A modified electrode and detection method for carbendazim detection in water environment

Abstract

The invention discloses a modified electrode and a detection method for detecting carbendazim in a water environment, and belongs to the technical field of water quality detection. The invention utilizes the adsorption capacity of β-cyclodextrin (β-CD) and the conductivity and electron transfer capacity of ZnCo-LDHs to construct an electrochemical sensor for detecting CBZ. ZnCo-LDHs / β-CD / GCE was successfully prepared by electropolymerizing β-CD on the surface of GCE and electro-depositing ZnCo-LDHs. The modification of ZnCo-LDHs / β-CD was successfully proved by various characterization methods such as SEM, XPS and FTIR. The electrochemical properties of the electrode were studied by various electrochemical methods such as CV and SWV. Under the optimal experimental conditions, the sensor showed a good linear relationship in the range of 0.005-1 mg / L, with a detection limit as low as 0.35 μg / L, and excellent anti-interference and reproducibility. The method can be successfully applied to the determination of carbendazim in actual water samples.

Description

Technical Field

[0001] The invention relates to the technical field of water body detection, and in particular to a modified electrode for detecting carbendazim in a water environment and a detection method. Background Art

[0002] my country is a major agricultural country and also a major pesticide user. In order to better detect trace pesticides in water environments, it is necessary to establish an efficient, sensitive, and cost-effective detection method. The electrochemical sensor method does not require large equipment, is simple to operate, has a low detection limit, is low in cost, and is highly efficient, sensitive, and easy to miniaturize.

[0003] Carbendazim (CBZ) (methyl-1H-2-benzimidazole carbamate) is a broad-spectrum fungicide used for pest control of fruit and cereal crops. The demand for carbendazim in my country accounts for 10% of the total demand for fungicides and about 3% of the total demand for pesticides. It is one of the few 10,000-ton-level fungicides and is a major pollutant frequently detected in food, soil and water. It enters the aquatic environment through pesticide spraying and water runoff. CBZ is classified as a toxic substance with potential carcinogenicity, and its residues can cause liver disease and chromosomal aberrations, especially in aquatic organisms. Small amounts of CBZ can damage the endocrine system and cause hormonal disorders in the human body. In addition, this substance can affect the function of certain organs and cause serious effects on the reproductive system of male mammals, leading to infertility. The use of carbendazim is increasing, and its severe toxic effects are considered to pose an increasing threat to the ecological balance of the environment, and it also shows long-term environmental persistence. Therefore, environmental monitoring of CBZ is very necessary to prevent its excessive use from causing damage to human health.

[0004] Laboratory-scale and on-site monitoring of carbendazim and its derivatives are mainly carried out by spectroscopic, chromatographic and voltammetric techniques. However, these methods have certain limitations. In contrast, electrochemical methods are mainly used to detect CBZ because of their wide range of advantages such as good selectivity, high sensitivity, low cost and rapidity. However, the performance of electrochemical sensors depends on the choice of materials. Transition metal layered double hydroxides (LDHs) are widely used in supercapacitors due to their wide sources, unique layered structures, excellent theoretical specific charges, multiple oxidation states, easily adjustable chemical compositions and versatility. However, the relatively low electrical conductivity of LDHs often limits their development. It is worth noting that in order to better enhance the conductivity of electrode materials, cobalt ions can be introduced into LDHs, which can be used to oxidize Co in the redox process. 2+Conductive CoOOH is generated. Considering that LDHs have abundant Zn resources and rich oxidation states, the introduction of Zn ions can better improve the electrochemical performance of LDHs. β-CD is a naturally occurring cyclic oligosaccharide composed of seven glucose units, in a ring shape, with a hydrophobic cavity inside and a hydrophilic shell. This special structure enables it to bind molecules of appropriate size to form stable inclusion complexes, and the β-CD modifier can improve the reversibility of the electrode reaction, promote electron transfer, and improve selectivity. The inner cavity of the electropolymerized β-CD is able to accumulate the analyte on the electrode.

[0005] Based on the above content, the present invention proposes a ZnCo-LDHs / β-CD modified electrode and a detection method to complete the detection of carbendazim in water environment. Summary of the invention

[0006] The object of the present invention is to provide a modified electrode and a detection method for detecting carbendazim in a water environment so as to more efficiently and accurately realize the determination of carbendazim in actual water samples.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A modified electrode for detecting carbendazim in a water environment is composed of a glassy carbon electrode and ZnCo-LDHs / β-CD modified on the surface of the glassy carbon electrode.

