Effect of pH and cell configuration on the selective and specific electrodialytic separation of chitosan oligomers

Interest in chitosan oligomers of low molecular weights is growing fast because of their potential use as bioactive ingredients. In the present study, the effect of pH and electrodialysis with ultrafiltration membrane (EDUF) cell configuration was studied on electromigration of chitosan oligomers (dimer, trimer and tetramer) to demonstrate the potential selective and specific separation of the three oligomers from each others. It was shown that cell configuration influenced the possibility of separation of the oligomers since oligomer migration and separation was observed only in configuration 1 (anode–AEM1–UFM–AEM2–cathode). Furthermore, chitosan oligomer electromigration decreased by increasing the pH of the medium. Hence, the dimer showed the highest electromigration rate at all pH values, followed by trimer, and then by tetramer. It was shown that it was possible to separate dimer mixed with trimer at pH 6 or only the dimer at pH 7 according to the processing time. There was no electromigration at pH 8 and 9. Up to now, only analytical methods were known to separate dimer, trimer and tetramer. Consequently, it was a real challenge to separate, on a potential large-scale technology such as EDUF, the dimer from the trimer and tetramer since they have very close molecular weights.