Beta-cyclodextrin / ionic liquid compound electrode, preparation method thereof and nonyl phenol detection method

Abstract

The invention belongs to the technical field of electrochemical analysis methods, and particularly relates to a beta-cyclodextrin / ionic liquid compound electrode, a preparation method thereof and a nonyl phenol detection method. When being applied to detection of nonyl phenol, the nano-material has good reproducibility, stability and selectivity, the linear range is 5 * 10 <-9 >-5 * 10 <-4 > mol L <-1 >, the detection limit is 1 * 10 <-9 > mol L <-1 >, the detection linear range is wide, and the sensitivity is high; and the adding standard recovery rate is 90.8%-98.8%. According to the preparation method, the nano graphite powder, the beta-cyclodextrin, the ionic liquid and the binder are mixed and ground, the beta-cyclodextrin / ionic liquid compound electrode can be prepared through a combination method, and the method is simple and easy to operate.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical analysis methods, and particularly relates to a beta-cyclodextrin / ionic liquid composite electrode, a preparation method thereof, and a nonylphenol detection method. Background Art

[0002] Environmental endocrine disrupting chemicals (EDCs) are a class of toxic organic compounds that can migrate in the environment. They easily accumulate in organisms and are difficult to degrade. They can also be amplified through the food chain, posing serious hazards to the ecological environment and human health. With the destruction of the ecological environment and the gradual increase in diseases caused by environmental endocrine disruptors, people have gradually paid attention to the research and control of environmental endocrine disruptors. Its typical representative is nonylphenol (NP), also known as 4-nonylphenol, whose molecular formula is C 15 H 24 O. It is a liquid at room temperature, typically light yellow or colorless. The primary source of nonylphenol in the environment is industrial production. Due to its excellent surface activity and emulsifying properties, it has been widely used in the production and processing of detergents, emulsifiers, pesticides, plasticizers, and food contact materials. Currently, the use of nonylphenol is strictly restricted in many countries, including the European Union and China, but it is still widely used in some developing countries. Even though nonylphenol has been strictly regulated across a large area, the existing nonylphenol in the environment will continue to exist for a long time due to its difficulty in degradation and continue to exert its impact.

[0003] NPs primarily interfere with the endocrine system by mimicking endogenous estrogens, affecting normal physiological regulation and the development and function of the reproductive system. For example, they can cause testicular atrophy in men, affect male hormone synthesis, and reduce sperm quality; and in women, they can cause menstrual disorders, decreased ovarian function, and even infertility. Exposure in pregnant women can affect fetal gonadal development and increase the risk of birth defects. They also pose a significant threat to aquatic ecosystems. For example, low concentrations of nonylphenol can cause male fish to produce vitellogenin, resulting in oxidative damage and estrogenic effects on aquatic organisms, affecting population sex ratios and leading to feminization of aquatic organisms.

[0004] In-depth research into nonylphenol detection technology is crucial for both the prevention and treatment of environmental endocrine-related diseases and the maintenance of environmental homeostasis. Currently, commonly used methods for nonylphenol detection include chromatography and chromatography-mass spectrometry. However, current nonylphenol detection methods still have shortcomings that require improvement. For example, the large size of large-scale instrumentation, complex sample pretreatment, and time-consuming detection processes hinder rapid on-site testing. Furthermore, the instrument's operating specifications are stringent, requiring specialized personnel. Furthermore, the detection limit and the testing environment may also affect the detection results.

