TSKgel BioAssist Chelate is the PEEK format of the TSKgel Chelate-5PW column. This column is based on a 100 nm (1000 Å) pore size polymethacrylate base material covalently bonded with iminodiacetic acid (IDA) groups. Prior to chromatography, a metal ion, such as Zn2+, Ni2+ or Cu2+, is added to form a chelate with the IDA group. Peptides and proteins containing histidine residues will normally adsorb to these chelated ions at neutral pH. The retained compounds can be eluted with buffer containing imidazole or glycine.