Determination of the degree of N-acetylation for chitin and chitosan by various NMR spectroscopy techniques: A review

Up to know, several methods have been developed to determine degree of N-acetylation, DA, for chitin and chitosan. In this article, an effort has been made to review the available literature information on the DA for the two biopolymers by different techniques of nuclear magnetic resonance, NMR (H-1 NMR, C-13 NMR, and N-15 NMR) spectroscopy. This article describes the effects of various parameters and different compounds as impurities of the original polymers (moisture, minerals, proteins, and pigments) on the accuracy of the DA values. This study allows one to choose an appropriate technique to determine the DA for the two polymers. These techniques have been compared for their performances and limitations. Among various NMR spectroscopy techniques, H-1 NMR is the most sensitive and precise technique and results in the most accurate data. C-13 NMR and N-15 NMR techniques have been employed for entire range of the DA. (C) 2009 Elsevier Ltd. All rights reserved.