A CHROMATOGRAPHIC COMPARISON OF THE RELATIVE LEWIS ACIDITIES OF ALUMINA AND ZIRCONIA

The chromatographic properties of alumina and zirconia are compared with respect to their relative Lewis acidities when parabenzoic acid derivatives are chromatographed in aqueous media. Weak Bronsted acids show similar capacity factors on alumina and zirconia. As solute Bronsted acidity increases, the capacity factor increases more significantly on the zirconia phase than on the alumina phase. Efficiencies, as determined by the dominant desorption rate constants, are generally comparable between the two phases with alumina showing slightly higher efficiencies. Secondary interactions between the solutes and the stationary phases are nearly absent on zirconia but are very apparent on the alumina phase.