Evaluation of infrared spectroscopic techniques for analysing chitosan

Abstract The use of the 3450 cm −1 absorption band as an internal standard in the determination of the extent of N ‐acetylation of chitosan from the absorbance of the amide I band at 1655 cm −1 was studied. The results show that the technique gives consistent results that are relatively unaffected by whether the sample is air‐dried or oven‐dried. A number of chitosan samples, covering the range of N ‐acetyl values from 14% to 72% were analysed by three techniques: infrared spectroscopy using the ratio A 1655 / A 3450 , hydrobromide salt titration and residual salicylaldehyde determination. There is a very good correlation between the results from infrared spectroscopy and those from the other two analytical techniques, confirming the validity of the former technique.