The use of DSC curves to determine the acetylation degree of chitin/chitosan samples

The use of DSC curves is proposed as an alternative method to determine the degree of N-acetylation (DA) in chitin/chitosan samples, based in both peak area and height of the decomposition signal. Samples with DA from 74 to 16% were prepared from a chitin commercial sample and the DA was determined by H-1 NMR, C-13 CP/MAS NMR and IR spectra. The effect of water content, heating rate, sample mass and gas flow on the DSC peaks were evaluated and optimized. Using optimized conditions a linear relationship between peak area and height with the DA could be achieved with linear correlation coefficients of -0.998 and -0.999 (n=7), respectively. The calibration graphs were used to determine the DA of a commercial chitosan sample with relative errors ranging from 2 to 3% for both peak area and peak height, when compared with the DA determined by H-1 NMR method. (c) 2006 Elsevier B.V. All rights reserved.