Study the Methods on Determination of the Degree of Deacetylation of Chitosan
|Keywords||degree of deacetylation of chitosan UV-spectrophotometry colloid titration ~1H NMR spectroscopy electric titration|
Chitosan and its derivatives with vast and diverse (biological, physicochemical, mechanical, and film and fiber forming) properties has been employed for various applications in food and agriculture. It is important to find a simple, rapid and precise technique for D.D. measurement. Up to now, several methods have been developed to determine degree of N-deacetylation, D.D., for chitin and chitosan. In this article, an effort has been made to compare the available literature information on the D.D. determination.(1) Colloid titration was used to determine the substitution degree of deacetylation (D.D.) of chitosan. The effect of solution pH value, concentration and sodium chloride concentration on colloid titration were discussed. The advantages and disadvantages of colloid titration were compared with electrolytic titration and 1H-NMR. The results showed that colloid titration was an optimum method to determine the D.D. value of chitosan.(2) The substitution degree of deacetylation of chitosan (D.D.) was determined by UV-spectrophotometry, 1st derivative UV-spectrophotometry, multiwavelength Linear Regression UV-Spectrophotometry and dual standards UV-spectrophotometry. The advantages and disadvantages of four UV-spectrophotometry methods were compared with electrolytic titration, colloid titration and 1H NMR. The results showed that it is hardly to obtained accurate D.D. values by UV-spectrophotometry, so as the conventional acid-base titration, iodum indicator method and IR-spectrophotometry.(3) The availability of the NMR instrument is a limitation due to cost, special considerations, and sophistication, which render it no more appropriate for research purposes. We could determine the chitosan D.D. value using the three kinds of electric titration methods at the same time, but the time consuming of the dual abrupt change conductometric titration is so longer than that of colloid titration. Therefore, Colloid titration was a quick, simple quantitative and optimum method to determine the D.D. value of chitosan.