A molecularly imprinted ratio-type working electrode for detecting mitomycin C, and a preparation method and application thereof

Abstract

The application discloses a molecular imprinting ratio type working electrode for detecting mitomycin C and a preparation method and application thereof, and belongs to the technical field of analysis and detection. The application aims to solve the problem of simple and accurate detection of the content of mitomycin C (MMC). The application adopts a solvothermal reaction to prepare cerium-nickel bimetallic organic framework material, adopts ultrasonic reaction to prepare cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material, and adopts the cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material and thionine as a modification material of an electrochemical sensing interface. A molecular imprinting ratio type electrochemical sensor with specific recognition response to a template molecule MMC is prepared on the surface of the modified electrode through an electrochemical polymerization method. The application is applied to the detection of the content of MMC, and has the advantages of simple operation, low cost, high sensitivity and good selectivity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of analytical detection, and particularly relates to a molecular imprinting ratio type working electrode for detecting mitomycin C (MMC) and a preparation method and application thereof. BACKGROUND

[0002] Mitomycin C (MMC) is a natural compound derived from Streptomyces, which belongs to the antitumor antibiotic chemotherapeutic drug and has good efficacy for gastric cancer, intestinal cancer, liver cancer, etc. At present, the determination of the content of mitomycin mainly includes ultraviolet spectrophotometry, high performance liquid chromatography, capillary electrophoresis, etc. Although the above methods are relatively mature, such methods have the disadvantages of expensive instruments, long experimental period, complicated operation and inability to realize portability. Compared with other detection methods, the electrochemical method is concerned due to its simple equipment, convenient operation, low consumption and high sensitivity. The biggest advantage is that it can directly detect without pre-treatment. There are reports on the determination of the content of mitomycin by the electrochemical method, but the detection sensitivity and selectivity of the method need to be further improved. Therefore, the development of a high-precision detection method for the content of mitomycin can provide certain theoretical and technical support for the production and quality control of mitomycin. SUMMARY

[0003] The present application provides a method for preparing a molecular imprinting ratio type working electrode for detecting mitomycin C, which is used as an electrochemical sensor working electrode and is used for high-precision detection of the content of MMC.

[0004] In order to solve the above technical problems, the present application adopts the following technical solutions:

[0005] The present application uses cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material and thionine as the modification materials of the electrode, which is used for improving the conductivity and electroactive area of the bare glassy carbon electrode. Thionine is also used as a reference probe for electrochemical detection, which is used for improving the detection accuracy. On the surface of the modified electrode, o-phenylenediamine (O-PD) is used as a functional monomer for preparing a molecular imprinting film, and a molecular imprinting ratio type electrochemical sensor with specific response to MMC is constructed. The electrode prepared by the method of the present application has high sensitivity, good selectivity, and the test accuracy is greatly improved after the introduction of the reference probe.

[0006] The present application adopts solvothermal reaction to prepare cerium-nickel bimetallic organic framework material, adopts ultrasonic reaction to prepare cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material, and adopts cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material and thionine as a modified material of an electrochemical sensing interface. A molecularly imprinted ratio type electrochemical sensor with specific recognition response to a template molecule MMC is prepared on the surface of the modified electrode by an electrochemical polymerization method. The present application introduces a ratio detection strategy, takes the electrochemical response of polythionine and potassium ferricyanide as a reference probe signal and a detection signal respectively, combines a molecular imprinting technology, prepares a molecularly imprinted ratio type electrochemical sensor with specific recognition response to MMC molecules, and applies it to the detection of MMC content, which has the advantages of simple operation, low cost, high sensitivity and good selectivity.

[0007] Based on the rapid detection of MMC sample content, the factors affecting the electrochemical performance mainly include the ratio of functional monomer to template molecule, elution conditions and the like. The above conditions are optimized to construct a molecularly imprinted ratio type electrochemical sensor with specific recognition to MMC.

