Next Article in Journal
Relationship between Molarity and Color in the Crystal (‘Dramada’) Produced by Scytalidium cuboideum, in Two Solvents
Next Article in Special Issue
Synthesis and Structural Identification of a Biaryl Ether-Linked Zearalenone Dimer
Previous Article in Journal
Quercetagetin and Patuletin: Antiproliferative, Necrotic and Apoptotic Activity in Tumor Cell Lines
Previous Article in Special Issue
The Content of Biogenic Amines in Croatian Wines of Different Geographical Origins
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Molecules
Volume 23
Issue 10
10.3390/molecules23102580
molecules-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Ultrasensitive Electrochemical Sensor Based on Polyelectrolyte Composite Film Decorated Glassy Carbon Electrode for Detection of Nitrite in Curing Food at Sub-Micromolar Level

by
Jingheng Ning
,
Xin Luo
,
Min Wang
,
Jiaojiao Li
,
Donglin Liu
,
Hou Rong
,
Donger Chen
and
Jianhui Wang
*
School of Chemistry and Biological Engineering, Changsha University of Science & Technology, Changsha 410110, China
*
Author to whom correspondence should be addressed.
Molecules 2018, 23(10), 2580; https://doi.org/10.3390/molecules23102580
Submission received: 3 September 2018 / Revised: 28 September 2018 / Accepted: 5 October 2018 / Published: 9 October 2018
(This article belongs to the Collection Advances in Food Analysis)
Browse Figures
Versions Notes

Abstract

:
To ensure food quality and safety, developing cost-effective, rapid and precision analytical techniques for quantitative detection of nitrite is highly desirable. Herein, a novel electrochemical sensor based on the sodium cellulose sulfate/poly (dimethyl diallyl ammonium chloride) (NaCS/PDMDAAC) composite film modified glass carbon electrode (NaCS/PDMDAAC/GCE) was proposed toward the detection of nitrite at sub-micromolar level, aiming to make full use of the inherent properties of individual component (biocompatible, low cost, good electrical conductivity for PDMDAAC; non-toxic, abundant raw materials, good film forming ability for NaCS) and synergistic enhancement effect. The NaCS/PDMDAAC/GCE was fabricated by a simple drop-casting method. Electrochemical behaviors of nitrite at NaCS/PDMDAAC/GCE were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimum conditions, the NaCS/PDMDAAC/GCE exhibits a wide linear response region of 4.0 × 10−8 mol·L−1~1.5 × 10−4 mol·L−1 and a low detection 1imit of 43 nmol·L−1. The NaCS/PDMDAAC shows a synergetic enhancement effect toward the oxidation of nitrite, and the sensing performance is much better than the previous reports. Moreover, the NaCS/PDMDAAC also shows good stability and reproducibility. The NaCS/PDMDAAC/GCE was successfully applied to the determination of nitrite in ham sausage with satisfactory results.

Graphical Abstract

1. Introduction

Nitrite is widely used as a preservative in food industry, especially in the production and processing of cured meat and fishery products [1]. Additionally, it is also utilized as a fertilizing agent in agriculture and an inhibitor in corrosion science [2]. Furthermore, nitrite has become one of the widespread inorganic contaminants present in soil, food, ground water, and even physiological systems [3]. Nitrite has been proven to be of potential risk to human health and leads to many serious diseases, such as methemoglobinemia, esophageal cancer, spontaneous abortion, and birth defects of the central nervous system [4,5,6,7]. Therefore, the content of nitrite demands strict control. The World Health Organization (WHO) has set a fixed maximum limit in drinking water for nitrite as 65 μM [8]. In China, according to national standard GB 2760-2014, the maximum permitted level of nitrite in meat food is 0.15 g/kg [9]. To ensure food quality and safety, developing cost-effective, rapid, and precision analytical techniques for quantitative detection of nitrite is highly desirable.
To date, many techniques have been developed for the detection of nitrite, including chromatography [10,11], UV spectrophotometry [12,13], fluorometry [14,15], and flow injection analysis [16,17]. Although these analytical methods are well-recognized, they also suffered from limits, such as high cost, being time-consuming, cumbersome, and requiring complicated pretreatment. Recently, electrochemical analysis has become one of most preferred techniques to detection small biomolecules, food additives, and environmental contaminants, owing to its overwhelming merits including cost- and time-effective, facile operation, and high sensitivity and specificity [18,19,20,21,22,23]. In the last few years, electrochemical nitrite sensors have received increasing attention. Various modified materials have been proposed for nitrite sensors, including graphene [24,25], carbon nanotubes [26], metal or metal oxide nanoparticles [27,28,29], metal organic frameworks [30,31], and conducting polymers [32,33]. However, these modified electrodes have several drawbacks, such as low detection limits (almost at the mmol/L level, far lower than sub-micromolar level for HPLC and fluorometry), narrow linear range, and susceptibility to interference. Thus, it is urgent to develop novel electrochemical sensors for the detection of nitrite at sub-micromolar level.
Poly (dimethyldiallylammonium chloride) (PDMDAAC) is a ubiquitous linear cationic polymer that has unique properties, such as biocompatibility, low cost, high charge density, as well as good water solubility [34]. It has been reported that PDMDAAC film was successfully immobilized on electrochemical sensors [35,36,37]. These previous studies demonstrated that PDMDAAC film has excellent conductivity due to the presence of electron conductive networks, and good ion-exchange performances that can effectively increase the concentration of anions round the film as compared with the bulk solution. For these reasons, PDMDAAC film was chosen as a modified material to construct electrochemical sensors, aiming to facilitate preconcentration and enhance selectivity properties of nitrite sensors, and eventually enhance the electrochemical response. However, PDMDAAC was found to exhibit relatively poor performances in film formation in our preliminary experiments, which could influence the electrode stability. Additionally, the sensitivity of PDMDAAC modified electrode is very limited. To overcome these problems, PDMDAAC was combined with sodium cellulose sulfate (NaCS), which has good film-formation ability. NaCS/PDMDAAC is an emerging composite film that has unique properties such as excellent mechanical strength, transparency and small pore size [38]. NaCS/PDMDAAC has been widely used in the immobilization of bacteria, fungus and microalgae, drug delivery systems, and membrane systems [38,39,40]. However, to our best knowledge, NaCS/PDMDAAC has rarely been applied as a modified material in electrochemical sensors.
Herein, NaCS/PDMDAAC composite film as prepared to construct a novel electrochemical sensor for the detection of nitrite at the sub-micromolar level, aiming to make full use of the merits of individual components (biocompatible, low cost, good electrical conductivity for PDMDAAC; non-toxic, abundant raw materials, and the good film forming ability of NaCS) and synergistic enhancement effect (Scheme 1). NaCS/PDMDAAC/GCE was fabricated by coating the PDMDAAC and NaCS sequentially on the surface of GCE. The electrochemical performance were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using [Fe(CN)6]3−/4− as redox probe solution. The analytical parameters (including pH) were systemically explored. Finally, the content of nitrite in ham sausage was determined by differential pulse voltammetry (DPV) with satisfactory results.

