Quantitative analysis of trace elements in geological materials by laser ablation ICPMS: Instrumental operating conditions and calibration values of NIST glasses

A UV laser ablation microprobe coupled to an ICPMS has been used to determine trace element concentrations in solids with a spatial resolution of less than or equal to 50 microns and detection limits ranging from less than or equal to 2 mu g/g for Ni to less than or equal to 50 ng/g for the REE, Th, and U. Experiments designed to optimize laser operating conditions show that pulse rates of 4 Hz produce a steady state signal with less inter-element fractionation per unit time than higher pulse rates (10-20 Hz). Comparisons of laser microprobe analyses of garnets and pyroxenes using the NIST 610 and 612 glasses as calibration standards, with proton microprobe, solution ICPMS, INAA and XRF data show no significant matrix effects. Laser microprobe analyses of the NIST 610 and 612 glasses have a precision and accuracy of 2-5%, and error analysis shows that counting statistics and the precision on the internal standard concentration accounts for the analytical uncertainty. The NIST glasses appear to be useful calibration materials for trace element analysis of geological materials by laser microprobe.