A highly sensitive, selective and rapid liquid chromatography-electrospray ionization mass spectrometry (LC-MS) method has been developed and validated for simultaneous determination of moxifloxacin (MFX) and ketorolac (KTC) in rat plasma. Gemifloxacin (GFX) was used as an internal standard (IS). A simple protein precipitation method was used for the extraction of analytes from rat plasma. Effective chromatographic separation of MFX, KTC and GFX was achieved on a Kromasil C(18) column (100 × 4.6 mm, 5 µm) using a mobile phase consisting of acetonitrile-10 mm ammonium acetate (pH 2.5)-0.1% formic acid (50:25:25) in an isocratic elution, followed by detection with positive ion electrospray ionization mass spectrometry using target ions of [M + H](+) at m/z 402 for MFX, m/z 256 for KTC and m/z 390 for GFX in selective ion recording mode. The method was validated over the calibration range of 5-100 ng/mL for MFX and 10-6000 ng/mL for KTC. The method demonstrated good performances in terms of intra- and inter-day precision (0.97-5.33%) and accuracy (93.91-101.58%) for both MFX and KTC, including lower and upper limits of quantification. The recoveries from spiked control samples were >75% for MFX and >79% for KTC. The matrix effect was found to be negligible and the stability data were within acceptable limits. Further, the method was also successfully applied to a single-dose pharmacokinetic study in rats. This method can be extended to measure plasma concentrations of both drugs in human to understand drug interaction and adverse effects.
Copyright © 2012 John Wiley & Sons, Ltd.