Simultaneous determination of desloratadine and pseudoephedrine in human plasma using micro solid-phase extraction tips and aqueous normal-phase liquid chromatography/tandem mass spectrometry

Cation‐exchange micro solid‐phase extraction (SPE) tips and aqueous normal‐phase (ANP) chromatography coupled with tandem mass spectrometry were explored for the rapid, selective and sensitive quantitation of desloratadine and pseudoephedrine in human plasma. A novel micro‐SPE device was evaluated for analyte capacity, extraction efficiency and its ability to maximize recovery of an analyte of interest from bioanalytical matrices by successive replicates of linked extraction steps. Ion suppression using two different methods with micro‐SPE tips was negligible when compared to protein precipitation. The use of ANP chromatography eliminated the need for sample reconstitution following extraction and was found to be highly selective. A reliable chromatography system was developed with a short duty cycle of 2 min/sample. The proposed bioanalytical method required 50 µL of plasma for the determination of desloratadine and pseudoephedrine at limits of quantitation of 0.1 and 1.25 ng/mL, respectively. The analytical method was validated in accordance with the FDA guidance on bioanalytical method validation; selectivity, linearity, reproducibility and accuracy were all acceptable. Copyright © 2007 John Wiley & Sons, Ltd.