Method for enriching and detecting pesticide based on garlic straw magnetic biochar

Abstract

The invention relates to the technical field of pesticide analysis and detection, in particular to a method for enriching and detecting pesticide based on garlic straw magnetic biochar. The preparation method comprises the following steps: by taking garlic straw as a carbon source, activating, calcining and carbonizing, and then mixing and reacting with a trivalent ferric salt solution and a divalent ferric salt solution to obtain the garlic straw magnetic biochar. The garlic straw magnetic biochar has a large number of pore structures, a high specific surface area, rich oxygen-containing functional groups and excellent magnetism, and has a good adsorption effect on neonicotinoid and methoxy acrylate pesticides. The garlic straw magnetic biochar is used for magnetic solid-phase extraction detection of neonicotinoid and methoxyl acrylate pesticides in an environmental water sample, and the detection recovery rate and precision are good.

Description

Technical Field

[0001] The invention relates to the technical field of pesticide analysis and detection, and in particular to a method for enriching and detecting pesticides based on magnetic biochar from garlic straws. Background Art

[0002] Pesticides, as an important agricultural chemical, are widely used to improve crop yield and quality. As a representative class of insecticides, neonicotinoids (NEOs) are widely used in more than 120 countries, accounting for about 25% of the global insecticide market, because they have a broad spectrum of effects in controlling agricultural pests. Neonicotinoids have high water solubility, good fluidity and a relatively long half-life, so they will remain in the environment, threatening the behavior of aquatic insects, the survival of bees, and even human health.

[0003] Strobilurin fungicides (SFs) are a relatively new class of agrochemicals. Orysastrobin, as a typical SFs, has been successfully used to control rice leaf blight, panicle blast and sheath blight. Considering the persistence of orysastrobin in water and its mobility in soil, orysastrobin tends to accumulate in aquatic environments. Studies have shown that high average concentrations of orysastrobin are often detected in wetlands, and it is significantly toxic to amphibians, aquatic organisms and soil animals. In order to reduce the level of pesticide residues and protect the health of humans and other organisms, many countries and organizations have set maximum residue limits for neonicotinoid insecticides and orysastrobin, ranging from 0.01 mg kg -1 to 10 mg kg -1 Therefore, it is particularly important to develop effective extraction, enrichment and pretreatment and detection methods for neonicotinoid pesticides and orysastrobin in trace amounts in environmental water samples. Summary of the invention

[0004] Based on the above content, the present invention provides a method for enriching and detecting pesticides based on garlic straw magnetic biochar. The garlic straw magnetic biochar of the present invention has a developed pore structure, a large specific surface area, rich oxygen-containing functional groups, excellent magnetic properties, and a high adsorption rate for neonicotinoids and strobilurin pesticides.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The first aspect of the present invention provides a method for preparing magnetic biochar from garlic straw, comprising the following steps:

[0007] The garlic straw is placed in an alkaline solution for activation, and then calcined and carbonized to obtain garlic straw biochar;

[0008] The garlic straw biochar is dispersed in a mixed solvent of water and ethanol, and then a trivalent iron salt solution is first added, and then a divalent iron salt solution and an alkaline precipitant are added to react to obtain the garlic straw magnetic biochar.

[0009] A second aspect of the present invention provides a garlic straw magnetic biochar prepared according to the above-mentioned preparation method.

[0010] A third aspect of the present invention provides an application of the above-mentioned garlic straw magnetic biochar in the enrichment and detection of neonicotinoid insecticides or strobilurin fungicides.

[0011] The fourth aspect of the present invention provides a method for enriching and detecting pesticides based on the above-mentioned garlic straw magnetic biochar, wherein the garlic straw magnetic biochar is placed in a water sample for mixing and oscillation (to enrich the pesticides in the garlic straw magnetic biochar), the garlic straw magnetic biochar in the water sample is separated by a magnet and then placed in an acetone solution for desorption to obtain an eluent; the eluent is filtered and then subjected to high performance liquid chromatography analysis and detection, and the pesticide content is calculated according to a standard curve;

[0012] The pesticide is acetamiprid, imidacloprid, thiacloprid or orysastrobin.

