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  • 1985-1989  (2)
  • 33  (1)
  • Mass spectrometry, negative ion chemical ionization  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of legal medicine 99 (1988), S. 253-261 
    ISSN: 1437-1596
    Keywords: Antiepileptics, mass spectrometry ; Mass spectrometry, negative ion chemical ionization ; Hydantoins, mass spectrometry ; Antiepileptika, Massenspektrometrie ; Massenspektrometrie, Negativspektren ; Hydantoine, Massenspektrometrie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Es werden Positiv-Ionen-EI-(PIEI)-, Positiv-Ionen-CI-(PICI)-und Negativ-Ionen-CI-(NICI)-Massenspektren von sieben Hydantoinderivaten und Analogen vorgestellt, daneben die wahrscheinlichen Fragmentierungsmuster. Beim PIEI-Modus unterschieden sich die Molekularionen im Hinblick auf die verschiedenen Verbindungen. Eine Spaltung an der Außenregion der beiden Carbonylgruppen war allen Verbindungen gemeinsam. Beim PICI-Modus zeigten alle Verbindungen quasi-molekulare [M+1]+-Ionen. Beim NICI-Modus waren quasi-molekulare [M−1]−-Anionen Basispeaks mit Ausnahme von Trimethadion und Paramethadion. Alle Negativ-Spektren zeigten Anionen bei m/z 42, verursacht durch [NCO]−; diese Peaks erscheinen nützlich zum Screening von Antiepileptika. Weiterhin werden ein Extraktionsverfahren für Antiepileptika aus Humanurin oder -plasma sowie die gaschromatographische Trennung (GC) beschrieben. Diese Verfahren gestatten die Identifizierung mittels GC/MS.
    Notes: Summary Positive ion electron impact (PIEI), positive ion chemical ionization (PICI), and negative ion chemical ionization (NICI) mass spectra of seven compounds of hydantoins and their analogs are presented; their probable fragmentation modes are also presented. In the PIEI mode, intensities of molecular ions differed according to different compounds. Cleavage at outsides of both carbonyl groups was commonly observed for all compounds. In the PICI mode, all compounds showed [M+1]+ quasi-molecular ions constituting the base peaks. In the NICI mode, [M−1]− quasi-molecular anions were the base peaks except for trimethadione and paramethadione. All negative spectra showed anions at m/z 42 due to [NCO]−; these peaks seem useful for screening of antiepileptics. An extraction procedure for the antiepileptics from human urine or plasma, and their separation by gas chromatography (GC), are also presented to serve for their actual identification by GC/mass spectrometry.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0649
    Keywords: 82.50 ; 33
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have been studying the practical CO2-laser-induced13C separation by a two-stage IRMPD process. The IRMPD of natural CHClF2 in the presence of Br2 mainly produced CBr2F2, which was found to be highly enriched with13C. The yield and13C-atom fraction of CBr2F2 were examined as functions of pulse number, laser line, laser fluence, total pressure, and Br2 pressure using a CO2 TEA laser with an output less than 1 J pulse−1 in order to optimize experimental conditions for13C separation. For example, we obtained CBr2F2 at a13C concentration of 55% in the irradiation of the mixture of 100-Torr CHClF2 and 10-Torr Br2 with the laser radiation at a wavenumber of 1045.02 cm−1 and at a fluence of 3.4 J cm−2. The mechanism for the IRMPD is discussed on the basis of observed results. Using 8-J pulses, we were able to obtain 1.9×10−4 g of13C-enriched CBr2F2 (13C-atom fraction, 47%) per pulse under selected conditions. It is possible to produce 90% or higher13C by the second-stage IRMPD of the CBr2F2 in the presence of oxygen.
    Type of Medium: Electronic Resource
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