Simultaneous LC-MS/MS determination of the emerging ketamine analogue 2F-2-oxo-PCPr and related compounds in human hair and application to forensic casework.

Abstract

In early 2025, an unidentified white powder suspected illicit drug was submitted to National Forensic Service (NFS) for analysis and was subsequently identified as 2F-2-oxo-PCPr. 2F-2-oxo-PCPr is a structurally modified ketamine analogue characterized by the replacement of the aromatic chlorine substituent with fluorine and the substitution of the amine methyl group with a propyl group. Ketamine is known to exert hallucinogenic and dissociative effects through antagonism of N-methyl-D-aspartate (NMDA) receptors, and 2F-2-oxo-PCPr may exhibit similar pharmacological effects owing to its structural similarity to ketamine. In recent years, novel ketamine analogues including 2F-2-oxo-PCE have emerged on the illicit drug market, raising forensic and toxicological concerns due to their structural similarity to ketamine and the limited analytical data. In South Korea, the detection of 2F-2-oxo-PCE since 2023 and the subsequent emergence of 2F-2-oxo-PCPr since 2025 have highlighted the necessity for developing reliable analytical methods to confirm the abuse of these substances in biological specimens. Hair analysis is a powerful tool in forensic toxicology, providing a long detection window and the ability to assess chronic drug exposure. Therefore, we developed and validated a quantitative LC-MS/MS method for simultaneous detection of 2F-2-oxo-PCPr, 2F-2-oxo-PCE, 2F-deschloroketamine, ketamine and their key metabolites, 2F-deschloronorketamine and norketamine, in human hair. Selectivity, specificity, limit of detection (LOD), limit of quantification (LOQ), linearity, precision, accuracy, matrix effect, recovery, process efficiency, and stability were evaluated, and all results were acceptable. The validated method was applied to human hair samples from 8 individuals suspected of ketamine related substances use provided by the law enforcement agency. To the best of our knowledge, this is the first study to report a single validated hair-based LC-MS/MS workflow that simultaneously covers ketamine together with both fluorinated ketamine analogues (2F-2-oxo-PCPr, 2F-2-oxo-PCE and 2F-deschloroketamine) and their metabolites.