Patent ID: 7534624

Claim:
An assay method in utilizing attenuated total reflection by use of at least one sensor unit and an optical assay unit, wherein said sensor unit includes a transparent dielectric medium, and thin film having a light entrance surface and a sensing surface reverse to said light entrance surface, said light entrance surface being an interface in connection with said dielectric medium, and said sensing surface causing interaction between ligand of ligand liquid and analyte liquid, wherein said optical assay unit applies illuminating light through said dielectric medium to said light entrance surface in such a form as to satisfy a condition of total reflection, and assays interaction between said ligand and said analyte liquid by detecting attenuation of said illuminating light reflected by said light entrance surface, said assay method comprising: wherein said sensor unit includes a flow channel block having a flow channel for causing said ligand liquid and said analyte liquid to flow to said sensing surface; a step of, in an immobilizing stage, immobilizing said ligand on said sensing surface by introducing said ligand liquid to said flow channel for a prescribed period of time; a step of introducing evaporation retardant to said flow channel, for preventing drying of said immobilized ligand; a step of removing said evaporation retardant from said flow channel after transfer of said sensor unit from said immobilizing stage to an assay stage; and a step of introducing said analyte liquid to said flow channel, to assay said interaction.