Extraction-spectrophotometric determination of indium with salicylideneamino-2-thiophenol

Abstract

The solvent extraction-spectrophotometric determination of indium and gallium with salicylideneamino-2-thiophenol (SATP) was studied. Indium reacts with SATP in the presence of ο-phenanthroline(ο-phen) to form a ternary complex, which can be extracted quantitatively into chloroform. Under the optimum conditions Beer's law holds up to 160 μg of indium, and up to 40 μg of gallium in 10 ml of chloroform, respectively. When the pH's of the aqueous phase were in the range of 4.66.0 for the indium ternary complex and 4.55.8 for the gallium chelate, a constant absorbance was obtained, and extractability was greater than 99% for the indium ternary complex. Many elements interfered with the determination of indium and gallium. Silver was masked with thiourea, and gold masked with L-ascorbic acid. Vanadium and gallium were masked by tartaric acid. However, copper and palladium must be removed before analysis. The standard procedure is as follows: Take (1030) ml of a sample solution containing less than 160 μg of indium. Add 1 ml of a buffer solution (1 M acetic acid and 1 M sodium acetate) and 3 ml of a 0.1% ο-phen solution. Adjust the pH to 5.0. Then add 1 ml of a 0.1% SATP (ethanolic solution) and dilute to about 50 ml with water. Extract the indium complex with 10 ml of chloroform by shaking for 3 min. Measure the absorbance of chloroform phase at 425 nm (the molar absorption coefficient, 1.1 × 10⁴ 1 mol^-1 cm^-1).