Monoclonal antibody-based icELISA for the screening of diazinon in vegetable samples

Diazinon (DAZ) is an organophosphorus pesticide (OP), which is commonly used to prevent and control harmful pests that endanger agricultural products. In this study, we developed a novel heterology coating strategy for the immunoassay of DAZ. The DAZ coating hapten can be directly conjugated to the carrier protein without requiring a spacer arm. This proposed hapten coating strategy is time-saving and significantly improves the sensitivity of the immunoassay due to the lack of a spacer arm. The as-synthesized coating antigen was used to screen the monoclonal antibody (mAb). Finally, the developed indirect competitive enzyme-linked immunoassay (icELISA) showed IC₅₀ and limit of detection (LOD) values of 0.58 ng mL^-1 and 8 pg mL^-1, respectively. This method exhibited negligible cross-reactivity towards other analogues, and the recoveries of samples (cucumber, cabbage, and lettuce) ranged from 92.6% to 125.4%, with coefficients of variance (CV) below 12%. Good correlation between icELISA and high-performance liquid chromatography mass spectrometry (HPLC-MS/MS) was obtained. The proposed icELISA was an ideal tool for monitoring DAZ residues in food samples.