| abstract |
An immunoassay, e.g. ELISA, method and kit for determining (preferably quantitatively) an analyte adsorbed at a surface or present in a liquid sample, comprising binding said analyte to a solid phase, attaching a marker to the analyte, and detecting marker attached to said solid-phase. The invention proposes to use a combination of marker and detection means (e.g. an enzyme-substrate combination) which is capable of producing a precipitate on solid phase which carries the marker and to detect the binding of analyte to the solid phase by in-situ determining the change of surface mass of said solid phase due to the formation of said precipitate. Ellipsometry is an example of a technique suitable for determining the change of surface mass of the solid phase, which could be made of a silicon- or chromium-sputtered glass slide. The invention shortens the assay time and/or improves the assay sensitivity, and allows to measure extremely low surface concentrations of analytes of interest. |