Abstract
In this article we follow up on our recent investigations of the use of the 1870 cm-1 band of silica in diffuse reflectance spectroscopy (DRS) for the quantification of silica in respirable dusts. The 1870 cm-1 band, though weak in Fourier transform infrared (FTIR) spectroscopy, has sufficient sensitivity for quantitative analysis in DRS and suffers insignificant interference from the absorption bands of other minerals usually found in mine dusts. In this work we have extended these studies to silica standards deposited on VM-1 filters and mine dust samples deposited on DM-450 filters. The mass of the deposited silica on the filters varied between 35 μg to 325 μg. The intensity of the 1870 cm-1 band varied linearly with mass with the slope 0.0083 μg for the samples deposited on the VM-1 filters, satisfying the Kubelka-Munk theory for dilute samples. This linearity and sensitivity suggest the usefulness of DRS for silica quantification for dust deposited on filters without any additional sample preparation. Because the surface of the silica particle is responsible for its pathogenicity, a surface analytical technique such as DRS should be more relevant for the quantification of the biologically active silica in mine dusts. Dusts deposited uniformly on filters also eliminate the problems associated with the reproducibility of the powder sample-loading in DRS. The quantitative analysis performed on a series of mine dust samples by DRS demonstrates its applicability and usefulness as a technique for silica analysis. These considerations suggest DRS to be a very promising technique for on-filter determination of silica in mine dusts samples.