2. Results and Discussion

2.1. Characterization of Surface Morphology

The surface morphologies of NaCS film and NaCS/PDMDAAC composite film were characterized by scanning electron microscope (SEM, Figure 1). As shown in Figure 1A, the NaCS film consists of acicular crystal structure. After compositing with NaCS/PDMDAAC, the surface is changed from acicular crystal to smooth film (Figure 2a), which is favorable for the electron transfer between the surface of modified electrode and analytes, and would eventually enhance electrocatalytic activity toward nitrite.

2.2. Electrochemical Characterization of NaCS/PDMDAAC/GCE

The electrochemical performance of bare GCE, NaCS/GCE, PDMDAAC/GCE, and NaCS/PDMDAAC/GCE were investigated using cyclic voltammetry (CV) recorded in 5 × 10−3 mol L−1 K3[Fe(CN)6] solution. The cyclic voltamograms recorded on various electrodes are shown in Figure 2. A pair of redox peaks appears on all the electrodes, suggesting the electrochemical process is quasi-reversible. A pair of weak and broad peaks was observed on the bare GCE (curve a), with redox peak separation (∆Ep) of 137 mV. The anodic peak current (ipa) and cathodic peak current (ipc) is 43 μA, and 58 μA, respectively. On the NaCS modified electrode (curve b), the ∆Ep increases to 186 mV. Meanwhile, the peak currents also increase slightly, with ipa of μA and ipc of 69 μA, respectively. When modified with PDMDAAC alone (curve c), a pair of obvious and well-shaped redox peaks appears with a significant decrease on ∆Ep (101 mV). The corresponding redox peaks increase greatly, with ipa of 81 μA and ipc of 80 μA, respectively. When modified with NaCS/PDMDAAC composite film (curve d), the ∆Ep (143 mV) has a slight increase compared to that on the NaCS/GCE. The ipa and ipc is 72 μA and 89 μA, indicating that the NaCS/PDMDAAC film facilitates the electron transfer between the electrode and analyses, and eventually improves the electrochemical response.
The influence of layers of NaCS/PDMDAAC composite film was also investigated in 5 × 10−3 mol L−1 K3[Fe(CN)6] solution by CV. As illustrated in Figure 3, the response peak currents decrease with the increase of layers of NaCS/PDMDAAC composite film. It is probably related to the charge transfer resistance that increases with the thickness increasing. Hence, monolayer NaCS/PDMDAAC composite film was employed for subsequent experiments.
Electrochemical impedance spectroscopy (EIS) is a useful tool to acquire abundant information about electrode interface, which have been widely used in the electrocatalysis [41,42], chemosensors, and biosensors [43,44]. The EIS of bare GCE, NaCS/GCE, PDMDAAC/GCE, and NaCS/PDMDAAC/GCE were also measured in the 5 × 10–3 mol L–1 K3[Fe(CN)6] solution. The Nyquist plots of different electrodes were shown in Figure 4. The charge transfer resistance (Rct) were estimated by EIS fitting with the equivalent circuit. The Rct of bare GCE, NaCS/GCE, PDMDAAC/GCE, and NaCS/PDMDAAC/GCE are 37,830 Ω, 104,800 Ω, 36,810 Ω, and 52,190 Ω, respectively, i.e., the conductivity (1/Rct) of them are 2.6434 × 10–5 S, 9.5420 × 10–6 S, 2.7167 × 10–5 S, and 1.9161 × 10–5 S, respectively. Apparently, the conductivity of the bare GCE (2.6434 × 10–5 S) is slightly lower than that of PDMDAAC/GCE (2.7167 × 10–5 S) but much higher than that of NaCS/GCE (9.5420 × 10–6 S), indicating that when each of them is independently modified onto the bare electrode, the polycation PDMDAAC can improve the conductivity while the polyanion NaCS is not favorable for electron transfer. As is well known, both PDMDAAC and NaCS are polyelectrolytes and, theoretically, should have good conductivities. However, these polyelectrolytes are quite different in charge density, solubility, and counter-ion effects in solution (ions will naturally attract the opposite-charged ions to form counter-ion layers), all of which are thought to be able to influence the conductivity, and the former two factors are thought to be favorable for conductivity while the last one is unfavorable. In fact, the molecular weight of PDMDAAC used in our experiment is less than 1.0 × 105, while NaCS has a much bigger average molecular weight more than 1.9 × 106, and so it is obvious that PDMDAAC contains much shorter molecular chains, which reinvests it with a higher charge density, a better solubility, as well as a weaker counter-ion effect due to narrower interfaces to attract less opposite-charged ions. Thus, although both being polyelectrolytes, PDMDAAC can improve the conductivity of the modified GCE while NaCS cannot, as the above results show. However, it is worth noting that when using the composite NaCS/PDMDAAC modifies the bare GCE, the Rct of NaCS/PDMDAAC/GCE (52,190 Ω) is only about half of that on the NaCS/GCE (104,800 Ω), suggesting the unfavorable counter-ion effect of NaCS is significantly weakened after the introduction of PDMDAAC, which actually improves the charge transfer efficiency. Obviously, the conductivity of NaCS/PDMDAAC/GCE (1.9161 × 10−5 S) is better than that of NaCS/GCE (9.5420 × 10–6 S). Thus, by considering the outstanding conductivity of PDMDAAC as well as the good performances of NaCS for film formation, the composite NaCS/PDMDAAC is the most suitable material for the modification of GCE to construct the new and effective sensor for nitrite detection, herein with a moderate Rct/conductivity value, which is consistent with the above research result conducted by the CV method.

