Development of a McAb-based immunoassay for parathion and influence of the competitor structure

A specific monoclonal antibody (McAb) for parathion was produced. Based on this McAb, a battery of competitors as coating antigens were used to develop homologous and heterologous indirect competitive enzyme-linked immunosorbent assays (ELISAs) for parathion. The relationship between the heterology degree of the competitor and the sensitivity of the corresponding immunoassay was investigated. Results showed that, when the specific McAb was used in the ELISA experiment, competitors should have a certain degree of homology with the immunizing hapten for immunoassays, and the best performance occurred when the competitor hapten was highest heterologous to the target analyte. With the most suitable competitor, a sensitive and selective ELISA was developed. The IC₅₀ value of the ELISA was 2.94 ng/ml with a detection limit (IC₂₀) of 0.70 ng/ml. The average recoveries of parathion in spiked water, soil, cucumber and rice were 88.09%, 93.15%, 91.37% and 83.42%, respectively.