Perfluorinated compound electrochemical sensor based on two-parameter molecular imprinting composite coating and preparation method

Abstract

The invention belongs to the technical field of electrochemical sensors, and relates to a perfluorinated compound electrochemical sensor based on a two-parameter molecular imprinting composite coating as well as a preparation method and application of the perfluorinated compound electrochemical sensor. The perfluorinated compound electrochemical sensor comprises a PFOA molecular imprinting sensing area, a PFOS molecular imprinting sensing area, a glass substrate, a circuit board, an external electrode and the like. [Fe (CN) 6] < 3- / 4-> is taken as a probe molecule, the hole effect on a molecularly imprinted membrane is utilized, that is, a target molecule can be adsorbed to a binding site through electrostatic attraction or hydrogen-bond interaction, after the originally exposed binding site is occupied by the target molecule, the surface conductivity of an electrode is inhibited, a relatively low signal response is generated, and the detection sensitivity is improved. And the concentrations of PFOA and PFOS are quantified according to the change of a current signal generated on the surface of the working electrode. The electrochemical sensor disclosed by the invention is successfully applied to detection of PFOA and PFOS in a water sample, has the advantages of rapid response, high sensitivity, strong specificity, good stability and good anti-interference performance, and can realize simultaneous detection of double targets (PFOA and PFOS) and in-situ cleaning of the electrode in one set of sensor; the volume of the needed sample is obviously reduced, tedious and repeated manual operation is reduced, the cost is low, carrying is easy, the requirement for on-site rapid detection of the actual sample can be met, and marketization is more convenient.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical sensor technology, and relates to electrochemical sensing technology based on molecularly imprinted polymers. Specifically, it relates to a perfluorinated compound electrochemical sensor based on a dual-parameter molecularly imprinted composite coating, its preparation method, and its application. Background Technology

[0002] According to records, perfluorinated compounds (PFAS) are a class of synthetically produced organofluorine compounds. Due to their stable physical and chemical properties, as well as their hydrophobic and oleophobic properties, they are widely used in commercial and industrial applications, such as aqueous film-forming foams for firefighting, lubricants, pesticides, textiles, and food packaging. PFAS can be classified according to the differences in their terminal groups into perfluoroalkyl acids (PFAAs) and perfluoroalkyl carboxylic acids / perfluoroalkyl carboxylic acids (PFCAs), among which perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are typical representatives of PFAAs and PFCAs, respectively. However, the CF bond has strong polarity, enabling it to withstand strong heating, light, chemical reactions, microbial activity, and the metabolism of higher vertebrates. This makes PFAS persistent and difficult to degrade in the natural environment. As research has progressed, PFAS have been detected in environmental media such as soil and water. In addition, toxicological studies have found that they have the ability to bind to proteins and accumulate in the body. PFAS are eventually exposed to human body fluids and tissues such as serum, breast milk, liver and kidneys through drinking water and the food chain, thereby producing hepatotoxicity, immunotoxicity, reproductive and developmental toxicity, endocrine disruption and potential carcinogenicity.

[0003] Currently, the main method for PFAS detection is the traditional analytical method based on chromatography-mass spectrometry (GC-MS). While this method offers high sensitivity, it often requires transporting collected samples to a laboratory for multi-step pretreatment, resulting in a long detection cycle. Furthermore, the instruments used are sophisticated and expensive, requiring specialized technicians for maintenance and operation, leading to high detection costs and lacking on-site testing capabilities. Therefore, to improve detection efficiency, reduce costs, and achieve rapid screening of batches of samples, it is essential to establish a simpler, faster, and more cost-effective method for PFAS detection.

[0004] Electrochemical sensing enables rapid detection of target substances based on changes in electrochemical signals induced by their presence. Traditional electrochemical sensing methods rely on the redox reaction properties of the target substance itself to generate a detectable electrical signal. However, PFAS (perfluorooctanoic acid) are electrochemically inert substances and cannot be directly detected. Therefore, researchers combine molecular imprinting technology with electrochemical sensing to achieve rapid PFAS sensing. Molecular imprinting (MIPs), as a specific molecular recognition technology, is often used for targeted synthesis to achieve targeted recognition of target molecules. Due to its advantages such as ease of operation, high stability, and ease of on-site analysis, it has promising application prospects and broad development potential in fields such as food and environmental safety assessment. Chinese patent CN 118533933 A provides an anti-interference electrochemical molecular imprinted sensor for perfluorooctanoic acid (PFOA) and its application in detecting PFOA in water. This method has the advantages of rapid response, high sensitivity, strong specificity, good stability, and good anti-interference. However, implementing the method described in this patent still requires a dedicated electrochemical workstation, which is inconvenient to operate and requires a large sample volume for measurement. Furthermore, it cannot simultaneously detect multiple target substances.

