Chromium speciation by hyphenation of high-performance liquid chromatography to inductively coupled plasma-mass spectrometry—study of the influence of interfering ions

Abstract

This study presents the development of a speciation method for chromium redox species by HPLC-ICP-MS. Chromatographic separation is performed with CG5A-CS5A columns set (Dionex) containing both anionic and cationic groups to retain Cr(VI) and Cr(III), respectively, associated with a nitric acid elution. After optimisation, detection limits lower than 0.5 µg L⁻¹ were obtained for both Cr species. This method is free from interferences possibly linked to chloride and organic or inorganic carbon on the two most abundant chromium isotopes (⁵²Cr⁺ and ⁵³Cr⁺). A modification of the chemistry of Cr(III) was, however, observed in the presence of hydrogencarbonate ions. In this medium, for trivalent chromium, three peaks instead of one are present on the chromatograms. This modification was attributed to the hydrolysis of Cr(III) that occurs at these pH values. The accuracy of the analytical procedure was verified by analysing a certified reference material (BCR-CRM 544) and spiked natural waters. The concentrations found for Cr(VI) were in good agreement with the certified and spiked values. Because of the high reactivity of Cr(III) in alkaline medium, recoveries were not completely quantitative.