[0009] Preferably, the modified electrode preparation method is as follows:

[0010] A1. Use aluminum oxide powder of different particle sizes to polish the bare glassy carbon electrode into a mirror surface, then clean the electrode surface. After cleaning, place the glassy carbon electrode under an infrared lamp to dry;

[0011] A2, using the glassy carbon electrode treated in A1 as the working electrode to construct a three-electrode system; then depositing ZnCo-LDHs on the electrode surface by cyclic voltammetry. After the deposition is completed, the residual deposition liquid is washed away with a washing bottle, and then the glassy carbon electrode is placed under an infrared lamp to dry;

[0012] A3. After drying, the three-electrode system constructed in A2 is placed in a β-CD solution for further deposition. β-CD is deposited on the electrode surface by cyclic voltammetry to obtain a ZnCo-LDHs / β-CD modified glassy carbon electrode.

[0013] A method for detecting carbendazim in a water environment, specifically comprising the following steps:

[0014] S1. Weigh Zn(NO3)2·6(H2O), Co(NO3)2·6(H2O) and KNO3 in deionized water to obtain ZnCo-LDHs, which are then bottled for later use. Weigh β-cyclodextrin in a weakly acidic PBS buffer to obtain a β-CD solution.

[0015] S2, polishing the bare glassy carbon electrode on suede with aluminum oxide powder of different particle sizes into a mirror surface, then cleaning the electrode surface with a high-intensity water flow, and drying the glassy carbon electrode under an infrared lamp;

[0016] S3, the glassy carbon electrode treated in S2 is used as a working electrode, and is placed in a solution containing zinc and cobalt together with a counter electrode and a reference electrode to construct a three-electrode system; then ZnCo-LDHs is deposited on the electrode surface in the range of -2 to 2V by cyclic voltammetry. After the deposition is completed, the residual deposition liquid is washed away with a washing bottle, and then the glassy carbon electrode is placed under an infrared lamp to dry;

[0017] S4. After drying, the three-electrode system is placed in a β-CD solution for further deposition, and β-CD is deposited on the electrode surface in the range of -2 to 2 V by cyclic voltammetry to obtain a ZnCo-LDHs / β-CD modified glassy carbon electrode;

[0018] S5, using the ZnCo-LDHs / β-CD modified glassy carbon electrode prepared in S4 as the working electrode of the three-electrode system to prepare a ZnCo-LDHs / β-CD electrochemical sensor;

[0019] S6. Using the ZnCo-LDHs / β-CD electrochemical sensor prepared in S5, the carbendazim in the water body is measured.

[0020] Compared with the prior art, the present invention provides a modified electrode and a detection method for detecting carbendazim in a water environment, which has the following beneficial effects:

[0021] The present invention utilizes the adsorption capacity of β-cyclodextrin (β-CD) and the conductivity and electron transmission capacity of ZnCo-LDHs to construct an electrochemical sensor for detecting carbendazim (CBZ). ZnCo-LDHs / β-CD / GCE was successfully prepared by electropolymerizing β-CD and electrodepositing ZnCo-LDHs on the surface of GCE, and then the modification of ZnCo-LDHs / β-CD was successfully proved by various characterization methods such as SEM, XPS and FTIR. In addition, the present invention also studies the electrochemical properties of the electrode by various electrochemical methods such as CV and SWV. Under the optimal experimental conditions, the sensor prepared by the present invention shows a good linear relationship in the range of 0.005 to 1 mg / L, and the detection limit is as low as 0.35 μg / L, and has excellent anti-interference and reproducibility. The ZnCo-LDHs / β-CD / GCE prepared by this method can be successfully applied to the determination of carbendazim in actual water samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of the preparation of the ZnCo-LDHs / β-CD modified electrode mentioned in Example 1 of the present invention;

[0023] Figure 2 The SEM and EDS images of the modified electrode mentioned in Example 1 of the present invention;

[0024] Figure 3 (A) is the FTIR spectrum of ZnCo-LDHs / β-CD in Example 1 of the present invention; Figure 3 (B) is the full spectrum of ZnCo-LDHs / β-CD; Figure 3 (β)~(F) are high-resolution spectra of C1s, O1s, Zn2p, and Co2p, respectively;

[0025] Figure 4 (A) is the CV graph of different electrodes in Example 1 of the present invention in 5 mM K3[Fe(CN)6] and 0.1 M KCl probes; Figure 4 (B) EIS graphs of different electrodes in 5 mM K3[Fe(CN)6] and 0.1 M KCl; Figure 4 (C) shows the detection of CBZ by ZnCo-LDHs / β-CD / GCE in 10 mg / L CBZ using different methods; Figure 4 (D) shows the detection of CBZ with different electrodes and different parameters in 10 mg / L CBZ;

