The application of carbon composite electrodes for the analysis of environmental and biological pathogens
Date
2023
Authors
McMahon, Catherine J., author
Henry, Charles S., advisor
Prieto, Amy L., committee member
Farmer, Delphine, committee member
Geiss, Brian, committee member
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Volume Title
Abstract
Fast, reliable, and accurate detection of heavy metals is crucial in preventing adverse health effects. Heavy metal contamination comes from various human anthropological endeavors, and can leach into water, food, and consumer products such as cosmetics. Electrochemical detection of heavy metals has become a popular alternative to traditional analysis, using highly sensitive spectroscopic techniques. Carbon composite electrodes have been used for electrochemical sensors due to their chemical inertness, large potential window, and resistance to fouling. However, they can often suffer from poor electrocatalytic behavior, resulting in the need for extensive surface modifications. Moreover, traditional carbon composite electrodes have been limited in their pattern-ability and difficultly in fabrication. Thermoplastic electrodes were developed in 2017 to address these needs and are further discussed and characterized in this dissertation for applications towards heavy metal analysis. Overall, this dissertation seeks to use carbon composite electrodes to improve detection efforts for both environmental pollutants (i.e heavy metals) and biological analytes. Chapter 2 introduces the use of stencil-printed carbon electrodes (SPCEs) for the analysis of heavy metals in cosmetic samples from Nepal, Ghana, and Uganda. The approach utilizes a previously developed method and adapts it, expanding its utility. The goal of the work is to develop a method that is capable of screening for heavy metal pollutants outside of traditional laboratory settings. An alternative sample extraction approach is detailed as well as the development of a laboratory standard for heavy metal analysis in cosmetics. In addition to the electrochemical analysis, extensive analysis using inductively coupled plasma optical emission spectroscopy is conducted on the cosmetics samples, to better understand the Pb contamination and matrix complexity of the samples. Chapter 3 focuses on the use of TPEs for the detection of heavy metals. Six formulations of TPEs, with different graphites and polymer binders, are characterized to better understand how the unique surface properties impact the analysis of heavy metals. The detection of Pb is used as a proof-of-concept model. The results illustrate that both the polymer and graphite can have intensive impact on the application of TPEs. Of the various formulations tested, polystyrene and polymethyl methacrylate show promise in detecting heavy metals within relevant ranges. Chapter 4 pivots from heavy metal analysis and investigates the use of SPCEs for the detection of SARS-CoV-2 nucleocapsid protein. With the onset of the COVID-19 pandemic in 2020, my research focus pivoted to address the need to develop reliable, accurate, and fast point-of-care diagnostics for SARS-CoV-2 to help manage the spread of the virus. SPCEs are modified based on an ELISA (enzyme-linked immunosorbent assay) for the electrochemical detection of the N-protein. The assay developed sets the framework for a potential POC diagnostic, while meeting the industry need for fewer false negatives and lower limits of detection. In summary, this dissertation seeks to implement and expand the utility of different kinds of carbon composite electrodes for the detection of heavy metals and biological analytes. The work described in this dissertation sets the framework for improving upon carbon-based electrochemical sensors for environmental and biological sensors. This work provides materials, methods, and fundamental characterization of carbon composite electrodes, and how different surface treatments and modifications can expand their utility in electrochemically sensing applications.
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Subject
cosmetics
thermoplastic electrodes
COVID-19
carbon electrodes