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A method has been proposed for the differential determination of inorganic and organic mercury in environmental and biological materials, based on their successive extraction followed by a cold vapor atomic absorption spectrometric (CVAAS) determination.Mercury was first extracted by shaking a sample with 1 M hydrochloric acid containing 3% sodium chloride in the presence of copper(I) chloride. In order to separate organic mercury from inorganic mercury, the extract was shaken with chloroform to extract only organic mercury. The chloroform phase was transferred into a 50 ml volumetric flask and 0.4 ml of 0.2% dithizone-chloroform solution was added. The contents of the flask was evaporated to dryness, followed by addition of 2 ml of 1:1 nitric acid-perchloric acid solution and 5 ml of concentrated sulfuric acid and heating at ca. 230°C for 30 min. The hydrochloric acid phase containing inorganic mercury was transferred into a 50 ml volumetric flask, followed by addition of 1 ml of 60% perchloric acid and 5 ml of concentrated sulfuric acid and heating at ca. 230° C for 30 min. After cooling, the digested sample solution was diluted with water to 50 ml. The mercury in each solution was determined by CVAAS. When 0.5 g amounts of artificial standard soil samples spiked with a given amount of organic mercury and inorganic mercury {20 ng (as Hg) of mercury(II) chloride and methylmercury chloride} were treated by the above-mentioned procedures, the recoveries were 102% and 97.0% with the relative standard deviations of 1.0% and 2.8%, respectively. This method was successfully applied to a differential determination of mercury in sediment, soil and fish meat samples.

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