Characterization of Fipronil in Micellar Medium with Brij 35

Abstract

Fipronil is a phenyl pyrazole used as an insecticide to combat termites, moths, and locusts. Its low solubility in water represents a problem with its commercial formulations. In this work, an aqueous micellar medium was formed with Brij 35, calculating the critical micellar concentration at 0.01% (w/v) by UV-visible spectrophotometry and conductimetry. In this medium, the apparent pka was estimated at 12.6 from spectrophotometric data by the graphical method and Partial Least Squares Regression. Finally, its degradation kinetics in this medium at pH 12 was studied, finding that it conforms to a first-order model, with a half-life of 3.3 h, higher than the 2.4 h reported by other authors for an aqueous medium. In conclusion, the micellar medium favored the solubility of the compound in aqueous medium, allowing the estimation of its pka and retarding its chemical degradation.