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Abstract
This paper reports the preparation of polyclonal antibodies against a synthetic azo dye, Orange II, and the development of an indirect ELISA to detect Orange II in foods. The sulfonic group of Orange II was modified and linked with carrier protein to synthesise an artificial antigen. Based on the checkerboard titration, the method showed excellent sensitivity (IC50 = 0.61 ng g−1) to Orange II in the linear range of 0.05–10 ng g−1. The antibody had little cross-reactivity with Chromotrope FB, Gardenia Yellow, Ponceau 4R, Sunset Yellow and Sudan dyes. The ELISA had limits of detection (LOD) of 0.22, 0.97 and 0.74 ng g−1 in chilli powder, chilli oil and braised pork, respectively. The limits of quantification (LOQ) of the assay were 0.91 ng g−1 in chilli powder, 1.48 ng g−1 in chilli oil and 1.10 ng g−1 in braised pork. For food products fortified with 1–10 ng g−1 Orange II, the inter- and intra-assay variations were all less than 24.0% and 18.0%, respectively. Therefore, the proposed test could be used as a rapid screening method for Orange II detection in food samples.
Acknowledgements
The authors are thankful for the financial support from the National Natural Science Foundation (Grant Numbers 81173017 and 31101277), the National High-Tech Research and Development Program of China (863 Program, Numbers 2010AA10Z402 and 2007AA06A407), the Tianjin Science and Technology Program (Grant Number 09ZCKFSH07500), the Scientists–Company Cooperation Project of the Ministry of Science and Technology of China (Grant Number SQ2009GJA0002591), and the Fundamental Research Funds for the Central Universities (Grant Number 65011121).
