Simultaneous determination of carbamazepine-N-glucuronide and carbamazepine phase I metabolites in the wastewater by liquid chromatography-tandem mass spectrometry

Carbamazepine (CBZ) is one of the most frequently detected pharmaceuticals in the aquatic environment. In the human body, CBZ is metabolized and transformed into a variety of metabolites. Among metabolites, CBZ N-glucuronide (CBZ-Glu, Phase II metabolite) was discharged into sewage system together with Phase I metabolites such as 2-hydroxycarbamazepine (2-OH-CBZ), 3-hydroxycarbamazepine (3-OH-CBZ), 10-hydroxycarbamazepine (10-OH-CBZ), 10,11-Dihydroxycarbamazepine (DiOH-CBZ), and carbamazepine 10,11-ep-oxide (EP-CBZ). However, the occurrence of CBZ-Glu in wastewater was not reported previously due to the lack of CBZ-Glu standard. In this study, a quantitative analytical method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the determination of CBZ-Glu as well as other CBZ metabolites in wastewater. In the developed method, sufficiently high extraction efficiencies of CBZ and its metabolites were achieved by solid phase extraction (SPE) process (recoveries ranged from 79.3% to 95.8%, and from 84.4% to 96.4% in wastewater influent and effluent, respectively). The concentration of CBZ-Glu in the wastewater influent and effluent were 59.4, and 48.1 ng/L, respectively. CBZ in the wastewater influent and effluent were 53.8, and 61.9 ng/L, respectively. Although CBZ and phase I metabolites were persistent during the A2O process, deconjugation of CBZ-Glu was suspected to contribute to the increase of CBZ.