Spectrophotometric Determination of Gold(III) by Formation of Dicyanoaurate(I) and Its Solvent Extraction with Methylene Blue

Abstract

The proposed determination of gold(III) is based on the formation of dicyanoaurate(I) and its extraction into 1, 2-dichloroethane as an ion-pair with Methylene Blue. The optimum pH range for the formation of dicyanoaurate(I) is 2.2-7.2 under the conditions described. The absorbance of the extract is stable for at least 4 days in a glass-stoppered tube. The apparent molar absorptivity for gold is 1.08×105l mol-1 cm-1 and the Sandell sensitivity for 0.001 absorbance is 1.8×10-3μgAu cm-2 at 657nm. Linear calibration graphs are obtained over the range 2×10-7-8×10-6M gold(III) (0.4-15.8μgAu in 10ml); at the 6×10-6M gold(III) level, the relative standard deviation is 0.2%.