POTENTIOMETRIC IODIDE-ION SENSOR BASED ON A CONDUCTING POLY(3-METHYLTHIOPHENE) POLYMER FILM ELECTRODE

A potentiometric iodide-selective electrode based on a poly(3-methylthiophene) (PMeT) film was developed. Graphite electrodes were first coated with PMeT and then iodine was incorporated (doped) into the polymer film by electrochemical oxidation of iodide at +0.70 V. The effects of various electroactivation parameters such as doping potential, polymer film thickness, dopant concentration and doping period were examined in relation to the slope and linearity of calibration graphs. The performance of the electrode with respect to electrode reproducibility, response stability, appropriate pH range and response time was also examined. The polymer-based iodide-selective electrode was found to be suitable for the measurement of iodide concentrations down to 1 x 10(-6) M and its selectivity coefficients for most of the potential interferents were of the order of 1 x 10(-3). However, certain species that deplete the iodine in the polymer matrix adversely affected the electrode response.