Flow-injection spectrophotometric determination of gold using 5-(4-sulphophenylazo)-8-aminoquinoline

Gold (0–75 μg ml −1) was determined spectrophotometrically at 605 nm in a flow injection (FI) system based on the reaction of gold(III) and 5-(4-sulphophenylazo)-8-aminoquinoline (SPA) in the presence of cetyltrimethylammonium bromide (CTAB). The carrier stream was 1% (w/v) disodium ethylenediaminetetraacetate and the reagent streams were 2.0 × 10 −4 M SPA and 0.6% (w/v) sodium hydroxide solution. The sample solution was mixed with 0.2% (w/v) CTAB solution prior to injection. The various chemical and physical variables were optimised and a study of interfering ions was carried out. The relative standard deviation for the determination of 5 μg ml −1 gold was 0.9% ( n = 10) and the limit of detection (blank signal plus three times the standard deviation of the blank) was 1.1 μg ml −1, both based on injection volumes of 60 μl. The method has been successfully applied to the determination of gold in ores and anode slimes.