Development and validation of an immunochromatographic assay for rapid detection of sulfadiazine in eggs and chickens

A rapid immunochromatographic assay (ICA) was developed and validated for the detection of sulfadiazine in eggs and chickens. Based on the competitive reaction mechanism, the competitor of sulfadiazine (sulfadiazine-BSA conjugate) was immobilized to the defined detection zone on a nitrocellulose membrane which acted as the capture reagent, and the monoclonal antibody against sulfadiazine was conjugated to colloidal gold particles which served as the detection reagent for the preparation of the immunochromatographic strips to test sulfadiazine. With this method, the semi-quantitative detection of sulfadiazine was accomplished in less than 15min, with high sensitivity to sulfadiazine (5ng/g) and low cross-reactivities with other sulfonamides. With experimental egg and chicken samples spiked with sulfadiazine at concentrations of 10, 20, and 100ng/g, recoveries were demonstrated to be from 71% to 97% in egg samples and 71% to 95% in chicken samples. This method was compared with the enzyme-linked immunosorbent assay by testing 52 egg samples from the animal experiment, and compared with the high-performance liquid chromatographic method by testing 56 chicken samples, with an agreement rate of 100% for both comparisons, by using the maximum allowed residue of sulfadiazine (i.e. 100ng/g) as the cut-off level as set by the European Union and China. The accuracy of ICA was also confirmed in an initial study with marketed egg and chicken samples. In conclusion, the method is rapid and accurate for the detection of sulfadiazine in eggs and chickens.