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Title: Retention mechanism for reversed phase and hydrophilic interaction liquid chromatography : development and characterisation of modified silica particles
Author: Bailes, Sophie
Awarding Body: Open University
Current Institution: Open University
Date of Award: 2013
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Silanophilic interaction chromatography columns can give rise to complementary selectivity compared to the more commonly used hydrophobic interaction based HPLC columns. However, the former types of phase have historically caused issues of tailing and irreversible retention with polar or basic analytes. An investigation was therefore undertaken into the fundamental nature of their electrostatic, dipole-dipole and hydrogen bonding interactions. This was particularly focussed on interactions that are induced by the presence of residual silanols on the surface of HPLC phases, in order to fully understand the retention mechanism and the practical limitations of commercial stationary phases. Manufacturer's literature for these types of phase often contains specific applications and claims, however full independent testing of a range of acid, basic, phenolic, and polar compounds had not previously been demonstrated . Research in this area will aid in the development of new industrial applications by highlighting the stationary phase type with the most suitable mechanism to separate any combination of polar and non-polar compounds. Initial investigations evaluated silanophilic interactions present in a set of Extended Polar Selectivity (EPS) phases utilising a set of known characterisation probes. Structural elucidation of these phases confirmed the intensity of these interactions is due to the accessibility of the silanols and the purity of the base silica. Shorter chains and sparsely bonded hydrocarbon ligands were shown to reduce hindrance and increase the degree of interaction. Endcapping was shown to decrease the accessibility of residual silanols and mask silanophilic interactions. High purity base silica was shown to reduce silanophilic interactions compared to similar phases bonded to a TVPE-A silica. The control and restriction of silanophilic interactions is of great importance for the analysis of basic and polar molecules. Commercial TVPE-C™ phases are claimed to minimise silanophilic interactions through the " silanization" process. This converts the surface silanols to silica hydride prior to derivatisation with a functionalised ligand.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available