Formation of protonated phosphonates in the ion‐trap mass spectrometer under electron impact conditions

Abstract

Abstract The gas‐phase behaviour of organophosphorus compounds such as diethylmethylphosphonate 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 adduct ions such as 2M +· and [2M + H] + . The keto‐to‐enol‐like isomerization of the molecular M +· ion seems to favour proton transfer to neutral M species and a “self chemical ionization” ion is observed with corresponding fragment ions.