Extractive Spectrophotometric Determination of Omeprazole in Pharmaceutical Preparations

Purpose: To develop a simple, rapid and selective method for the extractive spectrophotometric determination of omeprazole using acidic dyes.
Methods: Extractive spectrophotometric determination of omeprazole was developed using acidic dyes - bromophenol blue and orange G - as ion-pairing agents in aqueous medium (pH 7.0 and 6.0, respectively). The ion pair chromogen formed, which was extracted with chloroform, was measured quantitatively at 408 nm and 508 nm, respectively. The developed method was used to analyse commercial omeprazole tablets.
Results: Using bromophenol blue and orange G dyes, the ion-paired formed obeyed Beer's law in the ranges 5 - 30 μg/ml and 50 - 250 μg/ml at 408nm and 503nm, respectively, with molar absorptivities of 1.712 × 10³ L mol^-1 cm^-1 and 2.095 × 10³ L mol^-1 cm^-1, respectively, for omeprazole,. The purity of omeprazole obtained was 98.1±0.9 and 99.7±0.3, respectively. Standard deviation (S.D.), % relative standard deviation (% R.S.D.) and standard error were 0.001 - 0.013, 0.94 - 1.07 % and 4 × 10^-4, respectively. The complexes formed were stable for approx. 3 h.
Conclusion: Recovery studies gave satisfactory results indicating that none of the major additives/excipients interferred with the assay method. Therefore, a simple, rapid and selective method was developed for extractive spectrophotometric determination of omeprazole. This method may be useful for routine laboratory analysis of omeprazole.