OPTIMIZATION OF SUPERCRITICAL-FLUID EXTRACTION GAS-CHROMATOGRAPHY OF METHYLMERCURY IN MARINE SAMPLES

Two-level factor designs were used to optimize the supercritical fluid extraction (SFE) of methylmercury (Me-Hg) in marine samples, which we re subsequently analysed by gas chromatography-electron capture detect ion (GC-ECD). Several variables potentially affect to extraction effic iency and kinetics. The factors studied were: CO2 flow-rate and densit y, extraction cell temperature, static extraction time, nozzle and tra p temperature, amount of hydrochloric acid and contact time between th e acid and the sample before to extraction. The extraction kinetics wa s studied in all experiments by splitting extracts at 2, 7, 17 and 37 min. The results suggest that only the extraction cell temperature is statistically significant. The optimized SFE procedure to extract Me-H g was validated by means of three available reference materials having certified methylmercury content.