High performance liquid chromatography-electrospray ionization mass spectrometric determination of tolterodine tartrate in human plasma

A selective and sensitive high performance liquid chromatography-electrospray ionization mass spectrometry method has been developed for the determination of tolterodine tartrate in human plasma. With oxybutynin as internal standard, tolterodine tartrate was extracted from plasma with n-hexane: isopropanol (95:5, v/v). The organic layer was evaporated and the residue was redissolved in mobile phase comprised of acetonitrile–water (10 mM CH3COONH4, pH 3.0) = 50:50 (v/v). An aliquot of 10 μl was chromatographically analyzed on a prepacked Shimadzu Shim-pack VP-ODS C18 column (150 mm × 2.0 mm I.D.) by means of selected-ion monitoring (SIM) mode mass spectrometry. Standard curves were linear (r = 0.9993) over the concentration range of 0.1–30.0 ng/ml and had good accuracy and precision. The within- and between-batch precisions were within 10% relative standard deviation. The limit of detection (LOD) was 0.05 ng/ml. The validated LC–ESI–MS method has been used successfully to study tolterodine tartrate pharmacokinetic, bioavailability and bioequivalence in 20 healthy male volunteers.