Determination of major and trace elements in silicate rock fused with lithium metaborate using laser ablation-inductively coupled plasma-mass spectrometry†

Abstract

In this study, a novel lithium metaborate fusion technique using a homemade fusion furnace and graphite crucibles was developed to produce homogeneous glasses from silicate rock powder. The glasses were then analyzed for both major and trace element concentrations by LA-ICP-MS. The parameters of the ratio of flux-to-sample, melting temperature and time, and closed fusion were optimized. It was found that homogeneous glasses could be obtained, and the loss of Pb was effectively suppressed at a low melting temperature and short time (900 or 950 °C for 5 min) in closed fusion. Compared to Pt or Pt–Au crucibles in the traditional flux fusion method, homemade graphite crucibles are more economical and omit the need of any releasing agent because the bottom curve design allows the melt to shrink into a bead for easy removal. Accurate results by LA-ICP-MS can be directly obtained by applying a quantitative calibration strategy using 100% oxide normalization, which offers a solution for unknown sample analysis without the prior determination of the concentration of an internal standard element. The analytical results of 42 major and trace elements in 5 USGS silicate rock reference materials (covering mafic to felsic rock types) using the developed LiBO₂ fusion technique are consistent with the reference values within 10% for most elements, and analytical precision (RSD) is within 10% for most elements. The developed method is simple for preparing homogeneous glasses from rock powders, which displays great potential for the rapid and accurate determination of mass fractions of major and trace elements in silicate rocks using LA-ICP-MS.