Swelling of dextran gel and osmotic pressure of soluble dextran in the presence of salts

Abstract

The swelling of dextran gels (Sephadex) in salt solutions with a water activity of 0.937, compared with the swelling in pure water, exhibited anion specificity as evidenced by an increased swelling ratio in the following order: Na 2 SO 4 Ͻ H 2 O Ͻ NaCl Ͻ NaSCN. The swelling ratio showed a good linear correlation with the osmotic pressure of dextran (500 kD) in these solutions. The salt-concentration difference (imbalance) between the polymer-solution side of the membrane and the polymer-free permeate side during the osmotic-pressure measurements positively correlated with the effect of the salt on the polymer osmotic pressure. These phenomena conform to Hofmeister-type (or lyotropic) behavior. The diminishing augmentation of dextran osmotic pressure and the change in the salt-concentration imbalance with rising NaSCN concentration imply a positive preferential interaction and adsorption of the salt onto the polymer.

High ionic strength narrows the population of sites participating in protein ion-exchange adsorption: A single-molecule study

“…Ion-exchange adsorbents can undergo structural changes with changes in ionic strength as inter-charge electrostatic repulsion is more or less well screened [52-55]. There also can be direct effects of salt on the structure of agarose itself [56].…”

Spoliation of a rigid gas permeable contact lens by sodium chloride: A free volume microprobe study

“…The adhesion results to increased osmotic pressure and hence faster mass uptake. This can be explained as follows: The difference in the behavior of different ions in aqueous solutions is related to their surface charge densities [5,6]. According to Collin [5], ions of low charge density adsorb onto hydrophilic sites of the polymer by releasing the weakly bound hydration shell water molecules, both their own and those of the polymer, allowing them to form more favorable bulk water.…”

“…Hence these are more probable sites for the adhesion of sodium (Na + ) and chloride (Cl -)ions. Relatively large, low charge density ions such as Na + and Cl -, increase the osmotic pressure and demonstrate a positive excess because they are pushed toward the polymer by the water molecules, which energetically favor the bulk water structures [6].…”

Modulating the properties of sunflower oil based novel emulgels using castor oil fatty acid ester: Prospects for topical antimicrobial drug delivery

“…These interactions have been reported to cause the shrinkage of the emulgels by counteracting the osmotic pressure [32]. The shrinkage effect of the emulgels is often associated with a decrease in the osmotic pressure as this is a major driving force for the swelling of the emulgels [33,34]. Since metronidazole is an aqueous soluble drug, controlling the release rate of the drug is a challenge.…”