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  • 1 M. S. University of Baroda Analytical Laboratories, Pharmacy Department, Faculty of Technology and Engineering Kalabhavan 390001 Baroda (India)
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A selective method for the solvent extraction and spectrophotometric determination of uranium(VI) is described. Uranium can be extracted into chloroform at pH 6.0 with N-m-chlorophenyl-2-theno-hydroxamic acid (N-m-CPTHA) and determined by spectrophotometry using 1-(2-pyridylazo)-2-naphthol (PAN). The molar absorptivity is 1.50·104 1·mol–1·cm–1 at 560 nm. The system obeys Beer's law within the range 0.95–20.00 ppm of uranium. Alternatively, a back-extraction procedure was also developed in which uranium is back-extracted by nitric acid and estimated spectrophotometrically using Arsenazo III. The molar absorptivity is 2.0·104 1·mol–1·cm–1 at 665 nm. The parameters concerning the optimum conditions for the analytical method are discussed. The proposed method is applied precisely for the determination of uranium in rock and sea water samples.