Positive and negative ion desorption chemical ionization of some penicillins

Abstract

The ammonia positive ion desorption chemical ionization and methane negative ion desorption chemical ionization mass spectra of five commercially available penicillins have been studied. In every case ions characteristic of the molecular weight were obtained together with diagnostically significant fragment ions. As well as the known fragmentation pathways observed under electron impact conditions a significantly different fragmentation pathway was observed using negative ion desorption ionization. The reproducibility of the spectra obtained contrasts markedly with previous reports on the mass spectra of penicillin free acids.