Quantification of paroxetine in human plasma by liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

A rapid LC coupled with electrospray ionization (ESI) MS/MS method was developed and validated for the quantification of paroxetine in heparinized human plasma. The plasma samples were prepared by the solid-phase extraction method without drying or reconstitution. Elution was done with 0.5 mL 0.2% (v/v) formic acid in methanol-acetonitrile (65 + 35, v/v). The analyte and the internal standard (IS; imipramine hydrochloride) were chromatographed on a BDS Hypersil C18 column. The analyte was analyzed by LC/MS/MS with only 1.7 min run time. An ESI interface was chosen for ionization of the analyte from the sample matrix. Selected reaction monitoring mode for detection of paroxetine and the IS were achieved by using m/z 330.17/192.10 and 281.13/86.14, respectively. The LC retention times for paroxetine and imipramine were 0.94 and 1.05 min, respectively. The method was linear in the concentration range of 0.5-80.0 ng/mL with r > or = 0.9995. Recovery of paroxetine and imipramine ranged from 90 to 95%. The assay has been successfully applied to bioequivalence study samples for estimation of paroxetine in healthy human subjects.