Characterization of mass transport processes in IMAC chromatography by dynamics methods

The characterization of mass transport processes in IMAC chromatography and the pH effect on the process have been done. To do that the adsorption equilibrium constant and adsorption rate constant for Cu, Zn-superoxide dismutase (Cu, Zn-SOD) on Cu-IDA-agarose matrix have been determined in batch and in a continuous operating systems (chromatographic column) by dynamic methods. The experiments were performed at pH of 7.00, 7.40 and 7.80 and, in case of chromatographic columns, flow rates of 1.56–2.66 ml/min. From the analysis of the experimental results it can be concluded that the controlling steps for the Cu, Zn-SOD adsorption on Cu(II)-IDA-agarose beads are both external and internal mass transfer processes, which was experimentally confirmed with the fact that the adsorption kinetic process is too fast. The medium pH affects equilibrium and mass transport parameters in the following way: a decrease in the medium pH towards the enzyme isoelectric point increases the adsorption equilibrium constant and both molecular and effective intraparticle diffusion coefficients; and decreases internal, external and global mass transfer resistances, and effective axial dispersion.