Indirect spectrofluorimetric determination of omeprazole by its quenching effect on the fluorescence of Tb3+-1,10-phenanthroline complex in presence of bis (2-ethylhexyl) sulfosuccinate sodium in capsule formulations

Purpose: Omeprazole (OMZ) is a substituted benzimidazole, which is used in the treatmentof gastric acid related disorders. The aim of this study was the development and validationof a rapid, simple and reliable fluorimetric method for determination of OMZ inpharmaceutical formulations based on fluorescence quenching of Tb3+-1, 10-phenanthrolinecomplex.Method: For the determination of OMZ, aliquots of Tb3+, bis (2-ethylhexyl) sulfosuccinatesodium (AOT), 1,10-phenanthroline (phen) solutions (in optimal concentrations), aliquotsof working OMZ solution and Tris-HCl buffer (pH 7.0) solution were added to 5 mLvolumetric flasks. The mixture was then diluted with distilled water and allowed to standfor 30 min and the fluorescence intensity was then measured at 545 nm using an excitationwavelength of 300 nm. Matrix systems of OMZ (OMZ capsules with a nominal of 20 mg)were prepared by powdering and mixing the contents of ten capsules of OMZ. A portion of10.0 mg of this powder was then accurately weighed and dissolved in about 10 mL of 0.1M NaOH solution and filtered into a 100 mL volumetric flask. The residue was washedseveral times with water and solution was diluted to the mark. A suitable aliquot of thissolution was applied for fluorimetric determination of OMZ. The recovery assay wascarried out using the same procedure by addition of known amounts of OMZ.Results: It was found that the fluorescence intensity of Tb3+-1, 10-phenanthroline complexcan be greatly quenched by omeprazole in the presence of AOT. Under optimal conditions,the quenched fluorescence intensity was found to be proportional to the concentration ofomeprazole in the range of 0.05-10 μg/mL. The detection limit was 0.016 μg/mL. Therelative standard deviation values for 6 replicated determinations of 0.3 and 1.5 μg/mL ofOMZ were 3.5 and 1.5 %, respectively, The RSD of intraday was 2.6 and that of interdaywas 3.4 % for 4 and 2 μg/mL of OMZ, respectively.Conclusion: Based on the obtained results, a simple, rapid and selective spectrofluorimetricmethod was developed for determination of omeprazole in its capsule formulations withexcellent reproducibility and allowed the interference-free determination of OMZ in realsamples.