Ascorbate Amperometric Detection Using Conducting Copolymers Electrosynthetized

J. YANEZ HERAS; A. FORTE GIACOBONE; F. BATTAGLINI

Burdeos

Congreso; 11th International Conference on Electroanalysis; 2006

Society for Electroanalytical Chemisty

The electronic properties of polyaniline (PANI) can be reversibly controlled both by protonation and by changing the oxidation state of the polymer. These characteristics make this polymer almost unique for some applications. Among them are the construction of amperometric electrodes and molecular switches for the detection of analytes at low concentrations, particularly for its use in bioanalytical chemistry. However, the fact that PANI is redox-active only in acid conditions has prevented its wide use in this field, which generally requires a neutral pH environment. Different routes have been followed to overcome this drawback. One approach is to introduce acid groups into the PANI backbone and to form a so called “self-doped” PANI, which can maintain its electroactivity in neutral conditions. Another approach is to dope PANI with a negatively charged polyelectrolyte. As an example of bioanalytical application, the ascorbate detection using different PANI based electrodes has been presented (1-3), since the concentration of ascorbate can be used to assess the amount of stress in human as well as in plants (4,5). In this work, we present the polymerization of aniline and N-(3-propylsulfonic acid)aniline (PSA) in a sequential order, first the electropolymerization of aniline followed by the electropolymerization of PSA. The modified electrode obtained presents an improved electrochemical behavior at neutral pH compared with PANI modified electrodes. Also, the polymerization from a molar ratio of aniline:PSA = 9:1 is able to produce a modified electrode with improved properties with respect to polyaniline at neutral pH. The prepared modified electrodes are used for the construction of an amperometric sensor for the detection of ascorbate able to work at 25 mV vs Ag/AgCl with a linear response up to 2.5 mM in the case of the sequential electropolymerization. Effect of possible interferants, like dopamine and uric acid are discussed.