SEC–MALLS analysis of wood holocelluloses dissolved in 8 % LiCl/1,3-dimethyl-2-imidazolidinone: challenges and suitable analytical conditions

Abstract

The use of size-exclusion chromatography in combination with multi-angle laser-light scattering analysis (SEC–MALLS) can provide useful information pertaining to the molecular mass parameters of wood celluloses and hemicelluloses. When wood holocelluloses containing significant amounts of hemicelluloses were soaked in ethylenediamine (EDA) and subjected to sequential EDA-removal and solvent-exchange processes into 1,3-dimethyl-2-imidazolidinone (DMI) under suitable conditions, the resulting materials provided much more reliable molecular mass parameters when they were dissolved in LiCl/DMI and subjecting to SEC–MALLS analysis. Furthermore, the residual EDA molecules trapped in the EDA-treated holocelluloses could be removed by simply washing with methanol following the solvent-exchange process. The effect of the stirring time for the EDA-treated and solvent-exchanged eucalyptus holocellulose in 8 % (w/v) LiCl/DMI was investigated in terms of its impact on the molecular mass parameters of the high-molecular-mass cellulose fractions and found to have no impact for up to 5 months. The optimal EDA treatment and solvent-exchange conditions obtained for eucalyptus holocellulose were subsequently applied to various other wood holocelluloses, including Japanese cedar, ginkgo and birch, which gave characteristic SEC elution patterns together with the corresponding molecular mass parameters, depending on their hemicellulose contents and the number of cellulose/lignin/hemicellulose chemical linkages present in their high-molecular-mass cellulose fractions. The weight-average degrees of polymerization of the high-molecular-mass cellulose fractions in the wood holocelluloses ranged from 4400 to 6400, which were higher than those of cotton cellulose (2700) and bacterial cellulose (3100).