A GO / Mg-Fe-LDH modified electrode and electrochemical sensor

Abstract

The present invention discloses a GO / Mg‑Fe‑LDH modified electrode and an electrochemical sensor, and relates to the technical field of electrode materials. The present invention discloses a GO / Mg‑Fe‑LDH modified electrode consisting of a working electrode and a magnesium-iron double hydroxide layer and a graphene oxide layer wrapped from the inside out on the surface of the working electrode. The GO / Mg‑Fe‑LDH modified electrode prepared in the present application is used as a working electrode in an electrochemical sensor. The electrochemical sensor is suitable for detecting the content of mycophenolic acid in feed. The modified electrode prepared in the present invention has a large specific surface area and can provide more active sites for the reaction, thereby significantly improving the sensitivity of the sensor to the target molecule. The good catalytic performance of the material can significantly improve the charge transfer rate.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and in particular to a GO / Mg-Fe-LDH modified electrode and an electrochemical sensor. Background Art

[0002] Electrochemical sensors are devices that detect the type and content of target substances by monitoring the electrical signals (such as current, voltage, and resistance) generated by redox reactions in electrolytes or buffers. This application area involves multiple disciplines, including chemistry, materials science, information technology, and microelectronics. This sensing method allows for the construction of corresponding detection electrodes based on the specific substance being tested. Compared to conventional detection methods, the equipment and materials used offer advantages such as portability, real-time detection, fast response time, and low production costs. It is widely used in areas such as food safety, environmental monitoring, medical diagnostics, and industrial process control.

[0003] Graphene oxide (GO), a graphene derivative derived from graphene by oxidation, has a similar two-dimensional structure to graphene, resulting in a large surface area and excellent electrical conductivity. Graphene oxide also possesses numerous oxygen-containing groups, such as hydroxyl and alkoxy groups, on its surface. These oxygen-containing groups not only enable GO to be highly dispersible in water and polar solvents but also provide abundant active sites, thereby enhancing its chemical catalytic properties. This has led to its widespread application as a surface modification material for electrodes. Layered double hydroxides (LDHs) are specialized compounds with a columnar structure, consisting of positively charged layers with intercalated anions. This unique structure exhibits interlayer anion exchangeability, thermal stability, enzyme-mimicking activity, a large surface area, and a two-dimensional nanostructure. Combining this excellent material with electrochemical sensors can improve sensor sensitivity and lower detection limits. Its catalytic properties can also be exploited as an electrocatalyst to amplify electrochemical signals. This material is simple to prepare and low-cost, making it suitable for the development of highly sensitive and cost-effective electrochemical sensors. Therefore, by utilizing the electrochemical and structural properties of double metal hydroxides or graphene oxide to prepare composite materials for modifying electrode surfaces, it is possible to construct an electrochemical detector that is accurate and inexpensive. Summary of the Invention

[0004] The purpose of the present invention is to provide a GO / Mg-Fe-LDH modified electrode and electrochemical sensor to solve the following technical problems:

[0005] Existing working electrodes for electrochemical sensors have low sensitivity.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A GO / Mg-Fe-LDH modified electrode consists of a working electrode and a magnesium-iron double hydroxide layer and a graphene oxide layer wrapped from the inside out on the surface of the working electrode.

[0008] As a further solution of the present invention: a magnesium-iron layered double hydroxide solution is coated on the surface of the working electrode and dried to obtain a magnesium-iron double hydroxide layer.

[0009] As a further solution of the present invention: the working electrode is any one of a glassy carbon electrode, a platinum electrode, a gold electrode, and a copper electrode.

[0010] As a further embodiment of the present invention, the magnesium-iron layered double hydroxide solution uses water as a solvent, and each milliliter of the solution contains 0.5-3 mg of magnesium-iron layered double hydroxide (Mg-Fe-LDH).

