Simultaneous detection of residues of 34 beta-lactam antibiotics in livestock and fish samples through liquid chromatography-tandem mass spectrometry

β -Lactam is one of the widely used veterinary drugs, but simultaneous analytical methods for β -lactam on various animal foods have not been established. In this study, we aimed to detect 34 β -lactam antibiotics simultaneously in livestock samples (beef, pork, chicken, egg, and milk) by liquid chromatography-tandem mass spectrometry (LC–MS/MS). Samples were extracted using phosphate buffer/acetonitrile or water/acetonitrile and then cleaned with 150 mg of C 18 and 900 mg of MgSO 4 . The method showed acceptable recovery and repeatability of 66.1–119% and 1.5–26%, respectively. The method was employed to monitor 127 real samples from the domestic market to confirm its applicability, and no β -lactam residues were detected. It was also applied to other matrices (eel, flat fish, and shrimp) and showed acceptable recovery (62.1–120%) and repeatability (1.0–28%). The method is expected to improve the efficiency of monitoring veterinary drug residues in domestic livestock products and fishery foods.