I use magnetic beads and after antibody binding I add 150uL of 5mM BS3 in conjugation buffer (20mM sodium phosphate, 150mM NaCl, pH=7-9) for 30 min rotating, then quench it with 12,5uL 1M Tris pH=7,5 for 15 min rotating again and finally I wash 3 times with SPT (0,1M sodium phosphate pH=8,2+ 0,01% Tween20) and 3 times with conjugation buffer. It works fine

Thanks, I had't thought of using magnetic beads, but that might be really useful. I used a protocol similar to what worked for DSS. I'll find out soon if it worked. I didn't see your response before attempting, so if it doesn't work, I'll try your method, Thanks!

Steve