[0011] As a further embodiment of the present invention, the working electrode is pretreated before being coated with the magnesium-iron layered double hydroxide solution; the pretreatment step includes placing the working electrode in a slurry containing polishing powder for polishing; the difference between the two peak voltages of the working electrode obtained after pretreatment is less than 0.1V.

[0012] As a further solution of the present invention: a graphene oxide solution is coated on the surface of a working electrode coated with a magnesium-iron double hydroxide layer and dried to obtain a modified electrode coated with a magnesium-iron double hydroxide layer and a graphene oxide layer from the inside out.

[0013] As a further embodiment of the present invention, the graphene oxide solution uses water as a solvent, and each milliliter of the solution contains 0.5-3 mg of graphene oxide.

[0014] Electrochemical sensor, using any one of the above GO / Mg-Fe-LDH modified electrodes as the working electrode of the electrochemical sensor.

[0015] As a further solution of the present invention: an electrochemical sensor is used to detect the content of mycophenolic acid.

[0016] Beneficial effects of the present invention:

[0017] This invention modifies a working electrode using graphene oxide and magnesium-iron double hydroxide to produce a GO / Mg-Fe-LDH modified electrode. First, the electrode is surface-modified with Mg-Fe-LDH, a material with improved conductivity, resulting in more stable sensing performance. GO is then used to modify the electrode with the magnesium-iron double hydroxide layer, providing a large effective surface area, facilitating adsorption of the analyte and improving sensor sensitivity. This electrode, used as the working electrode in an electrochemical sensor, is suitable for detecting mycophenolic acid (MPA) in feed. The modified electrode prepared in this application has a large surface area, providing more active sites for the reaction, significantly improving the sensor's sensitivity to the target molecule. The material's excellent catalytic properties significantly enhance the charge transfer rate. Specific groups on the graphene oxide surface enhance the specific catalysis of the target molecule, significantly improving the sensor's specificity. Compared to traditional MPA detection methods such as chromatography-tandem mass spectrometry, high-performance liquid chromatography, and gas chromatography, the sensor presented in this invention offers advantages such as low cost, simple operation, and rapid response. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1 This is a graph showing the detection data of mycophenolic acid concentration by the modified electrode prepared in Example 1 of the present application;

[0020] Figure 2 This is a graph showing the effective specific surface area of ​​the modified electrodes prepared in Example 1 and Comparative Examples 1-2 of the present application;

[0021] Figure 3 This is the cycle stability test curve of the modified electrode prepared in this application

[0022] Figure 4 This is a diagram showing the repeatability and reproducibility of the modified electrode prepared in this application;

[0023] Figure 5 This is a specific detection curve diagram of the modified electrode prepared in this application. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] Example 1 A method for preparing a GO / Mg-Fe-LDH modified electrode comprises the following steps:

[0026] S1: Prepare a 4 mmol / L potassium ferrocyanide solution (containing 0.1 mol / L potassium chloride): Weigh 1.055 g potassium ferrocyanide trihydrate, 0.823 g potassium ferrocyanide, and 3.727 g potassium chloride into a 100 mL beaker and dissolve in ultrapure water. Transfer to a 500 mL volumetric flask and dilute to the mark with ultrapure water to obtain a 5 mmol / L potassium ferrocyanide solution.

[0027] S2: Pretreatment: Sprinkle polishing powder (Al2O3) on the suede and then add ultrapure water and stir to form a homogenate. Polish the glassy carbon electrode (GCE) on the homogenate perpendicular to the suede in a circular motion. Then, ultrasonicate it in ultrapure water, anhydrous ethanol, and ultrapure water for 30 seconds each. Note that the electrode should be tilted in the beaker and then blown dry for later use.

