Inductively coupled plasma-mass spectrometric analysis of geological samples: A critical evaluation based on case studies

Inductively coupled plasma-mass spectrometry (ICP-MS) is a relatively new and promising analytical technique, with the potential to be an excellent analytical tool in earth sciences. In this paper, we provide an overview of the use of ICP-MS in earth sciences, based on our experience with this technique over the last five years. This paper discusses a variety of calibration techniques, chemical separation and preparation procedures, followed by various data acquisition protocols to determine a variety of elements in samples ranging from mineral separates, Fe formations, to ultramafics. The procedures evaluated include methods for the determination of 33 trace elements using a modified standard addition procedure and its adaptation to mg quantities of mineral separates; a procedure for the determination of Y, all the rare-earth elements (REE), and Th using a Na₂O₂ sinter, with quantification using internal standards; and techniques for the determination of very low-level REE in ultramafic samples using ion-exchange concentration. To solve dissolution difficulties involved in Fe formation samples a procedure using oxalic acid to complex the Fe is demonstrated on the reference material IF-G. Precious-metal determination of all the Pt-group elements along with Re and Au is summarised. The application of ICP-MS to isotope ratios is discussed with reference to the determination of ¹⁴⁷Sm ¹⁴⁴Nd and Pb-Th-U isotope ratios. From the results of these studies, it is clear that the future for ICP-MS in earth sciences is very promising.