Stability indicating RP-HPLC method for simultaneous determination of omeprazole and aspirin in the presence of salicylic acid as degradation product

Reversed-phase high performance liquid chromatographic method (RP-HPLC) was applied for simultaneous determination of aspirin (ASP) and omeprazole (OMP) in presence of salicylic acid (SA) as the most common degradation product of ASP. The drugs were exposed to different stress conditions including acid, alkali, neutral hydrolysis, oxidation, and photodegradation. The separation was carried out on the Thermo Scientific Hypersil ODS column (250 x 4.6 mm, 5 mu m) column. Mobile phase composed of acetonitrile: 0.05 M sodium phosphate monobasic buffer with 0.1% TEA (23:77, v/v). The pH of the buffer was adjusted to pH 3.5 with o-phosphoric acid. The flow rate was 1.2 mL/min. The UV detector was set at 230 nm. The retention time of SA, ASP and OMP were 3.51 +/- 0.19 min, 4.77 +/- 0.23 min, and 16.65 +/- 0.34 min, respectively. Linearity was established for in the range of 1-150 mu g/mL for ASP, 2-80 mu g/mL for OMP and 1-25 mu g/mL for SA. The mean percentage recoveries of ASP, OMP and SA were found to be 99.89% +/- 0.39, 99.76% +/- 0.38 and 100.28% +/- 0.18, respectively. The developed method was validated and successfully applied to the simultaneous determination of ASP and OMP in their tablets. The assay results obtained using the developed method were statistically compared to those obtained by the reported RP-HPLC method and good agreement was observed.