Quantitation of promethazine enantiomers in human serum using a chiralcel OJ-R column and mixed-mode disc solid-phase...

A liquid chromatographic method was developed for the assay of R(+)- and S(-)-promethazine enantiomers from human serum. The method involves the use of the mixed mode disc solid-phase extraction technique for sample clean-up. Chromatographic resolution of the enantiomers was performed on a reversed-phase cellulose-based chiral column (Chiralcel OJ-R) under isocratic conditions using a mobile phase consisting of 0.5 M aqueous sodium perchlorate/acetonitrile (63:37, v/v) at a flow rate of 0.5 ml min-1. Recoveries in the range of 97-99% at 20 ng ml-1 levels were obtained for both promethazine enantiomers. Intra-day and inter-day precision calculated as R.S.D.% was in the 3-8% ranges for both enantiomers. Intra-day and inter-day accuracy calculated as percent error was in the 0-10 and 1-7% ranges for both enantiomers, respectively. Linear calibration curves were obtained for each enantiomer in serum in the concentration range 5-90 ng ml-1. The limit of quantitation of each enantiomer was 10 ng ml-1. The detection limit for each enantiomer in serum using UV detection at 249 nm was 2 ng ml-1 (S/N = 2).