[0008] The present application aims to provide a method for preparing a molecularly imprinted ratio type working electrode for detecting mitomycin C (MMC), which comprises the following steps:

[0009] Step 1: dispersing cerium salt and nickel salt in N,N-dimethylformamide to obtain solution A, dispersing organic ligand in anhydrous ethanol to obtain solution B, mixing solution A and B, performing solvothermal reaction, and after the reaction is completed, washing and vacuum drying to obtain cerium-nickel bimetallic organic framework material;

[0010] Step 2: dispersing the cerium-nickel bimetallic organic framework material and multi-walled carbon nanotubes in a solvent, and performing ultrasonic reaction to prepare cerium-nickel bimetallic organic framework material / multi-walled carbon nanotube composite material;

[0011] Step 3: adding a fixing agent to the composite material obtained in step 2, uniformly mixing, and then dropping and coating on a glassy carbon electrode, drying to form a film, and then placing the modified glassy carbon electrode in a thionine phosphate buffer solution, and electrochemically polymerizing a film, and naturally drying to obtain a modified electrode;

[0012] Step 4: placing the modified electrode in an O-PD and MMC phosphate buffer solution, electrochemically polymerizing a film, naturally drying, placing in a sulfuric acid solution for elution, drying, and obtaining the working electrode.

[0013] In an embodiment of the present application, in step 1, the cerium salt is Ce(NO3)3·6H2O.

[0014] In an embodiment of the present application, in step 1, the nickel salt is Ni(NO3)2·6H2O.

[0015] In one embodiment of the present application, in step 1, the organic ligand is 1,3,5-benzenetricarboxylic acid.

[0016] In one embodiment of the present application, in step 1, the molar ratio of cerium salt, nickel salt and organic ligand is 6:4:2.

[0017] In one embodiment of the present application, in step 1, the solvent-thermal reaction is carried out at 120°C for 12 h.

[0018] In one embodiment of the present application, in step 1, after the solid-liquid separation by centrifugation, the solid is collected, then washed with N,N-dimethylformamide three times, and then washed with anhydrous ethanol until neutral.

[0019] In one embodiment of the present application, in step 2, the mass ratio of cerium-nickel bimetallic organic framework material and multi-walled carbon nanotubes is 1:5.

[0020] In one embodiment of the present application, in step 3, the fixing agent is a 0.5wt.% chitosan solution, and the volume ratio of the composite material to the fixing agent is 3:1.

[0021] In one embodiment of the present application, in step 3, the drying is carried out in an oven at 50°C for 8 min-14 min.

[0022] In one embodiment of the present application, in step 3, the phosphate buffer solution of thionine is prepared by dissolving thionine in a phosphate buffer solution,

[0023] In one embodiment of the present application, in step 3, the concentration of thionine in the phosphate buffer solution of thionine is 5mM.

[0024] In one embodiment of the present application, in step 3, the pH value of the phosphate buffer solution in the phosphate buffer solution of thionine is 6.0.

[0025] In one embodiment of the present application, in step 3, the process parameters for electrochemical polymerization film formation are: scanning potential: -0.4V-0.4V, scanning number: 20 circles, scanning rate: 0.04 V·s -1 .

[0026] In one embodiment of the present application, in step 4, the phosphate buffer solution of O-PD and MMC is prepared by adding anhydrous ethanol solution of O-PD and anhydrous ethanol solution of MMC into a phosphate buffer solution; the concentration ratio of the anhydrous ethanol solution of O-PD to the anhydrous ethanol solution of MMC is (1-8):1, preferably 4:1.

[0027] In one embodiment of the present application, the concentration of O-PD in the phosphate buffer of O-PD and MMC in step 4 is 1 mM.

[0028] In one embodiment of the present application, the concentration of O-PD in the phosphate buffer of O-PD and MMC in step 4 is 1 mM-8 mM.

[0029] In one embodiment of the present application, the pH value of the phosphate buffer in the phosphate buffer of O-PD and MMC in step 4 is 7.0.

[0030] In one embodiment of the present application, the process parameters of electrochemical polymerization film in step 4 are: scanning potential: 0V-0.8V, scanning circle number: 40 circles, scanning rate: 0.05 V·s -1 .

[0031] In one embodiment of the present application, the process of eluting the template molecules in step 4 is to place the electrode in 0.1 M H2SO4 solution for elution.

[0032] Another object of the present application also provides a working electrode prepared by any of the above methods.

[0033] Another object of the present application also provides an electrochemical sensor comprising a working electrode prepared by any of the above methods.

[0034] Another object of the present application also provides the above molecularly imprinted ratiometric working electrode for use as a working electrode of an electrochemical sensor for electrochemical detection of MMC content; in particular, for electrochemical detection of MMC content in production and environmental samples.