[0026] Figure 5 (A) is the CV response of ZnCo-LDHs / β-CD / GCE in 10 mg / L CBZ at 20-200 mV / s in Example 1 of the present invention; Figure 5 (B) indicates Ipa Linear relationship with scan rate; Figure 5 (C) means I pa Linear relationship with the square root of the scan rate;

[0027] Figure 6 In Example 1 of the present invention, in a medium containing 5 mM K3[Fe(CN)6] and 0.1 M KCl, the scanning speed (20-200 mVs -1 ) The linear relationship between the recorded CV response and the square root of the scan rate and the peak current;

[0028] Figure 7 (A) is the SWV response of ZnCo-LDHs / β-CD / GCE to 0.1 mg / L CBZ in PBS buffer at different pH in Example 1 of the present invention; Figure 7 (B) shows the change of peak current with pH value; Figure 7 (C) shows the change of peak potential with pH value;

[0029] Figure 8 (A) Figure 8 (B) is the response of the ZnCo-LDHs / β-CD / GCE electrode prepared with different concentrations of Zn(NO3)2·6(H2O) in Example 1 of the present invention to CBZ; Figure 8 (C) Figure 8 (D) shows the response of ZnCo-LDHs / β-CD / GCE electrode made with different concentrations of Co(NO3)2·6(H2O) to CBZ; Figure 8 (E) Figure 8 (F) shows the response of ZnCo-LDHs / β-CD / GCE electrodes made of bitter solution with different deposition cycles to CBZ;

[0030] Fig. 9 (A) Fig. 9 (B) is the response of the ZnCo-LDHs / β-CD / GCE electrode prepared with different concentrations of β-CD in Example 1 of the present invention to CBZ; Fig. 9 (C) Fig. 9 (D) shows the response of ZnCo-LDHs / β-CD / GCE electrodes made with different deposition cycles of β-CD to CBZ;

[0031] Fig.10 (A) Fig.10 (B) Fig.10 (C) is the SWV response diagram of ZnCo / GCE, β-CD / GCE, and ZnCo-LDHs / β-CD / GCE electrodes in Example 1 of the present invention at different enrichment times in 10 mg / L CBZ solution; Fig.10(D) Scatter line graph showing time and current values ​​for the three electrodes;

[0032] Fig.11 (A) Fig.11 (B) is the SWV response and linear relationship diagram of ZnCo-LDHs / β-CD / GCE to CBZ solutions of different concentrations in Example 1 of the present invention;

[0033] Fig.12 (A) is the SWV response signal value of ZnCo-LDHs / β-CD / GCE in CBZ solution containing different interfering ions and pesticides in Example 1 of the present invention; Fig.12 (B) shows eight modified electrodes prepared in the same way detecting CBZ solution. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0035] It should be emphasized that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs. Although any methods, devices and materials similar or equivalent to those herein can be used in the practice or testing of the present invention, preferred methods, devices and materials are now described.

[0036] The present invention proposes a modified electrode for detecting carbendazim in a water environment, namely a ZnCo-LDHs / β-CD glassy carbon electrode, and also proposes a method for detecting carbendazim in a water environment using the electrode. The specific embodiments are as follows.

[0037] Embodiment 1:

[0038] A method for detecting carbendazim in a water environment, specifically comprising the following steps:

[0039] (1) Solution preparation: Weigh 0.0149 g Zn(NO3)2·6(H2O), 0.0219 g Co(NO3)2·6(H2O) and 0.1011 g KNO3 in 10 ml deionized water and bottle for later use. Weigh 0.00851 g β-cyclodextrin (β-CD) in 10 ml PBS buffer at pH 6.5.

[0040] (2) Preparation of modified electrodes: The bare glassy carbon electrode was polished to a mirror surface on suede with 300 mm and 50 nm aluminum oxide powder, respectively, and then the electrode surface was cleaned with a high-intensity water flow. Finally, the glassy carbon electrode was placed under an infrared lamp to dry. The glassy carbon, platinum wire (counter electrode) and silver / silver chloride electrode (reference electrode) were placed in a solution containing zinc and cobalt, and ZnCo-LDHs were deposited on the electrode surface by cyclic voltammetry in the range of -2 to 2 V for 5 cycles. After the deposition was completed, the residual deposition liquid was rinsed with a washing bottle, and the glassy carbon electrode was placed under an infrared lamp to dry; after drying, the three-electrode system was placed in a β-CD solution for further deposition, and β-CD was deposited on the electrode surface by cyclic voltammetry in the range of -2 to 2 V for 3 cycles.

