SIMULTANEOUS DETERMINATION OF OMEPRAZOLE an‎d ITS METAL COMPLEXES BY REVERSED-PHASE HIGH PERFORMANCE LIQUID CHROMATOGRAPHY IN PHARMACEUTICAL FORMULATIONS

A sensitive, precise, selective and accurate reversed-phase high-performance liquid chromatographic (RPHPLC)method has been developed for the simultaneous determination of omeprazole in Risek® capsules.Omeprazole and the internal standard, diazepam, were separated by Shim-pack CLC-ODS 0.4 × 25 cm, 5mm particle size column. The mobile phase was Methanol-Water (80:20, v/v), pumped isocratically at ambient temperature. Analysis was run at a flow rate of 1.0 mL/min at a detection wave length of 302 nm.The method was specific and sensitive with a detection limit of 3.5 ng/mL at a signal-to-noise ratio of 4:1.The limit of quantification was set at 6.25 ng/mL. The calibration curve was linear over a concentration range of 6.25-1280 ng/mL. Precision and accuracy, demonstrated by within-day, between-day assays, and inter-operator assays were lower than 10%. The in vitro availability of omeprazole in presence of manganese, cobalt, nickel, copper and zinc was studied by this method. Recovery of omeprazole inpresence of various metals was from 41% to 74%.