Electrochemical sensor for detecting perfluorooctanoic acid based on molecular imprinting as well as preparation method and application of electrochemical sensor

Abstract

The invention discloses an electrochemical sensor for detecting perfluorooctanoic acid based on molecular imprinting as well as a preparation method and application of the electrochemical sensor. The electrochemical sensor is used for analyzing and detecting an acid mist inhibitor perfluorooctanoic acid (PFOA) in a pickling solution. The electrochemical sensor comprises a carbon quantum dot and a composite membrane modified glassy carbon electrode of polypyrrole and N-trifluoromethyl pyrrolidine-3-amine, wherein the composite membrane is imprinted with a PFOA structure, and the modified electrode CDs / PPy (PFPy)-MIP (PFOA) / GCE capable of selectively recognizing PFOA is prepared. The modified electrode is used as a working electrode, the PFOA in the pickling solution is detected by adopting an electrochemical alternating-current impedance technology, and the lowest detection limit reaches 0.064 mg / L. The electrochemical sensor provided by the invention does not need to carry out pretreatment such as separation on a sample, can carry out analysis and detection only by diluting the sample, and has the advantages of high selectivity, simplicity in operation and the like.

Description

Technical Field

[0001] The present invention relates to the analysis of acid mist inhibitors in the solution for rust removal of iron products in the surface treatment industry, and specifically relates to a sensor for specifically detecting perfluorooctanoic acid (PFOA) in pickling solution based on molecular imprinting electrochemical AC impedance sensor and a preparation method thereof. (PFOA) The sensor, which was composed of Ag / GCE modified electrode as working electrode, platinum electrode as auxiliary electrode and Ag / AgCl electrode as reference electrode, used electrochemical impedance spectroscopy to detect the concentration of PFOA in the pickling solution. Background Art

[0002] During the hot working (such as forging, hot rolling, etc.) of metal, a layer of oxide scale will form on the surface. This layer of oxide scale will not only affect the appearance of the metal, but also hinder the subsequent processing procedures. For example, during the cold rolling process, the oxide scale may cause the roller to wear more severely, affecting the rolling accuracy and product quality. Through pickling, this layer of oxide scale can be effectively removed, so that the metal surface can be restored to a smooth and clean state, providing a good foundation for subsequent processing. Similarly, for some mechanical parts that require high-precision surfaces, such as engine cylinders, gears, etc., pickling can remove tiny burrs, protrusions and impurities on the surface, making the surface smoother and smoother, thereby improving the assembly accuracy and operating performance of the parts, reducing friction loss, reducing noise, and improving mechanical efficiency. Therefore, pickling is an indispensable and important process in industrial production.

[0003] The main components of pickling liquid are inorganic acids, mainly hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. Different metals use different pickling liquids. The main difference is not just the different acids used, but also the different corrosion inhibitors, complexing agents, promoters and defogging agents added according to the properties of the metals. Regardless of the type of pickling liquid, defogging agents are essential, because the addition of defogging agents effectively reduces the acid mist in the environment, protects the health of operators and prevents corrosion of equipment in the surrounding environment.

[0004] The so-called defogging agent is a special amphiphilic molecular structure in the surfactant, with a hydrophilic group at one end and a hydrophobic group at the other end. The hydrophilic group can adsorb water molecules, making them evenly distributed on the surface of the pickling liquid or the metal surface, while reducing the surface tension of the water molecules. The reduction in surface tension makes it difficult for the pickling liquid to form small droplets and evaporate into the air to form acid mist, but instead spreads on the surface into a thin liquid film, thereby reducing the generation of acid mist. In addition, the surfactant also has good foaming properties and can form a thick layer of foam on the surface of the pickling liquid. These foams can cover the surface of the acid solution, prevent the acid solution from contacting the air, and thus inhibit the formation of acid mist. As mentioned above, defogging agents are mostly surfactants. Since perfluorooctanoic acid has good stability and excellent surface activity, it is often used as a defogging agent in pickling liquid. However, due to its environmental toxicity and bioaccumulation, monitoring PFOA in pickling liquid is of great significance to reducing environmental pollution and maintaining human health.

