Retention behavior of colloidal dispersions in sedimentation field-flow fractionation

Abstract

Sedimentation field-flow fractionation (SdFFF) has a high resolution over a wide range of particle size compared with other methods of size determination of colloidal dispersions. However, the retention behavior in SdFFF depends strongly on the experimental parameters, especially the ionic strength of the carrier solution. The sizes calculated from the results of the experiment by using the theory of Giddings are underestimated if the carrier solution with low surfactant concentration is used, compared with those determined by other techniques. To explain this phenomenon, this review discusses theoretically the perturbation behavior in the retention by the particle—wall interaction due to electrostatic repulsive and van der Waals' attractive forces, and by the contribution of particle motion in shear flow. The influence of particle—wall interaction was not significant at low sample concentrations below 0.1% and at high ionic strengths of the carrier solution above 10 −3 M. However, under low ionic strength conditions of the carrier solution, the concentration profiles in the channel spread widely, and the estimated retention time decreases from the Giddings' theory. The effect of particle motion in shear flow appears at the measurement of large particle with high ionic concentration solution, and the retention ratio will become smaller. But this effect is not so large compared with particle—wall interaction.