[0005] Compared with other methods, electrochemical analysis detection instruments are more portable, easy to operate, more responsive, more selective and sensitive, and can make up for the shortcomings of current detection. In the prior art, the Chinese invention patent application number 202410245109.5 discloses a method for preparing nickel / porous boron-doped diamond electrochemical sensor electrode materials for detecting nonylphenol, specifically: 1. Prepare boron-doped diamond electrodes; 2. Place the boron-doped diamond in a magnetron sputtering device and evacuate to 10 -4 Pa, turn on the DC sputtering power supply, the sputtering pressure is 2Pa, the sputtering time is 20s, and the sputtering atmosphere is 40sccm of argon to form a nickel / boron doped diamond structure; 3. Place the sample prepared in step 2 in a tube furnace in a nitrogen or argon atmosphere and heat it to 900℃ for 10 minutes. At high temperature, the metallic nickel becomes nanoparticles and etches the diamond to form a nickel / porous boron doped diamond structure. The linear range of the electrode is 1×10 -8 ~10×10 -7 mol L -1 , the detection limit was 0.63×10 -8 mol L -1 The preparation of this electrode material also requires magnetron sputtering and high-temperature treatment, which is a complex preparation method. In addition, the electrode has low sensitivity, poor reproducibility and stability. Summary of the Invention

[0006] Based on this, the present application provides a β-cyclodextrin / ionic liquid composite electrode, a preparation method thereof, and a method for detecting nonylphenol to solve the technical problems in the prior art that the electrode material has low sensitivity, poor reproducibility, and complex preparation method in detecting nonylphenol.

[0007] The technical solutions of this application to solve the above technical problems are as follows:

[0008] A method for preparing a β-cyclodextrin / ionic liquid composite electrode comprises the following steps:

[0009] The nanographite powder, β-cyclodextrin, ionic liquid and binder are mixed and then fully ground to obtain a paste;

[0010] The paste is placed in a polytetrafluoroethylene tube and heated to obtain an electrode column. The surface of the electrode column is polished and smooth to obtain a β-cyclodextrin / ionic liquid composite electrode.

[0011] Preferably, as described in the above preparation method, in the paste, the total amount of the nano-graphite powder, β-cyclodextrin and ionic liquid added per microliter of binder is 3 to 8 mg.

[0012] Preferably, as described in the above preparation method, the mass ratio of the nano-graphite powder to the β-cyclodextrin is (5 to 15):1.

[0013] Preferably, as described in the above preparation method, the mass ratio of the nano-graphite powder and β-cyclodextrin to the ionic liquid is (1 to 3):1.

[0014] Preferably, as in the above preparation method, the binder is paraffin oil or dimethyl silicone oil.

[0015] Preferably, as described in the above preparation method, the ionic liquid is 1-octylpyridinium hexafluorophosphate.

[0016] A beta-cyclodextrin / ionic liquid composite electrode is prepared by the above-mentioned preparation method.

[0017] An electrochemical sensor based on a β-cyclodextrin / ionic liquid composite electrode adopts the above-mentioned β-cyclodextrin / ionic liquid composite electrode as a working electrode.

[0018] A method for detecting nonylphenol comprises the following steps:

[0019] constructing an electrochemical sensor based on the β-cyclodextrin / ionic liquid composite electrode as described above;

[0020] Constructing an electrolyte system, wherein the electrolyte system consists of a sample solution to be detected and a PBS buffer solution, wherein the concentration of the PBS buffer solution is 0.1 M and the pH is 6 to 9;

[0021] The concentration of nonylphenol was measured.

[0022] Preferably, as in the above-mentioned method for detecting nonylphenol, the concentration of nonylphenol is detected by differential pulse voltammetry, and the concentration is carried out for 60 seconds at open circuit potential.

[0023] Compared with the prior art, this application has at least the following advantages:

[0024] The present invention provides a β-cyclodextrin / ionic liquid composite electrode (β-CD / nano-CILPE, hereinafter referred to as the composite electrode), which is applied to the detection of nonylphenol and has good sensitivity, reproducibility, stability and selectivity. Under optimal experimental conditions, the linear range of nonylphenol detection using differential pulse voltammetry is 5×10 -9 ~5×10 -4 molL -1 , the detection limit is 1×10 -9 mol L -1 , wide detection linear range, high sensitivity; spike recovery rate is 90.8% to 98.8%; for interfering substances, such as 100 times the Mg 2+ , Ca 2+ 、Na + , K+ 、Cu 2+ 、SO4 2- 、Cl - , 10 times the p-nitrophenol (p-NP), hydroquinone (HQ), resorcinol (RES), catechol (CAT) to 5×10 -5 mol L -1 The effect on nonylphenol detection was not significant, indicating that β-CD / nano-CILPE had good selectivity for nonylphenol.

