immunochromatographic assay for simultaneous and quantitative detection of 3-methyl-quinoxaline-2-carboxylic acid and quinoxaline-2-carboxylic acid residues in animal tissues based on highly luminescent quantum dot beads

Due to their potential adverse effects on human health, the use of carbadox and olaquindox in feedingstuffs was prohibited by the european union since 1998. in this work, highly luminescent quantum dot beads (qbs) were synthesized by encapsulating cdse/zns and used as novel fluorescent probes in the immunochromatographic assay (ica) for simultaneous and quantitative determination of metabolites of olaquindox (3-methylquinoxaline-2-carboxylic acid, mqca) and carbadox (quinoxaline-2-carboxylic, qca). the fluorescence intensities of the test lines were recorded using a fluorescence strip reader. the 50% of inhibition for mqca and qca was shown to be 8.1 and 10.6 μg l−1, respectively. the whole assay process can be accomplished within 10 min. the immunosensor was used to analyze spiked samples, and analyte intra- and inter-assay recovery rates ranged from 78.7 to 92.2% for mqca and 80.6 to 95.8% for qca, and coefficients of variation were all below 12%. the incurred tissues samples were assayed using both qb-based ica and commercial elisa kit and were further confirmed with lc-ms/ms. the qb-based ica results exhibited good agreement with both commercial elisa and lc-ms/ms methods.