Electron capture negative ion chemical ionization mass spectrometry of derivatized chlorophenols and chloroanilines.

Abstract

The electron capture negative ion chemical ionization mass spectra of electrophoric derivatives (perfluoroacyl, pentafluorbenzyl, pentafluorobenzoyl, 3,5-bis(trifluoromethyl)-benzoyl, and (pentafluorophenyl)methanimine) of chloro-substituted phenols and anilines have been investigated. The formation of analyte-specific anions in the spectra of the derivatives is strongly influenced by the nature of the electrophoric group and the summed electron-donating or -with-drawing properties of the aromatic ring substituents. Hammett linear free energy relationships can be used to predict the stability of molecular anions, the direction of fragmentation pathways, and the usefulness of a given derivative for analytical purposes by using selective-ion monitoring. The influence of ion source temperature on the ionically induced dissociation of the derivatives was examined. The relative molar responses of different derivatives under conditions of GC-negative ion chemical ionization mass spectrometry and GC-electron capture detection were comparable.