[0035] The present application also provides a method for electrochemical detection of MMC content, which comprises the following processes:

[0036] A series of MMC samples with known concentrations are prepared, and the above molecularly imprinted ratiometric electrochemical sensor is used as a working electrode to detect the electrochemical signals of the MMC samples by square wave voltammetry (SWV), and the current signals of potassium ferricyanide (I Fe ) and polythionine (I Thi ) are obtained at the same time; the current ratio I Fe / I Thi is used to construct a linear relationship with the corresponding MMC concentration to obtain a MMC detection model.

[0037] In the method of the present application, the concentration range of the series of MMC samples is 0.1 nM-100 nM.

[0038] In the method of the present application, the content of MMC is determined by preparing a molecular imprinting ratio type electrochemical sensor. In order to evaluate the electrochemical performance of the prepared cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material, the cyclic voltammetry of the bare glassy carbon electrode, the cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material modified electrode, the thionine and cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material modified electrode, the electrode after electropolymerization of the molecular imprinting polymer, and the imprinted electrode after elution of the MMC molecule in potassium ferricyanide is confirmed (see Figure 1 ). Further, the ratio of the functional monomer and the template molecule is optimized, and it is found that when the concentration ratio of the functional monomer and the template molecule is 4:1, the detection performance of the prepared molecular imprinting ratio type electrochemical sensor for MMC is better (see Figure 2 ).

[0039] The prepared molecular imprinting ratio type electrochemical sensor of the present application is based on cerium-nickel bimetallic organic framework and multi-walled carbon nanotube, and is a molecular imprinting ratio type electrochemical sensor for high-sensitivity identification of MMC, which has high sensitivity (see Figure 3 ) and good selectivity (see Figure 4 ). It can be applied to the detection of the content of MMC in production and environmental samples.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] The prepared molecular imprinting ratio type electrochemical sensor of the present application is used for specific identification analysis technology of MMC. The traditional detection method of MMC has a long cycle and a complicated process, so a molecular imprinting ratio type electrochemical sensor is proposed, which is used for high-sensitivity identification of MMC in the environment and specific response. In the present application, the material of the modified electrode is simple to prepare and low in price, and the proposed detection method is SWV, which can quickly detect the concentration of MMC and has high sensitivity (see the attached Figure 3 ) in the concentration range of 0.1 nM-100 nM, the current ratio is linearly related to the logarithm of the concentration of MMC, the calculated detection limit is 0.03 nM, which is about 1 / 2 of the detection limit of the non-ratio electrochemical sensor, and has good selectivity (see Figure 4 ).

[0042] In order to further understand the features and technical contents of the present application, please refer to the following detailed description of the present application and the attached drawings, however, the attached drawings are provided for reference and illustration only, and are not used to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1The molecular imprinting ratio type electrochemical sensor diagram for different modified electrodes; wherein, A is a bare glassy carbon electrode, B is a cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode, C is a polythiophene pThi / cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode, D is an electrode after the electro-polymerization of a molecular imprinting film, and E is a molecular imprinting electrochemical sensor after elution.

[0044] Figure 2 The molecular imprinting ratio type electrochemical sensor response signal comparison diagram prepared by different concentrations of functional monomers and template molecules.

[0045] Figure 3 (A) is the SWV diagram of the molecular imprinting ratio type electrochemical sensor of the application for detecting different concentrations of MMC (the concentrations from a to e are 0.1, 0.5, 5, 10, and 100 nM, respectively). Figure 3 (B) is the linear relationship diagram of the molecular imprinting (MIP) and non-molecular imprinting (NIP) ratio electrochemical sensors constructed by the application for detecting MMC.

[0046] Figure 4 The selectivity performance comparison diagram of the molecular imprinting ratio type electrochemical sensor for MMC (1 nM) (a) MMC, (b) MMC + Oxytetracycline (OTC, 1 nM), (c) MMC + Penicillin (PG, 1 nM), (d) MMC + Roxithromycin (ROX, 1 nM). DETAILED DESCRIPTION

[0047] The application will be described in detail below with specific examples. The following examples will help those skilled in the art to further understand the application, and do not limit the application in any form. It should be noted that for those skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made. These all belong to the protection scope of the application.

