Abstract: Objective To develop a method of SPE-LC-MS/MS for the determination of doxepin in whole blood. Methods After solid phase extraction, the samples were identified by LC-MS/MS. Positive ion electrospray ionization mode and multiple reaction monitoring（MRM） mode was selected. Amitriptyline was used as internal standard. The m/z of doxepin： 280→107, 280→235 and 280→220. The m/z of amitriptyline： 278→233. The retaining time of doxepin and amitriptyline were 15.15 and 16.94 min, respectively. Results The calibration curve was linear among the concentration of doxepin range from 0.005 to 1.00 μg/mL. The linear correlation equation was y=3.204 7 x+0.033 9, the correlation coefficient was 0.999 6. The detection limit of doxepin was 0.001 μg/mL and average recovery rate was 78.0%-82.9%. The relative standard precision for within-day and between-day were less than 2.55% and 5.90%, respectively. Conclusion The method is effective, simple, reliable and can be used in the determination of doxepin in whole blood.

Key words: forensic toxicology, solid phase extraction, LC-MS/MS, doxepin, blood