2,3-Dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline as an Analytical Reagent for the Spectrophotometric Determination of Microamount of Gold(III)

Abstract

Abstract The synthesis, spectral characteristics, and analytical application of 2,3-Dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) are described. A simple, rapid, selective, and sensitive spectrophotometric method for the determination of microgram amounts of gold, alone, or in the presence of associated metals, is developed, based on the color reaction between the metal ion and the reagent. The yellowish brown complex (λmax = 575 nm) has stoichiometric ratio (1 : 1) [metal : ligand] over the pH range 3.4 to 7.0. Beer’s law is obeyed over the concentration range 0.1—6.9 μg cm−3 of gold. The molar absorptivity and Sandell’s sensitivity of the method are 1.52 × 104 dm3 mol−1 cm−1 and 0.016 μg Au cm−1 respectively. The relative standard deviation for six replicate determination of 2.95 μg cm−3 of gold(III) is 1.37%. The interference of various ions has been studied and conditions were developed for the determination of gold in alloys and some synthetic samples without the need for extraction or heating.