ABOUT THE POSSIBILITY OF QUANTITATIVE DETERMINATION OF LIGNIN AND CELLULOSE IN PLANT MA-TERIALS USING IR SPECTROSCOPY

Abstract

A methodical approach for quantitative determination of lignin and cellulose in plant materials by midinfrared FT-IR spectroscopy using the suspension method in tablets with KBr was proposed. For the prepared model binary mixtures of pure cellulose and lignin a direct correlation was achieved between the concentration and intensity of the analytical absorption bands of lignin (1508–1512 cm-1) and cellulose (1059–1061 cm-1). Based on the obtained intensity / concentration dependences formulas were derived that allow calculating the content of lignin and cellulose. The proposed method was tested on a wide range of plant biomass samples: 9 wood samples and 11 samples of agro-processing wastes. A good suitability of the proposed method for the quantitative determination of lignin was shown; the deviation from the literature data was no more than 1%. However, the proposed method was not suitable for the determination of cellulose since it didn't take into account the contribution of hemicellulose and extractive substances in the absorption band of 1059–1061 cm-1, which resulted in greatly overestimated results of cellulose content determination.