[0005] For the detection of PFOA in pickling liquid, chromatographic-mass spectrometry is often used for analysis. Due to the large number of other metal ions and organic additive molecules coexisting in the pickling liquid, the pickling liquid often needs to be separated before treatment. In view of the difficulties of the above analytical technology, the present invention has developed a modified electrode CDs / PPy(PFPy)-MIP with an extremely low detection limit (the minimum detection limit is 0.064 mg / L). (PFOA) / GCE sensor. Because the present invention does not need to perform pre-treatment such as separation on the pickling solution sample when analyzing PFOA, and other metal ions coexisting in the pickling solution do not cause interference. The modified electrode constructed by the present invention for analyzing PFOA in the pickling solution not only has the advantages of high sensitivity, strong specificity, and simple instrumentation, but more importantly, it saves the sample pre-treatment, which has important practical significance for the application of rapid analysis of PFOA. Summary of the invention

[0006] The purpose of the present invention is to provide an electrochemical sensor for detecting perfluorooctanoic acid based on molecular imprinting and a preparation method thereof, and an electrochemical impedance spectroscopy analysis method for specifically detecting PFOA in pickling liquid, in view of the fact that the analysis of PFOA in pickling liquid is relatively cumbersome and requires cumbersome operations such as pretreatment of the pickling liquid sample.

[0007] The present invention firstly provides an electrochemical AC impedance sensor for detecting PFOA based on molecular imprinting, comprising a modified electrode constructed on the surface of a conductive substrate by co-modifying carbon quantum dots and a molecular imprinting polymer imprinted with a PFOA molecular structure, wherein the molecular imprinting polymer is obtained by an electropolymerization reaction of pyrrole and N-trifluoromethylpyrrolidine-3-amine.

[0008] The electrochemical alternating current impedance sensor of the present invention is based on the fact that when pyrrole (Py) and N-trifluoromethylpyrrolidin-3-amine (FPy, CAS 1420963-61-6) are electropolymerized, the hydrophobicity of the polypyrrole (PPy) and polytrifluoropyrrole (PFPy) composite film (PPy (PFPy)) formed on the electrode is stronger than the hydrophobicity of the PPy film, thereby improving the interaction between the electropolymerized composite film (PPy (PFPy)) and the hydrophobic PFOA.

[0009] In addition, the present invention uses PFOA as the imprinting molecule. Since the pH of the electropolymerization solution is about 7.4, under this pH value, PFOA exists as an anion as a whole. Therefore, when Py and FPy are electropolymerized, PFOA is easily doped into the composite film (PPy (PFPy)) to form an electropolymerization composite film PPy (PFPy) - MIP (PFOA) / GCE. As PFOA is removed from the polymer composite film, the modified electrode PPy (PFPy) - MIP (PFOA) The spatial structure of the imprinted PFOA molecule is left in the polymer composite film of / GCE. Also due to the hydrophobicity of the imprinted PFOA molecule, the electropolymerization modified electrode PPy (PFPy) - MIP (PFOA) The hydrophobicity of the / GCE composite membrane is stronger than that of the composite membrane doped with other non-hydrophobic anions. Based on this, the modified electrode PPy (PFPy)-MIP (PFOA) The interaction between the polymer film of / GCE and PFOA binding was further strengthened.

[0010] Since the resistance of the electrodeposited polymer film is large, it seriously hinders the transmission of electrons on the electrode. In order to effectively improve the electron transmission ability of the modified composite film electrode, the present invention cleverly uses carbon quantum dots (CDs) to improve the electron transmission performance of the PPy (PFPy) composite film. The use of CDs is mainly based on the following considerations: (1) The surface of carbon quantum dots usually contains abundant oxygen-containing functional groups such as hydroxyl and carboxyl. The nitrogen atoms on the polypyrrole molecular chain have lone pairs of electrons and can form hydrogen bonds with hydroxyl and carboxyl groups on the surface of carbon quantum dots. The formation of hydrogen bonds can enhance the interaction between the two, allowing them to be better combined in the composite material, thus improving the CDs / PPy(PFPy)-MIP material. (PFOA) stability and uniformity.

