Production of the monoclonal antibody against Sudan 2 for immunoassay of Sudan dyes in egg.

Many methods have been reported to determine the residues of Sudan dyes in food samples. Among the reported methods, enzyme-linked immunosorbent assay (ELISA) was a frequently used practical screen tool. In this study, a novel hapten of Sudan 2 was synthesized by coupling 4-amino-3-methylbenzoic acid to ß-naphthol, and the monoclonal antibody against Sudan 2 was produced. The obtained antibody can recognize Sudan 1, 2, 3, and 4, Sudan red G, and Para red simultaneously. After evaluation of different coating antigens, a heterologous indirect competitive ELISA was then developed to determine the six Sudan dyes in egg. The cross-reactivities for the six analytes were in a range of 63% to 100%, and the limits of detection were in a range of 0.2 to 0.5 ng/g, depending on the compound. Intra- and interassay recoveries from the standard fortified blank eggs were in a range of 71.7% to 97.6% with coefficients of variation lower than 17.1%.

Broad specificity indirect competitive immunoassay for determination of nitrofurans in animal feeds.

A generic hapten of nitrofurans was synthesized by derivatization of 5-nitrofurfural with diamine, and the hapten was coupled to carrier protein to prepare different immunogens and coating antigens by using diazotization method and glutaraldehyde method. The obtained novel polyclonal antibodies from immunized rabbits showed broad cross reactivity among seven nitrofurans. After assessment of four coating antigen/antibody combinations, an indirect competitive immunoassay was developed to simultaneously detect the seven nitrofurans in animal feeds. The limits of detection for these analytes were in the range of 5-16 µg kg(-1) depending on the compound. Recoveries from nitrofurans fortified blank feeds at levels of 30 and 100 ng g(-1) were in a range of 82.6-108.4% with coefficients of variation lower than 11.4%. The immunoassay was further validated by a HPLC method and the two methods showed good correlation (r=0.9924). Therefore, the proposed immunoassay could be used as a practical method to monitor the illicit use of nitrofurans in animal feeds.