[0025] The present invention also provides a method for preparing a β-cyclodextrin / ionic liquid composite electrode. The β-cyclodextrin / ionic liquid composite electrode can be prepared by simply mixing and grinding nanographite powder, β-cyclodextrin, an ionic liquid, and a binder, and then self-assembling. The method is simple and easy to operate. The composite electrode prepared was measured six times with the same electrode, and the calculated relative standard deviation (RSD) of the peak current result was 1.41%. When the six composite electrodes were used to test nonylphenol at equal concentrations, the RSD of the peak current was 3.17%, indicating good reproducibility. After the modified electrode was stored for one month under dry conditions at room temperature, the peak current value was measured at the same concentration of nonylphenol, and the peak current value was still 99.1% of the initial value, indicating that the β-CD / nano-CILPE exhibits excellent stability.

[0026] The present invention also provides an electrochemical sensor based on a β-cyclodextrin / ionic liquid composite electrode, and its application in the field of nonylphenol detection. The sensor is simple to operate and has not only good sensitivity and selectivity but also good reproducibility and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Cyclic voltammograms of (a) nano-CPE; (b) β-CD / nano-CPE; (c) β-CD / nano-CILPE in 5 mM K3[Fe(CN)6] / K4[Fe(CN)6] probe solution containing 0.1 M KCl, scan rate: 50 mV s -1 (A); AC impedance spectrum (B).

[0028] Figure 2 (a) nano-CPE; (b) β-CD / nano-CPE; (c) β-CD / nano-CILPE in 5 mM [Fe(CN)6] containing 0.1 M KCl 3- / 4- Cyclic voltammograms at different scan rates in the solution. From inside to outside, the scan rates are: 25, 50, 75, 100, 125, 150, 175, and 200 mV s -1 .

[0029] Figure 3 (A) Differential pulse voltammograms of 100 μM NP at different pH values ​​(pH:ae are 5, 6, 7, 8, and 9, respectively); (B) Effect of pH value on the peak potential and peak current of NP.

[0030] Figure 4 The effect of β-cyclodextrin content in 0.1 M PBS (pH 7.0) on the response current of 100 μM NP.

[0031] Figure 5 The figure shows the effects of accumulation potential and open circuit potential on the peak current of 100 μM NP.

[0032] Figure 6 This is the effect of enrichment time on the response current of 100 μM NP.

[0033] Figure 7 (B) The differential pulse voltammograms of different concentrations of NP on the β-CD / nano-CILPE modified electrode (concentrations from bottom to top are: 0, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 50, 100, 500 μM NP; (B) The linear relationship between NP peak current and concentration.

[0034] Figure 8 The effect of different potential interferents on the response current of 50 μM NP. DETAILED DESCRIPTION

[0035] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The following will further describe the technical solution of the present invention in conjunction with the drawings of the embodiments of the present invention, and the present invention is not limited to the following specific embodiments.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used in the specification herein are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] In one embodiment of the present application, a method for preparing a β-cyclodextrin / ionic liquid composite electrode comprises the following steps:

[0038] The nanographite powder, β-cyclodextrin, ionic liquid and binder are mixed and then fully ground to obtain a paste;

[0039] For example, nano-graphite powder, β-cyclodextrin, ionic liquid and binder are weighed and ground evenly in an agate mortar to obtain a paste.

