A rapid HPLC-DAD method for separation and determination of omeprazole extracted from human plasma

A high-performance liquid chromatographic (HPLC) method for the determination of omeprazole in human plasma is described. Omeprazole and the internal standard (H168/24) were extracted from plasma samples by solid phase extraction (SPE) using a polymeric sorbent-based cartridge. The separation was accomplished under reversed phase conditions using an Eclipse XDB-C8 Rapid Resolution (4.6 x 50 mm) column. The mobile phase consisted of 23% acetonitrile and 77% of 30.4mM Na2HPO4 and 1.76mM KH2PO4 solution, pH 8.4, in which a gradient elution was used to linearly change solvent composition to 33% acetonitrile and 67% phosphate buffer during the first minute. Absorbance was monitored at 302 nm for omeprazole and at 294 nm for the internal standard and the total analysis time was 4 minutes. The lower limit of quantitation was 10 ng/mL and the calibration function is linear to 2000ng/mL. This method has been shown to be appropriate for pharmacokinetic studies involving children.