A ratiometric electrochemical sensor, preparation method and method for simultaneous detection of methyl parathion and carbendazim

Abstract

This invention discloses a ratiometric electrochemical sensor, its preparation method, and a method for simultaneously detecting methyl parathion and carbendazim. The sensor uses a CeCoZn-MOF / NBA / CNHs-modified glassy carbon electrode as the working electrode, a saturated KCl-type Ag / AgCl as the reference electrode, and a platinum wire as the counter electrode. Preparation involves electrode pretreatment, CeCoZn-MOF synthesis, composite material compounding, dispersion preparation, and electrode drop-coating modification. Differential pulse voltammetry is used for detection, with Nile Blue A as the internal standard probe. Quantification is based on the current ratio of the target analyte to the internal standard. The linear detection range for methyl parathion is 0.05–15 μg / mL, and for carbendazim, it is 0.05–4 μg / mL, with correlation coefficients greater than 0.99 for both. This sensor exhibits strong anti-interference capabilities, high sensitivity and accuracy, with a recovery rate of 91.0%–109.2% in actual agricultural product samples. It enables rapid, simultaneous, and accurate detection of methyl parathion and carbendazim, and is suitable for rapid on-site detection of pesticide residues in agricultural products.

Description

Technical Field

[0001] This invention relates to a ratiometric electrochemical sensor, its preparation method, and a method for simultaneously detecting methyl parathion and carbendazim. Background Technology

[0002] Methyl parathion (MP) is a typical nitro-aromatic organophosphate insecticide that kills insects by inhibiting cholinesterase activity and disrupting the nervous system. It is widely used for pest control in fruits and vegetables, significantly improving agricultural productivity. However, long-term exposure to low doses can cause neurological symptoms, gastrointestinal discomfort, and even pose a fatal risk. Carbendazim (CBZ) is a broad-spectrum benzimidazole fungicide commonly used to control fungal diseases in fruits, vegetables, and grains. However, excessive residues can damage the human immune system and liver and kidney function, threatening food safety and human health. In agricultural production, these two fungicides are often used together to enhance efficacy, easily leading to simultaneous residues in agricultural products. Therefore, developing a sensitive, rapid, and reliable method for the simultaneous detection of methyl parathion and carbendazim is of significant practical importance for ensuring food safety and human health.

[0003] Currently, detection techniques for methyl parathion and carbendazim mainly include gas chromatography, high-performance liquid chromatography-mass spectrometry, and surface-enhanced Raman scattering. However, these techniques generally suffer from limitations such as expensive instruments, long detection times, and complex operating procedures, making it difficult to meet the needs of rapid on-site detection. In contrast, electrochemical techniques, with their advantages of low cost, high sensitivity, fast response speed, ease of operation, and miniaturization, have demonstrated excellent analytical performance in the detection of various pesticide residues, becoming a research hotspot in the field of rapid on-site detection.

[0004] Traditional electrochemical sensors typically rely on changes in the response of a single signal output to quantify the content of analytes. However, this single signal is easily affected by factors such as differences in electrode modification methods and fluctuations in environmental conditions (e.g., temperature, pH), leading to subtle differences in the electrode background signal and reducing the accuracy and repeatability of the detection results. This problem is particularly prominent in trace detection and simultaneous detection of multiple components. Unlike traditional sensors that rely on a single signal, ratio sensors possess dual response signals, using the ratio of the two signals as the output. This effectively cancels out the aforementioned interference, significantly improving the reliability and stability of the detection results.

[0005] Currently, research on ratiometric electrochemical sensors capable of simultaneously detecting methyl parathion and carbendazim is still limited. Existing sensors either can only detect a single substance or lack sufficient sensitivity and selectivity, making it difficult to meet the demand for simultaneous detection of trace amounts of both substances in real-world samples. Therefore, developing high-performance ratiometric electrochemical sensors and establishing methods for the simultaneous detection of methyl parathion and carbendazim to overcome the limitations of existing detection technologies has significant research value and application prospects for achieving efficient, accurate, and rapid detection of these two pesticide residues. Summary of the Invention

[0006] The present invention provides a ratiometric electrochemical sensor, a preparation method, and a method for simultaneously detecting methyl parathion and carbendazim in order to solve the problems existing in the prior art.

