Determination of the degree of acetylation (DA) of chitin and chitosan by an improved first derivative UV method

An economical and accurate determination of degree of acetylation (DA) for highly acetylated chitin has always been a challenge for researchers dealing with chitin and chitosan. A new protocol for the first derivative UV method using concentrated phosphoric acid as a solvent for highly acetylated chitin was developed in this study. The solvent was proposed based on thorough investigation of the effects of associated reactions including chain degradation, monomer dehydration, and oxazolinium ion formation. The reproducibility and performance of the new protocol was evaluated using commercial samples and the results showed the DA values of both chitin and chitosan could be determined accurately by a single analytical technique in less than 3 h.