IONIC STRENGTH DEPENDENCE OF PROTEIN RETENTION ON SUPEROSE-12 IN SEC-IEC MIXED-MODE CHROMATOGRAPHY

Protein retention was studied on Superose 12 in SEC-IEC mixed mode, over a wide range of ionic strength (16.8 mM to 500 mM). A new SEC parameter, K-int, which is analogous to the capacity factor k' in IEC was defined. The effect of ionic strength on K-int was compared to predictions from two previous models, that of Kopaciewicz et al. [1] and that of Stahlberg et al. [2]. The ionic strength dependence of K-int more closely fits the second model, and the stationary phase surface charge density calculated from the model agrees well with the experimental value.