[0007] The technical solutions adopted in this invention are as follows:

[0008] A ratiometric electrochemical sensor includes a working electrode, a reference electrode, and a counter electrode, characterized in that: the working electrode is a CeCoZn-MOF / NBA / CNHs modified glassy carbon electrode, wherein CeCoZn-MOF is a cerium-cobalt-zinc ternary metal-organic framework, NBA is Nile Blue A, and CNHs are carbon nanoparticles.

[0009] Furthermore, the reference electrode is an Ag / AgCl electrode saturated with KCl, and the counter electrode is a platinum wire electrode.

[0010] Furthermore, in CeCoZn-MOF / NBA / CNHs, the mass ratio of NBA to CNHs is 1:2.

[0011] Furthermore, the surface modification layer of the glassy carbon electrode is formed by drop-coating 4 μL to 8 μL of a CeCoZn-MOF / NBA / CNHs dispersion with a concentration of 0.5 mg / mL to 2 mg / mL and then air-drying it at room temperature.

[0012] This invention also discloses a method for preparing a ratiometric electrochemical sensor, wherein the sensor is the aforementioned ratiometric electrochemical sensor, and the preparation method includes the following steps:

[0013] (1) Polish the glassy carbon electrode with aluminum oxide powder until the surface is smooth, clean it with ethanol and pure water by ultrasonic cleaning, and then air dry it at room temperature to obtain the pretreated glassy carbon electrode.

[0014] (2) Add H3BTC, Ce(NO3)3·6H2O, Co(NO3)2·6H2O and Zn(NO3)2·6H2O to an ethanol-water mixture with a volume ratio of 1:1, disperse by ultrasonication, stir at room temperature, and centrifuge, wash and dry the mixture to obtain CeCoZn-MOF powder.

[0015] (3) Disperse CeCoZn-MOF powder in a 1:1 volume ratio ethanol-water mixed solution, add NBA and CNHs, disperse by ultrasonication and stir at room temperature, centrifuge, wash and dry the mixture to obtain CeCoZn-MOF / NBA / CNHs powder;

[0016] (4) Disperse CeCoZn-MOF / NBA / CNHs powder in pure water to obtain CeCoZn-MOF / NBA / CNHs dispersion;

[0017] (5) The CeCoZn-MOF / NBA / CNHs dispersion was drop-coated onto the surface of the glassy carbon electrode pretreated in step (1) and dried at room temperature to obtain the CeCoZn-MOF / NBA / CNHs modified glassy carbon electrode.

[0018] Further, in step (2), the mass fractions of H3BTC, Ce(NO3)3·6H2O, Co(NO3)2·6H2O and Zn(NO3)2·6H2O are 4.2–16.8 parts, 8.7–34.8 parts, 3.75–15 parts, and 5.95–23.8 parts, respectively.

[0019] Furthermore, in steps (2) and (3), the ultrasonic dispersion time is 5 min to 20 min, the stirring time is 15 min to 60 min, the drying temperature is 60℃, and the drying time is 6 h to 10 h.

[0020] This invention also discloses a method for simultaneously detecting methyl parathion and carbendazim. The method uses the aforementioned ratiometric electrochemical sensor as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum wire as the counter electrode. Differential pulse voltammetry is used to detect the test solution, and the current value I of methyl parathion is measured separately. MP The current value I of carbendazim CBZ The current value I of Nile Blue A NBA , with I MP / I NBA I CBZ / I NBA For quantitative purposes, the concentrations of methyl parathion and carbendazim were calculated using the standard curve method.

[0021] Furthermore, the pH value of the test solution was 5-7, the linear detection range of methyl parathion was 0.05 μg / mL to 15 μg / mL, and the linear detection range of carbendazim was 0.05 μg / mL to 4 μg / mL.

[0022] The present invention has the following beneficial effects:

[0023] (1) In the preparation method of this invention, CeCoZn-MOF (cerium-cobalt-zinc ternary metal-organic framework) is used as a carrier, and CNHs@NBA composite units formed by combining CNHs and NBA are covered on its surface. Through the synergistic effect of physical adsorption and chemical bonding, a stable CeCoZn-MOF / NBA / CNHs composite material is formed, providing a stable internal standard signal for ratiometric sensors, and solving the shortcomings of traditional single-signal sensors that are susceptible to interference and have poor stability. When this composite material is modified on the surface of a glassy carbon electrode, compared with existing single MOF or carbon material modified electrodes, the electrode conductivity and adsorption performance are significantly improved. CeCoZn-MOF has high porosity, large specific surface area and Ce 3+ / Ce 4+ Co 2+ / Co 3+ Zn 2+ The multivalent state transition characteristics of the composite material can serve as a highly efficient electron transfer accelerator, enhancing the adsorption, enrichment, and catalytic capabilities for two pesticides. NBA, as an internally electroactive probe, is adapted to a ratio sensing strategy to counteract various interferences and ensure accurate and reliable detection. CNHs further improve the conductivity and catalytic activity of the composite material, addressing the performance deficiencies of existing MOF-based sensors. Experiments show that this composite material exhibits excellent electrochemical catalytic performance for both methyl parathion and carbendazim, providing a foundation for their simultaneous detection.

