SOLVATOCHROMIC STUDIES OF THE SURFACE POLARITY OF SILICA UNDER NORMAL-PHASE CONDITIONS

The solvatochromic method has been used to quantify the dipolarity-pol arizability, hydrogen-bonding acidity, and hydrogen-bonding basicity o f the surface of silica under normal-phase conditions. In n-hexane-chl oroform mixtures, the surface dipolarity-polarizability and hydrogen-b onding acidity of silica are not affected by the composition of the mi xtures. The surface of silica has a high dipolarity-polarizability and a high hydrogen-bonding acidity. The hydrogen-bonding basicity of sil ica is much lower and decreases as the concentration of chloroform inc reases in the mobile phase.