First calculate the amount of ligand to be immobilized based on the relative size differences between ligand and analyte.
I assume you use the amine coupling on a dextran chip.
Then use a pre-concentration experiment to determine the correct pH and ligand concentration to get a pre-concentration rate between 15 – 40 RU/s. Use a report point during the pre-concentration to determine the slope in RU/s. www.sprpages.nl/immobilization/ligand-pre-concentration
The actual ligand concentration is not of real importance as long as the pre-concentration is fast enough for the desired immobilization target. We use normally a maximum of 100 µl ligand solution (5 – 20 µg/ml) to immobilize between 200 – 5000 RU ligand (5000 – 160000 Da).