Problems of the MMD analysis of cellulose by SEC using DMA/LiCl: A review

The state of the art in the determination of cellulose molecular mass (MM) by the size-exclusion chromatography (SEC) method during the last 10 years was examined. The separation of cellulose/pulp during SEC under conditions usually applied, i.e. 0.5-1% LiCI in N,N-dimethylacetamide (DMA) at 80degreesC on styrene-divinylbenzene packing, was recognized as pseudo-exclusion. The salt sensitivity, over-salting and polyelectrolyte interactions have been proposed as the secondary phenomena accompanying the separation of polysaccharides in DMA with 0.5-1% LiCl added. Chemical heterogeneity as well as the conformation and rigidity of the polymer backbone are the governing factors of the distorting effect. It has been concluded that the SEC technique requires further improvement aiming at optimising the ionic strength and pH of the mobile phase and determining the Mark-Houwink constants. (C) 2002 Elsevier Science Ltd. All rights reserved.