Abstract
The utility of CF3 + as a chemical-ionisation reagent for the identification of volatile organic compounds (VOCs) is explored. CF3 + and CF2H+, produced from the discharge of CF4, have been used as chemical ionization (CI) precursor ions with a representative functional mixture of VOCs in Chemical Ionisation Reaction Mass Spectrometry (CIR-MS), a multi-reagent analogue of PTR-MS. Reacting CF3 + with a functionally varied range of VOCs, under 100 Td and 120 Td accelerating electric fields (E/N), produced markedly different fragmentation patterns. Whereas hydride ion transfer was found to be the main reaction mechanism with n-alkanes. CF3 + acts as a Lewis acid, a strong electrophile with aromatics and nitriles. In VOCs with carbonyl groups, CF3 + forms an intermediate complex leading to the substitution of oxygen by fluorine. Target VOCs with longer alkyl chains in general show greater fragmentation, starting at C5 and becoming progressively more significant by C7. A brief comparison is made with the comparable H3O+ reactivity. From the comparison between CF3 + and H3O+, it is clear that CF3 + is a “more aggressive” reagent ion but offers utility in terms of distinctive mass shifts with certain functional groups.