Nitrite electrochemical sensor based on graphene oxide and polytromethamine composite material as well as preparation method and application of nitrite electrochemical sensor

Abstract

The invention discloses a nitrite electrochemical sensor based on a graphene oxide and polytromethamine composite material and a preparation method and application thereof, and belongs to the field of electrochemical method detection, the preparation method comprises the following steps: uniformly dispensing a graphene oxide suspension on the surface of a glassy carbon electrode, and airing to obtain GO / GCE; putting the GO / GCE, a saturated calomel electrode and a platinum wire electrode into an electrolyte containing tromethamine with a certain concentration, and carrying out electropolymerization by adopting a cyclic voltammetry to obtain Poly (Tris) / GO / GCE; a saturated calomel electrode is used as a reference electrode, a platinum wire electrode is used as a counter electrode, Poly (Tris) / GO / GCE is used as a working electrode, and the nitrite electrochemical sensor is constructed and is more accurate and sensitive in nitrite detection, the linear detection range is 2 * 10 <-6 >-6 * 10 <-3 > mol / L, and the detection limit is 1.00 * 10 <-7 > mol / L.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical detection, in particular to a nitrite electrochemical sensor based on a graphene oxide and polytromethamine composite material, and a preparation method and application thereof. Background Art

[0002] Nitrite is a common food preservative, additive and corrosion inhibitor, which is widely present in drinking water, food and environmental systems. The misuse and overuse of inorganic fertilizers can lead to excessive nitrite content in water and agricultural products. Excessive nitrite is not only harmful to the environment, but also to human health. Nitrite is used as an official food preservative, which can inhibit the growth of harmful bacteria such as Clostridium botulinum. In addition, nitrite has also been developed as an important color preservative. It is added to meat products in the form of sodium or potassium salts and can react with myoglobin to preserve the color and flavor of fresh meat. At the same time, nitrite can interfere with the body's oxygen transport system and interact with amines in the stomach to produce carcinogenic nitrosamines, which is particularly harmful to pregnant women and infants. The World Health Organization (WHO) has included nitrite in the list of carcinogens, and most countries have enacted laws and regulations to limit and control the use of nitrite in food and industrial production. These measures have alleviated people's concerns about the hazards of nitrite to a certain extent, but the best solution is to establish a complete nitrite monitoring and control system. In addition, according to the World Health Organization (WHO), the nitrite concentration limit in drinking water is 3 mg / L.

[0003] As people's awareness of environmental protection and food safety increases, the detection of nitrite has become an important item in environmental testing and food analysis.

[0004] In view of this, it is necessary to develop a method for detecting nitrite concentration that is highly sensitive, stable, simple and low-cost. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a nitrite electrochemical sensor based on a graphene oxide and polytromethamine composite material, and a preparation method and application thereof. The prepared nitrite electrochemical sensor is more accurate and sensitive in detecting nitrite.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for preparing a nitrite electrochemical sensor based on a composite material of graphene oxide and polytromethamine comprises the following steps: Step 1, evenly drop a graphene oxide suspension on the surface of a glassy carbon electrode, and after drying, obtain a graphene oxide modified glassy carbon electrode GO / GCE; Step 2, placing the GO / GCE prepared in step 1, a saturated calomel electrode, and a platinum wire electrode into an electrolyte containing a certain concentration of tromethamine for electropolymerization; using cyclic voltammetry to polymerize tromethamine onto the surface of GO / GCE to obtain Poly(Tris) / GO / GCE; Step 3, using saturated calomel electrode as reference electrode, platinum wire electrode as counter electrode, and Poly(Tris) / GO / GCE as working electrode, a three-electrode system of nitrite electrochemical sensor was constructed.

[0007] A further improvement of the technical solution of the present invention is that in step 1, the modification amount of the graphene oxide is 10 μL.

[0008] A further improvement of the technical solution of the present invention is that in step 2, the scanning rate is 0.1 V / s, the voltage range is -1.5 to 2.0 V, and the number of scanning circles is 25 circles.

[0009] A further improvement of the technical solution of the present invention is that in step 2, the concentration of the tromethamine solution is 10 mmol / L.

[0010] A further improvement of the technical solution of the present invention is that the preparation method also includes the preparation of a graphene oxide suspension, specifically: weighing 5.0 mg of graphene oxide with an analytical balance, adding 5.00 mL of deionized water thereto, and finally placing it in an ultrasonic cleaner for more than one hour to obtain a graphene oxide suspension; and then ultrasonicating it again for 20 minutes with an ultrasonic cleaner before use to prevent precipitation of the graphene oxide.

