High-performance liquid chromatography method for the quantification of rabeprazole in human plasma using solid-phase extraction

A simple, sensitive and selective HPLC method with UV detection (284 nm) was developed and validated for quantitation of rabeprazole in human plasma, the newest addition to the group of proton-pump inhibitors. Following solid-phase extraction using Waters Oasistrade mark SPE cartridges, the analyte and internal standard (Pantoprazole) were separated using an isocratic mobile phase of 5 mM ammonium acetate buffer (pH adjusted to 7.4 with sodium hydroxide solution)/acetonitrile/methanol (45/20/35, v/v) on reverse phase Waters symmetry C(18) column. The lower limit of quantitation was 20 ng/mL, with a relative standard deviation of less than 8%. A linear range of 20-1000 ng/mL was established. This HPLC method was validated with between- and within-batch precision of 2.4-7.2% and 2.2-7.3%, respectively. The between- and within-batch bias was -1.7 to 2.6% and -2.6 to 2.1%, respectively. Frequently coadministered drugs did not interfere with the described methodology. Stability of rabeprazole in plasma was excellent, with no evidence of degradation during sample processing (autosampler) and 3 months storage in a freezer. This validated method is sensitive, simple and repeatable enough to be used in pharmacokinetic studies.