Benzylammonium thermometer ions: Internal energies of ions formed by low temperature plasma and atmospheric pressure chemical ionization

Edward R. Stephens, Morphy Dumlao, Dan Xiao, Daming Zhang, William A. Donald

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    19 Citations (Scopus)

    Abstract

    The extent of internal energy deposition upon ion formation by low temperature plasma and atmospheric pressure chemical ionization was investigated using novel benzylammonium thermometer ions. C–N heterolytic bond dissociation enthalpies of nine 4-substituted benzylammoniums were calculated using CAM-B3LYP/6-311++G(d,p), which was significantly more accurate than B3LYP/6-311++G(d,p), MP2/6-311++G(d,p), and CBS-QB3 for calculating the enthalpies of 20 heterolytic dissociation reactions that were used to benchmark theory. All 4-substituted benzylammonium thermometer ions fragmented by a single pathway with comparable dissociation entropies, except 4-nitrobenzylammonium. Overall, the extent of energy deposition into ions formed by low temperature plasma was significantly lower than those formed by atmospheric pressure chemical ionization under these conditions. Because benzylamines are volatile, this new suite of thermometer ions should be useful for investigating the extent of internal energy deposition during ion formation for a wide range of ionization methods, including plasma, spray and laser desorption-based techniques.
    Original languageEnglish
    Pages (from-to)2081-2084
    Number of pages4
    JournalJournal of the American Society for Mass Spectrometry
    Volume26
    Issue number12
    Early online dateOct 2015
    DOIs
    Publication statusPublished - Dec 2015

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