Omeprazole, resolution

Figure 3.6 Resolution of the enantiomers of omeprazole using a protein-derived CSP. The chromatogram shows the analysis of esomeprazole API artificially enriched with 0.1% w/w of the R-enantiomer. (Conditions cti-AGP 10 cm X 0.4 cm i.d. mobile phase sodium phosphate [pH 6.0, 60 mM] acetonitrile [85 15, v/v] flow rate 1 mbmin detection UV at 302 nm column temperature ambient sample preparation 0.02mg/ml in sodium phosphate [pH 11.0, 18 mM] methanol [98 2, v/v] injection volume 20 pi.)...

Figure 6.6. Metabolite profiles of omeprazole in human plasma (a) base peak ion chromatogram of unprocessed data and (b) base peak ion chromatogram of MDF-processed data exhibiting all metabolite peaks present and some endogenous peaks. High-resolution LC-MS data were obtained for a human plasma sample spiked with omeprazole metabolites generated by microsomal incubation (the equivalent of a 1.0-mL plasma injection). A MDF ivas set at 50 mDa around the apparent mass defect of the omeprazole ion.

Agbaba et al. [56] developed an HPTLC method for the determination of omeprazole, pantoprazole, and their impurities omeprazole sulfone and N-methylpantoprazole in pharmaceutical. The mobile phase chloroform-2-propanol 25% ammonia-acetonitrile (10.8 1.2 0.3 4), enables good resolution of large excesses of the drugs from the possible impurities. Regression coefficients (r > 0.998), recovery (90.7-120.0%), and detection limit (0.025-0.05%) were validated and found to be satisfactory. The method is convenient for quantitative analysis and purity control of the compounds. 

Rezk et al. [74] developed and validated a reversed-phase HPLC assay method for the simultaneous quantitative determination of omeprazole and its three metabolites in human plasma. The method provides excellent chromatographic resolution and peak shape for the four components and the internal standard within a 17-min run time. The simple extraction method results in a clean baseline and relatively high extraction efficiency. The method was validated over the range of 2-2000 ng/ml. The resolution and analysis for the four analytes omeprazole, hydroxyome-prazole, omeprazole sulfone, and omeprazole sulfide and the internal standard utilized a Zorbax C18 (15 cm x 3 mm, 5 /im) with a Zorbax C18 (12.5 cm x 4.6 mm) guard column. The mobile phase consisted of two components. Mobile phase A was 22 mM phosphate monobasic, adjusted to a pH of 6 with diluted sodium hydroxide. This solution was filtered through a 0.45-/im membrane filter, then mixed as 900 ml buffer to 100 ml methanol. Mobile phase B was composed of 100 ml of the phosphate buffer as mobile phase A, mixed with 800 ml of acetonitrile, 100 ml of methanol, and 100 /A of trifluoroacetic acid with an initial flow-rate of 0.55 ml/min and detection at 302 nm. 

Sivasubramanian and Anilkumar [81] described a simple reversed-phase HPLC method for the determination of omeprazole and domperi-done from tablet formulations. The analysis was carried out on a Hypersil ODS Ci8 (15 cm x 4.6 mm, 5 /jm) column using a mobile phase of methanol- 0.1 M ammonium acetate, pH 4.9 (60 40). The flow-rate and rim time were 1 ml/min and 10 min, respectively. The eluent was monitored at 280 nm. The method was reproducible, with good resolution between omeprazole and domperidone. The detector response was linear in the concentration range of 10-60 /[Pg.222]

Bonato and Paias [136] developed two sensitive and simple assay procedures based on HPLC and capillary electrophoresis for the enantio-selective analysis of omeprazole in pharmaceutical formulations. Racemic omeprazole and (S)-omeprazole were extracted from commercially available tablets using methanol-sodium hydroxide 2.5 mol/1 (90 10). Chiral HPLC separation of omeprazole was obtained on a ChiralPak AD column using hexane-ethanol (40 60) as the mobile phase and detection at 302 nm. The resolution of omeprazole enantiomers by capillary electrophoresis was carried out using 3% sulfated /1-cyclodextrin in 20 mmol/1 phosphate buffer, pH 4 and detection at 202 nm. 

Olsson and Blomberg [141] enantioseparated omeprazole and its metabolite 5-hydroxyomeprazole using open tubular capillary electrochromatography with immobilized avidin as chiral selector. The separation was performed with open tubular capillary electrochromatography. The protein avidin was used as the chiral selector. Avidin was immobilized by a Schiffs base type of reaction where the protein was via glutral-dehyde covalently bonded to the amino-modified wall of a fused-silica capillary, 50 /an i.d. Both racemates were baseline resolved. Resolution... 

To avoid the expensive use of deuterated solvents for H/D exchange experiments, Tolonen et al. [21] have described the postcolumn infusion of D2O to facilitate the LC-MS detection and identification of labile protons in a column eluant. Whilst acknowledging the potential limitations with respect to a reduced level of exchange, and hence sensitivity, compared to the use of deuterated mobile-phase solvents, they optimized the column effluent flow rate (via a splitting connector) with the infused D2O flow rate to enable the very useful determination of up to four labile protons. The method was exemplified by the differentiation of hydroxylated metabolites of the alkaloidal drugs imipramine and omeprazole (Figure 13.5) from the N-oxide and sulfone metabolites, respectively [21]. This was a differentiation that could not be achieved by high-resolution mass measurements. 

KahrUas PJ, Falk GW, Johnson DA, Schmitt C, ColUns DW, Whipple J, D Amico D, Hamelin B, Joelsson B. Esomeprazole improves healing and symptom resolution as compared with omeprazole in reflux oesophagitis patients a randomized controlled trial. The Esomeprazole Study Investigators. Aliment Pharmacol Ther 2000 14(10) 1249-58. 

Direct resolution of omeprazole without prior derivatization ( classical salt formation). 

Resolution of omeprazole via covalent diastereomeric derivatives (in principle following a procedure described in Section 7.3 or variations thereof). 

A high-resolution micrograph of a stimulated parietal cell after inhibition by radioactive omeprazole, showing the localization of the binding of this PPI exclusively to the active secretory canaliculus. The dark grains indicate the covalent binding of acid-activated omeprazole to the pump in the secretory canaliculus. 

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