[Determination of doxepin in whole blood by SPE-LC-MS/MS].

To develop a method of SPE-LC-MS/MS for the determination of doxepin in whole blood. 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. The calibration curve was linear among the concentration of doxepin range from 0.005 to 1.00 microg/mL. The linear correlation equation was y = 3.2047x + 0.0339, the correlation coefficient was 0.9996. The detection limit of doxepin was 0.001 microg/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. The method is effective, simple, reliable and can be used in the determination of doxepin in whole blood.