Determination of polymerization degree of maltooligosaccharides by FT-IR/ATR spectroscopy

In this work the use of Fourier transform infrared (FT-IR) spectroscopy coupled with an attenuated total reflectance (ATR) accessory was applied to determine the polymerization degree of straight-chain oligosaccharides. Glucose (G1) was used as monosaccharide and maitooligosaccharides (G2 similar to G7) that from two to seven glucose polymerized were used as straight-chain oligosaccharides. Seven kinds of same concentration sugar solution (G1 similar to G7) were prepared and their infrared spectra were measured. It was, shown that the shape of spectra in fingerprint region for G5, G6 and G7 were similar. The partial least-squares (PLS) regression was used to determine polymerization degree of maltooligosaccharides from spectra in fingerprint region. The number of C-O-C group was used instead of polymerization degree because C-O-C group forms additionally on polymerization of sugars. Regression analysis against the calculated value gal e a correlation coefficient of 0.999. In order to apply this spectroscopy to on-line prediction of individual sugar concentrations in mixtures, curve-fit of the fingerprint region was attempted to extract the absorption bands affected by polymerization, and three component bands were extracted. The multiple linear regression was used to determine polymerization degree of maltooligosaccharides from spectra in fingerprint region. The number of COC group was predicted by the absorbance of spectra of maltooligosaccharides at three component bands. The comparison between predicted values of the number of C-OC group and the values calculated by preparation of materials showed good agreement. Especially, accurate agree ment was shown for maitooligosaccharides from G1 to G.