Characterisation of high pressure quadrupole collision cells possessing direct current axial fields

Abstract

An investigation into the performance characteristics of various designs of novel quadrupolar collision cells possessing axial fields has been undertaken. Among the advantages of such devices possessing conical, tilted or segmented rod geometries is their ability to enable the cell to be operated at high pressure without the deleterious effects of long ion transit times. The collisional focusing benefits of operating at such pressures can therefore be maximised, with increased transmission and resolution of fragment ion spectra. The present work compares the relative merits of the three main designs of axial field cells. The ion optics software package SIMION 6.0 has been utilised to simulate the various designs of cell with user-written programs to model each quadrupolar device, including ion-neutral collisional phenomena. The effect on ion transmission of applying a direct current (DC) offset voltage to the conical and tilted rod cells to generate the axial field is shown. Where possible the simulations and theory are compared to experimental data. Crown Copyright © 1999 National Research Council of Canada.