Electromigration of Chitosan d-Glucosamine and Oligomers in Dilute Aqueous Solutions

Abstract

The electromigration behavior of chitosan D-glucosamine and oligomers with a degree of polymerization from 1 to 6 in dilute aqueous systems containing either NaCl or KCl salt at 0.01, 0.05, and 0.1 M at pH values from 2 to 9 was evaluated. The results showed that the electromigration of the chitosan D-glucosamine and oligomers did not change by changing the type of salt in the running medium and that the pH had a significant effect on the direction of migration under an external electric field. In addition, the increase in the ionic strength of the medium caused a significant decrease on the absolute value of the electrophoretic mobility, and the highest values of the electromobility were observed in water. However, the ionic strength had no significant effect on the electrophoretic mobilities at pH 2 in comparison with the other pH values. The dimer showed the highest electrophoretic mobility in the alkaline zone of the pH. At pH values lower than the pKa of the D-glucosamine, the chitosan D-glucosamine, and oligomers migrated toward the anode, where the amine groups are protonated and carry positive charge. At higher pH values, chitosan D-glucosamine and oligomers migrated toward the anode, even though they did not carry any electric charge. The contribution of the difference in the dielectric constants between the solvent and the solute to this phenomenon was highlighted. It was shown that the glucose moiety contributes to the direction of migration of the chitosan D-glucosamine and oligomers under alkaline conditions and that the difference in the dielectric constant of glucose and the solvent accounts for the direction and the extent of electromobility.