Utility of solid phase extraction for spectrophotometric determination of gold in water, jewel and ore samples

A highly sensitive, selective and rapid method for the determination μg L ^-1 level of Au(III) based on the rapid reaction of Au(III) with 2,3-dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) and the solid phase extraction of the colored complex with a reversed phase polymer-based C18 cartridge have been developed. The DCHNAQ reacted with Au(III) to form a violet complex of a molar ratio 3:1 [DCHNAQ to Au(III)] in the presence of 5.0 M of phosphoric acid solution and Triton X-100 medium. This complex was enriched by the solid phase extraction with a polymer-based C18 cartridge. The enrichment factor of 100 was achieved. The molar absorptivity of the complex is 2.73 × 10 ⁵ l mol ^-1 cm ^-1 at 633 nm in the measured solution. The system obeys Beer's law in the range of 0.02-1.30 μg ml ^-1, whereas the optimum concentration ranges obtained from Ringbom plot was 0.08-1.24 μg ml ^-1. The relative standard deviation for ten replicates sample of 0.6 μg ml ^-1 level is 1.28%. The detection and quantification limits, are 6.1 and 19.5 ng ml ^-1 in the original sample. This method was applied to the determination of gold in water, jewel and ore samples with good results comparing to the GFAAS method.