CATHODIC STRIPPING VOLTAMMETRY OF THE COPPER-1,10-PHENANTHROLINE COMPLEX

Cathodic stripping voltammetry of copper, based on the accumulation and reduction of its complex with 1,10-phenanthroline (phen), has been studied. The complex is reduced in two steps from Cu-I-phen and Cu-II-phen to copper amalgam at potentials of -0.43 and -0.62 V vs. Ag/AgCl, respectively. The reduction processes are strongly dependent on the pH of the solution, as well as on the concentration of the metal ion and ligand. The reduction mechanism of both complexes was established. The detection limit for copper in 0.55 mol/L NaCl with 20 min accumulation at 0.0 V vs. Ag/AgCl, measuring the reduction peak of the Cu-I-phen complex at -0.43 V vs. Ag/AgCl by SWV, was found to be about 5 x 10(-10) mol/L. The reaction parameters were calculated by square-wave voltammetry (SWV), i.e., transfer coefficients alpha(CuI-phen) = 0.31 and alpha(CuII-phen) = 0.45, and the maximum surface concentrations Gamma(CuI-phen) = (2.02 +/- 0.08) x 10-(11)mol/cm(2) and Gamma(CuII-phen) = (2.83 +/- 0.12) x 10(-12) mol/cm(2). Measurements of the copper content in natural seawater samples were performed as well.