[0024] (2) The ratiometric electrochemical sensor of the present invention can simultaneously detect methyl parathion and carbendazim. This sensor has the advantages of fast detection speed, high sensitivity, wide linear range and high accuracy, and excellent anti-interference and repeatability. It has good application prospects in the field of agricultural product quality and safety testing, can meet the needs of rapid and high-precision detection, and solves the problems of complex operation, low efficiency and insufficient accuracy of existing detection methods.

[0025] The ratiometric electrochemical sensor described in this invention can achieve sensitive and simultaneous detection of methyl parathion and carbendazim. The linear detection range of the sensor for methyl parathion is 0.05 to 15 μg / mL, and the linear detection range for carbendazim is 0.05 to 4 μg / mL. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the preparation and detection process of the ratiometric electrochemical sensor of the present invention.

[0027] Figure 2 (A) shows the DPV response curves corresponding to different concentrations of MP and CBZ, where the concentrations of MP are 0.05, 0.5, 2.5, 4, 6, 10, and 15 μg / mL, and the concentrations of CBZ are 0.05, 0.5, 1, 1.5, 2, 3, and 4 μg / mL, respectively; (B) shows the ratio of peak DPV current (I0).MP / I NBA ) and MP concentration (C MP (C) is the standard linear curve between the peak and off-peak currents of the DPV; (I) is the ratio of peak to off-peak current of the DPV. CBZ / I NBA ) and CBZ concentration (C CBZ The standard linear curve between ( ). Detailed Implementation

[0028] The invention will now be further described with reference to the accompanying drawings.

[0029] like Figure 1 As shown, a glassy carbon electrode with a diameter of 3 mm was successively polished with aluminum oxide powder with particle sizes of 0.3 μm and 0.05 μm until the surface was mirror smooth. It was then ultrasonically cleaned in ethanol and pure water to remove surface impurities, and dried at room temperature to obtain a pretreated glassy carbon electrode. A 1:1 volume ratio ethanol-water mixture was prepared, and 60 mL was placed in a reaction vessel. 8.4 mg of triphenylcarboxylic acid (H3BTC), 17.4 mg of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), 7.5 mg of cobalt nitrate hexahydrate (Co(NO3)2·6H2O), and 11.9 mg of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) were added sequentially. The mixture was ultrasonically dispersed for 10 minutes, vigorously stirred at room temperature for 30 minutes, and the mixture was washed three times by centrifugation with ethanol. The resulting solid was dried in a 60℃ oven for 8 hours to obtain CeCoZn-MOF powder.

[0030] CeCoZn-MOF powder was dispersed in 60 mL of ethanol-water mixture with a volume ratio of 1:1. 2 mg of Nile Blue A (NBA) and 4 mg of carbon nanoparticles (CNHs) were added sequentially. The mixture was ultrasonically dispersed for 10 minutes and vigorously stirred at room temperature for 30 minutes. The mixture was washed three times by centrifugation with ethanol. The resulting solid was dried in an oven at 60 °C for 8 hours to obtain CeCoZn-MOF / NBA / CNHs powder.

[0031] 1 mg of the powder was dispersed in 1 mL of pure water to obtain a CeCoZn-MOF / NBA / CNHs dispersion with a concentration of 1 mg / mL. 6 μL of this dispersion was drop-coated onto the surface of a pretreated glassy carbon electrode. After air-drying at room temperature, a CeCoZn-MOF / NBA / CNHs-modified glassy carbon electrode was obtained. Using this electrode as the working electrode, a KCl-saturated Ag / AgCl electrode as the reference electrode, and a platinum wire electrode as the counter electrode, a ratiometric electrochemical sensor was assembled. The preparation and detection procedures for this sensor are detailed in the attached instruction manual. Figure 1 .

