Stability constants and thermodynamic parameters of cadmium complexes with sulfonamides and cephapirin

Abstract

Stability constant (log `) and thermodynamic parameters of Cd 2+ complexes with sulfon- amide and cephapirin were determined by Polarographic technique at pH = 7.30 ± 0.01 and µ = 1.0 M KNO 3 at 250°C. The sulfonamides were sulfadiazine, sulfisoxazole, sulfamethaxazole, sulfamet- hazine, sulfathiazole, sulfacetamide and sulfanilamide used as primary ligands and cephapirin as sec- ondary ligand. Cd 2+ formed 1:1:1, 1:2:1 and 1:1:2 complexes. The nature of electrode processes were reversible and diffusion controlled. The stability constants and thermodynamic parameters (® G,® H and® S) were determined. The formation of the metal complexes has been found to be spontaneous, exothermic in nature, and entropically unfavourable at higher temperature. Keyword: polarography; stability constant; sulfonamide; cephapirin; thermodynamics.