Modified electrode for detecting perfluorooctane sulfonic acid in electrogalvanizing solution and preparation method of modified electrode

Abstract

The invention discloses a modified electrode for detecting perfluorooctane sulfonic acid in an electrogalvanizing solution and a preparation method thereof.The modified electrode comprises a working electrode, and the surface of the working electrode is modified with dodecyl trimethyl ammonium bromide-zirconium-based metal organic framework / praseodymium-based dynamic metal organic gel; the praseodymium-based dynamic metal organic gel forms a stable film layer on the surface of the electrode, the zirconium-based metal organic framework is combined with the praseodymium-based dynamic metal organic gel and is bridged with dodecyl trimethyl ammonium bromide, and the dodecyl trimethyl ammonium bromide is specifically combined with perfluorooctane sulfonic acid. According to the application, the dodecyltrimethylammonium bromide and the perfluorooctane sulfonic acid are specifically combined, the praseodymium-based dynamic metal organic gel is combined to enhance an initial electrochemical luminescence signal of a system, and the zirconium-based metal organic framework is used for improving the stability of an interface, so that the interference of coexisting ions in an electrogalvanizing solution is avoided; the accuracy and the reliability of perfluorooctane sulfonic acid detection are improved.

Description

Technical Field

[0001] This application relates to the field of organic pollutant detection technology, and in particular to a modified electrode for detecting perfluorooctane sulfonic acid in electroplating zinc solution and its preparation method. Background Technology

[0002] Perfluorooctane sulfonic acid (PFOS), due to its excellent chemical stability, was once a key additive with superior performance in the electroplating industry, mainly used to suppress acid mist generation, improve coating quality, and enhance electroplating process stability. For example, in the electroplating of zinc and zinc-nickel alloys, PFOS is often used as a plating solution additive to reduce the surface tension of the plating solution and prevent defects such as pinholes and pitting in the coating. Furthermore, by reducing the surface tension of the plating solution and controlling interfacial behavior, it can also significantly reduce the adhesion and carryover of the plating solution to the workpiece surface, thereby improving process efficiency and reducing the risk of contamination.

[0003] However, due to the high bond energy of the fluorocarbon bond in PFOS (486 kJ / mol), it requires temperatures above 1000℃ to decompose, making it virtually impossible to degrade in the natural environment. Furthermore, PFOS has an atmospheric half-life exceeding 3.7 years, and its half-life in water and soil can be even longer, lasting for centuries. This stability allows PFOS to migrate globally through atmospheric circulation and ocean currents; PFOS residues have even been detected in polar bears and penguins in the Arctic and in snow in remote mountainous areas. Experimental data shows that even extremely low concentrations of PFOS are extremely harmful to humans, causing liver damage, metabolic disorders, and endocrine system disruption. It is also a potent carcinogen. Therefore, in 2009, the Stockholm Convention listed PFOS and its salts as "persistent organic pollutants," prohibiting their production. The Chinese government stipulated a complete ban on the production, use, and import / export of PFOS by 2019, and will include it in the "List of Key Controlled New Pollutants" in 2023. However, due to the many excellent properties of PFOS as an electroplating additive, people in the electroplating industry are very willing to use PFOS. Therefore, the technology and methods for effectively monitoring PFOS have become particularly urgent.

[0004] Currently, various methods are used for PFOS detection, including gas chromatography-mass spectrometry (GC-MS), liquid chromatography-tandem mass spectrometry (LC-MS-MS), ultra-high performance liquid chromatography (UHPLC), and fluorescence spectrophotometry. Among these analytical methods, water samples are most commonly analyzed, as coexisting substances have relatively little interference with PFOS detection. However, the analysis and detection of PFOS in electroplating solutions is particularly difficult. The fundamental reason is that high concentrations of cations and anions can affect PFOS detection. Furthermore, pretreatment of the electroplating solution can lead to the loss of low-concentration PFOS (typically around 10 μg / ml), introducing errors into the PFOS detection. Summary of the Invention

[0005] To improve the accuracy of PFOS detection, this application provides a modified electrode for detecting PFOS in electroplating zinc solution and its preparation method.

[0006] Firstly, this application provides a modified electrode, which adopts the following technical solution: A modified electrode includes a working electrode, the surface of which is modified with a dodecyltrimethylammonium bromide-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel, wherein the praseodymium-based dynamic metal-organic gel forms a stable film on the electrode surface, the zirconium-based metal-organic framework is bonded to the praseodymium-based dynamic metal-organic gel and bridges the dodecyltrimethylammonium bromide, wherein the dodecyltrimethylammonium bromide specifically binds to perfluorooctane sulfonic acid.