[0032] Simultaneous detection of methyl parathion and carbendazim was performed using the aforementioned ratiometric electrochemical sensor. Methyl parathion standard solutions were prepared with PBS buffer at concentrations of 0.05 μg / mL, 0.5 μg / mL, 2.5 μg / mL, 4 μg / mL, 6 μg / mL, 10 μg / mL, and 15 μg / mL, respectively. Differential pulse voltammetry (DPV) was used for detection, and the peak currents of methyl parathion oxidation (IMP) and Nile Blue A oxidation (INBA) were recorded.

[0033] Carbendazim standard solutions were prepared with PBS buffer at concentrations of 0.05 μg / mL, 0.5 μg / mL, 1 μg / mL, 1.5 μg / mL, 2 μg / mL, 3 μg / mL, and 4 μg / mL. The oxidation peak currents of carbendazim (ICBZ) and Nile Blue A (INBA) were detected and recorded using the same method.

[0034] The DPV response curves for different concentrations of methyl parathion and carbendazim are shown in the attached instruction manual. Figure 2 As shown in Figure A, IMP and ICBZ gradually increase with increasing target concentration, while INBA remains basically stable.

[0035] A standard curve was plotted with methyl parathion concentration on the x-axis and IMP / INBA on the y-axis, yielding the linear equation I. MP / I NBA =0.4081C MP -0.0025 (R) 2 =0.994), correlation coefficient R 2 =0.994, see attached instruction manual. Figure 2 For carbendazim B, the linear detection range was 0.05 μg / mL to 15 μg / mL; a standard curve was plotted with carbendazim concentration on the x-axis and ICBZ / INBA on the y-axis, yielding the linear equation I. CBZ / I NBA =2.0784C CBZ +0.0201, correlation coefficient R 2 =0.997, see attached instruction manual. Figure 2 For C, the linear detection range is 0.05 μg / mL to 4 μg / mL.

[0036] In actual sample testing, the pH of the test solution was adjusted to 5-7, and the same three-electrode system and DPV method were used for detection. The concentrations of methyl parathion and carbendazim could be calculated by substituting them into the above linear equation. Cabbage samples were selected for spiked recovery testing. After washing, spiking, drying, and chopping, 10 mL of a 6:4 methanol-water mixture was added, and the mixture was shaken for 2 hours. After centrifugation at 8000 rpm for 10 minutes, the supernatant was filtered through a 0.2 μm filter membrane and diluted 100 times with 0.1 M PBS solution. 5 mL of the supernatant was used for detection. The results are shown in Table 1.

[0037] Table 1: Detection results of MP and CBZ in cabbage samples using the constructed electrochemical sensor

[0038]

[0039] The test results show that the ratiometric electrochemical sensor prepared in this invention has a recovery rate of 91.0% to 109.2% for methyl parathion and carbendazim in cabbage samples, with relative standard deviations of less than 5%. It has good detection accuracy and repeatability, and can achieve sensitive, accurate and simultaneous detection of methyl parathion and carbendazim residues in actual agricultural product samples.

[0040] In other embodiments of the present invention:

[0041] In step (2), the volume ratio of the ethanol-water mixture (1:1) can be adjusted within the range of 30 mL to 90 mL.

[0042] The dosage of benzotricarboxylic acid (H3BTC) can be adjusted within the range of 4.2 mg to 16.8 mg;

[0043] The dosage of cerium nitrate hexahydrate can be adjusted within the range of 8.7 mg to 34.8 mg;

[0044] The dosage of cobalt nitrate hexahydrate can be adjusted within the range of 3.75 mg to 15 mg;

[0045] The dosage of zinc nitrate hexahydrate can be adjusted within the range of 5.95 mg to 23.8 mg;

[0046] The ultrasonic dispersion time can be adjusted within the range of 5 to 20 minutes;

[0047] The stirring time at room temperature can be adjusted within the range of 15 to 60 minutes.

[0048] The drying time can be adjusted within the range of 6 to 10 hours.

[0049] In step (3), the volume ratio of 1:1 ethanol-water mixed solution can be adjusted from 30 mL to 90 mL, and the amount of Nile Blue A can be adjusted from 1 mg to 4 mg.

[0050] The amount of carbon nanoparticles can be adjusted in the range of 2mg to 8mg. The adjustment range of ultrasonic dispersion time, stirring time, drying temperature and drying time is the same as that in step (2).