[0011] A further improvement of the technical solution of the present invention is that the preparation method also includes pretreatment of GCE, specifically: polishing the bare glassy carbon electrode with polishing aluminum powder so that the surface of the polished bare glassy carbon electrode presents a mirror surface; placing the polished electrode in an ultrasonic cleaner, and ultrasonically cleaning it with deionized water, anhydrous ethanol, and deionized water for 5 minutes.

[0012] The nitrite electrochemical sensor based on graphene oxide and polytromethamine composite material prepared by the preparation method.

[0013] Application of the nitrite electrochemical sensor based on graphene oxide and polytromethamine composite material prepared by the preparation method in detecting nitrite concentration.

[0014] A further improvement of the technical solution of the present invention is that the nitrite electrochemical sensor based on the graphene oxide and polytromethamine composite material is applied to the direct real-time detection of nitrite in the liquid phase.

[0015] A further improvement of the technical solution of the present invention is that: in specific application, the detection steps are: (1) The three electrodes of the constructed nitrite electrochemical sensor were placed in a 0.1 mol / L phosphate buffer solution with a pH value of 3; (2) Add the water sample containing nitrite to be tested into the base solution; (3) Nitrite was detected by differential pulse voltammetry, with the following parameters: potential range 0.5-1.1 V, amplitude 50 mV, pulse width 0.05 s, sampling width 0.0167, pulse period 0.5 s, and rest time 2 s; (4) The nitrite content was calculated by measuring the oxidation peak current value of nitrite on the DPV curve and using the standard curve.

[0016] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is: 1. The present invention prepares Poly(Tris) / GO / GCE, wherein graphene oxide has good stability and can be attached to an electrode to increase the specific surface area of ​​the electrode and improve the adsorption efficiency of the electrode; polytromethamine also has excellent conductivity, so graphene oxide and polytromethamine are co-modified on the electrode surface, and the synergistic effect of the two increases the number of active sites on the electrode and improves the electrocatalytic performance of the working electrode to nitrite.

[0017] 2. The present invention uses Poly(Tris) / GO / GCE as the working electrode, adopts GO modification amount of 10 μL, electrolyte pH of 3, enrichment stirring time of 60 s, and Poly(Tris) modification amount of 25 cycles to construct a nitrite electrochemical sensor. The linear detection range of the nitrite electrochemical sensor is 2×10 -6 ~6×10 -3 mol / L, the detection limit is 1.00×10 -7 mol / L, with a wide linear range and a low detection limit.

[0018] 3. The nitrite electrochemical sensor constructed by the present invention was used to measure nitrite of the same concentration in parallel 12 times, and the relative standard deviation was 3.44%, indicating that the precision of the nitrite electrochemical sensor was high; the spiked recovery rate of the nitrite electrochemical sensor was between 99% and 101%, indicating that the nitrite electrochemical sensor had a high accuracy.

[0019] 4. The nitrite electrochemical sensor provided by the present invention is simple to prepare and operate, has low cost, and has good stability and selectivity, and is expected to be applied to the determination of nitrite in actual samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. Figure 1 is a flow chart of the preparation method provided by the present invention; Figure 2 1 is a SEM image of GCE, GO / GCE, and Poly(Tris) / GO / GCE in an embodiment of the present invention; Among them, SEM image of A-GCE; SEM image of B-GO / GCE; SEM image of C- Poly(Tris) / GO / GCE; Figure 3 is a CV graph of Poly(Tris) / GO / GCE in an embodiment of the present invention; Among them, A-blank 0.1mol / L PBS electrolyte (red); B-containing 5.00×10 -4 mol / L nitrite in 0.1 mol / L PBS electrolyte (blue); Figure 4 CV diagrams of nitrite on different electrodes in the embodiment of the present invention; Among them, A-Poly(Tris) / GO / GCE (red); B-GCE (brown); C-Poly(Tris) / GCE (blue); D-GO / GCE (green); Figure 5 is a standard curve diagram of nitrite in an embodiment of the present invention; Figure 6 is a DPV diagram of different concentrations of nitrite in an embodiment of the present invention; Among them, the nitrite concentrations of the DPV curve from top to bottom are 0.002, 0.04, 0.1, 0.2, 0.4, 2.0, 4.0, 6.0 mmol / L. DETAILED DESCRIPTION

[0021] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0022] The present invention is further described in detail below with reference to the accompanying drawings and embodiments: like Figure 1 As shown, a method for preparing a nitrite electrochemical sensor based on a composite material of graphene oxide and polytromethamine comprises the following steps: (1) Preparation of graphene oxide suspension: 5.0 mg of graphene oxide was accurately weighed on an analytical balance, and 5.00 mL of deionized water was added thereto. The suspension was then placed in an ultrasonic cleaner for more than one hour to obtain a graphene oxide suspension. The suspension was then ultrasonically cleaned for another 20 minutes before subsequent use to prevent the graphene oxide from precipitating.

