[Fluoroimmunoassay and Magnetic Lateral Flow Immunoassay for the Detection of Ractopamine]

A fluoroimmunoassay based on quantum dots (QDs) and a lateral flow immunoassay system based on the magnetic beads (MB) were constructed to detect ractopamine (RAG) in urine samples. The monoclonal antibody (Ab1) against RAC was conjugated with QDs or MB as detector reagent, respectively. They apply a competitive format using an immobilized RAC conjugate and free RAC present in samples. That is to say, the concentration of RAC in the sample was negative related to the fluorescense intensity of QDs or the color density of MB. Results showed that the limit of detection (LOD) of fluorescence immunoassay method is 1 ng · mL⁻¹ and analysis time is 4 h, while the visual LOD was 10 ng · mL⁻¹ and analysis time was 15 min in magnetic lateral flow immunoassay system (MFLIS). Taken into consideration of the advantages and disadvantages of the two methods, it was suitable for the trace detection of RAC using fluoroimmunoassay while it was appropriate for point-of-care tesing of RAC by MFLIS.