Paper-based detection method for detecting mancozeb

Abstract

The invention discloses a paper-based detection method for detecting mancozeb, which comprises the following steps: by taking AgNO3 as a silver source, a high-molecular polymer Tween 20 as a surface stabilizer and a dispersing agent and NaBH4 as a reducing agent, preparing hydrophilic silver nanoparticles by adopting a room-temperature liquid-phase chemical reduction method; and printing the silver nanoparticles on filter paper by adopting a pipette to obtain the silver nanoparticle paper-based colorimetric sensor containing a sensing element point. A solution containing mancozeb is dropwise added to the paper-based sensor, and the color of the paper-based sensor changes, so that pesticide detection is achieved. A paper-based sensor is used for detecting mancozeb with different concentrations, a mancozeb standard colorimetric card is manufactured, a quantitative detection model M is established, and the lowest detection limit of mancozeb is 0.076 mu mol / L. The method provided by the invention has the characteristics of low cost, high sensitivity, strong selectivity and the like, and can realize visual rapid quantitative and qualitative analysis of mancozeb.

Description

Technical Field

[0001] The present application relates to a paper-based detection method for detecting mancozeb, belonging to the technical field of analytical chemistry. Background Art

[0002] Mancozeb (complex salt of ethylenebisdithiocarbamoyl manganese and zinc), the industrial product is off-white or light yellow powder, smells like rotten eggs, is insoluble in water, and is a broad-spectrum protective low-toxic fungicide of the thiocarbamate class. It protects plants by providing them with Zn elements. In addition to solving the symptoms of zinc deficiency, it enhances the ability of plants to resist diseases, thereby playing a relatively bactericidal role. Mancozeb is mainly used to prevent and control vegetable downy mildew, anthracnose, brown spot, etc. It is currently an ideal agent for preventing and controlling early blight of tomatoes and late blight of potatoes. Due to its wide range of bactericidal effects and its difficulty in producing resistance, its control effect is significantly better than other similar fungicides, so it has always been a large-tonnage product used internationally. At present, most of the compound fungicides in China are processed and prepared with mancozeb. The residues produced by its large-scale use will inevitably have an adverse impact on the ecological environment, and then pose a threat to human health.

[0003] At present, the main methods for detecting mancozeb include national standard titration method, capillary electrophoresis, gas chromatography, spectrophotometry, liquid chromatography-mass spectrometry, etc. These instrumental analysis methods cannot avoid complicated detection steps and sample pretreatment, and cannot be used for on-site detection anytime and anywhere.

[0004] With the development of chemical sensors, more and more nanomaterial probes are used for the detection of pesticides, such as carbon quantum dot fluorescent probes, surface functionalized precious metal nanoparticle probes, etc. With the continuous improvement of detection conditions, chemical sensors have gradually shifted from aqueous solutions to paper-based ones. Based on the excellent colorimetric sensing performance of silver nanoparticles, they have been widely used in pesticide detection, but most of them are carried out under aqueous solution conditions. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a visual detection method for mancozeb pesticide based on a silver nanoparticle paper-based colorimetric sensor modified with Tween 20 for specific recognition and detection of mancozeb. This detection method is low-cost, rapid, and sensitive, and can realize instrument-free on-site visual detection of mancozeb.

[0006] The detection of mancozeb pesticide by Tween 20-modified silver nanoparticles provided by the present invention utilizes Tween 20 with multiple active groups to obtain monodisperse silver nanoparticles, mancozeb reacts chemically with the surface modification of the monodisperse silver nanoparticles to remove the modifier on the surface of the nanoparticles, resulting in the aggregation of the silver nanoparticles, thereby generating an obvious colorimetric response on a paper substrate.

[0007] The invention adopts a room temperature liquid phase chemical reduction method, uses silver nitrate as a silver source, uses Tween 20 as a stabilizer and dispersant, and uses NaBH4 as a reducing agent to prepare Tween 20-modified hydrophilic silver nanoparticles, and provides a visual detection method for mancozeb pesticide based on a silver nanoparticle paper-based colorimetric sensor.

