Simultaneous detection of sulfamethazine and sulfaquinoxaline using a dual-label time-resolved fluorescence immunoassay.

A dual-label time-resolved fluoroimmunoassay (TRFIA) was introduced for the simultaneous quantification of sulfamethazine (SM2) and sulfaquinoxaline (SQX). Lanthanide (Eu(3+) and Sm(3+))-labelled antibodies were used because lanthanides have higher stabilities and narrower emission spectra than most fluorescent dyes. The sensitivity of the TRFIA for SM2 was 0.02 ng ml(-1), and the average recoveries and the intra- and inter-assay CVs were 77.2-107.6%, 5.4-10.5%, and 6.0-11.2%, respectively. The sensitivity of the TRFIA for SQX was 0.04 ng ml(-1); and the average recoveries and the intra- and inter-assay CVs were 74.1-102.8%, 4.6-10.9%, and 8.7-11.2%, respectively. The method was used to analyse chicken tissue and egg samples, and the results agreed well with the results of HPLC and enzyme-linked immunosorbent assay (ELISA) analyses, with correlation coefficients (R(2)) of 0.9415-0.9724. The TRFIA developed is a simple, fast and sensitive method for the high-throughput simultaneous screening of SM2 and SQX in edible animal tissues.