THERAPEUTIC MONITORING OF LEVOFLOXACIN: A NEW LC-MS/MS METHOD FOR QUANTIFICATION OF LEVOFLOXACIN IN HUMAN PLASMA

A simple and sensitive liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method for the quantification of levofloxacin in human plasma was developed and validated. The separation was performed on a Zorbax SB-C18 column under isocratic conditions using a mobile phase of 17:83 (v/v) acetonitrile and 0.1% (v/v) formic acid in water at 50 degrees C with a flow rate of 1 mL/min. The detection of levofloxacin was performed in multiple reaction monitoring (MRM) mode using an ion trap mass spectrometer with electrospray positive ionisation. The human plasma samples (0.1 mL) were deproteinised with methanol and aliquots of 1 mu L from supernatants obtained after centrifugation were directly injected into the chromatographic system. The method shows a good linearity (r(2) > 0.99), precision (CV < 11%) and accuracy (bias < 4.7%) over the range of 0.1-10.0 mu g/mL plasma. The lower limit of quantification (LLOQ) was 0.1 mu g/mL and the recovery was between 95.2-104.5%. The method is not expensive, it needs a minimum time for plasma sample preparation and has a run-time of 1.3 min for instrument analysis (retention time of levofloxacin was 0.9 min). The developed and validated method is very simple, rapid and efficient, with wide applications in clinical level monitoring, pharmacokinetics and bioequivalence studies of levofloxacin.