Determination of ketamine and norketamine enantiomers in plasma by solid-phase extraction and high-performance liquid chromatography.

A high-performance liquid chromatographic method is described for determination of sub-anaesthetic concentrations of the enantiomers of ketamine and its metabolite norketamine in plasma. The samples are purified by reversed-phase solid-phase extraction. The enantiomers are separated on a Chiral AGP column with a mobile phase containing 16% methanol and a 10 mM phosphate buffer at pH 7.0, and measured by UV-detection at a wavelength of 220 nm. Linear calibration curves with correlation coefficients better than 0.995 have been obtained in the range 10-320 ng/ml. Minimum detectable concentrations were about 2 ng/ml.