Fully automated gradient elution liquid chromatographic assay of omeprazole and two metabolites

An automated liquid chromatographic method for the determination of omeprazole and two metabolites in plasma and urine is described. It utilizes the Technicon Fully-Automated-Sample-Treatment-LC system (FAST(R)-LC). Sample preparation is achieved by air-segmented continuous-flow providing solvent extraction, evaporation to dryness and reconstitution before injection onto a reversed-phase column. The compounds are separated by isocratic or gradient elution with acetonitrile-phosphate buffer mobile phases and quantified by UV-measurements at 302 nm. The limit of determination (relative standard deviation 10-15%) is 50 nmol l(-1) in plasma (800 microl) and 200 nmol l(-1) in urine (200 microl). The sample capacity is six or three samples per hour, depending on the elution mode.