Investigation of the Reaction of Gold(III) with 2‐[2‐(4‐Dimethylamino‐Phenyl)‐Vinyl]‐1,3,3‐Trimethyl‐3H‐Indolium. Application for Determination of Gold

Abstract

A new, simple, rapid, sensitive, efficient and low‐cost spectrophotometric procedure for the determination of gold was developed. The method is based on the reaction of [AuCl4]− with 2‐[2‐(4‐dimethylaminophenyl)‐vinyl]‐1,3,3‐trimethyl‐3H‐indolium reagent to form a colored ion associate extractable by various organic solvents. The molar absorptivity of the ion associates is in the range (5.7–9.2) × 104 L mol−1 cm−1 depending on the extractant. Butyl acetate was chosen as the extractant. The optimum reaction conditions were established: pH 2–4, concentration of the dye reagent (0.8–1.5) × 10−4 mol L−1. The determination of gold is not hindered even by a 1000‐fold concentration of Ni and Co; a 500‐fold concentration of Pb and Zn; a 100‐fold concentration of Bi, Cu, Cd, Pt, Rh and Ru; or a 20‐fold concentration of Ag. The established method was applied to the determination of gold in model samples and enriched polymetallic ores.

Spectrophotometric Determination of Gold(III) Using 2-Hydroxy-3-Methoxy Benzaldehyde Thiosemicarbazone as a Chromophoric Reagent

“…Among the several instrumental techniques spectrophotometric methods for the determination of metal ions have an attractive attention due to their simplicity and low operating costs. A variety of spectrophotometric methods for the determination of gold have, therefore, been reported which includes different chromophoric reagents, 2-[2-(4-dimethylamino-phenyl)-vinyl]-1,3,3-trimethyl-3H-indolium [1], bis(salicylaldehyde) orthophenylenediamine [2], 5-(4-carboxylphenyl-azo)-8-hydroxyquinoline [3], ethopropazine hydrochloride and isothipendyl hydrochloride [4], morin [5], and 2-carboxyl-1naphthalthiorhodanine [6].…”