Serum/plasma methylmercury determination by isotope dilution gas chromatography : inductively coupled plasma mass spectrometry

Abstract A method for the determination of methylmercury in plasma and serum samples was developed. The method uses isotope dilution with 198 Hg-labeled methylmercury, extraction into dichloromethane, back-extraction into water, aqueous-phase ethylation, purge and trap collection, thermal desorption, separation by gas chromatography, and mercury isotope specific detection by inductively coupled plasma mass spectrometry. By spiking 2 mL sample with 1.2 ng tracer, measurements in a concentration interval of (0.007–2.9) μg L −1 could be performed with uncertainty amplification factors −1 was estimated at 10 times the standard deviation of concentrations measured in preparation blanks. Within- and between-run relative standard deviations were −1 , 0.35 μg L −1 and 2.8 μg L −1 , with recoveries in the range 82–110%. Application of the method to 50 plasma/serum samples yielded a median (mean; range) concentration of methylmercury of 0.081 (0.091; −1 . This is the first time methylmercury has been directly measured in this kind of specimen, and is therefore the first estimate of a reference range.