Use of polyethylene glycol in the radioimmunoassay of aflatoxin B1.

Polyethylene glycol (PEG) is used to separate the antibody-bound ligand from the free ligand in the radioimmunoassay of aflatoxin B1. Conditions affecting precipitation of the bound ligand are described. Maximal precipitation of antibody-bound aflatoxin B1 requires an aqueous PEG concentration of 15-20% and 0.4 mg of carrier gamma-globulin. Precipitation is unaffected by pH variations from 6 to 9, by NaCl concentrations below 0.28 M, and by Tris-HCl concentrations below 0.2 M. The radioimmunoassay procedure is simple, rapid, and sensitive and could be used to assay aflatoxin B1 in unextracted sera or in peanut butter after solvent extraction.