Rapid Fluorescent Determination of Imidacloprid in Food Samples Using a Phenothiazine-oxadiazole Probe

A phenothiazine-oxadiazole derivative (WA-1) was synthesized and used as a fluorescent probe for the rapid and selective determination of imidacloprid (IMI) in food samples. The probe exhibited strong fluorescence emission at 470 nm, which was efficiently quenched upon IMI interaction. Under optimized conditions, the fluorescence response showed a good linear relationship over the concentration range of 0.025-1.0 ppm, with a low detection limit of 8.3 × 10^- 3 ppm. The developed sensing system demonstrated rapid response behavior (2 min) and high selectivity toward IMI in the presence of other pesticides and common metal ions. The proposed method was successfully applied to determine IMI in different food matrices, providing satisfactory recovery values and good agreement with the reference HPLC method. The sensing mechanism was supported by theoretical calculations, suggesting that fluorescence quenching originates from the modulation of the intramolecular charge transfer pathway through intermolecular interactions with IMI. These findings demonstrate the potential of WA-1 as a simple, sensitive, and reliable fluorescence platform for monitoring imidacloprid residues in food.