Preparation and application of hydrophobic hybrid monolithic columns containing polyhedral oligomeric silsesquioxanes for capillary electrochromatography.
Hydrophobic organic-inorganic hybrid monolithic columns were synthesized via thermally initiated free radical polymerization with the confines of 75 μm id capillary using a polyhedral oligomeric silsesquioxane (POSS) reagent containing eight or more methacrylate groups as the crosslinker. Three organic functional monomers, butyl methacrylate (BuMA), lauryl methacrylate (LMA) and methacrylic acid (MAA), were selected and copolymerized with the POSS in the presence of 1-propanol and 1,4-butanediol to prepare the poly(POSS-co-BuMA), poly(POSS-co-LMA), and poly(POSS-co-MAA) monoliths, respectively. The 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) was copolymerized as ionizable monomer into the poly(POSS-co-BuMA) and poly(POSS-co-LMA) for the generation of EOF in capillary electrochromatography (CEC). A hybrid poly(POSS-co-LMA-co-MAA) monolith was also similarly prepared by copolymerizing ternary monomers of POSS, LMA, and MAA, and compared with poly(POSS-co-BuMA), poly(POSS-co-LMA), and poly(POSS-co-MAA) monoliths. The resulting four kinds of POSS-contained hybrid monoliths exhibited good permeability and mechanical stability. Their column efficiencies were evaluated by the separation of alkylbenzene homologues and polar compounds in CEC. The results indicated that the highest efficiencies of 194,100 and 102,100 theoretical plates per meter for thiourea and benzene were obtained on the poly(POSS-co-LMA-co-MAA) monolith. Additionally, the poly(POSS-co-LMA-co-MAA) monolith exhibited better selectivity for separation of polar compounds than those of other hybrid monoliths.