Comparative Analysis of Alkaline-Extracted Hemicelluloses from Beech, African Rose and Agba Woods using FTIR and HPLC

Abstract

The vast application of hemicellulose in industry is greatly influenced by its chemical components. The hydroxyl spectra vibrations (3919-3671 cm -1 ) from the FTIR spectra indicates the presence of non-hydrogen bonded OH stretch and normal polymeric OH stretch (3454-3211 cm -1 ) in the three samples. The samples contained residual lignin indicated by IR absorption bands at 1592 and 1525 cm -1 . The presence of C=O stretching vibrations of acetyl groups at 1734 cm -1 indicated that African rosewood was generally an acetylated molecule. Each heteropolysaccharide also contained reducing monosaccharides at their ends suggested by the C-H stretching vibrations. Infrared absorptions characteristic of asymmetric β-1,6-glycosidic stretching was present in Beechwood and Agbawood, respectively, and African rosewood gave three absorption bands β-1,3-glycosidic stretch, β-1,4-glycosidic stretch and an asymmetric β 1,6-glycosidic stretch, respectively. Agbawood gave a major absorption band at 923.75 cm -1 corresponding to the absorption band at β-1,4-glycosidic stretching. African rosewood contained 96% mannose and 4% of an unidentified sugar. Beechwood contained primarily glucose, but Agbawood contained 20, 14, 8 and 57% glucose, mannose, galactose, and an unidentified sugar, respectively.