[0048] Example 1: In this embodiment, the preparation method of the molecular imprinting ratio type working electrode for detecting mitomycin C is prepared according to the following steps:

[0049] Step 1, Preparation of Ce-Ni bimetallic organic framework material: 0.6 mmol Ce(NO3)3·6H2O and 0.4 mmol Ni(NO3)2·6H2O were dispersed in 18 mL of N,N-dimethylformamide (DMF) to obtain solution A, 0.2 mmol 1,3,5-benzenetricarboxylic acid was dispersed in 18 mL of anhydrous ethanol to obtain solution B, then solution A and B were mixed, and placed in a 100 mL polytetrafluoroethylene high-pressure reaction kettle, and subjected to a solvothermal reaction at a solvothermal reaction temperature of 120°C for 12 h. After the solvothermal reaction, the solid-liquid separation was performed by centrifugation, and the collected solid was washed with N,N-dimethylformamide (DMF) three times, and then washed with anhydrous ethanol until neutral, and placed in a vacuum drying box and dried at 60°C for 10 h to obtain the Ce-Ni bimetallic organic framework material.

[0050] Step 2, Preparation of Ce-Ni bimetallic organic framework / multi-walled carbon nanotube composite material: 2 mg of the Ce-Ni bimetallic organic framework material obtained in step 1 and 10 mg of multi-walled carbon nanotubes were placed in 10 mL of N,N-dimethylformamide, and subjected to ultrasonic reaction in an ultrasonic cleaner with a working frequency of 40 KHz and an ultrasonic electric power of 600 W, and the reaction time was 30 min and the reaction temperature was room temperature. After the ultrasonic reaction, the Ce-Ni bimetallic organic framework / multi-walled carbon nanotube composite material was obtained.

[0051] Step 3, Preparation of Ce-Ni bimetallic organic framework / multi-walled carbon nanotube composite material modified electrode: The Ce-Ni bimetallic organic framework / multi-walled carbon nanotube composite material obtained in step 2 was used to prepare a modified electrode: the above Ce-Ni bimetallic organic framework / multi-walled carbon nanotube composite material was mixed with a 0.5wt.% chitosan solution (fixing agent) until it was uniformly dispersed, and the volume ratio of the Ce-Ni bimetallic organic framework / multi-walled carbon nanotube composite material to the fixing agent was 3:1. 10 μL was taken and dropped on a polished glassy carbon electrode, and placed in a drying oven at 50°C for 12 min to obtain the modified electrode.

[0052] Step 4: Preparation of the polythionite pThi cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode: The modified electrode is prepared using the cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode obtained in Step 3. The cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode is placed in a phosphate buffer solution of thionite (prepared by dissolving thionite in phosphate buffer solution, with a thionite concentration of 5 mM and a pH of 6.0) for electrochemical polymerization to form a film. After polymerization, the electrode is allowed to dry naturally to obtain the modified electrode. The electropolymerization conditions in Step 4 are: scan potential: -0.4 V to 0.4 V, number of scans: 20, scan rate: 0.04 V·s. -1 .

[0053] Step 5: Preparation of the molecularly imprinted ratiometric working electrode: The modified electrode obtained in Step 4 was placed in a phosphate buffer solution of O-PD and MMC (prepared by adding anhydrous ethanol solutions of O-PD and MMC to the phosphate buffer solution, with an O-PD to MMC concentration ratio of 1:1, an MMC concentration of 1 mM, and a pH of 7.0 for electrochemical polymerization to form a film. The polymerized electrode was then allowed to dry naturally and subsequently eluted in a 0.1 M H₂SO₄ solution to obtain the molecularly imprinted ratiometric working electrode, which is used as the working electrode for an electrochemical sensor for the electrochemical detection of MMC content. The electropolymerization conditions in Step 5 were: scan potential: 0 V-0.8 V, number of scan cycles: 40, scan rate: 0.05 V·s. -1 .

[0054] Example 2: This example differs from Example 1 in that, in step 5, the modified electrode obtained in step 4 is placed in a phosphate buffer solution of O-PD and MMC (prepared by adding anhydrous ethanol solutions of O-PD and MMC to the phosphate buffer solution, with an O-PD to MMC concentration ratio of 2:1, an MMC concentration of 1 mM, and a buffer pH of 7.0) for electrochemical polymerization to form a film (electroplation conditions: scan potential: 0 V-0.8 V, scan cycles: 40 cycles, scan rate: 0.05 V·s). -1 After polymerization, the electrode is allowed to dry naturally, and then eluted in a 0.1 M H2SO4 solution to obtain a molecularly imprinted ratiometric working electrode, which is used as the working electrode of an electrochemical sensor for the electrochemical detection of MMC content. Other steps and parameters are the same as in Example 1.

