Preparation method and application of electrochemical sensor for detecting norfloxacin in water

Abstract

The invention relates to a preparation method and application of an electrochemical sensor for detecting norfloxacin in water, a boron-doped diamond (BDD) electrode is modified by adopting a multi-walled carbon nanotube and gold nanoparticles, and the sensitivity of the electrode is enhanced; and preparing a layer of molecular imprinting film on the surface of a boron-doped diamond (BDD) electrode by taking norfloxacin as an imprinting molecule and adopting an electrochemical in-situ electropolymerization technology, so as to improve the specificity of the electrode and construct an electrochemical sensor for detecting norfloxacin in water. The MIP / AuNPs / MWCNTs / BDD electrode is immersed into norfloxacin buffer solutions with different concentrations for 10 min, and then a differential pulse method DPV is used for testing to obtain a peak current and concentration corresponding relation curve; therefore, the selectivity of the electrode is improved, and the influence of other interfering substances is reduced. Meanwhile, the sensitivity and the stability of the electrode are enhanced, and trace substances are detected.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of an electrochemical sensor of a multi-walled carbon nanotube supported gold nanoparticle modified boron-doped diamond electrode for detecting norfloxacin in water. Background Art

[0002] As a quinolone antibiotic, norfloxacin is widely used in the fields of medicine and aquaculture. In the medical field, due to its broad-spectrum antibacterial activity, it is often used to treat various bacterial infectious diseases in humans, such as intestinal and urinary tract infections. In the aquaculture industry, norfloxacin is also widely used to prevent and treat bacterial diseases of aquatic animals to ensure aquaculture production. However, with its extensive use, norfloxacin inevitably enters the water environment. After humans use norfloxacin, part of the drug is excreted from the body in the form of the original or metabolites through urine and feces and enters the urban sewage system. If the treatment process of the sewage treatment plant cannot effectively remove norfloxacin, then it will be discharged into natural water bodies with the treated effluent. In aquaculture, norfloxacin that is not completely absorbed and utilized by aquatic organisms will remain in the aquaculture water body, and when the aquaculture wastewater is discharged, norfloxacin will also be brought into the surrounding water bodies. Norfloxacin that exists in water for a long time may have many negative impacts on the water ecosystem. It may interfere with the normal physiological functions of aquatic organisms, affect their growth, reproduction and immune capabilities, and damage the aquatic biological community structure and ecological balance. More seriously, the continuous presence of norfloxacin in the water environment may induce bacteria to develop drug resistance, which not only threatens the health of aquatic organisms, but also may pose a potential risk to human health through the food chain.

[0003] For most small water environmental pollutants including antibiotics, traditional detection methods include high performance liquid chromatography (HPLC), gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS), etc. However, these methods have both advantages and disadvantages. Their advantages lie in high sensitivity, while their disadvantages are that the instruments are expensive and large, the sample pretreatment is cumbersome, and the experimental period is long, which results in the above methods not being widely used.

[0004] Molecularly Imprinted Polymers (MIPs) are formed by the formation of host-guest complexes between template molecules (molecules to be separated) and polymerizable functional monomers through supramolecular interactions such as ionic interactions, hydrogen bonds, and hydrophobic interactions. A large amount of cross-linking agent can be added, and then it can be prepared by photo-polymerization, thermal polymerization or electro-polymerization. After removing the template molecules, cavities that precisely match the spatial structure of the template molecules are left in the polymer, and the functional groups on the cavities have specific binding ability to the template molecules. Molecularly imprinted sensors using molecularly imprinted polymers as sensitive recognition elements have the advantages of being fast, accurate, stable, and reusable, and have been widely used in analytical detection, enzyme receptor simulation, biosensors and other aspects.

[0005] An electrochemically modified electrode is a type of electrode that fixes a layer of modified substance with specific functions on the surface of a traditional electrode through physical or chemical methods, thereby endowing the electrode with new properties and functions. Summary of the Invention

[0006] Technical Problem: The purpose of the present invention is to provide a preparation method and application of an electrochemical sensor for detecting norfloxacin in water. In view of the technical requirements for detecting antibiotics in water and the existing problems in current electrochemical detection, such as poor conductivity, electrode stability, biocompatibility, and lack of specific recognition function, combined with molecular imprinting technology, polymer modification is carried out on the electrode surface to improve the selectivity of the electrode and reduce the influence of other interfering substances. At the same time, enhance the sensitivity and stability of the electrode to achieve the detection of trace substances.

