Raman and FTIR spectroscopic study of carboxymethylated non-starch polysaccharides

Abstract

Four types of non-starch polysaccharides including cellulose, guar gum, locust bean gum and xanthan gum were modified by carboxymethylation. The degree of substitution (DS) was determined by a colorimetric method. Raman and Fourier transform infrared spectra of the native and modified polysaccharides were acquired and analysed. Representative marker bands, with intensities and/or integrated areas affected by carboxymethylation, were selected at 1607 cm-1 (Raman) and 1315 cm-1 or 1605 cm-1 (IR), attributed to C{double bond, long}O carbonyl stretching vibration. The ratios of intensities (or areas) of the marker bands to that of an internal standard band, corresponding to the skeletal configuration and linkages (850-950 cm-1), were plotted against DS. Linear fits were obtained with high correlation coefficients, r > 0.96 (p < 0.01), suggesting a strong correlation between the spectroscopic data and DS determined by wet chemistry. Some structural changes were also observed from the spectral data. © 2008 Elsevier Ltd. All rights reserved.