DEGRADATION KINETICS OF THE NEW ANTIBACTERIAL FLUOROQUINOLONE DERIVATIVE, ORBIFLOXACIN, IN AQUEOUS-SOLUTION

The degradation kinetics of orbifloxacin imethyl-1-piperazinyl)-4-oxoq uinoline-3-carboxylic acid] was investigated as a function of pH (1.5- 10.5), temperature (100-120 degrees C) and buffer concentration (0.05- 0.2 M) by means of high-performance liquid chromatography. The degrada tion of orbifloxacin in aqueous solution followed apparent first-order kinetics under all experimental conditions, No appreciable effect of buffer on the degradation of orbifloxacin was observed for any of the buffer species used in this study, The log k-pH profiles indicated spe cific-acid and specific-base catalyses and there were inflection point s near pH 6 and 9 corresponding to the pK(a1) and pK(a2) values, From the Arrhenius plots, the activation energies for k(H)', k(H2O)', k(H2O ), k(H2O)'' and k(OH)'' were found to be 31.9, 36.9, 23.5, 26.5 and 19 .0 kcal/mol, respectively, Arrhenius data obtained from this study sho wed that the degradation of orbifloxacin at room temperature was negli gible at all pH values studied conditions (pH 1.5-10.5),