Calibration of a portable X-ray fluorescence spectrometer in the analysis of archaeological samples using influence coefficients

Abstract

This paper responds to the expanding interest in archaeology in the use of portable X-Ray fluorescence (pXRF) technologies. Accurate analysis using pXRF requires correction for absorbance and secondary enhancement of the excited element X-rays by the other elements present. Several correction methods are widely used, including fundamental parameters, influence coefficients, Compton ratioing, multi-variate statistical analysis, and dilution. Most pXRF calibrations use either fundamental parameters or multi-variate statistics. However, influence coefficients are known to be the most certain calibration method for XRF analysis of geological materials. Portable XRF calibrations using influence coefficients in the analysis of obsidian, flint, mudbrick, and sediment have far less bias and include a wider range of elements (Mg through Ce) than multi-variate statistical or fundamental parameter calibrations using beam filtered spectra. Bias v. wavelength dispersive XRF data using influence coefficients is mostly less than 1 % for obsidian and flint, and less than 2 % for mudbrick and sediment, in contrast with the large biases (up to 36 %) found using fundamental parameters or multi-variate statistical methods.

Multiple sources: The pXRF analysis of obsidian from Kenan Tepe, S.E. Turkey

“…While pXRF instruments have gained frequent use in archaeology, both for analysis of obsidian and other materials, this has often been driven by accessibility, ease of use and cost. Although these are very significant advantages, there have been less rigorous attempts to optimise the analytical workflow or to gauge measurement uncertainty (Conrey et al 2014;Speakman and Shackley 2013;Lynch et al 2016).…”

Characterizing crystalline volcanic rock (CVR) deposits from Galiano Island, B.C., Canada: Implications for lithic material procurement at the Dionisio Point locality

“…Conrey et al, 2014). Identification of crystalline volcanic rocks is based on SiO 2 content, which is a compound too light to be detected reliably by pXRF.…”

Geochemical Characterization of Bolivian Formative Earthen Architecture by Wavelength‐Dispersive X‐ray Fluorescence

“…Although there are distinct geological contexts across the Taraco Peninsula (Swedish Geological AB, 1994; Figure 1, Table I), nondestructive EDXRF could not discriminate between different areas of the Peninsula, or distinguish clays that were well differentiated in the field by color. In addition, WDXRF assays elements individually without the spectral overlap and interference found in EDXRF, which is exacerbated in portable machines unless effectively corrected (Conrey et al, 2014). The pretreatment developed by Johnson, Hooper, and Conrey (1999) as adapted to this study effectively homogenizes samples and distributes them in a medium that facilitates relatively low LOD.…”

“…WDXRF was selected over other analytical methods for its dual potential as a very well-established analytical method that can also be directly applied to calibration of our pXRF studies (Conrey et al, 2014). We therefore initiated this project with a well-established bulk technique in order to determine if the geochemical characteristics of earthen architecture are varied enough to differentiate different cultural materials.…”