Fabrication and characterization of nano-agglomerated monolithic stationary phases for separation science

摘要

The following thesis provides an extensive study into the fabrication, surface modification and physical characterisation of polymer monoliths in capillary formats. These polymer monoliths were subsequently immobilised with metal oxide nanoparticles for separation of phosphorylated compounds. The fabricated monolithic columns in capillary format, in all instances, were modified with diethylamine and subsequently immobilised with citrate stabilised iron oxide nanoparticles. The monolithic stationary phases were characterised using back pressure and sC4D measurements, which can provide information on the reproducibility and density of the stationary phase. Citrate stabilised iron oxide nanoparticles (Fe3O4 NP’s) with a particle size of 15.8 nm were electrostatically immobilised on a poly(butylmethacrylate-co-ethylene dimethacrylate) monolith bearing grafted functional polymer chains with quaternary amine groups resulting in homogeneous and high density coverage of iron oxide nanoparticles on the monolithic column demonstrated by FE-SEM images. The monolithic column immobilised with Fe3O4 nanoparticles was connected to a HPLC instrument and used in the separation of phosphorylated compounds such as adenosine, adenosine monophosphate, adenosine diphosphate and adenosine triphosphate using gradient elution. In a related study, commercially available centrifugally driven solid-phase extraction silica monoliths were immobilised with 15.8 nm citrate stabilised iron oxide nanoparticles with a dense coverage without detrimental blockage of the flow-through macropores. Since Fe3O4 is known to form reversible complexes with phosphorylated species, the silica monoliths were subsequently used for the enrichment of selected nucleotides and phosphorylated peptides.