Competitive ELISA of Thiabendazole Residues in Produce Using Indirectly Immobilized Monoclonal Antibodies

Abstract

An enzyme‐linked immunosorbent assay (ELISA), developed originally for analysis of thiabendazole (2‐[4‐thiazolyl] 1H‐benzimidazole, TBZ) residues in bovine liver, was used to analyze residues of this post‐harvest fungicide in the peel of apple, potato, orange, grapefruit and banana. Residues were extracted by soaking peels overnight in 80% methanol and filtering the decanted supernatants. A 20‐fold dilution eliminated significant matrix effects. The ELISA has a limit of detection of 0.1 ppm in peel samples, corresponding to 10–40 ppb in the whole fruit or tuber. The ELISA employs a monoclonal antibody layer, immobilized indirectly via a rabbit anti‐mouse IgG secondary antibody, and horseradish peroxidase‐conjugated 5‐succinamido‐TBZ. Assay wells coated in this way could be dried and stored for at least 6 months without detectable changes in assay parameters. The method exceeds the required sensitivity for regulatory monitoring of TBZ residues in the US, and offers greater speed and specificity than previously reported methods.

Keywords:

• Thiabendazole
• ELISA
• peel
• extraction