2.3. Electrochemical Behavior of Nitrite on NaCS/PDMDAAC/GCE

The electrochemical behaviors of nitrite on bare GCE and NaCS/PDMDAAC/GCE were investigated by CV in 0.1 mol·L–1 PBS solution containing 4.0 × 10–3 mol·L–1 nitrite (Figure 5). The anodic peak current on the bare GCE is 59 μA. When modified with NaCS/PDMDAAC composite film, the anodic peak current increases to 97 μA, suggesting the NaCS/PDMDAAC composite film improve the electrochemical responses of nitrite.

2.4. Optimization of Analytical Conditions

2.4.1. Effect of the Modifier Loading Amount

The effect of the modifier loading amount is one of important factors that affect the electrochemical response of modified electrode. The bare GCEs were modified with various dosage of NaCS/PDMDAAC dispersion (v/v = 1:1) firstly. Then the response peak currents of 1.0 × 10–4 mol·L–1 nitrite on these electrodes were recorded and compared. The effect of modifier loading on the response peak current was shown in Figure 6A. The response peak currents of nitrite vary with the loading amount of NaCS/PDMDAAC composite. The response peak current increases gradually with the loading amount increasing from 2–6 μL, afterwards the response peak currents decrease with the further increase on loading amount. The maximum response peak current is obtained when the loading amount is 6 μL. Namely, the loading amounts of PDMDAAC and NaCS are 3 μL. Hence, the 6 μL loading amount was used in the subsequent experiments. The trend of response peak current to loading amount is directly related to the amount of reactive active sites and the thickness of modifier films. With loading amount increasing, the amount of available reactive active sites increases, which causes the increase on the response peak current. However, the thickness of the modified film increases when the loading amount beyond 6 μL, which hinders the electron transfer between the electrode and nitrite. As a result, the response peak current decreases with the further increase on the loading amount.

2.4.2. Effect of PDMDAAC Concentration

The effect of the PDMDAAC concentration on the response peak current of nitrite was also explored. The results are shown in Figure 6B. It observed that the response peak current increases as the increase of PDMDAAC concentration. When the concentration (w/v) is 7%, the peak current reaches the maximum. Afterwards the response peak current decreases with further increase on PDMDAAC concentration. Therefore, 7% was selected to be the suitable PDMDAAC concentration for the following measurements.

2.4.3. Effect of pH

It is well known that pH plays a crucial role on the oxidation of nitrite, so it’s well worth investigating the influence of pH. The response peak currents of 1.0 × 10–4 mol·L–1 nitrite were measured in various pH (3.0–10.0), and the result was presented in Figure 6C. When the electrolyte solution closes to neutral (pH 7.0 or 8.0), the response peak current is largest. Therefore, pH 7.0 was recommended as the optimum pH. Under acidic conditions, NO2- is very unstable and easily reacted with H+ to produce NO and NO2 gas. As a result, the response peak current declines as the pH decreasing. In addition, most amount of the NO2− is protonated in such acidic environment (pKa(HNO2) = 3.3). Under alkaline pH ranging of 8.0–10.0, the increase on pH leads to the decline of the response peak current due to the lack of sufficient H+.

2.4.4. Effect of Accumulation Time

As we all know, accumulation time directly influences the adsorption of analyses at the surface of modified electrode. The NaCS/PDMDDA/GCE was accumulated for various times firstly, then corresponding response peak currents were record and compared (Figure 6D). During the first 300 s, the response peak currents increase with the time prolonging. It is probably due to the increasing amount of nitrite adsorbed on the reaction active sites. The highest response peak current was obtained for 300 s accumulation. Afterwards the response peak currents remain stable, suggesting the nitrite adsorption has achieved saturation. Thus, 300 s was selected as the optimal accumulation time.

2.5. Standard Curves, Linear Ranges, and Detection Limit

Under the optimized analytical conditions, the response peak currents of various concentrations of nitrite were measured by NaCS/PDMDAAC/GCE using differential pulse voltammetry (DPV). The response DPV curves of various concentrations of nitrite are shown in Figure 7. There is a good relationship between the response peak current and the nitrite concentration ranging from 4.0 × 10−8 mol·L–1 to 1.5 × 10–4 mol·L–1. The corresponding linear regression equation can expressed as i (μA) = 0.01027c (μmol·L–1) + 0.02771 (r = 0.9984, n = 8). The limit of detection (LOD, S/N = 3) is estimated to 4.3 × 10–8 mol·L–1. A comparison on sensing performances between reported electrodes and NaCS/PDMDAAC/GCE is summarized on the Table 1. The sensing performances (in terms of linear response range and limit of detection) of the NaCS/PDMDAAC/GCE are at least comparable to, and even better than, the most reported modified electrodes [45,46,47,48,49,50].

2.6. Selectivity, Reproducibility, and Stability of NaCS/PDMDAAC/GCE

Before detection nitrite in real samples, the practicability (including selectivity, reproducibility, and stability) of the proposed NaCS/PDMDAAC/GCE were checked carefully. Firstly, the interference investigation was performed in 1 × 10–5 mol·L–1 sodium nitrite mixed with the equal concentration of potential interfering substances including sodium chloride, glucose, l-cysteine, and ascorbic acid. The response peak current is hardly changed with these interfering compounds (peak current variation within 5%), indicating the nitrite is bonded specifically to the NaCS/PDMDAAC composite film and interfering substances cannot interfere with the nitrite detection. In other words, the proposed sensor has good specificity and selectivity toward nitrite.
Then, the reproducibility of NaCS/PDMDAAC/GCE was validated by repeatedly measuring the response peak currents for 9 times in 8.0 × 10−5 mol·L‒1 and 8.0 × 10‒6 mol·L–1 nitrite solution alternately. The result is shown in Table 1. Obviously, the response peak current remains stable after repeated measurements for 9 times, with relative standard deviation (RSD) of 1.05% and 4.89%, respectively (Table 2). It demonstrates that the proposed NaCS/PDMDAAC exhibits good reproducibility for nitrite detection.
Finally, the stability of the proposed sensor was investigated by continuously monitoring the response peak current for 30 days. The NaCS/PDMDAAC/GCE was always immersed in 0.1 mol·L‒1 PBS solution (pH 7.0) and stored at 4 °C for 30 days. The cyclic voltammetric response of nitrite at the NaCS/PDMDAAC/GCE was measured every 3 days. As shown in Figure 8, after 24 days, the current response of nitrite remains unchanged nearly. After 30 days, the response peak current value still retains 73.6% of the initial value. It can be inferred that the NaCS/PDMDAAC/GCE have good stability, which is very especially important for real sample detection.

