Grata-amih electrode modification material and application thereof

Abstract

The application discloses a GR@TA-Ag@MIH electrode modification material and application thereof, tannic acid (TA) is dissolved in deionized water, a Tris solution is added to adjust the pH to 7.5-8.5, and then AgNO3 is added to obtain a TA-Ag solution after stirring; graphene (GR) is dissolved in the TA-Ag solution to form a GR@TA-Ag suspension; the GR@TA-Ag suspension is added into a mixed solution containing acrylamide (AM), ammonium persulfate (APS) and methyl parathion (MP), and is stirred for 5-15 min, and after reaction, washing is performed to obtain the GR@TA-Ag@MIH electrode modification material. The graphene in the GR@TA-Ag@MIH composite material endows the sensor with excellent conductive performance, and the introduced metal ions further improve the conductive characteristics of the composite material, the sensor realizes high specificity identification of methyl parathion, and effectively avoids the interference of compounds similar in structure from generating an oxidation peak at the same potential; a TA-Ag double-catalytic system is constructed, free radicals are rapidly polymerized at room temperature, the self-adhesion of the hydrogel is utilized, and the binding force of the GR@TA-Ag@MIH and the electrode and the adsorption capacity of methyl parathion are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of food safety detection, in particular to a GR@TA-Ag@MIH electrode modification material and application thereof. BACKGROUND

[0002] Methyl parathion (MP) is an organic compound with the chemical formula C8H 10 NO5PS, which is a highly toxic, efficient and broad-spectrum organophosphorus insecticide. Methyl parathion (MP) has a series of advantages such as high efficiency, broad spectrum, small dosage, multiple action modes, convenience of use and short half-life, and has been widely used in agricultural production. It plays an important role in the prevention and control of various pests on many crops. However, methyl parathion degrades slowly in the natural environment, and a large amount of residues will cause serious pollution and harm to the ecological environment. Moreover, methyl parathion can be enriched in the human body through the food chain, and then cause various diseases, endangering human physiological health. Therefore, methyl parathion is banned in many countries, and is strictly regulated in the import and export trade of agricultural products and the safety management of food. Therefore, it is crucial to develop a rapid detection method for methyl parathion.

[0003] At present, the traditional methods for separating, analyzing and detecting methyl parathion reported in the literature mainly include chromatography, chromatography combined with mass spectrometry for qualitative and quantitative detection. However, the above-mentioned detection methods use expensive equipment, have long analysis time and require complex sample pretreatment techniques; therefore, it is of great significance to develop a rapid, accurate and sensitive detection method for methyl parathion. As can be seen from the structure of methyl parathion, methyl parathion contains a nitro group, indicating that methyl parathion is an electrochemically active substance, and therefore can be directly determined by electrochemical methods.

[0004] In the literature "Development of a methyl parathion molecularly imprinted electrochemical sensor based on graphene sensitization", Wu Jiawen et al. developed a graphene-sensitized molecularly imprinted electrochemical sensor for the detection of organophosphorus pesticide methyl parathion. In the preparation of the molecularly imprinted sensor, the nanomaterial graphene was combined, which effectively improved the analysis performance of the sensor. However, when detecting similar structures such as chlorpyrifos, triazophos, and phoxim, there is also a current response, which will reduce the accuracy of the detection results. Patent CN118746607A discloses a methyl parathion molecularly imprinted photoelectrochemical sensor and a preparation method thereof. The photoelectrochemical sensor includes a reference electrode, a saturated calomel electrode, and a working electrode. The working electrode is a molecularly imprinted electrode, which includes a conductive substrate and a composite material (Bi2WO6 QDs / flower-shaped COF) loaded on the conductive substrate. Bismuth tungstate quantum dots are used to increase the charge conversion capability and improve the separation efficiency of electron-hole pairs in cooperation with flower-shaped COF. However, the synthesis process of the electrode modification material Bi2WO6 QDs / flower-shaped COF is relatively complex and requires high temperature and high pressure reaction. In addition, the selectivity of the material to other structurally similar compounds has not been thoroughly studied. However, the recognition sites of traditional MIPs are not uniformly distributed, and some sites may be deeply buried in the polymer, leading to reduced recognition efficiency. In addition, the molecularly imprinted polymer modified electrochemical sensor is prone to fall off on the electrode surface, has poor mechanical strength, and affects the stability of the sensor, thereby reducing the sensitivity and reproducibility of the molecularly imprinted polymer modified electrochemical sensor for detecting methyl parathion. SUMMARY

