Amperometric detection of iron (III) on electroconductive hydrogel based on polypyrrole and alkoxysulfonated poly(3,4-ethylenedioxythiophene) (PEDOT-S)

A polymeric conducting hydrogel of autopolymerized polypyrrole (PPY) and poly(4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl-methoxy)-1-butanesulfonic acid (PEDOT-S) cast-deposited on a glassy carbon electrode is demonstrated to be an efficient electrocatalyst for the fairly irreversible, and often irreproducible, reduction of Fe(III) at the bare substrate. Sensitive amperometric monitoring of Fe(III) is then possible without the need for oxygen removal at the fairly positive polarization potential of 0.3 V vs. Ag/AgCl in acidic electrolyte (0.1 M HClO4). The sensor shows a linear current response over a concentration range exceeding two orders of magnitude (2.5–500 μM, R2 = 0.9998). The detection limit (3σ) was estimated to be 0.8 μM, and the sensitivity factor was 0.28 μA μM cm−2, which is approximately 23 times higher than for the unmodified electrode under the same experimental conditions.