In this study, BS1801 metabolites were characterized in the hepatocytes of different species (monkey, dog, mouse, rat, and human) and plasma specimens using the ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC/Q-TOF MS) method. 
UPLC/Q-TOF MS
Five metabolites were identified based on the characteristic peak clusters of selenium atoms in the mass spectrum, combined with the product ions obtained by MS-MS through collision-induced-dissociation (CID), including M1 (reduction metabolite), M2 (reduction and Se-methylation metabolite), M4 (M2 further oxidized metabolite) and M5 (Se-methylation and Se-glucuronidation conjugation metabolite), of which the amount of M2 was the highest. 
MS-MS through collision-induced-dissociation (CID)
Subsequently, an accurate and fast LC-MS/MS method was established to verify the major metabolite M2 in human plasma. 
LC-MS/MS method