DETERMINATION AND CHARACTERIZATION OF SELECTED FLUOROQUINOLONES OXIDATION PRODUCTS UNDER POTASSIUM PERMANGANATE TREATMENT

A simple, sensitive and reproducible ultra-performance liquid chromatography (UPLC) method for the determination of: danofloxacin. enrofloxacin, marbofloxacin, orbifloxacin and pefloxacin oxidation stability under permanganate treatment in acidic conditions at pH from 3.0 to 6.0, was developed. Chromatographic separations were carried out using the Acquity UPLC BEH C-18 column; (2.1 x 100 mm, 1.7 mu m particle size). The column was maintained at 40 degrees C, and eluted under gradient conditions using from 100% to 75% of eluent A over 10 min for danofloxacin, enrofloxacin, marbofloxacin, orbifloxacin or 95% to 75% of eluent A over 10 min for pefloxacin, at a flow rate of 0.3 mL/min. Eluent A: 1% (v/v) formic acid in water; eluent B: 0.1% (v/v) formic acid in acetonitrile. Satisfactory resolution was obtained for oxidation products. The correlation coefficients and determination coefficients (R-2) obtained for linear model for all examined fluoroquinolones were greater than 0.99. Linearity range was observed in the concentration range 0.06-0.13 mg/mL. Sensitivity of the method was good. The LOD and LOQ values were found to be 0.01 mg/mL and from 0.02 to 0.04 mg/mL, respectively. Good precision and intermediate precision with %RSD less than 2.0% was observed. The oxidation processes followed kinetic of the second order reaction and depended upon solution acidity. Oxidation of fluoroquinolones proceeded at piperazine moiety yielding respective hydroxy and oxo analogs, and leaving the quinolone fragment intact. Structures of products formed were assigned on a basis of UPLC/MS/MS fragmentation pathways.