Development and validation of an HPLC method for the determination of gatifloxacin stability in human plasma

A simple reversed-phase high performance liquid chromatography (HPLC) method for the determination of gatifloxacin stability in human plasma was developed and validated. Using ciprofloxacin as an internal standard (IS), separation was achieved on X Terra MS C18 (3 mm x 50 mm, 5 microm) column. The mobile phase, 0.025 M disodium hydrogen phosphate (pH 3.0) and acetonitrile (80:20 v/v), were delivered at a flow rate of 1.0 ml/min. The eluent was monitored using spectrophotometeric detection at 293 nm. Plasma samples were deproteinized using Amicon Centrifree system. No interference in blank plasma or of commonly used drugs was observed. The relationship between gatifloxacin concentration and peak height ratio of gatifloxacin to the IS was linear over the range of 0.10-6.0 microg/ml. The intra-day and inter-day coefficients of variation were < or = 2.77 and < or = 4.59%, respectively. The extraction recovery of gatifloxacin and the IS from plasma samples was > or = 85%. Gatifloxacin was found to be stable for at least 5 h at RT, 7 weeks at -20 degrees C, and after 3 freeze-thaw cycles in plasma; 16 h at RT and 48 h at -20 degrees C in deproteinized plasma; and 24 h at RT and 7 weeks at -20 degrees C in phosphate buffer.