Development of direct competitive enzyme-linked immunosorbent assay for the determination cadmium residue in farm produce.
Cadmium, a toxic heavy metal, poses a significant threat to human health. Currently, the methods for detecting cadmium residue in farm produce need expensive equipment, intensive labor, and much time to finish one detection. In this study, a direct competitive enzyme-linked immunosorbent assay (DC-ELISA) based on a cadmium-chelate-specific monoclonal antibody has been developed. The DC-ELISA showed an IC(50) of 2.30 microg/L with a detection limit of 0.20 microg/L for cadmium. The assay has been demonstrated to be highly specific since the monoclonal antibody showed little or no cross-reactivity with all tested metal chelates which include Cd(2+), Pb(2+), Hg(2+), Zn(2+), Na(+), Ca(2+), Fe(3+), Mg(2+), Mn(2+), Cu(2+), Al(3+), Co(2+), Cr(2+), Ni(2+), Sn(2), and K(+). The assay showed that a mean recovery ranged from 100.47% to 103.86%, and the coefficients of variations for intra- and inter-assay were 1.73-7.14% and 3.63-6.81%, respectively. Then, several farm produces including wheat flour, apple juice, rice flour, and tea were analyzed for cadmium residue with DC-ELISA and graphite furnace atomic absorption spectroscopy (GFAAS). The correlation coefficient between the DC-ELISA and GFAAS was 0.99. It was demonstrated that the DC-ELISA can be used as a simple and economic method to detect and quantitate cadmium residue in farm produce.