Ultrahigh Molar Mass Component Detected in Ethylhydroxyethyl Cellulose by Asymmetrical Flow Field-Flow Fractionation Coupled to Multiangle Light Scattering

Asymmetrical flow field-flow fractionation (flow FFF) was connected to multiangle light scattering (MALS) and refractive index (RI) detectors for characterization of the molar mass distribution and molecular radius of a cellulose derivative, ethylhydroxyethyl cellulose (EHEC). Experimental conditions were optimized to allow study of a wide range of molar mass including even ultrahigh molar mass (UHM) components. The weight-average molar mass was 3.1 x 10^5 g.mol^-1 representing a very broad range (of molar mass) from 4.0 x 10^4 to 10^7 g.mol^-1, which corresponds to from <20 to 200 nm rms radius. The light scattering signal showed the presence of an UHM component, possibly an aggregate of extreme size, i.e.,~10^8 g.mol^-1 with a hydrodynamic diameter of 0.35 (mu)m. Careful choice of the pore size in in-line filters is necessary in order to minimize MALS detector noise without removing the UHM component. Flow FFF-MALS-RI was demonstrated to be uniquely suited to detect the presence of UHM components.