Rapid determination of methylmercury in biological materials by GC-MIP-AES or GC-ICP-MS following simultaneous ultrasonic-assisted in situ ethylation and solvent extraction

A simple and rapid sample pre-treatment procedure was developed for the determination of methylmercury in biological materials. The procedure is based on acid leaching (5 min) of sample materials followed by simultaneous in situ derivatisation and extraction (40 min) in the presence of sodium tetraethylborate and nonane, buffered at pH 7.0, in an ultrasonic field. The nonane phase with an overall average recovery of methylmercury higher than 90% was analysed by gas chromatography (GC) coupled to microwave induced plasma atomic emission spectrometry (MIP-AES) or inductively coupled plasma mass spectrometry (ICP-MS). Detection limits (as Hg), based on three times the standard deviation of a standard solution, were 4.4 ng g−1 for GC-MIP-AES and 2.6 ng g−1 for GC-ICP-MS. No artefact formation of methylmercury during sample pre-treatment was observed following the addition of a 201Hg2+ isotope standard. The method was validated by the analysis of three biological certified reference materials and applied to the determination of methylmercury in a fish sample.