[0005] In view of the above prior art, the purpose of the present application is to provide a GR@TA-Ag@MIH electrode modification material and its application.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] In the first aspect of the present application, a GR@TA-Ag@MIH electrode modification material is prepared by the following method:

[0008] (1) Dissolve tannic acid (TA) in deionized water, add Tris solution to adjust the pH to 7.5-8.5, then add AgNO3, and stir to obtain a TA-Ag solution;

[0009] (2) Dissolve graphene (GR) in the TA-Ag solution to form a GR@TA-Ag suspension;

[0010] (3) Add the GR@TA-Ag suspension to a mixed solution containing acrylamide (AM), ammonium persulfate (APS), and methyl parathion (MP), stir for 5-15 min, wash after reaction, and obtain the GR@TA-Ag@MIH electrode modification material.

[0011] Preferably, in step (1), the ratio of the amount of tannic acid and deionized water is (1-3) mg:(0.5-1.5) mL; and the concentration of the Tris solution is 0.8-1.5 M.

[0012] Preferably, in step (1), the mass ratio of AgNO3 and tannic acid is (1-3):(1-3).

[0013] Preferably, in step (2), the ratio of graphene and TA-Ag solution is (3-5) mg:(0.5-1.5) mL.

[0014] Preferably, in step (3), the volume ratio of GR@TA-Ag suspension and mixed solution is (1-3):(1-3).

[0015] Preferably, in step (3), in the mixed solution, the mass percentage of acrylamide is 15-25%; the mass percentage of ammonium persulfate is 0.1-0.3%; and the mass percentage of methyl parathion is 0.002-0.004%.

[0016] Preferably, in step (3), the specific method of washing is as follows:

[0017] First, the methyl parathion is eluted with a mixed solution of methanol and acetic acid, and then the deionized water is used for washing.

[0018] Preferably, in the mixed solution of methanol and acetic acid, the volume ratio of methanol and acetic acid is (7-9):(1-3).

[0019] In a second aspect of the present application, the above-mentioned GR@TA-Ag@MIH electrode modification material is provided for use in the preparation of an electrochemical sensor for detecting methyl parathion.

[0020] In a third aspect of the present application, an electrochemical sensor is provided, wherein a glassy carbon electrode modified with the above-mentioned GR@TA-Ag@MIH electrode modification material is used as a working electrode, a platinum electrode is used as an auxiliary electrode, and a saturated calomel electrode is used as a reference electrode.

[0021] Preferably, the working electrode is prepared by the following method:

[0022] The GR@TA-Ag@MIH electrode modification material is dropped onto the surface of a bare glassy carbon electrode using a syringe, and then dried to obtain a modified GR@TA-Ag@MIH@GCE electrode, which is used as the working electrode.

[0023] In a fourth aspect of the present application, a method for detecting methyl parathion by using the above-mentioned electrochemical sensor is provided, which comprises the following steps:

[0024] (1) the working electrode, the reference electrode and the auxiliary electrode in the electrochemical sensor are made into a three-electrode system, the working electrode is immersed into standard methyl parathion solutions with different concentrations in a potential window of -0.6~0.1V by using differential pulse voltammetry, and the corresponding current value is recorded I P ; the working curve is drawn with the concentration of the methyl parathion standard solution as the abscissa and the current value as the ordinate. I

[0025] (2) the content of methyl parathion in the pretreated sample is detected by using the working curve drawn in step (1).

[0026] Preferably, in step (2), the pretreatment method of the sample is as follows: the sample is repeatedly extracted 2~4 times by vortexing and centrifuging with acetonitrile, the water phase and the organic phase are separated by adding sodium chloride, the extraction liquid is combined and dried by blowing nitrogen, the residue obtained after nitrogen blowing is dissolved in a phosphate buffer solution, and the sample extraction liquid is obtained by filtration.

[0027] More preferably, the ratio of the sample to the amount of acetonitrile added is 1g: (1~5) mL.

