Development of a dispersive liquid-liquid microextraction method for the spectrophotometric determination of mercury in food samples

Dispersive liquid-liquid microextraction (DLLME) technique combined with ultraviolet-visible spectrophotometry for the preconcentration and determination of mercury in food samples was developed. Dithizone, chloroform and ethanol were used as chelating agent, extraction solvent and disperser solvent, respectively. Some important DLLME parameters such as the volume of extraction and disperser solvent, pH, concentration of chelating agent and extraction time were investigated in detail. Under the optimized conditions, the calibration graph was linear from 10 to 200ng·mL-1 with a correlation coefficient of 0.9966. The limit of detection was 3ng·mL-1 and the relative standard deviation (n=7, for 100ng·mL-1 of mercury) was 4.3%. The method was successfully applied into the determination of trace amounts of mercury in fish and tea leaves.