Nitrate ion-selective sensor based on electrochemically prepared conducting polypyrrole films

Nitrate-doped polypyrrole (PPy) films on a glassy carbon substrate have been prepared electrochemically in aqueous, acetonitrile, and propylene carbonate solutions for use as nitrate sensors. Lithium nitrate, sodium nitrate, nitric acid, tetraethylammonium p-toluene sulfonate (TS), and tetradodecylammonium nitrate (TDN) were employed as electrolytes. The effect of dibutylphthalate (DBP) as a plasticizer on the sensitivity and lifetime of PPy film sensors was also investigated. A Nernstian behavior with a slope of 56.9 mV/decade over 0.1-7.4x 10(-5) M NO3- and a detection limit of 4.7 x 10(-5) M were observed for the polymer sensor prepared in acetonitrile solution containing lithium nitrate and 15% plasticizer (DBP). A lifetime of more than 6 months for this PPy film electrode was obtained.