Simultaneous stereoselective analysis of venlafaxine and O-desmethylvenlafaxine enantiomers in human plasma by HPLC-ESI/MS using a vancomycin chiral column.

A high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI/MS) method for simultaneous stereoselective analysis of venlafaxine (VEN) and its major metabolite O-desmethylvenlafaxine (ODV) enantiomers in human plasma has been developed and validated. Chiral chromatography is performed on the CHRIOBIOTIC V (5 microm, 250 mm x 4.6 mm) column with mobile phase constituted of 30 mmol/l ammonium acetate-methanol (15:85, pH 6.0) at a flow rate of 1.0 ml/min and a postcolumn splitting ratio of 3:1. The compounds were ionized in the electrospray ionization (ESI) ion source of the mass spectrometer and detected using the selected ion recording (SIR) mode. Calibration curves obtained from spiked plasma were linear in the range of 5.0-400 ng/ml for S-(+)-VEN and R-(-)-VEN, 4.0-280 ng/ml for S-(+)-ODV and R-(-)-ODV, respectively, with linear correlation coefficient all above 0.999. The average extraction recoveries for all the four analytes were above 76%. The methodology recoveries were higher than 92%. The limit of detection were 1.0 ng/ml for S-(+)-VEN and R-(-)-VEN, 1.5 ng/ml for S-(+)-ODV and R-(-)-ODV, respectively. The intra- and inter-day variation coefficients were less than 9%.