en
Doctoral thesis
English

Exploring Novel Electrochemical Methods for Nitrate and Glucose Sensing

ContributorsDamala, Polyxeni
DirectorsBakker, Eric
Number of pages129
Imprimatur date2023
Defense date2023
Abstract

Accurate monitoring, whether it be in environmental, clinical, or other context, is a prerequisite for maintaining and enhancing the common wellness and functionality of our society. Successful monitoring is grounded in the use of reliable sensors which ensure that real-time data reflect -as much as possible- the actual conditions. Numerous aspects influence the performance of sensors, including -but not limited to- environmental conditions, engineering features, maintenance needs and more, often making the task of ensuring accurate sensing quite challenging. The goal of this thesis is to explore some of these issues and provide alternative methods that can serve as a foundation for developing better performing sensors, with a special focus on the environmental and clinical field.

Nitrate constitutes a major analyte in the environmental context mainly due to its increased presence in the water bodies following the misuse of fertilizers and inadequate management of water resources. Potentiometry offers a simple and easy way to monitor nitrate levels using nitrate selective electrodes that typically rely their function on ion-exchangers. Despite their widespread use, these sensors often lack the desired selectivity and present interfering issues due to the presence of other components found in water, such as chloride. To overcome this challenge, nitrate ionophores have been developed and commercialized, with the hope of providing the required selective characteristics. Even though several studies have dedicated their resources on these compounds, nitrate still remains one of the analytes lacking a selective ionophore that can outperform the existing ion-exchangers, as we demonstrate by testing two commercially available nitrate ionophores. Apart from the prerequisite of selectivity, a well performing ion-selective electrode (ISE) requires a conditioning step prior to its use. This is typically a time-consuming procedure and several strategies have been suggested for decreasing the required time of conditioning. In this work we propose a method for completely avoiding the need for conditioning while maintaining stable potentiometric readings using solid-contact ISEs.

Transitioning from the environmental to the clinical setting, glucose emerges as another key analyte that continues to attract considerable attention. Today, the goal is to measure glucose in-situ with minimally invasive sensors that are reliable and affordable, and in view of this trend, the research field has experienced a surge of newly developed sensors. The downside of this development is that often there is a tendency to prioritize the engineering facets, neglecting the understanding of the fundamental working principles behind glucose sensing. As we demonstrate here, these core issues need to be carefully examined and addressed to enable the implementation of continuously operating biosensors. The majority of glucose sensors currently work in amperometric mode. Despite their popularity, owing to their ease of use, amperometric sensors suffer from undesired high charging currents and ohmic contributions. To circumvent these limitations, in the last part of this work we present a time-dependent potentiometric glucose biosensor with a readout similar to that of chronopotentiometry.

eng
Keywords
  • Potentiometry
  • Nitrate ionophore
  • Ion-selective electrode
  • Solid-contact electrode
  • Glucose biosensor
  • Redox mediator
  • Nitrate
  • Glucose
Research group
Citation (ISO format)
DAMALA, Polyxeni. Exploring Novel Electrochemical Methods for Nitrate and Glucose Sensing. 2023. doi: 10.13097/archive-ouverte/unige:175929
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Thesis
accessLevelRestrictedaccessLevelPublic 01/01/2025
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