Identification of phase II pharmaceutical metabolites in reclaimed water using high resolution benchtop Orbitrap mass spectrometry.

This study described an analytical method for the identification of common phase II pharmaceutical metabolites in reclaimed water using liquid chromatography high resolution Orbitrap mass spectrometry after solid phase extraction (SPE). Orbitrap mass spectrometer was operated at resolution of 70000 in MS mode and 35000 in data-dependent MS/MS mode, without using lock mass. Firstly, parent drugs and their metabolites were tentatively identified based on accurate mass using a mass tolerance of 5 ppm. A detailed examination of the extracted ion chromatograms (XICs) for all potential metabolites revealed the presence of two phase II metabolites of sulfamethoxazole, acetylsulfamethoxazole and sulfamethoxazole glucuronide in reclaimed water. Secondly, the high resolution data-dependent MS/MS spectra of each compound were further investigated using metabolic profiling software. After comparing characteristic ions obtained in MS/MS mode with those predicted by the software and reported in previous studies, the two phase II metabolites were positively identified in reclaimed water. Lastly, the two metabolites were detected and quantified in the reclaimed water samples collected during a period of one month. As a result, averaged concentrations of sulfamethoxazole, acetylsulfamethoxazole and sulfamethoxazole glucuronide were calculated at 2848 ± 1367 ng L(-)(1), 1980 ± 1410 ng L(-)(1), and 2859 ± 1526 ng L(-)(1), respectively. The two metabolites represented 54% of the source of sulfamethoxazole in reclaimed water suggesting the importance of measuring pharmaceutical metabolites in the environment. To our knowledge, this is the first known report of sulfamethoxazole glucuronide surviving intact through wastewater treatment plants and occurring in environmental water samples.