INVESTIGATION AND COMPARISON OF THE ELECTROCHEMICAL-BEHAVIOR OF SOME ORGANIC AND BIOLOGICAL MOLECULES AT VARIOUS CONDUCTING POLYMER ELECTRODES

Electrodes modified by the electrodepozition of conducting organic pol ymers such as poly(3-methylthiophene)(PMT), polypyrrole (PPY) and poly aniline (PAN) were used as chemical sensors for voltammetric analysis and flow injection detection of some organic and biological molecules. The electrochemical behaviors of catechol, ascorbic acid, hydroquinon e, dopamine, epinephrine, acetaminophen and p-aminophenol were examine d by differential pulse voltammetry. The electrochemical behavior of t hese molecules at different electrodes was compared and the effects on behavior of electrolyte type and its pH and the film thickness were s ystematically examined. The results showed that the proposed modified surface catalyzes the oxidation of these compounds. Electrocatalytic ' efficiency' decreases in order of poly-3-methylthiophene, polypyrrole and polyaniline. Voltammetric peak positions were affected by the natu re of the electrolyte and its pH. Also, the effect of increasing film thickness was to observe increased peak heights. Polymer coated electr odes were also used in an amperometric detector for flow injection ana lysis of most of the these compounds. The responses of the polymer ele ctrode were 5-15 times larger as compared with those of bare platinum. PMT showed improved performance as an amperometric detector for flow injection analysis systems over other types of polymer electrodes. Det ection limits as low as 10(-8)-10(-9) M were achieved using the PMT, c ompared with 10(-6)-10(-8) M using platinum electrodes In the flow inj ection analysis, with increasing molecular weight of analyte molecules was to observe decreased peak heights. (C) 1997 Elsevier Science B.V.