Possible Pitfalls in the Analysis of Minerals and Loose Materials by Portable XRF, and How to Overcome Them

Abstract

Portable X-ray fluorescence spectroscopy is now widely used in almost any field of geoscience. Handheld XRF analysers are easy to use, and results are available in almost real time anywhere. However, the results do not always match laboratory analyses, and this may deter users. Rather than analytical issues, the bias often results from sample preparation differences. Instrument setup and analysis conditions need to be fully understood to avoid reporting erroneous results. The technique’s limitations must be kept in mind. We describe a number of issues and potential pitfalls observed from our experience and described in the literature. This includes the analytical mode and parameters; protective films; sample geometry and density, especially for light elements; analytical interferences between elements; physical effects of the matrix and sample condition, and more. Nevertheless, portable X-ray fluorescence spectroscopy (pXRF) results gathered with sufficient care by experienced users are both precise and reliable, if not fully accurate, and they can constitute robust data sets. Rather than being a substitute for laboratory analyses, pXRF measurements are a valuable complement to those. pXRF improves the quality and relevance of laboratory data sets.

Vectors to ore in replacive volcanogenic massive sulfide (VMS) deposits of the northern Iberian Pyrite Belt: mineral zoning, whole rock geochemistry, and application of portable X-ray fluorescence

“…Prior to sample analysis, an assessment of the performance of our device was made, particularly on the effect of equipment warm-up, measuring time, distance to sample, water content, and number of analyses per sample following the examples and recommendations of previous works (e.g. Ge et al, 2005;Hall et al, 2013Hall et al, , 2014Bourke and Ross, 2015;McNulty et al, 2020;Laperche and Lemière, 2021); results and discussion of these aspects are presented in Sect. S1.3.…”

On-Site Analyses as a Decision Support Tool for Dredging and Sustainable Sediment Management

“…2.2.1. On-Site Analytical Technologies Used in the Different Case Studies pXRF Among currently available technologies for sediments, portable X-ray fluorescence (pXRF) is one of the best known, and its operation is straightforward [18][19][20]. It allows routine measurements for most of the major elements (Ca, Fe, K, Ti, Mn, and, often with lesser accuracy or higher deviation, Si, Al, P, S and Cl) and for many trace elements (often contaminants: Pb, Zn, Cu, As, Sb, Cr, V, etc).…”

“…Bias and shift between on-site and laboratory analyses for sieved and raw samples. Modified from[18].…”

Characterization of Wall Paintings of the Harem Court in the Alhambra Monumental Ensemble: Advantages and Limitations of In Situ Analysis

“…Nevertheless, handheld XRF commercial instruments fitted with factory in-built calibrations that provide direct conversion of the obtained spectra into elemental constituent concentrations without user interaction are proliferating. Most of these semi-quantitative determinations are based on mathematical algorithms such as Fundamental Parameters (FP) to correct for matrix effects [ 28 , 29 ]. These semi-quantitative results have been reported to lack enough analytical accuracy, particularly in the case of artworks, where the minimum requirements of sample homogeneity do not apply [ 29 , 30 ].…”

“…Most of these semi-quantitative determinations are based on mathematical algorithms such as Fundamental Parameters (FP) to correct for matrix effects [ 28 , 29 ]. These semi-quantitative results have been reported to lack enough analytical accuracy, particularly in the case of artworks, where the minimum requirements of sample homogeneity do not apply [ 29 , 30 ]. However, their usefulness to provide information of tendencies, groupings, and correlations will be here evaluated by using a multivariate exploratory tool as Principal Component Analysis (PCA).…”