The present invention relates to methods for measuring an amount of an analyte using an electrochemical assay in a conduit comprising a sensor, wherein said sensor comprises an electrode having a surface layer of immobilized antibody that binds said analyte, and a counter/reference electrode disposed within said conduit. A solution comprising a substrate for said enzyme and at least one air segment contacts the sensor to remove unbound analyte and labeled antibody from a region of the sensor. The disclosed invention is adaptable to the point-of-care clinical diagnostic field, including use in accident sites, emergency rooms, surgery, nursing homes, intensive care units, and non-medical environments.