[0011] (2) There are a large number of functional groups and active sites on the surface of carbon quantum dots. Polypyrrole is a conductive polymer with a conjugated structure. When the two come into contact, due to the energy level difference between carbon quantum dots and polypyrrole, electrons can be transferred from carbon quantum dots to the conjugated system of polypyrrole, or from polypyrrole to carbon quantum dots, thereby changing the electron cloud distribution and electrical properties of the two, thereby improving the modified electrode CDs / PPy(PFPy)-MIP. (PFOA) / GCE composite films.

[0012] The present invention further provides a method for preparing the electrochemical AC impedance sensor for detecting PFOA based on molecular imprinting, comprising the following specific steps: (1) A clean GCE electrode was used as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum electrode as the auxiliary electrode; electropolymerization was performed in a PBS buffer containing functional monomers Py and FPy, and a template imprinted molecule PFOA. The polymerization conditions were cyclic voltammetry scanning in the range of 0 to 0.8 V, scanning for 10 to 30 cycles, a scanning rate of 100 mV / s, and electropolymerization at room temperature. The number of scanning cycles will affect the film thickness of the modified electrode, and the optimal number of cycles is 20 cycles. After the modified electrode after electropolymerization was thoroughly washed with deionized water, it was immersed in a mixture of ethanol and DMF (v / v, 9:1), and then thoroughly washed with deionized water to obtain the modified electrode PPy(PFPy)-MIP. (PFOA) / GCE.

[0013] Wherein, in the electropolymerization solution, the molar ratio of Py, FPy and PFOA is 10:1:1; and the concentration of Py in the electropolymerization solution is 1 mmol / L.

[0014] (2) Take 2-5 μL of CDs dispersion and apply it on PPy(PFPy)-MIP (PFOA) / GCE electrode and dried at room temperature to obtain CDs / PPy(PFPy)-MIP (PFOA) / GCE modified electrode. The amount of CDs applied has a serious impact on the resistance of the modified electrode, and the optimal amount is 3μL.

[0015] Among them, CDs dispersion was prepared by preparing a mixed solution of citric acid and ethylenediamine with deionized water, placing it in a polytetrafluoroethylene-lined autoclave at 200 °C for 5 h, cooling it to room temperature after the reaction was completed, transferring the liquid in the autoclave to a dialysis membrane for dialysis in ultrapure water, centrifuging the liquid in the membrane, and freeze-drying it to obtain carbon quantum dot powder. 1 mg of CDs was taken and dispersed in 1 ml of N,N-dimethylformamide (DMF) solvent to obtain a CDs dispersion with a concentration of 1 mg / mL.

[0016] The present invention also provides the use of the electrochemical AC impedance sensor for detecting PFOA based on molecular imprinting in detecting PFOA. In a specific embodiment of the present invention, the sensor is used to detect the concentration of PFOA in the pickling solution. The detection method specifically includes: (1) Drawing of PFOA standard curve A series of solutions with different PFOA concentrations were prepared using PBS buffer solution with a pH of 7.4 and a concentration of 0.1 mol / L. (PFOA) / GCE was placed in the above solution and enriched for 10 min at room temperature under stirring conditions. The modified electrode after enrichment was washed with deionized water and used as the working electrode. Ag / AgCl was used as the reference electrode and the platinum wire electrode was used as the counter electrode to form a three-electrode system. It was placed in a solution containing Fe(CN)6 3- / 4- The AC impedance test was carried out in a 0.1 mol / L KCl solution with a concentration of 5 mmol / L. The test parameters were: potential 0.2 V, amplitude of the applied sinusoidal potential: 10 mV, frequency range: 1~1x10 5 Hz. Establishment of AC impedance sensor modified electrode CDs / PPy(PFPy)-MIP (PFOA) The relationship between the change value (ΔRct) of the charge transfer resistance (Rct) of / GCE combined with PFOA and the PFOA concentration in the standard solution was used to obtain the corresponding linear regression equation.