[0005] Based on the current state of the technology, the inventors of this application intend to provide an electrochemical sensing technology based on molecularly imprinted polymers, especially a perfluorinated compound electrochemical sensor based on a two-parameter molecularly imprinted composite coating, its preparation method and application. Summary of the Invention

[0006] The purpose of this invention is to provide an electrochemical sensing technology based on molecularly imprinted polymers, and in particular, a perfluorinated compound electrochemical sensor based on a two-parameter molecularly imprinted composite coating, its preparation method, and its application, based on the current state of the prior art and addressing the problems existing in the prior art.

[0007] This invention can simultaneously detect two PFAS (PFOA and PFOS). The reaction cell can achieve in-situ cleaning and in-situ measurement. It has the advantages of small sample volume, high detection sensitivity, strong specificity, good repeatability and convenient operation.

[0008] To achieve the above objectives, the present invention adopts the following solution:

[0009] An electrochemical sensor for perfluorinated compounds based on a dual-parameter molecularly imprinted composite coating is provided, characterized by comprising a PFOA molecularly imprinted sensing region, a PFOS molecularly imprinted sensing region, a glass substrate, a circuit board, and external electrodes.

[0010] The PFOA molecular imprinted sensing area and the PFOS molecular imprinted sensing area are fixed on the upper surface of the glass substrate, located on the left and right sides respectively, and are used to detect PFOA and PFOS molecules.

[0011] Furthermore, the PFOA molecularly imprinted sensing region and the PFOS molecularly imprinted sensing region are two independent electrochemical sensing systems, each including a working electrode, a reference electrode, and a counter electrode. These three electrodes are arranged concentrically on a glass substrate and are electrically insulated from each other. The working electrode is located at the very center of the sensing region, the non-enclosed annular reference electrode is located around the working electrode, and the non-enclosed annular counter electrode is located around the reference electrode. The counter electrodes of the two sensing regions are independent of each other. Above the counter electrode, a closed convex wall is provided around the sensing region, forming an open electrochemical reaction cell. The inner diameter of the cell wall is larger than the arc-shaped inner diameter of the counter electrode, enclosing the working electrode, counter electrode, and reference electrode within it. The circuit board is fixed below the glass substrate, and multiple external electrodes are provided on the circuit board, connected to the working electrode, counter electrode, and reference electrode in the two sensing regions respectively via gold wires.

[0012] This invention provides a method for preparing a perfluorinated compound electrochemical sensor based on a dual-parameter molecularly imprinted composite coating, which includes three parts: electrode construction, in-situ polymerization of the imprinted membrane, and in-situ elution of the imprinted membrane.

[0013] The method for preparing a perfluorinated compound electrochemical sensor with a dual-parameter molecularly imprinted composite coating as described in this invention includes the following steps in electrode construction:

[0014] (1) A layer of photoresist is spin-coated on the upper surface of the glass substrate, with a thickness greater than three times that of the conductive film to be sputtered; after photolithography and development, the patterns of working electrode, reference electrode and counter electrode are formed.

[0015] (2) A conductive film is sputtered on the surface of the photoresist working electrode pattern, and a silver / silver chloride film and a platinum film are sputtered on the surfaces of the reference electrode and the counter electrode, respectively, with a thickness of about 350 nm.

[0016] (3) Use a stripping process to remove excess conductive film layers, leaving the required working electrode, reference electrode and counter electrode;

[0017] (4) Cover the insulating substrate surface of the prepared conductive thin film layer with a silicon oxide insulating layer, and then expose the required working electrode, reference electrode and counter electrode by ion beam etching, while retaining the insulating layer covering the surface of other areas.

[0018] (5) Fix the electrode substrate constructed above onto the upper surface of the circuit board, and then use gold wire ball soldering to connect the working electrode, counter electrode and reference electrode in the sensing area to the external electrode on the circuit board.

