For solvent extraction a solution containing 0.03–0.1 M CuSO4 (Merck) and 0.4–0.5 M KBr (Merck) in 5% H2SO4 was prepared. No significant difference in the MeHg extraction efficiency was observed if the Cu2+ concentration in extraction solution was raised from 0.03 to 0.1 M and Br concentration from 0.4 to 0.5 M.