I want to do analytical tests regarding histidine in buffer systems. So if sulfate groups interact with histidine, please mention how I can avoid the problem.
I do not believe that Histidinyl side chain residues of proteins will react co-valently with the sulphate groups of HEPES and CHES buffers. However, there will be some Coulombic attraction of the negative ion to the positive side chain. I would suggest testing with and without added NaCl (or KCl).