Abstract: Objective To develop a sensitive and accurate assay for detecting cinobufagin and resibufogenin in liver tissue using high performance liquid chromatography-tandem mass spectrometry （HPLC-MS/MS）. Methods The homogenization of liver tissue with internal standard dexamethasone was extracted with dichloromethane. The extracts with methanol were purified through ProElut C18 solid phase extraction and tested in positive electrospray ionization with multiple reaction monitoring of HPLC-MS/MS. Results The good linear relationship of cinobufagin and resibufogenin in liver tissue were 1-204 ng/g and 1-206 ng/g, respectively. The minimal detection threshold （S/N≥3） of this method was 0.3 ng/g for both cinobufagin and resibufogenin. The matrix effect was 96.5%-126.7%. The extraction recovery coefficient was 70.0%-82.3%. The precision of intra-day and inter-day was less than 10%. Conclusion This method is sensitive and reliable, and can be used in forensic toxicological analysis.

Key words: forensic toxicology, tandem mass spectrometry, high performance liquid chromatography-tandem mass spectrometry, cinobufagin, resibufogenin