Quantitative Analysis by IR: Determination of Chitin/Chitosan DD

Abstract

FTIR spectroscopy has been widely used to quantitatively study the parameters of the chitin deacetylation. A new research on a Canadian chitin has shown that a degree of deacetylation (DD) of 90% has been reached with a base concentration of 12.5 M, a reaction time of 120 min, and a temperature of 110°C. In parallel, our study on Moroccan chitin allowed to reach 75%. A degree of deacetylation of 75% was obtained at T = 120°C and at CNaOH = 12 N in a single step for 6 hours. Another study followed by IR prepared the chitosan under pressure or under irradiation. Firstly, the compression method was used for preparing 100% deacetylated chitosan with less environmental pollution. The 100% fully deacetylated chitosan is produced in low-concentration alkali and high-pressure conditions under 0.11–0.12 MPa for 120 min. Secondly, microwave deacetylation showed that a degree of deacetylation of 95.19% was achieved after irradiating chitin at 60 meshes with 50% NaOH solution in a microwave for 10 min at 1400-W power. To find these results, the authors used different formulas to calculate DD by FTIRM, but the most used and reliable formula is that which calculates DD of chitosan by the report of absorbance of amide at 1655 cm−1 that measures the acetyl group and absorbance at 3430 cm−1 relating to the hydroxyl group