Electroanalytical chemistry of cadmium complexes of amino acids at the ionic strength of seawater (0.70 M NaCLO4): Part II

The complexation of cadmium with naturally occurring amino acids was studied at the ionic strength of seawater (0.70 M in sodium perchlorate medium) and at 25±0.1°C by differential pulse polarography and potentiometry with a glass electrode.The Miniquad program was used to analyse and refine the results of the potentiometry.Although the stability of the complexes is very similar since the chelate groups of the ligands are the same, the rate of dissociation of the complexes can be different.The kinetic aspect has been studied by cyclic voltammetry which is under the influence of the type of adsorption. When this is strong the diffusion and adsorption peaks are well separated and, in principle the rate constant of dissociation of the complex can be determined. If there is weak adsorption the diffusion peak is distorted by adsorption and kinetic studies cannot be done. the adsorption of the ligands themselves has been studied by ac polarography at a 90° angle phase and it has been noticed that ligands with π bonds, sulphur groups or with long hydrocarbon chains are more adsorbed than those without.