I ran my samples from 20-200 uM However, I got two spikes(I can term it peaks)before association and after dissociation. I am not sure whether the fit is good or not. SPR machine details: Reichert Tech.
I think you cannot make a valid fit with these kind of peaks. Probably something went wrong with the injection or data processing.
You can check the injection system with just one injection with buffer. The curves should be flat, if not, clean the system.