Determination of dextromethorphan and dextrorphan solar photo-transformation products by LC/Q-TOF-MS: Laboratory scale experiments and real water samples analysis

• Published in: Environmental pollution (1987) Vol. 265; no. Pt A; p. 114722
• Main Authors: Campos-Mañas, Marina Celia, Cuevas, Sara Miralles, Ferrer, Imma, Thurman, Earl Michael, Sánchez-Pérez, José Antonio, Agüera, Ana
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-10-2020
• Subjects: Opioids; Photolysis; Surface water; Transformation products; Wastewater; Transformation products; Photolysis; Wastewater; Opioids; Surface water
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2020.114722

This work discusses the identification of the transformation products (TPs) generated during the photolytic degradation of dextromethorphan (DXM) and its metabolite dextrorphan (DXO), under simulated solar radiation in aqueous solutions (Milli-Q water and river water) in order to determinate its behavior into the aquatic environment. Tentative identification of the TPs was performed by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOF-MS), following a suspect screening approach. The use of high resolution-mass spectrometry (HRMS) allowed the tentative identification of DXM and DXO photoproducts based on the structure proposed by an in silico software, the accurate mass measurement, the MS/MS fragmentation pattern and the molecular formula finding. A total of 19 TPs were found to match some of the accurate masses included in a suspect list, and they were all tentatively identified by their characteristic MS-MS fragments. Most of the TPs identified showed a minor modified molecular structure like the introduction of hydroxyl groups, or demethylation. The time-evolution of precursors and TPs were monitored throughout the experiments, and degradation kinetics were presented for each analyte. Finally, the occurrence of DXM, DXO, and their tentatively proposed photodegradation TPs was evaluated in both surface and wastewater. In all real matrices, the results showed that the highest concentration was detected for DXO, followed by TP-244 (N-desmethyldextrorphan) and DXM.
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•Photolysis of dextromethorphan and dextrorphan was studied.•Photodegradation kinetics were calculated.•LC/QTOF-MS/MS analysis was conducted to tentatively identify 19 phototransformation products.•Real environmental water samples were evaluated by retrospective analysis.•Dextromethorphan, dextrorphan, and N-demethyldextrorphan were identified in real samples.
A photolysis study of DXM and DXO demonstrated the formation of 19 TPs and their presence and fate in environmental waters has been evaluated.