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

Shirley Le Roux,Andrew Crouch,Priscilla Baker

doi:10.17159/0379-4350/2016/v69a15

Shirley Le Roux, Andrew Crouch + Show 1 more

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https://doi.org/10.17159/0379-4350/2016/v69a15

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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).

Highlights

Anthropogenic sources as well as natural contributions have increased Hg levels in the environment
Several detectors have been developed that can substantially lower the sensitivity of this analytical technique, including inductively coupled plasma (ICP), inductively coupled plasma mass spectroscopy (ICP-MS), and electrochemical detection
Sample Preparation and HPLC-ICP-MS Analysis A 0.5–1.5 g sediment sample was weighed into a 50 mL polypropylene centrifuge tube to which 2 mL of CuSO4 (1M), 10 mL of HNO3 (3M) and 10 mL of CH2Cl2 was added

Summary

Introduction

Anthropogenic sources as well as natural contributions (e.g. volcanic activity and evaporation from the oceans) have increased Hg levels in the environment. Several detectors have been developed that can substantially lower the sensitivity of this analytical technique, including inductively coupled plasma (ICP), inductively coupled plasma mass spectroscopy (ICP-MS), and electrochemical detection These methods have shown high selectivity, excellent linearity and reproducibility in analysis for MeHg and other forms of Hg.[31] A disadvantage of using ICP as a detector for HPLC is that the mobile phase should be carefully chosen as solvents such as methanol and acetonitrile are not compatible with the argon plasma.[2] Mobile phases which contain high concentrations of salts and buffers can clog the cones of the nebulizer which can produce changes in sensitivity.[32]. The Eerste River site (33°05’S, 18°46’E) is approximately 36 km southeast of Cape Town

Experimental

Results and Discussion

Conclusion