[0028] Test the pretreated glassy carbon electrode in the potassium ferrocyanide solution prepared in S1 in cyclic voltammetry (CV) mode. If the difference between the two peak voltages is less than 0.1 V, the grinding is qualified. Otherwise, repeat the above steps until the difference between the two peak voltages is less than 0.1 V (CV parameter settings: potential range -0.2-0.6 V, scan speed 50 mV / s, initial scan polarity: positive, scan rate 0.05 V / s, number of scan segments 2, sampling interval 0.001 V, standing time 2 seconds, sensitivity 1.e-004 A / V);

[0029] S3: Weigh 1.0 mg of Mg-Fe-LDH (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) and place it in a 2 mL centrifuge tube. Add 1 mL of ultrapure water and sonicate until no obvious particles are left at the bottom of the centrifuge tube to obtain a Mg-Fe-LDH solution.

[0030] 1.5 mg of GO (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) was weighed and placed in a 2 mL centrifuge tube. 1 mL of ultrapure water was added and ultrasonicated until no obvious particles were left at the bottom of the centrifuge tube to obtain a GO solution.

[0031] Use a pipette to accurately draw 5 μL of the above-configured Mg-Fe-LDH solution and drop it onto the electrode surface, then place it in an oven for drying to obtain an electrode with a magnesium-iron double hydroxide layer on the surface; drop 5 μL of the above-configured GO solution on the surface of the electrode with the magnesium-iron double hydroxide layer, and dry it again to obtain a GO / Mg-Fe-LDH modified electrode.

[0032] Example 2 A method for preparing a GO / Mg-Fe-LDH modified electrode comprises the following steps:

[0033] S1: Prepare a 4 mmol / L potassium ferrocyanide solution (containing 0.1 mol / L potassium chloride): Weigh 1.055 g potassium ferrocyanide trihydrate, 0.823 g potassium ferrocyanide, and 3.727 g potassium chloride into a 100 mL beaker and dissolve in ultrapure water. Transfer to a 500 mL volumetric flask and dilute to the mark with ultrapure water to obtain a 5 mmol / L potassium ferrocyanide solution.

[0034] S2: Pretreatment: Sprinkle polishing powder (Al2O3) on the suede and then add ultrapure water and stir to form a homogenate. Polish the glassy carbon electrode (GCE) on the homogenate perpendicular to the suede in a circular motion. Then, ultrasonicate it in ultrapure water, anhydrous ethanol, and ultrapure water for 30 seconds each. Note that the electrode should be tilted in the beaker and then blown dry for later use.

[0035] Test the pretreated glassy carbon electrode in the potassium ferrocyanide solution prepared in S1 in cyclic voltammetry (CV) mode. If the difference between the two peak voltages is less than 0.1 V, the grinding is qualified. Otherwise, repeat the above steps until the difference between the two peak voltages is less than 0.1 V (CV parameter settings: potential range -0.2-0.6 V, scan speed 50 mV / s, initial scan polarity: positive, scan rate 0.05 V / s, number of scan segments 2, sampling interval 0.001 V, standing time 2 seconds, sensitivity 1.e-004 A / V);

[0036] S3: Weigh 0.5 mg of Mg-Fe-LDH (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) and place it in a 2 mL centrifuge tube. Add 1 mL of ultrapure water and sonicate until no obvious particles are left at the bottom of the centrifuge tube to obtain a Mg-Fe-LDH solution.

[0037] 0.5 mg of GO (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) was weighed and placed in a 2 mL centrifuge tube. 1 mL of ultrapure water was added and ultrasonicated until no obvious particles were left at the bottom of the centrifuge tube to obtain a GO solution.

[0038] Use a pipette to accurately draw 5 μL of the above-configured Mg-Fe-LDH solution and drop it onto the electrode surface, then place it in an oven for drying to obtain an electrode with a magnesium-iron double hydroxide layer on the surface; drop 5 μL of the above-configured GO solution on the surface of the electrode with the magnesium-iron double hydroxide layer, and dry it again to obtain a GO / Mg-Fe-LDH modified electrode.

