I have been trying to couple the aqueous polymer with a COONa group at the terminal position with microsized particle having a lot of amine (-NH2) on its surface. I used aqueous media. I took the polymer having -COONa in water, dissolved it then added EDC. After 5 minute added Sulfo-NHS and then stirred for 30 min. Thereafter, added the NH2-microparticles (aqueous dispersion) and stirrred for 2 h. Thereafter, washed it by water through centrifugation. I am not able to identify the amide bond via FTIR/NMR which should be formed through this reaction. I tried ninhydrin test also, but it seem both amine and amide are respondin to this test. Please comment on the coupling procedure and/or the characterization procedure, too. Thank you in advance.