Evaluation of the Deacetylation Degree of Chitosan with Two‐Abrupt‐Change Coulometric Titration

The two‐abrupt‐change coulometric titration was proposed for the analysis of the degree of deacetylation of chitosan. The potential was indicated by an antimony electrode which could sensitively response to the variation of activity of hydrogen ion in the turbid and viscous chitosan solution. Through this new approach, the deficiency of combination pH glass electrode in that medium is successfully overcome. The degree of deacetylation of chitosan was obtained by the difference of electrolysis time between two inflection points in the electrolysis process. The measurement error, which is caused by the residual acid or alkali in the chitosan, could be eliminated. The degree of deacetylation of four chitosan samples were investigated by this new method, which found to be consist with those determined by proton nuclear magnetic resonance (¹H NMR). The standard deviations were found to be lower than 0.60 % and the whole experimental process can be completed within 15 min. With merit of simplicity, convenience, quickness, accuracy, the proposed new method would possess extensive practicability in scientific research and industrial production.