ACTA Pharmaceutica Sciencia 2011 , Vol 53 , Num 1
SPECTROPHOTOMETRIC STUDIES OF THE CHARGE-TRANSFER COMPLEXATION BETWEEN LUMEFANTRINE AND CHLORANILIC ACID IN ACETONITRILE
OLAJİRE A ADEGOKE, CHİNEDUM P BABALOLA, PETER O K ISAAC, OLAYİNKA A KOTİLA
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria A simple, rapid and accurate spectrophotometric method has been developed for the determination of lumefantrine in bulk and dosage forms. The method involves the utilization of lumefantrine as n-electron donor and chloranilic acid (CAA) as π-electron acceptor with the consequent formation of a stable chargetransfer (CT) complex which absorbed visible light maximally at 520 nm. Factors controlling the formation of the CT complex were studied and optimized. Optimal detector response was obtained at a mole ratio of 1:1 between lumefantrine and CAA at a temperature of 30oC and 5 minutes reaction time in acetonitrile as solvent. Under the optimal conditions obtained the assays of the CT complex were linear over the range 10 -60 μgmL-1with a correlation coefficient of 0.9980 and the method was accurate and precise (inter-day recoveries = 97.64 ± 1.18 with RSD of 1.21%). Benesi-Hildebrand equation has been used to calculate the formation constant and the molar absorptivity of the CT band. The CT complex was associated with large formation constant (4.677 x 109) and molar absorptivity (1.403 x 103 M-1cm2). Transition energy, free energy change (ΔG0), oscillator strength (f), transition dipole moment (μEN), resonance energy (RN), ionization potential (ID) and dissociation energy (W) of the CT band were also determined and related to the stability of the formed complex. The method was successfully applied to the estimation of lumefantrine in combination products with artemether (artemether-Lumenfantrine: A-L) and there was no significant difference (p>0.05) between the results when compared with classical nonaqueous titration method. The developed procedure is simple, accurate and precise and could find application as a rapid spectrophotometric method for the assay of lumefantrine. Keywords : LUMEFANTRINE, CHLORANILIC ACID, CHARGE-TRANSFER COMPLEXATION, SPECTROPHOTOMETRIC STUDIES, DRUG ANALYSIS

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