Development and in situ synthesis of monolithic stationary phases for electrochromatographic separations

Organic monolithic stationary phases have been synthesized in UV-transparent fused-silica capillaries, which have been used as test format of microfabricated device channels. The columns have been prepared by in situ polymerization of butyl acrylate, lauryl acrylate, 1,3-butanediol diacrylate, and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) in a ternary porogenic solvent. The resulting stationary phases have been tested in capillary electrochromatography and exhibited reversed-phase chromatography behavior toward neutral solutes. Van Deemter plots of phenylureas and polycyclic aromatic hydrocarbons, selected as model analytes, have been determined to study the influence of various polymerization and separation parameters on properties of the monoliths. The amount of AMPS and the nature of monomers in the polymerization solution have been thus adjusted. It has been observed that the ionic strength of the mobile phase may affect significantly the efficiency of the separation. The effect of the percentage of acetonitrile in the mobile phase on efficiency and permeability of the organic monoliths has also been investigated. Efficiencies greater than 300,000 plates/m have been obtained with the test compounds. Stability and reproducibility have been extensively studied.