A method Is presented for isolating low-molar-mass aromatic compounds such as vanillin, acetovanillone, guaiacol, and p -hydroxybenzaldehyde, which are formed from lignin by alkaline air oxidation of spent sulfite liquor. The compounds are adsorbed on a strong cation-exchange resin in sodium form and then separated from other compounds of the oxidized spent sulfite liquor by elution with either water or a sodium carbonate solution.

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When polyelectrolytes (lignosulfonates) with a broad molecular weight distribution are eluted from Sephadex gels with water, the fractionation is affected by steric exclusion, polyelectrolyte expansion, ion exclusion, and ion inclusion effects. The ion inclusion effect is due to interaction of charged sites in the macro‐ions which are more or less excluded from the gel with charged sites in more permeable macro‐ions. The ion inclusion effect depends on the cation of the lignosulfonates in such a way that the elution of lignosulfonates with a univalent cation is affected to a greater extent than the elution of lignosulfonates with a divalent cation. This is due to the existence of a higher density of free charges in the lignosulfonates with a univalent cation owing to a lesser tendency to form ion pairs. By choosing suitable eluents, it is possible to alter the retention volumes of lignosulfonates of different sizes and thus optimize the resolution.

Lignin sulfonates obtained through sulfonation of Western Hemlock wood chips (W), and also lignin sulfonates prepared from milled wood lignin (MWL), were fractionated by Sephadex gel chromatography in aqueous solution and then acetylated and methylated. The resulting acetyl lignin sulfonate methyl ester (ALSME) fractions were characterized by nuclear magnetic resonance spectroscopy carried out in deuteriochloroform solutions, and the usefulness of this procedure was established. The ALSME-MWL fractions were also characterized by chemical analyses. Mass spectroscopy did not yield useful results. The findings are interpreted in relation to the structure of lignin sulfonates. Gel permeation chromatography of ALSME fractions was carried out in methanol on Sephadex LH-20 and yielded further evidence indicating the separation in part of low molecular weight ALSME species including one which was obtained in crystalline form.

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