Molecular weight determination of lignosulfonates by size-exclusion chromatography and multi-angle laser light scattering

A lignosulfonate sample was fractionated according to the solubility in ethanol-water. The fractions were analysed by aqueous size exclusion chromatography (SEC) combined with in-line multi-angle laser light scattering (MALLS), and by static MALLS. Satisfactory SEC results were obtained with aqueous phosphate buffer containing DMSO and SDS. The refractive index increment (dn/dc) varied from 0.186 to 0.205 ml/g, depending on M-w and the degree of sulfonation. The second viral coefficient (A(2)) was 7 x 10(-3) ml mol/g(2). The weight-average molecular weight (M-w) of the fractions varied from 4600 up to 398 000 g/mol, and the polydispersity (M-w/M-n) varied between 1.3 and 3.5. (C) 2002 Elsevier Science B.V. All rights reserved.