Determination of ketamine and norketamine in hair samples by μ-QuEChERS and gas chromatography coupled to tandem mass spectrometry

Ketamine has gained popularity in Europe as a new psychoactive substance due to its dissociative effects, which are sought after by users at raves, for unprescribed treatment of psychological issues, and in drug-facilitated crimes. Forensic experts often face challenges in proving drug use, and hair offers distinct advantages as a sample, revealing both long-term consumption and recent abuse. However, due to its complex nature, hair requires pretreatment to remove interferences and enhance analytical sensitivity. This study employs a miniaturised version of the "Quick, Easy, Cheap, Rugged, and Safe" (QuEChERS) extraction method, commonly used in food and environmental analyses. The method uses 1 mL of 5 % formic acid in acetonitrile and 250 mg ammonium formate as solvent and salt partitioning agents, along with 50 mg magnesium sulphate and 10 mg primary-secondary amine for dispersive solid-phase extraction. After this cleanup process, samples were analysed using gas chromatography coupled with tandem mass spectrometry. Following optimisation, the method was validated for detecting ketamine and its primary metabolite, norketamine. A limit of detection of 0.01 ng/mg was achieved for ketamine, and 0.8 ng/mg for norketamine, with limits of quantification of 0.05 ng/mg and 0.8 ng/mg, respectively. This established a working range of 0.05-5 ng/mg for ketamine and 0.8-5 ng/mg for norketamine. Recovery rates ranged from 47-76 % for ketamine and 14-27 % for norketamine. The method was then applied to real samples from drug users, proving the effectiveness of the mu -QuEChERS technique as a sustainable clean-up method. Despite its miniaturisation, it retained the performance of the original QuEChERS protocol and allowed obtaining high sensitivity, enabling analyte detection at a concentration below the Society of Hair Testing's cut-off value of 0.2 ng/mg.