ANALYSIS OF ORGANOMERCURY COMPOUNDS IN SEDIMENTS BY CAPILLARY GC WITHATOMIC FLUORESCENCE DETECTION

Analysis of methyl- and ethylmercury (NIM and EM) halides in biologica l and environmental samples is generally performed by gas chromatograp hy with electron capture detection. Tedious sample work-up protocols a nd poor chromatographic response (using packed columns) have, however, shown the need for the development of new methods in this field. This paper reports a sensitive method, free from these deficiencies, for t he determination of methyl- and ethylmercury. The organomercury compou nds (MM and EM) are first released from the sample matrix, by the comb ined action of acidic potassium bromide and cupric ions, and then extr acted into dichloromethane. The initial extracts are subjected to thio sulfate clean-up and the organomercury species are isolated as their c hloride derivatives by addition of cupric chloride, and subsequent ext raction into a small volume of organic solvent. Capillary GC coupled w ith atomic fluorescence detection provided excellent separation effici encies for methyl- and ethylmercury and proved to be a very selective and sensitive technique. The absolute detection limit for both MM and EM was found to be 0.2 pg.