High-Sensitivity Fluorescent Sensing Platform for Rapid and Selective Detection of Chlorpyrifos Pesticide in Water Samples Using Terbium-Isatin-3-allyl Complex.

Abstract

The detection of organophosphorus pesticides, particularly chlorpyrifos, in environmental samples is essential due to their widespread use and associated health risks. In this study, we developed a high-sensitivity fluorescent sensing platform utilizing an Isatin-3-allyl-terbium (IS-Tb) complex in solution for the rapid and selective detection of chlorpyrifos in various water samples. The proposed chemical structure of the complex in solution was evaluated using molar ratio method. The IS-Tb complex was characterized in solution, as it was not isolated in the solid state. To assess its structural and optical properties, several characterization techniques were employed. UV-Vis spectrophotometry was used to evaluate the absorption characteristics, and spectrofluorimetry was applied to assess the fluorescence properties. Additionally, the stoichiometry of the complex was determined using the molar ratio method, which confirmed a 1:1 ligand-to-metal ratio and provided the optimal conditions for sensing chlorpyrifos. The IS-Tb complex exhibited weak intrinsic fluorescence, which was significantly enhanced upon interaction with chlorpyrifos, enabling sensitive and quantitative analysis. Methanol was identified as the best solvent for maximizing the sensitivity of chlorpyrifos detection. The sensor demonstrated a wide linear detection range from 0.006 to 28 µg/L, with a low limit of detection (LOD) of 2 ng/L. The sensor's selectivity for chlorpyrifos over other commonly encountered pesticides (13 organophosphorus) and environmental contaminants was high, ensuring minimal interference. The performance of the sensor was validated using spiked water samples, yielding an average recovery of 101% with a relative standard deviation (RSD) of less than 5%. These results suggest that the proposed sensing platform is a powerful tool for the environmental monitoring of chlorpyrifos, with significant implications for public health protection and regulatory compliance.