[0007] By employing the above technical solution, the dodecyltrimethylammonium bromide (DTAB) modification layer on the working electrode surface can specifically bind to the hydrophobic fluorocarbon chain and negatively charged sulfonate group of PFOS molecules through its hydrophobic long chain and positively charged hydrophilic head. This allows for highly selective recognition and enrichment of PFOS in complex matrices, effectively shielding against interference from coexisting ions (such as zinc ions and sulfate ions) in the zinc plating solution. Praseodymium ions in the praseodymium-based dynamic metal-organic gel can synergistically catalyze the reduction of co-reactants with the zirconium oxide clusters of the zirconium-based metal-organic framework, enhancing the initial electrochemiluminescence signal and improving the sensitivity for PFOS detection. Furthermore, the flexible gel network structure of the praseodymium-based dynamic metal-organic gel facilitates the formation of a stable film on the electrode surface, while the rigid porous structure of the zirconium-based metal-organic framework, through the anchoring and bridging effect of DTAB, firmly binds to the praseodymium-based dynamic metal-organic gel, forming a stable and durable composite sensing interface that ensures good reproducibility of the detection signal and a long service life of the electrode. The synergistic effect of the above components ensures rapid, highly sensitive, and highly selective detection of trace PFOS in electroplating zinc solutions, thereby significantly improving the accuracy and reliability of the detection results.

[0008] Optionally, the preparation steps of the DTAB-zirconium-based metal-organic framework include: mixing zirconium chloride, N,N-dimethylformamide, and formic acid, adding trimesic acid, heating and reacting, centrifuging to remove the supernatant, washing, and drying to obtain zirconium-based metal-organic framework 808 (MOF808); adding the MOF808 to a DTAB solution, stirring evenly, centrifuging to remove the supernatant, washing, and drying to obtain the DTAB-zirconium-based metal-organic framework.

[0009] By employing the above-mentioned technical solution, this application successfully constructed a highly crystalline and porous MOF808 support through a solvothermal reaction using zirconium chloride as the metal source and trimesic acid as the organic ligand. Then, by immersing MOF808 in a DTAB solution, the positive charge of the zirconium-oxygen cluster nodes on the MOF808 surface and the hydrophobic microenvironment of its organic framework allow DTAB molecules to be efficiently and stably loaded onto the surface and pore entrances of MOF808 through electrostatic and hydrophobic interactions. The rigid porous framework of MOF808 provides a stable support for DTAB, effectively preventing DTAB detachment or aggregation during electrochemical detection and ensuring the long-term stability of the functional interface. Simultaneously, the orderly distributed DTAB molecular layer on the surface combines its specific recognition ability for PFOS (hydrophobic and electrostatic interactions) with the high specific surface area of ​​MOF808, significantly enhancing the selective enrichment ability of the composite material for trace PFOS in complex electroplating solutions, laying a material foundation for subsequent high-sensitivity detection.

[0010] Optionally, the preparation steps of the praseodymium-based dynamic metal-organic gel include: mixing dimethyl sulfoxide and deionized water, adding 1,10-phenanthroline-2,9-dicarboxylic acid and terephthalic acid, adding triethylamine under ultrasonic conditions, adding praseodymium nitrate hexahydrate, heating and stirring, centrifuging to remove the supernatant, washing, and freeze-drying to obtain the praseodymium-based dynamic metal-organic gel.

[0011] By employing the above technical solution, this application first fully dissolves and deprotonates the 1,10-phenanthroline-2,9-dicarboxylic acid ligand, then combines it with a terephthalic acid ligand, and finally automatically assembles it with praseodymium ions under heating conditions to construct a metal-organic gel with a flexible, three-dimensional network structure. This facilitates the formation of a uniform, dense, and strongly adherent active film on the electrode surface, providing a stable substrate for subsequent modification. Furthermore, the praseodymium ions are uniformly and densely immobilized within the gel network, serving as a highly efficient catalytic center and laying the material foundation for subsequent synergistic catalysis with zirconium-based metal-organic frameworks and co-catalyzing co-reactants (such as persulfate) to generate a strong initial electrochemiluminescence signal.

[0012] Secondly, this application provides a method for preparing a modified electrode, employing the following technical solution: A method for preparing a modified electrode includes the following steps: S1. Add DTAB-zirconium-based metal-organic framework to N,N-dimethylformamide and disperse by ultrasonication to obtain DTAB-zirconium-based metal-organic framework dispersion; S2. Add praseodymium dynamic organometallic gel to N,N-dimethylformamide and disperse by ultrasonication to obtain praseodymium dynamic organometallic gel dispersion; S3. The praseodymium-based dynamic metal-organic gel dispersion is drop-coated onto the surface of a glassy carbon electrode and dried with infrared light to obtain a praseodymium-based dynamic metal-organic gel / glassy carbon electrode. S4. The DTAB-zirconium-based metal-organic framework dispersion is drop-coated onto the surface of the praseodymium-based dynamic metal-organic gel / glassy carbon electrode and dried to obtain a working electrode with surface-modified DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel.