[0019] (6) On the surface of the insulating layer, a three-dimensional ring with a height of about 25 μm is cast around the working electrode, the reference electrode and the counter electrode to form an electrochemical reaction cell, while all gold wires and the edge of the sensing area are sealed inside the ring wall.

[0020] The method for preparing a perfluorinated compound electrochemical sensor with a dual-parameter molecularly imprinted composite coating according to the present invention includes the following steps in the in-situ polymerization of the imprinted film:

[0021] (1) Using a physical drop-coating method, a carboxymethyl cellulose-multi-walled carbon nanotube (CMC-MWCNTs) suspension was coated onto the surfaces of two working electrodes. The modified working electrodes obtained under natural drying have the advantages of large specific surface area, strong conductivity and good stability.

[0022] (2) For the PFOA molecularly imprinted membrane, take 0.2-1.0 mg PFOA, 30-110.0 μL methacrylic acid, 0.5-1.5 mL ethylene glycol dimethacrylate, and 2-8 mg azobisisobutyronitrile, and add them to 0.2-1.5 mL of dimethyl sulfoxide solution; then inject the electropolymerization solution prepared above into the electrochemical reaction cell and dry it at 40 °C; connect the working electrode, counter electrode, and reference electrode of the sensing area to the corresponding external electrochemical workstation, and then use cyclic voltammetry at 60-120 °C.

[0023] The scanning rate was between mV / s, with 15-30 scan cycles, to generate an imprinted polymer film with PFOA as the template molecule.

[0024] (3) For PFOS molecular imprinted membrane, take 0.2-1.0 mg PFOS and 1-10 mg o-phenylenediamine and dissolve them in 0.1 mol / L acetate buffer (pH 4.0); then take the above-prepared electropolymerization solution and inject it into the electrochemical reaction cell. Connect the working electrode, counter electrode, and reference electrode of the sensing area to the external electrochemical workstation. Then use cyclic voltammetry to scan at a rate of 60-120 mV / s, with 15-30 scan cycles, to generate an imprinted polymerized membrane with PFOS as the template molecule.

[0025] The method for preparing a perfluorinated compound electrochemical sensor with a dual-parameter molecularly imprinted composite coating according to the present invention, wherein the imprinted film is eluted in situ, includes the following steps:

[0026] (1) For eluting PFOA molecules, add elution solution (methanol:acetic acid = 9:1, v / v) to the electrochemical reaction cell and soak for 1-30 min to remove PFOA; then add ultrapure water dropwise to the eluted electrode to remove acetic acid and PFOA adhering to the electrode, and then dry at room temperature for later use.

[0027] (2) To remove PFOS molecules, add elution solution (0.1 mol / L NaOH solution) to the electrochemical reaction cell and soak for 1-30 min to remove PFOS; then add ultrapure water dropwise to the eluted electrode to remove NaOH and PFOS adhering to the electrode; then dry at room temperature for later use.

[0028] The application of the perfluorinated compound electrochemical sensor with the dual-parameter molecularly imprinted composite coating described in this invention includes the following steps:

[0029] (1) Injecting a solution containing 2.00 into the electrochemical reaction cell

[0030] mmol / L [Fe(CN)6] 3- / 4- The peak current signal against the blank background was recorded using a 0.10 mol / L KCl test solution and differential pulse voltammetry. The scan range was 0-0.40 V, the rest time was 2.00 s, the voltage amplitude was 0.05 V, the pulse period was 0.5 s, the sampling width was 0.0167 s, and the scan speed was 100 mV / s.

[0031] (2) After cleaning the electrode with ultrapure water, inject the test base solution containing different concentrations of PFOA and PFOS into the left and right electrochemical reaction cells and incubate for 1-10 min respectively. Based on the above conditions, scan to obtain the corresponding peak current signal.

[0032] (3) Calculate the difference between the peak current signal and the blank background signal at different concentrations, and then fit the linear relationship between the peak current signal and the concentration of the target molecule.

[0033] (4) Further, actual samples (such as food, soil, environmental water samples, etc.) are collected, pretreated, mixed with the above-mentioned test base liquid, and then the differential pulse voltammetry test is performed in the same procedure. The difference between the peak current signals before and after the target molecules are incubated is calculated to quantify PFOA and PFOS in the water environment.

