Column preconcentration of gold by adsorbing AuCl ⁻₄ onto methyltrioctyl ammonium chloride–naphthalene and subsequent atomic absorption spectrometric determination

Abstract

A sensitive, selective and simple preconcentration method for ultra-trace gold determination has been developed that uses naphthalene–methyltrioctyl ammonium chloride (Aliquat 336s) as an adsorbent. Gold, in the form of AuCl ⁻₄ , was retained by the adsorbent in the column at a flow rate of 1 ml min⁻¹. After filtration, the solid mass consisting of the gold complex and naphthalene was dissolved out of the column with 5 ml of N,N-dimethylformamide (DMF), and the metal was then determined by atomic absorption spectrometry. In the initial solution, the calibration graph of absorbance versus gold concentration was found to be linear in the range 0.5–150 ng ml⁻¹ Au(III) with r=0.997 (n =9), and the 3 s detection limit was 0.428 ng ml⁻¹. The relative standard deviation for eight replicate measurements of 20 μg of gold was 2.14%. Preconcentration factors of 390 and 650 were achieved using 5 ml and 3 ml of DMF, respectively. The proposed method was successfully applied to the determination of gold in wastewater, processed pool water, slurry pool water, and raw well-water from the Moteh gold mine, and synthetic samples.