Rapid determination of REEs and other trace elements in geological samples by microwave acid digestion and ICP-MS

A method is described for the chemical decomposition and determination of 20 geochemically significant trace elements and all 14 rare earth elements in a few international geological reference materials using microwave acid digestion and inductively coupled plasma mass spectrometry (ICP-MS). Samples of about 50 mg were dissolved using a microwave digestion procedure. 103 Rh was used as an internal standard, and a 0.02% solution of matrix-matched geological reference samples was used as the calibration standard. Detection limits for most of the elements are in ppt and sub-ppt range. The data obtained for several rock reference materials were found to be in good agreement with the certified data. The precisions achieved were < 5% RSD with comparable levels of accuracy; in most cases suggesting that the data obtained by ICP-MS are best suited for high precision geochemical studies. The ability to generate semiquantitative analysis data for nearly 70 elements in about 90 sec was demonstrated using a certified reference material. The accuracy and precision of the results are in most cases well within the 20% RSD of the certified values. For the semi-quantitative analysis, a 200-ng/mL multi-element solution was used for calibration. This ability should be particularly useful when totally unknown samples have to be characterized or when concentrations of certain trace elements have to be recorded in a large number of samples.