[0034] The perfluorinated compound electrochemical sensor based on a dual-parameter molecularly imprinted composite coating of the present invention has been put into practical use. The following steps are followed for its operation:

[0035] (1) Injecting a solution containing 2.00 mmol / L [Fe(CN)6] into an electrochemical reaction cell 3- / 4- The peak current signal against the blank background was recorded using a 0.10 mol / L KCl test solution and differential pulse voltammetry. The scan range was 0-0.40 V, the rest time was 2.00 s, the voltage amplitude was 0.05 V, the pulse period was 0.5 s, the sampling width was 0.0167 s, and the scan speed was 100 mV / s.

[0036] (2) After cleaning the electrode with ultrapure water, inject the test base solution containing different concentrations of PFOA and PFOS into the left and right electrochemical reaction cells and incubate for 1-10 min respectively. Based on the above conditions, scan to obtain the corresponding peak current signal.

[0037] (3) Calculate the difference between the peak current signal and the blank background signal at different concentrations, and then fit the linear relationship between the peak current signal and the concentration of the target molecule.

[0038] (4) Further, collect actual samples, such as food, soil, and environmental water samples, and after pretreatment, mix them with the above-mentioned test base liquid. Then, perform differential pulse voltammetry testing using the same procedure. Quantify PFOA and PFOS in the water environment by calculating the difference in peak current signals before and after incubation of the target molecules.

[0039] The electrochemical sensor prepared in this invention is based on [Fe(CN)6]. 3- / 4- As a probe molecule, after all the template molecules on the polymer membrane are eluted, a large number of specific binding sites are exposed, allowing [Fe(CN)6] to bind. 3- / 4- These sites can reach the electrode surface and generate a reduction current, at which point the current reaches its maximum value. When the target substance is present, the target molecule is adsorbed onto the binding site through electrostatic attraction or hydrogen bonding. The reduction of holes leads to the inhibition of conductivity on the electrode surface, resulting in a lower signal response. As the concentration of the target substance gradually increases, the difference between its peak current signal and the blank signal also gradually increases. The changes in the probe current signal before and after incubation of the target molecule are used to quantitatively analyze the concentrations of PFOA and PFOS in the water sample.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] (1) The present invention constructs a simple and portable electrochemical sensing device, which has the advantages of being fast, simple, low cost and easy to carry compared with the method of large instruments, and is more convenient for commercialization.

[0042] (2) Compared with existing electrochemical methods for detecting PFAS, the solution provided by this invention can realize the simultaneous detection of dual targets (PFOA and PFOS) and in-situ cleaning of electrodes in one sensor, significantly reducing the required sample volume and reducing tedious and repetitive manual operations, thus meeting the needs of rapid on-site detection of actual samples.

[0043] (3) Compared with a single conductive film, the present invention uses multi-walled carbon nanotubes with a large specific surface area and carboxymethyl cellulose with strong dispersibility to modify the conductive film, which significantly enhances the electron transfer efficiency of probe molecules on the electrode surface, making the working electrode more conductive and greatly improving the sensitivity of the detection method.

[0044] (4) In this invention, PFOA and PFOS are used as template molecules and in-situ polymerization is used to construct molecularly imprinted membranes of PFOA and PFOS respectively. These membranes can capture target molecules in a targeted manner through adsorption of specific recognition sites and high affinity, with high detection selectivity and effective resistance to interference from other PFAS with similar structures. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a perfluorinated compound electrochemical sensor based on a two-parameter molecularly imprinted composite coating.

[0046] Figure 2 for Figure 1 AA section view in the image.

[0047] Figure 3 This is a schematic diagram illustrating the principle of detecting PFOA and PFOS based on the present invention.

[0048] Figure 4 The differential pulse voltammograms and standard working curves of PFOA in different concentration ranges constructed based on the examples are shown.

[0049] Figure 5 The differential pulse voltammograms and standard working curves of PFOS in different concentration ranges constructed based on the examples are shown.

[0050] Figure 6 This demonstrates the anti-interference capability of the electrochemical sensor constructed based on the embodiments. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Example 1

[0053] Fabrication of a perfluorinated compound electrochemical sensor based on a two-parameter molecularly imprinted composite coating, such as... Figure 1 and 2 As shown, the perfluorinated compound electrochemical sensor includes a PFOA molecularly imprinted sensing region 1, a PFOS molecularly imprinted sensing region 2, a glass substrate 3, a circuit board 4, and an external electrode 5.

