The suitability of polymerised microemulsions as stationary phases for capillary electrochromatography

Abstract

Capillary electrochromatography (CEC) is an analytical separation technique, coupling the electroosmotic flow principles of capillary electrophoresis (CE) with the stationary phase separation principles of high performance liquid chromatography (HPLC). The development of this technique has been slowed due to technical problems with packing capillary columns. Alteration of the stationary phase to a solid monolithic support enables ease of filling and reduces bubble formation. Polymerisation of bicontinuous microemulsions can yield porous structures that are potentially suitable for use as a stationary phase for this technique. Polymerising bicontinuous microemulsions with different compositions produce monoliths of varying pore sizes. The microemulsions consist of a hydrophobic phase and an aqueous phase. The hydrophobic phase is typically methyl or butyl methacrylate, and a cross-linker, ethylene glycol dimethacrylate. The aqueous phase consists of water and a surfactant, typically sodium dodecyl sulfate. A short chain alcohol (C3-C5) is added as a porogen which also acts as a co-surfactant to aid with the stabilisation of the microemulsion. AMPS (2-acrylamido-2-methyl-l-propane sulfonic acid), added to the aqueous phase provides a charge along the polymer backbone essential for electroosmotic flow mechanism in electrochromatography. SEM analysis shows that polymerisation in-situ yields a structure with a porous topography. Materials prepared were assessed for suitability with a variety of microemulsion compositions.