CV-AFS Determination of Methyl Mercury in Sediment and Soil Samples with Ultrasonic Extraction

Methyl mercury in the sample was extracted ultrasonically with 6 mol·L-1 HCl for 2 h.After centrifugation,the supernatant extract was extracted with dichloromethane.The organic phase was taken and de-ionized water was added.Dichloromethane was expelled by evaporation with N2-blowing at 60 ℃ and methyl mercury was retained in the water phase.The water solution was acidified with 9 mol·L-1 H2SO4 and treated with mixed solution of KBrO3 and KBr to transform the methyl mercury into inorganic mercury ion,which was determined by CV-AFS.Detection limit (3S/N) of the method found was 0.1 pg·g-1.The proposed method was used in determination of methyl mercury in samples of soil and sediment,giving values of RSD′s (n=6) less than 5%.Average recovery found by standard addition method attained to a value of 93.6%.