[0023] (2) Pretreatment of GCE: Use polishing aluminum powder to polish the bare glassy carbon electrode so that the surface of the polished bare glassy carbon electrode presents a mirror surface. Place the polished electrode in an ultrasonic cleaner and perform ultrasonic cleaning with deionized water, anhydrous ethanol, and deionized water for 5 minutes.

[0024] (3) Preparation of GO / GCE: Ensure that the surface of the pretreated GCE remains dry and clean, and use a cleaned microsyringe to transfer a certain amount of graphene oxide suspension. The graphene oxide in the graphene oxide suspension must remain suspended to prevent it from precipitating. Use the drop coating method to drop graphene oxide on the surface of GCE, ensuring that the graphene oxide completely covers the electrode surface, and wait for the water to completely evaporate to form a graphene oxide film, and then GO / GCE can be obtained.

[0025] (4) Preparation of Poly(Tris) / GO / GCE: The prepared GO / GCE, saturated calomel electrode, and platinum wire electrode were placed in an electrolyte containing 10 mmol / L tromethamine for electropolymerization. The electrochemical method selected was cyclic voltammetry, with a scan rate parameter of 0.1 V / s, a voltage range of -1.5 to 2.0 V, and a scan number of 25 circles. This method can be used to polymerize tromethamine to the electrode surface to obtain Poly(Tris) / GO / GCE.

[0026] (5) A three-electrode system of nitrite electrochemical sensor was constructed using saturated calomel electrode as the reference electrode, platinum wire electrode as the counter electrode, and Poly(Tris) / GO / GCE as the working electrode.

[0027] In the embodiment of the present invention, Poly(Tris) / GCE is also prepared, and the prepared GCE, saturated calomel electrode, and platinum wire electrode are placed in a solution containing 10mmol / L tromethamine for electropolymerization. Cyclic voltammetry is used, the scan rate is set to 0.1V / s, the voltage is set to -1.5~2.0V, and the number of scans is 25. Polytromethamine is polymerized to the electrode surface to obtain Poly(Tris) / GCE.

[0028] Specifically, the instruments used include: JSM-7900F field emission scanning electron microscope, CHI660c electrochemical workstation, 85-2 digital display constant temperature magnetic stirrer, pHs-3C acidity meter, FA2204B electronic balance, laboratory pure water treatment system, HN6-180 ultrasonic cleaner, 1-100μL micropipette, KH-A infrared lamp, etc.

[0029] A complete electrochemical sensor is constructed with a three-electrode system, an electrochemical workstation, an electrolytic cell and a display to determine nitrite.

[0030] Three-electrode system: the reference electrode is a saturated calomel electrode; the counter electrode is a platinum wire electrode; the working electrode is a glassy carbon electrode (GCE) or a graphene oxide modified glassy carbon electrode (GO / GCE) or a polytromethamine modified glassy carbon electrode [Poly(Tris) / GCE] or a graphene oxide and polytromethamine modified glassy carbon electrode [Poly(Tris) / GO / GCE].

[0031] Note: Electrode in English is Electrode, and E is the abbreviation of electrode in English, that is, E in the present invention represents electrode.

[0032] Main reagents: sodium nitrite, tromethamine, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium chloride, phosphoric acid, graphene oxide, alumina polishing powder, 0.1 mol / L PBS buffer solution (prepared with a certain proportion of sodium dihydrogen phosphate and disodium hydrogen phosphate).

[0033] The application of nitrite electrochemical sensor based on graphene oxide and polytromethamine composite in detecting nitrite concentration.

[0034] The nitrite electrochemical sensor based on graphene oxide and polytromethamine composite material is applied to the direct real-time detection of nitrite in liquid phase, and the detection steps are as follows: (1) The three electrodes of the constructed nitrite electrochemical sensor were placed in a 0.1 mol / L phosphate buffer solution with a pH value of 3; (2) Add the water sample containing nitrite to be tested into the base solution; (3) Nitrite was detected by differential pulse voltammetry (DPV), with the following parameters: potential range 0.5-1.1 V, amplitude 50 mV, pulse width 0.05 s, sampling width 0.0167, pulse period 0.5 s, and rest time 2 s; (4) The nitrite content was calculated by measuring the oxidation peak current value of nitrite near 0.85V on the DPV curve and using the standard curve.

