FIELD PORTABLE XRF: HOW TO GET GOOD AND TRACEABLE DATA

The Canadian Mining and Industry Research Organization (CAMIRO) under the scientific guidance of Gwendy Hall performed a comprehensive two part study on the recommended use and operating procedures for industrial “commercial” pXRF. Based parts one of the study it is clear that neither vendor’s unit produce publication ready data(1). To enable pXRF units to be included as tools in research papers it is imperative to enable the user to calibrate them if desired. This enables user to use the same methodology as on their laboratory units. Many early pXRF geo papers used data without vetting the accuracy or the applicability of the method to the studied materials. For recent submissions it was therefore required to provide details in the calibration and validation of the analyser to prove that it was correctly set up for the desired application. The talk will illustrate how a “factory” generic mining calibration needs to differ from a research based geochemical calibration from a design and performance point of view. The generic mining calibration of a BRUKER S1 TURBO SDD unit is compared with the user calibration for Basalts on a TRACER IV SD done by the University of Washington’s Rick Conroy(2).

We will learn that the more unspecific a calibration is, the less accurate and more variable results can be expected. For geo samples we deal in addition to matrix effects with additional mineralogical and grain size effects. These latter effects cannot be corrected for mathematically thus limiting our ability to create a universal geo calibration.

1. Hall G, Buchar A, Bonham-Carter G (2011) Quality Control Assessment of portable XRF Analysers: Development of Standard Operating Procedures, Performance on Variable Media and Recommended Uses. Canadian Mining and Industry Research Organization (CAMIRO) Exploration Division, Project 10E01 Phase I, 171 pp
2. R. Conroy et al. In submission PXRF Calibration for Archaeological Samples Using Influence Coefficients, special PXRF volume of the journal Geochemistry: Exploration, Environment, Analysis (GEEA, run by Geol Soc of London and Assoc of Applied Geochemists)