China Resources Sanjiu Modern Chinese Medicine Pharmaceutical Co., Ltd 1 article published in JoVE Chemistry An Improved Technique for Trimethylamine Detection in Animal-Derived Medicine by Headspace Gas Chromatography-Tandem Quadrupole Mass Spectrometry Hui Ye1, Xuemei Liu1, JiaBao Liao2, Haozhou Huang3, Lin Huang1, Yang Bao1, Hongyan Ma1, Junzhi Lin4, Xiaoming Bao5, Dingkun Zhang1, Runchun Xu1 1State Key Laboratory of Southwestern Chinese Medicine Resources, Pharmacy School, Chengdu University of Traditional Chinese Medicine, 2China Resources Sanjiu Modern Chinese Medicine Pharmaceutical Co., Ltd, 3Innovative Institute of Chinese Medicine and Pharmacy, Chengdu University of Traditional Chinese Medicine, 4TCM Regulating Metabolic Diseases Key Laboratory of Sichuan Province, Hospital of Chengdu University of Traditional Chinese Medicine, 5Shimadzu (China) Co., Ltd Here, a headspace gas chromatography-tandem quadrupole mass spectrometry (HS-GC-MS/MS) method suitable for the determination of trimethylamine (TMA) in animal-derived medicines is described. The protocol includes sample pretreatment, headspace treatment, analysis conditions, methodological validation, and the determination of TMA in animal-derived medicines.