Spectrophotometric determination of uranium(IV) with thorin and N-hydroxy-N,N′-diphenylbenzamidine

Abstract

A simple method for the selective and sensitive spectrophotometric determination of uranium(IV) is described. The method is based on the reaction of U^IV with thorin and subsequent extraction of the red–orange complex with N-hydroxy-N,N′-diphenylbenzamidine (HDPBA) in benzene as an interfacial complex at pH 2.2. The interfacial complex, dissolved in ethanol, exhibits maximum absorbance at 490 nm with a molar absorptivity of 8.8 × 10⁴ l mol^–1 cm^–1. The Sandell's sensitivity of the ternary complex is 2.7 × 10^–3µg cm^–2. The system obeys Beer's law up to 2.0 µg ml^–1 of U^IV. Various analytical parameters were studied to establish the optimum conditions for the determination of U^IV. The method is selective as none of the common metal ions and anions tested interfere. The detection limit of the method is 0.09 µg ml^–1 of U^IV. The relative standard deviation of the method for ten replicate measurements is 1.5%. The method was successfully applied to the recovery of uranium from standard ores, geological samples and synthetic matrices.