DETERMINATION OF (R)-(-ISOMERS AND (S)-(-)-ISOMERS OF THIOPENTONE IN PLASMA BY CHIRAL HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY())

A method for the determination of (R)-(+)- and (S)-(-)-isomers of thio pentone in plasma was developed. Following liquid-liquid extraction, t he separation of enantiomers of thiopentone and the internal standard (racemic ketamine) was achieved by high-performance liquid chromatogra phy on an alpha(1)-acid glycoprotein (AGP) column with ultraviolet det ection 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/m in. The limit of quantification for each isomer was approximately 10 n g/ml. The assay is suitable for pharmacokinetic studies of (R)-(+)- an d (S)-(-)-isomers of thiopentone, following usual bolus intravenous cl inical doses of the racemic drug.