Characterization of the surface properties of Mg/Al oxides by the solvation parameter model.

The oxides of different Mg/Al ratios (Mg/Al = 0, 0.1, 5, 10 and infinity) were prepared, and the characterization of these oxides was attempted by estimating characteristic interaction parameters based on the solvation parameter model. The magnitudes of the regression coefficients varied with the increase of Mg/Al ratio. For the oxide of Mg/Al = 0.1 and Al2O3, the contribution of these characteristic interactions for solutes' retention was similar to that of the common silica, and the dipolarity/polarizability (pi*), the solute hydrogen bond donating (alpha2(H)) and accepting (beta2(H)) abilities played an important role. Yet, the retention behavior at a higher Mg/Al ratio (Mg/Al = 5, 10 and MgO) drastically changes, and V(i)/100 (the intrinsic molar volume), pi*, alpha2(H) and beta2(H) all favored the solutes retention. By comparison of the regression coefficients on various normal-phase (NP) and reversed-phase (RP) columns, a new model was developed to correlate the solute retention factors on Mg/Al = 5, 10 and MgO columns with the data of NP and RP columns.