Evaluation and calibration of a Field Portable X-Ray Fluorescence spectrometer for quantitative analysis of siliciclastic soils and sediments

Abstract

This paper documents the evaluation of a Field Portable X-Ray Fluorescence spectrometer (FP-XRF) as a bench top laboratory unit with regard to quantitative elemental analysis of siliciclastic soils and sediments. With the end-user in mind, we outline a calibration scheme that offers significant improvement in data quality over the manufacturer's calibration. Our calibration approach is based on Standard Reference Materials (SRMs) as calibration standards, the use of least-squares regression techniques that allow for uncertainty in both x and y data (i.e., type II linear regression), propagation of error with respect to predicted concentrations, and goodness of fit evaluation. Data presented include the repeated analysis of numerous standard reference sediments and soils, which are used to evaluate the instrument response to changes in concentration, signal stability over the course of ∼1 year, and calibration model suitability. We present Hudson River estuary sediment data along with independent confirmatory analyses as a demonstration. Our results for the estuarine sediments are in very good agreement with independent laboratory analyses, indicating that the FP-XRF is comparable to traditional laboratory instrument/analytical techniques, and capable of providing high quality data for numerous elements.