Direct chromium speciation using X-ray spectrometry and chemometrics

摘要

Chromium is a chemical element that occurs in two principal distinct forms: trivalent (Cr(III)) and hexavalent (Cr(VI)). As chromium toxicity depends on its oxidation state, the concentrations of both the species should necessarily be determined, and not only that of total chromium. Using X-ray spectrometry allied to chemometrics, this work presents a new method for chromium speciation,with no prior separation and/or preconcentration of Cr(III) and Cr(VI) species. Spectra of several solutions containing different concentrations of Cr(III) and Cr(VI) were obtained. The data were treated through principal component analysis and partial least squares regression. The results obtained show that direct speciation using a conventional X-ray spectrometer is possible, with calculated limits of detection and quantification for Cr(III) and Cr(VI) being lower than 17 and 50 μg g-1, respectively.