A Method for the Determination of Methylmercury in Environmental Samples, Particularly Sediment

Abstract

A successful method was developed for the determination of trace amounts of methylmercury in environmental samples, particularly in sediments by gas-liquid chromatography (GLC). A sample of known weight was treated with ethanolic potassium hydroxide solution and extracted with dithizone-benzene solution after slightly acidification with hydrochloric acid. The methylmercury dithizonate in benzene layer was partitioned into a small portion of sodium sulfide in aqueous ethanol as bismethylmercury sulfide. The excess of sulfide ions was removed by bubbling air through the solution slightly acidified with hydrochloric acid, and then methylmercury in the solution was re-extracted into dithizone-benzene solution as methylmercuric dithizonate. Methylmercury thus obtained was measured by ECD-GLC with a column of 5% diethylene glycol succinate and 5% sodium chloride on chromosorb W. The recovery of methylmercury added to river sediments was 95.7% on the average and the detection limit was 0.5 ppb as mercury on a wet weight basis in the present method. This method was also applicable to the analyses of methylmercury in other environmental samples such as natural water, fish, etc.