Determination of moxifloxacin in human plasma by liquid chromatography electrospray ionization tandem mass spectrometry.

Moxifloxacin is an advanced-generation, 8-methoxy fluoroquinolone that is active against a broad spectrum of pathogens, including antibiotic resistant Streptococcus pneumoniae. Development of a rapid, sensitive and selective method for the determination of moxifloxacin in human plasma is essential for understanding the pharmacokinetics of the drug when administered orally or intravenously. Solid phase extraction (SPE) using Oasis(R) HLB was used to extract moxifloxacin and the internal standard lomefloxacin from plasma. A method based on liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) was developed and validated to quantitate moxifloxacin in human plasma. The precursor and major product ion of the analyte was monitored on a triple quadrupole mass spectrometer with positive ion electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode. Mechanisms for the formation of collision-induced dissociation (CID) products of moxifloxacin are proposed. Linear calibration curves were generated from 1 to 1000 ng/ml with coefficients of determination greater than 0.999. The inter-day and intra-day precision (% CV) was less than 11.3% and accuracy (% error) was less than 10.0% for moxifloxacin. The limit of detection (LOD) for the method was 50 pg/ml based on a signal to noise ratio of 3.