Desalting of chitin derivatives by the electrodialysis via ion-exchange membranes

Using an electrodialysis technique, chitin derivatives in aqueous solutions containing various salts were desalted. The anodic cell (Part A: 0.1 mol/d m(3) KOH, 95 ml) and the cathodic cell (Part C: 0.1 mol/dm(3) HCl, 95 ml) w ere separated from the sample cell (Part O: 95 ml) by an anion-exchange mem brane and a cation-exchange membrane,, respectively. The potential between the electrodes was regulated to 10 V (free current). Because N-acetylation of chitosan and N-deacetylation of chitin were respectively performed under acidic and strongly basic conditions unless enzymatic methods were not emp loyed, neutralization in workup produced considerable amount of salt. There fore, chitin derivatives such as partially deacetylated chitin (DAC) and pa rtially acetylated chitosan (PAC) were sometimes contaminated with various salts. Aqueous solutions of PAC and carboxymethylated DAC containing NaCl, AcONa or AcOH were desalted by the electrodialysis. In the case of the susp ension containing AcONa and gels produced by N-acetylation reaction of chit osan with Ac2O in aqueous AcOH/MeOH, the electrodialysis of the sample susp ension eliminated AcONa inefficiently. This problem was solved by the treat ment of the sample suspension with a homogenizer for 1 or 2 min before the electrodialysis. Since chitin and its derivatives have received growing att ention as biologically active substances, the electrodialysis method provid es a convenient way for the preparation of salt-free samples of chitin deri vatives. (C) 1999 John Wiley & Sons, Ltd.