[0017] (2) Detection of PFOA in pickling samples The acid wash solution was diluted 1000 times with PBS buffer solution and fixed to 50 mL in a volumetric flask. The sample dilution was placed in a 100 mL beaker and the modified electrode CDs / PPy(PFPy)-MIP was placed on the (PFOA) / GCE is placed in the above sample solution and stirred for enrichment for 10 min at room temperature. The AC impedance test is performed according to the method in the above step (1), and the measured ΔRct is substituted into the regression equation of the standard curve to calculate the concentration of PFOA in the acid wash solution sample.

[0018] The electrochemical AC impedance sensor prepared by the present invention is based on the composite film CDs / PPy (PFPy)-MIP (PFOA) Strong interaction with PFOA, when modified electrode CDs / PPy(PFPy)-MIP (PFOA)When the CDs / PPy(PFPy)-MIP(PFOA) / GCD electrode meets PFOA in the solution, the modified electrode composite membrane has the spatial structure of PFOA and has similar hydrophobicity to PFOA. PFOA in the aqueous solution will be quickly enriched by the modified electrode membrane and enter the modified electrode to form a CDs / PPy(PFPy)-MIP(PFOA) / GCD electrode. At this time, the electrode is placed in a probe Fe(CN)6 3- / 4- CDs / PPy(PFPy)-MIP can be obtained in potassium chloride solution. (PFOA) Charge transfer resistance of modified electrode and its relationship with the modified electrode composite membrane CDs / PPy(PFPy)-MIP (PFOA) The more PFOA enters the composite membrane, the more CDs / PPy(PFPy)-MIP (PFOA) / GCD has a larger charge transfer resistance ( Figure 2 ). The charge transfer resistance is linearly related to the concentration of PFOA in the solution, thus realizing CDs / PPy(PFPy)-MIP (PFOA) Selective determination of PFOA using GCD / GCD modified electrode.

[0019] The significant advantage of the present invention is that a method for detecting PFOA in pickling solution has been developed. When the present invention is used to detect PFOA, only the pickling solution needs to be diluted, and no pre-separation treatment of the pickling sample is required. (PFOA) / GCE has high sensitivity. Even if the pickling solution is diluted 1000 times, PFOA in the pickling solution can still be analyzed and detected. At the same time, due to the high selectivity of the modified electrode composite membrane to PFOA, even if other metal ions and organic matter coexist in the pickling solution, they will not interfere with the determination of PFOA. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Infrared spectra of polymers: (a) PPy, (b) PPy(PFPy), and (c) PPy(PFPy)-MIP(PFOA).

[0021] Figure 2 The AC impedance response diagram is shown in Fig. 3- / 4- The concentration of PFOA was 5 mmol / L in 0.1 mol / L KCl solution. The concentrations of PFOA enriched were: 0.1 mg / L, 0.75 mg / L, 1.0 mg / L, 3.0 mg / L, 4.0 mg / L, 8.0 mg / L and 10 mg / L.

[0022] Figure 3It is the standard curve drawn according to the AC impedance response diagram. DETAILED DESCRIPTION

[0023] In order to further illustrate the effect of the technical method adopted by the present invention on detecting PFOA in the pickling solution, it is further described in detail through examples. Example

[0024] (1) Preparation of CDs dispersion Dissolve 1.05 g of citric acid monohydrate (0.5 mol / L) and 0.3 g of ethylenediamine (0.5 mol / L) in 10 mL of ultrapure water. After stirring for 10 minutes, the resulting mixed solution was transferred to a 50 mL PTFE autoclave and heated at 200 °C for 5 hours. After the reacted liquid was cooled to room temperature, the CDs solution was dialyzed in ultrapure water using a dialysis membrane. Finally, the CDs solution was centrifuged and freeze-dried to obtain a brown CDs powder. Take 1 mg of CDs and disperse it in 1 ml of N,N-dimethylformamide (DMF) solvent to obtain a dispersion of CDs with a concentration of 1 mg / mL.

