Water-insoluble lignin

Figure 11 reveals that the water-insoluble lignin has a broad molar mass distribution with an average molar mass close to Mw = 2000 g/mol. 

Table I. Elemental Composition of the Water-Insoluble Lignin...

Water-insoluble lignin C9H7.4602.47(OCH3)o.83 Milled wood lignin (P. abies) (6) C9H8.8302.37(OCH3)o.96... 

It is assumed that the water-insoluble lignin is a polymerization and oxidation product of a Cio monomer, C9Hn03(0CH3). The brown color may be the result of loss of 0.17 methyl groups and hydrogen atoms during the formation of a quinonoid structure and loss of 0.7 moles of water. 

Figure 10. Lignins dissolved on heating spruce wood meal with dioxane-phosphate buffer (60 40% v/v) for 16 h at 150°C (A) Lignins dissolved (B) Water-insoluble lignin. Column Spherisorb ODS. Elution Gradient elution with phosphate buffer-methanol.

Figure 11. Water-insoluble lignin. Column Sephadex G-50. Eluent 0.5 M NaOH.

Figure 12. IR-spectra of the water-insoluble lignin and a MWL preparation of Pinus sylvestris (obtained by courtesy of Dr. Bo Hortling).

The water-insoluble lignin amounted to about one-third, and the hexane-dioxane soluble lignins (which were mostly monomers) to about 20%, of the lignins dissolved. 

Hiittermann, A. Gel permeation chromatography of water-insoluble lignins on controlled pore glass and sepharose CL-6B. Holzforschung 32, 108-111 (1978)... 

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