Derivative spectra and simultaneous determination of U(IV), U(VI) and Pu(III) in nitric acid solution

The second derivative spectra (2nd DS) of U(IV), U(VI) and Pu(III) in nitric acid solution in investigated and compared with each species' absorption spectra (AS). The influences of HNO3, H+ and other impurities on 2nd DS and AS of these species are discussed. Wide and intensive absorption band can be declined by derivation. On the other hand, weak but sharp absorption band can be amplified by derivation. U(IV) causes serious interference on absorption spectra of U(VI) and Pu(III) if the concentration of U(IV) is higher than the concentrations of U(VI) and Pu(III). But in 2nd DS, the characteristic peaks of U(VI) and Pu(III) can be easily discerned and U(IV) slightly affects their determinations. The height of negative peak at 415 nm can be used to determine U(VI) concentration. Either the negative peak at 584 nm or the positive peak at 665 nm can be used to determine Pu(III) concentration depending on concrete situation. The determination of U(IV) is scarcely affected by Pu(III) and U(VI), and its concentration can be determined via several peaks' height. 2.5-3.0 mol/l HNO3 is suitable for the determination with the analysis deviation below 5.0%. The low-limits of determination for Pu(III), U(IV) and U(VI) are 0.5, 0.1 and 1 mmol/l, respectively