Simultaneous derivative spectrophotometric determination of thorium and uranium in a micellar medium

Derivative photometric methods for trace analysis of Th(IV) and UO₂(II), and their simultaneous determination in mixtures using 5,8-dihydroxy-1,4-naphthoquinone in a micellar medium are reported. Molar absorptivity and Sandell's sensitivity of 1:2 Th(IV) and 1:1 UO₂(II) complexes at their λ_max, 614.5 nm and 637.0 nm are, 1.19 × 10⁴ 1/mol/cm and 1.12 × 10⁴ 1/mol/cm and 1.95 × 10^?2 μg/cm² and 2.13 × 10^?2 μg/cm² μg/cm², respectively. Calibration graph is linear over the range 9.28 × 10^?2?18.56 μg/ml of Th(IV) and 9.52 × 10^?2?19.04 μg/ml of UO₂(II). Though presence of Th(IV) and UO₂(II) causes interference in each others determination, 9.28 × 10^?1?9.28 μg/ml Th(IV) and 9.52 × 10^?1?9.52 μg/ml UO₂(II) when present together, can be simultaneously determined using derivative spectra.