IMMUNOASSAY TECHNIQUES ARE METHODS that exploit immunological reactions to measure the presence of a substance. The first immunoassay, a radioimmunoassay (RIA) for insulin, was described by Yalow and Berson (1959); thereafter, radiolabels were replaced by enzymes in enzyme immunoassays (EIAs) by Engvall and Perlmann (1971) and Van Weemun and Schuurs (1971). Enzyme immunoassays are widely used in nonclinical fields; radioimmunoassays are seldom used in food analysis, to some extent because of the short half-life of many radioactive materials, which require special handling and disposal, but most often because the presence of radioisotopes in a food processing environment is unsuitable.
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