QUANTITATIVE-ANALYSIS OF TRACE-ELEMENTS IN GEOLOGICAL-MATERIALS BY LASER-ABLATION ICPMS - INSTRUMENTAL OPERATING-CONDITIONS AND CALIBRATIONVALUES OF NIST GLASSES

A UV laser ablation microprobe coupled to an ICPMS has been used to de termine trace element concentrations in solids with a spatial resoluti on of less than or equal to 50 microns and detection limits ranging fr om less than or equal to 2 mu g/g for Ni to less than or equal to 50 n g/g for the REE, Th, and U. Experiments designed to optimize laser ope rating conditions show that pulse rates of 4 Hz produce a steady state signal with less inter-element fractionation per unit time than highe r pulse rates (10-20 Hz). Comparisons of laser microprobe analyses of garnets and pyroxenes using the NIST 610 and 612 glasses as calibratio n 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 er ror analysis shows that counting statistics and the precision on the i nternal 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.