Intrinsic Viscosity Determination by “Single-Point” and “Double-Point” Equations

With rheology progress was made in understanding of structure of gels and colloidal suspensions, particularly with regard to polysaccharides and large glyconjugates. Whereas the rheology of concentrated dispersions is the considerable interest to the colloidal scientist, pharmacist or food technologist [1], of more interest to molecular biophysicist is dilute solution viscometry and the structural parameter the intrinsic viscosity [2]. The intrinsic viscosity is a viscosity measure extrapolated to infinite dilution that depends on the properties of isolated macromolecules in solution (effects of interaction have been eliminated by extrapolation). So, intrinsic viscosity provides information about molecular weight, radius of gyration, shape, specific volume, conformation, hydration, flexibility of the macromolecules. Several empirical equations relating viscosity to concentration [2 4] have been proposed in order to determine intrinsic viscosity [h]. The three most commonly used equations, concerning dilute solutions, are the following: