The objective of this project is research on and development of new mass spectral techniques in order to provide innovative and/or more rapid solutions to problems involving (1) chemical structure determination, (2) complex mixture analysis and (3) measurement of trace components in biological systems. Fast atom bombardment mass spectrometry and combined liquid chromatography-mass spectrometry remain the techniques of current interest. Reversed phase, paired-ion techniques are being developed for combining micro-column liquid chromatography with continuous-flow fast atom bombardment ionization for the on-line liquid chromatography-mass spectrometry analysis of nucleosides. Use of acidic, anionic surfactants during static fast atom bombardment greatly enhances sensitivity for analysis of cytosine nucleosides such as cyclopentenyl cytosine. The structure of an in vitro metabolite of benzene-3-carboxamide riboside, which is a potent inhibitor of inosine monophosphate dehydrogenase, has been confirmed as the adenine dinucleotide conjugate by negative ion fast atom bombardment mass spectrometry.