Colour reaction of gold with 5-(4-sodium sulphonatephenylazo)-8-aminoquinoline and its analytical application

The synthesis of 5-(4-sodium sulphonatephenylazo)-8-aminoquinoline (SPAQ) is described, and a simple, rapid, selective and sensitive new spectrophotometric method for determination of gold is developed. SPAQ reacts with gold(III), and in the presence of cetyl trimethyl ammonium bromide cationic surfactant and upon making the solution alkaline, forms a blue-green 1:3 (metal:ligand) with an absorption maximum at 605 nm. Beer's law is obeyed over the concentration range 0–2 μg/ml gold. The molar absorptivity and Sandell's sensitivity of the method are 1.48 × 10 5 1.mole −1.cm −1 and 0.0013 μg/cm 2, respectively. The interference of various ions has been studied and the method has been used for the determination of microamounts of gold in ores and anode slimes.