Picogram Determination of Methylmercury in Seawater by Gold Amalgamation and Atomic Absorption Spectrophotometry

Abstract

Abstract An analytical procedure for the determination of total mercury (T-Hg) and methylmercury (CH3Hg) in seawater was described. CH3Hg was extracted with benzene and concentrated by a succession of three partitions between benzene and a cysteine solution. From the last cysteine extract, CH3Hg was transfered into a dithizone chloroform solution. CH3Hg-dithizonate was determined by atomic absorption spectrophotometry (AAS). T-Hg was also determined by AAS after wet combustion of the sample with sulfuric acid and potassium permanganate. The limit of detection was 0.005 ng for CH3Hg, when 3.6 liter of seawater was treated, and the coefficients of variation for CH3Hg 10 ng was about 1%. Seawater from the coast of the Kinki-area, the middle part of the mainland of Japan, seemed to have a T-Hg content of about 10ngl−1 of which nearly 1% was suspected to be the content of CH3Hg.