Determination of mercury in selected polluted sediments using HPLC-ICP-MS in Westbank area, Western Cape, South Africa

Abstract

High selectivity, excellent linearity and reproducibility were achieved using HPLC-ICP-MS method for mercury in sediments. The HPLC-ICP-MS method reported previously for mercury in biota analysis was adapted in terms of operational consumables and optimized for the efficient mercury determination in riverbed sediments; a first for South Africa. Results obtained for real environmental samples, were verified by Direct Mercury Analysis (DMA) by an accredited laboratory. The determination of inorganic and organic mercury compounds in sediments was based on the complexation of mercury compounds with cysteine. The separation was achieved on a reversed-phase C18 column (15 cm×4.6mm id) using aqueous 0.1% w/v L-cysteine•HCl+0.1% w/v L-cysteine mobile phase at a flow rate of 0.8 mL min-1 at ambient temperature. The method was found to be suitable for the routine analysis of Hg compounds in sediments as well as aqueous media and was developed to determine the influence of humic substances on the bioavailability of mercury species. The results were comparable and consistent with those determined with a Direct Mercury Analyzer. The detection limit for methylmercury, ethylmercury and inorganic mercury were lower than 10 ng L-1 and recoveries for spiked samples was >90 % . The accuracy of the method was assessed by the analysis of certified reference material (European Reference Material ERMCC580 and Tort-2) and found to be in good agreement. Mercury concentration was determined in sediments collected from the Eerste Kuils River, Westbank area, Kuilsriver, Western Cape, South Africa. Mercury concentration was determined to vary from 2-14 ng g-1 (w.wt).