[0028] The present application has the following beneficial effects:

[0029] ​(1) The electrode modified by GR@TA-Ag@MIH is used as a working electrode, and an electrochemical sensor capable of sensitive detection of methyl parathion is successfully constructed. In the GR@TA-Ag@MIH composite material, graphene endows the sensor with excellent conductivity, and the introduction of metal ions further improves the conductivity of the composite material. Through the molecular imprinting technology, the sensor realizes high specificity recognition of methyl parathion, effectively avoids the interference of similar compounds with oxidation peaks at the same potential, and significantly improves the accuracy of detection; the electrochemical sensor of the application promotes the rapid polymerization of free radicals by using a dynamic double catalytic system inspired by mussels to form a hydrogel, constructs a TA-Ag double catalytic system, the ortho-benzene diol group on TA can reduce silver ions to silver nano ions, and through the oxidation conversion of silver ions into semiquinone or quinone groups; the corresponding semiquinone or quinone group and silver ion activate APS to generate sulfate radical, thereby accelerating the radical polymerization of acrylamide monomers without external energy input, so that when the GR@TA-Ag suspension is added to a mixed solution containing acrylamide (AM), ammonium persulfate (APS) and methyl parathion (MP), the radical polymerization of acrylamide monomers is promoted, the formation of hydrogel does not require high temperature heating, and the radical polymerization is rapid at room temperature; in combination with the molecular imprinting technology, the hydrogel has the ability of specific recognition, and realizes the specific recognition of methyl parathion; the combination of the hydrogel and the molecular technology solves the problems of poor compatibility, easy falling off, long synthesis time and the like of the existing molecular imprinting sensor; the combination of the above multiple advantages significantly improves the oxidation peak current value of methyl parathion, and endows the sensor with higher sensitivity and stability.

[0030] (2) The electrochemical sensor of the application has a minimum detection limit of 0.1 umol / L for methyl parathion; the MRL value of methyl parathion in the national standard is 0.2 mg / kg, therefore, the method can meet the detection needs, and the electrochemical sensor prepared by the application has low cost, simple pretreatment, high sensitivity, short analysis time and simple experimental operation, and is suitable for rapid detection of methyl parathion in various foods. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 : Surface morphology diagram of the GR@TA-Ag@MIH electrode modification material prepared in Example 1 of the application under different magnifications;

[0032] Figure 2 : A is the CV curve of the GR@TA-Ag@MIH / GCE of the application in 100 uM methyl parathion at different scanning rates; B is the relationship between the peak potential and the logarithm of the scanning rate;

[0033] Figure 3A is the DPV curve of GR@TA-Ag@MIH / GCE in methyl parathion solution with different pH values; B is the relationship between peak potential and different pH values;

[0034] Figure 4 A is the DPV curve of GCE, GR@TA-Ag@MIH / GCE and GR@TA-Ag@NIH / GCE in 100 uM methyl parathion solution;

[0035] Figure 5 A is the DPV curve of GCE, GR@TA-Ag@MIH / GCE and GR@TA-Ag@NIH / GCE in 100 uM methyl parathion solution;

[0036] Figure 6 A is the DPV curve of GCE, GR@TA-Ag@MIH / GCE and GR@TA-Ag@NIH / GCE in 100 uM methyl parathion solution;

[0037] Figure 7 A is the DPV curve of GCE, GR@TA-Ag@MIH / GCE and GR@TA-Ag@NIH / GCE in 100 uM methyl parathion solution; DETAILED DESCRIPTION

[0038] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0039] As described in the background, the conventional methods for the separation, analysis and detection of methyl parathion reported in the literature mainly include chromatography and chromatography-mass spectrometry for qualitative and quantitative detection. However, the above-mentioned detection methods use expensive equipment, take a long time for analysis, and require complex sample pretreatment techniques. Although there are reports of using electrochemical methods to detect methyl parathion in the prior art, the preparation methods of the modification materials of existing photoelectrochemical sensors are complex, and compounds with similar structures can also produce current responses at the same potential, thereby interfering with the detection of methyl parathion, reducing the accuracy and specificity of the detection.

[0040] Therefore, the purpose of the present application is to provide an electrochemical sensor and a detection method thereof capable of sensitive and specific detection of methyl parathion. In order to achieve sensitive and specific detection of methyl parathion, the electrode modified with GR@TA-Ag@MIH is used as the working electrode, and an electrochemical sensor capable of sensitive detection of methyl parathion is constructed.

