Synthesis and characterization of novel stationary phases for small scale liquid chromatographic separations of proteins and nanoparticles

Graduation date: 2008The emerging field of nanotechnology strictly requires the micro-scaling of the available separation technology and the design of novel devices for separations of molecules of interest. The separation of proteins and nanoparticles is challenging due to their relatively large size, non-specific adherence to surfaces and instability in many solvents.\ud This dissertation presents the synthesis and characterization of novel stationary phases for use in separations of proteins or nanoparticles in both capillary and microchip formats.\ud In order to separate blood proteins with high specificity, a DNA aptamer selected for α-thrombin was employed as an affinity component of the stationary phases. Silica surfaces and organic monoliths were modified with the aptamer via an azlactone linkage and have demonstrated highly efficient separations of thrombin from a mixture in the microscale. The high efficiency of the protein separation (HETP = 276 μm, RS = 1.7) is comparable with macroscale results using antibodies as the affinity factor.\ud Novel hybrid inorganic-organic polysilsesquioxane stationary phases were synthesized by way of surfactant templated polymerization of bridged alcoxy-silyl ethane monomers, in presence of sodium hydroxide. The novel materials were successful in size exclusion separation of polystyrene standards with molecular diameters of 0.3-2.4 nm. A hybrid inorganic-organic polysilsesquioxane sorbent also proved useful for small scale separations of triphenyl phosphine protected gold nanoparticles, based on a sorptive mechanism instead of a size exclusion mechanism. Polysilsesquioxanes were easily synthesized in-situ inside fused silica capillary columns and PMMA microchip channels in order to facilitate integration with a micro-reactor.\ud The novel stationary phases proved efficient for separation of proteins and nanoparticles in the micro-scale format and can further be utilized for online purification and separation of these difficult compounds