[0055] Example 3: The difference between this example and Example 1 is that in step 5, the modified electrode obtained in step 4 is placed in a phosphate buffer solution of O-PD and MMC (prepared by adding anhydrous ethanol solutions of O-PD and MMC into a phosphate buffer solution, the concentration ratio of O-PD to MMC is 4:1, the concentration of MMC is 1 mM, and the pH of the buffer solution is 7.0), and electrochemical polymerization is performed (electropolymerization conditions: scan potential: 0 V-0.8 V, scan number: 40, scan rate: 0.05 V·s -1 ). After that, the polymerized electrode is naturally placed to dry, and then is placed in a 0.1 M H2SO4 solution for elution, thereby obtaining a molecularly imprinted ratio-type working electrode, which is used as a working electrode of an electrochemical sensor for the electrochemical detection of MMC content. The other steps and parameters are the same as in Example 1.

[0056] Example 4: The difference between this example and Example 1 is that in step 5, the modified electrode obtained in step 4 is placed in a phosphate buffer solution of O-PD and MMC (prepared by adding anhydrous ethanol solutions of O-PD and MMC into a phosphate buffer solution, the concentration ratio of O-PD to MMC is 8:1, the concentration of MMC is 1 mM, and the pH of the buffer solution is 7.0), and electrochemical polymerization is performed (electropolymerization conditions: scan potential: 0 V-0.8 V, scan number: 40, scan rate: 0.05 V·s -1 ). After that, the polymerized electrode is naturally placed to dry, and then is placed in a 0.1 M H2SO4 solution for elution, thereby obtaining a molecularly imprinted ratio-type working electrode, which is used as a working electrode of an electrochemical sensor for the electrochemical detection of MMC content. The other steps and parameters are the same as in Example 1.

[0057] Performance study of a molecularly imprinted ratio-type electrochemical sensor for MMC detection

[0058] The following tests are used to verify the effect of the application:

[0059] Test 1: MMC detection

[0060] In a mixture of 2.5 mM K3[Fe(CN)6] and 0.1 M KCl, the molecularly imprinted ratio-type working electrode obtained in Example 3 is used as the working electrode of an electrochemical sensor, an Ag / AgCl electrode is used as the reference electrode, and a platinum wire electrode is used as the auxiliary electrode. The electrochemical signal is detected by SWV technology, and the corresponding current ratio I Fe / I Thi is measured; a linear detection model is constructed using the current ratio I Fe / I Thi and the corresponding MMC concentration, as shown in Figure 3As shown. It can be seen that in the concentration range of 0.1 nM-100 nM, with the increase of the concentration of MMC, the current ratio decreases, the current ratio is linearly related to the logarithm of the concentration of MMC, and the detection limit is 0.03 nM.

[0061] Test 2: Explore the influence of different O-PD and MMC concentration ratios on the molecular imprinting ratio type electrochemical sensor obtained

[0062] Preparation of the molecular imprinting ratio type electrochemical sensor: the modified electrode obtained in step 4 of the above embodiment 1 was placed in a phosphate buffer solution containing O-PD and MMC (the concentration ratio of O-PD to MMC was 8:1, the concentration of MMC was 1 mM, and the pH of the buffer was 7.0), and electrochemical polymerization film was performed (the electrochemical polymerization conditions were: scan potential: 0 V-0.8 V, scan number: 40, scan rate: 0.05 V·s-1), then the polymerized electrode was naturally placed to dry, and then was placed in a 0.1 M H2SO4 solution for elution, thereby obtaining a molecular imprinting ratio type working electrode, which was used as an electrochemical sensor working electrode for electrochemical detection of MMC content.

[0063] The molecular imprinting ratio type working electrodes prepared with the concentration ratios of O-PD to MMC being 1:1, 2:1, 4:1, and 8:1 were used as the working electrodes of the electrochemical sensor, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the auxiliary electrode to construct the molecular imprinting electrochemical sensor; then the above molecular imprinting electrochemical sensor was placed in a 1 nM MMC solution for adsorption, the adsorption time was 8 min, the electrochemical sensor was taken out, and the electrochemical response signal was tested.

[0064] Electrochemical test of sensors prepared with different O-PD / MMC concentration ratios: the sensors prepared with different O-PD / MMC concentration ratios were placed in a mixture of 2.5 mM K3[Fe(CN)6] and 0.1 M KCl, and the electrochemical signal was tested by SWV technology. As shown in Figure 2 , when the concentration ratio was 1:1, 2:1, and 8:1, the current ratio I Fe / I Thi was higher, the polymerization effect was poorer, and the obtained molecular imprinting ratio type electrochemical sensor could not be used for subsequent specific content detection; when the concentration ratio was 4:1, the current ratio I Fe / I Thi was the lowest, the polymerization effect was the best, and a high-sensitivity detection model shown in test 1 could be constructed.

