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Title: Resolving multiple amperometric signals in the frequency domain
Author: Iyengar, S. G.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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This thesis applies immittance spectroscopy (IS) to resolve a "mixed" amperometric signal from two chemical species undergoing electro-oxidation at a single electrode, separating and quantifying the contribution of one or both of these species to the total measured signal. Traditional amperometric sensors base their mode of selectivity on the redox potential of the analyte and so are limited to samples where no other sample species is electroactive at the measuring potential. IS offers increased selectivity by utilising the kinetic and mechanistic information contained in the frequency domain. The methodology of IS is developed for the simultaneous detection of hydrogen peroxide and ascorbic acid because hydrogen peroxide cannot normally be oxidised without Faradaic interference from ascorbic acid in samples containing both. The theoretical basis for the origin of the ac response is considered and ac measurements are used to select information about one species or to determine individual signal fingerprints which identify those species that simultaneously contribute to the amperometric signal. The experimental parameters which may be altered to yield a desired spectrum are identified and selective detection of hydrogen peroxide are demonstrated. To determine both species simultaneously, the phase angles of their respective ac responses, given in terms of admittance, are used as fingerprints to quantify the amperometric signal from each; a matrix transformation is used to resolve the signal into its respective components to determine the concentration of each species. Finally, the phase angle detection method is extended to the case of the glucose biosensor, which uses the enzyme glucose oxidase to convert glucose to the amperometrically detectable hydrogen peroxide. This method allows for simultaneous measurement of glucose and ascorbic acid, overcoming transducer non-specificity and extending biosensor performance.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available