[0039] Example 3 A method for preparing a GO / Mg-Fe-LDH modified electrode comprises the following steps:

[0040] S1: Prepare a 4 mmol / L potassium ferrocyanide solution (containing 0.1 mol / L potassium chloride): Weigh 1.055 g potassium ferrocyanide trihydrate, 0.823 g potassium ferrocyanide, and 3.727 g potassium chloride into a 100 mL beaker and dissolve in ultrapure water. Transfer to a 500 mL volumetric flask and dilute to the mark with ultrapure water to obtain a 5 mmol / L potassium ferrocyanide solution.

[0041] S2: Pretreatment: Sprinkle polishing powder (Al2O3) on the suede and then add ultrapure water and stir to form a homogenate. Polish the glassy carbon electrode (GCE) on the homogenate perpendicular to the suede in a circular motion. Then, ultrasonicate it in ultrapure water, anhydrous ethanol, and ultrapure water for 30 seconds each. Note that the electrode should be tilted in the beaker and then blown dry for later use.

[0042] Test the pretreated glassy carbon electrode in the potassium ferrocyanide solution prepared in S1 in cyclic voltammetry (CV) mode. If the difference between the two peak voltages is less than 0.1 V, the grinding is qualified. Otherwise, repeat the above steps until the difference between the two peak voltages is less than 0.1 V (CV parameter settings: potential range -0.2-0.6 V, scan speed 50 mV / s, initial scan polarity: positive, scan rate 0.05 V / s, number of scan segments 2, sampling interval 0.001 V, standing time 2 seconds, sensitivity 1.e-004 A / V);

[0043] S3: Weigh 3 mg of Mg-Fe-LDH (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) and place it in a 2 mL centrifuge tube. Add 1 mL of ultrapure water and sonicate until no obvious particles are left at the bottom of the centrifuge tube to obtain a Mg-Fe-LDH solution.

[0044] 3 mg of GO (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) was weighed and placed in a 2 mL centrifuge tube. 1 mL of ultrapure water was added and ultrasonicated until no obvious particles were left at the bottom of the centrifuge tube to obtain a GO solution.

[0045] Use a pipette to accurately draw 5 μL of the above-configured Mg-Fe-LDH solution and drop it onto the electrode surface, then place it in an oven for drying to obtain an electrode with a magnesium-iron double hydroxide layer on the surface; drop 5 μL of the above-configured GO solution on the surface of the electrode with the magnesium-iron double hydroxide layer, and dry it again to obtain a GO / Mg-Fe-LDH modified electrode.

[0046] Comparative Example 1 A method for preparing a graphene oxide modified electrode comprises the following steps:

[0047] S1: Prepare a 4 mmol / L potassium ferrocyanide solution (containing 0.1 mol / L potassium chloride): Weigh 1.055 g potassium ferrocyanide trihydrate, 0.823 g potassium ferrocyanide, and 3.727 g potassium chloride into a 100 mL beaker and dissolve in ultrapure water. Transfer to a 500 mL volumetric flask and dilute to the mark with ultrapure water to obtain a 5 mmol / L potassium ferrocyanide solution.

[0048] S2: Pretreatment: Sprinkle polishing powder (Al2O3) on the suede and then add ultrapure water and stir to form a homogenate. Polish the glassy carbon electrode (GCE) on the homogenate perpendicular to the suede in a circular motion. Then, ultrasonicate it in ultrapure water, anhydrous ethanol, and ultrapure water for 30 seconds each. Note that the electrode should be tilted in the beaker and then blown dry for later use.

[0049] Test the pretreated glassy carbon electrode in the potassium ferrocyanide solution prepared in S1 in cyclic voltammetry (CV) mode. If the difference between the two peak voltages is less than 0.1 V, the grinding is qualified. Otherwise, repeat the above steps until the difference between the two peak voltages is less than 0.1 V (CV parameter settings: potential range -0.2-0.6 V, scan speed 50 mV / s, initial scan polarity: positive, scan rate 0.05 V / s, number of scan segments 2, sampling interval 0.001 V, standing time 2 seconds, sensitivity 1.e-004 A / V);

[0050] S3: Weigh 1.5 mg of GO (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) and place it in a 2 mL centrifuge tube. Add 1 mL of ultrapure water and sonicate until no obvious particles are left at the bottom of the centrifuge tube to obtain a GO solution.

