Objective To test ractopamine with the method of time-resolved fluoroimmunoassay(TRFIA) for the determination of.Methods RAC-BSA was coated by physical adsorption onto a 96 well microtitre plate,which was then competed with RAC in the sample for limited quantity of anti-RAC antibody labeled by Eu3+.Ractopamine in urine could be determined by direct competition method.Results The assay sensitivity of the method was 0.01ng/ml.The correlation coefficient of dose-response curve was 0.998 5.The recov...