[0041] The CV curve of the working electrode (GR@TA-Ag@MIH / GCE) of the application at different scan rates in 100 uM methyl parathion and the linear relationship between the peak potential and the logarithm of the scan rate are shown in the following figure. Figure 2 As can be seen in (A), the peak current increases with the increase of the scan rate, and the peak potential moves to the negative potential direction with the increase of the scan rate. Figure 2 The linear equation of the peak potential and the logarithm of the scan rate obtained in (B) is E pc (V)=0.0265logv(Vs -1 )-0.0829. According to Lavirons equation:

[0042] ;

[0043] wherein, A is a constant related to the standard electrode potential; a is the transfer coefficient; n is the number of electron transfer in the diffusion control process; R, T and F are the gas constant, temperature and Faraday constant respectively. The slope of the obtained straight line should be 2.303RT / a nF. The electron transfer number a=0.5, and n is about 4 calculated by the obtained linear equation. Therefore, it can be inferred that the oxidation reaction of methyl parathion is a reaction involving 4 electrons.

[0044] The present application further explores the oxidation mechanism of methyl parathion by investigating the relationship between the peak potential and pH of GR@TA-Ag@MIH / GCE in 100 uM methyl parathion solution prepared at different pH values. Figure 3 (A) is the DPV curve of GR@TA-Ag@MIH / GCE in 100 uM methyl parathion solution prepared at different pH values, and it can be seen from the figure that the peak potential value gradually moves to the negative potential direction with the gradual increase of pH. According to the relationship between the peak potential and pH, the linear relationship between the two is Ep(V)=-0.0631pH+0.2476 (Figure 3 (B)). However, the theoretical value of the slope of the linear relationship between Ep and pH is 59 mV. This result can indicate that the number of protons and electrons involved in the oxidation reaction of methyl parathion is equal. Combined with the previous result that the oxidation reaction of methyl parathion involves 4 electrons, it can be finally inferred that the oxidation reaction of methyl parathion involves 4 electrons and 4 protons.

[0045] Figure 4DPV curves of different modified electrodes in 100 uM methyl parathion solution. As can be seen from the figure, after the GCE surface is modified by GR@TA-Ag@MIH, the oxidation peak current value of methyl parathion increases. Compared with GCE, the peak current value of GR@TA-Ag@MIH increases obviously, and the current value of GR@TA-Ag@MIH is greater than that of Gr / TA-Ag@NIH. The graphene added in the GR@TA-Ag@MIH composite has good conductivity, and the metal ions added at the same time improve the conductivity of the composite; the molecular imprinting can realize the specific recognition of the electrochemical sensor to methyl parathion, and excludes the interference of the compounds with similar structures to methyl parathion at the same potential, thereby improving the accuracy of detection; the TA-Ag double-catalytic system is constructed, so that the formation of the hydrogel does not need high-temperature heating, and the free radicals are rapidly polymerized at room temperature; the self-adhesion of the hydrogel improves the bonding force of GR@TA-Ag@MIH and the electrode, and improves the adsorption capacity of methyl parathion, and the combination of the above multiple advantages significantly improves the oxidation peak current value of methyl parathion, and gives the sensor higher sensitivity and stability. The lowest detection limit of methyl parathion by the method of the application is 0.1 umol / L, and high-sensitivity and specific detection of methyl parathion is realized.

[0046] In order for those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0047] The test materials used in the embodiments of the present application are all conventional test materials in the art and can be purchased through commercial channels.

[0048] The synthesis method of Gr / TA-Ag@NIH / GCE used in the present application is the same as that of GR@TA-Ag@MIH / GCE in Embodiment 1, except that no template molecule methyl parathion is added.

[0049] Embodiment 1: Preparation of GR@TA-Ag@MIH electrode modification material:

[0050] (1) 20 mg tannic acid (TA) was dissolved in 10 mL deionized water, and magnetic stirring was carried out for 15 min, and then Tris solution (1M) was added to adjust the pH value to 8.0, 20 mg AgNO3 was added, and stirring was carried out until uniform, to obtain a TA-Ag solution;

[0051] (2) 40 mg of graphene (GR) was dissolved in 10 mL of TA-Ag solution to form a Gr@TA-Ag suspension.

