Characterization of lignins from organosolv pulping according to the organocell process: Part 3. molecular weight determination and investigation of fractions isolated by GPC

Both residual lignins and lignins isolated from the pulping liquor of 20 1 batch cookings of spruce chips according to the Organocell process were subjected to HPSEC. Checking the resulting M_n-values by vapor pressure osmometry confirmed the HPSEC data except for first stage lignins with short cooking times, where the different elution behavior caused by high portions of organic nonlignin substances is held responsible for these discrepancies. The molecular weights of residual lignins, which were found to be considerably higher than those of the corresponding soluble lignins, are dependent on yields and/or isolation procedure and are therefore not representative of the total lignin in the pulp.