[0041] (2) Electrochemical detection: The modified ZnCo-LDHs / β-CD electrode is used as the working electrode to construct a three-electrode electrochemical sensor, which is then connected to an electrochemical workstation for electrochemical detection. The working electrode reacts with the substance to be tested to generate a sensing signal, which is then converted into a recognizable electrical signal proportional to the concentration of the target substance by the electrochemical workstation and displayed on a computer, thereby achieving qualitative or quantitative analysis and detection of the target substance. The preparation and detection process is as follows: Figure 1 The specific contents are as follows:

[0042] 2.1) Material characterization

[0043] SEM scans the surface of a sample by focusing an electron beam to produce an image of the sample surface, which can intuitively show the morphology, size and distribution of the sample; EDS refers to the surface distribution diagram of the energy spectrum, which is used to provide information on the distribution of elements in the sample. Figure 2 ,like Figure 2 As shown, it shows the scanning electron microscope (SEM) image of ZnCo-LDHs / β-CD / GCE. Through the SEM image, it can be observed that β-CD is like a thin film covering the surface of GCE, and ZnCo-LDHs presents a porous mesh structure. It can be seen that the surface of ZnCo-LDHs is covered with a thin film. This porous mesh structure can provide more electroactive sites and provide better detection performance for the detection of carbendazim. Through the energy dispersive spectrometer (EDS), it can be seen that C, O, Zn and Co are all detected in the material, among which carbon is densely distributed and accounts for the highest weight percentage. This is mainly due to two reasons. One is that the base is a glassy carbon sheet, which is rich in carbon elements; the other is that β-CD is rich in carbon elements. Among them, C and O belong to β-CD materials, O, Zn and Co belong to ZnCo-LDHs materials, and the distribution of the three elements is relatively uniform. EDS can prove that the electrode ZnCo-LDHs / β-CD composite material is successfully modified.

[0044] In order to gain a deeper understanding of the structure and bonding of the prepared ZrP / PEDOT materials, Fourier transform infrared (FTIR) measurements were performed on the prepared materials. Figure 3 ,like Figure 3 (A) 480.47 and 525.99cm -1 The peak at 1333.53 cm corresponds to the stretching vibration of MO (M = Co and Zn). -1 The peaks may be related to the nitrate ions inserted and captured in the metal hydroxide structure; the typical characteristic peaks of β-CD are 572.16 cm -1 The ring vibration peak at 1019.68cm -1 The peak at 1151.77 cm represents CO / CC stretching vibration. -1 COC stretching / OH bending vibrations at 1413.08, 2923.55, and 3279.36 cm -1 The peaks at represent the CH / OH bending vibration, CH2 stretching vibration and OH stretching vibration peaks respectively.

[0045] Figure 3 The survey spectrum in (B) is the full spectrum of ZnCo-LDHs / β-CD. It can be seen from the figure that ZnCo-LDHs / β-CD contains four elements: C, O, Co and Zn. Figure 3 In the C1s spectrum of (C), CC, CO and C═O bonds were detected at 284.84, 286.30 and 288.21 eV. Figure 3 (D) In ​​the O1s spectrum shown in Figure 5, Mental-O (Mental is Co and Zn), C=O and CO bonds are detected at 530.97, 532.56, and 535.37 eV. In the Zn2p spectrum, Zn2p centered at 1020.88 and 1043.91 eV 3 / 2 and Zn2p 1 / 2 Core energy level. The Co2p spectrum shows Co at 780.30 and 795.21 eV 3+ The peaks at 780.96 and 796.75 eV are Co 2+ There are two satellite peaks at around 801 and 783 eV.

