III International Conference

PP-III-4inserted in PAn either in the course of electrosynthesis or using the subsequent impregnationof the polymer in the mediator solution. It is important for a long operating CME that thecontent of the immobilized mediator would remain constant. This is, to a great extent,provided by the formation of chemical bonds between a mediator and a polymer. We showedthat ABTS 3 and HCI 4 form stable complexes with aniline. The complexes were isolated andcharacterized by elemental and IR analyses. Therefore, one could expect that such mediatorswould be fixed in PAn due to the formation of chemical bonds with a polymer and, hence, themain condition for stable operation of the sensor will be met. All the CME were tested for thedetermination of concentrations of antioxidants at +0.7 V (Ag/AgCl) electrode potential. Atthis potential, as it derives from the experimental data, Ir is in +4 oxidation state and ABTS isin the radical cation form. As a result of the reaction with the antioxidant, Ir is reduced to the+3 oxidation state and ABTS is reduced to a neutral form. At +0.7 V they are oxidized to Ir +4and ABTS + . Then the cycle is repeated untill the antioxidant is consumed. It should be notedthat an amperometric response to different concentrations of antioxidants is demonstrated bypure (without a mediator) PAN as well, though this response is noticeably weaker. The roleand the necessity of a mediator in the structure of a sensor were studied during a long-termobservation of three type sensors: 1) PAn; 2) PAn-ABTS; 3) PAN- IrCI 2- 6 . The sensors werestored in air for a year and their activity was controlled periodically. Ascorbic acid was usedas a reference compound. Each time a new 6х10 –3 M solution of ascorbic acid was preparedand sensor activity was tested. The data are presented in Fig.1:The most stable sensor was found to be thatbased on PAn- IrCI 2- 6 , and the sensor based on purePAn demonstrated only 14% of its initial activity bythe 300 th day. These data are evidence of that themediator introduced in the sensor structure canperform not only as an active component butessetially stabilizes the performance of the sensor.References1. Miller N. Rice-Evans C.A. Redox Report. 1996 №2, C161.2. Abalyaeva V.V. Efimov O.N. Polymer for Edvanced Technologies, 1997, V.8, P.517.3. V.V.Abalyaeva, O.N.Efimov. Elektrokhimiya (Electrochemistry) (in Russian), 2002, V.38, N10,P.1212.4. V.V.Abalyaeva, O.N.Efimov. Elektrokhimiya (Electrochemistry) (in Russian) 2005, V.41, N11,P.1323.477