Abstract
Accuracy and repeatability of analytical results obtained by laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) critically depends on the availability of calibration standards, which should ideally have a matrix composition very close to the samples being analyzed. The preparation of synthetic obsidian standards (SOS) is described in this work, their minor and trace element composition (>40 elements), determined by solution nebulization ICP-MS and inductively coupled plasma optical emission spectrometry is presented and their performance in the quantitative and semiquantitative analysis of obsidians by LA-ICP-MS is discussed. Due to matrix matching of SOS and natural obsidians, internal standardization of the analyte intensities by 27Al or 29Si had no significant effect on the final results. Good analytical curves ( r 2>0.995) were obtained with the SOS series, permitting quantitative determination of a large number of trace elements in geological and archaeological samples with repeatabilities typically between 5 and 10% and adequate accuracies, as shown by the generally good agreement between solution nebulization and laser ablation data for the same samples. Results obtained in the fast semiquantitative mode of calibration were in most cases statistically not different from those obtained by the quantitative mode. This, for the routine analysis of a large number of samples attractive feature, was achieved by the use of 47 quantified elements in SOS for updating of the response factors. An example for the application of analytical methodologies introduced in this work is shown in provenance studies of archaeological obsidian artifacts from Ecuador.
Published Version
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