Improved method for i.r. determination of the degree of N-acetylation of chitosan

Three published i.r. absorption band ratios for determining the % N -acetylation of chitosan have been used to follow the rate of alkaline deacetylation of chitin. Only one, the A 1655 /A 3450 ratio, gives the expected rate of deacetylation curve. Consideration of the various i.r. ratios has led to a new relationship, % N -acetylation = ( A 1655 /A 3450 ) × 115, where the absorbance of the amide I band at approximately 1655 cm −1 is determined using the baseline proposed previously. The values obtained using this proposed relationship agree closely with those obtained from dye adsorption measurements for chitosans having % N -acetylation values in the range 0–55%.