Partitioning behavior of silica in the Triton X-100/dextran/water aqueous biphasic system.

The partitioning behavior of silica particles was investigated in the Triton X-100/dextran/water system. It was found that both electrostatic effects and interactions between phase-component species and the solid surface played important roles in determining the distribution of solids. Silica partition was highly pH-dependent, which was interpreted in terms of the pH dependence of the Triton X-100/SiO(2) interaction and the weak acidity of dextran. The presence of sodium dodecyl sulfate (SDS) moved the particles from the top surfactant-rich phase to the interface and the bottom phase, while dodecyltrimethylammonium bromide (DTAB) had the opposite effect. These trends are attributable to the electrostatic interaction between the charged mixed micelles in the top phase and the particles and to the fact that the ionic surfactants modified the adsorption density of the nonionic surfactant on silica.