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