[0013] By employing the above technical solution, this application first forms a praseodymium-based dynamic metal-organic gel layer on a glassy carbon electrode, creating a robust conductive catalytic layer. Then, a DTAB-zirconium-based metal-organic framework layer is coated onto this layer, ensuring that the praseodymium catalytic center and the DTAB recognition site are spatially closely adjacent. This significantly shortens the distance between the captured target analyte (PFOS) and the catalytic center, facilitating efficient coupling of recognition and signal transduction, thereby improving response speed and sensitivity. Furthermore, infrared drying of the drop-coated electrode ensures uniform film formation on the electrode surface, guaranteeing the electrode's mechanical stability, uniform electrochemical activity, and high reproducibility of the detection signal.

[0014] Optionally, in S1, the concentration of the DTAB-zirconium-based metal-organic framework dispersion is 1 mg / mL.

[0015] By adopting the above technical solution, this application uses a DTAB-zirconium-based metal-organic framework dispersion of a specific concentration, which can ensure that the dispersion does not affect the stability of the system while providing a sufficient number of DTAB molecules, thereby ensuring that the DTAB-zirconium-based metal-organic framework is fully bound to the PFOS analyte.

[0016] Optionally, in S2, the concentration of the praseodymium dynamic metal-organic gel dispersion is 1 mg / mL.

[0017] By adopting the above technical solution, this application uses a praseodymium-based dynamic metal-organic gel dispersion of a specific concentration, which can ensure that the dispersion does not affect the stability of the system while ensuring that the praseodymium-based dynamic metal-organic gel is uniformly dispersed on the electrode surface.

[0018] Thirdly, this application provides an application of a modified electrode in the detection of PFOS in an electroplating zinc solution.

[0019] Optionally, the application includes the following steps: Step 1: Mix sulfuric acid and phosphate buffer, add PFOS to obtain PFOS standard solution; Step 2: Place the working electrode of the surface-modified DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel in the PFOS standard solution, then add persulfate and phosphate buffer, perform electrochemiluminescence measurement, and obtain the linear regression equation; Step 3: Mix sulfuric acid and phosphate buffer, add the sample to be tested, insert the working electrode of the surface-modified DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel, then add persulfate and phosphate buffer, measure the electrochemiluminescence intensity, and obtain the concentration of PFOS in the sample to be tested according to the linear regression equation.

[0020] By adopting the above technical solution, this application uses sulfuric acid to adjust the phosphate buffer to a low pH environment to prepare the PFOS standard solution, simulating the acidic matrix conditions of the actual diluted electroplating zinc solution. This ensures that the standard curve establishment process is highly consistent with the actual sample detection process in terms of the PFOS enrichment mechanism. Furthermore, the entire detection process requires no complex extraction, separation, or derivatization pretreatment of the electroplating zinc stock solution; simple dilution with acidic PBS buffer is sufficient for direct determination. This greatly simplifies the operation process, shortens the analysis time, and avoids the loss of target analytes or the introduction of errors that may result from cumbersome pretreatment.

[0021] Preferably, the pH value of the phosphate buffer solution is 7.5.

[0022] By employing the above technical solution, the working electrode of the surface-modified DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel exhibits a large electrochemiluminescence intensity in phosphate buffer solution when the pH value is 7.5. Furthermore, the phosphate buffer solution can, to some extent, resist the influence of external acid or alkali addition on the solution pH.

[0023] Optionally, in step one, the concentration of PFOS in the PFOS standard solution is 1.0 × 10⁻⁶. -13 g / L-1.0×10 -5 g / L.

[0024] By adopting the above technical solution, this application uses a PFOS standard solution of a specific concentration. On the one hand, it can avoid the instrument signal from exceeding the linear response range due to excessively high concentrations of PFOS, resulting in inaccurate detection results. On the other hand, it also prevents the detection signal from being too weak and being buried by instrument noise and background signals when the concentration is too low, which would lead to a significant decrease in signal-to-noise ratio and an increase in measurement uncertainty.

[0025] Preferably, in step two, cyclic voltammetry is performed within the electrochemical window range of -1.8 to 0 V at a scan rate of 0.1 V / s to record the electrochemiluminescence value of the PFOS standard solution. The logarithm of the PFOS concentration is used as the abscissa, and the difference in electrochemiluminescence values ​​with and without PFOS is used as the ordinate to obtain a linear regression equation.

