Photodegradation of Moxifloxacin in Aqueous and Organic Solvents: A Kinetic Study |
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| Authors: | Iqbal Ahmad Raheela Bano Syed Ghulam Musharraf Sofia Ahmed Muhammad Ali Sheraz Qamar ul Arfeen Muhammad Salman Bhatti Zufi Shad |
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| Institution: | .Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Toll Plaza, Super highway, Gadap Road, Karachi, 74600 Pakistan ;.H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, 75270 Pakistan |
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| Abstract: | The kinetics of photodegradation of moxifloxacin (MF) in aqueous solution (pH 2.0–12.0), and organic solvents has been studied. MF photodegradation is a specific acid-base catalyzed reaction and follows first-order kinetics. The apparent first-order rate constants (kobs) for the photodegradation of MF range from 0.69 × 10−4 (pH 7.5) to 19.50 × 10−4 min−1 (pH 12.0), and in organic solvents from 1.24 × 10−4 (1-butanol) to 2.04 × 10−4 min−1 (acetonitrile). The second-order rate constant (k2) for the H+]-catalyzed and OH−]-catalyzed reactions are 6.61 × 10−2 and 19.20 × 10−2 M−1 min−1, respectively. This indicates that the specific base-catalyzed reaction is about three-fold faster than that of the specific acid-catalyzed reaction probably as a result of the rapid cleavage of diazabicyclononane side chain in the molecule. The kobs-pH profile for the degradation reactions is a V-shaped curve indicating specific acid-base catalysis. The minimum rate of photodegradation at pH 7–8 is due to the presence of zwitterionic species. There is a linear relation between kobs and the dielectric constant and an inverse relation between kobs and the viscosity of the solvent. Some photodegraded products of MF have been identified and pathways proposed for their formation in acid and alkaline solutions.KEY WORDS: acid-base catalysis, kinetics, moxifloxacin, photodegradation, rate–pH profile, solvent effect |
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