[0007] Technical Solution: A preparation method of an electrochemical sensor for detecting norfloxacin in water according to the present invention uses multi-walled carbon nanotubes and gold nanoparticles to modify a boron-doped diamond BDD electrode to enhance the sensitivity of the electrode; then, using norfloxacin as an imprinting molecule, an electrochemical in-situ electropolymerization technique is used to prepare a layer of molecularly imprinted film on the surface of the boron-doped diamond BDD electrode to improve the specificity of the electrode and construct an electrochemical sensor for detecting norfloxacin in water.

[0008] The specific method of using multi-walled carbon nanotubes and gold nanoparticles to modify the boron-doped diamond BDD electrode is as follows:

[0009] The dispersed multi-walled carbon nanotubes (MWCNTs) dispersion liquid is evenly coated on the surface of the BDD electrode, and the solvent is evaporated to obtain the MWCNTs / BDD electrode; then, on an electrochemical workstation, using a three-electrode system, the MWCNTs / BDD electrode is electrochemically deposited in an aqueous solution of chloroauric acid by potentiostatic deposition to obtain the AuNPs / MWCNTs / BDD electrode.

[0010] The AuNPs / MWCNTs / BDD electrode is prepared by potentiostatic deposition electrochemically; specifically:

[0011] The well-dispersed MWCNTs dispersion was evenly coated on the surface of the BDD and placed under an infrared lamp until the solvent completely evaporated, thus obtaining the MWCNTs / BDD electrode; then, on an electrochemical workstation, using a three-electrode system, with a platinum wire electrode as the counter electrode, a saturated KCl electrode as the reference electrode, and the MWCNTs / BDD electrode as the working electrode, it was immersed in an aqueous solution of chloroauric acid and electro-deposited by potentiostatic deposition at a potential of -0.2V to obtain the AuNPs / MWCNTs / BDD electrode.

[0012] The preparation of a molecularly imprinted film on the surface of a boron-doped diamond BDD electrode by using an in-situ electrochemical polymerization technique is specifically as follows:

[0013] Taking the AuNPs / MWCNTs / BDD electrode as the working electrode, using a three-electrode system, it was immersed in a buffer solution containing norfloxacin template molecules and functional monomers for electro-polymerization, and then the template molecules were washed away to obtain the molecularly imprinted polymer modified electrode MIP / AuNPs / MWCNTs / BDD.

[0014] The functional monomer is: 4-mercaptoaniline or o-phenylenediamine.

[0015] In the buffer solution containing norfloxacin and the functional monomer, the concentration of norfloxacin is 1 mmol / L; norfloxacin:function monomer = 1:5 - 20 molar ratio.

[0016] Application of the electrochemical sensor for detecting norfloxacin in water prepared by the method of the present invention. After immersing the MIP / AuNPs / MWCNTs / BDD electrode in buffer solutions of different concentrations of norfloxacin for 10 min, it was tested by differential pulse voltammetry (DPV) to obtain a curve of the corresponding relationship between peak current and concentration.

[0017] The buffer solution is a phosphate buffer with pH = 6.86.

[0018] The concentration range of the buffer solutions of different concentrations of norfloxacin is:

[0019] Linear range: 1×10 -8 ~1×10 -5 mol / L

[0020] The lowest detection limit reaches 3.3×10 -9 mol / L.

[0021] Beneficial effects: By electrochemically polymerizing a molecularly imprinted polymer layer with molecular recognition properties on the surface of a boron-doped diamond electrode for the detection of norfloxacin in water, the selectivity of the electrode is achieved, and its conductivity is improved by modifying with carbon nanotubes and gold nanoparticles, which is beneficial for detection in low-concentration and complex systems and can greatly improve the practicality of the electrode.

[0022] The present invention combines biomimetic recognition, nanomaterials, and electrochemical detection by utilizing the specific recognition and enrichment effects of molecularly imprinted materials to prepare a molecularly imprinted polymer modified electrode for electrochemical detection, achieving specific recognition of norfloxacin molecules, improving the selectivity and sensitivity of traditional electrochemical detection techniques, and giving birth to a new detection approach with both high selectivity and high sensitivity. Description of the Drawings

[0023] Figure 1 It is the electron micrograph of the MIP / AuNPs / MWCNTs / BDD electrode.

[0024] Figure 2 It is the CV curve of norfloxacin at different concentrations.

[0025] Figure 3 It is the linear relationship diagram of peak current and logarithm of concentration.

