Abstract: A system and method wherein components of a reagent such as labeled antibodies are separated from a biologically active sensor surface by depositing the reagent on a carrier surface distinct from a sensor surface in a detection region. The present device provides a short, well-defined and controlled, pre-incubation time between the particles of interest in the sample fluid and the reagent, thereby increasing the reproducibility by providing all components in one detection region such as a detection chamber.

Abstract: A system and method is described wherein components of the reagent (4), e.g. labelled antibodies, are separated from the biologically active sensor surface (5) by depositing the reagent (4) on a carrier surface (3) distinct from the sensor surface (5) in the detection region (2), e.g. detection chamber. In this way, a high assay reproducibility is obtained. By allowing a short, well-defined and controlled, pre-incubation time between the particles of interest, e.g. drugs, in the sample fluid (20) and the reagent (4), the reproducibility will be increased, whereas the speed of the assay is guaranteed by having all components in one detection region (2), e.g. detection chamber.