Capture antibodies are pre-coated in the wells of premium Nunc MaxiSorp™ modular microplates, which can be broken into 8-well strips. After the target has been immobilized in the well, a second monoclonal antibody, against a different epitope on the target, is added to the well. This detector antibody is either directly labeled with biotin, or a biotin-labeled goat anti-mouse secondary is added. Substrate plus HRP or AP conjugated to streptavidin provide a colorimetric signal that is readable by any plate readers capable of standard ELISA absorbance measurements.