[0054] The PFOA molecular imprinted sensing region 1 and the PFOS molecular imprinted sensing region 2 are fixed on the upper surface of the glass substrate 3, located on the left and right sides respectively, and are used to detect PFOA and PFOS molecules.

[0055] The PFOA molecularly imprinted sensing region 1 and PFOS molecularly imprinted sensing region 2 are two independent electrochemical sensing systems, each including a working electrode 6, a reference electrode 7, and a counter electrode 8. These three electrodes are arranged concentrically on the glass substrate 3 and are electrically insulated from each other. The working electrode 6 is located at the very center of the sensing region, the non-enclosed annular reference electrode 7 is located around the working electrode 6, and the non-enclosed annular counter electrode 8 is located around the reference electrode 7. The counter electrodes of the two sensing regions 1 and 2 are independent of each other. Above the counter electrode 8, a closed convex wall 9 is provided around the sensing region, forming an open electrochemical reaction cell 10. The inner diameter of the cell wall is larger than the arc-shaped inner diameter of the counter electrode 8, enclosing the working electrode 6, counter electrode 8, and reference electrode 7 within it. The circuit board 4 is fixed below the glass substrate 3, and multiple external electrodes 5 are provided on the circuit board, connected to the working electrode 6, counter electrode 8, and reference electrode 7 in the two sensing regions via gold wires 11.

[0056] This embodiment describes the preparation of a perfluorinated compound electrochemical sensor based on a dual-parameter molecularly imprinted composite coating using the following method, which includes three parts: electrode construction, in-situ polymerization of the imprinted film, and in-situ elution of the imprinted film; wherein...

[0057] The implementation steps for constructing the electrode are as follows:

[0058] (1) A layer of photoresist is spin-coated on the upper surface of the glass substrate 3, with a thickness greater than three times that of the conductive film to be sputtered; after photolithography and development, a pattern of working electrode 6, reference electrode 7 and counter electrode 8 is formed.

[0059] (2) A conductive film 12 is sputtered on the surface of the photoresist working electrode pattern, and a silver / silver chloride film 13 and a platinum film 14 are sputtered on the surfaces of the reference electrode 7 and the counter electrode 8, respectively, with a thickness of approximately 350 nm.

[0060] (3) Use a stripping process to remove excess conductive film layer, leaving the required working electrode 6, reference electrode 7 and counter electrode 8;

[0061] (4) Cover the insulating substrate surface with silicon oxide insulating layer 15 after the conductive thin film layer is prepared, and then expose the required working electrode 6, reference electrode 7 and counter electrode 8 by ion beam etching, while retaining the insulating layer 15 covering the surface of other areas.

[0062] (5) Fix the electrode substrate constructed above onto the upper surface of the circuit board 4, and then use gold wire ball soldering to connect the working electrode 6, counter electrode 8 and reference electrode 7 in the sensing area to the external electrode 5 on the circuit board 4.

[0063] (6) On the surface of the insulating layer 15, a three-dimensional ring 9 with a height of about 25 μm is cast around the working electrode 6, the reference electrode 7, and the counter electrode 8 to form an electrochemical reaction cell 10, while all gold wires 11 and the edge of the sensing area are sealed inside the ring wall 9.

[0064] The implementation method of the in-situ polymerization of the imprinted film is described in the following specific embodiments:

[0065] (1) Using a physical drop-coating method, 15 μL of carboxymethyl cellulose-multi-walled carbon nanotubes (CMC-MWCNTs) suspension was coated onto the surfaces of two working electrodes. The modified working electrodes obtained under natural drying conditions have the advantages of large specific surface area, strong conductivity, and good stability.

