Electrocatalytic oxidation and determination of nitrite on carbon paste electrode modified with oxovanadium(IV)-4-methyl salophen
Introduction
Nitrites are of both environmental and biological importance. The potential for nitrite to be metabolised to carcinogenic N-nitroso compounds [1], [2] and its widespread presence in food products and beverages has necessitated its monitoring [1], [2], [3], [4], [5]. Nitrite is used as a food preservative (E249, E250) and its salts are known to occur in high quantity in soil [6], [7], [8], [9]. Industrially, it is used to inhibit corrosion in industrial water. Also, nitrite is an important source of nitrogen in green plants and its complete reduction is achieved in nature by nitrite reduction enzymes [10]. Various methods have been used to determine nitrite ions, including spectrophotometry [11], [12], [13], [14], chromatography [15] and electrochemical methods [16], [17], [18], [19], [20], [21], [22]. Electrochemical methods offer useful alternative since they allow a faster and precise analysis [23], [24], [25], [26]. Electrochemical determination of nitrite is either by reduction or oxidation. Oxidation of nitrite ions offers several advantages, namely no interference from nitrate ion and from molecular oxygen, which are usually the major limitations in the cathodic determination of nitrite [23], [24]. The use of bare electrodes such as carbon electrodes, platinum and gold for the oxidation of nitrite requires high potentials [17], [27] and these electrodes tend to be poisoned by the species formed during the electrochemical process [28]. A good way of lowering potentials is using modified electrodes. One of the most important effects of any mediator is a reduction of the overpotential required for the electrochemical reaction and enhancement of the sensitivity (current) and selectivity of the method.
The development and application of chemically modified carbon paste electrodes (CMCPEs) have received considerable attention in recent years due to their many advantages, such as easy manufacture, non-poison, low price, wider operational potential window, renewable surface, stability in various solvents and longer life time [29], [30]. The incorporation of electroactive materials into a carbon paste electrode is advantageous and has been widely applied in the electroanalytical community.
Transition metal complexes such as Schiff bases are well known as electron mediators in the electrocatalytic oxidation of some biologically important compounds. Oxovanadium(IV) and oxovanadium(V) complexes with Schiff base ligands exhibit a reversible (IV/V) redox response with electrodes in various electrolyte solution [31]. The redox and electrochemical behaviors of oxovanadium complexes with ligand salen [H2-salen = N,N-ethylenebis-(salicylideneamine)] in acetonitrile solution were first studied by Bonadies and co-worker [32]. The acid-induced disproportionation of VIVO(salen) was the result that was originally proposed by Bonadies et al. [32]. Recently, additional electrochemical studies of the complexes have been described [33], [34], [35]. Owing to reversible redox activity and catalytic properties of V-salen complexes, they are used as catalysts in the epoxidation of olefins [36], oxidation of sulfides with peroxidies [37] and electrocatalytic reduction of oxygen to water [38], [39] and electrocatalytic detection of iodate, periodate, bromate and nitrite [40]. The present work reports on the application of oxovanadium(IV)-4-methyl salophen ([VO(SB)])-modified carbon paste electrode for the electrocatalytic determination of nitrite ion in aqueous solutions.
Section snippets
Reagents and solutions
The Schiff base and its complex with vanadium(IV) (Fig. 1) were prepared according to the literature procedures [41]. All chemicals were of analytical-reagent grade from Merck or Fluka and were used directly without further purification. Triply distilled water was used to prepare buffer and reagent solutions. The supporting electrolyte used in all the experiments was 0.1 M KCl or 0.1 M phosphate buffer solutions.
Apparatus
Voltammetric experiments were performed with a Metrohm computrace voltammetric
Electrochemical behavior of VIVO(salen) in acetonitrile solution
The reaction of VIVO(SB) with methanesulfonic acid in acetonitrile is readily monitored by means of cyclic voltammetry. Fig. 2 (part A) is the response obtained from VIVO(SB) before the addition of an acid. The single reversible response, corresponding to half-reaction 1, matches that reported in previous studies [32], [33].The Addition of methanesulfonic acid produced the separated oxidation and reduction waves shown in part B (curves a–d) of Fig. 2. As the concentration of
Conclusions
In the present article, the electrocatalytic activity of an oxovanadium(IV) complex-modified carbon paste electrode toward the oxidation of nitrite in 0.1 M phosphate buffer (pH 4) medium was demonstrated. The oxovanadium(IV) Schiff base complex forms a reversible oxidation to oxovanadium(V) at potential about 0.62 V and reversible disproportionation to V(III) and V(V) in the presence of an acid (reaction 2). However, in the presence of an acid the occurrence of reaction 2 produces a second peak
Acknowledgement
The authors wish to express their gratitude to the Zanjan University Research Council for the support of this work.
References (49)
Cancer Lett.
(1995)- et al.
Talanta
(2004) - et al.
Anal. Biochem.
(2004) - et al.
Talanta
(2005) - et al.
J. Chromatogr. B
(2000) - et al.
Anal. Chim. Acta
(1992) - et al.
Talanta
(2004) - et al.
Electrochim. Acta
(2007) - et al.
J. Electroanal. Chem.
(2004) - et al.
Talanta
(2005)
J. Electroanal. Chem.
Electrochim. Acta
Electrochem. Commun.
Inorg. Chim. Acta
Electrochem. Commun.
J. Electroanal. Chem.
J. Electroanal. Chem.
J. Electroanal. Chem.
Eur. J. Pharm. Environ. Toxicol. Pharmacol.
CRC Crit. Rev. Anal. Chem.
J. Sci. Food. Agric.
J. Sci. Food. Agric.
Oncology
Nature
Cited by (125)
Enhanced non-enzyme nitrite electrochemical sensing property based on stir bar-shaped ZnO nanorods decorated with nitrogen-doped reduced graphene oxide
2022, Sensors and Actuators B: ChemicalNon-enzymatic nitrite amperometric sensor fabricated with near-spherical ZnO nanomaterial
2022, Colloids and Surfaces B: BiointerfacesElectrocatalytic detection of nitrite at NiCo<inf>2</inf>O<inf>4</inf> nanotapes synthesized via microwave-hydrothermal method
2021, Journal of Electroanalytical Chemistry