Determination of the pattern of acetylation of chitosan samples: Comparison of evaluation methods and some validation parameters

Chitosan is a linear copolymer consisting of glucosamine and N-acetylglucosamine units. Its specific biological features make it a very attractive biomaterial for diverse applications in both pharmaceutics and medicine. The pattern of acetylation of chitosan samples (PA) can strongly influence their biomedical activities. So far, three methods of determining the PA value of chitosan samples, based on NMR spectroscopy, have been developed. Chitosans with a degree of acetylation (FA) from 0.02 to 0.48 were used to compare these methods. The most suitable and specific method of PA determination was 13C NMR based on the intensities of carbon C-5 signals. Some validation parameters—specificity, sensitivity, precision (repeatability and reproducibility)—were established. The intra- and inter-day precision of this method depended on the degree of acetylation of the chitosan samples. It was found to be specific, sensitive, repeatable and reproducible.