Rapid Determination of REEs, PGEs, and Other Trace Elements in Geological and Environmental Materials by High Resolution Inductively Coupled Plasma Mass Spectrometry

Methodologies were designed and developed using magnetic sector high resolution inductively coupled plasma mass spectrometry (IIR-ICP-MS) for the fast, reliable, and accurate determination of different sets of geochemically significant trace elements (at sub-ng/g to pg/g levels) including rare earth elements (REEs) and platinum group elements (PGEs) in a variety of geological materials for their application in advanced geochemical studies. In the case of trace elements (including REE) in rock, mineral, soil, and sediment samples, about 50 mg each of the samples was dissolved in Savillex (R) pressure decomposition vessels by utilizing a mix of hydrolluoric-intricperchloric adds. Procedural blanks were prepared in a similar way. Trace elements were determined in water samples directly after filtration, acidification, and appropriate dilution with Xe-129 and Xe-132 as the internal standards. NiS fire assay and Te co-precipitation methods were used for the separation and pre-concentration of the PGEs and Au from the rock matrix (similar to 10 g properly homogenized samples) before their determination by HR-ICP-MS. Synthetic multi-element solutions (1, 10, and 100 ng/mL) were used for the preparation of calibration graphs. In order to validate these methods, a series of international geo-standards starting from acidic to ultra-basic rock, soil, sediment, stream sediment, and water reference samples were analyzed after optimizing the instrumental parameters. Most spectroscopic interferences were removed by choosing optimum resolution (300R) settings for each element or group of elements for the separation of the interfering peaks, such as doubly charged ions and polyatomic species, from the analyze peaks of interest. The matrix effects were minimized by analyzing very diluted samples. Extremely close agreement was found between the data sets by IIR-ICP-MS with certified values wherever data available for comparison. The precisions obtained in this study were <2% RSD for the majority of elements with comparable accuracy, confirming that the methodologies designed and developed in this study are suitable for obtaining precise data suitable for high precision geochemical, mineral exploration, and environmental studies.