IMPROVED METHOD FOR IR 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/A3450 ratio, gives the expected rate of deacetylation curve. Consideration of the various i.r. ratios has led to a new relationship, % N-acetylation = (A1655/A3450) x 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%.