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Electrocatalytic and voltammetric determination of sulfhydryl compounds through iron nitroprusside modified graphite paste electrode

Author(s): Carmo Devaney R. do | Silva Ricardo M. da | Stradiotto Nelson R.

Journal: Journal of the Brazilian Chemical Society
ISSN 0103-5053

Volume: 14;
Issue: 4;
Start page: 616;
Date: 2003;
Original page

Keywords: iron nitroprusside | graphite paste electrode | L-cysteine | N-acetylcysteine | sulfhydryl compounds

Iron nitroprusside Fe(II)NP was incorporated into a carbon paste electrode and the electrochemical studies were performed with cyclic voltammetry. The cyclic voltammogram of Fe(II)NP exhibits two redox couple with formal potential (E0')1 = 0.24 e (E0')2 = 0.85 V vs SCE attributed to Fe(II)/Fe(II) and Fe(II)(CN)5NO / Fe(III)(CN)5NO, respectively. The redox couple with (E0')2 = 0.85 V presents an electrocatalytic response for sulfhydryl compounds. The electrocatalytic oxidation of sulfhydryl compounds by the mediator has been used for the determination of L-cysteine and N-acetylcysteine. The modified graphite paste electrode gives a linear range from 9.2 ×10-4 - 2.0 ×10-2; 9.6 × 10-4 - 1.4 × 10-2mol L-1 for the determination of L-cysteine and N-acetylcysteine, respectively, with detection limit of 1.9 ×10-4 mol L-1; 1.5 × 10-4 mol L-1 and relative standard desviations ± 5% and 1.5 × 10-3 mol L-1 ± 4% (n=3). The amperometric sensitivities are 0.024 and 0.027 muA/mumol L-1 for L-cysteine and N-acetylcysteine, respectively. The application of this electrode was tested and a commercial pharmaceutical product (Fluimucil) has been determined.
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