Are gas‐phase processes really responsible for the ionization of cyclic acetals by fast‐atom bombardment?

Abstract

AbstractThe mass spectral behavior of a series of substituted 2‐phenyl‐1,3‐dioxolanes has been studied by several ionization techniques in order to gain further insight into the basic ionization mechanisms occurring in the fast‐atom bombardment mass spectrometry. The results obtained show that in chemical ionization, ions of the type [M+H]+ are predominant while [MH]+ ions are observed as important species in electron ionization and fast‐atom bombardment. Comparison of the gas‐phase hydride‐ion affinities of thr chemical ionization reagent gases ammonia and isobutane with those of the loquid matrices glycerol and dithiothereitol/dithioerythritol indicates that the predomionant formation of the [MH]+ ion observed in fast‐atom bombardment by hydride abstraction in the gas phase is improbable. Furthermore, comparison of the electron ionization behavior of the cyclic acetals with that observed under fast‐atom bombardment suggests that the origin of [MH]+ in the latter is not related EI gas‐phase processes.