Self-doped polyaniline modified electrodes were successfully fabricate
d 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 acti
vity with the formal potential of 50 mV in pH 7.0 buffer solution. Als
o, such 'self-doped' polyaniline was rather stable for a long-term use
. Ascorbate was electrocatalytically oxidized at these 'self-doped' po
lymer-modified electrodes. The effect of pH on the catalysis of ascorb
ate 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) mo
l L-1 (correlation coefficient 0.996).