Voltammetric Study of Cu(II) in Presence of Aspartic Acid and L-Phenyl Alanine at Different pH Media

The voltammetric study of Cu (II) in presence of aspartic acid (Aa) and L-phenyl alanine (Pa) respectively has been carried out in buffer solution of different pH, scan rate and variation of Aa or Pa concentration. Cu(II) in presence of Aa and Pa has been found to undergo two anodic peaks follows two step two electron transfer anodic reaction. The peak positions of the voltammogram of Cu(II) in presence of Aa or Pa shifted with respect to that of uncoordinated Cu(II). The peak current of Cu(II) with ligands (Aa, Pa) decrease significantly compared with that of uncoordinated Cu(II) in the same experimental conditions. These behaviors may ascribe the formation of complex of Cu(II) with Aa and Cu(II) with Pa. The linear behavior of peak current with the square root of scan rate of Cu complexes indicates that the electrochemical processes are diffusion controlled. The effects of pH of Cu-Aa and Cu-Pa complexes were studied by varying pH from 3.5 to 5.5. The oxidation peak current increases with the decrease in pH. At higher pH (pH>7) the complexes were almost electroinactive. This attributed that the electrochemical oxidation of the complexes are facilitated in lower pH media. The slope of the plots of Ep against pH of Cu-Aa and Cu-Pa complexes are 35-39 mV, indicates that the oxidation of Cu-Aa and Cu-Pa complexes proceeded via 2e−/2H+ processes. The complexes were formed by the addition of Aa or Pa into Cu(II) and the maximum interaction has been found for 1:3 molar ratio at pH 3.5. The mode of interaction of Aa and Pa with Cu(II) has been found to be similar.