A ratio derivative spectrophotometric method for the simultaneous determination of thorium and uranium

This paper addresses the development of a ratio derivative spectrophotometric method for the simultaneous determination of thorium and uranium at trace levels in 5M HNO3 with a view to find its applicability in some of reprocessed materials from thorium-uranium fuels. Arsenazo III was used a chromogenic reagent and the overlapping spectra of thorium and uranium Arsenazo III complexes are resolved by making use of the first derivative of the ratios of their direct absorption spectra. A relative error of about 1% and 2% is obtained for thorium and uranium respectively. The method is simple fast and does not require prior separation. (author)