Straightforward Determination of the Degree of N-Acetylation of Chitosan by Means of First-Derivative UV Spectrophotometry

Chitin is a structural polysaccharide that can be found in the cell wall of fungi and in the exoskeleton of most invertebrates, of which crustaceans are currently the major source of chitin for the industry. This polysaccharide is similar to cellulose, both in function, chemical structure and abundance; chitin is likely to be one of the most abundant natural macromolecules in the biosphere. Besides its central importance as a building and structural material in a great number of biological organisms, chitin is winning a central role as a raw material in engineering and emergent technologies, in great part owing to its soluble derivative, chitosan. Given its natural abundance, it promises to be one of the future, important sources of renewable materials. In fact, more or less successfully, chitin and chitosan have been proposed for a broad range of industrial applications, including wastewater treatment, food, agriculture, cosmetics, biotechnological processes and separation technologies, as well as, for medical applications, such as biomaterials and tissue engineering. It can be also used as a precursor to produce other materials through chemical modification. Chitin is poly[b-(1!4)-2-acetamido-2-deoxy-D-glucopyranose]. N-deacetylation processes give origin to a series of copolymers varying in the relative amounts of its comonomers, b-(1! 4)-2-acetamido-2-deoxy-D-glucopyranose (GluNAc) and b-(1!4)-2-amino-2-deoxy-D-glucopyranose units (GluN). The molar fraction of the GluNAc units is defined as the degree of N-acetylation (DA). Chitosan is the most N-deacetylated part of this series of copolymers. Although the criteria that defines what is chitin or chitosan based on the DA value is somewhat controversial, chitosan is often Full Paper