Kinetic studies of Dexamethasone photodegradation by multivariate curve resolution applied to UV-spectral data

RAZUC, MARIELA; GRÜNHUT, MARCOS; ACEBAL, CAROLINA C.; GARRIDO, MARIANO; FERNANDEZ BAND, BEATRIZ S.

Córdoba

Congreso; 3° Reunión Internacional de Ciencias Farmacéuticas - RICiFa 2014; 2014

Dexamethasone is a widely used synthetic anti-inflammatory corticosteroid. Consequently, high amounts of this compound are released into the environment through different pathways. Therefore, it is important to know the effect of different environmental factors, like UV-radiation and temperature, upon this compound. Despite its importance, very little has been done with respect to photodegradation studies of dexamethasone. In these researches the analytical determinations were performed using separative techniques- mainly HPLC. This work presents a simple and economical exploratory study of photochemical degradation of dexamethasone to understand the kinetic of photodegradation and know the rate constants of the process. The photodegradation reactions were carried out in a flow system with a photoreactor, coupled to a UV-Vis diode array detector. The photoreactor source was a 15W germicidal lamp (max. 254 nm). The photodegradation was performed for 3.5 min at 50ºC. The dexamethasone solutions were prepared in pure water. The spectrophotometric monitoring was performed in a continuous way, almost at real time. The spectra recorded throughout the photodegradation time were arranged in matrices and subsequently analyzed by the chemometric techniques multivariate curve resolution. The application of these techniques upon the experimental data allows obtaining the kinetic profiles and the corresponding pure response profiles (UV?Vis spectra) of dexamethasone and its main degradation products. Also, these analyses provide the kinetic rate constants for the reactions.The degradation profile of dexamethasone and of five photodegradation products could be observed throughout the reaction. All the compounds showed different UV-Vis spectra. The obtained rate constant for the photodegradation reaction of dexamethasone in water was 0.0268 s-1. This preliminary result is promising as a starting point to study the kinetic degradation of dexamethasone in several media. The proposed method constitutes a fast, simple and economical technique to study the photodegradation kinetic of dexamethasone, avoiding the use of separation techniques.