Enantiospecific determination of arotinolol in rat plasma by LC-MS/MS: Application to a stereoselective pharmacokinetic study

A highly sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and fully validated for quantification of arotinolol enantiomers in rat plasma using haloperidol as the internal standard. After solid phase extraction of 50.0 mu L rat plasma in 96 well plate, a baseline resolution of arotinolol enantiomers was achieved on a CHIRALPAK AD-H column using the mobile phase of n-hexane and ethanol in 0.02% diethylamine (20:80, v/v) at a flow rate of 0.550 mL/min within 11.0 min. Acquisition of mass spectrometric data was performed on a triple-quadrupole mass spectrometer in multiple-reaction-monitoring (MRM) mode with an ESI source using the transition m/z 372.1 -> 316.1 for (+/-)-arotinolol and m/z 376.1 -> 165.1 for haloperidol. The calibration curves of both enantiomers were linear over the range of 1.00-200.0 ng/mL (r(2) > 0.992) and the lower limit of quantification was 1.00 ng/mL. Intra- and inter-day precision ranged from 5.6% to 8.9% for R-( -)-arotinolol and 4.6-7.4% for S-(+)-arotinolol. Accuracy varied from 0.0% to 7.0% for R-(-)-arotinolol and 5.0-10.0% for S-(+)-arotinolol. For R-(-)-arotinolol, the recovery ranged from 87.2% to 99.2% and the matrix factor was 1.03-1.09; for S-(+)-arotinolol, the recovery ranged from 88.0% to 92.4% and the matrix factor was 0.84-0.95, both were not concentration dependent. The method was demonstrated with acceptable accuracy, precision and specificity for the determination of arotinolol enantiomers and has been successfully applied to a stereoselective pharmacokinetic study. (C) 2014 Elsevier B.V. All rights reserved.