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

• Polypyrrole/PEDOT-S composite conducting gel shows appreciable electrochemical activity in acidic aqueous electrolyte.
• The gel effectively preconcentrates cationic species.
• The gel modified electrode can be used for sensitive amperometric detection of trivalent iron ions.

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.

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