Determination of (R)-(+)- and (S)-(-)-isomers of thiopentone in plasma by chiral high-performance liquid chromatography.

A method for the determination of R-(+)- and (S)-(-)-isomers of thiopentone in plasma was developed. Following liquid-liquid extraction, the separation of enantiomers of thiopentone and the internal standard (racemic ketamine) was achieved by high-performance liquid chromatography on an alpha1-acid glycoprotein (AGP) column with ultraviolet detection at 280 nm. The mobile phase consisted of 20 mM KH2PO4 buffer-2-propanol-methanol (93.5:5.0:1.5) at pH 5.0. The flow-rate was 0.9 ml/min. The limit of quantification for each isomer was approximately 10 ng/ml. The assay is suitable for pharmacokinetic studies of (R)-(+)- and (S)-(-)-isomers of thiopentone, following usual bolus intravenous clinical doses of the racemic drug.