cation radicals and a series of organosilicon cation radicals) in the low energy region were studied using ab initio molecular orbital (MO) methods. Finally, the dissociation (by hydrogen loss) of the first excited state (Ã2B1) of the formaldehyde cation as a function of its vibrational excitation was analyzed. Its mechanism involved an electronic predissociation by the ground X2B2 state in the tunneling regime. A statistical treatment for nonadiabatic interactions accounted for the low value of the rate constant as well as for a large isotope effect that persists over an energy interval of ca. 0.7 eV.
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REGULAR PAPERS
  • Stable Cluster Ions in Carboxylic Acid-Water Binary Systems and Their Reactivity with Ammonia Studied by Liquid Ionization Mass Spectrometry
    Masahiko TSUCHIYA, Shiho TESHIMA, Atsushi SHIGIHARA, Tsuneo HIRANO
    1998 Volume 46 Issue 6 Pages 483-489
    Published: 1998
    Released on J-STAGE: July 20, 2007
    DOIhttps://doi.org/10.5702/massspec.46.483
    JOURNAL FREE ACCESS
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    Intense peaks of cluster ions, (RCOOH)5(H2O)H+, have been observed for monocarboxylic acid-water binary systems and a stable ring-type structure has been suggested. The stability and the structure of such cluster ions in the acetic acid-water mixture were investigated by measuring reactions between binary cluster ions and ammonia by liquid ionization (LPI) mass spectrometry and MO calculation. The LPI mass spectra showed again the special stablity of (CH3COOH)5(H3O)+ ion in the substitution reactions with ammonia. This substitution reaction seemed to require a certain threshold concentration of ammonia. The results of theoretical calculation with the MNDO-PM3 method revealed that the ring-type structure assumed was more stable than well known catamer-type structures. The results of calculation agreed well with the results obtained from LPI mass spectra. Differences between water and ammonia as a component of clusters are also described.
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  • Electron Impact Mass Spectrometry of Steroidal Dithiolanes
    Gerardo M. CABALLERO, Eduardo G. GROS
    1998 Volume 46 Issue 6 Pages 490-494
    Published: 1998
    Released on J-STAGE: July 20, 2007
    DOIhttps://doi.org/10.5702/massspec.46.490
    JOURNAL FREE ACCESS
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    The EI mass spectrometry data of several steroid dithiolanes are reported. The main fragments were characterized by high resolution mass spectrometric measurements and by linked scan experiments. According to the proposed structures, tentative mechanisms for the formation of important ions are postulated and discussed.
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  • Collisionally Activated Dissociation of 13-Membered Peptides, Ustiloxins, and Phomopsins
    Naoko MORISAKI, Yukiko KOISO, Yukiko MITSUI, Yukiko YAMASHITA, Hisayos ...
    1998 Volume 46 Issue 6 Pages 495-501
    Published: 1998
    Released on J-STAGE: July 20, 2007
    DOIhttps://doi.org/10.5702/massspec.46.495
    JOURNAL FREE ACCESS
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    Collisionally activated dissociation (CAD) of [M+H]+ of ustiloxins and phomopsins was examined. Fragments of ustiloxins were formed by the cleavage of O(1)-C(2) and the peptide chain to form “a”, “b”, “x”, and “y” series ions, and of the C(9)-C(10) bond to form ions “M-Bz” and “b-Bz”. Phomopsins gave the “b” and “y” series ions. The difference may be at least partly explained by different hydrogen bond-forming characteristics of ustiloxins and phomopsins.
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