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  • 1
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Decafluorotriphenylphosphine has been shown to be a useful compound for checking the overall performance of gas chromatography mass spectrometry systems in the electron impact (EI) mode of operation. This paper reports the results obtained on several compounds evaluated for their utility in checking mass spectrometric performance in the chemical ionization mode of operation. The ideal compound should be capable of being admitted to the ion source from both the solid probe inlet and the gas chromatographic inlet, should respond in both positive ion and negative ion modes, should have as high a molecular weight as possible (preferably 〉 400), should generate an abundant ion indicative of the molecular weight and several significant fragment ions covering a wide mass range in positive ion chemical ionization (CH4), and should generate less fragmentation in positive ion chemical ionization with less exothermic reagent gases. Following an evaluation which included such compounds as benzophenone, decafluorotriphenylphosphine, octacosane (n-C28H58), triacontane (n-C30H62), and methyl stearate, lauryl laurate (mol. wt = 368) was found to offer the best compromise in satisfying these criteria.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1987), S. 342-347 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Imidazolin-4-ones are a new class of herbicides which contain both an amide and amino nitrogen in a five-membered ring. During the manufacturing process, it is possible to methylate either nitrogen. This presented an interesting analytical problem in distinguishing between the two N-methylated derivatives of ASSERT® (a mixture of 6-(4-isopropyl-4-methyI-5-oxo-2-imidazolin-2-yl)- m- and p-toluic acid methyl esters) at low levels in a complex mixture. After developing a high-performance liquid chromatography method for separating and isolating components in the mixture, mass spectrometric techniques, which included electron impact (EI) and collisional activation decomposition (CAD), were used to distinguish between two isomeric N-methylated derivatives. The data from the El and CAD experiments enabled amidomethyl and aminomethyl structures to be assigned. Accurate mass measurements and proton nuclear magnetic resonance spectroscopy were used to support the assignments.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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