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Electropolymerization of methylene green on gold and platinum electrodes for ascorbic acid determination

Agnieszka Kossakowska ,  Dorota G. Pijanowska ,  Jerzy Kruk ,  Władysław Torbicz 

Polish Academy of Sciences, Institute of Biocybernetics and Biomedical Engineering (IBBE PAS), Trojdena 4, Warszawa 02-109, Poland

Abstract

In this paper, results concerning application of a phenothiazine dye - methylene green (MG) as a sensing membrane for amperometric sensors are presented. The MG can act as an electron transfer mediator and reduce the oxidation overpotential of some biologically important compounds.

The MG was electropolymerized on gold and platinum electrodes. The three electrode electrochemical cell consisted of working electrode (WE) of 3.75 mm2 area, a reference electrode - saturated calomel electrode and a counter one - platinum rod. The electropolymerization was carried out in 1 mM MG/0.1 M KCl solution using a cyclic voltammetry technique: 30 sweeps in potential range from -0.6 V to +1.4 V with scan rate 100 mV/s.

Obtained thin films of poly(methylene green) (PMG) were compared using scanning electron microscopy. It was found that on platinum WE very thin, non-uniform and untight layers were deposited. Electrochemical tests by cyclic voltammetry in potential range from -0.8 V to +0.8 V, starting and finishing at 0.0 V, with scan rate 100 mV/s in 0.1 M KCl solution shown voltammograms of different shape, stability and reproducibility, depending on type of the bare working electrode material used.

Finally, the gold and platinum electrodes modified with PMG were used for the determination of ascorbic acid in concentration range from 1 mM to 20 mM. In case of the platinum WE modified with PMG, the sensitivity to ascorbic acid become worse, while in the case of the gold electrodes sensitivity increased and a reduction peak has appeared.

Summarizing, covering the gold electrode with PMG film makes the electrode sensitive to ascorbic acid. Such modified electrodes can be used in immunoassays with antybodies labelled with alkaline phosphate which uses ascorbic acid phosphate as a substrate. The future research will be oriented towards increase the selectivity to ascorbic acid.

This research is financially supported by Ministry of Science and Higher Education (Grant No. N N518 0926 33).

 

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Presentation: Oral at E-MRS Fall Meeting 2009, Symposium F, by Agnieszka Kossakowska
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-25 21:28
Revised:   2009-07-14 09:29