Determination of sitafloxacin in human plasma by liquid chromatography-tandem mass spectrometry method: application to a pharmacokinetic study.

A high-performance liquid chromatographic-tandem mass spectrometric (HPLC-MS/MS) method was developed and validated to determine sitafloxacin in human plasma with dextrorphan as internal standard. Chromatographic separation was performed on a ZORBAX SB-C18 column (3.5μm, 2.1mm×100mm) with the mobile phase of methanol/water (containing 0.1% formic acid) (46:54, v/v) at a flow rate of 0.2mL/min. Quantification was performed using multiple-reaction monitoring of the transitions at m/z 410.2 → 392.2 for sitafloxacin and m/z 258.1 → 157.1 for dextrorphan, respectively. The calibration curve was linear over the range of 5-2500ng/mL with the lower limit of quantification of 5ng/mL for sitafloxacin. The intra- and inter-day precisions were less than 8.3% and the deviations of assay accuracies were within ±4.1%. Sitafloxacin was sufficiently stable under all relevant analytical conditions. This method was successfully applied to the pharmacokinetic study of sitafloxacin in healthy Chinese volunteers.