Direct online HPLC-CV-AFS method for traces of methylmercury without derivatisation: a matrix-independent method for urine, sediment and biological tissue samples

Mercury (Hg) is a global pollutant which occurs in different species, with methylmercury (MeHg) being the critical compound due to its neurotoxicity and bioaccumulation through the food chain. Methods for trace speciation of MeHg are therefore needed for a vast range of sample matrices, such as biological tissues, fluids, soils or sediments. We have previously developed an ultra-trace speciation method for methylmercury in water, based on a preconcentration HPLC cold vapour atomic fluorescence spectrometry (HPLC-CV-AFS) method. The focus of this work is mercury speciation in a variety of sample matrices to assess the versatility of the method. Certified reference materials were used where possible, and samples were spiked where reference materials were not available, e.g. human urine. Solid samples were submitted for commonly used digestion or extraction processes to obtain a liquid sample for injection into the analytical system. For MeHg in sediment samples, an extraction procedure was adapted to accommodate MeHg separation from high amounts of Hg(2+) to avoid an overload of the column. The recovery for MeHg determination was found to be in the range of 88-104% in fish reference materials (DOLT-2, DOLT-4, DORM-3), lobster (TORT-2), seaweed (IAEA-140/TM), sediments (ERM(®)-CC580) and spiked urine and has been proven to be robust, reliable, virtually matrix-independent and relatively cost-effective. Applications in the ultra-trace concentration range are possible using the preconcentration up to 200 mL, while for higher MeHg-containing samples, lower volumes can be applied. A comparison was carried out between species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID-GC-ICP-MS) as the gold standard and HPLC-CV-AFS for biological tissues (liver, kidney and muscle of pilot whales), showing a slope of 1.008 and R (2) = 0.97, which indicates that the HPLC-CV-AFS method achieves well-correlated results for MeHg in biological tissues

Mercury alkylation in freshwater sediments from Scottish canals

Funding This research was partly funded by award of a Strategic Educational Pathways Scholarship (Malta) to RC. Acknowledgement The authors wish to thank Scottish Canals (formerly British Waterways) for providing background information on the canal systems studied and granting permission to sample, and Dr Ana Teresa Reis (University of Aveiro) for conducting the Fe and S analysis in the Union Canal Sediments.Peer reviewedPostprin

Mercury alkylation in freshwater sediments from Scottish canals

Mercury concentrations were investigated in freshwater sediment from two canals in Scotland, UK. High concentrations found in the Union Canal (353-1200 mg kg(-1)) likely originate from historical munitions manufacture, with lower levels in the Forth & Clyde Canal (0.591-9.14 mg kg(-1)). Concentrations of methylmercury (MeHg) were low - from 6.02 to 18.6 mu g kg(-1) (0.001-0.023% of total Hg) in the Union Canal and from 3.44 to 14.1 mu g kg(-1) (0.11-0.58% of total Hg) in the Forth & Clyde Canal - and there was a significant inverse relationship between total Hg concentration and %MeHg. Total Hg concentration was significantly negatively correlated with pH and positively correlated with Fe content (in the Union Canal only) but not with organic matter, S content or the proportion of clay present. The MeHg concentration was not correlated with any of the above sediment parameters. Ethylmercury was detected in the most highly contaminated sediments from the Union Canal. (C) 2017 Elsevier Ltd. All rights reserved