Determination of methylmercury in fish and seafood using gas chromatography with atomic emission detection
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ABSTRACT:
Mercury is an environmental contaminant that appears in different chemical forms. Or-ganic forms of mercury, such as methylmercury, can occur in marine organisms like fish and shellfish and are far more toxic than the inorganic form. It is therefore vital to have refined analytical methods for the different mercuric species in order to evaluate the potential risk for seafood consumers.
The most problematic step in the determination of mercury species in marine organism is the sample preparation. The best performing methodology consisted of digesting the sample in methanolic potassium hydroxide solution followed by mercury speciation with aqueous phase ethylation. Prior to injection into the GC system, the derivatized mer-cury compounds have to be extracted into an organic solvent, which simultaneously facilitates a clean-up, as the fish matrix predominantly remains in the aqueous phase. This is especially true for the saponified fat. Extraction with n-hexane before injection into the GC-AED-System gave best results.
The main advantage of this procedure is that both Hg2+ and methylmercury as well as the methylmercury proportion can be determined simultaneously. Finally, this proce-dure generally showed recoveries above 90%.
The procedure was found to be selective and sensitive with a limit of detection of 6 µg/kg for methylmercury. The average recovery for the full procedure was 91 ± 19%. A preliminary survey of seafoods confirmed the previous observation that the proportion of methylmercury in the total mercury can vary widely, up to a complete occurrence as methylmercury (see table).
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STATISTICS
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