Mariane Olivier Brandão, Luciano C. Arantes, Camila D. Lima, Bruno Gabriel Lucca, Natália C. Moraes, Evandro Rodrigo Pedão, Fernanda M.R. Guerbas, Sâmya Soler Gebara, Wallans T. P. dos Santos
ABSTRACT Simultaneous detection of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) is crucial for the analysis of seized materials and cannabis-based preparations. To address this need, a simple, rapid, and selective electrochemical method was developed for the preliminary detection and quantification of both cannabinoids. The proposed method employs unmodified carbon screen-printed electrodes (carbon-SPEs) in a strongly alkaline medium (0.5 mol L -1 NaOH solution). The electrochemical behaviors of THC and CBD were investigated over a wide range of pH values, enabling a simultaneous detection with distinct peak potentials observed on carbon-SPE ( vs Ag). THC exhibited a single irreversible oxidation process (O 1T ) on the carbon-SPE surface, whereas CBD showed, for the first time, five well-defined electrochemical processes, with two reduction processes (R 1C and R 2C ) and three oxidation processes (O 1C, O 2C and O 3C ). Square wave voltammetric technique was optimized for the simultaneous determination of THC and CBD using their oxidation processes at O 1T and O 3C on carbon-SPE, with limits of detection of 0.09 μmol L -1 and 2.72 μmol L -1 , respectively. Moreover, consistent electrochemical responses were obtained using either the same (N=5) or different SPEs (N=3), with RSDs lower than 5.6% and 2.0 % for peak currents and peak potentials, respectively. Method applicability was confirmed by analyzing thirty-five (35) real seized samples and seven cannabis-based products, showing good agreement with GC-MS results. Addition-recovery studies using real seized samples yielded values close to 100 % for both analytes: 102 ± 2 % for O 1T (THC) and 103.3 ± 0.8 % for O 3C (CBD). These findings highlight the method’s potential as a reliable, low-cost, and field-deployable tool for forensic screening and quality control in cannabis-derived products.