2.7. Determination of Actual Samples

Under the optimal analytical conditions, the pretreated ham sausage filtrate was used as the actual sample. The concentration of nitrite was detected by DPV method in 0.1 mol·L–1 PBS (pH 7.0) using the proposed NaCS/PDMDAAC/GCE, and determination results are listed in Table 3. The unspiked content of nitrite are 26.24−27.32 mg/kg, which does not exceed the maximum permitted content (0.15 g/kg) [9]. Then these samples were spiked with known concentration nitrite, the recovery is estimated to 98.2–104.0%, with relative standard deviation (RSD) lower than 3.3%, suggesting the satisfactory results are obtained. Together with outstanding advantages including low cost, sensitivity, and selectivity, the proposed NaCS/PDMDAAC/GCE shows great prospects on the detection of nitrite in diverse food samples.

3. Conclusions

In this work, a novel electrochemical sensor based on NaCS/PDMDAAC composite film was proposed for the detection of nitrite at sub-micromolar level. The NaCS/PDMDAAC/GCE was fabricated by a facile drop-casting method. The surface morphology of NaCS film and NaCS/PDMDAAC composite was characterized by SEM. The electrochemical behavior of nitrite at the NaCS/PDMDAAC was investigated by CV and DPV. The NaCS/PDMDAAC not only shows the inherent properties from the individual component, but also exhibits synergetic enchantment effect toward sensing nitrite. Under optimal detection conditions, the proposed NaCS/PDMDAAC/GCE exhibits a wide linear response region of 4.0 × 10−8 mol·L–1~1.5 × 10−4 mol·L−1, and low detection limit of 43 nmol·L–1 (S/N = 3). Moreover, the proposed NaCS/PDMDAAC/GCE also has good stability and reproducibility. Finally, the NaCS/PDMDAAC/GCE was successfully used to detect the nitrite content in the ham sausage sample with satisfactory results. The proposed NaCS/PDMDAAC/GCE provided a promising sensing platform on the detection nitrite in diverse real samples at the sub-micromolar level.

4. Materials and Methods

4.1. Chemicals

Poly(dimethyldiallylammonium chloride) (PDMDAAC) was supplied by Aldrich Co., Ltd (Shanghai, China). Cellulose sulfate sodium salt was purchased from J&K SCIENTIFIC LTD (Shanghai, China). Borax and sodium nitrite were purchased from Hunan General Chemical Reagent Works (Changsha, China). Potassium ferricyanide, potassium hexacyanoferrate, sodium dihydrogen phosphate and disodium hydrogen phosphate were all bought from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). All the chemicals were of analytical reagent grade and were used as received without any further purification. Both PDMDAAC and NaCS were also synthesized in our experiments (details can be seen in the Supporting Information).

4.2. Fabrication of NaCS/PDMDAAC/GCE

The synthesis of NaCS and PDMDAAC has been described in the Supporting Information. The infrared spectra of cellulose sodium sulfate, 1H NMR spectrum of DMDAAC, infrared spectra of (a) PDMDAAC & (b) DMDAAC have been also plotted in the Supporting Information (Figure S1, Figure S2 & Figure S3). GCE was polished to mirror-like surface with 0.3 μm and 0.05 μm alumina powder, rinsed twice with ethanol and distilled water, and dried under natural condition. Firstly, 3 μL PDMDAAC (7% (w/v)) solution was drop-casted on the surface of GCE, dried naturally to obtain PDMDAAC/GCE. Secondly, 3 μL NaCS (3.5% (w/v)) solution was dropped-casted to the surface of PDMDAAC/GCE, dried naturally to obtain NaCS/PDMDAAC/GCE.

4.3. Electrochemical Measurements

All electrochemical experiments were performed on the CHI-760B electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd., Shanghai, China). A standard three-electrode system is used for all electrochemical experiments, consisting of bare GCE or modified electrodes as the working electrode, platinum wire as the counter electrode, and an Ag/AgCl electrode (saturated potassium chloride) as the reference electrode. The electrochemical performance was measured by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 5 × 10–3 mol·L–1 K3[Fe(CN)6] solution. The electrochemical behavior of nitrite at the NaCS/PDMDAAC/GCE was investigated by CV. The content of nitrite was detected by differential pulse voltammetry (DPV). The supporting electrolyte for all electrochemical measurements is 0.1 mol·L–1 Na2HPO4-NaH2PO4 buffer solution (PBS, pH 7.0, containing 0.1 M NaCl) unless otherwise stated.

4.4. Pretreatment of Ham Sausage Samples

The ham sausage samples were purchased from a local supermarket. 12.5 mL of borax saturation solution was added into 5 g ground ham sausage, and stirred to mix well. Then the ham sausage sample was washed into 50 mL volumetric flask by a small amount of hot water, and heated in boiling water bath for 15 min. Afterwards the volumetric flask was cooled to room temperature. Subsequently, 2.5 mL PBS solution was added into the volumetric flask, and then dilute with distilled water to 50 mL. After 30 min rest, the upper layer of fat or oil was removed, the spare liquor was extracted by suction filtration to obtain sample solution for quantitative analysis.

Supplementary Materials

The following are available online.

Author Contributions

J.N. and J.W. conceived and designed the experiments; J.N., X.L., M.W., and J.L. performed the experiments; D.L., R.H., D.C., J.N., and J.W. analyzed the data; J.N., and J.W. contributed reagents/materials/analysis tools; J.N. and J.W. wrote the paper; all authors read and approved the final manuscript.

Funding

This research was funded by the NSFC (no. 21505005), the National Key R&D Program of China (2017YFC1600306), Hunan Provincial Natural Science Foundation (no. 2018JJ2424), Open Project of National Engineering Laboratory of Hydrometallurgical Cleaner Production Technology of Chinese Academy of Sciences (No. 20120220CH1), Scientific Research Fund of Hunan Provincial Education Department (no. 17C0034), Open Research Program of Hunan Provincial Key Laboratory of Power and Transportation Materials (no. 2017CL07), and the Huxiang Youth Talent Support Program (2015RS4051).

