Aged commercial imidacloprid formulation alters the thermal, optical, and electrical behavior of aqueous matrices

Juan Hernández , Fredy Mesa , Juan Daniel Hernández Vargas , Andre Riveros Rivera

Environmental persistence of neonicotinoid insecticides is influenced by their long-term stability and interactions with aqueous matrices. In this study, the thermal, optical, and electrical properties of a commercial imidacloprid formulation (Confidor 350 SC) were characterized under environmentally representative conditions. Solutions were prepared using three types of water (Distilled, Rain, and Mud) and exposed to three temperatures (5 °C, 25 °C, and 50 °C), considering products with three expiration states (valid, near-expiry, and expired). Thermal analysis revealed that the formulation maintains macroscopic stability even after the expiration date; however, the aqueous matrix significantly modulates heat transfer dynamics. UV-Vis absorbance measurements showed spectral shifts dependent on water type and temperature, suggesting subtle chemical transformations. Electrical characterization, using impedance spectroscopy and current-voltage curves, revealed significant interactions among water type, storage time, and temperature that affect conductivity and dielectric behavior. Overall, the results indicate that although thermal properties remain relatively stable, optical and electrical tools allow more sensitive detection of aging effects and environmental conditions. This integrative approach provides a solid foundation for assessing the stability and transformation of pesticides in aquatic ecosystems, with implications for modeling their mobility and persistence in agricultural contexts.