[0065] Test 3: Selectivity evaluation of the analysis method

[0066] A molecularly imprinted electrochemical sensor was constructed in a mixture of 2.5 mM K3[Fe(CN)6] and 0.1 M KCl, using the molecularly imprinted working electrode from Experiment 2 as the working electrode of the electrochemical sensor, an Ag / AgCl electrode as the reference electrode, and a platinum wire electrode as the auxiliary electrode.

[0067] Using structural analogs of MMC, oxytetracycline (OTC), penicillin (PEG), and roxithromycin (ROX), as interfering substances, the electrochemical response signals of the same concentration of MMC (1 nM) were investigated with and without the addition of interfering substances, and It was calculated. P / I A Value(I P I represents the presence of interfering substances Fe / I Thi I A When representing no interfering substances, I Fe / I Thi The performance of the selection method is evaluated by the magnitude of the current ratio.

[0068] The results are as follows Figure 4 As shown, I P / I A The variation value was between 97% and 105%, which was relatively small, indicating that the prepared molecularly imprinted ratiometric electrochemical sensor has high specificity for MMC. This detection method exhibits good selectivity and can achieve specific detection of MMC.

[0069] The specific embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a molecularly imprinted ratiometric working electrode for detecting mitomycin C, characterized in that, Includes the following steps: Step 1: Disperse cerium salt and nickel salt in N,N-dimethylformamide to obtain solution A, and disperse the organic ligand in anhydrous ethanol to obtain solution B. Mix solutions A and B and carry out a solvothermal reaction. After the reaction is completed, centrifuge, wash and vacuum dry to obtain cerium-nickel bimetallic organic framework material. Step 2: Disperse the cerium-nickel bimetallic organic framework material and multi-walled carbon nanotubes in a solvent and perform an ultrasonic reaction; Step 3: Then add the fixative, mix well, drop-coat it onto the glassy carbon electrode, dry it, and then place it in the phosphate buffer of thionine to electrochemically polymerize into a film. After natural drying, the modified electrode is obtained. Step 4: Place the modified electrode in a phosphate buffer solution of O-PD and MMC, electrochemically polymerize it into a film, allow it to dry naturally, elute it in a sulfuric acid solution, and dry it to obtain the working electrode.

2. The method according to claim 1, characterized in that, The cerium salt is Ce(NO3)3·6H2O; the nickel salt is Ni(NO3)2·6H2O; and the organic ligand is 1,3,5-benzenetricarboxylic acid.

3. The method according to claim 1, characterized in that, The molar ratio of cerium salt, nickel salt and organic ligand was 6:4:2; the reaction was carried out at 120℃ for 12 h; the washing was performed by washing three times with N,N-dimethylformamide, followed by washing with anhydrous ethanol until neutral.

4. The method according to claim 1, characterized in that, In step 2, the solvent is N,N-dimethylformamide, and the mass ratio of cerium-nickel bimetallic organic framework material to multi-walled carbon nanotubes is 1:

5.

5. The method according to claim 1, characterized in that, In step 3, the fixative was a 0.5 wt.% chitosan solution; the concentration of thionine was 5 mM; the pH of the phosphate buffer was 6.0; the parameters for electrochemical polymerization film formation were: scan potential: -0.4 V to 0.4 V, number of scans: 20, scan rate: 0.04 V·s. -1 .

6. The method according to claim 1, characterized in that, In step 4, the concentration of MMC is 1 mM, the concentration of O-PD is 1 mM-8 mM, and the pH of the phosphate buffer is 7.

0.

7. The method according to claim 1, characterized in that, The process parameters for electrochemical polymerization film formation are as follows: scan potential: 0V-0.8V, number of scans: 40, scan rate: 0.05 V·s. -1 The concentration of the sulfuric acid solution is 0.1 M.

8. A working electrode prepared by the method according to any one of claims 1-7.

9. An electrochemical sensor, characterized in that, The working electrode includes one prepared by the method according to any one of claims 1-7.

10. A working electrode prepared by the method of any one of claims 1-7 for electrochemical detection of MMC content.

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