GRAPHITE-FURNACE AAS DETERMINATION OF MER CURY IN WATER SAMPLES AFTERPRECONCENTRATION WITH ONE-DROP SOLVENT

An effective method for the determination of mercury at ng/I levels in water sample is described. Mercury is extracted with 1,5-diphenylthio carbazone (dithizone) into carbon tetrachloride (CCl4). With hydrophob ic filter paper; the organic phase is transferred to a Teflon beaker c ontaining a micro volume of dimethyl sulfoxide (DMSO, a high boiling-p oint solvent); then CCl4 is removed by evaporation in a water bath at ca. 40 degrees C. Mercury is concentrated in the residual DMSO and det ermined by graphite furnace AAS. The sensitivity and stability of merc ury atomic absorption were enhanced in the presence of DMSO and dithiz one due to matrix modification. A preconcentration factor of 15000 tim es was obtainable using 3 mi of CCl4 and 0.1 ml of DMSO. When 1000 mi of the sample was used, the lower limit of determination(10 sigma) was 1.3 ng/l, and the relative standard deviation was 6.3% (10 ng/l, n=8) . The proposed method was applied to the determination of total mercur y in surface snow and river water after acid digestion using potassium peroxodisulfate. Water samples were collected in glass bottles contai ning sulfuric acid and potassium permanganate, and analyzed within 4 d ays.