Routine quantitative multi-element analysis of sulphide minerals by laser ablation ICP-MS: Standard development and consideration of matrix effects

Abstract

<p>The paper describes a calibration standard for quantitative <i>in-situ</i>multi-element analysis of sulphide minerals by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Standard STDGL2b2 is a mixture of 25% Zn concentrate and 75% pyrrhotite doped with a number of additional traceelements and fused into an X-ray fluorescence (XRF) glass disk. The homogeneityof the disk has been tested for the 55 elements of interest. All elements except Se, Tl, Au and Pt are homogenous (< 5% variation). Accurate analysis for the above four elements requires averaging multiple analyses of the standard. Element concentrations in STDGL2b2 were quantified by XRF and standard solutionICP-MS using a Finnigan Element and an Agilent 4500 mass-spectrometers.</p><p>For the analysis of pyrite, pyrrhotite, chalcopyrite, galena and sphalerite,analytical errors caused by matrix-dependent fractionation have been evaluated by analysing five pressed-powder pellets.. The compositions of the powders have been analysed by XRF and solution ICP-MS. When Fe or Pb can be used as the internal standard, errors for most elements are < 15%, but reach up to 50% for W, Zn and Cd, requiring correction factors to be introduced. However, when Zn is used as the internal standard, significant correction factors are required for most elements.</p><p>Comparison of the results obtained with two different laser microprobes, a solidstate 213 nm and an excimer 193 nm, indicates that either is well suited forLA-ICP-MS analysis of sulphide minerals using STDGL2b2 as the calibrationstandard.</p>Use of STDGL2b2 significantly improves accuracy of sulphide analysis byLA-ICP-MS compared to silicate reference materials, such as the NIST 600 series.