A SIMPLE SOLID-PHASE RADIOIMMUNOASSAY FOR AFLATOXIN B1

A solid-phase radioimmunoassay (RIA) for aflatoxin B₁ (afla B₁) was developed. This method involved the incubation of afla B₁, both labelled and unlabelled, with immunoglobulin (IgG)-sepharose gel which was prepared by conjugation of the IgG highly specific to afla B₁ with CNBr-activated sepharose gel, followed by a filtration step. The binding capacity was determined by counting the radioactivity in the filtrate. Studies with different afla B₁ analogues revealed that the IgG-gel bound most effectively with B₁. Binding of afla B₂, G₁, G₂, and aflatoxicol to the IgG-gel was less effective in comparison with the IgG before coupling. Between 0.5–5.0 ng per assay, the displacement of radioactivity from the gel was directly proportional to the amount of afla B₁ present. Using a simple extraction procedure without clean-up step, the recovery yields for afla B₁ in the contaminated corn or wheat at levels of 5 ppb or above were above 60%.