A solid state Cr(VI) ion-selective electrode based on polypyrrole

We report on a graphite electrode onto which polypyrrole was electrodeposited and then doped with chromate ion. This electrode can serve as a Cr(VI)-selective solid-state electrode. Electropolymerization of pyrrole was performed potentiostatically at 0.80 V (vs. SCE) using battery graphite as the working electrode in a solution containing 0.10 M of pyrrole and 20 mM of chromate. A platinum wire was used as an auxiliary electrode. The new electrode displays high selectivity, a very wide dynamic range, a sufficiently fast response time and a good shelf lifetime. It shows a linear Nernstian response over 1.0 × 10−6 to 1.0 × 10−1 M concentration range (with a slope of 26.55 ± 0.20 mV per log of concentration). The detection limit is 0.5 μM, and the pH optimum is 7.0.