On-site detection of an emerging fungicide: developing an immunochromatographic assay for thifluzamide through de novo hapten design and synthesis.

Thifluzamide (THF), a novel succinate dehydrogenase inhibitor fungicide, is widely used to control crop diseases; however, excessive residues pose potential risks to human health. To guide hapten design, a detailed analysis of the spatial structures and electrostatic potential distributions of THF and its haptens was conducted using computer-assisted molecular modeling. The challenges in synthesizing haptens that simultaneously contain both 1,3-dibromo-5-(trifluoromethoxy)benzene and 2-methyl-4-(trifluoromethyl)thiazole moieties were also addressed, ultimately leading to the development of a highly specific and sensitive monoclonal antibody with a half-maximal inhibitory concentration of 0.42 ng/mL. Based on this mAb, an immunochromatographic assay was established and successfully applied to detect THF residues in real crop samples. The visual limits of detection were 100 μg/kg for rice and 200 μg/kg for potato and peanut samples. Overall, this study provides a rapid and reliable on-site detection method for THF residues in agricultural products, offering strong technical support for food safety monitoring.