Comparative evaluation of the swelling and degrees of cross-linking in three organic gel packings for SEC through some geometric parameters

The size exclusion chromatographic (SEC) behavior of five solvent/polymer systems in three organic column packings based on polystyrene/divinylbenzene (PS/DVB) copolymer, TSK-Gel H HR, μ-styragel and TSK-Gel H XL, has been compared. All the packings offer similar characteristics (pore size, particle size and efficiency) but some differences have been found when eluting the same systems. The different elution behavior observed in both polymeric gels has been analyzed in terms of their swelling and cross-linking degrees and of the fractal parameters. From the Universal Calibration plots, values of the chromatographic partition coefficient, K p, have been obtained and using some equations previously reported, values of the volume fraction of the network in the swollen state have been determined for the three sets of columns. Overall, for a given hydrodynamic volume and solvent-polymeric solute system the fraction of cross-linked polymer in the stationary phase was ordered according to: TSK-Gel H XL>μ-styragel>TSK-Gel H HR. This means an enhanced swelling degree for TSK-Gel H HR. In general, fractal calculations support the thermodynamic predictions since both the fractal dimension and the pore size can be ordered as TSK-Gel H HR>μ-styragel>TSK-Gel H XL (in 10 of the 15 situations studied). The exceptions can be explained in terms of strong preferential solvation.