Conditioning treatment to improve the potentiometric pH response of polydiphenylamine modified electrodes

The potentiometric pH response of gold electrodes, modified with polydiphenylamine (PDPA) films was studied. These were obtained by electropolymerization of saturated diphenylamine in 3.7 M HClO4 solutions by cycling the working electrode potential between −0.10 and 0.65 V versus saturated calomel electrode (SCE). The PDPA modified electrodes were subjected to a conditioning treatment consisting of a sequence of electrochemical procedures performed in 1 M H2SO4 solutions. This treatment improves the linearity and sensitivity of the pH response and enlarges to 0 ≤ pH ≤ 11 the measuring range. The potential versus pH slope is 0.041 V/pH unit; this value is due to the fact that the conditioning treatment produces an effective pK distribution that is much wider that in the as made PDPA films.