Simultaneous electrochemical determination of sulphite and nitrite by a gold nanoparticle/graphene-chitosan modified electrode

A highly sensitive electrochemical sensor for the simultaneous determination of SO₃ 2- and NO₂ - based on a glassy carbon electrode (GCE) modified with graphene (GR)-chitosan (CS) and gold nanoparticles (AuNPs) was developed. The GR and GR-CS/AuNPs GCEs were characterized using a transmission electron microscope (TEM). The electrochemical behaviours of SO₃ 2- and NO₂ - at the GR-CS/AuNPs GCE were investigated using cyclic voltammetry (CV). The chemically modified electrode displayed excellent electrochemical catalytic activities towards sulphite and nitrite. Linear relationships between the values of the oxidation peak current and the concentration of SO₃ 2- and NO ₂ - were obtained in the ranges of 5 μM to 0.41 mM (R = 0.9986) and 1 μM to 0.38 mM (R = 0.9940) with detection limits (S/N = 3) of 1 μM and 0.25 μM, respectively. This GR-CS/AuNPs GCE showed many advantages in terms of stability, sensitivity, facility and economy. The proposed method was employed to example real samples with recoveries of 97.2% to 102.6%.