Solid phase extraction of gold(III) on silica gel modified with benzoylthiourea prior to its determination by flame atomic absorption spectrometry

A new method has been developed for the determination of gold based on separation and preconcentration using silica gel modified with benzoylthiourea. The optimum experimental parameters for preconcentration of gold, such as acid concentration, sample flow rate, eluent and matrix ions, have been investigated. Gold could be quantitatively retained in the 0.25-2.0 mol L (-aEuro parts per thousand 1) HCl and HNO3 concentrations, and then eluted completely with 0.5 mol L (-aEuro parts per thousand 1) thiourea in 1.0 mol L (-aEuro parts per thousand 1) HCl. The sorption capacity of gold(III) is 0.92 +/- 0.04 mmol g (-aEuro parts per thousand 1) with a high enrichment factor of 267. The relative standard deviation of the method, RSD%, was found as 1.2% for 0.1 mu g mL (-aEuro parts per thousand 1). The detection limit for gold was 1.4 mu g L (-aEuro parts per thousand 1). The validation of the proposed method was checked by the analysis of certified reference soil materials. The presented procedure was applied to the determination of gold in some environmental samples.