Solid phase extraction and spectrophotometric determination of gold

Abstract

A sensitive, selective and rapid method for the determination of gold based on the rapid reaction of gold with 5<i>-</i>(<i>p-</i>aminobenzylidene)-thiorhodanine (ABTR) and the solid phase

extraction of the colored chelate has been developed. In 0.05-0.5 mol L^-1 hydrochloric acid and emulsifier-OP medium, ABTR reacts with gold to form a red chelate of molar ratio 1:3 (gold to ABTR). This chelate has been preconcentrated by solid phase extraction with polymer-based C₁₈ cartridge and eluted from cartridge with dimethyl formamide to attain an enrichment factor of 100. In DMF medium, the molar absorptivity of the chelate is

1.23 × 10⁵ L. mol^-1. cm^-1 at 550 nm. Beer's law is obeyed in the range of 0.01-3μg mL^-1 of gold. The relative standard deviation for eleven replicate samples of 0.5 μg L^-1 gold is 2.1 8%. The detection limit, based on three times of standard deviation, is 0.02μg L^-1 in the original sample. This method has been applied to the determination of gold in water and ore with good results.