New psychoactive drugs: A comprehensive electrochemical characterization and differential pulse voltammetric analysis of xylazine.

Xylazine is a widely employed veterinary anesthetic that, in recent years, has also been used as a recreational drug, leading to several fatal and non-fatal intoxications. We present herein a comprehensive investigation of the electrochemical behavior of xylazine, followed by the quantification of this target analyte. Specifically, it has been found that xylazine oxidizes irreversibly on a glassy carbon electrode in ethanol/lithium perchlorate media, with an EC mechanism; the number of electrons involved in the process is equal to two. The oxidation pathway has been suggested and supported by a thorough electrochemical investigation, in which the behavior of the analyte has been compared with other model compounds. A quantitative method was then proposed, employing differential pulse voltammetry (DPV) for the determination of xylazine in real samples. The analytical figures of merits were computed from the calibration curves obtained by analyzing standard solutions of xylazine in ethanol/lithium perchlorate medium. A LOQ of 0.2 μg mL-1 and a dynamic range up to 150 μg mL-1 were achieved. The method was then applied to samples simulating "street tablets" and urine from drug consumers. The selectivity of the method, as well as the reproducibility of the results, were investigated by analyzing the interferences between common excipients and human urine components. For urine samples, a Florisil-based clean-up and preconcentration step by solid phase extraction (SPE) were carried out. The SPE strategy was optimized by a Design of Experiments (DoE) approach, whereby an enrichment factor of up to 25 was obtained. Recoveries from 87 % to 108 % were achieved on all examined samples, suggesting the good potential of the method for its application in clinical and forensic chemistry.