[0008] According to one aspect of the present application, a paper-based detection method for detecting mancozeb is provided, and the paper-based detection method comprises the following steps:

[0009] (1) stirring a mixture containing Tween 20 and silver nitrate solution, adding NaBH4 solution to the mixture for reduction, and obtaining Tween 20-modified silver nanoparticles;

[0010] (2) immobilizing Tween 20-modified silver nanoparticles on a paper substrate and printing to obtain a paper-based colorimetric sensor;

[0011] (3) dropping mancozeb solutions of different concentrations onto a paper-based colorimetric sensor, observing the colorimetric response, and obtaining a standard colorimetric test paper card for detecting mancozeb;

[0012] (4) Add a solution of mancozeb of unknown concentration onto the paper-based colorimetric sensor, observe the colorimetric response and compare it with the standard colorimetric test paper card for detecting mancozeb to determine the concentration of mancozeb in the mancozeb solution.

[0013] Optionally, in step (1), the concentration of Tween 20 is 0.06-0.08M.

[0014] Optionally, in step (1), the concentration of Tween 20 is selected from any value among 0.06M, 0.065M, 0.07M, 0.075M, 0.08M or a range between any two of the above values.

[0015] Optionally, in step (1), the concentration of the silver nitrate solution is 0.02-0.04M.

[0016] Optionally, in step (1), the concentration of the silver nitrate solution is selected from any value among 0.02M, 0.025M, 0.03M, 0.035M, 0.04M or a range between any two of the above.

[0017] Optionally, the concentration of the NaBH4 solution is 0.01M to 0.03M.

[0018] Optionally, the reduction temperature is 25-28° C., and the reduction time is 3-4 hours.

[0019] Optionally, in step (2), the paper base is selected from at least one of qualitative filter paper, Whatman No. 1 filter paper, and Whatman No. 4 filter paper.

[0020] Optionally, the pore size of the filter paper is 10-12 μm.

[0021] Optionally, the detection limit of the paper-based colorimetric sensor for mancozeb is 0.076-0.080 μmol / L.

[0022] Optionally, the diameter of the sensing element in the paper-based colorimetric sensor is 2.0-3.5 mm.

[0023] Optionally, in step (2), the paper-based colorimetric sensor is stored in an inactive atmosphere.

[0024] Optionally, the inert atmosphere is selected from at least one of nitrogen, helium and argon.

[0025] As a specific implementation, the present application is implemented through the following technical solutions:

[0026] The present invention provides a visual detection method for mancozeb pesticide based on a silver nanoparticle paper-based colorimetric sensor, which specifically comprises the following steps:

[0027] Step 1: Preparation of hydrophilic silver nanoparticles and construction of paper-based colorimetric sensor:

[0028] Under room temperature, silver nitrate was dissolved in 10 ml ultrapure water, stirred for 15 min, and Tween 20 was added to the solution, and mixed and stirred for 30 min. Under stirring, 5 ml of fresh reducing agent NaBH4 aqueous solution was added dropwise, and the mixture was reduced by stirring for 3 h to obtain hydrophilic silver nanoparticles modified with Tween 20. The prepared nanosilver solution was first filtered through filter paper, and the filtrate was centrifuged to remove the supernatant, and finally a dark brown silver nanoparticle solution was obtained. The silver nanoparticle solution was manually transferred using a pipette, fixed on the filter paper, and printed to obtain a paper-based colorimetric sensor. The paper-based sensor was placed in a screw-mouth glass bottle, passed through N2 to isolate oxygen, and stored at room temperature for use.

[0029] Step 2: Prepare a standard colorimetric card and quantitative detection model M for mancozeb.

