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Handbook of Size Exclusion Chromatography and Related ...

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Figure 4 GPC elution curves <strong>of</strong> the kraft RL fractions before – – – – <strong>and</strong> after – – –<br />

laccase treatment. Molar mass growing from right to left. Lignin concentration 0.13 mg/<br />

mL, laccase charge 170 nkat/mg. (a) Fr 1; (b) Fr 2; (c) Fr 3. High molar mass part after<br />

treatment with laccase. (From Ref. 80.)<br />

or lignin–carbohydrate molecules in larger amounts <strong>and</strong> <strong>of</strong> higher MM in the<br />

subsequent chemical extraction performed as described above.<br />

MMD value for brown-colored substances in biologically treated<br />

wastewaters from paper production plants (84) have also been investigated.<br />

When comparing the SEC chromatograms <strong>and</strong> the UV spectra <strong>of</strong> the eluted brown<br />

substances with those <strong>of</strong> humic acids <strong>and</strong> lignin sulfonic acids, the eluted<br />

substances could be identified as polymeric organic substances with acidic ligninlike<br />

character.<br />

3.4 Physicochemical Investigations <strong>of</strong> Lignins<br />

Important information about changes in the relative MMs <strong>of</strong> lignin occurring<br />

during different processes is obtained by performing SEC measurements using online<br />

detection. Using sophisticated detectors it is possible to obtain absolute MM<br />

© 2004 by Marcel Dekker, Inc.

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