Non-destructive monitoring of cyenopyrafen residues on strawberry via 280 nm UV-excited fluorescence of co-formulated organic solvents

Cyenopyrafen is widely used to control spider mites during strawberry cultivation, and its residues should be monitored non-destructively after harvest. This study explores a fluorescence imaging system for estimating cyenopyrafen residues from a commercial pesticide formulation (STARMITE®, Nissan Chemical co., Japan). Excitation-emission matrix (EEM) analysis guided the imaging setup using 280 nm UV light. While cyenopyrafen itself is non-fluorescent, persistent formulation components associated with the solvent system emitted strong blue fluorescence, serving as an indirect index of residue level. Fluorescence images of 71 samples were captured and correlated with HPLC measurements. A partial least squares regression (PLSR) model developed using 53 samples (<5 mg/kg) achieved R² = 0.92, RMSE = 0.38, and a detection limit of 0.44 mg/kg. This method enables non-destructive, accurate, and cost-effective residue estimation and is suitable for high-throughput post-harvest screening. The approach also shows potential for broader application to other formulation-based pesticide detection tasks.