DOUBLE CATIONIZATION WITH ALKALI IONS IN LIQUID SECONDARY-ION MASS-SPECTROMETRY

A unique double cationization process produces a singly charged ion (M +2Met) in the LSIMS mass: spectra of nitro-group containing organic m olecules. In contrast to the usual replacement of a hydrogen by the se cond metal atom to form (M+2Met-H)(+), there is no loss of hydrogen in the doubly cationized species. Since two positively charged metal ion s are added to the neutral sample molecule, a one-electron reduction s tep must also be invoked. Product ion MS/MS spectra suggest that both metal cations are associated directly with the nitro group. For the ni tro-group containing compounds studied, the double cationization produ ct ion is preferentially formed with cesium and any other group I meta l ion.