Some Aspects of Lignin Characterization by High Performance Size Exclusion Chromatography Using Styrene Divinylbenzene Copolymer Gels

The molecular weight distributions (MWD) of alkaline-extracted steam-exploded aspen (Populus tremuloides L.) lignin and organosolv black cottonwood (Populus trichocarpa L.) lignin are compared with those of milled wood lignin from aspen. High-performance size exclusion Chromatography (HPSEC) of these acetylated lignins on styrene-divinylbenzene copolymer gels was investigated s a function of the organic solvent elution System from tetrahydrofuran to dimethylformamide (DMF) alone or in the presence of 0.1 M LiBr. In the mixed solvent and DMF the three types of lignin reported in this study displayed multimodal elution behavior indicative of associative phenomena. Addition of LiBr to DMF reduced the observed apparent associative behavior of the lignins. The Interpretation of calibration Standard elution in these solvent Systems is discussed with reference to the behavior of polystyrenes, Igepal polymerst and lignin model compounds. Deconvolution of the elution profile of a lignin into acetylated monomers, dimers, and mixtures of trimers was performed.