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 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 x 10(4) l mol(-1) cm(-1). The Sandell's sensitivity of the ternary complex is 2.7 x 10(-3) mu g cm(-2). The system obeys Beer's law up to 2.0 mu g 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 mu g 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.