[0040] The analytical performance of electrochemical sensors is closely related to the properties of the modified materials and the preparation methods of the modified electrodes. Therefore, the synthesis and screening of electrode-modifying materials is a key research area in electrochemistry. Cyclodextrins (CDs) are oligosaccharides composed of six to eight glucose units, primarily including α-CD, β-CD, and γ-CD. The structural complementarity between the hydrophobic interior and the hydrophilic exterior of cyclodextrins is the primary reason for their excellent selectivity for guest molecules. Of the three cyclodextrins, β-CD is often chosen as a modifying material for modified electrodes because of its moderate molecular cavity and relatively better water solubility compared to the other two cyclodextrins. This significantly improves the performance of functional materials, particularly solubility and biocompatibility. Ionic liquids generally refer to specialized molten salts composed of specific anions and cations that are liquid at room temperature or have a low melting point (<100°C). As a new type of polar solvent, ionic liquids are non-flammable, non-volatile, and have good chemical and thermal stability. Therefore, they are favored by researchers in the selection of high-efficiency extractants, catalysts and adhesives, and have broad application prospects in various fields. In the field of electrochemistry, due to its good conductivity and relatively wide electrochemical window, it is a high-performance electrode modification material. Preferably, the ionic liquid is 1-octylpyridinium hexafluorophosphate. The binder is paraffin oil or dimethyl silicone oil, and paraffin oil is preferred in this application. β-cyclodextrin has a unique cyclic hydrophobic cavity structure, which enables β-cyclodextrin and ionic liquids to be effectively combined, so that the composite electrode has excellent selectivity and improved conductivity, can significantly reduce the electrode interface resistance, accelerate the electron transfer rate, thereby enhancing the electrochemical signal, and making the composite modified electrode have better electrochemical performance. Preferably, in the paste, the total amount of the nanographite powder, β-cyclodextrin and ionic liquid added per microliter of binder is 3 to 8 mg.

[0041] Preferably, the mass ratio of the nano-graphite powder to the β-cyclodextrin is (5 to 15): 1. In the present application, β-cyclodextrin is used as a modifier to improve the effective surface area of ​​the modified electrode. Experiments have shown that when the ratio of nano-carbon powder to β-cyclodextrin is 9:1, the response current value of nonylphenol reaches the highest. Therefore, further, the mass ratio of the nano-graphite powder to β-cyclodextrin is 9:1.

[0042] Preferably, the mass ratio of the sum of the mass of the nano-graphite powder and β-cyclodextrin to the ionic liquid is (1 to 3):1. Further, the mass ratio of the sum of the mass of the nano-graphite powder and β-cyclodextrin to the ionic liquid is 2:1.

[0043] The paste is placed in a polytetrafluoroethylene tube and heated to obtain an electrode column. The surface of the electrode column is polished and smooth to obtain a β-cyclodextrin / ionic liquid composite electrode.

[0044] A beta-cyclodextrin / ionic liquid composite electrode is prepared by adopting the above preparation method.

[0045] An electrochemical sensor based on a β-cyclodextrin / ionic liquid composite electrode adopts the above-mentioned β-cyclodextrin / ionic liquid composite electrode as a working electrode.

[0046] A method for detecting nonylphenol comprises the following steps:

[0047] constructing an electrochemical sensor based on the β-cyclodextrin / ionic liquid composite electrode as described above;

[0048] For example, the composite electrode prepared by the above method is used as the working electrode, the reference electrode is a saturated calomel electrode (SCE), and the auxiliary electrode is a platinum wire electrode.

[0049] Constructing an electrolyte system, wherein the electrolyte system consists of a sample solution to be detected and a PBS buffer solution, wherein the concentration of the PBS buffer solution is 0.1 M and the pH is 6 to 9;

[0050] Preferably, a PBS buffer solution with a concentration of 0.1 M and a pH of 6 to 9 is selected as the main electrolyte of the electrolyte system, and then an appropriate amount of the sample solution containing nonylphenol to be tested is added to the PBS buffer solution to obtain the electrolyte system.

[0051] The concentration of nonylphenol was measured.

[0052] Preferably, as in the above-mentioned method for detecting nonylphenol, the concentration of nonylphenol is detected by differential pulse voltammetry, and the concentration is carried out for 60 seconds at open circuit potential.

[0053] Based on the electrochemical sensor and the electrolyte system, differential pulse voltammetry was used at room temperature with a scanning range of -0.2 V to 0.6 V and an open circuit potential accumulation time of 90 s to obtain a voltammogram of nonylphenol. The concentration of nonylphenol was directly obtained based on the linear relationship between the oxidation peak current and the concentration of nonylphenol.

