KINETIC SPECTROPHOTOMETRIC DETERMINATION OF SOME FLUOROQUINOLONE ANTIBIOTICS IN BULK AND PHARMACEUTICAL PREPARATIONS

A simple and sensitive kinetic spectrophotometric method was developed for the determination of some fluoroquinolonea antibiotics; gemifloxacin mesylate, moxifloxacin hydrochloride and gatifloxacin in bulk and in pharmaceutical preparations. The method is based upon a kinetic investigation of the oxidation reaction of the drugs with alkaline potassium permanganate at room temperature for a fixed time of 20 min for gemifloxacin and 15 min for moxifloxacin or gatifloxacin. The absorbance of the coloured manganate ion was measured at 610 nm. The absorbance-concentration plots were rectilinear over the ranges of 2.0-20, 4.0-24 and 4.0-40 mu g mL(-1) for gemifloxacin, moxifloxacin and gatifloxacin, respectively. The concentrations of the studied drugs were calculated using the corresponding calibration equations for the fixed-time method. The determination of the studied drugs by the fixed concentration and rate constant methods was also feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. The different experimental parameters affecting the development and stability of the colors were carefully studied and optimized. The proposed method was applied to the determination of the studied drugs in pharmaceutical formulations.