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

A simple method for the selective and sensitive spectrophotometric determination of uranium(IV) is described. The method is based on the reaction of UIV 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 x 104 1 mol-1 cm-1. The Sandell's sensitivity of the ternary complex is 2.7 x 10-3 μg cm-2. The system obeys Beer's law up to 2.0 μg ml-1 of UIV. Various analytical parameters were studied to establish the optimum conditions for the determination of UIV. 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 UIV. 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. (author)