-Make sure all primary amine-containing buffer components of the buffer like Tris or glycine are completely removed by dialysis, desalting, or the use of the Pierce Antibody Clean-Up Kit (Cat. No. 44600) before coupling to magnetic beads
-Make sure the antibody is mixed with the NHS-beads IMMEDIATELY after washing the beads. A delay may cause hydrolysis of the NHS groups on the resin which leads to low coupling efficiency.
-Finally make sure the pH of the non-amine-containing coupling buffer used for coupling is between pH 7-9
Find additional tips, troubleshooting help, and resources within our Protein Assays and Analysis Support Center.