[0046] 2.2) Analysis of electrochemical behavior of CBR on different electrodes

[0047] See also Figure 4 , Figure 4(A) shows the CV images of electrodes modified differently with 5mM K3[Fe(CN)6] and 0.1M KCl as electrochemical redox probes. A lower redox peak current was observed on the bare electrode compared to the modified ZnCo-LDHs / β-CD / GCE composite electrode. The presence of ZnCo-LDHs on the electrode not only increased the redox peak current from 30.81 to 38.65μA, but also reduced its redox peak potential difference (△Ep) from 111mV to 85mV. The electrode conductivity and electrocatalytic ability were effectively improved, which are attributed to the conductivity of ZnCo-LDHs itself and its ability to promote electron transfer. After the addition of β-CD, the ZnCo-LDHs / β-CD composite material modified electrode reduced the redox current by about 1μA, which is mainly attributed to the weak conductivity of β-CD itself. Please also refer to Figure 6 , Figure 6 Each electrode was subjected to a 5 mM K3[Fe(CN)6] and 0.1 M KCl solution by changing the scan rate (20-200 mVs -1 ), the CV curves of the modified electrodes were recorded, and the linear relationship between the redox peak current and the square root of the scan rate (v) was recorded. The square root of the scan rate (v) reveals the mass transfer on the electrode surface that occurs through a diffusion-controlled process. The electroactive surface area (A) of all modified and unmodified electrodes was calculated according to the following formula (1), where i p is the peak current, n is the number of transferred electrons (1), A is the electroactive area, and D is the diffusion coefficient (in 5 mM K3[Fe(CN)6] and 0.1 M KCl, the value is 0.673x10 -5 cm 2 s -1 ), C is the concentration of ions involved in the reaction, and v is the scanning rate. The calculations show that the A (electroactive area) of GCE, β-CD / GCE, ZnCo-LDHs / GCE, and ZnCo-LDHs / β-CD / GCE are 0.0268, 0.0282, 0.0300, and 0.0291 cm, respectively. 2 The electroactive area of ​​the electrode modified by ZnCo-LDHs / β-CD composite material is significantly improved, which is conducive to obtaining better detection effect in the process of detecting CBZ. EIS can effectively characterize the electronic transport performance of surface modified electrodes. Figure 4(B) shows the impedance test diagram of different electrodes in 5mM K3[Fe(CN)6] and 0.1MKCl solution, and the test was fitted by Zview software. The Rct values ​​of GCE, β-CD / GCE, ZnCo-LDHs / GCE, and ZnCo-LDHs / β-CD / GCE (semicircle in the figure) are 585.7, 946.3, 131.8, and 217.9Ω, respectively. The poor conductivity of electropolymerized β-CD hinders the electron transfer process, which can explain that the surface of the ZnCo-LDHs / β-CD / GCE electrode has lower resistance and higher electron transfer ability.

[0048]

[0049] See also Figure 4 (C) shows that ZnCo-LDHs / β-CD / GCE uses different methods to detect CBZ in 10 mg / L CBZ to evaluate the optimal CBR detection method. From the information in the figure, we can know that the LSV detection signal value is 2.28μA, the DPV detection signal value is 8.38μA, and the SWV detection signal value is 10.36μA. It can be seen that the SWV detection method is the best detection method for CBR, and its detection signal value is about 4.54 times that of LSV and about 1.2 times that of DPV. Figure 4(D) shows the CBZ response under different detection parameters of different electrodes. As shown in the figure, the detection signal values ​​of bare electrode, β-CD / GCE, ZnCo-LDHs / GCE, and ZnCo-LDHs / β-CD / GCE are 1.77μA, 14.50μA, 10.36μA, and 20.85μA, respectively; it can be seen that the detection signal of GCE modified by ZnCo-LDHs / β-CD composite material is about 11.8 times that of bare electrode. By enriching more CBZ in the detection of CBZ, the electrode is allowed to stand still in 10mg / L CBZ for 5min so that the electrode surface can absorb more CBZ. The ZnCo-LDHs / β-CD (5min) / GCE in the figure is its detection result, and the detection signal value is 48.45μA (about 27.4 times that of bare electrode). In order to verify the adsorption effect on the electrode surface, after the electrode was enriched for 5 minutes, the electrode was taken out of the test solution, and the residual solution on the electrode surface was washed off with a washing bottle. Then the three electrodes were placed in a PBS buffer without CBZ for detection. The detection results are shown in the figure ZnCo-LDHs / β-CD (S-5min) / GCE. The detection signal value is 39.24μA (22.1 times the bare electrode level). It can be seen that the ZnCo-LDHs / β-CD composite material has adsorbed CBZ in its structure, proving that the ZnCo-LDHs / β-CD composite material does have the ability to adsorb CBZ, mainly because of the cavity structure of β-CD. The inner cavity of the electropolymerized β-CD can accumulate the analyte on the electrode.

[0050] See also Figure 5 ,like Figure 5 As shown in (A), as the scan rate increases, the oxidation peak current (I pa ) also increases accordingly. pa The ratio of the scan rate (v) to the square root of the scan rate (v 1 / 2 ) shows a certain linear relationship. After fitting calculation, the peak current (I pa ) is proportional to the scan rate and the square root of the scan rate. The peak current (I pa ) has a better linear relationship with v, therefore, it is inferred that the redox reaction of CBZ on the electrode surface is mainly controlled by adsorption.