[0030] Mancozeb was dissolved in ethanol, and ultrapure water was added to prepare different concentrations of mancozeb aqueous solutions. Mancozeb aqueous solutions of different concentrations were pipetted with a pipette and dropped onto the silver nanoparticle paper-based sensor to detect the reaction for 5 minutes. Mancozeb of different concentrations will produce different colorimetric responses with the paper-based sensor. The paper-based sensor images with different colorimetric responses were matched with mancozeb of different concentrations, and arranged in order from small to large mancozeb concentrations to establish a standard colorimetric test paper card for detecting mancozeb. The ΔRGB values ​​of the images before and after the response were extracted, and a model M for quantitative detection of mancozeb was established.

[0031] Step 3: Specific detection of mancozeb by silver nanoparticle paper-based colorimetric sensor.

[0032] The specific detection of mancozeb by paper-based colorimetric sensor includes the influence of interfering metal ions and other potential interfering pesticides on the detection of mancozeb by paper-based colorimetric sensor.

[0033] Optionally, in step 1, the centrifugation parameters are: rotation speed 5000-7000r / min, 5min; the filter paper is: rapid qualitative filter paper with a pore size of 10-12μm; the volume transferred by the pipette is 1-1.5ul, and the diameter of the sensor element is 2-3.5mm; the paper-based sensor is passed through N2 for 1h and placed at room temperature for 12h.

[0034] Optionally, in step 2, the mancozeb aqueous solutions with different concentrations are 0.01 μmol / L, 0.05 μmol / L, 0.10 μmol / L, 0.15 μmol / L, 0.20 μmol / L, 0.25 μmol / L, 0.3 μmol / L, 0.35 μmol / L, and 0.40 μmol / L, respectively; and the volume transferred by the pipette is 1 ul.

[0035] Optionally, in step 3, the interfering metal ion is Al 3+ , Cu 2+ , Mn 2+ , Fe 2+ , Ca 2+ Mg 2+ 、Ag + 、Na + , K + At least one of .

[0036] Optionally, in step 3, the interfering pesticide is at least one of diflubenzuron, carbendazim, thiophanate-methyl, imidacloprid, betaine, methomyl, trichlorfon, chlorpyrifos, and diflubenzuron.

[0037] In the present application, AgNO3 is used as a silver source, high molecular polymer Tween 20 is used as a surface stabilizer and dispersant, and NaBH4 is used as a reducing agent. A room temperature liquid phase chemical reduction method is used to prepare hydrophilic silver nanoparticles; the silver nanoparticles are printed on filter paper using a pipette gun to obtain a silver nanoparticle paper-based colorimetric sensor containing a sensing element. A solution containing mancozeb is dripped onto the paper-based sensor, and the color of the paper-based sensor changes, thereby achieving the detection of pesticides. The paper-based sensor is used to detect mancozeb of different concentrations, a mancozeb standard colorimetric card is prepared, and a quantitative detection model M is established, and the minimum detection limit of mancozeb is obtained to be 0.076 μmol / L.

[0038] The method of the invention has the characteristics of low cost, high sensitivity, strong selectivity, etc., and can realize visual rapid quantitative and qualitative analysis of mancozeb.

[0039] The beneficial effects of this application include:

[0040] 1) The silver nanoparticle paper-based colorimetric sensor provided in the present application has a specific response to the pesticide mancozeb and can be used for the identification and detection of mancozeb in complex matrix samples.

[0041] 2) The present application provides a visual detection method for mancozeb pesticide based on a silver nanoparticle paper-based colorimetric sensor. The method is simple to operate, portable, and can achieve instrument-free on-site detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the silver nanoparticle paper-based colorimetric sensor prepared in Example 1 of the present application.

[0043] Figure 2 This is the standard colorimetric test paper card for detecting mancozeb prepared in Example 2 of the present application.

[0044] Figure 3 This is a diagram of the linear fitting equation of the model M for quantitative detection of mancozeb by the paper-based sensor prepared in Example 2 of the present application.

[0045] Figure 4 This is the selective detection of mancozeb and metal ions by the paper-based sensor prepared in Example 3 of the present application.

