Novel Analytical Study For The Charge-Transfer Reactions Of Omeprazole With 2,3-Dichloro-Naphthoquinone And 2,3,5,6-Tetrabromo- 1,4-Benzoquinone: Application For The Development Of Microwell Assay Of Omeprazole

Novel analytical study was performed in order to develop and validate new high-throughput microwell-based spectrophotometric assays for determination of omeprazole (OMZ) in its pharmaceutical formulations. The proposed assays were based on the charge-transfer (CT) reaction of OMZ with 2,3-dichloronaphthoquinone (DCNQ) and 2,3,5,6-tetrabromo-1,4-benzo-quinone (BROM). In the present study, the CT reactions was carried out in microwell plates as reaction vessels in order to increase the automation of the assays and the efficiency of its use in quality control laboratories (QCLs). All factors affecting the CT reactions were carefully studied, and the conditions were optimized. Kinetics and stoichiometry of the CT reactions were investigated, and the mechanism was postulated. Activation energy of the CT reactions was determined and found to be 13.87 and 16.27 Kcal mol−1 for the reaction of OMZ with DCNQ and BROM, respectively. The initial rate and fixed time methods were applied for generating the calibration graphs for determination of OMZ concentrations. Under the optimum conditions, the linear range was 0.145 – 1.45 x 10-4 and 1.45 – 7.25 x 10-4 M with LOD of 0.6 and 6.0 microgram ml-1 for DCNQ and BROM, respectively. Analytical performance of the proposed methods, in terms of accuracy and precision, was statistically validated and the results were satisfactory; RSD was <2.8% for both repeatability and reproducibility. The proposed methods were successfully applied to the analysis of OMZ in its dosage forms and the recovery results (98.64 – 100.6 ± 0.25 -2.74 %) were comparable with those of the reported method. The developed method may provide a safer and economic tool for the analysis of OMZ in QCLs.