Ion‐molecule reactions observed for nitroaromatic compounds in negative ion fast atom bombardment mass spectrometry

Analyses of a series of nitroaromatic compounds using fast atom bombardment (FAB) mass spectrometry are discussed. An interesting ion‐molecule reaction leading to [M + O − H] − ions is observed in the negative ion FAB spectra. Evidence from linked‐scan and collision‐induced dissociation spectra proved that [M + O − H] − ions are produced by the following reaction: M + NO 2 − → [M + NO 2 ] − → [M + O − H] − . These experiments also showed that M −˙ ions are produced in part by the exchange of an electron between M and NO 2 − species. All samples showed M −˙ , [M − H] − or both ions in their negative ion FAB spectra. Not all analytes studied showed either [M + H] + and/or M + ˙ in the positive ion FAB spectra. No M + ˙ ions were observed for ions having ionization energies above ∼9 eV.