Abstract: In the present study, the metabolic profile of sulfamethazine in vivo, a veterinary drug, was investigated using ultra-performance liquid chromatography coupled to high resolution quadrupole time-of-flight mass spectrometry to acquire structural information on sulfamethazine metabolites. The corresponding product ion spectra were acquired and interpreted, and structures were proposed. Accurate mass measurement using ESI-Q-TOF/MS was using to determine the elemental composition of metabolites, thereby confirming the proposed structures of these metabolites. This study demonstrated that acetylating metabolic reaction was predominantly observed in mice plasma and urine, including target metabolite N4-Acetylsulfamethazine, subcardinal metabolites come from methylating renction and conjugates reaction.

Key words: veterinary drug, sulfamethazine, UPLC-Q-TOF/MS, metabolite