Methylmercury determination in biological samples by derivatization, solid-phase microextraction and gas chromatography with microwave-induced plasma atomic emission spectrometry

A method for the extraction and gas chromatographic determination of methylmercury in biological matrices is presented. By combining the advantages of two extraction techniques—microwave-assisted extraction (MAE) and solid-phase microextraction (SPME)—the separation of methylmercury from biological samples is possible. Specifically, the procedure involves microwave extraction with 3 M hydrochloric acid, followed by aqueous-phase derivatization with sodium tetraphenylborate and headspace SPME with a silica fibre coated with polydimethylsiloxane (PDMS). For optimization of the derivatization–SPME procedure, a central composite experimental design with α=1.682 and two central points was used to model gas-chromatographic peak areas as functions of pH, extraction temperature and sorption time. A desirability function was then used for the simultaneous optimization for methylmercury and Hg(II). The optimal derivatization−SPME conditions identified were close to pH 5, temperature 100 °C, and sorption time 15 min. The identification and quantification of the extracted methylmercury is carried out by gas chromatography with microwave-induced plasma atomic emission spectrometry detection. The validity of the new procedure is shown by the results of analyses of certified reference materials.