[0026] Preferably, the detection limit of PFOS is 1.9 × 10⁻⁶. -14 g / L.

[0027] Fifthly, this application provides a sensor for detecting PFOS, including a modified electrode.

[0028] Optionally, it also includes an auxiliary electrode and a reference electrode, wherein the auxiliary electrode is a platinum electrode and the reference electrode is a silver chloride electrode.

[0029] By adopting the above technical solutions, the platinum electrode has good conductivity, strong corrosion resistance and chemical stability, while the silver chloride electrode has a stable potential and can respond quickly to changes in potential in the solution. It can be used in a variety of different electrolyte systems and has good versatility.

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. The DTAB modification layer on the working electrode surface of this application can selectively identify and enrich PFOS, effectively shielding the interference of coexisting ions in the zinc plating solution. Praseodymium ions in the praseodymium-based dynamic metal-organic gel can synergistically catalyze the reduction of co-reactants with the zirconium-oxygen clusters of the zirconium-based metal-organic framework, enhancing the initial electrochemiluminescence signal of the system and improving the sensitivity for PFOS detection. Furthermore, the flexible gel network structure of the praseodymium-based dynamic metal-organic gel facilitates the formation of a stable film on the electrode surface, while the zirconium-based metal-organic framework can firmly bind to the praseodymium-based dynamic metal-organic gel, forming a stable and durable composite sensing interface, ensuring good reproducibility of the detection signal and a long service life of the electrode. The synergistic effect of these components ensures rapid, highly sensitive, and highly selective detection of trace PFOS in the zinc plating solution, thereby significantly improving the accuracy and reliability of the detection results. 2. This application utilizes zirconium chloride as the metal source and trimesic acid as the organic ligand to successfully construct a highly crystalline and porous MOF808 support through a solvothermal reaction. Then, by immersing MOF808 in a DTAB solution, the positive charge of the zirconium-oxygen cluster nodes on the MOF808 surface and the hydrophobic microenvironment of its organic framework allow DTAB molecules to be efficiently and stably loaded onto the surface and pore entrances of MOF808 through electrostatic and hydrophobic interactions. The rigid porous framework of MOF808 provides a stable support for DTAB, effectively preventing its detachment or aggregation during electrochemical detection and ensuring the long-term stability of the functional interface. Simultaneously, the orderly distributed DTAB molecule layer on the surface combines its specific recognition ability for PFOS (hydrophobic and electrostatic interactions) with the high specific surface area of ​​MOF808, significantly enhancing the selective enrichment ability of the composite material for trace PFOS in complex electroplating solutions, laying a material foundation for subsequent high-sensitivity detection. 3. This application uses sulfuric acid to adjust the phosphate buffer to a low pH environment to prepare the PFOS standard solution, simulating the acidic matrix conditions of the actual diluted zinc plating solution. This ensures that the standard curve establishment process is highly consistent with the actual sample detection process in terms of the PFOS enrichment mechanism. Furthermore, the entire detection process requires no complex extraction, separation, or derivatization pretreatment of the zinc plating stock solution; simple dilution with acidic PBS buffer is sufficient for direct determination. This greatly simplifies the operation, shortens the analysis time, and avoids the loss of target analytes or the introduction of errors that may result from cumbersome pretreatment. Attached Figure Description

[0031] Figure 1 This is the electrochemiluminescence response diagram and linear regression equation from Example 2 of this application. Wherein, A is the electrochemiluminescence response diagram of the DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode in PBS solutions with different PFOS concentrations; B is the linear regression equation obtained from the electrochemiluminescence values ​​in A; Figure 2 This is an electrochemiluminescence response diagram of a three-electrode system with different working electrodes in Example 4 of this application, obtained by electrochemiluminescence testing. Wherein, a is a glassy carbon electrode, b is a praseodymium-based dynamic metal-organic gel / glassy carbon electrode, c is MOF808 / glassy carbon electrode, d is DTAB-MOF808 / glassy carbon electrode, and e is DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode. Figure 3 This is an electrochemiluminescence response diagram showing the effect of different coexisting ions on the electrochemiluminescence signal intensity in Example 5 of this application. In the diagram, a represents the blank control group, b represents the experimental group, and c represents control group 1. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] This application designs a modified electrode, including a working electrode, the surface of which is modified with DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel. The preparation steps of the DTAB-zirconium-based metal-organic framework include: mixing zirconium chloride, N,N-dimethylformamide, and formic acid, adding trimesic acid, heating and reacting at 120-140℃ for 2-3 days, centrifuging at 8000-10000 r / min for 10-20 min, removing the supernatant, washing, and drying at 50-70℃ for 12-24 h to obtain the zirconium-based metal-organic framework; adding the zirconium-based metal-organic framework to a DTAB solution and stirring at 300-500 r / min for 12-24 h. Centrifuge at 8000-10000 r / min for 10-20 min, remove supernatant, wash, and dry at 50-70℃ for 12-24 h to obtain DTAB-zirconium-based metal-organic framework; the preparation steps of praseodymium-based dynamic metal-organic gel include: mixing dimethyl sulfoxide and deionized water, adding 1,10-phenanthroline-2,9-dicarboxylic acid and terephthalic acid, adding triethylamine under ultrasonic conditions of 300-500W, adding praseodymium nitrate hexahydrate, heating and stirring at 50-70℃ for 2-4 h, centrifuging at 8000-10000 r / min for 10-20 min, washing, and freeze-drying at -50~-70℃ for 12-24 h to obtain praseodymium-based dynamic metal-organic gel.

