Adrenaline In The Electron Transfer Properties Of Polyaniline Modified Electrode,

The chemically modified electrodes have been a most burgeoning and one of the most flourish research realms in the electrochemistry and electroanalytic chemistry. It was for the moment widely applied in many cases such as life sciences, environmental science, analytic science and material science. Because polyaniline (PAn) film has a unique doping behavior and good electrochemical reversibility, a lot of research of Pan-film modified electrode in the analysis and testing has been conducted. Epinephrine is an important catecholamine neurotransmitter in mammalian central nervous system, which plays a particularly important role in the biology action and nervous chemical processes in nervous system. So, electrochemical studies of epinephrine and analogies have an important role in biological samples. In this paper glassy carbon electrode modified with a polyaniline membrane was employed for the electrocatalytic oxidation of epinephrine,aiming at broadening the adrenaline in the modified electrode and the application of electrochemical detection field.In this paper, choosing EP probe, several factors affecting the electrocatalytic oxidation have been investigated. By using cyclic voltammetry, optimum condition for PAn preparation is estimated: the upper scanning potential of cyclic voltammetry is 0.95V, the lower scanning potential is -0.2V, the concentration of the acid medium HCl is 2.0 mol/L, the concentration of aniline is 0.5 mol/L, scanning rate is 50mV/s. The behaviors of this PAn modified electrode was studied by cyclic voltammetry in HCl and KCl buffer solution. Results indicated that the PAn modified electrode has good conductivity.The behaviors of epinephrine on this modified electrode was studied by cyclic voltammetry in the eight kinds of medium including 1.0 mol/L HCl solution , HClO₄ solution , H₃PO₄ solution , HNO₃ solution , H₂SO₄ solution, HCl and KCl buffer solution , McIlvaine buffer solution and BR buffer solution . The PAn modified electrode shows excellent electrocatalytic activity for oxidation of epinephrine. The film of PAn may protect electroactives of the modified electrode. The PAn modified electrode shows high sensitivity in determination of epinephrine. The relationship between i_pa of EP and v^1/2 is linear. The results indicate that the electron transfer process of epinephrine on this modified electrode is controlled by diffusion .The linear relationship between the peak current and concentration is observed for epinephrine with in the range of 2.5×10^-5 mol/L～1.6×10^-4 mol/L, implying that the PAn film electrodes have a potential application in the qualitative or quantitative analysis of epinephrine.The electrocatalytic activity of EP was studied by Electrochemical Impedance Spectroscopy at the polyaniline-modified glassy carbon electrode in HCl and KCl solution. The experimental results show that, with the increasing concentration of hydrochloric acid solution, the charge transfer resistance of the polyaniline membrane is getting smaller and smaller, and charge transfer accelerate; The results indicate that the electron transfer process of EP is controlled by diffusion , which is similar to that of by cyclic voltammetry. Polyaniline modified electrode can reduce EP of polarization resistance of electrochemical oxidation.In order to contrast with EP, the behavior of catechol at this modified electrode was also studied by cyclic voltammetry in HCl and KCl solution. The modified electrode shows excellent electrocatalytic activity for oxidation of catechol as well as epinephrine, but the peak current of epinephrine is significantly smaller than that of catechol, because amidocyanogen of epinephrine with positive electricity weakens the adsorption at the modified electrode. The reaction mechanism of electrochemical oxidation of PAn has been put forward. We proposed that the electron transfer process of epinephrine at the PAn modified electrode is two consecutive single-electron transition processes. The catalysis of polyaniline membrane is synergy and coupling of chemical catalysis and transfer catalysis.