Flow Immunoassay Based on Sequential Injection Using Microbeads

A flow immunoassay based on a combined technique of the sequential injection with the beads injection using magnetic microbeads immobilized with antigen or antibody is described. A methodology of the present immunoassay based on chemiluminescence and electrochemical detection and its application to the determination of vitelloginin (Vg) and anionic surfactant, linear alkylbenzene sulfonate (LAS) are described. Magnetic microbeads coated with agarose gel and polylactic acid were used for immobilization of an anti-Vg antibody and an anti-LAS antibody or Vg by a conventional amino coupling method. The introduction, trapping and flushing out of the magnetic microbeads in the immunoreaction cell were controlled by the magnet and the flow of the carrier solution. The protocol of the immunoassay in the immunoreaction cell, introduction of an analyte sample, the enzyme-labeled secondary antibody or antigen and a substrate solution for chemiluminescence or electrochemical detection were sequentially carried out by the sequential injection technique. A lower detection limit around ppb level was achieved for immunoassay for Vg and LAS. The time required for an analysis was ca 15 min/sample including incubation time for immunoreaction.