High-performance liquid chromatographic analysis of ondansetron enantiomers in human serum using a reversed-phase...

A stereospecific HPLC method was developed for the assay of R-(-)- and S-(+)-ondansetron enantiomers in human serum. The method involves the use of solid-phase extraction for sample clean-up and is also free of interference from 6-hydroxyondansetron, 7-hydroxyondansetron and 8-hydroxyondansetron, the three major metabolites of ondansetron. Chromatographic resolution of the enantiomers was performed on a reversed-phase cellulose-based chiral column (Chiralcel OD-R) under isocratic conditions using a mobile phase consisting of 0.7 M sodium perchlorate-acetonitrile (65:35, v/v) at a flow-rate of 0.5 ml/min. Recoveries at 200 ng/ml levels were more than 90% for both ondansetron enantiomers. Intra-day and inter-day precisions calculated as R.S.D.s were in the 0.3-5% and 2-8% ranges for both enantiomers, respectively. Intra-day and inter-day accuracies calculated as percent error were in the 0.3-11.5% and 0-3% ranges for both enantiomers, respectively. Linear calibration curves were obtained for each enantiomer in serum in the concentration range 15-750 ng/ml. The limit of quantitation of each enantiomer was 15 ng/ml. The detection limit for each enantiomer in serum using UV detection at 210 nm was 7 ng/ml (S/N=2).