Determination of the degree of polymerisation of carboxymethyl cellulose by size exclusion chromatography

A size exclusion chromatographic (SEC) system was developed in order to investigate the molecular weight distribution of depolymerisation products obtained by enzymatic degradation of carboxymethyl cellulose (CMC). The SEC system, which relies on a Superose 12 HR 10/30 column and an eluent containing sodium hydroxide (0.05 M), enabled an effective separation of CMC fragments. Cellulase was used for the degradation of CMC. Degradation was followed as a function of incubation time and cellulase dosage by viscosity measurements. The CMC hydrolysates separated by SEC were detected as total organic carbon (TOC) and reducing sugars. The degree of polymerisation (DP) of the hydrolysates was then determined by dividing the number of anhydroglucose units by the reducing sugar concentrations. The DP of the CMC fragments obtained after enzymatic hydrolysis ranged from 100 to 1, compared with a DPv of 170 for untreated CMC samples. The results obtained for a series of CMC fragments agreed with the DP values of standards of known molecular weight. The method is an absolute method; no external calibration was needed to calibrate the Superose 12 HR 10/30 column.