[0066] (2) For the PFOA molecular imprinted membrane 16, take 0.5 mg PFOA, 90 μL methacrylic acid, 1.3 mL ethylene glycol dimethacrylate and 4.5 mg azobisisobutyronitrile, and add them to 0.5 mL of dimethyl sulfoxide solution; then take the above-prepared electropolymerization solution and inject it into the electrochemical reaction cell 10, and dry it at 40 °C; connect the working electrode 6, counter electrode 8 and reference electrode 7 of the sensing area to the external electrochemical workstation, and then use cyclic voltammetry to scan between them at a rate of 100 mV / s, with a scanning cycle of 30, to generate the imprinted polymer membrane 16 with PFOA as the template molecule;

[0067] (3) For the PFOS molecular imprinted membrane 17, 0.5 mg of PFOS and 3 mg of o-phenylenediamine were dissolved in 0.1 mol / L acetate buffer (pH 4.0); then the prepared electropolymerization solution was injected into the electrochemical reaction cell 10, and the working electrode 6, counter electrode 8, and reference electrode 7 of the sensing area were connected to the external electrochemical workstation. Cyclic voltammetry was then used to scan the area at a rate of 100 mV / s, with 15 scan cycles, to generate the imprinted polymer membrane 17 with PFOS as the template molecule.

[0068] Furthermore, the in-situ elution steps of the imprinted membrane are as follows:

[0069] (1) To remove PFOA molecules, add elution solution (methanol:acetic acid = 9:1, v / v) to electrochemical reaction cell 10 and soak for 15 min to remove PFOA; then add ultrapure water dropwise to the working electrode 6 after elution to remove acetic acid and PFOA attached to the electrode, and then dry at room temperature for later use.

[0070] (2) To remove PFOS molecules, add elution solution (0.1 mol / L NaOH solution) to electrochemical reaction cell 10 and soak for 5 min to remove PFOS; then add ultrapure water dropwise to the working electrode 6 after elution to remove NaOH and PFOS adhering to the electrode; then dry at room temperature for later use.

[0071] Based on the above preparation parameters, this invention provides a detailed explanation of the application of a rapid detection method for PFOA and PFOS using collected surface water as an example. The specific steps are as follows:

[0072] First, a solution containing 2.00 mmol / L [Fe(CN)6] was injected into the electrochemical reaction cell. 3- / 4- Using a 0.10 mol / L KCl test base solution, the peak current signal against the blank background was recorded by differential pulse voltammetry. The scan range was 0 V-0.40 V, the rest time was 2.00 s, the voltage amplitude was 0.05 V, the pulse period was 0.5 s, the sampling width was 0.0167 s, and the scan speed was 100 mV / s.

[0073] After rinsing the electrodes with ultrapure water, PFOA standard solutions with a concentration range of 0.1-2000 ng / mL were sequentially injected into the left electrochemical reaction cell 10 and incubated for 5 min; then PFOS standard solutions with a concentration range of 5-1200 ng / mL were sequentially injected into the right electrochemical reaction cell 10 and incubated for 1 min; based on the above conditions, a scan was performed to obtain the corresponding peak current signal.

[0074] like Figure 4 and 5 As shown, the peak current gradually decreases with increasing PFOA concentration, indicating that more PFOA molecules bind to the imprinted membrane through the imprinted pores, occupying holes on the membrane and blocking [Fe(CN)6]. 3- / 4- Electron exchange of the probe. Within the PFOA concentration range of 0.1-2000 ng / mL, the Ip value and the logarithm of the PFOA concentration showed a good linear relationship. The correlation coefficient was 0.98384, and the linear regression equation can be expressed as Ip(μA) = -0.01167C. PFOA +75.31125, the detection limit (S / N = 3) is 0.1287 ng / mL. Similarly, in the range of 5-1200 ng / mL, the peak current difference is linearly related to the PFOS concentration, with regression equations of Ip(μA) = -0.019C. PFOS +69.53869(R 2 =0.9729); the detection limit in the low concentration range (S / N=3) is as low as 1.75 ng / mL, indicating that the method has high sensitivity.

[0075] Furthermore, 20 mL of local environmental water sample was collected, filtered through a 0.22 μm microporous membrane, mixed with the aforementioned test solution, and then subjected to differential pulse voltammetry testing using the same procedure. The results showed that PFOA and PFOS were not directly detected in the environmental water sample. To evaluate the practical application performance of the constructed sensor, this invention employs a standard spiking method to further demonstrate the feasibility of the detection method. PFOA and PFOS standard solutions of 10 ng / mL and 30 ng / mL were added to the collected water sample, respectively, and differential pulse voltammetry testing was performed according to the above steps. The PFOA concentrations in the spiked test samples were 10.17 ng / mL and 31.25 ng / mL, respectively; the PFOS concentrations were 9.94 ng / mL and 30.69 ng / mL, respectively. The calculated recoveries were 101.70%, 104.17%, 99.40%, and 102.30%, respectively, and the RSD values ​​were all below 5%, indicating that the quantitative analysis using this method is accurate and reliable.

