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 IC50 of 2.30 mu g/L with a detection limit of 0.20 mu g/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 Cd2+, Pb2+, Hg2+, Zn2+, Na+, Ca2+, Fe3+, Mg2+, Mn2+, Cu2+, Al3+, Co2+, Cr2+, Ni2+, 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.