Results: The appropriate chromatographic conditions were found out for quantitation of omeprazole impurities D and E, using InertsustainÒ C8 column (250 x 4.6 mm; 5 µm), mixture of acetonitrile and phosphate buffer pH 7.6 (25: 75, v / v) as eluent in isocratic mode, flow rate of 1.0 ml / min, and detection wavelength of 280 nm.