Yang, Yejin
(2022)
Improving Electrochemical Detection in Capillary Liquid Chromatography.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Our group has monitored dopamine using microdialysis (MD)-capillary high performance liquid chromatography (CLC) coupled to an electrochemical (EC) detector. To improve electrochemical detection of dopamine in this MD-HPLC-EC system, the electrochemical analysis methods are suggested in this study. Specifically, three strategies are employed to reduce the sloping background current, enhance the signal, and analyze the dead volume of the electrochemical detector.
Fourier transform sine-wave voltammetry (FT-SWV) can be a solution for the high sloping background current, resulting in an improved signal-to-background ratio (SBR). We comprehensively investigated the effect of voltammetric parameters: amplitude, dc bias potential, and excitation frequency of the sine waveform on background, signal, and SBR, as well as linearity with respect to the concentration of an analyte. We demonstrated that the dc bias potential can be used to adjust the phase angle difference between the signal and background to obtain out-of-phase background, leading to significant improvement in SBR.
A microelectrode array can also provide high SBR in the flow cell. By employing photolithography and pyrolysis, pyrolyzed microelectrode array (PMA) for HPLC flow cells were fabricated. The highest coverage PMA-3 (9%) showed a great reduction in slope of the background current slop and high sensitivity, indicating a promising electrode for the MD-HPLC-EC wall-jet flow cell. The simulation result of concentration gradient inside the wall-jet flow cell indicated that in the future, the PMA pattern can be designed to utilize the thin diffusion layer of the analyte and exploit the edge effect of the microelectrode.
It is also important to analyze and predict the dead volume of the flow cell to avoid separation efficiency reduction. We quantified the dead volume and the effective radius of the electrochemical flow cell using a stirred-tank model with various thicknesses of gaskets. The thicker gaskets result in an increase in the dead volume and a rapid decrease in the effective radius, leading to degraded peak shape and decreased column efficiency. Concentration simulation showed that wall-jet configuration affects the effective radius, ultimately the dead volume of the flow cell.
Share
| Citation/Export: |
|
| Social Networking: |
|
Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
13 August 2022 |
| Date Type: |
Publication |
| Defense Date: |
3 August 2022 |
| Approval Date: |
4 December 2024 |
| Submission Date: |
5 August 2022 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
101 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Fourier Transform Sine Wave Voltammetry, Microelectrode Array, Dead Volume of Wall-Jet Flow Cell |
| Date Deposited: |
04 Dec 2024 16:56 |
| Last Modified: |
04 Dec 2024 18:07 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/43536 |
Metrics
Monthly Views for the past 3 years
Plum Analytics
Actions (login required)
 |
View Item |
![[feed]](/images/feed-icon-32x32.png){kind=icon}