LAUSR

A competitive time-resolved fluoroimmunoassay (TRFIA) using a biotin–streptavidin system was developed for the detection and quantification of the furaltadone metabolite 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ) in aquatic tissues. AMOZ-bovine serum albumin was coated to a solid phase and then competed with a free nitrophenyl derivative of AMOZ (2-NP-AMOZ) in standards or samples for binding with biotin-anti-AMOZ-ovalbumin polyantibody. Later, the complex was recognized by europium-labelled streptavidin, which was used as a novel tracer to amplify the signal, and it also reacted faster than europium-labelled second antibody in traditional TRFIA. After optimizing the reaction conditions, the method showed high sensitivity and specification to 2-NP-AMOZ with a half maximal inhibitory concentration of 0.190 μg/l and a sensitivity of 0.019 μg/l with a working range from 0.025 to 10 μg/l. The data from fish and shrimp samples indicated that the limit of detection was 0.021 μg/kg, and the recovery rates were 84.1–107.0% and 80.9–98.4%, respectively, with an average RSD below 10%. High correlation rates were observed in TRFIA, high performance liquid chromatography and universal enzyme-linked immunosorbent assay methods. The experiment above confirms that biotin–streptavidin-amplified TRFIA could be an ultrasensitive and accurate tool for screening large numbers of aquatic products for the determination of AMOZ residues.