The extraction and spectrophotometric determination of sexavalent uranium with arsenazo III in aqueous-organic media

The determination of uranium(VI) has been carried out by extraction-spectrophotometric methods based on the use of tributyl phosphate dissolved in isobutyl methyl ketone and trioctylphosphine oxide in benzene. Arsenazo III is used as the metallochromic reagent in a medium buffered with monochloroacetic acid-sodium monochloroacetate. The effect of many cations and anions on the procedures has been investigated, including the elimination of the important interference caused by plutonium.The applicability of the methods evolved has been demonstrated by the comparative analysis of a series of international secondary uranium ore standards and some other low-content uranium ores that have been analysed by independent chemical methods. The trioctylphosphine oxide-benzene-arsenazo III procedure, which has been shown to be greatly superior to the other methods, permits the direct determination of uranium(VI) in the presence of plutonium when the uranium-to-plutonium ratio is greater than 0·2 per cent. The method has also been found suitable for the determination of uranium in monazitic sands, rare earth concentrates, zirconium-bearing materials and phosphoric acid solutions of the type used for the leaching of low-grade uranium ores.