Determination of methylmercury after supercritical fluid extraction

A method, using supercritical fluid extraction, for determining methylmercury in seafood has been developed to eliminate use of toxic organic solvents. Seafood samples were treated with 1N NaOH and then acidified with HCl to release CH3HgCl. After mixing the sample with cellulose powder (40 mesh) containing stearic acid modifier at 5 mg/g, the extraction was performed with supercritical CO2 under the following conditions: pressure, 200 atm; temperature, 50 degrees C; time, 20 min; and trap, 0.01N Na2S2O3 in a conical tube immersed in a flask of warm water to prevent freezing. The extract was then analyzed by a suitable method, such as cold-vapor atomic absorption spectrophotometry. The accuracy of the procedure was verified by analyzing biological standard reference materials. Several commercial seafood samples and spikes have been analyzed.