[0052] (3) 10 mL of the Gr@TA-Ag suspension was added into 10 mL of a mixed solution containing acrylamide (AM), ammonium persulfate (APS) and methyl parathion (MP), in which the mass percentage of acrylamide was 20%, the mass percentage of ammonium persulfate was 0.2%, and the mass percentage of methyl parathion was 0.003%;

[0053] The reaction was allowed to occur by magnetic stirring for 15 min, and after the reaction, the precipitate was eluted with a methanol-acetic acid mixed solution (the volume ratio of methanol to acetic acid was 8:2) until no methyl parathion was present, and then deionized water was used to wash away the methanol-acetic acid mixed solution, thereby obtaining the GR@TA-Ag@MIH electrode modification material.

[0054] Figure 1 The surface morphology of the GR@TA-Ag@MIH electrode modification material prepared in this embodiment 1 is shown in FIG. 1. Figure 1 It can be seen that the cross-linked network structure formed by the multiple non-covalent bonds between the hydrogels and the polymers is connected to each other, indicating that the hydrogel synthesis is successful.

[0055] Embodiment 2: Preparation of a GR@TA-Ag@MIH electrode modification material

[0056] (1) 10 mg of tannic acid (TA) was dissolved in 5 mL of deionized water, and magnetic stirring was performed for 15 min, and then a Tris solution (1 M) was added to adjust the pH value to 8.0, and 10 mg of AgNO3 was added and stirred uniformly to obtain a TA-Ag solution;

[0057] (2) 30 mg of graphene (GR) was dissolved in 5 mL of the TA-Ag solution to form a Gr@TA-Ag suspension.

[0058] (3) 20 mL of the Gr@TA-Ag suspension was added into 10 mL of a mixed solution containing acrylamide (AM), ammonium persulfate (APS) and methyl parathion (MP), in which the mass percentage of acrylamide was 20%, the mass percentage of ammonium persulfate was 0.2%, and the mass percentage of methyl parathion was 0.003%;

[0059] The reaction was allowed to occur by magnetic stirring for 15 min, and after the reaction, the precipitate was eluted with a methanol-acetic acid mixed solution (the volume ratio of methanol to acetic acid was 8:2) until no methyl parathion was present, and then deionized water was used to wash away the methanol-acetic acid mixed solution, thereby obtaining the GR@TA-Ag@MIH electrode modification material.

[0060] Embodiment 3: Preparation of a GR@TA-Ag@MIH electrode modification material

[0061] (1) 30 mg tannic acid (TA) was dissolved in 15 mL deionized water, and magnetic stirring was performed for 15 min, and then Tris solution (1 M) was added to adjust the pH value to 8.0, 30 mg AgNO3 was added, and stirring was performed until uniform, to obtain a TA-Ag solution;

[0062] (2) 50 mg graphene (GR) was dissolved in 15 mL TA-Ag solution to form a Gr@TA-Ag suspension.

[0063] (3) 30 mL Gr@TA-Ag suspension was added to 10 mL mixed solution containing acrylamide (AM), ammonium persulfate (APS) and methyl parathion (MP), and the mass percentage of acrylamide in the mixed solution was 20%; the mass percentage of ammonium persulfate was 0.2%; and the mass percentage of methyl parathion was 0.003%.

[0064] Magnetic stirring was performed for 15 min to allow the reaction to occur, and after the reaction, the precipitate was eluted with a methanol-acetic acid mixed solution (the volume ratio of methanol to acetic acid was 8:2) until no methyl parathion was present, and then deionized water was used to wash away the methanol-acetic acid mixed solution, to obtain the GR@TA-Ag@MIH electrode modification material.

[0065] Test Example 1: TA-Ag nanenzyme activity

[0066] The TA-Ag nanenzyme activity prepared in Example 1 was subjected to TMB colorimetry to confirm the catalase activity of the TA-Ag nanenzyme. The TA-Ag solution prepared in Example 1 is the TA-Ag nanenzyme.