[0076] Specificity verification based on the above embodiments:

[0077] Perfluorodecanoic acid (PFDA), perfluorovalerate (PFPeA), and perfluorooctane (PFO) at 10 times concentration were selected as interfering substances. These three substances are structural analogs of PFOA and PFOS. The test procedure is as described in the examples, and the results are as follows. Figure 6 As shown, after the interfering substances are added to the detection system, the peak current only changes significantly when PFOA or PFOS are present alone, and their respective electrochemical signals do not interfere with each other; while the current changes of PFDA, PFPeA, and PFO are very small and almost negligible, indicating that the sensor has good specificity.

[0078] Traditional instrumental analysis methods (such as liquid chromatography-mass spectrometry) can accurately perform quantitative and qualitative analysis, but these methods require expensive equipment, cumbersome pretreatment processes, and high sample purity requirements, resulting in high detection costs and long cycles, which cannot meet the requirements of large-scale rapid screening and thus limit their widespread use. This invention, as a novel detection and analysis technology, utilizes electrochemical sensing technology based on molecularly imprinted membranes, which has advantages such as high specificity, high sensitivity, and good stability. Moreover, this method is simple to operate, has a rapid response, and integrates the previously complex detection system into a single sensor, enabling in-situ detection and cleaning, providing practical evidence for the subsequent fabrication of more integrated sensors.

[0079] The above embodiments are merely explanations of the present invention, but the implementation of the present invention is not limited to the embodiments described. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A perfluorinated compound electrochemical sensor based on a dual-parameter molecularly imprinted composite coating, characterized in that, It includes a PFOA molecular imprinted sensing region, a PFOS molecular imprinted sensing region, a glass substrate, a circuit board, and an external electrode structure. The PFOA molecular imprinted sensing area and the PFOS molecular imprinted sensing area are fixed on the upper surface of the glass substrate and are located on the left and right sides respectively, for detecting PFOA and PFOS molecules. The PFOA molecularly imprinted sensing region and the PFOS molecularly imprinted sensing region are two independent electrochemical sensing systems, each including a working electrode, a reference electrode, and a counter electrode. The three electrodes are arranged concentrically on a glass substrate and are electrically insulated from each other. The working electrode is located at the center of the sensing region, the non-closed annular reference electrode is located on the outer ring of the working electrode, and the non-closed annular counter electrode is located on the outer ring of the reference electrode. The counter electrodes of the two sensing regions are independent of each other. Above the counter electrode, a closed convex wall is provided around the sensing region to form an open electrochemical reaction cell. The inner diameter of the cell wall is larger than the arc-shaped inner diameter of the counter electrode, enclosing the working electrode, counter electrode, and reference electrode within it. The circuit board is fixed below the glass substrate, and multiple external electrodes are provided on the circuit board, which are connected to the working electrode, counter electrode and reference electrode in the two sensing areas respectively via gold wires.

2. The method for preparing the perfluorinated compound electrochemical sensor based on a dual-parameter molecularly imprinted composite coating as described in claim 1, characterized in that, The preparation process includes three parts: electrode construction, in-situ polymerization of the imprinted membrane, and in-situ elution of the imprinted membrane.

3. The preparation method according to claim 2, characterized in that, The electrode is constructed according to the following steps: (1) A layer of photoresist is spin-coated on the upper surface of the glass substrate, with a thickness greater than three times that of the conductive film to be sputtered; after photolithography and development, the patterns of working electrode, reference electrode and counter electrode are formed. (2) A conductive film is sputtered on the surface of the photoresist working electrode pattern, and a silver / silver chloride film and a platinum film are sputtered on the surfaces of the reference electrode and the counter electrode, respectively, with a thickness of about 350 nm. (3) Use a stripping process to remove excess conductive film layers, leaving the required working electrode, reference electrode and counter electrode; (4) Cover the insulating substrate surface of the prepared conductive thin film layer with a silicon oxide insulating layer, and then expose the required working electrode, reference electrode and counter electrode by ion beam etching, while retaining the insulating layer covering the surface of other areas. (5) Fix the electrode substrate constructed above onto the upper surface of the circuit board, and then use gold wire ball soldering to connect the working electrode, counter electrode and reference electrode in the sensing area to the external electrode on the circuit board. (6) On the surface of the insulating layer, a three-dimensional ring with a height of about 25 μm is cast around the working electrode, the reference electrode and the counter electrode to form an electrochemical reaction cell, while all gold wires and the edge of the sensing area are sealed inside the ring wall.