[0034] A method for preparing a modified electrode includes the following steps: S1. Add DTAB-zirconium-based metal-organic framework to N,N-dimethylformamide and ultrasonically disperse at 300-500W for 5-10 min to obtain DTAB-zirconium-based metal-organic framework dispersion; S2. Add praseodymium dynamic metal-organic gel to N,N-dimethylformamide and ultrasonically disperse at 300-500W for 5-10 minutes to obtain praseodymium dynamic metal-organic gel dispersion. S3. The praseodymium-based dynamic metal-organic gel dispersion is drop-coated onto the surface of a glassy carbon electrode and dried with infrared light at 2-4 μm for 10-20 min to obtain a praseodymium-based dynamic metal-organic gel / glassy carbon electrode. S4. The DTAB-zirconium-based metal-organic framework dispersion is drop-coated onto the surface of the praseodymium-based dynamic metal-organic gel / glassy carbon electrode and dried to obtain a working electrode with surface-modified DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel.

[0035] Application of a modified electrode in the detection of PFOS in electroplating zinc solution.

[0036] A method for detecting PFOS includes the following steps: Step 1: Mix sulfuric acid and phosphate buffer, add PFOS to obtain PFOS standard solution. The concentration of PFOS in the PFOS standard solution is 1.0 × 10⁻⁶.-13 g / L-1.0×10 -5 g / L; Step 2: Place the working electrode of the surface-modified DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel in PFOS standard solution, then add persulfate and phosphate buffer, and perform electrochemiluminescence measurement. The electrochemical window is -1.8 to 0 V, the scan rate is 0.1 V / s, and the linear regression equation is obtained. Step 3: Mix sulfuric acid and phosphate buffer, add the sample to be tested, insert the electrode with surface modified DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel, and then add persulfate and phosphate buffer. Use the above electrode as the working electrode to measure the electrochemiluminescence intensity, and obtain the concentration of PFOS in the sample to be tested according to the linear regression equation.

[0037] A sensor for detecting PFOS includes a working electrode modified with a surface-modified DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel, an auxiliary electrode being a platinum electrode, and a reference electrode being a silver chloride electrode.

[0038] All raw materials used in the embodiments of this application are commercially available, wherein: 1,10-Phenanthroline-2,9-Dicarboxylic Acid, Zhengzhou Yande Biotechnology Co., Ltd.; Dimethyl sulfoxide, Shanghai Lingfeng Chemical Reagent Co., Ltd.; Triethylamine, Shanghai Aladdin Biochemical Technology Co., Ltd.; Praseodymium nitrate hexahydrate, Shanghai Aladdin Biochemical Technology Co., Ltd.; 1,3,5-Benzotricarboxylic acid, Shanghai Aladdin Biochemical Technology Co., Ltd.; Zirconium chloride, Sinopharm Chemical Reagent Co., Ltd.; Formic acid, Sinopharm Chemical Reagent Co., Ltd.; N,N-Dimethylformamide, Shanghai Aladdin Biochemical Technology Co., Ltd. DTAB, Shanghai Aladdin Biochemical Technology Co., Ltd. Phosphate buffer, pH 7.4, Shanghai Ruichu Biotechnology Co., Ltd.

[0039] Preparation Example 1 Preparation of praseodymium-based dynamic organometallic gel: 5 mL of dimethyl sulfoxide and 5 mL of deionized water were mixed, and 45 mg of 1,10-phenanthroline-2,9-dicarboxylic acid and 10 mg of 1,3,5-benzenetricarboxylic acid were added. Under ultrasonic conditions of 500 W, 45 μL of triethylamine was added dropwise to deprotonate 1,10-phenanthroline-2,9-dicarboxylic acid. Then, 30 mg of praseodymium nitrate hexahydrate was added. The mixture was stirred at 60 °C for 3 h, centrifuged at 8000 r / min for 15 min, and the supernatant was collected. The supernatant was washed with anhydrous ethanol and deionized water and then freeze-dried at -50 °C for 24 h to obtain praseodymium-based dynamic organometallic gel.

