LASER-ABLATION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY (LA-ICP-MS) - A RAPID TECHNIQUE FOR THE DIRECT, QUANTITATIVE-DETERMINATION OF MAJOR, TRACE AND RARE-EARTH ELEMENTS IN GEOLOGICAL SAMPLES

A Nd:YAG laser in fixed-Q (free running) mode coupled to an inductively coupled plasma mass spectrometer was used to directly analyse pressed powder pellets of seven well-characterised silicate rock reference materials (AGV-1, BIR-1, DNC-1, G-2, NIST 2704, SCo-1 and W-2). The multielement limits of detection (LOD) were in the range 0.05-13 mug g-1 but with a majority of values better than 0.1 ug g-1. Using a narrow range scan LOD for the rare-earth elements (REE's) were between 11-84 ng g-1. Relative responses for the major elements indicate that the chemistry and mineralogy of individual rock samples influence the ablation behaviour, and that samples with very similar chemical and mineralogical compositions exhibit similar elemental responses. The accuracy of major-element determinations, for the materials studied, was generally better than +/- 5% with a precision of 10% RSD. First-row transition elements, incompatible elements and, in particular, REE's displayed a high degree of accuracy, with precision of generally < 10% RSD. Providing that samples and standards are matched both in terms of bulk chemistry and mineralogical composition, fully quantitative determination of major and trace elements is possible. Laser ablation ICP-MS is therefore not only a rapid alternative method of elemental determination, but is also particularly applicable for a number of elemental groups whose quantitative determination may be complicated if it is necessary to dissolve samples prior to analysis.