School of Chemical Sciences

Sensing Oxidants and Antioxidants

Contact researcher: Assoc. Prof. Paul Kilmartin

Polyphenol and other small molecule antioxidants can be characterised very effectively using glassy carbon electrodes, and methods have been developed at the University of Auckland to quantify the antioxidant capacity of beverages, plant extracts and biological fluids. Additional specificity for particular antioxidants, such as ascorbic acid and bisulfite, has been introduced through the use of conducting polymers as redox mediators.

Cyclic voltammetry at glassy carbon

Following earlier demonstrations that the polyphenol content of wines, teas, plant and food extracts can be characterised using cyclic voltmmetry, current projects include the monitoring of the antioxidant status in animal studies of acute pancreatits and further medical conditions (Anubhav Mittal - PhD in conjunction with Dr Anthony Phillips, Prof. John Windsor and Prof. Garth Cooper (School of Medicine)). The cyclic voltammetry method is also being extended to examine the interaction of wine polyphenols with antioxidant additives with implications for improving the stability of white wines (Olga Makhotkina - PhD). Recently the polyphenol and ascorbic acid content in various fruit juices was assessed using cyclic voltammetry (Azahari Nor Azieda - summer student project 08/09).

Two research students standing in their office
Olga Makhotkina and Olga Mednova in the electrochemistry laboratory

Conducting polymer redox mediators

The overpotential for ascorbic acid oxidation can be lowered through the use of forms of polyaniline which are electroactive in neutral pH buffers (In collaboration with Prof Philip Bartlett, University of Southampton). A range of nanostructured conducting polymer materials, cast upon inert electrodes, including polyaniline nanotubes covered with PEDOT, and poly(methoxyaniline) nanospheres are proving even more effective for constructing ascorbic acid sensing elements (Dr Lijuan Zhang and Jing Sui - PhD).

Electrode arrays - the electronic tongue

In 2008 a research student, Olga Mednova, along with Dr Dmitry Kirsanov visited from the research group of Dr Andrey Legin at the University of St Petersburg involved in the development of ‘electronic tongue’ sensor arrays for wine components. The focus of Olga’s project was to construct an array device which can measure SO2 concentrations in wines, and a working prototype was successfully achieved.

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Recent publications

  • O. Makhotkina and P.A. Kilmartin, "The Use of Cyclic Voltammetry for Wine Analysis: Determination of Polyphenols and Free Sulfur Dioxide", Analytica Chimica Acta 668 (2010) 155-165.
  • A. Mittal, G. Friederike, B. Loveday, N. Thompson, B. Delahunt, P.A. Kilmartin, G.J.S. Cooper, J.A. Windsor and A.R.J. Phillips, "The redox status of experimental haemorrhagic shock as measured by cyclic voltammetry", Shock 33 (2010) 460-466.
  • J. Sui, L. Zhang, J. Travas-Sejdic and P.A. Kilmartin, "Synthesis of Poly(3,4-ethylenedioxythiophene) hollow spheres in CTAB/DBS - mixed surfactant solutions", Macromolecular Symposia 290 (2010) 107-114.
  • L. Zhang, H. Peng, J. Sui, C. Soeller, P.A. Kilmartin and J. Travas-Sejdic, "Self-assembly of poly(o-methoxyaniline) hollow microspheres", Journal of Physical Chemistry C 113 (2009) 9128-9134.
  • O. Makhotkina and P.A. Kilmartin, "Uncovering the influence of antioxidants on polyphenol oxidation in wines using an electrochemical method: cyclic voltammetry", Journal of Electroanalytical Chemistry 633 (2009) 165-174.
  • O. Mednova, D. Kirsanov, A. Rudnitskaya, P. Kilmartin, A. Legin, "Application of a potentiometric electronic tongue for the determination of free SO2 and other analytical parameters in white wines from New Zealand", AIP Conference Proceedings 1137 (13th International Symposium on Olfaction and Electronic Nose), p. 263-266.
  • L. Zhang, H. Peng, P.A. Kilmartin, C. Soeller and J. Travas-Sejdic, "Poly(3,4-ethylenedioxythiophene) and polyaniline bilayer nanostructures with high conductivity and electro-catalytic activity", Macromolecules 41 (2008) 7671-7678.
  • A. Mittal, R.J. Fint, M. Fanous, B. Delahunt, P.A. Kilmartin, G.J.S. Cooper, J.A. Windsor and A. Phillips, "The antioxidant status of an inflammatory disease as measured by cyclic voltammetry: initial rodent studies to assess the severity of acute pancreatitis", Critical Care Medicine 36 (2008) 866-872.
  • D. Sun-Waterhouse, L.D. Melton, C.J. O’Connor, P.A. Kilmartin and B.G. Smith, "Effect of apple cell walls and their extracts on the activity of dietary antioxidants", Journal of Agricultural and Food Chemistry 56 (2008) 289-295.
  • P.A. Kilmartin, A. Martinez and P.N. Bartlett, "Polyaniline-based microelectrodes for sensing ascorbic acid in beverages", Current Applied Physics 8 (2008) 320-323.