An atmospheric-pressure ionization mass spectrometer/mass spectrometer

Abstract

This report gives data about the construction and performance of an atmospheric-pressure ionization source which provides positive or negative ions for a tandem mass spectrometer. The ions can be mass-analyzed in one or both of two Balzer quadrupole mass-analyzers. In addition, the ions can be fragmented by collisionally activated decomposition in one or both of two collision cells. All ions from the source pass through the first collision cell, and the degree of dissociation is controlled by selection of the ion energy. Ions of a chosen mass selected by the first mass-analyzer are passed through the second collision cell, where the degree of dissociation can be varied by choice of ion energy and/or collision-gas pressure. In order better to understand these variables and their effects on the spectra, data are presented about the energy spreads of the ions entering into different sections of the spectrometer, about the collision efficiencies of the two collision cells, and about the effects of the RF fields on the fragmentation of the ions. The identification of an odor constituent in an organophosphorothioate is described as an example of the utility of this tandem mass spectrometer.