Monodisperse Hydrolyzed Poly(glycidyl methacrylate-<i>co</i>-ethylene dimethacrylate) Beads as a Stationary Phase for Normal-Phase HPLC

The basic characteristics of a rugged, stable, and highly efficient polymeric stationary phase for normal-phase HPLC prepared by hydrolysis of porous monodisperse poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads have been studied and compared with those of bare Nucleosil silica and Nucleosil silica-diol. As a result of their overall chemical composition and the more than 10-fold larger surface coverage with hydroxyl groups, the polymer beads provide much higher retention of model solute molecules. In contrast to silica hydroxyls, all of the polymer surface diol groups are chemically equal and homogeneously distributed over all of the surface. In addition, they are less acidic than typical silanol functionalities. The exceptional selectivity of the polymeric column can be controlled by the composition of the mobile phase, as demonstrated with a broad spectrum of separations involving positional isomers of benzene derivatives, nonpolar isobutylene copolymers with minute composition differences, and hydrophilic poly(ethylene oxides) differing only in their chain length. Unlike silica phases, the properties of the polymeric stationary phrase are not affected by the presence of water in the mobile phase. As a result, repetitive gradient separations in eluents ranging in polarity from hexane through tetrahydrofuran to water can be easily accomplished.