Chromatographic Characterization of Immobilized Metal Ion Hollow-Fiber Affinity Membranes Obtained by Direct Grafting

Iminodiacetic acid was immobilized onto membranes with different grafting degrees by reaction in phosphate buffer or water/dimethyl sulfoxide. Membranes subjected to conversion in water/dimethyl sulfoxide underwent greater conversion than those modified in phosphate buffer, despite their grafting degree. Copper saturation capacity increased consistently with the grafting degree and histidine saturation capacity was approximately half than that of copper. When working with proteins, membrane behavior was related to the molecular weight of the protein tested. Accessible sites for lysozyme decreased with the increase in the grafting degree and the rise in the conversion of epoxy groups in iminodiacetic groups in water/dimethyl sulfoxide while they remained practically unchanged when the conversion step was performed in phosphate buffer. When working with hemoglobin, this effect was the same but at lower capacities. For hollow fibres with 60 and 75% grafting, capacities were the same despite the conversion reaction solvent.