Simultaneous Determination of Omeprazole and its Metabolites in Human Plasma by HPLC using Solid-phase Extraction

Abstract

A rapid, simple and sensitive HPLC assay was developed for the simultaneous determination of omeprazole and its major metabolites in human plasma using a solid-phase extraction procedure. Eluent (50 μL) was injected on an μBondapak C18 reversed-phase column (4.6 mm i.d., 250 mm; 10 μm). The mobile phase consisted of 0.05 m phosphate buffer (pH 7-5) and acetonitrile (75:25, v/v) at a flow rate of 0–8 mL min−1. UV detection was at 302 nm. Mean recovery was greater than 96% and the analytical responses were linear over the omeprazole concentration range of 50–2000 ng mL−1. The minimum detection limits were 10, 10 and 15 ng mL−1 for omeprazole, omeprazole sulphone and hydroxyomeprazole, respectively. The method was used to determine the plasma concentration of the respective analytes in four healthy volunteers after an oral dose of 40 mg omeprazole. The extraction procedure and HPLC method is simple, precise and quick, and suitable for the study of pharmacokinetic disposition and metabolism of omeprazole, which is extensively metabolized in man.