[0040] Preparation Example 2 Preparation of DTAB-zirconium-based metal-organic framework: 1.2 g of zirconium chloride, 24 mL of N,N-dimethylformamide, and 6 mL of formic acid were mixed and stirred until fully dissolved. The mixture was placed in a high-pressure reactor and heated at 130 °C for 48 h. After centrifugation at 8000 r / min for 15 min, the supernatant was removed, and the mixture was thoroughly washed with deionized water and anhydrous ethanol. The mixture was then dried in a vacuum drying oven at 60 °C for 12 h to obtain MOF808. 0.1 g of MOF808 was added to 100 mL of an aqueous solution containing 0.5 g of DTAB, stirred at 500 r / min for 24 h, washed with deionized water, centrifuged at 8000 r / min for 15 min, and the supernatant was removed. The mixture was then dried at 60 °C for 12 h to obtain DTAB-MOF808.

[0041] Example 1: Preparation of DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode 5 mg of DTAB-MOF808 obtained in Preparation Example 2 was added to 5 mL of N,N-dimethylformamide and ultrasonically dispersed at 500 W for 5 min to obtain a 1 mg / mL DTAB-MOF808 dispersion. 50 mg of praseodymium-based dynamic metal-organic gel obtained in Preparation Example 1 was added to 50 mL of N,N-dimethylformamide and ultrasonically dispersed at 500 W for 5 min to obtain a 1 mg / mL praseodymium-based dynamic metal-organic gel dispersion. 6 μL of the praseodymium-based dynamic metal-organic gel dispersion was drop-coated onto the surface of a glassy carbon electrode and dried under infrared light for 10 min at a wavelength of 3 μm to obtain a praseodymium-based dynamic metal-organic gel / glassy carbon electrode. Subsequently, 6 μL of the DTAB-MOF808 dispersion was drop-coated onto the surface of the praseodymium-based dynamic metal-organic gel / glassy carbon electrode and air-dried to obtain a DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode.

[0042] Example 2: Construction of the Linear Regression Equation A 0.1 mol / L phosphate buffer solution with a pH of 7.4 was prepared to a pH of 2 using sulfuric acid, thus obtaining a diluent. PFOS was then diluted with the diluent to obtain PFOS standard solutions of different concentrations. The concentrations of PFOS were 1.0 × 10⁻⁶. - 13 g / L, 1.0×10 -12 g / L, 1.0×10 -11 g / L, 1.0×10 -10 g / L, 1.0×10 -9 g / L, 1.0×10 -8 g / L, 1.0×10 - 7 g / L, 1.0×10 -6 g / L, 1.0×10 -5 g / L. The DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode obtained in Example 1 was placed in 10 mL of the above-mentioned PFOS standard solutions of different concentrations to enrich PFOS for 30 min. Then, this electrode was used as the working electrode, the silver chloride electrode as the reference electrode, and the platinum electrode as the auxiliary electrode to obtain a three-electrode system. Electrochemiluminescence measurements were performed using 25 mL of 0.1 mol / L PBS buffer solution containing 0.1 mol / L potassium persulfate as the electrolyte. The electrochemical window was -1.8 V, the scan rate was 0.1 V / s, and the logarithm of the standard solution concentration (logC) and the difference in electrochemiluminescence values ​​before and after the addition of PFOS (ΔECL) were recorded to obtain the linear regression equation. The results are shown in […]. Figure 1 .

[0043] Depend on Figure 1 We know that the linear regression equation is ΔECL = 13282.85 + 761.46logC, and the correlation coefficient RC is... 2 =0.998, the limit of detection is 1.9×10 -14 g / L indicates that the three-electrode system consisting of DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode used in this application measured 1.0 × 10 g / L. -13 g / L-1.0×10 -5 PFOS exhibits good linearity within the g / L range.

