Determination of tropisetron in human plasma by liquid chromatography-tandem mass spectrometry.

A sensitive and selective liquid chromatography-tandem mass spectrometry method (LC-MS/MS) for the determination of tropisetron in human plasma was developed and validated over the concentration range of 0.100-100 ng/mL. Diphenhydramine was used as the internal standard (IS). The tropisetron and the IS were extracted from alkalized plasma samples into diethyl ether-dichloromethane (2:1, v/v) and the LC separation was performed by a Diamonsil C18 column (150 mm x 4.6 mm, i.d., 5 microm). The mobile phase was methanol:water (80:20, v/v) containing 0.2% formic acid delivered at a flow rate of 0.5 mL/min. The total chromatographic run time was 4.5 min. The MS data acquisition was accomplished by selected reaction monitoring (SRM) mode with positive atmospheric pressure chemical ionization (APCI) interface. The lower limit of quantification (LLOQ) achieved was 0.100 ng/mL with precision (RSD) of 3.1% and accuracy (RE) of -0.7%. For both inter-batch and intra-batch tests, the precision (RSD) for the entire validation was less than 6.0%, and the accuracy (RE) was within the -0.5% to 0.2% range. This validated LC-MS/MS method was later used to characterize the pharmacokinetics as well as the bioequivalence of tropisetron formulations.