MASS-SPECTROMETRIC INVESTIGATION ON SOME PYRILIUM SALTS BY DIFFERENT IONIZATION METHODS AND METASTABLE ION STUDIES

A series of pyrilium hydrochlorides (Py+ClO4-) have been studied by me ans of both electron ionization and fast-atom bombardment (FAB) method s. Only for some compounds does electron ionization show the formation of Py+, together with [Py - H]+. ions. Metastable ion data indicate t hat the former also originate through H. loss when their formation cou ld be explained by loss of perchloric acid through a thermal process d irectly from the salt. Many fragment ions, related to the original str uctures, are also detected. In contrast, in FAB conditions, all the co mpounds show the formation of Py+ without any fragmentation products, proving its effectiveness in the easy identification of the related mo lecular species. Only by the mass-analyzed ion kinetic energy spectra of Py+ ions can a valid characterization of the compounds under study be achieved.