Issues related to the development and application of electrochemically modulated liquid chromatography (EMLC)

Lin, Bin
Major Professor
Marc D. Porter
Committee Member
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This dissertation presents two topics centered on electrochemically modulated liquid chromatography. The first topic continues our ongoing investigations on the modification of the surfaces of glassy carbon electrodes (GCEs) by the electrooxidation of amine-containing compounds. The method utilizes the electrooxidation of amines to form a chemically stable covalent linkage between the nitrogen atom of the amine and the carbon surface. The first section on this topic investigates a method for the fabrication of redox surfaces on GCEs by linkages with amine-containing compounds (i.e., dopamine). This work focuses specifically on issues related to the preparation of coatings with a high coverage. Results show that the use of a high pH and metal ion complexation, which drives the amine to its deprotonated form and protects the catechol group of dopamine by its complexation with Co (II), enhances the coverage and stability of the resulting coating. The second section on this topic devises a strategy to immobilize secondary and tertiary amines on GCEs. To implement this strategy, the correlation between the surface coverage of amines and surface oxides was studied. In addition, we explored the feasibility of utilizing this strategy to create reversed-phase architectures on the carbon materials. It was found that the wetting properties of modified GCE surfaces were dependent on the chain length of alkylamine. The resulting electrode surfaces showed high hydrophobicity and excellent chemical stability in strong acid and strong base, demonstrating the potential viability of the alkylamine-modified carbons as a new class of reversed-phase materials for liquid chromatography. The second topic investigates the EMLC-based applications to two important classes of biogenic aminescatecholamines and indoleamines. The capability of EMLC to facilitate the separation of catecholamines and indoleamines are demonstrated. The aim of this study is to explore the feasibility of using EMLC for the separation of these classes of compounds, forming the foundation for future applications of EMLC in analyzing biological materials.