Analysis of methylmercury and total mercury in seafood using flow injection cold vapour atomic absorption spectrometry

Methylmercury and total mercury in sea food were analysed by flow injection cold vapour atomic absorption spectrometry using sodium tetrahydroborate as a reductant. Methylmercury in aquatic species was leached with HBr 47% as neutral MeHgBr complex and quantitatively extracted into toluene. MeHgBr in toluene was back extracted with L-cysteine into aqueous phase in form of negatively charged MeHg-L-cysteine complex. All organic compounds in the aqueous phase were decomposed with KMnO4/H2SO4 to convert methyl mercury to Hg2+ for direct cold vapour reaction. The seafood sample was digested with aquaregia for total mercury analysis. The limits of detection/quantitation for methylmercury and total mercury were là 0.69/1.3 ng/g and 0.70/2.2 ng/g (as Hg), respectively. The recovery of the analytical methods for MeHg and total Hg were 96.5–105% and 93–101% within the concentration ranges of 2–700 ng/g Hg. The concentrations of MeHg and total Hg in some common seafood such as fish, shrimp and squid were in ranges of 1.2–483.5 ng/g and 4.0 ÷ 663.4 ng/g.