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Electrochemical detection optimized for capillary liquid chromatographic determination of neuroactive compounds

Xu, Xiaomi (2012) Electrochemical detection optimized for capillary liquid chromatographic determination of neuroactive compounds. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Analyzing microdialysates sampled from the brain area of interest using HPLC is the most popular method among neuroscientists to measure extracellular neurotransmitters. An optimized capillary UHPLC-ECD system is capable of measuring basal concentration of serotonin in microdialysis samples and can be coupled with microdialysis to for on-line measurements. Due to the low abundance of some neurochemicals and the complex nature of biological matrices, the detection method has to be sensitive and selective and needs to be optimized.
Miniaturization of the electrochemical flow cell detector is critical to improving the sensitivity especially in a capillary separation system. Fabricating the spacer in the flow cell using a novel photosensitive polymer coating offers the convenience of controllable thickness and easy assembling, which leads to improvement in detector performance. The advantage of the thin polymer coating as the spacer is demonstrated by comparing the performance with that of a traditional free standing spacer. A dual working electrode electrochemical detector increases detection selectivity based on the difference in the electrochemical reversibility of analytes. Carbon fiber/epoxy composite materials are commercially available in various shapes and sizes at very low cost. Using tube and rod composites, a ring-disk electrode with a 20 µm gap between the ring and the disk is successfully fabricated through a unique two-step insulation-adhesion process. The narrow gap is favorable for mass transfer in the generator-collector experiment. When assembled in an electrochemical radial-flow cell detector, the dual electrode gives high collection efficiency (0.8 for a chemically reversible species), which enhances the detection selectivity. Carbon electrodes can also be replaced with naphthalenethiol modified gold electrodes. The modification monolayer suppresses the background current from Au while giving detectable current for biological analytes with sensitivity comparable to a glassy carbon electrode.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Xu, Xiaomixix11@pitt.eduXIX11
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairWeber, Stephensweber@pitt.eduSWEBER
Committee MemberMichael, Adrianamichael@pitt.eduAMICHAEL
Committee MemberAmemiya, Shigeruamemiya@pitt.eduAMEMIYA
Committee MemberKitchin,
Date: 1 February 2012
Date Type: Publication
Defense Date: 10 November 2011
Approval Date: 1 February 2012
Submission Date: 14 November 2011
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 137
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: Neurotransmitters, Capillary HPLC, Electrochemical detection, optimization
Date Deposited: 01 Feb 2012 16:03
Last Modified: 15 Nov 2016 13:55


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