Field-Flow Fractionation of Cationic Cellulose Derivatives

Abstract

The asymmetric flow field-flow fractionation (AF4) method was developed for cationic cellulose derivatives. AF4 is the method of choice especially for high-molar mass samples, which are challenging to characterize with conventional chromatographic techniques such as size-exclusion chromatography (SEC). The cationic charge of macromolecules also complicates the size-based separations where no interaction between the analytes and the column stationary phase (SEC) or membrane (AF4) should occur. However, many column matrices and membranes carry negative charge and thus preventing interactions between cationic analytes and negatively charged separation support should be taken into consideration when doing method development. In this study, two eluent compositions, neutral and acidic, were tested for AF4 separation of cationic hydroxyethyl celluloses with varying charge densities. The eluent composition with a pH below the isoelectric point of regenerated cellulose membrane, which was used in this AF4 study, enabled the size-based separation with close to 100% analysis recovery. Macromolecular parameters (molar mass and radius of gyration) and conformation were investigated by coupling a multi-angle light scattering detector and differential refractometer to the AF4 system.

Nanoengineering the Redispersibility of Cellulose Nanocrystals

“…In this experiment, the redispersibility was calculated to be 79 ± 5%, and again, no aggregates were visually observed, suggesting that AHCNC may be partially lost (15-20%) due to the Ca 2+ -mediated binding to the negatively charged surface of regenerated cellulose dialysis membranes used to purify the dispersions. Previous studies on the separation of cationic cellulose derivatives have shown that the surface of regenerated cellulose membrane is negatively charged at neutral pH, reducing the sample recovery, likely as a result of unwanted interactions of charged cellulose with the membrane; however, the recovery improves at acidic pH when the membrane carries weak positive charges . Between 10 and 100 mM of Ca 2+ , when the theoretical charge neutralization is reached, there is a statistically significant decrease in the AHCNC redispersibility to 35 ± 2%, agreeing with the visual observations.…”

“…Previous studies on the separation of cationic cellulose derivatives have shown that the surface of regenerated cellulose membrane is negatively charged at neutral pH, reducing the sample recovery, likely as a result of unwanted interactions of charged cellulose with the membrane; however, the recovery improves at acidic pH when the membrane carries weak positive charges. 68 Between 10 and 100 mM of Ca 2+ , when the theoretical charge neutralization is reached, there is a statistically significant decrease in the AHCNC redispersibility to 35 ± 2%, agreeing with the visual observations. At all concentrations of CaCl 2 , the redispersibility of AHCNC is significantly higher than that of conventional CNC.…”

Marine Exopolysaccharide Complexed With Scandium Aimed as Theranostic Agents

“…Many commonly used SEC stationary phases may contribute to the unwanted interactions between charged analytes and column material. Another limitation of SEC is the incapability of the technique to characterize high-molar mass polymers and polysaccharides accurately (M w > 1 × 10 6 g mol −1 ), even if SEC has been successfully used for characterization of commercial cationic hydroxyethyl cellulose derivatives [ 52 ]. Additionally, it has been well established that the potential for degradation exists when analyzing long linear polymers by SEC [ 53 ].…”

Investigating the Impact of Hydrophobic Polymer Segments on the Self-Assembly Behavior of Supramolecular Cyclic Peptide Systems via Asymmetric-Flow Field Flow Fractionation

“…All samples were measured at room temperature in an aqueous solution consisting of 0.1 M sodium chloride (NaCl) and 0.02% sodium azide (NaN 3 ) (Table ). NaN 3 was added to prevent bacterial contamination while the NaCl was added as a standard AF 4 practice to minimize nonspecific electrostatic interactions between any charged analytes and the AF 4 regenerated cellulose membrane which carries a weak negative net charge at neutral pH. − This is achieved because of the charge screening effects of the Na + and Cl – ions. An additional benefit of the NaCl salt concentration is that it is representative of physiological cell environments (Na + : 0.103 M and Cl – : 0.142 M) …”