High spatial resolution trace element determination of geological samples by laser ablation quadrupole plasma mass spectrometry: implications for glass analysis in volcanic products

摘要

Increasing the spatial resolution of Laser Ablation Inductively CoupledPlasma Mass Spectrometry (LA-ICP-MS) is a challenge in microanalysis ofgeological samples. Smaller sizes for the laser beam will allow for (1) highresolution determination of trace element compositions, (2) accurate estimationof crystal/melt partition coefficients, (3) detailed characterization ofdiffusion profiles, and (4) analysis of fine volcanic glasses. Here, we reportabout the figures of merit for LA-ICP Quadrupole MS down to a spatialresolution of 5 {\mu}m. This study highlights the possibility to achievesuitable limits of detection, accuracy and precision for geological sampleseven at spatial resolutions of the order of 5 {\mu}m. At a beam size of 15{\mu}m precision (measured as one sigma) and accuracy (expressed as relativedeviation from the reference value) are of the order of 10%. At a smaller beamsize of 8um, precision decreases to 15% for concentration above 1.7 {\mu}g g-1.As the beam size is decreased to ~5 {\mu}m, precision declines to about 15% and20% for concentrations above 10 {\mu}g g-1 using 42Ca and 29Si as internalstandard, respectively. Accuracy is better or equal to 10% and 13 % at beamsizes of 15 and 10 {\mu}m respectively. When the spatial resolution isincreased to 8 {\mu}m, accuracy remains better than 15% and 20% for 42Ca and29Si as internal standard, respectively. We employed such high-resolutiontechniques to volcanic glasses in ash particles of the 2010 Eyjafjallaj\"okulleruption. Our results are well consistent with the previously reported dataobtained at lower spatial resolution, supporting the reliability of the method.