Solvatochromic studies of the surface polarity of silica under normal-phase conditions

The solvatochromic method has been used to quantify the dipolarity-polarizability, hydrogen-bonding acidity, and hydrogen-bonding basicity of the surface of silica under normal-phase conditions. In n-hexane-chloroform mixtures, the surface dipolarity-polarizability and hydrogen-bonding acidity of silica are not affected by the composition of the mixtures. The surface of silica has a high dipolarity-polarizability and a high hydrogen-bonding acidity. The hydrogen-bonding basicity of silica is much lower and decreases as the concentration of chloroform increases in the mobile phase.