[0035] 1. Characterization of Modified Electrodes 1.1 SEM characterization of working electrode The three working electrodes GCE, GO / GCE, and Poly(Tris) / GO / GCE were characterized by scanning electron microscopy. Figure 2 Comparing SEM images A and B, it can be seen that GO is successfully modified on GCE. Comparing SEM images B and C, it can be seen that Poly(Tris) is successfully electropolymerized on GO / GCE.

[0036] 1.2 Electrochemical behavior of nitrite on different electrodes When studying the electrochemical behavior of nitrite on different electrodes, a control experiment is required. By studying the electrochemical behavior of Poly(Tris) / GO / GCE in blank 0.1 mol / L PBS electrolyte and 5.00×10 -4 The CV graph of mol / L nitrite in 0.1 mol / L PBS electrolyte (pH=3) was used to study the potential range of the scans, which was 0.4-1.2 V, and the scan rate was 0.1 V / s. Figure 3 shown.

[0037] According to the CV curve, compared with the blank solution, -4 The 0.1 mol / L PBS electrolyte containing nitrite has an additional obvious oxidation peak at a potential of 0.8-0.9 V, indicating that nitrite underwent a significant oxidation reaction on Poly(Tris) / GO / GCE.

[0038] To study the electrocatalytic performance of GCE, GO / GCE, Poly(Tris) / GCE, and Poly(Tris) / GO / GCE, cyclic voltammetry was used. The electrolyte in the electrolytic cell was configured to contain 5.00×10 -4 0.1 mol / L PBS electrolyte (pH=3) containing nitrite. The potential range was 0.4-1.2 V and the scan rate was 0.1 V / s when cyclic voltammetry was used to measure the peak current i of the oxidation peak generated by the oxidation reaction of nitrite in the CV graph. p The obtained CV graph is as follows Figure 4shown.

[0039] Depend on Figure 4 It can be seen that the oxidation peak currents of nitrite on the four working electrodes are in the following order from small to large: i pGCE <i pPoly(Tris） / GCE <i pGO / GCE <i pPoly(Tris） / GO / GCE Because GO has large conductivity and specific surface area, Poly(Tris) has electrocatalytic performance on nitrite and Poly(Tris) itself has good conductivity, so Poly(Tris) / GO / GCE has the most significant electrocatalytic performance on nitrite. Therefore, the electrocatalytic effect of Poly(Tris) / GO / GCE on nitrite is more obvious than other electrodes.

[0040] 2. Sensor performance test 2.1 Standard curve and detection limit The nitrite electrochemical sensor constructed by the present invention with Poly(Tris) / GO / GCE as the working electrode was used to measure the DPV curves of nitrite standard solutions with different concentrations using the DPV method. p The concentration of nitrite c and the oxidation peak current i are plotted. p The results are as follows: Figure 5 and Figure 6 shown.

[0041] The results showed that when the nitrite concentration c was 2×10 -6 ~6×10 -3 mol / L range, the concentration c and peak current i p The values ​​show an obvious linear relationship, and its linear equation is i p (μA)=7.1957c(mmol / L)+0.8224,R=0.9940,detection limit is 1.00×10 -7 mol / L.

[0042] 2.2 Precision The nitrite electrochemical sensor constructed by the present invention with Poly(Tris) / GO / GCE as the working electrode was used to measure the concentration of 5.00×10 -4 The relative standard deviation of 12 parallel determinations was 3.44%, indicating that the electrochemical sensor has high precision.

[0043] 2.3 Selectivity Under the optimal experimental conditions, the selectivity of the nitrite electrochemical sensor constructed in the present invention with Poly(Tris) / GO / GCE as the working electrode was studied by DPV method. -4 mol / L nitrite in 0.1 mol / L PBS electrolyte (pH=3) was added to study the interference of some common ions. The experimental results show that when the relative error of the determination is not greater than 5%, 100 times the Mg 2+ , Ca 2+ 、Na + , K + 、SO4 2- PO4 3- , Cl － , 20 times Fe 2+ , have no interference with the detection of nitrite.

