Evaluating the accuracy and limitations of the Geotek X-ray fluorescence core scanner fundamental parameter method for the estimation of elemental concentrations in sediment samples

Abstract

X-ray fluorescence core scanners (XRF-CSs) are capable of performing high-resolution, nondestructive, and rapid chemical analyses of sediment samples. As such, they have become an essential part of many geological studies, including palaeoenvironmental reconstructions and geohazard assessments, with their applications expanding each year. The primary limitation of XRF-CSs is that, by default, they provide elemental intensities as outputs, which often cannot quantitatively reflect the chemical composition of samples. To address this limitation, the latest generation of Geotek XRF-CSs provides elemental concentrations estimated from element intensities using the fundamental parameter (FP) method as its default output. In this study, we present the first comprehensive evaluation of Geotek XRF-CS-derived estimates by comparing them to certified (‘true’) elemental concentrations reported for 17 various powdered certified reference materials, which are considered representative of sediment samples and are mixtures of air, water, mineral, and amorphous phases. Our goal was to assess the reliability of the instrument's default output under various measurement setups, including different apparatus settings and both wet and dry sample conditions. We found that Geotek XRF-CS estimates are mostly linearly related to true elemental concentrations. However, the latter remain significantly underestimated, particularly when the analysed sample is wet. The relationship between the true concentration and the instrument's estimates becomes proportional when the results are expressed as elemental log ratios, regardless of the measurement setup. In this regard, Geotek XRF-CS estimates resemble the element intensities provided by other XRF-CS systems. We conclude that Geotek XRF-CS estimates are suitable for reliably assessing the relative variability in the chemical composition of sediment samples and its uncertainty. However, their application to fully quantitative analysis may be limited.