Determination of the pore size distribution, by exclusion chromatography, of ion-exchange polymers which swell in water

Volume of Space within Cation-exchange Resins Determined by Penetration of Inorganic Salt Solutions

Penetration of salt solutions into cation exchange resins was used to measure the volume of a space within the resin phase (the inner space), which was usable for ion exchange in principle but not fully in practice. The average volume of the inner space per functional group was significantly dependent on the type and the concentration of the salt (250 - 450 ų) for a resin having the cross-linking degree of 8%, while being less dependent on the type and the concentration of the salt (160 - 240 ų) for a resin having the cross-linking degree of 12%. The salt concentration ratio of the solution filling the inner space to the outer solution decreased with a decrease in concentration of the outer salt solution due to the osmotic pressure, and decreased with an increase in cross-linking degree due to the smaller volume and the higher independency of the inner space.

Determination of pore size distributions of porous chromatographic adsorbents by inverse size-exclusion chromatography

The macroscopic properties of porous chromatographic adsorbents are directly influenced by the pore structure, with the pore size distribution (PSD) playing a major role beyond simply the mean pore size. Inverse size-exclusion chromatography (ISEC), a widely used chromatographic method for determining the PSD of porous media, provides more relevant information on liquid chromatographic materials in situ than traditional methods, such as gas sorption and mercury intrusion. The fundamentals and applications of ISEC in the characterization of the pore structure are reviewed. The description of the probe solutes and the pore space, as well as theoretical models for deriving the PSD from solute partitioning behavior, are discussed. Precautions to ensure integrity of the experiments are also outlined, including accounting for probe polydispersity and minimization of solute-adsorbent interactions. The results that emerge are necessarily model-dependent, but ISEC nonetheless represents a powerful and non-destructive source of quantitative pore structure information that can help to elucidate chromatographic performance observations covering both retention and rate aspects.