[0044] 2.4 Sample testing and spike recovery experiment A simulated water sample containing nitrite is prepared, and the nitrite concentration therein is determined using the nitrite electrochemical sensor constructed by the present invention with Poly(Tris) / GO / GCE as the working electrode. The nitrite content of the simulated water sample containing nitrite is determined by: firstly performing DPV scanning on the nitrite in the simulated water sample to obtain the oxidation peak current i on its DPV curve. p1 The standard curve is used to calculate the nitrite content c1 in the simulated water sample. Then a certain amount of nitrite standard solution is added to the simulated water sample to increase its concentration by Δc. The DPV scan of nitrite in the simulated water sample after addition is performed again to obtain the oxidation peak current i on its DPV curve. p2 The value was used to calculate the content c2 of nitrite in the simulated water sample after spiked addition through the standard curve. The spiked recovery rate was calculated according to the formula (c1-c2) / Δc×100%, and the spiked recovery rate was 99%-101%. The results are shown in Table 1.

[0045] Table 1 Spike recovery experiment

[0046] In summary, the present invention uses Poly(Tris) / GO / GCE as the working electrode, the modification amount of Poly(Tris) is 25 cycles, the modification amount of GO is 10 μL, the pH value of the electrolyte is 3, and the stirring enrichment time is 60 s to construct a nitrite electrochemical sensor; the linear detection range of the nitrite electrochemical sensor is 2×10 -6 ~6×10 -3 mol / L, the detection limit is 1.00×10 - 7mol / L; The above data show that the nitrite electrochemical sensor prepared by the present invention has high precision and accuracy.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a nitrite electrochemical sensor based on a composite material of graphene oxide and polytromethamine, characterized in that: The following steps are involved: Step 1, evenly drop a graphene oxide suspension on the surface of a glassy carbon electrode, and after drying, obtain a graphene oxide modified glassy carbon electrode GO / GCE; Step 2, placing the GO / GCE, saturated calomel electrode and platinum wire electrode prepared in step 1 into an electrolyte containing a certain concentration of tromethamine and performing electropolymerization by cyclic voltammetry; polymerizing tromethamine onto the surface of GO / GCE to obtain Poly(Tris) / GO / GCE; Step 3, using saturated calomel electrode as reference electrode, platinum wire electrode as counter electrode, and Poly(Tris) / GO / GCE as working electrode, a three-electrode system of nitrite electrochemical sensor was constructed.

2. The preparation method according to claim 1, characterized in that: In step 1, the modification amount of graphene oxide is 10 μL.

3. The preparation method according to claim 1, characterized in that: In step 2, the scanning rate is 0.1 V / s, the voltage range is -1.5 to 2.0 V, and the number of scanning turns is 25 turns.

4. The preparation method according to claim 1, characterized in that: In step 2, the concentration of the tromethamine solution is 10 mmol / L.

5. The preparation method according to claim 1, characterized in that: The preparation method also includes the preparation of a graphene oxide suspension, specifically: weighing 5.0 mg of graphene oxide with an analytical balance, adding 5.00 mL of deionized water thereto, and finally placing it in an ultrasonic cleaner for more than one hour to obtain a graphene oxide suspension; and then ultrasonicating it again for 20 minutes with an ultrasonic cleaner before use to prevent precipitation of the graphene oxide.

6. The preparation method according to claim 1, characterized in that: The preparation method also includes pretreatment of GCE, specifically: polishing the bare glassy carbon electrode with polishing aluminum powder so that the surface of the polished bare glassy carbon electrode presents a mirror surface; placing the polished electrode in an ultrasonic cleaner, and performing ultrasonic cleaning with deionized water, anhydrous ethanol, and deionized water for 5 minutes respectively.

7. A nitrite electrochemical sensor based on a composite material of graphene oxide and polytromethamine prepared by the preparation method according to any one of claims 1 to 6.

8. Application of a nitrite electrochemical sensor based on a composite material of graphene oxide and polytromethamine prepared by the preparation method according to any one of claims 1 to 6 in detecting nitrite concentration.

9. The use according to claim 8, characterized in that: The nitrite electrochemical sensor based on the graphene oxide and polytromethamine composite material is applied to the direct real-time detection of nitrite in the liquid phase.

10. The use according to claim 9, characterized in that: In specific applications, the detection steps are: (1) The three electrodes of the constructed nitrite electrochemical sensor were placed in a 0.1 mol / L phosphate buffer solution with a pH value of 3; (2) Add the water sample containing nitrite to be tested into the base solution; (3) Nitrite was detected by differential pulse voltammetry, with the following parameters: potential range 0.5-1.1 V, amplitude 50 mV, pulse width 0.05 s, sampling width 0.0167, pulse period 0.5 s, and rest time 2 s; (4) The nitrite content was calculated by measuring the oxidation peak current value of nitrite on the DPV curve and using the standard curve.

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