25 Accuracy and interferences associated with direct-on-filter quartz analysis of samples obtained from a brickworks, copper mine and gold mine

Abstract Background Numerous publications have demonstrated that potable Fourier Transform Infrared (FTIR) spectrometers can be used to perform direct-on-filter quartz analysis to obtain results quicker following respirable crystalline silica (RCS) exposure monitoring. This study analysed respirable crystalline silica (RCS) exposure samples from three commodities to test their influence on the quartz results obtained from a potable FTIR spectrometer. Methods Forty-four RCS exposure samples collected form a brickworks crushing area (n = 12), copper mine crushing area (n = 12) and gold mine tailings dam (n = 20) were analysed direct-on-filter using a PerkinElmer Spectrum 2 portable FTIR spectrometer and the NIOSH Field Analysis of Silica Tool (FAST). This was followed by X-ray diffraction (XRD) analysis using NIOSH 7500. Additionally, bulk samples from the copper mine and gold mine tailings dam were analysed using XRD (PANalytical X’Pert Pro) to identify minerals that could interfere with the quartz analysis. The accuracy of the FTIR analysis was assessed using Bland-Altman plots. Results The mean bias between the methods was the higher for the copper mine crusher dust (0.026 mg) compared to the brickworks (−0.007 mg) and the gold mine tailings dam dust (0.002 mg). Bulk samples contained minerals that are known to interfere with quartz analyses. The copper mine crusher sand contained 43% quartz, 17% muscovite and 6% talc, and the gold tailing dam sand contained 85% quartz and 4% pyrophyllite. Conclusions Portable FTIR spectrometers can be very useful to obtain timely results post-shift. However, users should be mindful of minerals in the sample that can interfere with quartz analysis.