[0025] (2) CDs / PPy(PFPy)-MIP (PFOA) Preparation of GCD modified electrode A clean GCE electrode (3 mm in diameter) was used as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum electrode as the auxiliary electrode. 1 mmol / L Py, 0.1 mmol / L FPy, and 0.1 mmol / L PFOA were electropolymerized in PBS buffer. The polymerization conditions were 20 cycles of cyclic voltammetry scanning in the range of 0 to 0.8 V, a scan rate of 100 mV / s, and electropolymerization at room temperature. After the modified electrode after electropolymerization was thoroughly washed with deionized water, it was immersed in a mixture of ethanol and DMF (v / v, 9:1), and then thoroughly washed with deionized water to obtain the modified electrode PPy(PFPy)-MIP. (PFOA) / GCE.

[0026] Take 3 μL of 1 mg / mL CDs dispersion and apply it dropwise on PPy(PFPy)-MIP (PFOA) / GCE electrode and dried at room temperature to obtain CDs / PPy(PFPy)-MIP (PFOA) / GCE modified electrode.

[0027] (3) Drawing of PFOA standard curve A series of solutions with PFOA concentrations of 0.1 mg / L, 0.75 mg / L, 1.0 mg / L, 3.0 mg / L, 4.0 mg / L, 8.0 mg / L and 10 mg / L were prepared using PBS buffer solution with a pH of 7.4 and a concentration of 0.1 mol / L. (PFOA) / GCE was placed in the above solution and enriched for 10 min at room temperature under stirring conditions. The modified electrode after enrichment was washed with deionized water and used as the working electrode. Ag / AgCl was used as the reference electrode and the platinum wire electrode was used as the counter electrode to form a three-electrode system. It was placed in a solution containing Fe(CN)6 3- / 4- The AC impedance test was carried out in a 0.1 mol / L KCl solution with a concentration of 5 mmol / L. The test parameters were: potential 0.2 V, amplitude of the applied sinusoidal potential: 10 mV, frequency range: 1 to 1x10 5 Hz. Establishment of modified electrode CDs / PPy(PFPy)-MIP (PFOA) The relationship between the change value (ΔRct) of the charge transfer resistance (Rct) before and after PFOA treatment and the PFOA concentration in the standard solution was obtained by combining GCE and PFOA, and the corresponding linear regression equation was: ΔRct = 1.2C + 2.27, with a linear range of 0.1 mg / L to 10 mg / L, and a correlation coefficient R 2 = 0.9960The minimum detection limit is 0.064 mg / L.

[0028] (4) Detection of PFOA in pickling samples There are many compositions of pickling liquid. In order to illustrate the effective effect of the present invention, the pickling process introduced in the literature published by Chen Jianqiu et al. is slightly modified: Development of the formula of pickling liquid for iron and steel oxide layer, Surface Technology, 2005 (34), 69-70. The composition of the pickling liquid is shown in Table 1. The concentration of the acid mist inhibitor PFOA in the pickling liquid is usually 0.2 g / L to 1.0 g / L, which is set to 1 g / L in Table 1 of the present invention.

[0029] Table 1 Composition of pickling solution

[0030] Dilute the acid wash solution in Table 1 1000 times with PBS buffer solution, accurately transfer 50 mL of the dilution solution into a 100 mL beaker, and place the modified electrode CDs / PPy(PFPy)-MIP (PFOA) / GCE was placed in the dilution solution and stirred for enrichment for 10 min at room temperature. The AC impedance test was performed according to the method in step (3) above, and the measured ΔRct was substituted into the regression equation of the standard curve to calculate the concentration of PFOA in the pickling solution sample. The results are listed in Table 2.

