A competitive dual-label time-resolved fluoroimmunoassay for the simultaneous determination of chloramphenicol and ractopamine in swine tissue

A novel dual-label time-resolved fluoroimmunoassay method was developed for the simultaneous determination of chloramphenicol (CAP) and ractopamine (RAC) residues in 18 swine tissue samples, using anti-CAP and anti-RAC monoclonal antibodies labeled with europium (Eu(3+)) and samarium (Sm(3+)), respectively. The detection limits for CAP and RAC were 0.06 and 0.25 ng/g. The recovery from swine muscle samples was 102%-121% for CAP at spiking levels of 0.1-5 ng/g, and 69.8%-85.8% for RAC at spiking levels of 1-10 ng/g. The results obtained from the swine tissue samples using this method showed good agreement with those obtained using ELISA and GC-MS, with correlation coefficients (R) between 0.92-0.98.