Column chromatography specific binding assay method and test kit

A specific binding assay method and test kit for determining a ligand, such as an antigen or antibody, in, or the ligand binding capacity of, a liquid medium, particularly a body fluid such as serum, wherein the unknown ligand competes with a labeled component, such as a radio labeled form of the ligand or of a binding analog of the ligand, for binding with a binding partner, with the improvement that separation of the resulting bound-species and free-species of the labeled component is accomplished by drawing the liquid reaction mixture into a column of an adsorbent material selective for one of the two species. Separation results by immobilization of the selected species at the beginning portion of the adsorbent column while the other species is transported farther along the column by advance of the reaction mixture. The present method is manipulatively simple and advantageous over the many known techniques; finds special application to radioimmunoassay, particularly for detecting low molecular weight ligands; and is readily adaptable to automation.