Evaluation of portable XRF instrumentation for assessing potential environmental exposure to toxic elements

摘要

Portable instruments based on X-Ray Fluorescence Spectrometry (XRF) have the potential to assist in field-based studies, provided that the data produced are reliable. In this study, we evaluate the performance of two different types of XRF instrument (XOS prototype and Thermo Niton XL3t). These two XRF analysers were evaluated in a laboratory setting, and data were reported for 17 elements (As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sn, Sr, Ti, V, and Zn). Samples analysed (n=38) included ethnic herbal medicine products (HMPs), ethnic spices (ES), and cosmetic products (CPs). Comparison analyses were carried out using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). In general, results reported for Cd, Cu, and Pb by the XOS prototype analyser, using the non-metal mode, were negatively biased (5-95%) as compared to ICP-OES. In contrast, results reported for Pb, As, Cd, Cu and Zn by the Niton, using the soil mode, were positively biased, in some instances (Cd) by up to four orders of magnitude. While the sensitivity of both instruments was insufficient for reliably quantifying' toxic elements below 15mg/kg, XRF was still capable of positively detecting' many elements at the low single-digit mg/kg levels. For semi-quantification estimates of contaminants at higher levels, and with limited sample preparation, both XRF instruments were deemed fit for the purpose. This study demonstrates that modern XRF instrumentation is valuable for characterising the elemental content of food, cosmetic, and medicinal products. The technology is particularly useful for rapidly screening large numbers of products (100's per day) in the field, and quickly identifying those that may contain potentially hazardous levels of toxic elements. Toxic elements can be confirmed by examining the raw spectrum, and the limitations of factory-based calibration are generally manageable for field-based studies.