Characteristics of an ion funnel as ion guide in an inductively coupled plasma mass spectrometer

The characteristics of an electrodynamic ion funnel as an alternative ion optics element for inductively coupled plasma mass spectrometry (ICPMS) were investigated in this work. Therefore the ion lens of a conventional ICPMS system has been removed and a custom made ion funnel was installed instead. The effects of the radiofrequency-amplitude and frequency and the axial funnel potential on the ion transmission have been investigated for different configurations. Under optimum conditions the ion current was in average 10-fold lower than with the un-modified instrument, while CeO+/Ce+ ratios increased ten-fold. Nonetheless, confinement of atomic ions from the ICP inside the ion funnel could be achieved by optimizing radiofrequency and DC potentials at the funnel electrodes as indicated by an increase in the ion signal intensities relative to the field-free case. With the ion funnel being partially enclosed, gases, such as N-2 and H-2, could be introduced which can reduce the abundance of Ar+ and Ar-based polyatomic ions by one (H-2) to three (N-2) orders of magnitude. Based on these experiments, however H-2 would be more favorable since it did not affect the transmission of low m/z analyte ions to a great extent. (c) 2012 Elsevier B.V. All rights reserved.