Determination of ketamine, norketamine and dehydronorketamine in urine by hollow-fiber liquid-phase microextraction using an essential oil as supported liquid membrane

Here, we present a method for the determination of ketamine (KT) and its main metabolites, norketamine (NK) and dehydronorketamine (DHNK) in urine samples by using hollow-fiber liquid-phase microextraction (HF–LPME) in the three-phase mode. The fiber pores were filled with eucalyptus essential oil and a solution of 1.0 mol/L of HCl was introduced into the lumen of the fiber (acceptor phase). The fiber was submersed in the alkalinized urine containing 10% NaCl, and the system was submitted to lateral shaking (2400 rpm) during 30 min. Acceptor phase was withdrawn from the fiber, dried and the residue was then derivatized with trifluoroacetic anhydride (TFAA) for further determination by gas chromatography–mass spectrometry (GC–MS). The calibration curves were linear over the specified range and limits of detection (LoDs) obtained for KT, NK and DHNK were below the cut-off value (1.0 ng/mL) recommended by the United Nations Office on Drugs and Crime (UNODC). A totally “green chemistry” approach of the sample extraction was obtained by using essential oil as a supported liquid membrane in HF–LPME. The developed method was successfully validated and applied to urine samples collected from two clinical cases in which KT was suspected to be involved.