An inductively coupled plasma as an ion source for the determination of trace elements in solutions by mass spectrometry

Abstract

<p>Aerosols of trace elements in solution are injected into an inductively coupled argon plasma to generate a relatively high number density of positive ions derived from the trace elements. A small fraction of these ions is extracted through a pinhole 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 the solvent (1% HNO(,3) in H(,2)O) consists essentially of ArH('+), Ar('+), H(,3)O('+), H(,2)O('+), NO('+), O(,2)('+), HO('+), Ar(,2)('+), Ar(,2)H('+), and Ar('+2). Thus there are few potential interferences from solvent or argon ions above 42 u. The mass spectra of the trace elements studied consists almost entirely of singly charged monatomic (M('+)) or oxide (MO('+)) ions. The various isotopes of those elements studied are detected in the correct relative isotopic abundances. Several trace elements are readily detected in a mass spectrometer scanning mode at 0.05 ug/mL. Analytical calibration curves obtained in a single ion mode are linear over nearly four orders of magnitude with detection limits of 0.001 - 0.01 ug/mL for those elements studied. Rapid sample throughput, direct introduction of solutions, and the capability of direct isotopic determination of trace elements are among the attractive features of this new analytical approach;*USDOE Report IS-T-898. This work was performed under contract W-7405-eng-82 with the Department of Energy and Interagency Agreement IAG-EPA-78-D-X0147 with the Environmental Protection Agency.</p>