Determination of caderofloxacin lactate in rat plasma by high-performance liquid chromatography–mass spectrometry and its application in rat pharmacokinetic studies

A sensitive liquid chromatography–electrospray ionization mass spectrometric (LC–ESI-MS) method for the quantification of a newly active quinolone carboxylic acid caderofloxacin lactate in rat plasma was developed and validated after precipitation method with methanol. Chromatographic separation was achieved on a reversed-phase Shimadzu 2.0 μm C18 column (150 mm × 2.00 mm) with the mobile phase of methanol–0.02% formic acid and step gradient elution resulted in a total run time of about 10.0 min. The analytes were detected by using an electrospray positive ionization mass spectrometry in the selected ion monitoring (SIM) mode. A good linear relationship was obtained in the concentration range studied (5–2000 ng/mL) (r = 0.9998). The lowest limit of quantification (LLOQ) was 5 ng/mL and the lowest limit of detection (LLOD) was 2 ng/mL. Average recoveries ranged from 88.80 to 93.05% in plasma at the concentrations of 10, 100 and 1000 ng/mL. Intra- and inter-day relative standard deviations were 4.01–7.30 and 4.15–7.51%, respectively. This method was successfully applied in the pharmacokinetic studies in rats.