 ISSN 0235-7216 ISSN 2424-4538 (online) |
2008 m. Nr. 3-4 Electrochemical study and thermodynamic parameters of Cd2+ complexes with some antibiotics and vitamin BX system
The polarographic technique was used to determine the stability constants and thermodynamic parameters such as enthalpy change (ΔH), free energy change (ΔG) and entropy change (ΔS) of Cd2+ complexes with neomycin, chlortetracycline, oxytetracycline, tetracycline, penicillin-V, and penicillin-G as primary ligands and vitamin BX as a secondary ligand at pH 7.30 ± 0.01 and ionic strength I = 1.0 M KNO3. The study was carried out at two different temperatures – 25 °C and 35 °C. Cd2+ complexes were formed in 1 : 1 : 1, 1: 1 : 2 and 1 : 2 : 1 ratios. The stability constant sequence of the complexes was neomycin < chlortetracycline < oxytetracycline < tetracycline < penicillin-V < penicillin-G, which can be explained by the nature of ligands and steric hindrance among metal ligands. The electrode processes were reversible and diffusion-controlled. The values of stability constants have shown that these drugs can be used to reduce Cd2+ toxicity. Keywords: electrode kinetics, stability constant, thermodynamic parameters, Cd2+–neomycin–vitamin BX system |
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