Determination of the DS distribution of non-degraded sodium carboxymethyl cellulose by gradient chromatography.

Two series of sodium carboxymethyl celluloses (NaCMCs) derived from microcrystalline cellulose (Avicel samples, DP~160) and cotton linters (BWL samples, DP~1400) with average degrees of substitution in the range DS=0.45-1.55 were analyzed by gradient liquid adsorption chromatography (gradient LAC) in order to determine their chemical composition distributions (DS distributions or 1st order heterogeneities). Clear separations of samples having different average DS values were achieved for both sample series, allowing determination of the DS distributions of the samples. A slight molar mass influence on the eluent composition at elution was observed. From the DS distributions the DS standard deviations were calculated and taken as a measure for the extent of chemical heterogeneity of the single samples. While no noticeable dependence of the chemical heterogeneity on average DS was observed for Avicels, the heterogeneity decreases with increasing average DS for BWLs.