[0013] The present invention discloses the following technical effects:

[0014] The invention adopts garlic straw as raw material, obtains biochar through activation and calcination, and magnetizes the biochar through in-situ polymerization. The prepared garlic straw magnetic biochar has a large number of pore structures, a high specific surface area, rich oxygen-containing functional groups, excellent magnetism, and good adsorption effect on neonicotinoids and methoxyacrylate pesticides.

[0015] The garlic straw magnetic biochar of the present invention is used in the magnetic solid phase extraction detection of neonicotinoids and methoxyacrylate pesticides in environmental water samples, and the detection recovery rate and precision are good. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 The surface morphologies of garlic straw biochar and garlic straw magnetic biochar prepared in Example 1 of the present invention; the left picture shows garlic straw biochar, and the right picture shows garlic straw magnetic biochar. DETAILED DESCRIPTION

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0019] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0020] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0021] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0022] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0023] The "%" described in the present invention, unless otherwise specified, refers to mass percentage.

[0024] The first aspect of the present invention provides a method for preparing magnetic biochar from garlic straw, comprising the following steps:

[0025] The garlic straw is placed in an alkaline solution for activation, and then calcined and carbonized to obtain garlic straw biochar;

[0026] The garlic straw biochar is dispersed in a mixed solvent of water and ethanol, and then a trivalent iron salt solution is first added, and then a divalent iron salt solution and an alkaline precipitant are added to react to obtain the garlic straw magnetic biochar.

[0027] In a preferred embodiment of the present invention, the alkaline solution is a mixed solution of KOH and water in a mass ratio of 1: (1-2); when preparing the alkaline solution, when the mass ratio of KOH and water exceeds the above range, the high concentration of the alkaline solution will destroy the pore structure of the biochar, reduce its specific surface area and pore volume, and thus reduce its adsorption capacity; the low concentration of the alkaline solution affects the modification effect and cannot modify the pore structure and surface functional groups well. The activation time is 17 hours; stirring is also performed during the activation process.

[0028] In a preferred embodiment of the present invention, the calcination and carbonization temperature is 800° C. and the time is 4.5 h.

[0029] In a preferred embodiment of the present invention, in the mixed solvent, the volume ratio of water to ethanol is 1:1; the trivalent iron salt is ferric chloride; the divalent iron salt is ferrous chloride; the alkaline precipitant is aqueous ammonia;

[0030] The mass ratio of the garlic straw biochar to the ferric iron salt and the ferrous iron salt is 1:2:1.

[0031] The present invention does not impose any particular limitation on the amount of the mixed solvent. The amount of the mixed solvent is sufficient to fully disperse the garlic straw biochar and to subsequently synthesize Fe3O4 with divalent iron and trivalent iron.

[0032] In a preferred embodiment of the present invention, after adding the ferric salt solution, the mixture is stirred at 70° C. for 15 minutes, then the temperature is raised to 80° C., the ferrous salt solution and the alkaline precipitant are added, and the mixture is reacted at 80° C. for 70 minutes.

[0033] In a preferred embodiment of the present invention, the biochar is poured into a three-necked flask, water and ethanol are added, and ultrasonic treatment is performed for 30 minutes. Ferrous chloride and ferric chloride are added to water and ultrasonic treatment is performed for 30 minutes. The three-necked flask is taken out and placed in a stirrer, and ferric chloride is first added, and stirred at 70°C for 15 minutes. The temperature is slowly raised to 80°C, ferrous chloride is added, ammonia water is added, and stirring is performed for 70 minutes. The mixture is taken out and poured into a centrifuge tube, washed three times with ethanol, and dried to obtain the garlic straw magnetic biochar.

[0034] A second aspect of the present invention provides a garlic straw magnetic biochar prepared according to the above-mentioned preparation method.

[0035] A third aspect of the present invention provides an application of the above-mentioned garlic straw magnetic biochar in the enrichment and detection of neonicotinoid insecticides or strobilurin fungicides.

[0036] In a preferred embodiment of the present invention, the neonicotinoid insecticide is acetamiprid, imidacloprid and / or thiacloprid; and the strobilurin fungicide is orysastrobin.

[0037] The fourth aspect of the present invention provides a method for enriching and detecting pesticides based on the above-mentioned garlic straw magnetic biochar, wherein the garlic straw magnetic biochar is placed in a water sample for mixing and oscillation (to enrich the pesticides in the garlic straw magnetic biochar), the garlic straw magnetic biochar in the water sample is separated by a magnet and then placed in an acetone solution for desorption to obtain an eluent; the eluent is filtered and then subjected to high performance liquid chromatography analysis and detection, and the pesticide content is calculated according to a standard curve;

[0038] The pesticide is acetamiprid, imidacloprid, thiacloprid or orysastrobin.

