On-line coupling of flow field-flow fractionation and multiangle laser light scattering for the characterization of macromolecules in aqueous solution as illustrated by sulfonated polystyrene samples

Seven sulfonated polystyrene standards (18 000-3 000 000 g/mol), taken as model substances for macromolecular polyelectrolytes, were dissolved in aqueous 0.1 M sodium nitrate solution and characterized by multiangle laser light scattering coupled on-line to now field-now fractionation. The distributions of molar mass and root mean square radius and the diffusion coefficients were obtained for each sample using a constant field of force for separation. Relationships between molar mass and root mean square radius [[R(G)(2)](0.5)(z) = (2.71 x 10(-2))M(w)(0.56)] or diffusion coefficient [D = (7.10 x 10(-8))M(w)(-0.68)] were calculated. To investigate the static analytical range of this novel hyphenated technique a mixture of all seven samples was fractionated applying a programmed field. The relationship obtained between root mean square radius and molar mass was used to calculate a Mark-Houwink equation [[eta]calcd = (2.99 x 10(-2))M(w)(0.68)]. To verify this result, the intrinsic viscosities for all samples were measured at low shear rate and found to be in good agreement [[eta]calcd = (2.77 x 10(-2))M(w)(0.67)].