Electrochemical detection of nitrite based on the polythionine/carbon nanotube modified electrode
Highlights
► Polythionine (PTH) was used as a mediator for electrocatalytic reduction of nitrite. ► Carbon nanotubes (CNTs) improve electron transfer between the electrode and nitrite. ► The PTH/CNT/glassy carbon electrode showed excellent nitrite detection performance.
Introduction
It is well known that nitrite is generally found within the environment and live process and is commonly used as an additive or corrosion inhibitor in some foods [1], [2]. However, nitrite can interact with amines to form carcinogenic nitrosamines [3]. Therefore, it is necessary and critical to carry out the determination of nitrite in practical analysis. In recent years, many techniques have been developed for the detection of nitrite [4], [5], [6], [7], [8]. Among them, electrochemical methods have been widely used because of their properties with rapid response and simple use [9], [10]. Generally, the electrochemical detection of nitrite can be realized based on the electrochemical oxidation or reduction of nitrite. However, it should be pointed out that the reduction potential of nitrite is extremely negative [11], and it is difficult to directly detect nitrite using its reduction behavior. Therefore, many catalysts are employed to catalyze the electroreduction of nitrite [12], [13], [14]. So far, the electrochemical sensor for nitrite with high sensitivity and selectivity is still challenging, although the electrochemical detection of nitrite has been improved greatly. Recently, more efforts are being made to improve the sensitivity and selectivity.
In this present work, a strategy for the determination of nitrite was explored based on the electrocatalytic reduction of nitrite at the polythionine (PTH)/carbon nanotube (CNT)-modified electrode. Herein, PTH was used as a mediator for electrocatalytic reduction of nitrite. And CNTs as an excellent nanomaterial can improve the electron transfer between the electrode and nitrite. The PTH/CNT-modified electrode exhibited a remarkable synergistic augmentation on response current of nitrite, which was very significant for the improvement of the sensitivity. Additionally, a relatively low detection limit and good selectivity for the detection of nitrite were also obtained.
Section snippets
Reagents and apparatus
Thionine and sodium nitrite were purchased from Chemical Reagent Company of Shanghai (China). Carbon nanotubes (20–30 nm in diameter) were obtained from Shenzhen Nanotech. Port Company. Before use, CNTs were treated in a mixture of sulfuric and nitric acid (3:1) with 6 h ultrasonication, followed by filtering, rinsing with double-distilled water and drying. Then, a CNT suspension (1 mg mL− 1) was prepared by dispersing the treated CNT in double-distilled water. All other chemicals were of analytic
Polymerization of thionine at the bare GC and CNT/GC electrodes
Both the bare GC (a) and CNT/GC (b) electrodes were potentially cycled from − 0.4 to 1.1 V in 0.5 M H2SO4 solution containing 0.4 mM thionine. And the corresponding results were shown in Fig. 1A. It can be observed that a pair of redox wave appeared for both electrodes, which was indicative of gradual growth of the polymer at the bare GC and CNT/GC electrodes via radical dimerization routine [16]. However, comparing with the bare GC electrode (Fig. 1A-a), the peak currents of polythionine at the
Conclusions
In this paper, the PTH/CNT/GC electrode was fabricated and employed for the electroanalysis of nitrite. We have illustrated that the PTH/CNT/GC electrode offered the electrocatalytic reduction for nitrite. The PTH/CNT/GC electrode was used to detect nitrite with high sensitivity of 5.81 μA mM− 1, and the detection limit of 1.4 × 10− 6 M. In addition, the PTH/CNT/GC electrode has high stability and good selectivity for the determination of nitrite. This indicates that the PTH/CNT/GC electrode is
Acknowledgment
This work was financially supported by the National Natural Science Foundation of China (Nos. 21005090; 21105128; 21105126), and State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University.
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