Visual detection method for mancozeb pesticide residues based on smart phone

Abstract

The invention discloses a visual detection method for mancozeb pesticide residues based on a smart phone, and belongs to the technical field of pesticide residue detection. The preparation method comprises the following specific steps: by taking silver nitrate as a silver source, a high-molecular polymer Tween 80 as a surface stabilizer and a dispersing agent and sodium borohydride as a reducing agent, preparing hydrophilic silver nanoparticles by adopting a room-temperature liquid-phase chemical reduction method; the method comprises the following steps: mixing silver nanoparticles with gelatin to obtain a silver nanoparticle gel patch containing a sensing element point; and dropwise adding a solution containing mancozeb onto the gel patch, and photographing and recording the color change of the gel patch before and after the reaction by using a mobile phone, thereby achieving the visual detection of mancozeb. The mancozeb with different concentrations is detected by adopting a smart phone, and the lowest detection limit of the obtained mancozeb is 3.3 mg / L (GB 20813). The method provided by the invention has the characteristics of high efficiency, economy, sensitive response, strong selectivity and the like, and can realize visual rapid quantitative and qualitative analysis of mancozeb.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural residue detection, and particularly relates to a visual detection method for mancozeb agricultural residues based on a gel patch. Technical Background

[0002] Mancozeb is an excellent organic agricultural fungicide, which has the characteristics of high efficiency, low toxicity, broad spectrum, and slow development of resistance, and is deeply loved by farmers. Mancozeb is fully called "manganese-zinc complex of ethylene bisdithiocarbamate (ethylidene-bis[dithiocarbamic acid] manganese zinc salt)", which is a "surface complex" formed by zinc ions on the surface of mancozeb particles. Non-fully complexed mancozeb contains a large amount of uncomplexed mancozeb, so it will rapidly release excessive manganese ions during the sterilization process, thus causing phytotoxicity to crops. This pesticide is widely used in crops such as fruits, vegetables, and rice, and can prevent various fungal hazards to plant branches and leaves. This pesticide is diluted 500-700 times with a 70% wettable powder into a liquid spray, which can prevent early blight, gray mold, downy mildew, and anthracnose of vegetables. It can also be used to prevent apple scab, rust, and anthracnose of fruit trees.

[0003] At present, for the detection of mancozeb, there are mainly national standard titration methods, capillary electrophoresis methods, gas chromatography methods, spectrophotometry methods, liquid chromatography-mass spectrometry coupling technology, etc. These instrumental analysis methods cannot avoid complex detection steps and sample pretreatment, nor can they perform on-site detection at any time and anywhere, and cannot reflect the situation in a timely manner.

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

[0005] The present invention adopts a room-temperature liquid-phase chemical reduction method, uses silver nitrate as the silver source, Tween 80 as the stabilizer and dispersant, and NaBH 4 as the reducing agent to prepare hydrophilic silver nanoparticles modified with Tween 80, and provides a visual detection method for mancozeb agricultural residues based on a gel patch of a smartphone. Summary of the Invention

[0006] To solve the problems existing in the prior art, the present invention provides a visual detection method for mancozeb based on a silver nanoparticle gel patch integrated with a smartphone, which is based on a Tween 80-modified silver nanoparticle gel patch and integrated with a smartphone for specific recognition and detection of mancozeb. This detection method is low-cost, fast, and sensitive, and can realize on-site visual detection of mancozeb without instruments.

[0007] The detection of mancozeb pesticide by a Tween 80-modified silver nanoparticle gel patch based on a smartphone provided by the present invention. Tween 80 with multiple active groups is used to obtain monodisperse silver nanoparticles. Mancozeb reacts chemically with the modification on the surface of the monodisperse silver nanoparticles, causing the modifier on the nanoparticle surface to fall off, resulting in the aggregation of silver nanoparticles, and thus causing an obvious colorimetric response of the gel patch.