[0046] Figure 5 This is the effect of the interfering gas prepared in Example 4 of the present application on the detection of methyl mercaptan gas. DETAILED DESCRIPTION

[0047] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0048] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0049] Example 1

[0050] A visual detection method for mancozeb pesticide based on silver nanoparticle paper-based colorimetric sensor, comprising the steps of:

[0051] Preparation of hydrophilic silver nanoparticles and construction of paper-based colorimetric sensor:

[0052] Under room temperature, dissolve 0.04M silver nitrate in 10ml ultrapure water, stir for 15min, then add 0.08M Tween 20 to the solution and mix and stir for 30min. Under stirring, add 0.01M 5ml fresh reducing agent NaBH4 aqueous solution dropwise, stir and reduce for 3h to obtain Tween 20 modified hydrophilic silver nanoparticles. The prepared nanosilver solution is first filtered through qualitative filter paper, and the filtrate is centrifuged: the speed is 5000-7000r / min, 5min, the supernatant is removed, and finally a dark brown silver nanoparticle solution is obtained. Use a pipette to manually transfer 1ul of silver nanoparticle solution, immobilize it on the filter paper, and print to obtain a silver nanoparticle paper-based colorimetric sensor (such as Figure 1 ), the diameter of the obtained sensing element point is 2-3.5 mm. The paper-based sensor is placed in a screw-mouth glass bottle, N2 is introduced for oxygen isolation for 1 hour, and stored at room temperature for 12 hours for use.

[0053] Example 2

[0054] Mancozeb standard colorimetric card and quantitative detection model M were prepared.

[0055] Mancozeb was dissolved in ethanol, and ultrapure water was added to prepare mancozeb aqueous solutions with concentrations of 0.01 μmol / L, 0.05 μmol / L, 0.10 μmol / L, 0.15 μmol / L, 0.20 μmol / L, 0.25 μmol / L, 0.3 μmol / L, 0.35 μmol / L, and 0.40 μmol / L. 1 ul of mancozeb aqueous solutions of different concentrations were respectively transferred with a pipette and dripped onto the silver nanoparticle paper-based sensor prepared in Example 1, and the reaction was detected for 5 minutes. Mancozeb of different concentrations will produce different colorimetric responses with the silver nanoparticle paper-based sensor. The paper-based sensor spectra with different colorimetric responses were matched with mancozeb of different concentrations, and arranged in order from small to large in terms of mancozeb concentration, to establish a standard colorimetric test paper card for detecting mancozeb (such as Figure 2 ).

[0056] A flatbed scanner was used to extract the spectrum of the silver nanoparticle paper-based sensor before and after the response, and Photoshop was used to extract the ΔRGB value of the image. ΔR is the difference in red color values ​​before and after the response, ΔG is the difference in green color values ​​before and after the response, and ΔB is the difference in blue color values ​​before and after the response.

[0057] The ED value was plotted as the ordinate and the mancozeb concentration as the abscissa, and the model M for quantitative detection of mancozeb was established - the linear fitting equation y = 11.02x + 2.61 (such as Figure 3 ), where x is the concentration of mancozeb. The LOD of the gas is calculated by the formula LOD = 3δ / K. Where K is the slope of the fitting curve, and δ = 0.28 is the standard deviation of the blank sample. Figure 3 It can be seen that the minimum detection limit of mancozeb is 0.076μmol / L.

[0058] Example 3

[0059] Silver nanoparticle paper-based sensor for selective detection of mancozeb and metal ions

[0060] Prepare a 2.5μmol / L mancozeb aqueous solution. Use AlCl3, CuCl2·2H2O, MnCl2, FeSO4·7H2O, Ca(OH)2, MgCl2, AgNO3, NaCl, and KCl as raw materials to prepare 9 kinds of metal ion aqueous solutions with a concentration of 2.5μmol / L. Use a pipette to transfer 1ul of the above 10 analyte solutions respectively, and drop them on the silver nanoparticle paper-based sensor respectively, and react for 5 minutes. Finally, use a flatbed scanner to collect the spectra of the sensor before and after the response to the above 10 analytes, and use the ChemEye older software to extract the colorimetric response intensity ΔRGB value, and use the formula ΔR is the difference in red color values ​​before and after the response, ΔG is the difference in green color values ​​before and after the response, and ΔB is the difference in blue color values ​​before and after the response.

