A POTENTIOMETRIC IODIDE (AND OTHER) ION SENSOR-BASED ON A CONDUCTING POLYMER FILM ELECTRODE .2. EFFECT OF ELECTRODE CONDITIONING AND REGENERATION TECHNIQUES

A novel potentiometric halide sensor electrode for iodide, based on th e entrapment of iodide/iodine/triiodide into a poly(3-methylthiophene) conducting polymer, had previously been developed using a potentiosta tic technique for film formation. The effect of film thickness (with t he film thickness controlled by the amount of charge passing in the el ectrolytic cell during the polymerization) has been studied. Also, the effects of various pre- and postconditioning parameters on the electr ode performance and life time were examined and compared. The life tim e of the electrode was extended up to one year by storing its sensing tip in a newly designed cap. The cap consisted of two chambers linked with a special orifice; the first contained iodine adsorbed on silica or alumina and the second housed the electrode tip. The linear dynamic range of the new sensor electrode was 1 X 10(-7)-5 X 10(-1) M iodide and the detection limit was 1 X 10(-8) M iodide. The working temperatu re range, response time and working pH range of the electrode are 0-50 degrees C, 17-20 s and 2-11, respectively. The potential for bromide, chloride, and sulfite selective electrodes based on these conducting polymer films are also presented and compared to those obtained for io dide. Moreover, the effect of changing the type of conducting polymer using poly(3-methylthiophene), poly(N-methylpyrrole) or poly(aniline) are given and compared.