Study of Electrode Kinetics of Zn2+–l-Amino Acids–γ-Picoline Mixed System

Abstract

Abstract Polarography was used to determine the stability constants (log β) of ternary complexes of Zn2+ with l-lysine, l-ornithine, l-threonine, l-serine, l-phenylglycine, l-phenylalanine, l-glutamic acid, and l-aspartic acid as primary ligands and γ-picoline as secondary ligand at pH = 8.50 ± 0.01 and ionic strength μ = 1.0 mol dm−3 NaClO4 at 25 °C. The waves of Zn and its complexes were quasireversible. Zn formed 1 : 1 : 1, 1 : 1 : 2, and 1 : 2 : 1 complexes. The kinetic parameters viz. the standard rate constant (k), degree of irreversibility (λ), and charge transfer coefficient (α) were also determined. The trend of the stability constants of Zn2+complexes with these amino acids and γ-picoline is l-lysine < l-ornithine < l-threonine < l-serine < l-phenylglycine < l-phenylalanine < l-glutamic acid < l-aspartic acid, which is explained on the basis of the sizes and basicities of the primary ligands.