[0031] Figure 1 The infrared spectrum of the polymer. It can be seen from the infrared spectrum that the spectrum in the figure a is very similar to the standard spectrum of polypyrrole, proving that the synthesis of polypyrrole is very successful. After adding N-trifluoromethylpyrrole-3-amine to the pyrrole solution, as shown in b in the figure, the polymerized product shows CF vibration peaks at 1200 and 1350, indicating that N-trifluoromethylpyrrole-3-amine and pyrrole may form a copolymer. After adding perfluorooctanoic acid to the solution of pyrrole and N-trifluoromethylpyrrole-3-amine, as shown in c in the figure, the infrared spectrum of the polymerized product shows vibration peaks of carbonyl (C=O) at 1720 and hydroxyl (-OH) at 3600, indicating that perfluorooctanoic acid is doped into the copolymer of PPy (PFPy). Comparative Example

[0032] (1) Preparation of CDs dispersion Same as the embodiment.

[0033] (2) CDs / PPy-MIP (PFOA) Preparation of GCD modified electrode The most fundamental difference between the modified electrode of the comparative example and the example is that no hydrophobic polytrifluoropyrrole is added to the polypyrrole composite film, and no functional monomer Fpy is added during the synthesis and preparation of the modified electrode, and other conditions are consistent with the example.

[0034] (3) Drawing of PFOA standard curve A series of solutions with PFOA concentrations of 0.1 mg / L, 0.75 mg / L, 1.0 mg / L, 3.0 mg / L, 4.0 mg / L, 8.0 mg / L and 10 mg / L were prepared to prepare a standard curve. (PFOA) / GCE was placed in the above solution for analysis, and other operations were the same as in the example. The corresponding linear regression equation was obtained as follows: ΔRct = 1.09C +2.06, the linear range was 1.0 mg / L~10 mg / L, and the correlation coefficient R 2 = 0.9938The minimum detection limit is 0.68 mg / L.

[0035] (4) Detection of PFOA in pickling samples Since the modified electrode CDs / PPy-MIP (PFOA)The sensitivity of / GCD is low. If the sample is diluted 1000 times, the modified electrode will not be able to detect PFOA in the acid wash solution. Therefore, the acid wash solution was diluted 500 times, 50 mL of the diluted sample was taken in a 100 mL beaker, and the modified electrode CDs / PPy-MIP was placed on the (PFOA) / GCD is placed in the above sample solution for enrichment. The sample analysis operation is consistent with that in the embodiment, and the concentration of PFOA in the pickling solution sample can be calculated. The results are listed in Table 2.

[0036] Table 2 PFOA concentration in pickling solution

[0037] As shown in Table 2, the modified electrode CDs / PPy(PFPy)-MIP (PFOA) / GCE tested the pickling solution sample in parallel 3 times, and the relative standard deviation was less than 2%, and the measured value was very close to the actual addition amount, showing that the modified electrode CDs / PPy(PFPy)-MIP (PFOA) / GCE has good accuracy and precision in the analysis of PFOA in pickling liquid samples. (PFOA) When analyzing PFOA in acid washing solution by GCE, the minimum detection limit and linear range of the modified electrode were not as good as those of the modified electrode CDs / PPy(PFPy)-MIP (PFOA) / GCE, which shows the importance of hydrophobic PFPy membrane.

[0038] The above embodiments are only used to illustrate the present invention, not to limit the present invention. Those skilled in the art may make various corresponding changes without departing from the scope of the present invention. Therefore, all technical solutions formed by equivalent replacement or equivalent modification belong to the protection scope of the present invention.

Claims

1. An electrochemical sensor for detecting perfluorooctanoic acid based on molecular imprinting, characterized in that: The modified electrode comprises carbon quantum dots and molecular imprinted polymers imprinted with perfluorooctanoic acid molecular structures co-modified on the surface of a conductive substrate, wherein the molecular imprinted polymer is obtained by electropolymerization of pyrrole and N-trifluoromethylpyrrolidine-3-amine.