[0054] It is worth noting that the β-CD / nano-CILPE provided by the present invention has good sensitivity, reproducibility, stability and selectivity when applied to the detection of nonylphenol. Under the optimal experimental conditions, the linear range of nonylphenol was 5×10 -9 ~5×10 -4 mol L -1 , the detection limit is 1×10 -9mol L -1 , high detection sensitivity; spike recovery rate is 90.8% to 98.8%; for interfering substances, such as 100 times the Mg 2+ , Ca 2+ 、Na + , K + 、Cu 2+ 、SO4 2- 、Cl - , 10 times the p-nitrophenol (p-NP), hydroquinone (HQ), resorcinol (RES), catechol (CAT) to 5×10 -5 mol L -1 The effect on nonylphenol detection is not significant, indicating that β-CD / nano-CILPE has good selectivity for nonylphenol. The preparation method of the β-cyclodextrin / ionic liquid composite electrode provided by the present invention only requires mixing and grinding nanographite powder, β-cyclodextrin, ionic liquid and binder, and the β-cyclodextrin / ionic liquid composite electrode can be prepared by a combination method. The method is simple and easy to operate. The composite electrode prepared was measured 6 times with the same electrode, and the calculated relative standard deviation (RSD) of the peak current result was 1.41%. The 6 composite electrodes were used to detect nonylphenol at equal concentrations, and the RSD of the peak current was 3.17%, indicating that it has good reproducibility; after storing the modified electrode for one month under dry conditions at room temperature, the same concentration of nonylphenol was measured, and the peak current value was still 99.1% of the initial value, indicating that β-CD / nano-CILPE exhibits excellent stability.

[0055] The following is a detailed experimental procedure to further illustrate the technical solution and technical effects of the present invention.

[0056] 1 Experimental part

[0057] 1.1 Reagents

[0058] Nonylphenol (Rowen, purity 98%), 1-octylpyridinium hexafluorophosphate (Lanzhou Institute of Chemical Physics, purity >99%), nanographite powder (Xianfeng Nanotechnology Co., Ltd., thickness: less than 40 nm, flake diameter: less than 400 nm), paraffin oil (Sigma), β-cyclodextrin, potassium ferrocyanide, potassium ferrocyanide, potassium dihydrogen phosphate, sodium dihydrogen phosphate, p-nitrophenol, hydroquinone, resorcinol, catechol, magnesium chloride, sodium chloride, potassium chloride, copper sulfate, and calcium chloride were purchased from Sinopharm Chemical Reagent Co., Ltd. All were analytical grade and did not require purification prior to use. Ultrapure water was laboratory-prepared.

[0059] 1.2 Instruments

[0060] Table 1 List of instruments used in the experiment

[0061] Instrument type model Manufacturer Electrochemical workstation CHI660E Shanghai Chenhua Instrument Co., Ltd. β-CD / nano-CILPE modified electrode / Prepare it yourself Pt wire electrode CHI115 Shanghai Chenhua Instrument Co., Ltd. Saturated calomel electrode CHI150 Shanghai Chenhua Instrument Co., Ltd. magnetic stirrer KMO2 IKA, Germany Electronic balance instrument AL204 Mettle-Toledo Group

[0062] 1.3 Electrode preparation

[0063] A β-cyclodextrin / ionic liquid composite electrode was prepared using a combinatorial method as follows: 0.045g of nanographite powder, 0.005g of β-cyclodextrin, 0.025g of ionic liquid (1-octylpyridinium hexafluorophosphate), and 15μL of paraffin oil were weighed and ground uniformly in an agate mortar. The thoroughly mixed electrode material was placed in a polytetrafluoroethylene tube and heated with a hair dryer for 1-2 minutes. The electrode surface was then polished smooth on weighing paper to obtain the β-cyclodextrin / ionic liquid composite electrode, labeled β-CD / nano-CILPE.

[0064] To compare the performance of different electrodes, nanocarbon paste electrode (nano-CPE) and β-cyclodextrin-modified nanocarbon paste electrode (β-CD / nano-CPE) were prepared according to the same preparation process as the above method. The difference was that nano-CPE was prepared by grinding 0.05 g nanographite powder and 15 μL paraffin oil; β-CD / nano-CPE was prepared by mixing 0.045 g nanographite powder, 0.005 g β-cyclodextrin and 15 μL paraffin oil.