[0051] The concentration of CeCoZn-MOF / NBA / CNHs dispersion can be adjusted within the range of 0.5 mg / mL to 2 mg / mL;

[0052] The drop volume can be adjusted within the range of 4μL to 8μL. After adjusting the above parameters, the sensor can still achieve simultaneous detection of methyl parathion and carbendazim, while maintaining good sensitivity and stability.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A ratiometric electrochemical sensor, comprising a working electrode, a reference electrode, and a counter electrode, characterized in that: The working electrode is a CeCoZn-MOF / NBA / CNHs modified glassy carbon electrode, where CeCoZn-MOF is a cerium-cobalt-zinc ternary metal-organic framework, NBA is Nile Blue A, and CNHs are carbon nanoparticles.

2. The ratiometric electrochemical sensor as described in claim 1, characterized in that: The reference electrode is an Ag / AgCl electrode saturated with KCl, and the counter electrode is a platinum wire electrode.

3. The ratiometric electrochemical sensor as described in claim 1, characterized in that: In CeCoZn-MOF / NBA / CNHs, the mass ratio of NBA to CNHs is 1:

2.

4. The ratiometric electrochemical sensor as described in claim 1, characterized in that: The surface modification layer of the glassy carbon electrode is formed by drop-coating 4 μL to 8 μL of CeCoZn-MOF / NBA / CNHs dispersion with a concentration of 0.5 mg / mL to 2 mg / mL and then air-drying at room temperature.

5. A method for preparing a ratiometric electrochemical sensor, characterized in that: The sensor is the ratiometric electrochemical sensor according to any one of claims 1-4, and the preparation method includes the following steps: (1) Polish the glassy carbon electrode with aluminum oxide powder until the surface is smooth, clean it with ethanol and pure water by ultrasonic cleaning, and then air dry it at room temperature to obtain the pretreated glassy carbon electrode. (2) Add H3BTC, Ce(NO3)3·6H2O, Co(NO3)2·6H2O and Zn(NO3)2·6H2O to an ethanol-water mixture with a volume ratio of 1:1, disperse by ultrasonication, stir at room temperature, and centrifuge, wash and dry the mixture to obtain CeCoZn-MOF powder. (3) Disperse CeCoZn-MOF powder in a 1:1 volume ratio ethanol-water mixed solution, add NBA and CNHs, disperse by ultrasonication and stir at room temperature, centrifuge, wash and dry the mixture to obtain CeCoZn-MOF / NBA / CNHs powder; (4) Disperse CeCoZn-MOF / NBA / CNHs powder in pure water to obtain CeCoZn-MOF / NBA / CNHs dispersion; (5) The CeCoZn-MOF / NBA / CNHs dispersion was drop-coated onto the surface of the glassy carbon electrode pretreated in step (1) and dried at room temperature to obtain the CeCoZn-MOF / NBA / CNHs modified glassy carbon electrode.

6. The method for preparing the ratiometric electrochemical sensor as described in claim 5, characterized in that: In step (2), the mass fractions of H3BTC, Ce(NO3)3·6H2O, Co(NO3)2·6H2O and Zn(NO3)2·6H2O are 4.2–16.8 parts, 8.7–34.8 parts, 3.75–15 parts, and 5.95–23.8 parts, respectively.

7. The method for preparing the ratiometric electrochemical sensor as described in claim 5, characterized in that: In steps (2) and (3), the ultrasonic dispersion time is 5 min to 20 min, the stirring time is 15 min to 60 min, the drying temperature is 60℃, and the drying time is 6 h to 10 h.

8. A method for simultaneously detecting methyl parathion and carbendazim, characterized in that: Using the ratiometric electrochemical sensor described in any one of claims 1-4 as the working electrode, the Ag / AgCl electrode as the reference electrode, and a platinum wire as the counter electrode, the test solution was detected by differential pulse voltammetry, and the current value I of methyl parathion was measured. MP The current value I of carbendazim CBZ The current value I of Nile Blue A NBA , with I MP / I NBA I CBZ / I NBA For quantitative purposes, the concentrations of methyl parathion and carbendazim were calculated using the standard curve method.

9. The method for simultaneous detection of methyl parathion and carbendazim as described in claim 8, characterized in that: The pH of the test solution was 5-7. The linear detection range of methyl parathion was 0.05 μg / mL to 15 μg / mL, and the linear detection range of carbendazim was 0.05 μg / mL to 4 μg / mL.

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