Laboratory Evaluation of a Field-Portable Sealed Source X-Ray Fluorescence Spectrometer for Determination of Metals in Air Filter Samples

Abstract

Recent advances in field-portable X-ray fluorescence (FP XRF) spectrometer technology have made it a potentially valuable screening tool for the industrial hygienist to estimate worker exposures to airborne metals. Although recent studies have shown that FP XRF technology may be better suited for qualitative or semiquantitative analysis of airborne lead in the workplace, these studies have not extensively addressed its ability to measure other elements. This study involved a laboratory-based evaluation of a representative model FP XRF spectrometer to measure elements commonly encountered in workplace settings that may be collected on air sample filter media, including chromium, copper, iron, manganese, nickel, lead, and zinc. The evaluation included assessments of (1) response intensity with respect to location on the probe window, (2) limits of detection for five different filter media, (3) limits of detection as a function of analysis time, and (4) bias, precision, and accuracy estimates. Teflon, polyvinyl chloride, polypropylene, and mixed cellulose ester filter media all had similarly low limits of detection for the set of elements examined. Limits of detection, bias, and precision generally improved with increasing analysis time. Bias, precision, and accuracy estimates generally improved with increasing element concentration. Accuracy estimates met the National Institute for Occupational Safety and Health criterion for nearly all the element and concentration combinations. Based on these results, FP XRF spectrometry shows potential to be useful in the assessment of worker inhalation exposures to other metals in addition to lead.

Keywords:

• accuracy
• bias
• metalworking
• precision
• welding

ACKNOWLEDGMENTS

The authors wish to thank Kevin Ashley, David Bartley, Martin Harper, Eugene Kennedy, Stanley Shulman, and Sid Soderholm of NIOSH for their technical and editorial input.

The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

Notes

^A All standards had certified accurate and uniform deposits within ±5%.

^B Three thin film standards in comparatively lower concentration ranges were used forchromium, manganese, and nickel, in keeping with the airborne concentrations anticipated at welding and metalworking operations.

^A Elemental standards for As, Mo, and Co were not available at the time of this study.

^B Values in this row are based on 10-hr sample duration.

^C Values indicated for zinc oxide (ZnO).