[0065] 1.4 Analytical methods

[0066] In the electrochemical analysis, a three-electrode system consisting of a saturated calomel electrode (SCE) as the reference electrode, a platinum wire electrode as the auxiliary electrode, and a β-CD / nano-CILPE working electrode was used in a pH 7.0, 0.1 M PBS solution containing nonylphenol. The measurement was performed after a 60-second enrichment time at open circuit potential. The peak current and peak potential on the corresponding DPVs curve were recorded, and the changes in the peak current and potential were discussed and summarized.

[0067] 2 Experimental results and discussion

[0068] 2.1 Electrochemical characterization of modified electrodes

[0069] The electrochemical performance of the modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Figure 1 A and Figure 1B shows the cyclic voltammograms and electrochemical impedance spectroscopy (EIS) of the nanocarbon paste electrode nano-CPE (a), β-cyclodextrin-modified nanocarbon paste electrode β-CD / nano-CPE (b), and β-CD / nano-CILPE (c) in a 5 mM K3[Fe(CN)6] / K4[Fe(CN)6] solution containing 0.1 M KCl. Compared with nano-CPE (curve a) and β-CD / nano-CPE (curve b), the β-CD / nano-CILPE (curve c) exhibits a stronger peak current signal and a smaller peak potential difference. The EIS results show that the semicircle diameter of the β-CD / nano-CILPE (c) impedance spectrum is further reduced, almost forming a straight line. This indicates that the β-cyclodextrin / ionic liquid complex significantly improves the conductivity of the modified electrode, further facilitating electron transfer on the electrode surface.

[0070] 2.2 Surface area study

[0071] The effective surface area of ​​the modified electrode was estimated. Figure 2 The CV graphs of different electrodes at different scan rates in mixed probe solutions are shown in Figure 2. The experimental results show that nano-CPE ( Figure 2 A), β-CD / nano-CPE( Figure 2 B), β-CD / nano-CILPE( Figure 2 C) and the square root of the scan rate (υ 1 / 2 ) have good linearity:

[0072] nano-CPE:I(μA)=166.0721v 1 / 2 (V 1 / 2 s -1 / 2 )+28.8154(r 2 =0.9906);

[0073] β-CD / nano-CPE:I(μA)=235.1537v 1 / 2 (V 1 / 2 s -1 / 2 )+35.7921(r 2 =0.9956);

[0074] β-CD / nano-CILPE:I(μA)=430.1071v 1 / 2 (V 1 / 2 s -1 / 2 )-12.8596(r 2 =0.9969);

[0075] Since the reaction is reversible, its Ipa varies with υ 1 / 2The change satisfies the Randles-Sevcik formula:

[0076] Ipa=(2.69×10 5 )n 3 / 2 AC0D R 1 / 2 υ 1 / 2

[0077] In this formula, the anode peak current is represented by Ipa, the number of electrons participating in the electrode reaction is n, the effective surface area of ​​the electrode is defined as A, and the experimental [Fe(CN)6] 3- / 4- The concentration is C0, and the diffusion coefficient is D R , the scanning rate is υ, in 5mM [Fe(CN)6] 3- / 4- In, D R =6.30×10 -6 cm 2 s -1 The calculated active surface areas of nano-CPE, β-CD / nano-CPE, and β-CD / nano-CILPE are 0.049 cm 2 , 0.070cm 2 and 0.127cm 2 The calculation results of the electrode active surface area show that the effective surface area of ​​β-CD / nano-CILPE is significantly increased, which can provide more binding sites for the analyte and achieve the effect of signal amplification.

