Reversed-phase foam chromatography : Chemical enrichment and separation of gold in the tributylphosphate-thiourea-perchloric acid system

Gold(III) is quantitatively extracted from acidic solution of thiourea into tri-n-butyl phosphate (TBP). The extracted species contains one molecule of thiourea and four molecules of TBP for each atom of gold. On short columns of TBP-loaded polyurethane foam, gold(III) can be separated from many other elements by retention from 0.1 M perchloric acid solution containing 3% thiourea and 1% sodium perchlorate. Flow-rates of 50–60 ml min^?1 are possible. Trace amounts of gold can be separated quantitatively from high concentrations of Zn²⁺, Co²⁺, Ni²⁺, Fe³⁺, Sb³⁺, Cu²⁺, Bi³⁺ and Pd²⁺, which have a negligible effect on the rate of adsorption of the gold-thiourea complex. The chemical enrichment of gold from dilute aqueous solutions is also possible.