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Title: In-column electrochemical detection for liquid chromatography
Author: Leow, Pei Ling
ISNI:       0000 0004 2682 8287
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2009
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This research focuses on the development of whole column detection (WCD) for liquid chromatography (LC). The WCD uses electrochemical techniques for detecting the analytes passing through the separation column. Electrode array for in-column electrochemical detection (ICED) is fabricated along the separation column to enable whole column separation monitoring and allow better understanding on the affinity of particular analyte to the stationary and mobile phases. Numerical models were built to understand the feasibility and differences of electrochemical detection within an unpacked and packed column. From the simulated results, the surface area of the electrode was not hindered by the presence of the particles in flow condition. An electrochemical microfluidic device has been successfully fabricated on PET (polyethylene terephthalate) substrate using the reverse imprinting technique. The photolithographically produced gold metal electrode lines were imprinted into the PET substrate using a blank mould and produced an inlaid electrode array with overall step residue within 40 nm. The semi-cured thermoset polyester channel was irreversibly thermal bonded on the PET substrate. The devices were able to tolerate pressure in excess of 90 bars. The PET column was packed with 5 μm C18 silica beads to perform reverse phase chromatography separation. The array was electrochemically characterised using standard redox probes in both stagnant conditions and under flow. Both numerical modelling and experimental data show improved sensitivity under flow and a limiting current which scaled linearly with cubic root of volume flow rate. Isocratic and gradient mode chromatographic separations of neurotransmitters and metabolites: serotonin, dopamine, adrenaline, 5- HIAA and DOPAC were conducted in the fabricated device. Separation progress was electrochemically detected at multiple locations along the column. Whole column assessment on separation efficiency and column packing efficiency monitoring were conducted using the ICED.
Supervisor: O'Hare, Danny Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral