Effect of halide/pseudohalide anions on the association and semimicroextraction of substituted chloroaurates with a symmetric carbocyanine dye: A complex study and analytical application

Abstract

The present work is focused on investigating the interaction of halide/pseudohalide-substituted chloroaurates with a symmetric carbocyanine dye 1,3,3-trimethyl-2-[5-(1,3,3-trimethyl-1,3-dihydroindol-2-yliden)-penta-1,3-dienyl]–3H-indolium chloride (DIDC), and on the optimization of formation and further semimicroextraction of Au ion associate for the spectrophotometric Au determination at 647 nm. Ligand changing in chloroaurates significantly improves the sensitivity and selectivity of the method. The molar absorptivity of the ion associates has been found in the range (10.7–15.6) × 10−4 L mol−1 cm−1, depending on the ligand. For the Au determination, a novel analytical system has been developed. The appropriate reaction conditions were found to be: the N3− ligand, pH 5.0, 5 × 10−5 mol L−1 of DIDC, amyl acetate as extraction solvent. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.10 µg mL−1 and 0.31 µg mL−1 of Au, respectively. The proposed method was applied to the determination of gold in artificial and pharmaceutic samples with reliable results. QTAIM analysis of DIDC chloroaurates electron density calculated at the CPCM(water)-B3LYP/ma-def2-SVP level of theory allowed to build a selectivity row which correlates well with the experimental data.