Quantification of rabeprazole in human plasma by liquid chromatography–tandem mass spectrometry

An analytical method based on liquid chromatography coupled with tandem mass spectrometry detection has been developed and validated for the determination of rabeprazole in human plasma using omeprazole as the internal standard. The analyte and internal standard was extracted with n-hexane–dichloromethane–isopropanol (20:10:1, v/v) and chromatographed isocratically on a Diamonsil C18 analytical column. Methanol was used as the mobile phase to avoid decomposition of rabeprazole. The drug was detected in the selected reaction monitoring mode using an atmospheric pressure chemical ionization source. The method was linear within the range 2.0-800 ng/ml. The lower limit of quantification was 2.0 ng/ml. The intra- and inter-day precision, calculated from quality control (QC) samples, was less than 9.8%. The accuracy was within (plus-minus)1.1%. The method herein described was employed in a pharmacokinetic study after an oral administration of 20 mg rabeprazole to 18 healthy volunteers.