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Noor, N.S.; Tan, L.L.; Heng, L.Y.; Chong, K.F.; Tajuddin, S.N. Acrylic microspheres-based optosensor for visual detection of nitrite. Food Chem. 2016, 207, 132–138. [Google Scholar] [CrossRef] [PubMed]
  2. Kumar, J.V.; Karthik, R.; Chen, S.M.; Balasubramanian, P.; Muthuraj, V.; Selvam, V. A novel cerium tungstate nanosheets modified electrode for the effective electrochemical detection of carcinogenic nitrite ions. Electroanalysis 2017, 29, 2385–2394. [Google Scholar] [CrossRef]
  3. Rastogi, P.; Ganesan, V.; Krishnamoorthi, S. A promising electrochemical sensing platform based on a silver nanoparticles decorated copolymer for sensitive nitrite determination. J. Mater. Chem. A 2013, 2, 933–943. [Google Scholar] [CrossRef]
  4. Manassaram, D.M.; Backer, L.C.; Moll, D.M. A review of nitrites in drinking water: Maternal exposure and adverse reproductive and developmental outcomes. Environ. Health Perspect. 2006, 114, 320–327. [Google Scholar] [CrossRef] [PubMed]
  5. Bukowski, J.; Somers, G.; Bryanton, J. Agricultural contamination of groundwater as a possible risk factor for growth restriction or prematurity. J. Occup. Environ. Med. 2001, 43, 377–383. [Google Scholar] [CrossRef] [PubMed]
  6. Brender, J.D.; Olive, J.M.; Felkner, M.; Suarez, L.; Marckwardt, W.; Hendricks, K.A. Dietary nitrites and nitrites, nitrosatable drugs, and neural tube defects. Epidemiology 2004, 15, 330–336. [Google Scholar] [CrossRef] [PubMed]
  7. Kikura-Hanajiri, R.; Martin, R.S.; Lunte, S.M. Indirect measurement of nitric oxide production by monitoring nitrite and nitrite using microchip electrophoresis with electrochemical detection. Anal. Chem. 2002, 74, 6370–6377. [Google Scholar] [CrossRef] [PubMed]
  8. WHO. Guidelines for Drinking-Water Quality, 3rd ed.; World Health Organization: Geneva, Switzerland, 2008; ISBN 9789241547611. [Google Scholar]
  9. Mao, Y.; Bao, Y.; Han, D.; Zhao, B. Research progress on nitrite electrochemical sensor. Chin. J. Anal. Chem. 2018, 46, 147–156. [Google Scholar] [CrossRef]
  10. Li, Y.; Whitaker, J.S.; McCarty, C.L. Reversed-phase liquid chromatography/electrospray ionization/mass spectrometry with isotope dilution for the analysis of nitrite and nitrite in water. J. Chromatogr. 2011, 1218, 476–483. [Google Scholar] [CrossRef] [PubMed]
  11. He, L.; Zhang, K.; Wang, C.; Luo, X.; Zhang, S. Effective indirect enrichment and determination of nitrite ion in water and biological samples using ionic liquid-dispersive liquid-liquid microextraction combined with high-performance liquid chromatography. J. Chromatogr. 2011, 1218, 3595–3600. [Google Scholar] [CrossRef] [PubMed]
  12. Manzoori, J.L.; Sorouraddin, M.H.; Hajishabani, A.M. Spectrophotometric determination of nitrite based on its catalytic effect on the oxidation of carminic acid by bromate. Talanta 1998, 46, 1379–1386. [Google Scholar] [CrossRef]
  13. Pourreza, N.; Fat’Hi, M.R.; Hatami, A. Indirect cloud point extraction and spectrophotometric determination of nitrite in water and meat products. Microchem. J. 2012, 104, 22–25. [Google Scholar] [CrossRef]
  14. Peng, Q.; Xie, M.G.; Koon-Gee, N.; Kang, E.T. A new nitrite-selective fluorescent sensor fabricated from surface-initiated atom-transfer radical polymerization. Chem. Lett. 2005, 34, 1628–1629. [Google Scholar] [CrossRef]
  15. Jiao, C.X.; Niu, C.G.; Huan, S.Y.; Shen, Q.; Yang, Y.; Shen, G.L.; Yu, R.Q. A reversible chemosensor for nitrite based on the fluorescence quenching of a carbazole derivative. Talanta 2004, 64, 637–643. [Google Scholar] [CrossRef] [PubMed]
  16. Lin, K.; Ma, J.; Yuan, D.; Feng, S.; Su, H.; Huang, Y.; Shangguan, Q. Sequential determination of multi-nutrient elements in natural water samples with a reverse flow injection system. Talanta 2017, 167, 166–171. [Google Scholar] [CrossRef] [PubMed]
  17. Feng, S.; Zhang, M.; Huang, Y.; Yuan, D.; Zhu, Y. Simultaneous determination of nanomolar nitrite and nitrite in seawater using reverse flow injection analysis coupled with a long path length liquid waveguide capillary cell. Talanta 2013, 117, 456–462. [Google Scholar] [CrossRef] [PubMed]
  18. Ning, J.; He, Q.; Luo, X.; Wang, M.; Liu, D.; Wang, J.; Liu, J.; Li, G. Rapid and sensitive determination of vanillin based on a glassy carbon electrode modified with Cu2O-electrochemically reduced graphene oxide nanocomposite film. Sensors 2018, 18, 2762. [Google Scholar] [CrossRef] [PubMed]
  19. He, Q.; Liu, J.; Liang, J.; Liu, X.; Li, W.; Liu, Z.; Ding, Z.; Tuo, D. Towards Improvements for Penetrating the Blood–Brain Barrier—Recent Progress from a Material and Pharmaceutical Perspective. Cells 2018, 7, 24. [Google Scholar] [CrossRef] [PubMed]
  20. He, Q.; Liu, J.; Liu, X.; Li, G.; Deng, P.; Liang, J. Preparation of Cu2O-reduced graphene nanocomposite modified electrodes towards ultrasensitive dopamine detection. Sensors 2018, 18, 199. [Google Scholar] [CrossRef] [PubMed]
  21. He, Q.; Liu, J.; Liu, X.; Li, G.; Chen, D.; Deng, P.; Liang, J. Fabrication of amine-modified magnetite-electrochemically reduced graphene oxide nanocomposite modified glassy carbon electrode for sensitive dopamine determination. Nanomaterials 2018, 8, 194. [Google Scholar] [CrossRef] [PubMed]
  22. He, Q.; Liu, J.; Liang, J.; Liu, X.; Tuo, D.; Li, W. Chemically Surface Tunable Solubility Parameter for Controllable Drug Delivery—An Example and Perspective from Hollow PAA-Coated Magnetite Nanoparticles with R6G Model Drug. Materials 2018, 11, 247. [Google Scholar] [CrossRef] [PubMed]
  23. He, Q.; Liu, J.; Liu, X.; Li, G.; Deng, P.; Liang, J. Manganese dioxide Nanorods/electrochemically reduced graphene oxide nanocomposites modified electrodes for cost-effective and ultrasensitive detection of Amaranth. Colloid Surf. B 2018, 172, 565–572. [Google Scholar] [CrossRef] [PubMed]
