Determination Of Omeprazole Enantiomers In Human Plasma By High Performance Liquid Chromatography

OBJECTIVE:Proton pump inhititors (PPIs) are a group of drugs whose main action is a pronounced and long-lasting reduction of gastric acid production.The PPIs most used clinicaily in the treatment of acid-related diseases are omeprazole (OME), lansoprazole (LAN), pantoprazole (PAN).All these PPIs have a stereogenic center at the sulfur atom .OME and PAN are clinically administered as a racemic mixture. Since the omeprazole,lansoprazole,pantoprazole enantiomers may have different physiological effects in biological systems, it is significance that both enantiomers could be determined and analysed, not only the racemates. PPIs have been performed by capillary chromatography (CE), supercritical fluid chromatography (SFC), enantioselective HPLC methods. HPLC method is a simple, rapid, reliable, selective, accurate method for the determination of PPIs.The direct HPLC method for the separation of omeprazole, lansoprazole, pantoprazole enantiomers was carried on derivatized cellulose and amylose chiral stationary phase (Chiralpak AD column, Chiralpak AS column, Chiralcel OD column, Chiralcel OJ column) was studied. In this assay, a high sensitivity and selectivity HPLC method for the analysis and quantification of omeprazole enantiomers in human plasma was also established.METHODS:Chromatography conditions: column: Chiralpak AD column (250 mm×4.6 mm, 10μm, Daicel Chemical), Chiralcel OJ column (250 mm×4.6 mm,10μm, Daicel Chemicals), Chiralpak AS column (250 mm×4.6 mm , 10μm, Daicel Chemicals), Chiralcel OD column (250 mm×4.6 mm, 10μm, Daicel Chemicals). Mobile phase: hexane-isopropanol, hexane-ethanol,hexane-isopropanol-ethanol, hexane-isopropanol-methanol. The flow rate was 0.5-1mL/min. The absorbance wavelength of omeprazole, lansoprazole and pantoprazole was 302 nm, 285 nm, and 289 nm, respectively. The column temperature was 25℃and the injection volume was 100μL.Plasma smples Chromatography conditions: Agilent BOND ODS-C18 Solid Phase Extraction (SPE) cartidges were used to extract the enantiomers from plasma samples and the chiral separation was carried on a Chiralpak AD column (250 mm×4.6 mm, 10μm, Daicel Chemical), with hexane-ethanol (30:70, v/v) as the mobile phase with the flow rate of 0.5 mL/min. The detection was carried out at 302 nm. The column temperature was 25℃and the injection volume was 100μL.RESULTS:The recoveris of (-)-(S)-omeprazole were between 96.7%～100.4%, and (+)-(R)-omeprazole were between 97.4%～100.2% in the determination of plasma samples. Intra- and inter-day precision values were lower than 3.3% and 4.7%, respectively. The linear ranges for (-)-(S)-omeprazole and (+)-(R)-omeprazole were 5~1000 ng/mL, (-)-(S)-omeprazole (n = 5, r = 0.9998), (+)-(R)-omeprazole (n = 5, r = 0.9997) with a detection limit of 2 ng/mL at a signal/noise ratio of 3.CONCLUSION:The established high-performance liquid chromatography separation of omeprazole, lansoprazole, pantoprazole enantiomers could be applied to the determination of optical purity, quality control and stereoselective pharmacokinetics research. This method presented in this assay is rapid, reliable, simple and high sensitivity with a satisfactory result in the study the pharmacokinetics of omeprazole enantiomers.