Voltammetric behaviour of the neptunyl succinate complex at the rotating pyrolytic graphite electrode

Abstract

The voltammetry of the neptunium (VI) succinate complex has been investigated over the pH range 0·7–7.0. A reversible, one-electron wave was obtained when the pH was less than 5·8. When the pH was greater than 5·8, an irreversible wave was obtained. In the pH range 0·7–4·4, the half-wave potential is a function of the pH, whereas in the pH range 4·4–7·0 it is independent of the pH. The metal/ligand ratio was found to be 1:2 by conductometric and amperometric titrations. The limiting current is proportional to the concentration of the neptunium (VI) from 1·30 × 10 −4 to 1·63 × 10 −3 M with a relative standard deviation of 7·5%. The diffusion coefficient is 0·30 × 10 −5 cm 2/s at pH 2·5 and 0·18 cm 2/s at pH 5·4. The stability constant of the neptunylsuccinat ion is 7·4 × 10 −5.