  24. Ma, Y.; Song, X.; Ge, X.; Zhang, H.; Wang, G.; Zhang, Y.; Zhao, H. In situ growth of α-Fe2O3 nanorod arrays on 3d carbon foam as an efficient binder-free electrode for highly sensitive and specific determination of nitrite. J. Mater. Chem. A 2017, 5, 4726–4736. [Google Scholar] [CrossRef]
  25. Mehmeti, E.; Stanković, D.M.; Hajrizi, A.; Kalcher, K. The use of graphene nanoribbons as efficient electrochemical sensing material for nitrite determination. Talanta 2016, 159, 34–39. [Google Scholar] [CrossRef] [PubMed]
  26. Rabti, A.; Aoun, S.B.; Raouafi, N. A sensitive nitrite sensor using an electrode consisting of reduced graphene oxide functionalized with ferrocene. Microchim. Acta 2016, 183, 3111–3117. [Google Scholar] [CrossRef]
  27. Dai, J.; Deng, D.; Yuan, Y.; Zhang, J.; Deng, F.; He, S. Amperometric nitrite sensor based on a glassy carbon electrode modified with multi-walled carbon nanotubes and poly(toluidine blue). Microchim. Acta 2016, 183, 1553–1561. [Google Scholar] [CrossRef]
  28. Shivakumar, M.; Nagashree, K.L.; Manjappa, S.; Dharmaprakash, M.S. Electrochemical detection of nitrite using glassy carbon electrode modified with silver nanospheres (AgNS) obtained by green synthesis using pre-hydrolysed liquor. Electroanalysis 2017, 29, 1434–1442. [Google Scholar] [CrossRef]
  29. Seo, Y.; Manivannan, S.; Kang, I.; Lee, S.W.; Kim, K. Gold dendrites co-deposited with m13 virus as a biosensor platform for nitrite ions. Biosens. Bioelectron. 2017, 94, 87–93. [Google Scholar] [CrossRef] [PubMed]
  30. Kung, C.W.; Li, Y.S.; Lee, M.H.; Wang, S.Y.; Chiang, W.H.; Ho, K.C. In-situ growth of porphyrinic metal-organic framework nanocrystals on graphene nanoribbons for electrocatalytic oxidation of nitrite. J. Mater. Chem. A 2016, 4, 10673–10682. [Google Scholar] [CrossRef]
  31. Kung, C.W.; Chang, T.H.; Chou, L.Y.; Hupp, J.T.; Farha, O.K.; Ho, K.C. Porphyrin-based metal–organic framework thin films for electrochemical nitrite detection. Electrochem. Commun. 2015, 58, 51–56. [Google Scholar] [CrossRef] [Green Version]
  32. Xu, G.; Liang, S.; Fan, J.; Sheng, G.; Luo, X. Amperometric sensing of nitrite using a glassy carbon electrode modified with a multilayer consisting of carboxylated nanocrystalline cellulose and poly(diallyldimethyl ammonium) ions in a pedot host. Microchim. Acta 2016, 183, 2031–2037. [Google Scholar] [CrossRef]
  33. Chen, L.; Liu, X.; Wang, C.; Lv, S.; Chen, C. Amperometric nitrite sensor based on a glassy carbon electrode modified with electrodeposited poly(3,4-ethylenedioxythiophene) doped with a polyacenic semiconductor. Microchim. Acta 2017, 184, 2073–2079. [Google Scholar] [CrossRef]
  34. Masumi, T.; Matsushita, Y.; Dan, A.; Takama, R.; Saito, K.; Kuroda, K.; Fukushima, K. Adsorption behavior of poly(dimethyl-diallylammonium chloride) on pulp fiber studied by cryo-time-of-flight secondary ion mass spectrometry and cryo-scanning electron microscopy. Appl. Surf. Sci. 2014, 289, 155–159. [Google Scholar] [CrossRef]
  35. Wang, B.; Okoth, O.K.; Yan, K.; Zhang, J. A highly selective electrochemical sensor for 4-chlorophenol determination based on molecularly imprinted polymer and PDDA-functionalized graphene. Sens. Actuators B Chem. 2016, 236, 294–303. [Google Scholar] [CrossRef]
  36. Yang, J.; Lin, Q.; Yin, W.; Jiang, T.; Zhao, D.; Jiang, L. A novel nonenzymatic glucose sensor based on functionalized pdda-graphene/cuo nanocomposites. Sens. Actuators B Chem. 2017, 253, 1087–1095. [Google Scholar] [CrossRef]
  37. Yang, T.; Zhang, W.; Du, M.; Jiao, K. A PDDA/poly(2,6-pyridinedicarboxylic acid)-CNTs composite film DNA electrochemical sensor and its application for the detection of specific sequences related to PAT gene and NOS gene. Talanta 2008, 75, 987–994. [Google Scholar] [CrossRef] [PubMed]
  38. Chen, G.; Yao, S.J.; Guan, Y.X.; Lin, D.Q. Preparation and characterization of NaCS-cmc/PDMDAAC capsules. Colloids Surf. B Biointerfaces 2005, 45, 136–143. [Google Scholar] [CrossRef] [PubMed]
  39. Zeng, X.H.; Danquah, M.K.; Zheng, C.; Potumarthi, R.; Chen, X.D.; Lu, Y.H. NaCS-PDMDAAC immobilized autotrophic cultivation of chlorella sp. For wastewater nitrogen and phosphate removal. Chem. Eng. J. 2004, 99, 185–192. [Google Scholar] [CrossRef]
  40. Zhang, J.; Guan, Y.X.; Ji, Z.; Yao, S.J. Effects on membrane properties of NaCS–PDMDAAC capsules by adding inorganic salts. J. Membr. Sci. 2006, 277, 270–276. [Google Scholar] [CrossRef]
  41. Wang, M.; Chen, K.; Liu, J.; He, Q.; Li, G.; Li, F. Efficiently enhancing electrocatalytic activity of α-MnO2 nanorods/N-doped ketjenblack carbon for oxygen reduction reaction and oxygen evolution reaction using facile regulated hydrothermal treatment. Catalysts 2018, 8, 138. [Google Scholar] [CrossRef]
  42. Chen, K.; Wang, M.; Li, G.; He, Q.; Liu, J.; Li, F. Spherical α-MnO2 supported on N-KB as efficient electrocatalyst for oxygen reduction in al–air battery. Materials 2018, 11, 601. [Google Scholar] [CrossRef] [PubMed]
  43. Li, G.; Wang, S.; Duan, Y.Y. Towards gel-free electrodes: A systematic study of electrode-skin impedance. Sens. Actuators B Chem. 2017, 241, 1244–1255. [Google Scholar] [CrossRef]
  44. Li, G.; Zhang, D.; Wang, S.; Duan, Y.Y. Novel passive ceramic based semi-dry electrodes for recording electroencephalography signals from the hairy scalp. Sens. Actuators B Chem. 2016, 237, 167–178. [Google Scholar] [CrossRef]
  45. Bai, W.; Sheng, Q.; Zheng, J. Hydrophobic interface controlled electrochemical sensing of nitrite based on one step synthesis of polyhedral oligomeric silsesquioxane/reduced graphene oxide nanocomposite. Talanta 2016, 150, 302–309. [Google Scholar] [CrossRef] [PubMed]
  46. Chen, X.; Wang, F.; Chen, Z. An electropolymerized nile blue sensing film-based nitrite sensor and application in food analysis. Anal. Chim. Acta 2008, 623, 213–220. [Google Scholar] [CrossRef] [PubMed]
  47. Feng, J.J.; Zhang, P.P.; Wang, A.J.; Zhang, Y.; Dong, W.J.; Chen, J.R. One-pot hydrothermal synthesis of uniform β-MnO2 nanorods for nitrite sensing. J. Colloid Interface Sci. 2011, 359, 1–8. [Google Scholar] [CrossRef] [PubMed]
