Mass Spectrometry-Based Characterization of Electrolytic Decomposition Products of Carbamazepine and Aripiprazole Under Different Electrode Conditions

Background: Carbamazepine (CBZ) and aripiprazole (ARI), frequently detected in medical facility effluents, are resistant to conventional wastewater treatment. However, a systematic comparison of their electrolytic degradation product profiles under different electrode conditions using an identical operating platform has not been previously reported. Methods: CBZ and ARI in NaCl solutions were subjected to electrolytic oxidation using the Eleca® system with either a boron-doped diamond (BDD) or a metal electrode. Residual drugs were quantified by LC-MS/MS and pseudo-first-order degradation kinetics were calculated. Transformation products were characterized by LC/PDA/HRMS/MS based on accurate mass measurements, MS/MS fragmentation, chromatographic behavior, and UV absorption. Radical scavenger experiments using methanol and tert-butanol were conducted to investigate reactive species’ contributions to degradation. Results: Both drugs were rapidly degraded under all conditions, with the metal electrode consistently exhibiting higher apparent pseudo-first-order rate constants than the BDD electrode. The metal electrode generated hydrophobic intermediates apparently retaining aromatic skeletons (consistent with partial oxidation), whereas the BDD electrode yielded more polar, low-molecular-weight products consistent with more extensive skeletal fragmentation (deep oxidation). Scavenger experiments suggested a greater relative contribution of hydroxyl radicals (•OH) under BDD electrode conditions. Transformation products were transiently detected but eliminated by prolonged electrolysis. Conclusions: Electrode material critically determines the degradation pathway, reactive species distribution, and product profile. Structural analysis of the tentatively identified transformation products suggests loss of pharmacophore integrity in several intermediates; however, residual pharmacological risk has not been experimentally validated and requires biological sassays for confirmation. Furthermore, the observed disappearance of the parent compounds does not demonstrate complete mineralization, detoxification, or environmental safety, as total organic carbon measurements and ecotoxicological assays were not performed. This study provides the first comparative characterization of transformation products of recalcitrant psychotropic drugs under metal vs. BDD electrode electrolysis, offering mechanistic insights for pharmaceutical wastewater treatment optimization.