Exploration of the utility of CF3⁺ as a reagent for chemical ionisation reaction mass spectrometry

The utility of CF 3 + as a chemical-ionisation reagent for the identification of volatile organic compounds (VOCs) is explored. CF 3 + and CF 2 H + , produced from the discharge of CF 4 , 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 CF 3 + with a functionally varied range of VOCs, under 100Td and 120Td 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. CF 3 + acts as a Lewis acid, a strong electrophile with aromatics and nitriles. In VOCs with carbonyl groups, CF 3 + 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 C 5 and becoming progressively more significant by C 7 .A brief comparison is made with the comparable H 3 O + reactivity. From the comparison between CF 3 + and H 3 O + , it is clear that CF 3 + is a "more aggressive" reagent ion but offers utility in terms of distinctive mass shifts with certain functional groups.