Liquid-phase Adsorption from Binary Solutions on Silica Gel. Separation Factors and Orientation of Adsorbed Components on the Surface

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Abstract
The preferential adsorption equilibria of various binary solutions of cyclohexane-aromatic compounds and cyclohexane-cyclic ethers on chromatographic silica gel have been studied at 30°C. On the basis of the assumption that the adsorption is of the Langmuir-type, the separation factors (α) and the numbers of moles in the adsorbed-phase per unit mass of silica gel (nσ⁄m) have been calculated. The values of logα correlate well not only with the electron-donating properties of the preferentially-adsorbed components, but also with the powers of the gas-phase adsorption on silica gel and of the liquid-liquid interaction with liquid trimethylsilanol. Moreover, on the basis of the information on nσ⁄m, the orientation angles of the adsorbed components on the surface have been evaluated. The adsorption of the aromatic hydrocarbons was nearly flat to the surface, and that of the cyclic ethers, perpendicular.