[0051] 2.3) Optimization of experimental conditions of the present invention

[0052] The experimental conditions and parameter settings were optimized to achieve the best performance of ZnCo-LDHs / β-CD / GCE in detecting carbendazim, including important factors such as the deposition concentration of the modified material and the number of deposition cycles. The optimization experiment adopted the controlled variable method. The optimized initial fixed experimental conditions were carried out in a pH = 6.5 phosphate buffer solution (PBS) containing 10 mg / L CBZ. The electrolytes used for the modified materials were a zinc-cobalt electrolyte composed of 0.1M KNO3 and 5.0mM Zn(NO3)2·6(H2O) and 5.0mM Co(NO3)2·6(H2O) and a β-CD electrolyte composed of 0.2M pH = 6.5 PBS and 5mMβ-CD; the number of deposition cycles was 5r; the enrichment time was 300s.

[0053] Under the same conditions, the SWV method was used to detect the effect of pH on the peak potential (E) of CBZ when the ZnCo-LDHs / β-CD / GCE electrode was used to detect CBZ at different pH values. p ) and peak current (I p ). See Figure 7 , Figure 7 (A) SWV response diagram of ZnCo-LDHs / β-CD / GCE to CBZ at 0.1 mg / L CBZ under different pH conditions on ZnCo-LDHs / β-CD electrode. Figure 7 (B) shows I p When the pH value ranges from 4.0 to 6.5, I p As the pH increases, it increases; when the pH value is between 6.5 and 7.5, I p The value of I decreases with the increase of pH value; when the pH value of the solution is 6.5, p Therefore, pH=6.5 is the best experimental condition. Figure 7 (C) shows E p The relationship between the peak potential and the solution pH is that as the pH value of the buffer solution increases, the peak potential gradually decreases. This is because H + Participates in electrode interaction; E p It has a linear relationship with pH, ​​and the linear equation is: E p (V) = -0.0611pH + 1018749 (R 2 =0.998), with a slope of -0.0611, close to the theoretical calculation of -0.0592, indicating that the CBZ oxidation on the ZnO / GCE surface involves an equal number of protons. The peak potential is linearly related to pH, and the absolute value of its slope is approximately equal to the general theoretical value of 0.059 V / pH, indicating that the ZnCo-LDHs / β-CD / GCE surface involves an equal number of proton and electron transfers.

[0054] In the process of electrodeposition of zinc-cobalt oxide, zinc and cobalt are co-deposited together. Here, only one variable is changed to perform the optimization experiment. Figure 8 ,like Figure 8 (A) and Figure 8 As shown in (B), when the concentration of Zn(NO3)2·6(H2O) increased from 2.5μM to 5.0μM, the peak current of CBZ gradually increased; when the concentration of Zn(NO3)2·6(H2O) increased from 5.0μM to 12.5μM, the peak current of CBZ gradually decreased; Figure 8 (C) and Figure 8 As shown in (B), when the concentration of Co(NO3)2·6(H2O) increases from 2.5μM to 7.5μM, the peak current of CBZ gradually increases; when the concentration of Zn(NO3)2·6(H2O) increases from 7.5μM to 12.5μM, the peak current of CBZ gradually decreases. An electrolyte with too high a concentration will result in the formation of an overly thick zinc cobalt oxide film, which will affect the detection of CBZ. Based on the deposition of 5.0μM Zn(NO3)2·6(H2O) and 7.5μM Co(NO3)2·6(H2O), the effect of different deposition cycles on the current signal of CBZ was studied. When the deposition cycle was 5r, the current signal of CBZ was the highest. Therefore, 5.0μM Zn(NO3)2·6(H2O) and 7.5μM Co(NO3)2·6(H2O) were selected as the optimal electrolyte concentrations, and ZnCo-LDHs / β-CD / GCE electrodes were synthesized by electrodeposition at 5r for subsequent experiments. Fig. 9 ,like Fig. 9 As shown in the figure, when the concentration of β-CD increases from 0.5μM to 0.75μM, the peak current of CBZ gradually increases; when the concentration of β-CD increases from 0.75μM to 7.5μM, the peak current of CBZ gradually decreases; this is because β-CD itself has poor conductivity, and excessively high concentrations of β-CD films will lead to weakened electrode conductivity and electron transfer capabilities. Based on the deposition of 0.75μM β-CD, the effect of different deposition cycles on the current signal of CBZ was studied. When the deposition cycle was 3r, the current signal of CBZ was the highest. Therefore, 0.75μM β-CD was selected as the optimal electrolyte concentration, and the ZnCo-LDHs / β-CD / GCE electrode was synthesized by electrodeposition when the electrodeposition cycle was 3r for subsequent experiments.

