Chiral separation and determination of ketamine and norketamine in hair by capillary electrophoresis

Ketamine, traditionally available as racemic mixture, has recently become available in the form of the single S-enantiomer, due to its higher anaesthetic potency associated with faster recovery times. The different pharmaceutical forms and the different pharmacodynamics of the two enantiomers imply the need for a chiral method, since most available analytical methods for biological matrices are not enantioselective. The method herein showed consists of simple capillary zone electrophoresis (CZE) for the chiral separation of ketamine and its major metabolite, norketamine, in hair specimens. After liquid-liquid extraction, the samples were electrokinetically injected and analysed in CE (running buffer: 15mM Tris phosphate pH 2.5, containing HS-γ-CDs, 0.1%, w/v). A complete separation of both racemic ketamine and norketamine in the respective enantiomers was obtained in less than 10minutes. Limit of detection (LOD) and limit of quantification (LOQ) were 0.08ng/mg and 0.25ng/mg, respectively. Percent recovery varied from 49% to 91% for all four enantiomers. Matrix effect on spiked hair samples demonstrated values ranging from 63% to 119%. Linearity was estimated using a calibration curve consisting of five concentration levels for each enantiomer (0.5-8.0ng/mg); the regression coefficients (R(2)) of weighted (1/x(2)) linear regression were all >0.988. The method is suitable for the analysis of real-world hair samples in order to investigate ketamine chronic abuse and to discriminate between the type of abused drug, either single enantiomer or racemic drug.