[0008] The present invention is a visual detection method for mancozeb pesticide residues based on a smartphone, which specifically includes the following steps:

[0009] Step 1: Preparation of mercuryophilic silver nanoparticles and construction of the gel patch:

[0010] Under room temperature conditions, silver nitrate is dissolved in 10 mL of ultrapure water and stirred for 15 min. Then, Tween 80 is added to the solution and mixed and stirred for 30 min. Under stirring, 1 mL of fresh reducing agent NaBH 4 aqueous solution is added dropwise, and the reduction is stirred for 3 h. After centrifugation at 5000 r / min for 5 min, the supernatant is extracted to obtain Tween 80-modified mercuryophilic silver nanoparticles. Weigh 0.5 g of gelatin and dissolve it in 4.5 mL of deionized water. Stir it in a constant temperature water bath heater at 80°C for 2 h. Then add 0.5 mL of the silver nanoparticle solution, heat and stir for 5 min, and then pour it into a glass petri dish to cool and form a film to form a gel patch, which is stored at room temperature for later use.

[0011] Step 2: Use a smartphone to take pictures of the gel before and after the reaction and the quantitative detection model M.

[0012] Dissolve mancozeb in ethanol and add ultrapure water to prepare mancozeb aqueous solutions with different concentrations. Use a pipette to respectively pipette mancozeb aqueous solutions with different concentrations and drop them on the gel patch for 5 min of detection reaction. Different concentrations of mancozeb will produce different colorimetric responses with the gel patch. Arrange the gel patch pictures with different colorimetric responses in ascending order of mancozeb concentration corresponding to different concentrations of mancozeb. Use a smartphone to take pictures of the gel patch before and after the colorimetric response, and use the color picker software in the mobile phone to extract the values before the reaction (R 1 , G 1 , B 1), and after (R 2 , G 2 , B 2 ) RGB values, according to the formula , with the ED value as the ordinate and the mancozeb concentration as the abscissa, plot a graph to establish a model M for visual quantitative detection of mancozeb.

[0013] Step 3, Specific detection of mancozeb by silver nanoparticle gel patch.

[0014] The specific detection of mancozeb by the gel patch includes: the effects of interfering metal ions and other potential interfering pesticides on the detection of mancozeb by the silver nanoparticle gel patch based on a smartphone.

[0015] In the said step (1), the concentration range of silver nitrate is 0.01 - 0.1 M, the concentration of Tween 80 is 0.01 - 0.5 M, and the concentration of the reducing agent NaBH 4 aqueous solution is 0.001 - 0.3 M.

[0016] In the said step (2), the concentration range of aqueous solutions of mancozeb at different concentrations is 100 - 1000 mg / L.

[0017] In the said step (3), the interfering metal ions are Al 3+ , Cu 2+ , Mn 2+ , Fe 2+ , Ca 2+ , Mg 2+ , Ag + , Na + , K + , Cd + ; The interfering pesticides are: chlorbenzuron, carbendazim, chlorothalonil, imidacloprid, betanal, methomyl, trichlorfon, vernolate, diflubenzuron.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. The silver nanoparticle gel patch prepared by the present invention has a specific response to mancozeb pesticide and can be used for the identification and detection of mancozeb in complex matrix samples.

[0020] 2. The present invention provides a method for visual detection of mancozeb pesticide by a silver nanoparticle gel patch based on a smartphone. This method is simple to operate, portable, and can achieve on-site detection without instruments. Description of the Drawings

[0021] Figure 1 It is a comparison picture before and after the colorimetric response of the silver nanoparticle gel patch to mancozeb in Example 2.

[0022] Figure 2 Model M - Linear fitting equation graph for quantitative detection of mancozeb by the silver nanoparticle gel patch in Example 2

[0023] Figure 3 Selective detection of mancozeb and metal ions by the silver nanoparticle gel patch in Example 3

[0024] Figure 4 Selective detection of mancozeb and other pesticides by the silver nanoparticle gel patch in Example 4 Detailed implementation manners

[0025] Example 1

[0026] A visual detection method for mancozeb pesticide residues based on a smartphone, comprising the steps of:

[0027] (1) Preparation of mercury - loving silver nanoparticles and construction of the gel patch:

[0028] Under room - temperature conditions, dissolve 0.05 M silver nitrate in 10 ml of ultrapure water, stir for 15 min, then add 0.2 M Tween 80 to the solution and mix and stir for 30 min. While stirring, dropwise add 1 mL of a 0.01 M aqueous solution of the fresh reducing agent NaBH4, and stir and reduce for 3 h to obtain Tween 80 - modified mercury - loving silver nanoparticles. Weigh 0.5 g of gelatin, dissolve it in 4.5 mL of deionized water, and stir in a constant - temperature water - bath heater at 80°C for 2 h. Then add 0.5 mL of the silver nanoparticle solution, heat and stir for 5 min, and then pour it into a glass petri dish to cool and form a film, forming a gel patch, which is stored at room temperature for later use.

[0029] Example 2

[0030] Use a smartphone to take pictures of the gel before and after the reaction and the quantitative detection model M.

[0031] Dissolve mancozeb in ethanol, add ultrapure water to prepare a mancozeb aqueous solution with a concentration range of 100 - 1000 mg / L. Use a pipette to respectively transfer 1 ml of mancozeb aqueous solutions with different concentrations, and drop them onto the silver nanoparticle gel patch respectively, and detect for 5 min. Mancozeb with different concentrations will produce different colorimetric responses with the gel patch. Arrange the gel patch pictures with different colorimetric responses corresponding to different concentrations of mancozeb in ascending order of mancozeb concentration, and establish a picture of the gel patch reaction for detecting mancozeb (Figure 1). Use a smartphone to take pictures of the colorimetric response pictures before and after the reaction, and use the color picker software in the mobile phone to extract the (R 1 G1 , B 1 ), and after (R 2 , G 2 , B 2 ), the RGB values of which are used to plot a graph with the ED value as the ordinate and the mancozeb concentration as the abscissa according to the formula , and a model M - linear fitting equation y = 0.1x + 9.4 ( Figure 2 ) is established, where x is the mancozeb concentration. The LOD of the gas is calculated by the formula LOD = 3δ / K. Among them, K is the slope of the fitting curve, and δ = 0.11 is the standard deviation of the blank sample. As can be seen from Figure 2, the lowest detection limit of mancozeb is 3.30 mg / L (GB20813).

[0032] Example 3

[0033] Selective Detection of Mancozeb and Metal Ions by Silver Nanoparticle Gel Patches

[0034] Prepare an aqueous solution of mancozeb with a concentration of 500 mg / L. Using AlCl 3 , CuCl 2 ·2H 2 O, MnCl 2 , FeSO 4 ·7H 2 O, Ca(OH) 2 , MgCl 2 , AgNO 3 , NaCl, KCl, CdCl 3 as raw materials, prepare 9 aqueous solutions of metal ions with a concentration of 500 mg / L respectively. Use a pipette to separately pipette 1 mL or more of the 10 analyte solutions and drop them on the gel patch respectively, and react for 5 min. Use a smartphone to take pictures to record the colorimetric response pictures before and after the reaction, and use the color picker software in the mobile phone to extract the RGB values before (R 1 , G 1 , B 1 ) and after (R 2 , G 2 , B 2 ), and establish a relationship diagram between the response intensity and the analyte with the response intensity value ED as the ordinate and the analyte type as the abscissa according to the formula . As can be seen from Figure 3 , the sensor has an obvious colorimetric response to mancozeb, while the response to other interfering metal ions is very weak, indicating that the gel patch has excellent selectivity for the detection of mancozeb.

[0035] Example 4

[0036] Selective Detection of Mancozeb and Potential Interfering Pesticides by Silver Nanoparticle Gel Patches

[0037] The pesticides mancozeb, cartap, chlorbenzuron, carbendazim, chlorothalonil, imidacloprid, phenmedipham, methomyl, trichlorfon, EPTC, and diflubenzuron were dissolved in methanol and diluted with ultrapure water to prepare 11 aqueous pesticide solutions with a concentration of 500 mg / L. 1 mL of each of the above 11 analyte solutions was pipetted and dropped onto the gel patch and reacted for 5 min. Colorimetric response pictures before and after the reaction were taken with a smartphone, and the RGB values before (R 1 , G 1 , B 1 ) and after (R 2 , G 2 , B 2 ) were extracted using the color picker software in the mobile phone. According to the formula , with the response intensity value ED value as the ordinate and the analyte type as the abscissa, a relationship graph between the response intensity and the analyte was established. As can be seen from Figure 4 , in the interference samples with other pesticides, the gel patch had an obvious colorimetric response to the detection of mancozeb.