[0044] Example 3: Detection of PFOS in electroplating zinc solution A zinc plating solution commonly used for sulfates was selected, and PFOS was added. Using the diluent obtained in Example 1, a zinc plating solution containing 5 mg / L of PFOS was prepared and used as the test sample. In the test sample, the concentration of zinc sulfate heptahydrate was 200 g / L, the concentration of sodium sulfate decahydrate was 30 g / L, the pH was 5, the temperature was 30°C, and the current density was 3 A / dm³.2 Take 50 mL of the sample to be tested and insert it into the three-electrode system obtained in Example 1. Use 25 mL of 0.1 mol / L PBS buffer solution containing 0.1 mol / L potassium persulfate as the electrolyte and measure the electrochemiluminescence value. The concentration of PFOS in the sample to be tested is obtained according to the linear regression equation. The results are shown in Table 1.

[0045] Table 1. Accuracy of PFOS detection in electroplating zinc solution

[0046] As shown in Table 1, the coefficient of variation of PFOS measured by the three-electrode system consisting of a surface-modified DTAB-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel working electrode in this application is 0.31%, indicating good accuracy.

[0047] Comparative Example 1 The difference between this comparative example and Example 2 is that the DTAB-MOF808 in Example 2 is replaced with MOF808 in this comparative example, resulting in MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode.

[0048] A linear regression equation was constructed for the MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode according to the method in Example 2. The results showed that the linear regression equation was ΔECL = 15291.64 + 886.29 logC, and the correlation coefficient R was [value missing]. 2 =0.998, the limit of detection is 1.2×10 -14 g / L.

[0049] The PFOS in the electroplating zinc solution was detected using the MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode according to the method in Example 3. Based on the corresponding linear regression equation curve, the concentration of PFOS in the electroplating zinc solution can be obtained. The results are shown in Table 2.

[0050] Table 2. Accuracy of PFOS detection in electroplating zinc solution in Comparative Example 1

[0051] As shown in Table 2, the actual concentration of PFOS should be 5 mg / L, but the results of the tests in Comparative Example 1 are 3.28 mg / L, 2.96 mg / L, and 3.01 mg / L, which is a large deviation. This error is mainly due to the absence of a DTAB selective film for PFOS on the surface of the modified electrode, resulting in a decrease in the selectivity of the modified electrode.

[0052] Example 4: Electrochemiluminescence test

[0053] Using the MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode, MOF808 / glassy carbon electrode, DTAB-MOF808 / glassy carbon electrode obtained in Comparative Example 1, and the DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode obtained in Example 1 as working electrodes, and a silver chloride electrode as the reference electrode and a platinum electrode as the auxiliary electrode, electrochemiluminescence assays were performed using 25 mL of 0.1 mol / L PBS buffer solution containing 0.1 mol / L potassium persulfate. The results are shown in [Figure number missing]. Figure 2 .

[0054] Preparation of MOF808 / glassy carbon electrode: 5 mg of MOF808 was added to 5 mL of N,N-dimethylformamide and ultrasonically dispersed at 500 W for 5 min to obtain a 1 mg / mL MOF808 dispersion. 6 μL of the MOF808 dispersion was drop-coated onto the surface of a glassy carbon electrode and dried under infrared light for 10 min at a wavelength of 3 μm to obtain the MOF808 / glassy carbon electrode.

[0055] Preparation of DTAB-MOF808 / glassy carbon electrode: 6 μL of the DTAB-MOF808 dispersion obtained in Example 1 was drop-coated onto the surface of a glassy carbon electrode and dried with infrared light for 10 min at a wavelength of 3 μm to obtain the DTAB-MOF808 / glassy carbon electrode.

[0056] Depend on Figure 2 It is evident that both the praseodymium-based dynamic metal-organic gel / glassy carbon electrode and the MOF808 / glassy carbon electrode exhibit strong electrochemiluminescence (ECL) intensity. However, due to the influence of the 12-carbon chain of DTAB on electron transport, the ECL intensity of the DTAB-MOF808 / glassy carbon electrode is weaker than that of the MOF808 / glassy carbon electrode. Even so, when MOF808 and praseodymium-based dynamic metal-organic gel are combined, the ECL intensity of the DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode significantly increases, reaching an ECL value of 12591, indicating a significant improvement in analytical sensitivity.

[0057] Example 5: Quantitative analysis of PFOS in electroplating zinc solution

[0058] Zinc sulfate and sodium sulfate were prepared into a solution containing 0.2 g / L zinc sulfate and 0.03 g / L sodium sulfate using 50 mL of the diluent obtained in Example 1, and this solution served as control group 1. The diluent obtained in Example 1 served as a blank control group, containing 1.0 × 10⁻⁶ g / L zinc sulfate and sodium sulfate. -6 The PFOS standard solution at g / L was used as the experimental group. The DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode obtained in Example 1 was used as the working electrode, the silver chloride electrode as the reference electrode, and the platinum electrode as the auxiliary electrode, forming a three-electrode system. Electrochemiluminescence assays were performed, and the results are shown in [Figure 1]. Figure 3 .

