Silica-particle-supported C18 Polymeric Monolithic Column For Capillary Liquid Chromatography

Firstly,a silica-particle-supported C18 polymeric monolithic column,shortened as the supported column,was prepared by in-situ polymerization of stearyl methacrylate(SMA,functional monomer)and ethylene dimethacrylate(EDMA,cross-linker)at the presence of a binary porogenic solvent consisting of methanol and cyclohexanol in a 150 μm i.d.fused silica capillary pre-packed with 5μm ODS silica particles.To be sure that the organic polymers were formed just on the ODS silica particle surface,leaving the interstitial space between the particles free for liquid flow,the conditions for preparation of the supported column were examined based on SEM images and pressure-vs-flowrate curves.The selected conditions were as follows:type of particles,ODS silica particles;volumetric ratio of methanol to cyclohexanol,6:4;total monomer concentration,22.5%(C%= 25%);polymerization time,5 h;polymerization temperature,60℃.Then,the prepared column was evaluated in terms of mechanical properties and chromatographic performance by comparing with C18 organic polymer monolithic column(shortened as organic column)and the ODS particle packed column(shortened as packed column).The results demonstrated that the supported column has the advantages of no need of retaining frits,possibility of cutting at any desired length over the packed column,and is superior to the organic column in uniformity of pore size,mechanical stability,resistance to swelling-shrinking and loading capacity.In comparison with the methods reported previously,the presented approach to hybrid columns has the merits of simplicity of procedure,ease of controlling experimental conditions,better reproducibility and stability.More importantly,presented approach can be adapted to other organic polymers in addition to the C18 polymers for preparation of various hybrid columns.Finally,a baseline separation of a mixture consisting of benzene and its derivatives was achieved on a short section of the supported column within a 2 min period,illustrating that the column is of hydrophobic retention mechanism and high column efficiency.