An indirect Raman spectroscopy method for the quantitative measurement of respirable crystalline silica collected on filters inside respiratory equipment

Abstract

A new Raman method for respirable crystalline silica that is capable of measuring concentrations below the limits of detection of current analytical methodology and worker exposures when wearing respirators.

Application of a Fourier Transform Infrared (FTIR) Principal Component Regression (PCR) Chemometric Method for the Quantification of Respirable Crystalline Silica (Quartz), Kaolinite, and Coal in Coal Mine Dusts from Australia, UK, and South Africa

“…X-ray diffraction (XRD) and FTIR are two analytical techniques that are commonly employed for the measurement of aerosol sampling filters containing RCS (Pickard et al, 1985;HSE, 2014). Raman spectroscopy is also available (Zheng et al, 2018;Stacey et al, 2020) but is a relatively new technique for this type of analysis,…”

Raman spectroscopy and X‐ray diffraction responses when measuring health‐related micrometre and nanometre particle size fractions of crystalline quartz and the measurement of quartz in dust samples from the cutting and polishing of natural and artificial stones

“…Moving to a lower magnification objective to increase the collection of laterally scattered photons will not improve the intensity of the Raman scatter, because the lower magnification with low numerical aperture has a smaller angle of light collection. [45] Fine grains studied in this work are smaller than those previously investigated and will scatter photons in a relatively localised area close to the particles' surface, which will be efficiently collected by the detector when using the current optics applied by the method proposed by Stacey et al [24] ; that is, the proportion of laterally dispersed photons is small for particles in this study. These conditions may account for the plateau for Raman band intensity observed in this research, for fractions of quartz particles with median diameters between 1 and 7 μm.…”

“…The number of photons counted could increase with particle size when the detector area was much larger than the illumination area (×4.2) but could also decrease when the two areas were more similar (×1.6) because the laterally scattered photons on larger particles were not detected as efficiently. Previous method development work showed a decrease in measurement sensitivity when using the quartz reference material with the largest particle size (Quin B), [24] suggesting that the instrument arrangement proposed for the measurement method was not efficiently collecting the laterally scattered photons for the very largest particles in this instance. In this research, reported herein, the minimum area of the focused spot was 4.5 μm 2 , which is slightly less the than median diameter of the particles of Quin B (7 μm).…”

“…The preparation of calibration samples to aid a uniform deposit is described in previous articles. [21,24] The mass of sample loaded onto the silver filters was kept below 1000 μg to avoid correcting for sample absorption when using XRD. [36] The calibration response trend line was extended up to 1800 μg to examine the effect of the depth of sample on Raman band intensity.…”

“…[20][21][22][23] The aim of this work is to assess if particle size is a factor that affects the Raman band intensity when using the specific analytical conditions proposed for a new method to measure aerosols of RCS collected onto filters. [24] Another aim of this study is to compare results obtained using Raman spectroscopy, as a new method to measure RCS, with those obtained from the established technique of XRD for both laboratory generated samples and emissions collected during typical stone working activities.…”