[0078] 2.3 Optimization of analytical conditions

[0079] 2.3.1 Effect of different pH values

[0080] Figure 3 The effects of β-CD / nano-CILPE on the peak potential and peak current of nonylphenol in 0.1M PBS at different pH values ​​were discussed. The results showed that the peak current of nonylphenol first increased and then decreased within the pH range of 5-9, with the strongest current signal at pH = 7. The peak potential of nonylphenol shifted negatively with increasing pH, and its linear regression equation was: E(V) = -0.067pH + 1.0076(r 2 =0.9903), the slope is 67.0 mVpH -1 , compared with the theoretically calculated 59.0mV pH -1 The values ​​are relatively close, indicating that the number of protons and electrons involved in the electrode reaction of nonylphenol is consistent.

[0081] 2.3.2 Effect of modifier content

[0082] This paper studies the effect of β-cyclodextrin content (2.5% to 15%) in carbon paste on the response current of nonylphenol. Figure 4 It can be seen that the optimal content ratio of β-cyclodextrin constituting the modified electrode is 10%.

[0083] 2.3.3 Effect of enrichment potential

[0084] Figure 5 The current response changes of 100 μM nonylphenol at different enrichment potentials (-0.1 to 0.4 V) and open circuit potentials are presented. The results show that the maximum response is obtained at 0.2 V under the applied potential conditions. However, there is no significant difference in the current response obtained at open circuit potential and enrichment potential of 0.2 V, and the DPV peak potential is more negative and the peak shape is better. This indicates that the open circuit potential is more conducive to the response of the modified electrode to nonylphenol. Therefore, the open circuit potential was selected for subsequent experiments.

[0085] 2.3.4 Effect of enrichment time

[0086] Figure 6 This study demonstrates the effect of concentration time on the response current of 100 μM nonylphenol. As the concentration time gradually increases from 10 to 60 seconds, the peak current of nonylphenol on the β-CD / nano-CILPE increases. If the concentration time exceeds 60 seconds, the adsorption of nonylphenol on the modified electrode reaches saturation. Considering both sensitivity and detection efficiency for nonylphenol analysis, this application adopted a 60-second concentration time as the optimal experimental condition.

[0087] 2.4 Standard curve

[0088] In this experiment, differential pulse voltammetry was used to detect a series of standard solutions of nonylphenol under the above optimized experimental conditions. The results are as follows: Figure 7 As shown. When the solution concentration is 5×10 -9 ~5×10 -4 mol L -1 The peak current of nonylphenol response was positively linearly correlated with its concentration, and the linear equation was: I (μA) = 0.0923c (μM) + 1.5182 (r 2 =0.9922), the detection limit is 1×10 -9 mol L -1 The results show that the electrochemical sensor constructed in this application has high sensitivity to nonylphenol, which is mainly reflected in its wider linear range and lower detection limit.

[0089] 2.5 Reproducibility and stability

[0090] Six replicate measurements of 150 μM nonylphenol in pH 7.000.1M phosphate buffer using the same β-CD / nano-CILPE were performed, resulting in a calculated relative standard deviation (RSD) of 1.41% for the peak current. Furthermore, six β-CD / nano-CILPE tubes prepared from different batches were used to measure the same concentration of nonylphenol, resulting in an RSD of 3.17%, demonstrating the excellent reproducibility of the composite electrode. After one month of storage at room temperature under dry conditions, the peak current was measured at the same concentration of nonylphenol, retaining 99.1% of the initial value, demonstrating the excellent stability of the β-CD / nano-CILPE.

[0091] 2.6 Interference Study

[0092] The experiment used 0.1M PBS (pH 7.0) as the electrolyte solution, added organic and inorganic interference components that may affect the detection results of nonylphenol, and used 0.1M PBS (pH 7.0) as the test matrix to test the anti-interference ability of β-CD / nano-CILPE. The changes in the peak current response of nonylphenol before and after the addition of interference were observed. The results are shown in Figure 2. Figure 8 As shown. Experiments have found that 100 times the Mg 2+ , Ca 2+ 、Na + , K + 、Cu 2+ 、SO4 2- 、Cl - , 10 times the p-nitrophenol (p-NP), hydroquinone (HQ), resorcinol (RES), catechol (CAT) to 5×10 -5 mol L -1 The effect on nonylphenol detection was not significant, indicating that β-CD / nano-CILPE had good selectivity for nonylphenol.

