Patent ID: 7715012

Claim:
A sensor unit for assay in utilizing attenuated total reflection, including a transparent dielectric medium, a thin film having a first surface and a sensing surface, said first surface being connected with said dielectric medium to constitute an interface, said sensing surface being back to said first surface, for detecting reaction of a sample, and a flow cell block having a flow channel for flowing of said sample to said sensing surface, wherein illuminating light is applied through said dielectric medium to said interface to satisfy a total reflection condition, and a reflection angle upon occurrence of said attenuated total reflection of said illuminating light changes according to reaction of said sample on said sensing surface, said sensor unit comprising: wherein said flow channel comprises a facing portion, disposed opposite to said sensing surface to extend along, for passing said sample to flow between, an inner surface of said facing portion having a height, defined with reference to said sensing surface, and equal to or more than 200 microns, and equal to or less than 500 microns; wherein an analyte fluid is introduced into said channel in which an buffer fluid is filled in assaying a reaction of binding of said sample, so as to substitute said analyte fluid for said buffer fluid in said flow channel; wherein introducing of said analyte fluid is stopped while said reaction of binding is assayed.