Liquid chromatography-tandem mass spectrometry (LC-MS/MS) determination of cantharidin in biological specimens and application to postmortem interval estimation in cantharidin poisoning

A rapid, sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination and quantification of cantharidin in rats liver and kidney. After grinding with methanol, the supernatant was determined by LC-MS/MS using an Thermo Accucore C18 column (100mmx2.1mm, 2.6 mu m) with a gradient elution of 0.1% formic acid and 0.1% acetonitrile, and in the subsequent analysis using selected reaction monitoring mode, three ion transitions were monitored for analyte. The limit of detection (LOD) was 0.741ng/ml and the limit of quantitation (LOQ) was 2.471ng/ml. Good linearity (R-2=0.9998) was observed for the analyte over the linear range (5-400ng/ml). The LC-MS/MS method was applied to the analysis of rats liver and kidney in different postmortem intervals (6h, 12h, 24h, 48h, 72h and 168h after death) after a single dose (4mg/kg) of cantharidin administration by gavage. At 72h after death, the cantharidin concentration in livers and kidneys were significantly higher than that in other postmortem intervals. Linear regression equations between postmortem interval and lg postmortem cantharidin concentration in rats liver and kidney were Y=0.007455*X+1.332(R-2=0.863) and Y=0.002689*X+1.433 (R-2=0.115) respectively. The animal experiment demonstrated LC-MS/MS method can be used to determine the postmortem cantharidin concentration in rats liver and kidney and the determination of cantharidin in the rats liver after death has potential value for postmortem interval estimation in cantharidin poisoning.