A Novel Polar Separation Medium for the Size Exclusion Chromatography of Small Molecules: Uniformly Sized, Porous Poly(vinylphenol-co-divinylbenzene) Beads

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Abstract
A novel separation medium based on uniform size beads of 4-hydroxystyrene-divinylbenzene can be used for both the size exclusion chromatography of small molecules and their separation by reversed-phase chromatography. The new 5 μm material is prepared by the controlled swelling of monodispersed polystyrene particles, that serve both as porogen and shape template, with a polymerization mixture consisting of the monomers and dibutylphthalate, followed by a suspension polymerization. Removal of the acetoxy groups by hydrolysis with aqueous base leads to the final poly(4-vinylphenol-co-divinylbenzene) monodispersed beads. Polymerization conditions that favor the formation of very small pores were developed to optimize the beads for the SEC separation of small molecules. The SEC calibration curve confirms that the optimized beads contain a large volume of pores suitable for the separation of solutes with a molecular weight of up to about 1000. The ability to separate alkylbenzenes according to their hydrodynamic sizes has been demonstrated using a column packed with this material. In addition, the phenol chemistry used in combination with a hydrophobic crosslinking monomer provides this separation medium with an unusual versatility that allows both reversed phase and normal phase chromatography to be run in the same column after a simple change of the mobile phase.