Steric Mass Action Isotherms for Ion Exchange Equilibria

4 Steric Mass Action Isotherms for Ion Exchange Equilibria 

The state of equilibrium in ion exchange chromatography is currently described by stoichiometric models where the solute, for example a protein, displaces a stoichiometric number of salt ions bound on the ion exchanger. A basic concept is the stoichiometric displacement model developed by Kopaciewicz et al. (1983). For monovalent counterions the reaction is described as follows  

For dilute protein solutions or at high salt concentration the protein load is very small so that 

Brooks and Cramer (1992) recommend experimental procedures such as using iso-cratic/gradient elution chromatography to determine the parameters Ku,i, f , and Oj. SMA isotherms do not take into account an influence of the pH value. Corresponding extensions have been developed by Gerstner, Bell, and Cramer (1994) and Bosma and Wesselingh (1998). 

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