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Both the separation behavior and the structure of a polymer monolith column depends on both the reaction solution composition and the polymerization conditions. In photoinitiated low-temperature polymerization, polymerization temperature, irradiation intensity, and polymerization time were key factors to control the monolith characteristics. In this study, the effect of polymerization time on the chromatographic, material, and chemical characteristics of poly(butyl methacrylate-co-ethylene dimethacrylate) monoliths was studied using pyrolysis-gas chromatography, Raman spectroscopy, inverse size exclusion chromatography, scanning electron microscopy, and chromatographic methods. Both butyl methacrylate and ethylene dimethacrylate monomers were incorporated into the monolith as the polymerization time increased, and it resulted in increases in both the flow resistance (decrease in both permeability and total/through pore porosities) and retention factors. The longer polymerization time led to lower relative amounts of free methacrylate functional groups in the monolith, i.e. cross-linking was enhanced. The increase of the polymerization time from 8 to 12 min significantly reduced the separation efficiency for the retained analyte, whereas an increase in the fraction of the mesoporosity was observed. [ABSTRACT FROM AUTHOR]

Abstract: A methacrylate-based anion-exchange monolithic column was prepared by a single-step UV photo-copolymerization of [2-(methacryloyloxy)ethyl]-trimethyl ammonium chloride, butylmethacrylate, and ethylene dimethacrylate at a low temperature of −15°C. The anion-exchange column exhibited good separation efficiency for the small inorganic anions of NO2 −, Br−, NO3 −, and I− in the isocratic mode. Under the conditions optimized using a mobile phase of 50% ACN containing 100mM of NaCl, the theoretical plate heights of the anions were within the range of 12.2–15.6μm (N, 64,000–82,000m−1; k, 0.2–1.6); and a value of 9.4μm (N, 110,000m−1) was achieved for t 0. The flow resistance of the column was acceptably low with a permeability of 2.7×10−13 m2. Fast gradient elution at a flow rate of 32mm/s resulted in rapid and precise separation of the inorganic anions of IO3 −, NO2 −, Br−, NO3 −, and I− within 20s. [Copyright &y& Elsevier]