[0059] Depend on Figure 3 It was found that when the DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode was enriched in a solution containing PFOS, the electrochemiluminescence intensity of the modified electrode decreased sharply due to PFOS enrichment. However, when the DTAB-MOF808 / praseodymium-based dynamic metal-organic gel / glassy carbon electrode was enriched in a solution of zinc sulfate and sodium sulfate, the electrochemiluminescence intensity was almost identical to that of the unenriched modified electrode. This indicates that even with a large presence of zinc ions and sulfate ions in the zinc sulfate plating solution, the quantitative analysis of PFOS is not affected.

[0060] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A modified electrode, characterized in that, The device includes a working electrode, the surface of which is modified with a dodecyltrimethylammonium bromide-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel. The praseodymium-based dynamic metal-organic gel forms a stable film on the electrode surface. The zirconium-based metal-organic framework is combined with the praseodymium-based dynamic metal-organic gel and bridges the dodecyltrimethylammonium bromide. The dodecyltrimethylammonium bromide is specifically bound to perfluorooctane sulfonic acid.

2. The modified electrode according to claim 1, characterized in that, The preparation steps of the dodecyltrimethylammonium bromide-zirconium-based metal-organic framework include: mixing zirconium chloride, N,N-dimethylformamide, and formic acid, adding trimesic acid, heating and reacting, centrifuging to remove the supernatant, washing, and drying to obtain zirconium-based metal-organic framework 808; adding the zirconium-based metal-organic framework 808 to a dodecyltrimethylammonium bromide solution, stirring evenly, centrifuging to remove the supernatant, washing, and drying to obtain the dodecyltrimethylammonium bromide-zirconium-based metal-organic framework.

3. The modified electrode according to claim 1, characterized in that, The preparation steps of the praseodymium-based dynamic organometallic gel include: mixing dimethyl sulfoxide and deionized water, adding 1,10-phenanthroline-2,9-dicarboxylic acid and terephthalic acid, adding triethylamine under ultrasonic conditions, adding praseodymium nitrate hexahydrate, heating and stirring, centrifuging to remove the supernatant, washing, and freeze-drying to obtain the praseodymium-based dynamic organometallic gel.

4. A method for preparing a modified electrode according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Add dodecyltrimethylammonium bromide-zirconium-based metal-organic framework to N,N-dimethylformamide and disperse by ultrasonication to obtain a dispersion of dodecyltrimethylammonium bromide-zirconium-based metal-organic framework; S2. Add praseodymium dynamic organometallic gel to N,N-dimethylformamide and disperse by ultrasonication to obtain praseodymium dynamic organometallic gel dispersion; S3. The praseodymium-based dynamic metal-organic gel dispersion is drop-coated onto the surface of a glassy carbon electrode and dried with infrared light to obtain a praseodymium-based dynamic metal-organic gel / glassy carbon electrode. S4. The dodecyltrimethylammonium bromide-zirconium-based metal-organic framework dispersion is drop-coated onto the surface of the praseodymium-based dynamic metal-organic gel / glassy carbon electrode and dried to obtain a working electrode with surface-modified dodecyltrimethylammonium bromide-zirconium-based metal-organic framework / praseodymium-based dynamic metal-organic gel.

5. The application of the modified electrode according to any one of claims 1-3 in the detection of perfluorooctane sulfonic acid in an electroplating zinc solution.

6. The application of the modified electrode according to claim 5 in the detection of perfluorooctane sulfonic acid in electroplating zinc solution, characterized in that, Includes the following steps: Step 1: Mix sulfuric acid and phosphate buffer, add perfluorooctane sulfonic acid to obtain perfluorooctane sulfonic acid standard solution; Step 2: Place the working electrode in the perfluorooctane sulfonic acid standard solution, then add persulfate and phosphate buffer solution, perform electrochemiluminescence measurement, and obtain the linear regression equation; Step 3: Mix sulfuric acid and phosphate buffer, add the sample to be tested, insert the working electrode, then add persulfate and phosphate buffer, measure the electrochemiluminescence intensity, and obtain the concentration of perfluorooctane sulfonic acid in the sample to be tested according to the linear regression equation.

7. The application of the modified electrode according to claim 6 in the detection of perfluorooctane sulfonic acid in electroplating zinc solution, characterized in that, In step one, the concentration of perfluorooctane sulfonic acid in the perfluorooctane sulfonic acid standard solution is 1.0 × 10⁻⁶. -13 g / L-1.0×10 -5 g / L.

8. A sensor for detecting perfluorooctane sulfonic acid, characterized in that, Includes the modified electrode as described in any one of claims 1-3.

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