Evaluation of an improved acid hydrolysis‐HPLC assay for the acetyl content in chitin and chitosan

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Abstract
Functional properties of the amino polysaccharides, chitin and chitosan, vary significantly with their acetyl content. The acid hydrolysis‐HPLC method offers good accuracy and precision to assay the acetyl content regardless of the solubility of the sample. In this research, the hydrolysis parameters were changed, and the analytical method was counterchecked with other methods. Complete hydrolysis was achieved by mixing chitosan with 1.4 mM oxalic acid and 12 M sulfuric acid followed by treatment at 110°C for 40 min. A sealed glass ampule was used instead of a vacuum hydrolysis tube. The acetic acid released during acid hydrolysis was measured quantitatively by HPLC. A high correlation (r2 = 0.98) was obtained between the modified HPLC assay and the solid‐state 13C CP/MAS NMR method for the samples of various crustacean sources with a wide range of acetyl contents. The modified HPLC method was also highly correlated (r2 = 0.99) with the first derivative UV method for soluble chitosan. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006