[0061] With the response intensity value ED as the ordinate and the analyte type as the abscissa, a relationship diagram between the response intensity and the analyte is established. Figure 4 It can be seen that the sensor has an obvious response intensity to mancozeb, but the response to other interfering metal ions is very weak, indicating that the paper-based sensor has excellent selectivity for the detection of mancozeb.

[0062] Example 4

[0063] Silver nanoparticle paper-based sensor for selective detection of mancozeb and potential interfering pesticides

[0064] The pesticides mancozeb, cartap, diflubenzuron, carbendazim, chlorothalonil, imidacloprid, betaine, methomyl, trichlorfon, chloranil, and diflubenzuron were dissolved in methanol and diluted with ultrapure water to prepare 11 kinds of pesticide aqueous solutions with a concentration of 2.5μmol / L. 1ul of the above 11 analyte solutions were respectively transferred with a pipette and dropped on the silver nanoparticle paper-based sensor for 5 minutes. Finally, a flatbed scanner was used to collect the spectra of the sensor before and after the response to the above 11 analytes, and the colorimetric response intensity ΔRGB value was extracted by ChemEye older software. The formula ΔR is the difference in red color values ​​before and after the response, ΔG is the difference in green color values ​​before and after the response, and ΔB is the difference in blue color values ​​before and after the response.

[0065] With the response intensity value ED value as the vertical axis and the analyte type as the horizontal axis, a relationship diagram between the response intensity and the analyte is established. Figure 5 It can be seen that in samples with other pesticides as interferences, the paper-based sensor has an obvious response to the detection of mancozeb.

[0066] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A paper-based detection method for detecting mancozeb, characterized in that: The paper-based detection method comprises the following steps: (1) stirring a mixture containing Tween 20 and silver nitrate solution, adding NaBH4 solution to the mixture for reduction, and obtaining Tween 20-modified silver nanoparticles; (2) immobilizing Tween 20-modified silver nanoparticles on a paper substrate and printing to obtain a paper-based colorimetric sensor; (3) dropping mancozeb solutions of different concentrations onto a paper-based colorimetric sensor, observing the colorimetric response, and obtaining a standard colorimetric test paper card for detecting mancozeb; (4) Add a solution of mancozeb of unknown concentration onto the paper-based colorimetric sensor, observe the colorimetric response and compare it with the standard colorimetric test paper card for detecting mancozeb to determine the concentration of mancozeb in the mancozeb solution.

2. The paper-based detection method according to claim 1, characterized in that: In the step (1), the concentration of Tween 20 is 0.06-0.08M.

3. The paper-based detection method according to claim 1, characterized in that: In the step (1), the concentration of the silver nitrate solution is 0.02-0.04M.

4. The paper-based detection method according to claim 1, characterized in that: The concentration of the NaBH4 solution is 0.01 to 0.03 M; Preferably, the reduction temperature is 25-28° C., and the reduction time is 3-4 hours.

5. The paper-based detection method according to claim 1, characterized in that: In the step (2), the paper base is selected from at least one of qualitative filter paper, Whatman No. 1 filter paper, and Whatman No. 4 filter paper.

6. The paper-based detection method according to claim 5, characterized in that: The pore size of the filter paper is 10-12 μm.

7. The paper-based detection method according to claim 1, characterized in that: The detection limit of the paper-based colorimetric sensor for mancozeb is 0.076-0.080 μmol / L.

8. The paper-based detection method according to claim 1, characterized in that: The diameter of the sensing element in the paper-based colorimetric sensor is 2.0-3.5 mm.

9. The paper-based detection method according to claim 1, characterized in that: In the step (2), the paper-based colorimetric sensor is stored in an inactive atmosphere.

10. The paper-based detection method according to claim 9, characterized in that: The inert atmosphere is selected from at least one of nitrogen, helium and argon.

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