Immunoassay for lead ions: analysis of spiked food samples.

A rapid, simple, and reliable competitive immunoassay was developed for measurement of lead ions in spiked food samples. Avian antibodies were produced against Pb(II). Since lead ions are too small to elicit an immune response, the metal was coupled to protein carrier Bovine Serum Albumin (BSA) using a bifunctional chelator 1-(4-isothiocyanobenzyl) ethylenediamine N,N,N',N'-tetraacetic acid (ITCBE). Poultry birds (layers) were immunized with this Pb(II)-ITCBE-BSA immunoconjugate and avian antibodies (IgY) were isolated from egg yolk. This avian antibody (IgY) produced recognized Pb(II)-ITCBE complexes as capture reagent. The assay depended on a competitive binding reaction between the antibody and Pb(II). Antibody reaction was optimized for different concentrations of antigen and antibody dilutions. Cross reactivity with other metals were below 1% in competitive ELISA. The detection range and the detection limit were 0.02-1000 mg · kg⁻¹ and 0.2 mg · kg⁻¹, respectively. Spike recovery studies in different food samples showed that the avian antibodies could recognize Pb(II) in food samples without much matrix effect.