The direct and simultaneous spectrophotometric determination of Np(IV), Np(V) and Np(VI) at low concentrations (> 10" 7 M) in nitric acid (up to 3 M) and in the presence of uranyl nitrate (up to 1 M) without addition of a complexing agent is described. The splitting of the absorption peak of Np(V) at 981 nm due to the formation of a 1 : 1 binuclear complex with U(VI) and the overlap of this peak with the absorption peak of Np(IV) at 978 nm are taken into account. Limits for quantitative determination of Np(IV), Np(V) and Np(VI) are of the order of 10" 6 , 10" 7 and 10" 6 M, respectively.

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