Determination of Ag and Au in geological samples by flame atomic absorption spectrometry after cloud point extraction

A simple and practical preconcentration method for low concentrations of Ag and Au, using cloud point extraction, is proposed. The analytes in the ini tial aqueous solution acidified with hydrochloric acid are complexed with a mmonium O, O-diethyldithiophosphate and Triton X-114 is added as a surfacta nt. After phase separation, based on the cloud point of the mixture, and di lution of the surfactant-rich phase with methanol, the enriched analytes ar e determined by flame atomic absorption spectrometry, using discrete nebuli zation. After optimization of the complexation and extraction conditions, e nrichment factors of 130 for Au and 91 for Ag were obtained. The complexes have a 1:1 composition. The detection limits are 0.53 ng ml(-1) for Au and 0.46 ng ml(-1) for Ag in the initial solution. The method was. applied to t he determination of Au and Ag in acidic solutions of certified reference ge ological materials and good agreement with the certified values was obtaine d.