Gold nanoparticle-based immunochromatographic assay for rapid detection of imazalil

Imazalil (IMZ) is a commonly used fungicide for controlling fungus in agriculture, leaving residual IMZ in crops that could be hazardous to human health. In this work, we designed IMZ haptens for mice immunization and prepared sensitive monoclonal antibody (mAb) against IMZ. The subtype of anti-IMZ mAb is IgG2a. It possessed a half inhibition concentration (IC₅₀) of 0.95 ng mL^-1 and showed no cross-reactivity against other chemicals in ic-ELISA. Taking advantage of the mAb, we developed a gold nanoparticle-based immunochromatographic assay (GICA) for the rapid detection of IMZ in grapes and tomatoes. The assay gave a visual limit of detection (vLOD) of 25 ng g^-1 and cut-off value of 500 ng g^-1 in both samples. According to the calibration curves, the calculated LOD were 4.12 ng g^-1 and 4.70 ng g^-1 in grapes and tomatoes, respectively. The recovery rates of IMZ ranged from 84.7% to 104.4% with variation coefficients (CVs) of 5.7-11.8% in spiked samples, indicating a potent practicability of the GICA. The whole GICA process took 30 min. Therefore, the developed assay can be used for on-site detection and quantitation of IMZ in grape and tomato samples.