SOLUTION PROPERTIES OF POLYELECTROLYTES .10. INFLUENCE OF IONIC-STRENGTH ON THE SECONDARY EFFECTS IN AQUEOUS SIZE-EXCLUSION CHROMATOGRAPHY

The retention behaviour of polyelectrolytes in aqueous size-exclusion chromatography (SEC), where electrostatic repulsion is the main secondary effect affecting to the separation mechanism, was investigated. A theoretical treatment was developed in order to establish the influence of the mobile phase ionic strength on calibration graphs, often used for the characterization of polyions by SEC. A master equation, derived in closed form, involving two terms related to the net charge of polyion and the residual surface charge on the gel packing, was derived. The formalism provides the basis for a more detailed analysis of chromatographic retention data in electrostatic interaction systems. Moreover, the introduction of some approximations in the original equation served to obtain an equivalent expression that is easier to use, and in which the functionality with respect to the ionic strength, T, remains unaltered. Reported data on the elution of sodium polystyrene sulphonate and poly(L-glutamic acid) from both organic and silica-based packings were used to test the goodness of the predictions carried out with the above mentioned equations.