SOLUTION PROPERTIES OF POLYELECTROLYTES .9. QUANTITATIVE DEPENDENCE ON ELUENT IONIC-STRENGTH OF ELUTION VOLUMES IN AQUEOUS SIZE-EXCLUSION CHROMATOGRAPHY

Quantitative evaluation of elution volumes (V-e) of polyelectrolytes in salt-containing eluents was performed, taking into account electric double-layer effects and the effective radius of polyions, and assuming that polyelectrolytes behave as rigid hydrodynamic spheres and that the geometry of gel pores is cylindrical. A polynomial V-e dependence on ionic strength (I) was obtained, namely a second order one in I--1/2. The semi-empirical polynomial coefficients depend on column characteristics, namely V-0 (interstitial volume), V-p (total pore volume) and alpha (mean pore radius), as well as on effective coil radius (R eta) and on k (a parameter related to the electric effects). Fair correlations between predicted and measured elution volumes for uncharged polymers hold, at least for the polyelectrolyte-gel systems tested here: polyelectrolytes poly(L-glutamic acid), sodium poly(styrene sulphonate) and poly(acrylic acid); gels Spherogel TSK PW4000 and Ultrahydrogel 250.