Cross-linked time-resolved fluorescence immunochromatographic strip for the detection of neonicotinoid pesticide residues: Competitive principle, rapid, reliable and environmentally friendly pretreatment.

This study focused on three typical neonicotinoid pesticides: Imidacloprid (IMI), thiamethoxam (THI) and clothianidin (CLO). Based on time-resolved fluorescence immunochromatography, a cross-linked time-resolved fluorescence lateral immunochromatography strip (CTRFLIS) was developed. By systematically optimizing the key parameters in the preparation of fluorescent probes and investigating the effects of polymer types, surfactant types, and pH on sample pretreatment, a green pretreatment system based on the synergistic effect of polymers and surfactants were developed, which significantly enhanced detection sensitivity and specificity. A monofactorial variable control method being used, the optimal extraction conditions for various neonicotinoid pesticides in Chinese cabbage and Chinese chive matrices were determined, achieving efficient pesticide extraction without the use of organic solvents. The CTRFLIS prepared in this study had linear detection ranges in Chinese cabbage of 3-600 ng/mL for IMI, 5-300 ng/mL for THI and 1-700 ng/mL for CLO, with limits of detection (LODs) of 0.32 ng/mL, 0.78 ng/mL and 0.13 ng/mL, respectively. In the detection of Chinese chive, the linear ranges were 3-400 ng/mL for IMI, 5-300 ng/mL for THI and 5-400 ng/mL for CLO, with corresponding LODs of 0.28 ng/mL, 0.83 ng/mL and 0.55 ng/mL. The work provides an effective approach to the construction of a rapid, sensitive and low-cost detection platform.