Trace Element Microanalysis in Iron Meteorites by Laser Ablation ICPMS
Analytical Chemistry, in press 1999
Andrew J. Campbell and Munir Humayun
Department of the Geophysical Sciences
University of Chicago
Chicago, IL 60637
A laser ablation microanalysis system has been developed that can analyze trace elements with a sensitivity in the ppb range, using a CETAC LSX-200 laser ablation system with a Finnigan Element. This capability has been applied to a set of iron meteorites to demonstrate the laser microprobe's analytical capability for the determination of platinum group elements (PGEs) with a spatial resolution of ~20 µm, comparable to that of dynamic secondary ion mass spectrometry (SIMS). The laser is shown to provide an accurate means of solid sampling for magnetic sector inductively coupled plasma mass spectrometry (ICPMS), allowing the determination of bulk metal composition, chemical zoning within the sample, and depth profiling. Recovery of the chemical zoning in taenite lamellae was achieved for Ru, Rh and Pd, which was not previously possible using SIMS. The methods presented here show that magnetic sector ICPMS can be successfully coupled to a laser ablation system, providing the advantages of higher sensitivity of the sector instrument, low background count rates (<0.1 cps), and flat-topped spectral peaks, while minimizing tradeoff against the speed of data acquisition required to handle the transient signals from the laser ablation system.