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

Authors:
  • MSMárcia Andreia Mesquita da Silva
    Márcia Andreia Mesquita da Silva
  • VFVera Lúcia Azzolin Frescura
    Vera Lúcia Azzolin Frescura
  • FAFaruk José Nome Aguilera
    Faruk José Nome Aguilera
  • ACAdilson José Curtius
    Adilson José Curtius
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Abstract
A simple and practical preconcentration method for low concentrations of Ag and Au, using cloud point extraction, is proposed. The analytes in the initial aqueous solution acidified with hydrochloric acid are complexed with ammonium O,O-diethyldithiophosphate and Triton X-114 is added as a surfactant. After phase separation, based on the cloud point of the mixture, and dilution of the surfactant-rich phase with methanol, the enriched analytes are determined by flame atomic absorption spectrometry, using discrete nebulization. After optimization of the complexation and extraction conditions, enrichment 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 the determination of Au and Ag in acidic solutions of certified reference geological materials and good agreement with the certified values was obtained.
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