Currently, I have been conducting studies on monoliths with surface confined ionic liquid (SCIL) phases for liquid chromatography. My initial goals are to synthesize and characterize a SCIL based stationary phase on a monolithic silica support for liquid chromatography. One objective is to further explore the selectivity and retention mechanisms behind SCIL stationary phases for the separation of polar species in hydrophilic interaction liquid chromatography (HILIC). HILIC or aqueous normal phase chromatography is captivating attention in many fields, in particular pharmaceutical and biological sciences. In HILIC, a hydrophilic stationary phase is utilized for a separation where elution is achieved by a mainly non-polar mobile phase. The mobile phase contains a small percent of water or aqueous buffer. The analytes retained with this technique are mainly polar, hydrophilic compounds, either neutral or charged and they are eluted in increasing hydrophilicity. The reduction of complexity in sample mixtures that HILIC provides together with the fact that derivatization of highly polar analytes may be avoided makes the technique very attractive to diverse fields. In addition, the partly aqueous eluent with a high percent of acetonitrile (ACN) and a low amount of salt makes the technique ideal for mass spectrometry detection.
Also, I carried out studies on the enrichment of phosphorylated peptides using Group (IV) metal oxides, such as zirconia and hafnia. Analysis of phosphorylation in a given protein is challenging in part because of the low concentration of phosphorylated peptides and also because although major phosphorylation sites might be located easily, minor sites might be difficult to identify. We evaluated and compared the isolation and enrichment characteristics of monolithic materials of hafnia and zirconia towards phosphorylated peptides using a model protein, Beta-casein. Heat treatment of the metal oxides hafnia and zirconia materials seemed to be an influence in the selectivity towards singly and multi phosphorylated peptides. Hafnia, when treated to 1100°C, showed enrichment/isolation characteristics that are more selective than commercially available materials towards monophosphorylated peptides. On the other hand, zirconia material treated at 500°C showed to a large extent preferential enrichment for tetraphosphorylated peptides. Not only the in-house materials complement each other, they also suggest that tunable enrichment characteristics could be attained by using specific material heat treatments.
