Abstract: The specific refractive index increments of a number of water soluble polymers inpure water were determined by quantitative size exclusion chromatography(SEC)equipedwith a refractive index detector.The results obtained are identical with literature values de-termined by conventional static methods. For SEC with aqueous salt solution as eluent,whick is similar to a mixed solvei,system,the chromatographic separation process of the so-lute with surrounding solvent molecules is equivalent to dialysis process. Under the condi-tions of chromatographic apparatus equiped with and without SEC separation columns,fromthe measured refractive index response constants the refractive index increment under con-stant chemical potential νμand under constant composition of the solvent νk of the polymerscould be determined.For the neutral polymer,polyacrylamide in aqueous NaCl solution,νμ>νk,that indicates the preferential adsorption of salt molecules by polymer chain,while forthe polyelectrolyte sodium polystyrene stilfonate,νμ<νk,i.e,the water molecules are prefer-entially adsorbed by polymer chain.

Key words: water-soluble polymer, refractive index increment, size exclution chromatogrphy