[0093] 3 Actual sample detection and recovery rate experiment

[0094] To test the ability of β-CD / nano-CILPE to detect real-world samples, we applied this method to water from Yanhu Lake, Ningxia Medical University, Yinchuan, to determine the content of nonylphenol. Water was collected from three different locations in Yanhu Lake and filtered in the laboratory to remove insoluble matter. 1 mL of each water sample was transferred to a volumetric flask and diluted to 10 mL with 0.1 M pH 7.0 PBS. The supernatant was retained for later use. Nonylphenol was determined using the established method, and spike recovery experiments were performed. The results, shown in Table 2, showed spike recoveries ranging from 90.8% to 98.8%, with RSDs less than 5%, demonstrating the suitability of β-CD / nano-CILPE for real-world sample analysis.

[0095] Table 2 Detection results of nonylphenol concentration in samples by β-CD / nano-CILPE (n=3)

[0096]

[0097]

[0098] 4 Conclusion

[0099] This application constructed an electrochemical detection platform for nonylphenol using β-cyclodextrin / ionic liquid composite electrode (β-CD / nano-CILPE) as the sensing interface, compared the electrochemical behaviors of the three modified electrodes, studied the influence of different test conditions on the current peak of nonylphenol, and determined the optimal detection conditions. Compared with nano-CPE and β-CD / nano-CPE, β-CD / nano-CILPE has a larger active surface area, higher electrocatalytic activity and better response intensity for nonylphenol. The results of condition optimization showed that in 0.1MpH=7.0 phosphate buffer, the response current value of nonylphenol was the highest when the open circuit potential and enrichment time were 60s. Under the optimal detection conditions, the linear range of nonylphenol was 5×10 -9 ~5×10 -4 molL -1 , the detection limit is 1×10 -9 mol L -1 Compared with other sensors for detecting nonylphenol, this sensor has a lower detection limit and a wider detection range. In addition, the electrochemical sensor constructed in this paper can be used to detect nonylphenol in actual samples.

[0100] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for preparing a β-cyclodextrin / ionic liquid composite electrode, characterized in that: The following steps are involved: The nanographite powder, β-cyclodextrin, ionic liquid and binder are mixed and then fully ground to obtain a paste; The paste is placed in a polytetrafluoroethylene tube and heated to obtain an electrode column. The surface of the electrode column is polished and smooth to obtain a β-cyclodextrin / ionic liquid composite electrode.

2. The preparation method according to claim 1, wherein In the paste, the total amount of the nano-graphite powder, β-cyclodextrin and ionic liquid added per microliter of binder is 3 to 8 mg.

3. The preparation method according to claim 1, wherein The mass ratio of the nano-graphite powder to the β-cyclodextrin is (5 to 15):

1.

4. The preparation method according to claim 1, wherein The mass ratio of the sum of the mass of the nano-graphite powder and the β-cyclodextrin to the mass of the ionic liquid is (1 to 3):

1.

5. The preparation method according to claim 1, wherein The binder is paraffin oil or dimethyl silicone oil.

6. The preparation method according to claim 1, wherein The ionic liquid is 1-octylpyridinium hexafluorophosphate.

7. A β-cyclodextrin / ionic liquid composite electrode, characterized in that: The method is as described in any one of claims 1 to 6.

8. An electrochemical sensor based on a β-cyclodextrin / ionic liquid composite electrode, characterized in that: The β-cyclodextrin / ionic liquid composite electrode as claimed in claim 7 is used as the working electrode.

9. A method for detecting nonylphenol, characterized in that: The following steps are involved: Constructing an electrochemical sensor based on a β-cyclodextrin / ionic liquid composite electrode as claimed in claim 8; Constructing an electrolyte system, wherein the electrolyte system consists of a sample solution to be detected and a PBS buffer solution, wherein the concentration of the PBS buffer solution is 0.1 M and the pH is 6 to 9; The concentration of nonylphenol was measured.

10. The method for detecting nonylphenol according to claim 9, wherein: The concentration of nonylphenol was detected by differential pulse voltammetry, and the sample was concentrated at open circuit potential for 60 seconds.

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