In various embodiments the present invention comprises 2,4,6-trisubstituted-1,3,5-triazine capping agents comprising one, two, or three leaving groups as substituents with any remaining substituents being essentially inert to reaction with a nucleophilic group on a polymer or monomer, or reactive with a nucleophilic group on a polymer or monomer at a slower rate than any leaving group. The first and second migration paths have first and second lengths chosen so that ligand in the sample reaches the test site and binds to the immobilized ligand-binding mechanism prior to the conjugate reaching the test site. A plurality of connecting bars are extended from the first enclosure; and the second enclosure is formed with a plurality of connecting holes.