[0055] The above optimal conditions were used to prepare ZnCo / GCE, β-CD / GCE, and ZnCo-LDHs / β-CD / GCE electrodes to study the effect of different enrichment times on the detection of 10 mg / L CBZ (high concentration was selected mainly to facilitate the exploration of the maximum adsorption time of CBZ on the electrode). Fig.10 ,according to Fig.10It can be seen that the response current value of GCE modified by ZnCo alone to CBZ ranges from 10 to 13.04 μA in 1 to 6 min, and the overall trend is relatively gentle, with no obvious upward trend; the response current value of GCE modified by β-CD alone to CBZ ranges from 15 to 31.74 μA in 1 to 6 min, and the response current value shows an increasing trend in 1 to 5 min, and tends to be gentle after 5 min; the response current value of GCE modified by the composite material ZnCo-LDHs / β-CD ranges from 20.65 to 49.46 μA in 1 to 6 min, and the response current value shows an increasing trend in 1 to 5 min, and tends to be gentle after 5 min, with a very slow growth trend. Considering the time cost, the subsequent experiments take 5 min as the optimal enrichment time. From the above results, it can be seen that GCE modified by ZnCo alone has no obvious adsorption effect on CBZ. On the contrary, whether it is modified by β-CD alone or the composite material ZnCo-LDHs / β-CD co-modified GCE, it shows adsorption effect on CBZ.

[0056] 2.4) Linear range and detection limit

[0057] PBS was used to prepare CBZ stock solution with different concentrations of 0.005, 0.01, 0.15, 0.02, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, and 1 mg / L. In terms of linear detection, the SWV method was used, so the experiment was carried out under the above optimal experimental conditions. SWV parameter settings: scanning range: -0.6~1.0V; 2s rest time, PBS pH 6.5, scanning rate 100mV / s, enrichment time 300s. Please refer to Fig.11 ,like Fig.11 As shown in Figure 2, when CBR is in the concentration range of 0.005-1 mg / L (i.e., 0.0262-5.23 μM / L), the concentration and the peak value of the electrical signal show a good linear relationship, and the linear regression equations of the peak current and the concentration of CBZ are i p (μA)=17.046(mg)-0.030(R 2 =0.992). The detection limit of the sensor was calculated by dividing 3 times the standard deviation of the blank by the slope of the linearity, and the detection limit of the ZnO / GCE electrochemical sensor was calculated to be 0.35 μg / L (i.e., 0.0018 μM / L). The experiment showed that the ZnCo-LDHs / β-CD / GCE sensor can successfully detect CBZ. Compared with similar sensors (as shown in Table 1), the prepared sensor has certain advantages in detection range and detection limit, with a good linear range and a lower detection limit.

[0058] Table 1 Other sensor detection data

[0059]

[0060] 2.5) Anti-interference and stability

[0061] The interference of various ions and some pesticides was explored to better explore the application of the sensor in the actual environment. In the experiment, Ca2+ with a concentration 100 times that of 0.1 mg / L CBZ was selected. 2+ Mg 2+ , Fe 2+ 、CO3 2- 、CH3OOH - 、SO4 2- 、NO2 - 、NO3 - ions, 10 times pesticides include: atrazine, malathion, glyphosate, diazinon, carbaryl as anti-interference substances. Fig.12 ,Depend on Fig.12 (A) It can be seen that the peak current does not change much after adding anti-interference ions compared with the case of pure carbendazim without anti-interference, indicating that the ZnCo-LDHs / β-CD / GCE sensor is not affected by the above interfering substances in the actual water environment. In general, the sensor exhibits good anti-interference performance. At the same time, in order to explore the stability of the ZnCo-LDHs / β-CD / GCE electrode, eight electrodes with the same modification conditions were used to measure the same solution, such as Fig.12 As shown in (B), the standard deviation of eight electrodes was calculated to be 7.7%, indicating good reproducibility.

[0062] 2.6) Application in actual water environment

[0063] In order to optimize the experimental conditions, the prepared electrode was used to detect CBR in actual water samples to verify the practical application ability of the prepared electrode. The prepared electrode was evaluated using the spike method. In order to avoid the influence of insoluble impurities in the water sample on the experimental results, the tap water collected and the river water and groundwater that had been simply filtered were prepared into CBR solutions with concentrations of 50, 75, and 100 μg / L, respectively, and electrochemical detection was performed under the optimal experimental conditions. The results are shown in Table 2. The recovery rate of CBR in tap water samples was 96.28-99.69%, the recovery rate of CBR in groundwater samples was 96.67-98.79%, and the recovery rate of CBR in surface water samples was 94.50-105.22%. The results show that the ZnCo-LDHs / β-CD / GCE electrochemical sensor can be used for the detection of actual water samples.