[0067] Test method: 0.1 mM TMB solution was prepared, 200 uL TMB solution was added to 1.5 mL acetic acid-sodium acetate buffer solution (0.2 M, pH=3.6), 100 uL H2O2 was added, and finally 100 uL TA-Ag was added, which caused TMB to change from colorless to blue. The absorbance was measured at 653 nm by ultraviolet-visible spectrophotometry, and the change curve of absorbance at 652 nm with time was drawn, and the measurement was performed every 20 s, and the total reaction time was 200 s. Figure 5

[0068] ​The TA-Ag nanozyme prepared by the application contains a phenol-quinone redox pair on the outer surface, which continuously transfers electrons to peroxide, and the Ag nanoparticles are further activated by the outer layer of quinone to continuously provide electrons to maintain the redox activity of the phenol-quinone pair. In addition, the TA-Ag nanozyme is the premise of constructing the TA-Ag double catalytic system, can effectively catalyze the self-condensation of the hydrogel without external stimulation, the ortho-diphenol group on the TA can reduce the silver ion to silver nano ion, and is oxidized to a semiquinone or quinone group by the silver ion; the corresponding semiquinone or quinone group and silver ion activate APS to generate sulfate free radicals, thereby accelerating the radical polymerization of acrylamide monomers without the need for external introduction of energy, resulting in rapid in-situ gelation of the hydrogel.

[0069] Test Example 2: Detection of methyl parathion by using an electrochemical sensor

[0070] The glassy carbon electrode modified by the GR@TA-Ag@MIH electrode prepared in Example 1 is used as a working electrode, a platinum electrode is used as an auxiliary electrode, and a saturated calomel electrode is used as a reference electrode.

[0071] The working electrode is prepared by the following method:

[0072] 10 μL of the GR@TA-Ag@MIH electrode modified material prepared in Example 1 is dropped on the surface of a bare glassy carbon electrode (the diameter of the glassy carbon electrode is 5 mm) by using a syringe, and is dried at room temperature to obtain a modified GR@TA-Ag@MIH / GCE electrode, which is used as a working electrode.

[0073] Test method:

[0074] (1) The saturated calomel electrode and the platinum electrode of the electrochemical sensor are used as the reference electrode and the auxiliary electrode respectively, and the working electrode constitutes a three-electrode system. The working electrode is immersed in methyl parathion standard solutions with concentrations of 1, 5, 10, 20, 50 and 100 μmol / L respectively within a potential window of -0.6~0.1 V by using a differential pulse voltammetry method, and the corresponding current values are recorded respectively. I P Figure 6 A);

[0075] (2) The concentration of the methyl parathion standard solution is used as the abscissa, and the current value is used as the ordinate to draw a working curve (B). The content of methyl parathion in the sample corresponding to different current values is calculated according to the following formula: Figure 6

[0076] I (μA)=0.0799 C (μM)﹣0.0219;

[0077] ​​(3) Accurately weigh 20 g of cucumber sample, add 40 mL of acetonitrile solution, vortex centrifuge, repeat extraction three times, combine the extract and separate the aqueous phase and organic phase by adding sodium chloride, dry under nitrogen, dissolve the remaining residue with 5 mL of 0.2 mol / L phosphate buffer solution, filter with a 0.22 μm filter membrane to obtain the sample extract;

[0078] (4) Replace the standard solution with the sample extract, repeat step 2, and calculate the concentration of methyl parathion according to the above formula, which is 4.22 x 10 -7 mol / L, and the content of methyl parathion in cucumber is 1.11 mg / L.

[0079] Test Example 3: Specificity test of the electrochemical sensor of the application for detecting methyl parathion:

[0080] To explore the specific recognition ability of GR@TA-Ag@MIH prepared in Example 1 for methyl parathion, three structural analogues of glyphosate, dipterex and acephate with the same concentration as methyl parathion were selected for selective test.

[0081] Test solution:

[0082] 50 μM methyl parathion solution;

[0083] Mixed solution containing glyphosate and methyl parathion, wherein the concentration of glyphosate and methyl parathion is 50 μM;

[0084] Mixed solution containing dipterex and methyl parathion, wherein the concentration of dipterex and methyl parathion is 50 μM;

[0085] Mixed solution containing acephate and methyl parathion, wherein the concentration of acephate and methyl parathion is 50 μM;

[0086] Figure 7 is the peak current value of GR@TA-Ag@MIH / GCE and GR@TA-Ag@NIH / GCE in methyl parathion and three mixed solutions containing methyl parathion and its structural analogues; it is calculated that the imprint factor of GR@TA-Ag@MIH / GCE in 50 μM methyl parathion solution is 2.12, and GR@TA-Ag@MIH / GCE has no electrochemical response to glyphosate, dipterex and acephate, three structural analogues, so in the methyl parathion solution containing glyphosate, dipterex and acephate, the calculated imprint factors are 2.05, 1.71 and 2.14, respectively.