2. The method for preparing an electrochemical sensor for detecting perfluorooctanoic acid based on molecular imprinting according to claim 1, characterized in that: The specific steps include: (1) A PBS buffer solution containing functional monomers pyrrole and N-trifluoromethylpyrrolidine-3-amine and perfluorooctanoic acid as a template imprinting molecule is prepared as an electropolymerization solution; an electropolymerization reaction is carried out in the electropolymerization solution at room temperature using a three-electrode system to prepare a molecular imprinting polymer on the surface of a conductive substrate; the template imprinting molecule in the molecular imprinting polymer is removed to obtain an electrode of a molecular imprinting polymer imprinted with a perfluorooctanoic acid molecular structure, which is denoted as PPy(PFPy)-MIP (PFOA) / GCE; (2) Apply dispersed carbon quantum dot droplets on PPy (PFPy)-MIP (PFOA) / GCE surface, dried, and obtained the modified electrode, denoted as CDs / PPy(PFPy)-MIP (PFOA) / GCE.

3. The method for preparing an electrochemical sensor for detecting perfluorooctanoic acid based on molecular imprinting according to claim 2, characterized in that: In the electropolymerization solution, the molar ratio of pyrrole, N-trifluoromethylpyrrolidine-3-amine and perfluorooctanoic acid is 10:1:1; and the concentration of pyrrole in the electropolymerization solution is 1 mmol / L.

4. The method for preparing an electrochemical sensor for detecting perfluorooctanoic acid based on molecular imprinting according to claim 2, characterized in that: The electropolymerization reaction: using a clean GCE electrode as a working electrode, an Ag / AgCl electrode as a reference electrode, and a platinum electrode as an auxiliary electrode; The polymerization conditions are as follows: cyclic voltammetry scanning in the range of 0 to 0.8 V at room temperature, scanning for 10 to 30 cycles, and a scanning rate of 100 mV / s.

5. The method for preparing an electrochemical sensor for detecting perfluorooctanoic acid based on molecular imprinting according to claim 2, characterized in that: The carbon quantum dot dispersion is obtained by uniformly dispersing the carbon quantum dots in N,N-dimethylformamide solvent, and the concentration is 1 mg / mL; the drop coating amount is 2 to 5 μL.

6. Use of the electrochemical sensor for detecting perfluorooctanoic acid based on molecular imprinting as claimed in claim 1 in detecting the concentration of perfluorooctanoic acid by electrochemical impedance spectroscopy.

7. The use according to claim 6, characterized in that: The detection method comprises the following steps: (1) Prepare PBS buffer solutions containing different concentrations of perfluorooctanoic acid as standard solutions and place the modified electrode CDs / PPy(PFPy)-MIP (PFOA) / GCE was placed in a standard solution and enriched for 10 min at room temperature under stirring. The modified electrode after enrichment was used as the working electrode, Ag / AgCl was used as the reference electrode, and a platinum wire electrode was used as the counter electrode to form a three-electrode system. 3- / 4- AC impedance test was carried out in KCl solution; AC impedance sensor modified electrode CDs / PPy(PFPy)-MIP was established (PFOA) The relationship curve between the change value of charge transfer resistance (ΔRct) of / GCE combined with perfluorooctanoic acid and the concentration of PFOA in the standard solution was obtained, and the corresponding linear regression equation was obtained; (2) Modified electrode CDs / PPy(PFPy)-MIP (PFOA) / GCE is placed in the diluent of the pickling solution and stirred for enrichment for 10 min at room temperature. The AC impedance test is performed according to the method in the above step (1). The measured ΔRct is substituted into the linear regression equation of the standard curve to calculate the concentration of perfluorooctanoic acid in the pickling solution.

8. The use according to claim 7, characterized in that: The Fe(CN)6 3- / 4- In KCl solution, Fe(CN)6 3- / 4- The concentration of is 5 mmol / L, and the concentration of KCl is 0.1 mol / L.

9. The use according to claim 7, characterized in that: The parameters of the AC impedance test are: potential 0.2 V, amplitude of the applied sinusoidal potential: 10 mV, frequency range: 1 to 1×10 5 Hz.

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