[0064] Table 2 Detection of ZnCo-LDHs / β-CD / GCE on actual water samples

[0065]

[0066]

[0067] In summary, the present invention prepares ZnCo-LDHs / β-CD modified GCE by a simple electrodeposition method and performs sensitive and selective electrochemical detection of CBZ. The morphological characteristics and elemental valence states of the modified materials are studied by means of SEM, EDS, XPS, FTIR, etc., and it is proved that ZnCo-LDHs / β-CD is successfully prepared, wherein the ZnO porous honeycomb structure. By testing cyclic voltammetry at different scan rates in potassium ferrocyanide, it is concluded that the composite material modification can enhance the electroactive sites on the electrode surface, and the impedance experiment in potassium ferrocyanide solution proves that the ZnCo-LDHs / β-CD / GCE electrode has good electron transfer ability. In order to evaluate the detection performance of the sensor under optimal conditions, the experimental conditions are optimized, including: enrichment time, ZnCo-LDHs and β-CD deposition solution concentrations and deposition cycles, buffer pH and other key experimental factors. Finally, the sensor showed a good linear relationship in the range of 0.005-1 mg / L (i.e. 0.0262-5.23 μM / L), and the detection limit was calculated to be 0.35 μg / L (i.e. 0.0018 μM / L). At the same time, the prepared sensor also showed excellent anti-interference performance and reproducibility, and obtained good results in the actual water sample spike test.

[0068] Combined with the data of the above examples, it can be seen that the present invention proposes an electrochemical sensor for detecting carbendazim modified by electrodeposition of ZnCo-LDHs and electropolymerization of β-CD, wherein the morphology of β-CD is a smooth and uniform film, and ZnCo-LDHs presents a porous network structure. Characterization means prove that the ZnCo-LDHs / β-CD modification is successful. The modification of ZnCo-LDHs / β-CD increases the active area of ​​the electrode by 0.0023 cm 2 , the electrode resistance was reduced by 367.8Ω, and the electrode electron transfer capacity was improved. Under the conditions of electrodeposition 5r (7.5mM Zn(NO3)2·6(H2O and 5.0mM Co(NO3)2·6(H2O)) and electropolymerization 3r (0.75mMβ-CD), the sensor showed a good linear relationship in the range of 0.005-1mg / L (i.e.: 0.0262-5.23μM / L), and the detection limit was 0.35μg / L (i.e.: 0.0018μM / L). 2+ , Fe 2+Plasma, atrazine, malathion, glyphosate, diazinon, and carbaryl pesticides still have good detection performance under the premise of anti-interference substances. Eight electrodes were prepared under the same conditions to test the same solution. The standard deviation of the eight electrodes was 7.7%, and the reproducibility was good. This method was applied to the determination of carbendazim in actual samples. The recovery rate of CBR in tap water samples was 96.28-99.69%, the recovery rate of CBR in groundwater samples was 96.67-98.79%, and the recovery rate of CBR in surface water samples was 94.50-105.22%. The bimetallic composite β-CD modified electrode developed in this study provides a novel solution for the efficient, portable, and in-situ detection of carbendazim in real water environments.

[0069] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for detecting carbendazim in a water environment, characterized in that: The specific steps include: S1. Weigh Zn(NO3)2·6(H2O), Co(NO3)2·6(H2O) and KNO3 in deionized water to obtain ZnCo-LDHs, which are bottled for later use; weigh β-CD in a weakly acidic PBS buffer to obtain a β-CD solution; S2, polishing the bare glassy carbon electrode on suede with aluminum oxide powder of different particle sizes into a mirror surface, then cleaning the electrode surface with a high-intensity water flow, and drying the glassy carbon electrode under an infrared lamp; S3, the glassy carbon electrode treated in S2 is used as the working electrode, and is placed in a solution containing zinc and cobalt together with the counter electrode and the reference electrode to construct a three-electrode system; then ZnCo-LDHs is deposited on the electrode surface in the range of -2 to 2 V by cyclic voltammetry. After the deposition is completed, the residual deposition liquid is washed away with a washing bottle, and then the glassy carbon electrode is placed under an infrared lamp to dry; S4. After drying, the three-electrode system is placed in a β-CD solution for further deposition, and β-CD is deposited on the electrode surface in the range of -2 to 2 V by cyclic voltammetry to obtain a ZnCo-LDHs / β-CD modified glassy carbon electrode; S5, using the ZnCo-LDHs / β-CD modified glassy carbon electrode prepared in S4 as the working electrode of the three-electrode system to prepare a ZnCo-LDHs / β-CD electrochemical sensor; S6, using the ZnCo-LDHs / β-CD electrochemical sensor prepared in S5 to measure the carbendazim in the water body to be tested; The detection method is implemented based on a modified electrode for detecting carbendazim in a water environment. The modified electrode is composed of a glassy carbon electrode and ZnCo-LDHs / β-CD modified on the surface of the glassy carbon electrode.

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