[0087] In the mixed solution, the molecular imprinting is about twice the imprinting factor of the non-molecular imprinting, and the current response value is almost similar, which shows that in the mixed solution of structural analogues, there is almost no current response for molecular imprinting and non-molecular imprinting. The imprinting factor is probably twice, which shows that the imprinting factor in the presence of structural analogues is similar to that in the single methyl parathion solution, so it can be shown that the material has the ability of specific recognition to methyl parathion. It can be seen that GR@TA-Ag@MIH / GCE only has the ability of specific recognition to methyl parathion.

[0088] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A GR@TA-Ag@MIH electrode modification material, characterized in that, Prepared by the following method: (1) Dissolve tannic acid in deionized water, add Tris solution to adjust pH to 7.5-8.5, then add AgNO3, and stir to obtain TA-Ag solution; the mass ratio of AgNO3 to tannic acid is (1-3):(1-3); (2) Dissolve graphene in the TA-Ag solution to form a GR@TA-Ag suspension; the solid-liquid ratio of graphene to TA-Ag solution is (3-5) mg:(0.5-1.5) mL; (3) Add the GR@TA-Ag suspension to a mixed solution containing acrylamide, ammonium persulfate and methyl parathion, stir for 5-15 min, wash after reaction, and obtain a GR@TA-Ag@MIH electrode modification material; the volume ratio of the GR@TA-Ag suspension to the mixed solution is (1-3):(1-3); in the mixed solution, the mass percentage of acrylamide is 15-25%, and the mass percentage of methyl parathion is 0.002-0.004%.

2. The GR@TA-Ag@MIH electrode modification material of claim 1, wherein, In step (1), the addition amount ratio of tannic acid to deionized water is (1-3) mg:(0.5-1.5) mL; the concentration of the Tris solution is 0.8-1.5 M.

3. The GR@TA-Ag@MIH electrode modification material of claim 1, wherein, In step (3), the mass percentage of ammonium persulfate is 0.1-0.3%.

4. Use of the GR@TA-Ag@MIH electrode modification material of any one of claims 1-3 in the preparation of an electrochemical sensor for detecting methyl parathion.

5. An electrochemical sensor, characterized in that, The electrochemical sensor uses a glassy carbon electrode modified by the GR@TA-Ag@MIH electrode modification material of any one of claims 1-3 as a working electrode, uses a platinum electrode as an auxiliary electrode, and uses a saturated calomel electrode as a reference electrode.

6. The electrochemical sensor of claim 5, wherein, The working electrode is prepared by the following method: The GR@TA-Ag@MIH electrode modification material is drop-coated onto the surface of a bare glassy carbon electrode using a syringe, and is allowed to dry to obtain a modified GR@TA-Ag@MIH@GCE electrode, which is the working electrode.

7. A method for detecting methyl parathion using the electrochemical sensor according to claim 5 or 6, characterized in that, Comprising the following steps: (1) The working electrode, reference electrode and auxiliary electrode in the electrochemical sensor form a three-electrode system, and the working electrode is immersed in different concentrations of methyl parathion standard solution in the potential window of-0.6-0.1 V by using differential pulse voltammetry, and the corresponding current value is recorded I P ; the working curve is drawn with the concentration of methyl parathion standard solution as the abscissa and the current value as the ordinate I ; (2) Detect the content of methyl parathion in the pretreated test substance using the working curve drawn in step (1).

8. The method of claim 7, wherein, In step (2), the pretreatment method of the test substance is as follows: the test substance is repeatedly extracted 2-4 times by vortexing and centrifuging with acetonitrile, the water phase and the organic phase are separated by adding sodium chloride, the extraction solutions are combined and blown dry with nitrogen, the residue obtained after nitrogen blowing is dissolved in a phosphate buffer solution, and the sample extract is obtained by filtration.

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