[0051] Use a pipette to accurately draw 5 μL of the above-prepared GO solution and drop-coat it on the electrode surface, then place it in an oven to dry to obtain a modified electrode.

[0052] Comparative Example 2 A method for preparing a magnesium-iron double hydroxide modified electrode comprises the following steps:

[0053] S1: Prepare a 4 mmol / L potassium ferrocyanide solution (containing 0.1 mol / L potassium chloride): Weigh 1.055 g potassium ferrocyanide trihydrate, 0.823 g potassium ferrocyanide, and 3.727 g potassium chloride into a 100 mL beaker and dissolve in ultrapure water. Transfer to a 500 mL volumetric flask and dilute to the mark with ultrapure water to obtain a 5 mmol / L potassium ferrocyanide solution.

[0054] S2: Pretreatment: Sprinkle polishing powder (Al2O3) on the suede and then add ultrapure water and stir to form a homogenate. Polish the glassy carbon electrode (GCE) on the homogenate perpendicular to the suede in a circular motion. Then, ultrasonicate it in ultrapure water, anhydrous ethanol, and ultrapure water for 30 seconds each. Note that the electrode should be tilted in the beaker and then blown dry for later use.

[0055] Test the pretreated glassy carbon electrode in the potassium ferrocyanide solution prepared in S1 in cyclic voltammetry (CV) mode. If the difference between the two peak voltages is less than 0.1 V, the grinding is qualified. Otherwise, repeat the above steps until the difference between the two peak voltages is less than 0.1 V (CV parameter settings: potential range -0.2-0.6 V, scan speed 50 mV / s, initial scan polarity: positive, scan rate 0.05 V / s, number of scan segments 2, sampling interval 0.001 V, standing time 2 seconds, sensitivity 1.e-004 A / V);

[0056] S3: Weigh 1.0 mg of Mg-Fe-LDH (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) and place it in a 2 mL centrifuge tube. Add 1 mL of ultrapure water and sonicate until no obvious particles are left at the bottom of the centrifuge tube to obtain a Mg-Fe-LDH solution.

[0057] 5 μL of the above-prepared Mg-Fe-LDH solution was accurately drawn with a pipette and drop-coated on the electrode surface, which was then placed in an oven for drying to obtain modification.

[0058] Performance testing

[0059] (1) Detection of mycophenolic acid concentration

[0060] a. Build system:

[0061] The modified electrode prepared in Example 1 was used as the working electrode of the electrochemical sensor, a platinum wire counter electrode, Ag / AgCl as the reference electrode, and a CHI760E electrochemical workstation to form a three-electrode sensing system;

[0062] b. Test solution configuration:

[0063] Preparation of MPA standard solution: Accurately weigh 10.0 mg of MPA standard sample into a 10 mL volumetric flask, dilute to the mark with anhydrous ethanol, tighten the bottle with the stopper, and shake it upside down to dissolve it to obtain an MPA solution with a concentration of 1 mg / ml. Store it in a refrigerator at 4°C. When used, take it out and dilute it with PBS to the target concentration before use.

[0064] Prepare PBS buffer solution: Weigh 15.601g of sodium dihydrogen phosphate dihydrate and 9.0g of sodium chloride into a 500ml beaker and dissolve them with ultrapure water. Transfer the solution to a 1000ml volumetric flask and dilute to the mark with ultrapure water to create a 0.1 mol / L phosphate buffer stock solution. Adjust the pH to 3.5 with 1 mol / mL NaOH and analytical grade phosphoric acid before use. Phosphate buffer acts as an electrolyte, providing electrolytes and reducing solution resistance.

