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

► We developed a new method for determination of the degree of N-acetylation of chitin and chitosan. ► We used first derivative diamond ATR FTIR spectroscopy. ► The new method allows the determination of the degree of N-acetylation in the presence of water. ► The new method was compared to results obtained by UV spectroscopy, elemental analysis, and Raman spectroscopy.