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

This work aims at describing the kinetic model of nitrofurazone photodegradation by a novel chemometrictechnique, hybrid hard–soft multivariate curve resolution (HS-MCR). The study was applied toUV-spectral data from the photolysis of nitrofurazone solutions at different concentrations and exposedunder varying illuminance power. The HS-MCR method was able to elucidate the kinetics of the photodegradationprocess and to determine the rate constants, and estimating at the same time the purespectra of the degradation products. Exposure to light of the drug gave a first rapid isomerization tothe syn-form that in turn underwent degradation furnishing a mixture of yellow-red products. The photodegradationprocess could be explained with a kinetic model based on three consecutive first-orderreactions (A > B, B > C and C > D). These results were confirmed by application of the MCR procedure tothe analysis of the data obtained from HPLC-DAD analysis of the nitrofurazone samples at different reactiontimes. The kinetic model was observed to be dependent on experimental conditions. The samplesat higher concentrations showed rate constants lower than the diluted samples, whereas an increaseof the rate of all degradation processes was observed when the light power also increased. This workshows the power of the hybrid hard- and soft-multivariate curve resolution as a method to deeply studydegradation processes of photolabile drugs.