DETERMINATION OF TRACE AMOUNTS OF SILVER AND GOLD IN SOME SEDIMENTS BY AAS AFTER PRECONCENTRATION ON ACTIVATED CARBON IMPREGNATED WITH DITHIZONE

Ag(I) and Au(III) are adsorbed on activated carbon (AC) impregnated with dithizone (AC-Dz). A simple and rapid method for determining trace amounts of Ag(I) and Au(III) by metal furnace AAS using direct heating of metals adsorbed onto AC was investigated. To 100 cm(3) of sample solutions containing less than 0.1 mu g of Ag(I) and 0.5 mu g of Au(III), respectively, 25 mg of AC-Dz is added. Ag(I) and Au(III) are adsorbed as Dz-complexes after adjusting the pH to 1.5 for Ag(I) and 3.0 for Au(III). After separation of AC from the aqueous phase through a membrane filter, an AC suspension is dispersed in 5.0 cm(3) of water by mixing with shaking. Then, aliquots (10 mm(3)) of AC-suspension are directly injected into the metal furnace, and the Ag and Au peak heights are measured under optimal instrumental operating conditions. The determination limits (S/N=3) were 0.005 mu gAg/100 cm(3) and 0.04 mu gAu/100 cm(3). Relative standard deviations were 3.2% and 2.6%, respectively. The proposed method has been applied to the determination of Ag and Au in riverbottom and sea floor sediments.