[0026] Figure 4 It is the influence of different structural analogues on the DPV peak current. Detailed Implementation Modes

[0027] A preparation method of an electrochemical sensor for detecting norfloxacin in water according to the present invention uses multi-walled carbon nanotubes and gold nanoparticles to modify a boron-doped diamond BDD electrode to enhance the sensitivity of the electrode; then, using norfloxacin as an imprinting molecule, an electrochemical in-situ electro-polymerization technique is adopted to prepare a molecularly imprinted film on the surface of the boron-doped diamond BDD electrode to improve the specificity of the electrode, and an electrochemical sensor for detecting norfloxacin in water is constructed.

[0028] Pretreatment of Multi-walled Carbon Nanotubes

[0029] First, the MWCNTs are acidified. The steps are as follows: accurately weigh 1 g of MWCNTs, carefully pour it into a concentrated nitric acid solution, continuously ultrasonically disperse it at 65 °C for 4 h, then centrifuge to separate the MWCNTs, pour off the supernatant, wash the MWCNTs with pure water until neutral and then filter, and dry it in a drying oven at 45 °C for 24 h to obtain acidified MWCNTs. Accurately weigh 2 mg of the acidified MWCNTs and uniformly disperse it into 2 mL of N,N-dimethylformamide (DMF) solution to obtain an assembly solution of MWCNTs, and place it in a refrigerator at 4 °C for standby.

[0030] Pretreatment of the BDD Electrode

[0031] The BDD electrode was successively ultrasonically cleaned with pure water, 0.5 mol / L nitric acid solution, and acetone for 5 min, and then immersed in 0.5 mol / L sulfuric acid solution for CV scanning to make its curve stable. The scanned electrode was repeatedly rinsed with pure water and dried for standby.

[0032] Preparation of Boron-Doped Diamond Electrode Modified with Gold Nanoparticles Loaded on Multi-Walled Carbon Nanotubes

[0033] Take 10 μL of the well-dispersed 1 mg / mL MWCNTs dispersion and evenly coat it on the surface of BDD, and place it under an infrared lamp for irradiation for 20 min until the solvent is completely evaporated to obtain the MWCNTs / BDD electrode. On the electrochemical workstation, using a three-electrode system, with a platinum wire electrode as the counter electrode, a saturated KCl electrode as the reference electrode, and the MWCNTs / BDD electrode as the working electrode, immerse it in an aqueous solution of chloroauric acid with a concentration of 0.1 g / L, and electro-deposit for 2 min at a potential of -0.2 V using the potentiostatic deposition method to obtain the AuNPs / MWCNTs / BDD electrode.

[0034] Preparation of Norfloxacin Imprinted Electrode

[0035] Using an electrochemical workstation, a norfloxacin molecularly imprinted polymer electrode was prepared by electro-polymerization method. The above-prepared AuNPs / MWCNTs / BDD electrode was used as the working electrode and immersed in a phosphate buffer solution containing 1 mmol / L norfloxacin and 10 mmol / L p-mercaptoaniline. After 10 cyclic voltammetry scans at a scan rate of 50 mV / s in the potential range of -0.2 to 0.6 V, an electrode with a polymer film having the imprinting function of norfloxacin was obtained, that is, the MIP / AuNPs / MWCNTs / BDD electrode ( Figure 1 ).

[0036] Electrochemical Detection of Norfloxacin at Different Concentrations

[0037] After immersing the previously obtained MIP / AuNPs / MWCNTs / BDD electrode in norfloxacin solutions with different concentrations for 10 min, a three-electrode system was used for differential pulse voltammetry (DPV) testing ( Figure 2 ), and the buffer solution used was a phosphate buffer with pH = 6.86. The results showed that in the concentration range of 1×10 -8 ~1×10 -5 mol / L, a good linear relationship was presented between the peak current and the logarithm of the concentration ( Figure 3 ), and its linear equation was I (μA) = 47.82 + 4.178 log C (mol / L). This method has simple operation, high sensitivity, and a wide linear range.

[0038] Selectivity of the molecularly imprinted electrode

[0039] To investigate the selectivity of the sensor, several structural analogues similar to norfloxacin that might interfere with the sensor's adsorption of norfloxacin were selected: ofloxacin, ciprofloxacin, enrofloxacin, and lomefloxacin. Interfering substances with a concentration 10 times that of norfloxacin were added respectively. After soaking for 10 min, the effect of the modified electrode on the DPV peak current of norfloxacin was investigated. The results are as Figure 4 shown. The current response of norfloxacin after adding the interfering substances changed little, indicating that the sensor has good selectivity for norfloxacin.

