Abstract: In this work we have developed a cost-effectivemethod for the analysis of methyl mercury (MeHg) inseawater fish muscle. The novelty of this method lies in theuse of microwave- assistedextraction with acidic solution (HCl), addition of toluene, and subsequent extraction with cysteine acetate solution where only MeHg is present because of its affinity for cysteine groups. MeHg in cysteine phase and total mercury in the homogenate muscle tissue were determined using a direct Hg analyzer (DMA-80). Validation, precision, and accuracy of the methodwere evaluated and monitored with a tuna fish certified reference material (CRM 463) containing MeHg. Keywords Methyl mercury Microwave extraction Mercury Direct mercury analyzer 萊伯泰科Blue Star紫外可見分光光度計