[0065] c. Establishment of the linear regression equation of the standard curve of mycophenolic acid electrochemical sensor:

[0066] See also Figure 1 ,like Figure 1 As shown in Figure (A), with a pH of 2.0 and 0.1 mol / L PBS buffer solution as the electrolyte, the three-electrode sensing system constructed above was used to perform differential pulse voltammetry (DPV) detection on MPA with different concentrations (4.17, 7.29, 10.42, 13.54, 19.79, 26.04, 32.29, and 38.54 μmol / L), and the peak currents of the MPA test solutions with different concentrations were obtained; Figure 1 As shown in Figure (B), the standard curve was established with MPA concentration as the independent variable and the peak current of the test solution with different concentrations of MPA as the dependent variable. The linear equation is y=0.01712x-0.06352(R 2 =0.9034), the concentration detection range was 4.1688138.5438 μmol / L, and the detection limit was 0.5337 μmol / L.

[0067] The DPV parameters were set as potential range 0.3–1.0 V, incremental potential 0.004 V, amplitude 0.05 V, pulse width 0.05 s, sampling width 0.0167 s, pulse period 0.5 s, and rest time 2 s.

[0068] d. Determination of mycophenolic acid concentration

[0069] The feed sample extract to be tested was added to a 0.1 mol / L PBS solution electrolyte at a pH of 2.0, and DPV measurement was performed using the three-electrode sensing system configured as described above to obtain the peak current value. The MPA concentration was obtained based on the linear regression equation of the standard curve of the mycophenolic acid electrochemical sensor established above.

[0070] (2) Determination of effective specific surface area of ​​electrochemical sensor: CV scanning was performed on the modified electrodes prepared in Example 1 and Comparative Examples 1-2 in 5 mmol / L potassium ferricyanide solution. The scanning rates were set to 25, 50, 75, 100, 125, 150, 200, 250, 300, 350, 400, 450, and 500 mV / s to explore the electrochemical active area of ​​the sensor. The results are shown in Figure 2. Figure 2 shown. Figure 2 Figure (A) shows the Ip-v of the modified electrode prepared in Comparative Example 1 in 5 mmol / L potassium ferricyanide solution. 1 / 2 curve, Figure 2 Figure (B) shows the CV curves of the modified electrode prepared in Comparative Example 1 at different scan rates; Figure 2 Figure (C) shows the Ip-v of the modified electrode prepared in Comparative Example 2 in 5 mmol / L potassium ferricyanide solution. 1 / 2 curve, Figure 2Figure (D) in the middle is the CV curves of the modified electrode prepared in Comparative Example 2 at different scan rates; Figure 2 Figure (E) shows the Ip-v of the modified electrode prepared in Example 1 in 5 mmol / L potassium ferricyanide solution. 1 / 2 curve, Figure 2 Figure (F) shows the CV curves of the modified electrode prepared in Example 1 at different scan rates; according to the Randles–Sevick equation, and the Ip-v of each electrode 1 / 2 The effective surface area of ​​the electrode can be calculated from the curve. The effective specific surface area of ​​the modified electrode prepared in Example 1 is calculated to be 0.068 cm 2 The effective specific surface area of ​​the modified electrode prepared in Comparative Example 1 is 0.015 cm 2 The effective specific surface area of ​​the modified electrode prepared in Comparative Example 2 is 0.028 cm 2 ; It can be seen that compared with the electrode modified with a single material, the modified electrode prepared in this application is modified by Mg-Fe-LDH and GO, and has a larger effective surface area, that is, it has a higher electrochemical activity, which confirms that the modified electrode prepared in this application is more advantageous.

[0071] (3) Cyclic stability test: Using the three-electrode sensing system described in (1), CV scans were performed for 100 cycles in potassium ferricyanide solution, and the current values ​​were recorded and the relative standard deviation (RSD) of the current was calculated to test the stability of the electrode. Figure 3 As shown in Figure (A), the RAD of the modified electrode is 1.92% (anodic peak) and 1.47% (cathodic peak), indicating high surface stability. Figure 3 The middle (B) figure is the CV curve.