Claims

1. A visual detection method for mancozeb pesticide residues based on a smart phone, characterized in that The specific steps are: (1) Preparation of hydrophilic silver nanoparticles and construction of gel patch: At room temperature, dissolve silver nitrate in 10 mL of ultrapure water, stir for 15 min, and then add Tween 80 was added to the mixture, and the mixture was stirred for 30 min. Under stirring, 1 mL of fresh reducing agent NaBH4 aqueous solution was added dropwise, and the mixture was stirred for reduction for 3 h. The mixture was centrifuged at 5000 r / min for 5 min, and the supernatant was extracted to obtain Tween 80-modified hydrophilic silver nanoparticles. 0.5 g of gelatin was weighed and dissolved in 4.5 mL of deionized water, and stirred in a constant temperature water bath with a heating stirrer at 80°C for 2 h. Then 0.5 mL of silver nanoparticle solution was added, and the mixture was heated and stirred for 5 min. The mixture was then poured into a glass culture dish, cooled to form a film, and a gel patch was formed, which was stored at room temperature for later use. (2) Use a smartphone to take photos of the gel patch before and after the reaction and the quantitative detection model M; Mancozeb was dissolved in ethanol, and ultrapure water was added to prepare mancozeb aqueous solutions of different concentrations. Mancozeb aqueous solutions of different concentrations were respectively transferred with a pipette and dropped onto the silver nanoparticle gel patch, and then allowed to react for 5 minutes. Mancozeb of different concentrations would produce different colorimetric responses with the gel patch. The pictures of the gel patch with different colorimetric responses were matched with mancozeb solutions of different concentrations and arranged in order from small to large mancozeb concentrations. A smartphone was used to take photos of the gel patch before and after the colorimetric response, and the color picker software in the phone was used to extract the RGB values ​​before (R1, G1, B1) and after (R2, G2, B2) the reaction, and the formula was used to calculate the color of the gel patch. , with ED value as the ordinate and mancozeb concentration as the abscissa, a visual quantitative detection model M of mancozeb was established; (3) Specific detection of mancozeb by the gel patch; The specific detection of mancozeb by the gel patch includes the effects of interfering metal ions and other potentially interfering pesticides on the detection of mancozeb by the smartphone-based silver nanoparticle gel patch.

2. According to claim 1, a visual detection method for mancozeb pesticide residues based on a smart phone is characterized in that: In the step (1), the concentration of silver nitrate is in the range of 0.01 to 0.1 M, the concentration of Tween 80 is in the range of 0.01 to 0.5 M, and the concentration of the reducing agent NaBH4 aqueous solution is in the range of 0.001 to 0.3 M.

3. According to claim 1, a visual detection method for mancozeb pesticide residues based on a gel patch, characterized in that: In the step (2), the concentration ranges of the different concentrations of the mancozeb aqueous solution are 100 to 1000 mg / L.

4. According to claim 1, a visual detection method for mancozeb pesticide residues based on a gel patch, characterized in that: In step (3), the interfering metal ion is Al 3+ , Cu 2+ , Mn 2+ , Fe 2+ , Ca 2+ Mg 2+ 、Ag + 、Na + , K + 、Cd + ; The interfering pesticides are: diflubenzuron, carbendazim, thiophanate-methyl, imidacloprid, betaine, cypermethrin, trichlorfon, chlorpyrifos, and diflubenzuron.

5. According to claim 1, a visual detection method for mancozeb pesticide residues based on a gel patch, characterized in that: The minimum detection limit of mancozeb is 3.3 mg / L, which meets the detection requirements of GB 20813.

6. According to claim 1, a visual detection method for mancozeb pesticide residues based on a gel patch, characterized in that: The gel patch showed excellent selectivity for the detection of mancozeb.

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