FORMATION OF PROTONATED PHOSPHONATES IN THE ION-TRAP MASS-SPECTROMETER UNDER ELECTRON-IMPACT CONDITIONS

The gas-phase behaviour of organophosphorus compounds such as diethylm ethylphosphonate towards electron impact (EI) ionization occurring in a quadrupole ion-trap instrument is investigated. If all ions observed in conventional EI mass spectra are detected, ion/molecule reactions are seen to occur leading to formation of protonated molecules and add uct ions such as 2M(+.) and [2M+H](+). The keto-to-enol-like isomeriza tion of the molecular M(+.) ion seems to favour proton transfer to neu tral M species and a ''self chemical ionization'' ion is observed with corresponding fragment ions.