title: Precision improvement for omeprazole determination through stability evaluation.
abstract: A new spectrofluorimetric method for the determination of omeprazole (OMP) based on its degradation reaction catalyzed by ultraviolet (UV) light is proposed. OMP in aqueous solution is very unstable, which renders a serious difficulty for controlling its quality. It does not show native fluorescence, but when exposed to UV radiation, it generates a highly fluorescent degradation product with adequate stability for indirect OMP quantification. Under the studied optimal experimental conditions (pH, temperature, exposure time to UV radiation), a specific rate constant of 2.851 min⁻¹--described by zero-order kinetic--was obtained for the degradation reaction. Using λ(exc) 293 nm and λ(em) 317 nm, a linear relationship was obtained (r² 0.9998) in the concentration range of 0.1 to 1.3 µg mL⁻¹, with a detection limit of 1.07 10⁻³ µg mL⁻¹ (S/N = 3). The methodology developed was successfully applied to OMP quality control in pure drugs and tablet dosage forms without previous treatment, with good tolerance to common excipient, and a high level of concordance between the nominal and experimental values. This work constitutes an important contribution to knowledge of the degradation mechanism of OMP. It has been shown to be appropriate for OMP quality control, to have an adequate sampling rate, low cost instrument, and to be a less polluting procedure.
authors.affiliation: Instituto de Química de San Luis (INQUISAL-CONICET), Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis, Argentina. cperalta@unsl.edu.ar
authors.forename: Cecilia Mariana
authors.initials: CM
authors.lastname: Peralta
authors.forename: Liliana Patricia
authors.initials: LP
authors.lastname: Fernández
authors.forename: Adriana Noemí
authors.initials: AN
authors.lastname: Masi
mesh_terms: D002138:Calibration; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D009853:Omeprazole / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects / Q000592:standards; D010782:Photolysis; D054328:Proton Pump Inhibitors / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects / Q000592:standards; D011786:Quality Control; D015203:Reproducibility of Results; D013050:Spectrometry, Fluorescence / Q000592:standards; D013607:Tablets; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D054328:Proton Pump Inhibitors; D013607:Tablets; D009853:Omeprazole