FRACTIONATION OF POLYDISPERSE DEXTRAN USING ETHANOL

For fractionating dextran using the antisolvent ethanol, the phase equ ilibria of polydisperse dextrans in the ternary system water-ethanol-d extran should be known, especially the influence of the molecular mass of the dextran on the liquid-liquid phase equilibrium. By applying th e lattice solution theory of Flory and Huggins with molecular mass dep endent interaction parameters, the molecular mass distributions of a d extran in both coexisting phases can be predicted from investigations of narrowly distributed dextrans in the same system. Numerical calcula tions are in good agreement with the molecular mass distributions of d extran obtained experimentally, using size exclusion chromatography. O n this basis, the influence of the concentrations of ethanol and dextr an of the total system on the fractionation of dextrans with any molec ular mass distributions can be calculated numerically.