Electrooxidation of Sulfite Ions on a Composite Carbon-Containing Electrode Modified with Submicron Gold Particles
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Electrooxidation of Sulfite Ions on a Composite Carbon-Containing Electrode Modified with Submicron Gold Particles S. V. Kovalevaa, O. S. Aksinenkoa, and A. V. Korshunovb, * a
Tomsk State Pedagogical University, Tomsk, 634061 Russia State University of Civil Engineering, Moscow, 129337 Russia *e-mail: [email protected]
bMoscow
Received December 30, 2019; revised February 20, 2020; accepted February 20, 2020
Abstract—Regularities of the electrooxidation of sulfite ions in an alkaline medium (рН ≥ 8; LiClO4, KNO3, Na2SO4, NaOH) on a composite carbon-containing electrode modified by submicron (300 nm or smaller) gold particles are studied using cyclic voltammetry. The electrocatalytic nature of the analytical signal is substantiated; a scheme of the oxidation process is proposed. A procedure for the preliminary electrochemical treatment of the modified electrode, ensuring an increase in the substrate oxidation current and consisting in the anodic polarization of the electrode in the potential range 0.9–1.4 V (Ag/AgCl reference electrode) in a supporting electrolyte is optimized. The essence of activation is an increase in the surface area of gold particles participating in the catalytic generation/reduction cycle of gold (hydr)oxides and providing an increase in the value of the analytical signal. The proposed approach ensures a significant increase of the sensitivity of the voltammetric method for determining sulfite ions. The concentration dependence of the analytical signal is linear in the concentration range of SO32 − -ions 1 × 10–7–2 × 10–4 М (limit of detection 5.5 × 10–8 M). The results of the determination of sulfite ions in wines, beer, and juices indicate a higher accuracy of the voltammetric method compared to the standard iodometric procedure. Keywords: sulfite ions, electrooxidation, composite carbon-containing electrode, gold particles, activation of the working electrode, concentration dependence of the analytical signal DOI: 10.1134/S1061934820080080
The main sources of inorganic sulfur(IV) compounds (dioxide, sulphurous acid, and sulfites) in a human body are man-made emissions (heat power, oil refining, metallurgy, chemical industry, and transport [1]) and food products, into which SO2 and sulfites are introduced as preservatives E220–E228 (wine, beer, and soft drinks; meat and fish semi-finished products; packaged perishable products; fruits, vegetables, and their processed products – up to 3 g/kg [2]). Sulfites belong to the third hazard class [3]. When ingested, they manifest themselves as allergic dermatitis, gastrointestinal upsets, and asthmatic attacks [4]. The World Health Organization recommended a low daily intake of sulfites in a human body (0.7 mg/kg body weight in terms of SO2 [5]), and, therefore, the amount of SO2 and sulfites in food products at a level of 10 mg/kg and higher should be reflected in the compoisiton of products [6]. The procedures adopted in chemical analytical practice for the determination of sulfites in food products, including those introduced in national s
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