Field ionization mass spectrometry—I. Nucleosides

The field ionization mass spectra of a series of nucleosides are reported, and compared with spectra obtained by conventional electron‐impact ionization. The latter are complex, with structurally significant molecular ion and sugar cleavage peaks often of low intensity or completely absent. In contrast, the field ion spectra are extremely simple, with all except guanosine (highest mass peak [M — 18]) showing intense molecular ion peaks, and the characteristic sugar (S) and base (B + H) cleavage products as the only other important fragments.