Methylmercury Determination in Fish by Direct Mercury Analyzer

Background: There are two methods for quantifying methylmercury (MeHg) in fish using GC electron capture detection (ECD): AOAC INTERNATIONAL Official Method 988.11 and the Korean Food Code (KFC) method. Both of these methods consume a large amount of chemicals and require long pretreatment times because of several complicated MeHg extraction steps. Objective: In this study, a new method for the simple and rapid determination of MeHg in fish has been developed. The method is based on the investigation of oxygen combustion-gold amalgamation using a direct mercury analyzer (DMA) after the complete removal of MeHg by organic extraction and back-extraction to an aqueous medium. Methods: The DMA is suitable for the analysis of both solid and liquid materials and has a good detection limit. The developed method was validated by comparing the MeHg recoveries (%) of both certified reference materials and the market-purchased fish samples with the MeHg concentration obtained using the KFC method. Results: The following parameters pertaining to the developed method were established: detection limit, 1.02 mu g/kg; LOQ, 3.09 mu g/kg; linearity (r), 0.9998; range, 0.1-300 mu g/kg; and recovery, 95-97%. Conclusions: Our method is a promising alternative by virtue of its much simpler and faster sample pretreatment procedure, with a MeHg recovery as high as that of the KFC method. Highlights: The developed method enables the simultaneous analysis of total Hg and MeHg with only DMA equipment.