Investigation of some 2,3-didehydro amino acids by fast ion bombardment,chemical ionization and mass-selected collision-induced dissociation mass spectrometry

Four 2,3-didehydro amino acids were investigated by fast ion bombardment (FIB) and ammonia chemical ionization (NH₃-CI) mass Spectrometry. The protonated molecules formed by the two techniques were mass selected and their respective collision-induced dissociations (CIDs) in the translational energy range 5–200 eV (in the laboratory frame of reference) were investigated. No obvious quantitative differences between the FIB and NH₃-CI mass spectra of the (E)- and (Z)-isomers were observed. Different internal excitation of the protonated molecules formed by the two techniques and the role of CID data in clarifying this particular observation are discussed.