O-(ß-hydroxyethyl)rutosides determination by micellar flow injection (FI)-spectrofluorimetry.

A simple, eco-friendly, sensitive and economic flow injection spectrofluorimetric method was developed for the determination of O-(ß-hydroxyethyl)rutosides. The procedure was based on the use of an anionic surfactant such as sodium dodecyl sulfate to provide an appreciable O-(ß-hydroxyethyl)rutosides fluorescence enhancement, increasing considerably the sensitivity of detection. All the variables affecting the fluorescence intensity were studied and optimized. The flow rate was 5 mL/min with detection at 450 nm (after excitation at 346 nm). A linear correlation between drug amount and peak area was established for O-(ß-hydroxyethyl)rutosides in the range of 0.01-200 µg/mL with a detection limit of 0.001 µg/mL (s/n=3). Validation processes were performed by recovering studies with satisfactory results. The new methodology can be employed for the routine analysis of O-(ß-hydroxyethyl)rutosides in bulks as well as in commercial formulations.

Precision improvement for omeprazole determination through stability evaluation.

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.

Online naphazoline quality control by micellar-enhanced spectrofluorimetry.

The aim of this study was to develop a method for online spectrofluorimetric quality control of naphazoline (NPZ) in pharmaceuticals and raw drugs. A combination of a flow-injection analysis (FIA) system with micellar-enhanced fluorescence detection is presented as a powerful alternative for the rapid and sensitive analysis of naphazoline. Since NPZ shows low native fluorescence, the use of an anionic surfactant, such as sodium dodecyl sulphate (SDS), provides a considerable enhancement of fluorescence intensity and the nature of the technique allows a possible and easy adaptation to a FIA system. Using λ(exc) = 280 nm and λ(em) = 326 nm, a good linear relationship (LOL) was obtained in the range 0.003-10 µg mL(-1) with a detection limit (LOD) of 3 × 10(-4) µg mL(-1) (s/n = 3). Parameters related to the nature of the analytical signal and to the FIA manifold were optimized. Satisfactory recoveries were obtained in the analysis of commercial pharmaceutical formulations. The proposed method is simple, accurate and allows for high-speed sampling and considerably shorter analysis times. In addition, it requires inexpensive equipment and reagents and has easy operational conditions and no side effects, thus avoiding environmental pollution through toxic waste.