Automated Method for the Selective Determination of Gold by On-Line Solvent Extraction and Reversed Micellar-Mediated Luminol Chemiluminescence Detection

A new method based on the direct coupling of on-line solvent extraction with chemiluminescence (CL) of luminol in reverse micelles is proposed for the determination of gold(III) in a reverse-flow injection system. In the on-line process, gold(III) is extracted from aqueous hydrochloric acid solution with tri-n-octylphosphine oxide in chloroform, followed by separation through a microporous Teflon membrane. A reversed micellar system of cetyltrimethylammonium chloride-water (buffered with sodium carbonate)-6:5 (v/v) chloroform-cyclohexane was used as a medium for the CL reaction. Linear calibration for gold was established over the concentration range 10-5000 ng ml⁻¹ and the detection limit was 1 ng ml⁻¹. Much higher tolerable levels of potential interfering metal ions were achieved for the present on-line procedure. The present method was applied to the analysis of industrial samples of silver-based alloy.