2.3. Preparation of hapten-protein conjugates

For pesticide immunogens, haptens were covalently attached to the lysine groups of BSA by the active ester method. To synthesize the hapten-OVA conjugates used as coating detective antigens, the mixed anhydride method was adopted using isobutyl chloroformate as the coupling reagent. Conjugates of OA-BCP and OA-BSA respectively serving as the immunogen and the coating antigen were prepared according to a previous research method (Lu et al., 2012). Purification was performed by dialyzing extensively with PBS, followed by treatment with a protein concentrator.