Mass spectrometric investigation on some pyrilium salts by different. Ionization methods and metastable ion studies

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.