On the composition of dioxane-water extracts of milled spruce wood: Characterization of hydrophilic constituents (Corrected reprint)

Dioxane-water extracts of spruce wood milled according to Bjorkman were examined. Fractionation by liquid-liquid extraction using a system containing water, acetic acid, pyridine and chloroform gave fractions from the organic layer freed from carbohydrates and consisting essentially of lignin with very low carbohydrate content (0.2-0.3%), and fractions from the aqueous layer consisting primarily of carbohydrates and lignin carbohydrate compounds with quite a high carbohydrate content. It could be concluded from experiments with modified extraction procedures that carbohydrate content and, to some extent, molecular mass are of importance for the separation of the constituents of extractives subjected to liquid-iiquid extraction.The selectivity of the extraction procedure was examined using model compounds studies. The results suggest that the organic layer is completely freed from constituents consisting solely of carbohydrates. Application of gel chromatographic techniques made it possible to isolate fractions of lignin carbohydrate compounds of low to moderate molecular mass from the aqueous layers. Further examinations (UV, carbohydrate analyses, thin layer chromatography, electrophoresis) corroborated that lignin or ligninrelated compounds and carbohydrates were chemically attached to each other in these fractions. In one of the fractions (carbohydrate content, 20.1%; molecular mass about 2000) galactose was a prominent constituent of the carbohydrate moiety. (First published in Nordic Pulp & Paper Research Journal no. 3, 1990 p. 107-113.