Electrocatalysis and Determination of Ascorbic Acid Through Graphite Paste Electrode Modified With Iron Nitroprusside

 

Devaney R. do Carmo, Ricardo M. da Silva, Nelson R. Stradiotto*

Instituto de Química, Universidade Estadual Paulista (UNESP) CEP 14800-900 Araraquara, SP – Brasil.

 

Received 25 October 2002; accepted in revised form 9 January 2004

 

Abstract

Iron nitroprusside, Fe(II)NP was incorporated into a carbon paste electrode and the electrochemical studies were performed by cyclic voltammetry. The cyclic voltammogram of the modified electrode, Fe(II)NP showed two redox couples ( E_½^ox)₁ = 0.24 and (E_½^ox)₂ = 0.85 V vs. SCE attributed to Fe^(II)/Fe^(III) and Fe^(II)(CN)₅NO / Fe^(III)(CN)₅NO, respectively. The redox couple at (E_½^ox)₁ = 0.24 V presents an electrocatalytic response for ascorbic acid. The modified paste electrode exhibits a decrease of 180 mV in the ascorbic acid oxidation. The modified graphite paste electrode gives a linear range from 1.0 × 10^-3 to 2.6 × 10^-2 mol L^-1 of ascorbic acid with a detection limit of 1.4 × 10^-3 (±1.2%) mol L^-1 (n =3). The electrocatalytic oxidation of ascorbic acid compounds by the mediator has been used for the determination of ascorbic acid in a commercially pharmaceutical available product .

 

Keywords: iron nitroprusside, modified electrode, electrocatalysis, ascorbic acid oxidation.

 

 

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*Corresponding author. E-mail address: nrstradi@iq.unesp.br