Rapid and simple chiral analysis of ketamine and norketamine in hair by capillary zone electrophoresis

Aims: Ketamine is a dissociative anaesthetic traditionally available as a racemic mixture, although, recently, the drug is also being released in the form of the single S-enantiomer. Starting from the ‘80s, ketamine has widely spread as drug of abuse in many countries, including Italy. Because of its mixed stimulant and dissociative effects, ketamine abuse looks particularly dangerous for traffic and workplacesafety, taking also into consideration that its detection is impossible with the traditional toxicological screening tests. The aim of the work was to develop a rapid and simple method based on capillary zone electrophoresis (CZE) for the enantioselective separation of ketamine and its major metabolite norketamine in hair specimens. Methods: After hair (100 mg) was incubated overnight in 0.1 M HCl and liquid-liquid extraction, ketamine and norketamine were analyzed by CZE in the presence of a chiral selector. The running buffer composition was 15 mM Tris phosphate (pH 2.5) added with a 0.1% highly sulphated gamma cyclodextrins, as the chiral selector. The separation was carried out under normal polarity (20 kV) in a 0.05 mm I.D. x 450 mm length uncoated fused silica capillary. Electrokinetic injection was performed at 7 kV x 50 s. The detection was based on UV absorbance at 200 nm. Results: Under the described analytical conditions, complete separation (R>1.5) of both ketamine and norketamine enantiomers was obtained in less than 10 min. The analytical sensitivity, without adopting voltage boosted injection methods, was limited to the low micrograms per milliliter range. However using field amplified sample stacking injection with a plug of 15 mM Tris phosphate (pH 2.5), the sensitivity was improved by a factor of 1,000 for both analytes without sacrificing the chiral selectivity. The method was successfully applied on hair samples from ketamine abusers. Analytical validation is in progress.