A competitive dual-label time-resolved fluoroimmunoassay for the simultaneous detection of chlortetracycline and doxycycline in animal edible tissues

A dual-label time-resolved fluoroimmunoassay (TRFIA) was introduced for the simultaneous quantification of chlortetracycline (CTC) and doxycycline (DOX) in edible animal tissues. Europium- and samarium-labelled antibodies were used, because lanthanides have higher stabilities and narrower emission spectra than most fluorescent dyes. The limits of detection for simultaneous determination of CTC and DOX were 0.03 ng ml(-1) and 0.04 ng ml(-1), respectively. The average recoveries and the intra- and inter-assay coefficients of variation were 85.8-102.4%, 4.3-8.4% and 5.5-8.9%, respectively, and 85.3-101.6%, 4.5-9.2% and 5.3-9.6% for DOX, respectively. The proposed TRFIA for spiked samples was confirmed by high-performance liquid chromatography with a high correlation coefficient (R-2) of 0.9933-0.9969. Therefore, the TRFIA may be an alternative sensitive and fast quantitative method for the high-throughput simultaneous screening of CTC or DOX in edible animal tissues.