Application of Fast Atom Bombardment Mass Spectrometry/Mass Spectrometry to Structural Analysis

Abstract

Fast atom bombardment (FAB) mass spectrometry in conjunction with tandem mass spectrometry (MS/MS) provides the unambiguous molecular weight and structural information about many kinds of organic compounds. FAB often yields molecular ion species with little fragmentation, and therefore, gives molecular weight information but little structural information. Collisionally activated dissociation (CAD) spectra, obtained with an MS/MS instrument, of the selected ion species can provide fragmentation information which can be used for structural elucidation. Occasionally, metastable ion (MI) spectra, obtained with an MS/MS spectrometer, of the quasi-molecular ion (QM+) or the fragment ions give more useful and convenient information to determine the structure of the target compounds. Since the reproducibility of FAB MS/MS spectra is excellent, slight differences in relative daughter ion intensities of structural isomers afford an assignment, which is often not possible from the conventional mass spectrum alone. In this work, capabilities of FAB MS/MS for structural isomer differentiation and structure determination in the natural products field are demonstrated.