Polarographic studies of lead(II) complexes with triethylenetetramine- N, N, N,′ N,″ N″', N″'-hexaacetic acid

Abstract

Three different polarographic waves of lead(II)-TTHA system explored from limiting currents, half-wave potentials and reciprocal slopes of the log-plots and analysed to determine the kinetic parameters. The reduction for the first wave (A) was reversible or irreversible involving partially kinetic-controlled reaction with the change of pH and molar ratio of lead(II): TTHA. The second wave (B) is proposed to occur as the results of the adsorption of dissociated ligand anion on the dme. The third wave (C) at more negative potential ( -0.831 V vs sce, pH = 4.32) was assigned to an irreversible reduction of the complex PbH 2L (pH ⩽ 5.27) or PbHL(pH > 5.27). The mechanisms of the electrode reaction of wave (C) are expressed as follows. ▪ where k j denotes the rate constant of electrodics. For the mechanisms (I) and (II) the values of k j were determined from the dependence of the half-wave potential on the hydrogen ion concentration. They were 2.98 X 10 t-3 and 1.45 X 19 t-9 cm/s, respectively.