Dual-label quantum dot-based immunoassay for simultaneous determination of Carbadox and Olaquindox metabolites in animal tissues

A novel and reliable dual-label direct competitive fluorescence-linked immunosorbent assay (dc-FLISA) based on quantum dots (QDs) was developed for the simultaneous determination of the major metabolites of Carbadox and Olaquindox residues in animal tissues, using anti-QCA monoclonal antibodies and anti-MQCA polyclonal antibodies labeled with QD520 and QD635, respectively. The limits of detection for QCA and MQCA were 0.05 and 0.07 ng/ml, respectively. The method was used to analyze fortified samples and analyte recoveries ranged from 81.5% to 98.2% (QCA) and 84.2% to 95.7% (MQCA). Good correlations between the dc-FLISA method and HPLC were demonstrated for the determination of QCA and MQCA residues in swine tissue samples, confirming the reliability of the proposed method.