A derivative spectrophotometric method has been developed for the simultaneous determination of uranium and plutonium at trace
levels in various process streams in 3M HNO3 medium using Arsenazo III. The method was developed with the objective of measuring both uranium and plutonium in the same
aliquot in fairly high burn-up fuels. The first derivative absorbances of the uranium and plutonium Arsenazo III complexes
at 632 nm and 606.5 nm, respectively, were used for their quantification. Mixed aliquots of uranium (20–28 μg/ml) and plutonium
(0.5–1.5 μg/ml) with U/Pu ratio varying from 25 to 40 were analysed using this technique. A relative error of about 5% was
obtained for uranium and plutonium. The method is simple, fast and does not require separation of uranium and plutonium. The
effect of presence of many fission products, corrosion products and complexing anions on determination of uranium and plutonium
was also studied.