Determination of the degree of N-acetylation (DA) of chitin and chitosan in the presence of water by first derivative ATR FTIR spectroscopy.

A new method for the determination of the degree of N-acetylation (DA) of chitin and chitosan is described using first derivative diamond ATR FTIR spectroscopy. Applying the derivative values of the amide III band at 1327cm and the CH deformation band of the N-acetyl group at 1383cm as measure of the N-acetyl content of the sample in relation to the derivative value of the bridge oxygen vibration at 1163cm as internal standard, a linear correlation to the results of first derivative UV spectroscopy was obtained and confirmed by elemental analysis and Raman spectroscopy. The described method allows the determination of the degree of N-acetylation of chitosan and chitin in the presence of water thus making drying procedures unnecessary.