Amperometric sensing of nitrite based on electroactive ferricyanide–poly(diallyldimethylammonium)–alginate composite film

Poly(diallyldimethylammonium chloride) (PDDA) and sodium alginate (AlgNa) were mixed to obtain a water-insoluble interpenetrating polymer composite via electrostatic interaction and then cast on an Au electrode surface, followed by robust immobilization of K3Fe(CN)6 to yield a K3Fe(CN)6–PDDA–Alg/Au electrode of stable electroactivity. The interaction processes and electrode modification are studied by visual inspection and electrochemical methods. Under optimized conditions, the K3Fe(CN)6–PDDA–Alg/Au electrode can efficiently electrocatalyze the reduction of nitrite in acidic aqueous solution and give a linear nitrite-detection range of 5.0 μM to 9.7 mM with a sensitivity of 83.7 μA cm−2 mM−1, which is amongst the best results reported for nitrite sensing. The electrode was also used for nitrite electroanalysis in real sample matrices with satisfactory results.