  48. Ghanei-Motlagh, M.; Taher, M.A. A novel electrochemical sensor based on silver/halloysite nanotube/molybdenum disulfide nanocomposite for efficient nitrite sensing. Biosens. Bioelectron. 2018, 109, 279–285. [Google Scholar] [CrossRef] [PubMed]
  49. Haldorai, Y.; Hwang, S.K.; Gopalan, A.I.; Huh, Y.S.; Han, Y.K.; Voit, W.; Saianand, G.; Lee, K.P. Direct electrochemistry of cytochrome c immobilized on titanium nitride/multi-walled carbon nanotube composite for amperometric nitrite biosensor. Biosens. Bioelectron. 2016, 79, 543–552. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  50. Ranjani, B.; Kalaiyarasi, J.; Pavithra, L.; Devasena, T.; Pandian, K.; Gopinath, S. Amperometric determination of nitrite using natural fibers as template for titanium dioxide nanotubes with immobilized hemin as electron transfer mediator. Microchim. Acta 2018, 185, 194. [Google Scholar] [CrossRef] [PubMed]
Molecules 23 02580 sch001 550
Scheme 1. Schematic of NaCS/PDMDAAC/GCE for the detection of nitrite detection.
Scheme 1. Schematic of NaCS/PDMDAAC/GCE for the detection of nitrite detection.
Molecules 23 02580 sch001
Molecules 23 02580 g001 550
Figure 1. SEM images of NaCS film (A) and NaCS/PDMDAAC composite film (B).
Figure 1. SEM images of NaCS film (A) and NaCS/PDMDAAC composite film (B).
Molecules 23 02580 g001
Molecules 23 02580 g002 550
Figure 2. Cyclic voltammograms of bare GCE (a), NaCS/GCE (b), PDMDAAC/GCE (c), and NaCS/PDMDAAC/GCE (d) recorded in 5 × 10–3 mol·L−1 K3[Fe(CN)6] solution.
Figure 2. Cyclic voltammograms of bare GCE (a), NaCS/GCE (b), PDMDAAC/GCE (c), and NaCS/PDMDAAC/GCE (d) recorded in 5 × 10–3 mol·L−1 K3[Fe(CN)6] solution.
Molecules 23 02580 g002
Molecules 23 02580 g003 550
Figure 3. Cyclic voltammograms of different layer of PDMDAAC/NaCS modified GCE recorded in 5 × 10–3 mol·L–1 K3[Fe(CN)6] solution.
Figure 3. Cyclic voltammograms of different layer of PDMDAAC/NaCS modified GCE recorded in 5 × 10–3 mol·L–1 K3[Fe(CN)6] solution.
Molecules 23 02580 g003
Molecules 23 02580 g004 550
Figure 4. (A) Nyquist plots of different electrodes in 5 × 10–3 mol·L–1 K3[Fe(CN)6] solution obtained from electrochemical impedance spectroscopy (EIS). The frequency investigated was between 10,000 and 0.1 Hz with a pulse amplitude of 5 mV. The inset is the equivalent circuit of electrode/electrolyte interface. (B) The Rct of different electrodes by EIS fitting.
Figure 4. (A) Nyquist plots of different electrodes in 5 × 10–3 mol·L–1 K3[Fe(CN)6] solution obtained from electrochemical impedance spectroscopy (EIS). The frequency investigated was between 10,000 and 0.1 Hz with a pulse amplitude of 5 mV. The inset is the equivalent circuit of electrode/electrolyte interface. (B) The Rct of different electrodes by EIS fitting.
Molecules 23 02580 g004
Molecules 23 02580 g005 550
Figure 5. Cyclic voltammograms of bare GCE (a) and NaCS/PDMDAAC/GCE (b) in 0.1 mol·L–1 PBS solution (pH 7.0) containing 4.0 × 10–3 mol·L–1 nitrite.
Figure 5. Cyclic voltammograms of bare GCE (a) and NaCS/PDMDAAC/GCE (b) in 0.1 mol·L–1 PBS solution (pH 7.0) containing 4.0 × 10–3 mol·L–1 nitrite.
Molecules 23 02580 g005
Molecules 23 02580 g006 550
Figure 6. Effect of loading amount of NaCS/PDMDAAC (A), concentration of PDMDAAC(w/v) (B), pH (C) and accumulation time (D) on the response peak current of nitrite (1.0 × 10–4 mol·L–1) at the NaCS/PDMDAAC/GCE.
Figure 6. Effect of loading amount of NaCS/PDMDAAC (A), concentration of PDMDAAC(w/v) (B), pH (C) and accumulation time (D) on the response peak current of nitrite (1.0 × 10–4 mol·L–1) at the NaCS/PDMDAAC/GCE.
Molecules 23 02580 g006
Molecules 23 02580 g007 550
Figure 7. Differential pulse voltammograms of NaCS/PDMDAAC/GCE in the nitrite solution of different concentrations with 0.1 V pulse amplitude, 0.01 s pulse width and 0.1 V s−1 scan rate. (a) 1.5 × 10−4 mol·L–1; (b) 1.0 × 10−4 mol·L–1; (c) 7.5 × 10−5 mol·L–1; (d) 4.5 × 10−5 mol·L–1; (e) 1.5 × 10−5 mol·L–1; (f) 5 × 10−6 mol·L–1; (g) 5 × 10−7 mol·L–1; (h) 4 × 10−8 mol·L–1.
Figure 7. Differential pulse voltammograms of NaCS/PDMDAAC/GCE in the nitrite solution of different concentrations with 0.1 V pulse amplitude, 0.01 s pulse width and 0.1 V s−1 scan rate. (a) 1.5 × 10−4 mol·L–1; (b) 1.0 × 10−4 mol·L–1; (c) 7.5 × 10−5 mol·L–1; (d) 4.5 × 10−5 mol·L–1; (e) 1.5 × 10−5 mol·L–1; (f) 5 × 10−6 mol·L–1; (g) 5 × 10−7 mol·L–1; (h) 4 × 10−8 mol·L–1.
Molecules 23 02580 g007
Molecules 23 02580 g008 550
Figure 8. Stability for NaCS/PDMDAAC/GCE monitored in the 1.0 × 10−4 mol·L–1 nitrite for 30 days.
Figure 8. Stability for NaCS/PDMDAAC/GCE monitored in the 1.0 × 10−4 mol·L–1 nitrite for 30 days.
Molecules 23 02580 g008
Table
Table 1. A comparison on sensing performances between reported electrodes and NaCS/PDMDAAC/GCE.
Table 1. A comparison on sensing performances between reported electrodes and NaCS/PDMDAAC/GCE.
ElectrodesMethodsLinear Ranges (μmol·L–1)LOD (μmol·L–1)References
POSS/rGO/GCECA0.5–1200.08[45]
PNB/GCEDPV0.5–1000.1[46]
β-MnO2 NRs/GCECA0.29–26,0900.29[47]
Ag/HNT/MoS2/CPECA2–4250.7[48]
MWCNTs-TiN/GCECA1–20000.0014[49]
hemin/TNT/GCECA0.6–1300.084[50]
NaCS/PDMDAAC/GCEDPV150–0.040.043This work
Table
Table 2. The reproducibility of NaCS/PDMDAAC/GCE for nitrite determination.
Table 2. The reproducibility of NaCS/PDMDAAC/GCE for nitrite determination.
No.Current Response (μA)
8.0 × 10−5 mol⋅L–18 × 10−6 mol⋅L–1
10.8960.115
20.8740.123
30.8870.112
40.8880.121
50.8780.114
60.8900.117
70.8980.112
80.8940.129
90.9030.122
Average0.8890.118
SD0.0090.006
RSD (%)1.05%4.89%
Table
Table 3. Determination of nitrite in ham sausage samples using the NaCS/PDMDAAC/GCE.
Table 3. Determination of nitrite in ham sausage samples using the NaCS/PDMDAAC/GCE.
SamplesContent (mg/kg)Added (mg/kg)Founded (mg/kg)Recovery (%)RSD (%)
127.323058.52104.02.3
226.873057.32102.61.4
326.243055.7198.23.3

