Determination of the Degree of Acetylation of Chitin/Chitosan by Pyrolysis-Gas Chromatography in the Presence of Oxalic Acid

Abstract

A new method to determine directly and rapidly the degree of acetylation of chitin/chitosan was developed based on reactive pyrolysis-gas chromatography in the presence of an oxalic acid aqueous solution. The degree of acetylation was precisely evaluated on the basis of peak intensities of the characteristic products such as acetonitrile, acetic acid, and acetamide originating from the N-acetyl group of N-acetyl-d-glucosamine units of chitin/chitosan. The observed values were in good agreement with those obtained by (1)H NMR and the other methods. Moreover, the proposed technique was applicable to any kinds of chitin/chitosan samples over the whole range of acetylation including insoluble chitin/chitosan and perfectly acetylated artificial chitin having higher crystallinity to which (1)H NMR had been inapplicable.