A systematic study of instrumental parameters affecting electron capture negative ion mass spectra

Abstract

The problem of reproducing electron capture negative ion mass spectra has been addressed by studying parameters that affect negative ion abundance on a Hewlett Packard 5985B mass spectrometer. Parameters affecting negative ion formation in the ion source, such as ion source temperature, pressure, sample concentration and electron energy, were studied in conjunction with the effect of lenses used to extract and transmit ions to the quadruples. From these experiments, it was found that, in addition to ion source temperature, the ion focus potential has the most dramatic effect on the abundance of molecular ions relative to fragment ions like Cl−. With proper control, it was found that the relative abundance of ions from decafluorotriphenylphosphine could be reproduced over a period of one year.