Share and Cite

MDPI and ACS Style

Ning, J.; Luo, X.; Wang, M.; Li, J.; Liu, D.; Rong, H.; Chen, D.; Wang, J. Ultrasensitive Electrochemical Sensor Based on Polyelectrolyte Composite Film Decorated Glassy Carbon Electrode for Detection of Nitrite in Curing Food at Sub-Micromolar Level. Molecules 2018, 23, 2580. https://doi.org/10.3390/molecules23102580

AMA Style

Ning J, Luo X, Wang M, Li J, Liu D, Rong H, Chen D, Wang J. Ultrasensitive Electrochemical Sensor Based on Polyelectrolyte Composite Film Decorated Glassy Carbon Electrode for Detection of Nitrite in Curing Food at Sub-Micromolar Level. Molecules. 2018; 23(10):2580. https://doi.org/10.3390/molecules23102580

Chicago/Turabian Style

Ning, Jingheng, Xin Luo, Min Wang, Jiaojiao Li, Donglin Liu, Hou Rong, Donger Chen, and Jianhui Wang. 2018. "Ultrasensitive Electrochemical Sensor Based on Polyelectrolyte Composite Film Decorated Glassy Carbon Electrode for Detection of Nitrite in Curing Food at Sub-Micromolar Level" Molecules 23, no. 10: 2580. https://doi.org/10.3390/molecules23102580

APA Style

Ning, J., Luo, X., Wang, M., Li, J., Liu, D., Rong, H., Chen, D., & Wang, J. (2018). Ultrasensitive Electrochemical Sensor Based on Polyelectrolyte Composite Film Decorated Glassy Carbon Electrode for Detection of Nitrite in Curing Food at Sub-Micromolar Level. Molecules, 23(10), 2580. https://doi.org/10.3390/molecules23102580

Article Metrics

Back to TopTop