Characterization of Chemical Heterogeneity of Cellulose Esters by Gradient Elution HPLC

A gradient polymer elution chromatography (GPEC) method was developed that can separate cellulose acetate (CA) with respect to a wide range of degrees of substitution (DS). A series of cellulose acetate propionate and cellulose acetate benzoate samples were synthesized by propionylation or benzoylation of CA samples with average degrees of substitution ranging from 0.6 to 2.9, and compositionally separated using the GPEC method. The reversed-phase gradient separation based on an adsorption/desorption mechanism, a linear gradient of acetonitrile : H 2 O = 6 : 1 and ethyl acetate was used with a phenyl group-modified silica column as stationary phase. Separation of samples with different DS values was achieved for both sample series. A slight molar mass effect was observed during elution for the sample with low DS. In addition, a sharp peak at low retention time was observed for the high DS sample. Although a search for further separation systems is necessary for the determination of quantitative substitution degree distribution, this method is applicable to the determination of DS distribution over a wide DS range.