Development of a three-electrode cell containing a polypyrrole coated auxiliary electrode

A three-electrode, flow through cell was manufactured. The system contained an auxiliary electrode coated with oxidized polypyrrole. The conducting polymer is believed to function both as a reduction reserve and as an electrode surface expander. The three-electrode cell was used for an electrochemical analysis, employing electrochemical oxidation at +500 mV versus an Ag/AgCl reference electrode, of morphine in the concentration range 0-8 mg/l. The sensitivity was 0.5 nA/(mg/L). Comparisons were done between polypyrrole coated and non-coated auxiliary electrodes. It was found that the use of a polypyrrole coating gave an increased linear range (from 0-2 mg/L to 0-8 mg/L) and a reduced current noise (>6 times) which should give lower detection limits. The repeatability of the measurements was found to be 1.9 % (n=5) and the reproducibility to be 6.1 % (n=5). The possibility of contamination occurring in the electrolyte solution is reduced in this system, which is another advantage of using the polypyrrole, due to the fact that the conducting polymer is acting as a well defined rapid solid state redoxcouple. Thus, this work clearly demonstrates the feasibility of applying a conducting polymer coating onto auxiliary electrodes in order to improve electrochemical characteristics of a three-electrode cell.