Ascorbate sensor based on 'self-doped' polyaniline

Self-doped polyaniline modified electrodes were successfully fabricated by copolymerization of aniline and m-aminobenzoic acid in 0.5 mol L-1 sulfuric acid. The electrochemical characteristics of this resulting polymer were investigated. The polymer displayed electrochemical activity with the formal potential of 50 mV in pH 7.0 buffer solution. Also, such 'self-doped' polyaniline was rather stable for a long-term use. Ascorbate was electrocatalytically oxidized at these 'self-doped' polymer-modified electrodes. The effect of pH on the catalysis of ascorbate was explored. By constant potential method, such polymer was also deposited on a dual platinum disk electrode with a gap of 10 mu m. The dependence of the film conductivity on the potential, which showed a peak-shaped curve, was obtained. The device also showed a fast off-on response sensitive to ascorbate with a linearity up to 6.0 x 10(-3) mol L-1 (correlation coefficient 0.996).