Issue 11, 2001

Abstract

An isotope dilution (ID) based GC-ICP-MS method, able to simultaneously determine incipient concentrations of methylmercury as well as the degree of methylation of inorganic mercury and de-methylation of methylmercury in brackish water sediments, was developed. Methyl- and inorganic mercury were extracted from the sediments using a solution containing KBr–H2SO4–CuSO4. CH3200Hg+ was added as a species-specific internal standard and 199Hg2+ to monitor artefact formation of methylmercury during sample work-up. Extracted mercury species were treated with NaBEt4 to form ethyl derivatives that were trapped on Tenax. The typical precision of the method was in the range of 2–3% RSD for methylmercury concentrations of 2–5 ng g−1 sediment (dry weight). The detection limit of the method based on 3 times the standard deviation of repeated sediment analysis was 0.3 ng g−1 sediment as the metal. When using bromide for extraction, degradation of methylmercury into elemental mercury and the probable formation of methylmercury bromide during sample pretreatment and/or analysis were observed. For investigations of mercury methylation and de-methylation during sample incubation, 201Hg2+ and CH3198Hg+ were added to sediment layers at 20% of the ambient concentrations of the two species. Mercury methylation and de-methylation activities differed by a factor of four between depths and were highest in the top 3 cm of the sediment. In this region 9.5% of the added 201Hg2+ tracer was methylated and 79% of the CH3198Hg+ tracer was de-methylated. Detection limits for methylation of 201Hg2+ and de-methylation of CH3198Hg+ were 0.1 ng g−1 and 0.2 ng g−1, respectively. Methylmercury concentrations changed about 5 times over the depth profile, which implies that samples have to be taken over a well-defined depth when assessing representative data.

Article information

Article type
Paper
Submitted
30 Jul 2001
Accepted
11 Sep 2001
First published
22 Oct 2001

J. Anal. At. Spectrom., 2001,16, 1296-1301

Applications of enriched stable isotope tracers in combination with isotope dilution GC-ICP-MS to study mercury species transformation in sea sediments during in situ ethylation and determination

L. Lambertsson, E. Lundberg, M. Nilsson and W. Frech, J. Anal. At. Spectrom., 2001, 16, 1296 DOI: 10.1039/B106878B

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