Semi-circular sweep voltammetry for electroanalysis

This thesis focuses on electroanalysis using semi-circular sweep voltammetry. This method is particularly developed for analytes which show significant difficulties when analysed using conventional voltammetry.
The fundamentals of electrochemistry and the principles of electrochemical methods are introduced in Chapter 1. Next, the theoretical aspects of semi-circular sweep voltammetry and the insights from related simulation studies are reviewed in Chapter 2. In Chapter 3, the generic experimental procedures used widely in the following chapters are described.
In the chapters, from Chapter 4 to Chapter 9, new, bespoke electrochemical methods for the detection of a range of target molecules are introduced with the focus on the electroanalytical applications of semi-circular sweep voltammetry the generation of new methodology for wider application. Chapter 4 considers the detection of the analyte piperine allowing comparative evaluation of semi-circular sweep voltammetry. In this chapter, the electrochemical behaviour of piperine at macro-and micro-electrodes are discussed. Semi-circular sweep voltammetry is used to maximise the analytical signal shown under conditions where high capacitive and solvent currents were present. The suggested electroanalytical method is validated in real samples following the establishment of a quick and simple improved extraction procedure of piperine from black pepper.
The electro-oxidation of phenol causes electrode passivation via electro-polymerisation making meaningful electroanalysis impossible. Chapter 6 investigates the passivating behaviour and develops an electroanalytical method for determining phenol using semi-circular sweep voltammetry by means of the introduction of a second species which reacts with phenol largely eliminating electro-polymerisation. The presence of the second species prevents the passivation at low phenol concentrations and the semi-circular sweep voltammetry amplifies the signal from the unreacted phenol in the low concentration range.
In Chapter 5 and 7, the merits of using semi-circular sweep voltammetry for the selective detection of one or other component of a mixture containing two components with closely similar potentials which preclude their resolution in conventional voltammetry are discussed. Chapter 5 demonstrates proof of concept of the developed approach applying semi-circular sweep voltammetry for distinguishing and quantifying chlorophyll a and chlorophyll b in their mixtures and is then applied to real samples. Chapter 7 suggests the generic applicability of semi-circular sweep voltammetry and its advantages over other analytical voltammetry in terms of the voltammetric resolution and sensitivity of detection. The electrochemical reaction processes and the analytical indications are investigated specifically in the cases of biological mixtures of ascorbic acid and acetaminophen, glucose and ethanol, and hydroquinone and catechol.
Finally, Chapter 8 focuses on another important technique for – adsorptive stripping voltammetry and discusses the intrinsic limitations in the practical voltammetric detections. The possibility of employing semi-circular sweep voltammetry to overcome such limitations is also explored in this Chapter.

Keywords: Selectivity
Semi-circular Sweep Voltammetry
Sensitivity
Electrochemical Detection
Advisor: Compton, R