Inductively coupled argon plasma as an ion source for mass spectrometric determination of trace elements

Abstract

Solution aerosols are injected into an inductively coupled argon plasma (ICP) to generate a relativly high number density of positive ions derived from elemental constituents. A small fraction of these ions is extracted through a sampling orifice into a differentially pumped vacuum system housing an ion lens and quadrupole mass spectrometer. The positive ion mass spectrum obtained during nebulization of a typical solvent (1% HNO/sub 3/ in H/sub 2/O) consists mainly of ArH/sup +/, Ar/sup +/, H/sub 3/O/sup +/, H/sub 2/O/sup +/, NO/sup +/, O/sub 2//sup +/, HO/sup +/, Ar/sub 2//sup +/, Ar/sub 2/H/sup +/, and Ar/sup 2 +/. The mass spectra of the trace elements studied consist principally of singly charged monatomic (M/sup +/) or oxide (MO/sup +/) ions in the correct relative isotopic abundances. Analytical calibration curves obtained in an integration mode show a working range covering nearly 4 orders of magnitude with detection limits of 0.002 to 0.06 ..mu..g/mL for those elements studied. This approach offers a direct means of performing trace elemental and isotopic determinations on solutions by mass spectrometry.