Abstract
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.
Highlights
Omeprazole (OMZ) is a selective and irreversible proton pump inhibitor
The use of micro-well plates as reaction vessels instead of normal volumetric flasks can reduce both consumption and cost of organic solvents, and decrease the risk of human exposure to toxic solvents [19]. These facts promoted our interest in utilizing DCNQ and BROM reagents for developing novel, simple and low-cost kinetic spectrophotometric methods for the determination of OMZ in quality control laboratories (QCLs)
The CT reaction was monitored at 45 ± 2 °C and the absorbance was recorded as a function of time each 5 min for 40 and 25 min for DCNQ and BROM, respectively
Summary
Omeprazole (OMZ) is a selective and irreversible proton pump inhibitor. It blocks the stomach acid release via specific inhibition of the H+/K+-ATPase enzyme system present at the secretory surface of gastric parietal cells. The sophisticated instrumentation, high analysis cost and long time required to obtain the most suitable conditions limit the routine use of the separation-based techniques in quality control laboratories (QCLs) where higher sensitivity is not required Among these techniques, spectrophotometry stands out, as the most effective and convenient analytical technique as compared to the others with respect to simplicity, cost, and wide availability in most QCLs. matrix interference disadvantage the direct UV spectrophotometric analysis of OMZ [3]. The use of micro-well plates as reaction vessels instead of normal volumetric flasks can reduce both consumption and cost of organic solvents, and decrease the risk of human exposure to toxic solvents [19] These facts promoted our interest in utilizing DCNQ and BROM reagents for developing novel, simple and low-cost kinetic spectrophotometric methods for the determination of OMZ in QCLs
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