Abstract: Objective To develop a liquid chromatography-tandem mass spectrometry （LC-MS/MS） analytical method for the determination of oleandrin in blood and liver tissues, which could be applied to the cases of death caused by oleander poisoning. Methods Blood or liver tissues underwent a liquid-liquid extraction （LLE） using ethyl acetate, and the extract was separated on an Agilent ZORBAX SB-C18 column and eluted with a gradient of acetonitrile and 20 mmol/L ammonium acetate （containing 0.1% formic acid）. Oleandrin was detected using electrospray positive ionization （ESI+） with multiple-reaction monitoring （MRM） mode. Results Oleandrin showed excellent linearity in both blood and liver samples in the corresponding linear range （r>0.995 0）, with detection limits 1 ng/mL and 2 ng/g, respectively, extraction recovery rates greater than 70.50%, both intra- and inter-day precisions less than 10.71%, accuracies 98.42%-111.63%, and matrix effects 91.52%-106.39%. The method was successfully applied to a case of suspected oleander poisoning. Oleandrin was detected in the blood, urine, liver tissues, bile, stomach wall tissues and stomach contents of the cadaver, with the content ranging from 65.5 to 29 600.0 ng/mL （ng/g）. Conclusion The method developed in this study is simple and convenient to operate with good selectivity, and is suitable for the analysis of oleandrin in biological samples such as blood and liver tissues, which can provide technical support for forensic identification and clinical diagnosis and treatment of oleander poisoning.

Key words: forensic toxicology, poisoning, blood, liver, liquid chromatography-tandem mass spectrometry, oleandrin