THERMODYNAMIC AND ANALYTICAL STUDIES ON THE CHARGE-TRANSFER COMPLEX FORMED BETWEEN CHLORANILIC ACID AND AMINO DERIVATIVE OF METRONIDAZOLE.

Abstract

The nitro group of metronidazole was converted to the amine derivative before complexation with chloranilic acid; the charge-transfer complex was analyzed spectrophotometrically. There was a bathochromic shift in the absorption of chloranilic acid from 420 to 440 nm on the formation of the complex. The stoichiometry of complexation was found to be 1:1. The equilibrium constant for the interaction at different temperatures was determined according to Benesi-Hildebrand model. The equilibrium constant and molar absorptivities varied only slightly with temperature. The thermodynamic parameters like free energy change (ΔG), enthalpy change (ΔH ) and entropy change (ΔS ) showed that the interaction was exothermic. Quantitative analysis of four brand of metronidazole showed mean percentage recoveries of 98.78 ± SD 0.045 for charge-transfer technique and 95.93 ± SD 0.31 for the Standard method. The limits of detection (LOD) and quantitation (LOQ) were 25 ng/ml and 70 ng/ml respectively. Comparison of these techniques shows that there is no significant difference (p > 0.05) between the two methods. Charge-transfer technique is suitable for the quantitative analysis of metronidazole because it is simple, sensitive and accurate. KEY WORDS: metronidazole derivative, charge-transfer complex, chloranilic acid. Global Jnl Pure & Applied Sciences Vol.10(1) 2004: 125-131