[0040] Detection of lake water samples

[0041] The addition method was used to detect norfloxacin in lake water. During the experiment, a certain amount of lake water was taken and standard solutions of norfloxacin were added to prepare solutions with different concentrations for determination. Each determination was carried out in 3 parallel trials. The results are shown in Table 1, and the results show good recoveries, with the overall relative standard deviation less than 3.2%.

[0042] Table 1 Detection of norfloxacin in natural lake water

[0043]

Claims

1. A method for preparing an electrochemical sensor for detecting norfloxacin in water, characterized in that: Multi-walled carbon nanotubes and gold nanoparticles were used to modify the boron-doped diamond BDD electrode to enhance the sensitivity of the electrode. Then, norfloxacin was used as the imprinted molecule and electrochemical in situ electropolymerization technology was used to prepare a molecular imprinting film on the surface of the boron-doped diamond BDD electrode to improve the specificity of the electrode. An electrochemical sensor for detecting norfloxacin in water was constructed.

2. The method for preparing an electrochemical sensor for detecting norfloxacin in water according to claim 1, characterized in that: The method of modifying the boron-doped diamond (BDD) electrode using multi-walled carbon nanotubes and gold nanoparticles is specifically as follows: The dispersed multi-walled carbon nanotube MWCNTs dispersion is evenly coated on the surface of the BDD electrode, and the solvent is evaporated to obtain the MWCNTs / BDD electrode; then, on an electrochemical workstation, a three-electrode system is used to place the MWCNTs / BDD electrode in a chloroauric acid aqueous solution and electro-deposit the AuNPs / MWCNTs / BDD electrode using a constant potential deposition method.

3. The method for preparing an electrochemical sensor for detecting norfloxacin in water according to claim 2, characterized in that: The AuNPs / MWCNTs / BDD electrode is prepared by electro-deposition using a constant potential deposition method; specifically: The dispersed MWCNTs dispersion was evenly coated on the surface of BDD and irradiated under an infrared lamp until the solvent evaporated completely, thereby obtaining a MWCNTs / BDD electrode; then, on an electrochemical workstation, a three-electrode system was used, with a platinum wire electrode as the counter electrode, a saturated KCl electrode as the reference electrode, and the MWCNTs / BDD electrode as the working electrode, immersed in an aqueous solution of chloroauric acid, and electrodeposited by constant potential deposition at a potential of -0.2 V to obtain an AuNPs / MWCNTs / BDD electrode.

4. The method for preparing an electrochemical sensor for detecting norfloxacin in water according to claim 1 or 2, characterized in that: The method of preparing a molecular imprinting film on the surface of a boron-doped diamond (BDD) electrode by using an electrochemical in-situ electropolymerization technique is as follows: The AuNPs / MWCNTs / BDD electrode was used as the working electrode and immersed in a buffer solution containing the template molecule norfloxacin and a functional monomer for electropolymerization using a three-electrode system. The template molecule was then washed away to obtain a molecularly imprinted polymer modified electrode MIP / AuNPs / MWCNTs / BDD.

5. The method for preparing an electrochemical sensor for detecting norfloxacin in water according to claim 4, characterized in that: The functional monomer is: p-mercaptoaniline or o-phenylenediamine.

6. The method for preparing an electrochemical sensor for detecting norfloxacin in water according to claim 4, characterized in that: The buffer solution containing norfloxacin and the functional monomer has a norfloxacin concentration of 1 mmol / L and a molar ratio of norfloxacin to the functional monomer of 1:5-20.

7. Use of an electrochemical sensor prepared by the method according to claim 4 for detecting norfloxacin in water, characterized in that: The MIP / AuNPs / MWCNTs / BDD electrode is immersed in a norfloxacin buffer solution of different concentrations for 10 minutes, and then tested by differential pulse method DPV to obtain a peak current and concentration correspondence curve.

8. The use of the electrochemical sensor for detecting norfloxacin in water according to claim 7, characterized in that: The buffer solution is a phosphate buffer solution with a pH of 6.

86.

9. The use of the electrochemical sensor for detecting norfloxacin in water according to claim 7, characterized in that: The concentration range of the norfloxacin buffer solution of different concentrations is: Linear range: 1×10 -8 ~1×10 -5 mol / L The minimum detection limit reached 3.3×10 -9 mol / L.

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