4. The preparation method according to claim 2, characterized in that, The in-situ polymerization of the imprinted film is carried out according to the following steps: (1) Using a physical drop-coating method, a carboxymethyl cellulose-multi-walled carbon nanotube (CMC-MWCNTs) suspension was coated onto the surfaces of two working electrodes. The modified working electrodes obtained under natural drying have the advantages of large specific surface area, strong conductivity and good stability. (2) For PFOA molecularly imprinted membrane, take 0.2-1.0 mg PFOA, 30-110.0 μL methacrylic acid, 0.5-1.5 mL ethylene glycol dimethacrylate and 2-8 mg azobisisobutyronitrile, and add them to 0.2-1.5 mL of dimethyl sulfoxide solution; then inject the electropolymerization solution prepared above into the electrochemical reaction cell and dry it at 40 °C; connect the working electrode, counter electrode and reference electrode of the sensing area to the external electrochemical workstation, and then use cyclic voltammetry to scan between 60-120 mV / s, with a scanning cycle of 15-30, to generate an imprinted polymerized membrane with PFOA as the template molecule; (3) For PFOS molecular imprinted membrane, take 0.2-1.0 mg PFOS and 1-10 mg o-phenylenediamine and dissolve them in 0.1 mol / L acetate buffer (pH 4.0); then take the above-prepared electropolymerization solution and inject it into the electrochemical reaction cell. Connect the working electrode, counter electrode, and reference electrode of the sensing area to the external electrochemical workstation. Then use cyclic voltammetry to scan at a rate of 60-120 mV / s, with 15-30 scan cycles, to generate an imprinted polymerized membrane with PFOS as the template molecule.

5. The preparation method according to claim 2, characterized in that, The in-situ elution of the imprint membrane is performed according to the following steps: (1) For eluting PFOA molecules, add elution solution (methanol:acetic acid = 9:1, v / v) to the electrochemical reaction cell and soak for 1-30 min to remove PFOA; then add ultrapure water dropwise to the eluted electrode to remove acetic acid and PFOA adhering to the electrode, and then dry at room temperature for later use. (2) To remove PFOS molecules, add elution solution (0.1 mol / L NaOH solution) to the electrochemical reaction cell and soak for 1-30 min to remove PFOS; then add ultrapure water dropwise to the eluted electrode to remove NaOH and PFOS adhering to the electrode; then dry at room temperature for later use.

6. The perfluorinated compound electrochemical sensor based on a dual-parameter molecularly imprinted composite coating according to claim 1, characterized in that, It is used by following these steps: (1) Injecting a solution containing 2.00 mmol / L [Fe(CN)6] into an electrochemical reaction cell 3- / 4- The peak current signal against the blank background was recorded using a 0.10 mol / L KCl test solution and differential pulse voltammetry. The scan range was 0-0.40 V, the rest time was 2.00 s, the voltage amplitude was 0.05 V, the pulse period was 0.5 s, the sampling width was 0.0167 s, and the scan speed was 100 mV / s. (2) After cleaning the electrode with ultrapure water, inject the test base solution containing different concentrations of PFOA and PFOS into the left and right electrochemical reaction cells and incubate for 1-10 min respectively. Based on the above conditions, scan to obtain the corresponding peak current signal. (3) Calculate the difference between the peak current signal and the blank background signal at different concentrations, and then fit the linear relationship between the peak current signal and the concentration of the target molecule. (4) Further, collect actual samples, such as food, soil, and environmental water samples, and after pretreatment, mix them with the above-mentioned test base liquid. Then, perform differential pulse voltammetry testing using the same procedure. Quantify PFOA and PFOS in the water environment by calculating the difference in peak current signals before and after incubation of the target molecules.

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