[0072] (4) Repeatability and reproducibility test: Using the three-electrode sensing system described in (1), 3.125 μmol / L MPA solution (pH = 2.0) was scanned 20 times in DPV mode, the peak current value was recorded, and the RSD of the current values ​​of these 20 times was calculated. The results are as follows: Figure 4 shown. Figure 4 The result shown in Figure (A) is RSD=1.74%<5%. Six more modified electrodes were prepared and tested under the same conditions. The RSD of the peak current of these six modified electrodes was calculated, as shown in Figure 1. Figure 4 The results shown in Figure (B) show an RSD of 1.77% (<5%), indicating that the sensor prepared in this invention has good reproducibility for MPA detection. These good repeatability and reproducibility demonstrate the electrode's excellent stability and suitability for practical production applications.

[0073] (5) Specific detection: The GO / Mg-Fe-LDH modified electrode prepared by the present invention was used as a working electrode in an electrochemical sensor. The electrode detected several substances commonly found in MPA and silage, such as sodium chloride, potassium chloride, L-isoleucine, L-leucine, glucose, sucrose, and citric acid. The DPV responses to these substances were as follows: Figure 5 As shown in the figure, it can be seen that the interfering substance does not produce a redox peak and the measured redox peak of MPA has a high degree of overlap with the redox peak of MPA without the addition of the interfering substance. This shows that the sensor prepared by the present invention has high resistance to interference from other interfering substances and has strong specificity.

[0074] (6) Actual sample detection: The silage sample extract was diluted with PBS buffer at pH 2.0, and MPA standard was added to make the actual concentration reach 5 μmol / L and 10 μmol / L respectively. The working electrode, counter electrode and reference electrode were immersed in the test solution. The peak current value was obtained by DPV method. The MPA concentration was calculated according to the linear regression equation of the standard curve of the mycophenolic acid electrochemical sensor, and the recovery rate and RSD were calculated. The test results are shown in Table 1;

[0075] Table 1: Electrochemical sensor recovery results for MPA spiked in silage samples

[0076]

[0077] The results are shown in Table 1. The recovery rate of corn silage is between 93.5% and 99.2%, and the RSD is between 0.23% and 0.82%, which proves that the GO / Mg-Fe-LDH modified electrode prepared in this application can be used as a working electrode in the electrochemical sensor, and the electrochemical sensor can be used for the actual detection of MPV.

[0078] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. Application of a GO / Mg-Fe-LDH modified electrode in the detection of mycophenolic acid content, characterized in that: The modified electrode consists of a working electrode and a magnesium-iron double hydroxide layer and a graphene oxide layer wrapped inside and outside on the surface of the working electrode. The GO / Mg-Fe-LDH modified electrode serves as the working electrode of the electrochemical sensor. coating a magnesium-iron layered double hydroxide solution on the surface of the working electrode and drying the solution to obtain a magnesium-iron double hydroxide layer; The magnesium-iron layered double metal hydroxide solution uses water as a solvent, and each milliliter of the solution contains 0.5-3 mg of magnesium-iron layered double metal hydroxide; A graphene oxide solution is coated on the surface of the working electrode coated with the magnesium-iron double hydroxide layer and dried to obtain a modified electrode coated with the magnesium-iron double hydroxide layer and the graphene oxide layer from the inside out; The graphene oxide solution uses water as a solvent, and each milliliter of the solution contains 0.5-3 mg of graphene oxide.

2. The use of the GO / Mg-Fe-LDH modified electrode according to claim 1 in the detection of mycophenolic acid content, characterized in that: The working electrode is any one of a glassy carbon electrode, a platinum electrode, a gold electrode, and a copper electrode.

3. The use of the GO / Mg-Fe-LDH modified electrode according to claim 1 in the detection of mycophenolic acid content, characterized in that: The working electrode is pretreated before being coated with the magnesium-iron layered double hydroxide solution; the pretreatment step includes placing the working electrode in a slurry containing polishing powder for polishing; The difference between the two peak voltages of the working electrode obtained after pretreatment is less than 0.1V.

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