Liquid chromatography/mass spectrometry analytical determination of gabapentin transformation products by heterogeneous photocatalysis and environmental evaluation

Rationale Gabapentin is a drug used to treat epilepsy and peripheral neuropathic pain. It is an analog of gamma‐aminobutyric acid, and it is a selective blocker of voltage‐gated calcium channels. The drug is excreted unmetabolized; it is stable in the environment and is classified as a persistent mobile organic contaminant. Because wastewater treatment plants (WWTPs) are not completely efficient, some bioactive molecules may be released unaltered into the environment. The aim of this study was to provide information about degradation pathways of gabapentin in water by studying its photoinduced transformation products (TPs) through laboratory simulation experiments. Gabapentin and its TPs were monitored in influent and effluent water samples from WWTPs in Germany and Italy. Methods The laboratory simulation used heterogeneous photodegradation mediated by titanium dioxide (TiO2). Chromatographic separation was achieved using a C18 reverse‐phase column, and the structural identification of TPs was performed using high‐resolution electrospray ionization high‐resolution mass spectrometry (ESI‐HRMS) and multistage MSn experiments. Results Several TPs were observed during TiO2 photodegradation. Nine new compounds were detected, and potential structures were assigned by studying the fragmentation pathways of the [M + H]+ ions of these TPs and gabapentin. Gabapentin and some of the newly identified TPs were found in environmental samples from WWTPs. Conclusions The developed high‐performance liquid chromatography/high‐resolution mass spectrometry method was used to identify TPs from gabapentin. It was then successfully applied to real environmental samples to monitor the TPs as potential environmental pollutants.