Determination of methylmercury in biological samples by semiautomated headspace analysis

Abstract

Gas-liquid distribution coefficients of methylmercury halides dissolved in water or benzene have been assessed by using a headspace injection system coupled to a gas chromatograph-microwave-induced plasma system. Vapor concentrations decreased in the following order: CH<sub>3</sub>HgI > CH<sub>3</sub>HgBr > CH<sub>3</sub>HgCl. To transform all methylmercury iodide, iodoacetic acid (IAc) is used as the liberating agent. Methylmercury iodide degradation is prevented by the addition of sodium thiosulfate (0.05 M). The results obtained with internal standard addition are not influenced by other volatile compounds including other mercury compounds. The method has been applied to a series of biological samples. The detection limit of methylmercury in biological samples is 1.5 ng/mL of homogenate.Contrary to direct on-column injection, no column performance degradation was observed when using a headspace sampler after more than 50 analyses.