Comparison of nickel speciation in workplace aerosol samples using sequential extraction analysis and X-ray absorption near-edge structure spectroscopy

There is a pressing need to further develop speciation knowledge of Ni workplace aerosols as the Zatka sequential extraction method used until now to speciate workplace Ni exposures has limitations. Here we compare the Zatka and XANES methods and evaluate XANES spectroscopy as a more appropriate and accurate technique for identifying nickel species in workplace aerosols. XANES spectroscopy is capable of identifying unique Ni species in the unaltered samples. Our findings indicate some significant departures in speciation assignment between the Zatka and XANES methods. In particular, the Zatka method can overestimate the soluble Ni fraction and it may underestimate the sulphidic and metallic fractions in some samples. Of particular importance, XANES is able to identify component sulphidic species. This information can lead to more accurate exposure matrices and more refined epidemiological analysis of respiratory cancer causation in sulphidic Ni processing.