Investigation of the effect of hapten heterology in the enzyme-linked immunosorbent assay for Sudan I

Three hapten derivatives of Sudan I were designed. Hapten-M and hapten-T shared a similar structure, differing only in spacer length. Hapten-X was obtained by reacting with the hydroxyl of Sudan I. Then polyclonal antibodies were produced and different combinations of antibodies and coating antigens were designed. The results showed that it was not the spacer length of hapten but the hydroxyl played an indispensable role in inducing antibody production for Sudan I. More importantly, we verified the experimental results theoretically by calculating the charge distribution of atoms. Next, monoclonal antibody was prepared and the optimal combination of monoclonal antibody and coating antigen was selected. The IC₅₀ was 0.65 ng/mL for Sudan I, and good cross-reactivity of antibody to other azo compounds was obtained. Finally, we acquired the recoveries of 82.2–116.0% and coefficients of variation of 4.3– 10.9% through the analysis of chilli sauce, tomato paste and chilli powder.