Mass spectrometric investigation on some pyrilium salts by different. Ionization methods and metastable ion studies
ABSTRACT A series of pyrilium hydrochlorides (Py+ClO−4) have been studied by means of both electron ionization and fast-atom bombardment (FAB) methods. Only for some compounds does electron ionization show the formation of Py+, together with [Py—H]+· ions. Metastable ion data indicate that the former also originate through H· loss when their formation could be explained by loss of perchloric acid through a thermal process directly from the salt. Many fragment ions, related to the original structures, are also detected. In contrast, in FAB conditions, all the compounds show the formation of Py+ without any fragmentation products, proving its effectiveness in the easy identification of the related molecular species. Only by the mass-analyzed ion kinetic energy spectra of Py+ ions can a valid characterization of the compounds under study be achieved.