Fundamental studies of the sampling process in an inductively coupled plasma mass spectrometer-II: Ion kinetic energy measurements

Abstract

Retarding-plate analysis was used to monitor kinetic energies of argon and analyte ions in the second and third stages of a three-stage ICP-MS instrument. In these studies, forces that influence ion movement (i.e. gas-kinetic or ion-ion interactions) and their relative strengths are deduced from retarding-potential curves. Coulombic interactions among ions have been found to be so strong in the mass spectrometer second stage that they can overpower influences on ion movement imparted by gas-kinetic forces. In contrast, ion movement in the third stage was found to be influenced less by these coulombic interactions than in the second stage. However, ion-ion interactions could be intentionally exaggerated in the third stage by increasing ion flux. Results from these experiments were useful not only in identifying the forces that influence ion movement but also in the development of a new qualitative ion-transport model for a three-stage ICP-MS instrument