Mass‐Spectrometrical Investigations of Boron Chelates. VI. Comparison of 70 eV and 15 eV electron impact ionization, chemical ionization and field desorption mass spectra of boron chelates containing CN groups

Boron chelates containing CN groups were investigated by mass spectrometry by three different ionization methods, i. e. 70 eV and 15 eV electron impact ionization (EI), chemical ionization (CI) and field desorption (FD). The extent of formation of the molecular ions and the typical fragmentation patterns of these chelates were compared with each other to provide a definite analytical characterization of these chelates. The EI mode was found to produce molecular ions M+ of very low intensity; even at low electron energy. In all cases, however, the fragment ion (MC6H5)+ was the base peak. For the quasimolecular ion MH+, intense signals could be obtained with the CI‐MS technique when using reactant gases of high proton affinity. The CI and FD methods permit the identification of the chelatized groups containing boron. This BR″C6H4 group is eliminated from MH+ by CI, and from M+ by the FD method respectively. In almost all cases the FD method gives the molecular ion as base peak.