Preparation and Evaluation of an End-Capped p-tert-Butyl-Calix[4]arene-Bonded-Silica Stationary Phase for Reversed-Phase High-Performance Liquid Chromatography

The preparation, characterization, and potential liquid chromatographic applications of an end-capped p-tert-butyl-calix4]arene-bonded-silica phase are presented. The phase was prepared by covalently bonding p-tert-butyl-calix4]arene-derivatized aminosilane to silica gel then end-capping with trimethylchlorosilane. Use of the new phase enabled good separations not only of polar and non-polar aromatic compounds, basic aromatic compounds, and polycyclic aromatic hydrocarbons but also of some isomers. It is more selective toward alkylbenzenes than Kromasil-C₁₈-SiO₂. The retention mechanisms involve strong hydrophobic interaction, strong π–π interaction, and host–guest interaction. Elemental analysis calculations confirm that the large molecules bonded to the silica act as shield against residual surface silanols. Assay of simvastatin and lovastatin on this column is also reported.