BIOANALYTICAL METHOD DEVELOPMENT, VALIDATION AND QUANTIFICATION OF METAXALONE BY LIQUID CHROMATOGRAPHY TANDEM MASS SPECTROMETRY IN RAT PLASMA

A simple, highly sensitive, precise and accurate high-performance liquid chromatographic (LCMSMS) method with mass detection was developed and validated for the rapid quantiication of metaxalone (CAS Registry No, 1665-48- 1) in rat plasma samples. The chromatographic separation was achieved with a reverse phase column Agilent XDB C18 (4.6×100 mm, 5µ) and the mobile phase consisted of methanol and 5 mm ammonium acetate buffer (80:20 v/v) as eluent, at a low rate of 0.6 mL/min. Phenytoin (CAS Registry no, 57-41-0) was used as an internal standard. The efluence was ionized by positive electrospray ionization and measured by mass spectrometry. The retention time of metaxalone and phenytoin were found to be 1.60 and 1.83 min respectively. The calibration curve was linear (r2 > or = 0.99) ranging from 0.98 to 998 ng/ml and the lower limit of quantiication was 0.98 ng/mL. Interday and Intraday precision were lower than 5% (CV) and accuracy ranged from 90 to 110% in terms of percent accuracy. Mean extraction recovery was found to be above 82%. The method was successfully demonstrated for evaluation of pharmacokinetic proile of metaxalone in male Sprague dawley rats and validated for excellent selectivity, accuracy, precision, recovery and stability. Keywords: Electrospray Ionization; Metaxalone; HPLC; Mass detection; Rat plasma; Validation.