[0039] In a preferred embodiment of the present invention, the mass volume ratio of the garlic straw magnetic biochar to the water sample is 20 mg:50 mL; the oscillation time is 30 s;

[0040] The parameters of the HPLC analysis and detection were set as follows: chromatographic column: 5 μm, 150×6 mm; flow rate: 1-5 mL min -1 ; Column temperature: 25°C; Injection volume: 20 μL; Mobile phases are A and B; A is a formic acid aqueous solution with a mass concentration of 0.1%; B is methanol; The gradient elution program is as follows: 0-2 minutes 10% B, 2-5 minutes 10%-40% B, 5-9 minutes 40%-80% B, 9-12 minutes 80% B, 12-14 minutes 80%-10% B, 14-16 minutes 10% B.

[0041] Garlic straw has a large number of functional groups on its surface. After KOH is added, KOH interacts with the functional groups of the above raw materials, and a large number of mesopores and micropores are generated during the calcination process, which greatly increases the specific surface area of ​​biochar and reduces the pore size of biochar. When used for the adsorption of neonicotinoids and methoxyacrylate pesticides, the adsorption rate is fast and the adsorption amount is high. Fe3O4 has excellent magnetic properties. The Fe3O4 biochar is attached to the surface of biochar by in-situ polymerization, making the adsorption and extraction process more convenient.

[0042] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0043] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0044] Example 1

[0045] A method for preparing magnetic biochar,

[0046] Preparation of garlic straw biochar: Wash the garlic straw with deionized water, dry it and cut it into small pieces. Then put the garlic straw into a three-necked flask, soak it in KOH solution (w / v=1:2) and stir it for 17 hours. After drying it in a 70℃ oven, the activated garlic straw was obtained. The activated garlic straw was placed in a tubular furnace under a nitrogen environment. The tubular furnace was heated to 800℃ at a heating rate of 3℃ / min and maintained for 4.5h. The obtained biochar was washed with 1mol / L hydrochloric acid solution and distilled water until it was neutral, and finally dried at 70℃ in a vacuum drying oven for 6h to obtain garlic straw biochar.

[0047] Preparation of garlic straw magnetic biochar: weigh 200 mg of ferrous chloride and 400 mg of ferric chloride, 200 mg of garlic straw biochar, pour the garlic straw biochar into a three-necked flask, add 50 mL of water and 50 mL of ethanol, and ultrasonicate for 30 min; ferrous chloride and ferric chloride are placed in centrifuge tubes and 5 mL of water are added for ultrasonication for 30 min to obtain ferrous chloride solution and ferric chloride solution; put the three-necked flask into a stirrer, add ferric chloride solution first, rinse the centrifuge tube with 5 mL of water, stir for 15 min, 400-600 r / min, 70 ° C. Heat to 80 ° C at a rate of 2 ° C / min, add ferrous chloride solution, rinse the centrifuge tube with 5 mL of water, add 5 mL of 25% ammonia water, and stir for 70 min. Take it out and pour it into a 50 mL centrifuge tube, wash it three times with ethanol, and dry it at 70 ° C to obtain garlic straw magnetic biochar.

[0048] The surface morphology of garlic straw biochar and garlic straw magnetic biochar in this example was observed by scanning electron microscopy. Figure 1 As shown. The garlic straw biochar presents a honeycomb structure with a smooth surface and a large number of irregular macroporous structures. Compared with the original garlic straw biochar, some small spherical particles were observed on the garlic straw magnetic biochar, which made its surface rougher. These tightly bound particles are the introduced Fe3O4. The magnetic Fe3O4 particles are attached to the surface of the biochar and do not occupy the pores where the biochar plays an adsorption role. The successful preparation of magnetic garlic straw biochar not only retains the original rich pore structure of the biochar, but also the introduction of magnetic particles can quickly separate the hybrid material (garlic straw magnetic biochar) and the solution, making the adsorption and extraction process of pesticides more convenient.

[0049] Effect Example 1

[0050] A method for enriching and detecting pesticides based on magnetic biochar of garlic straw is as follows:

[0051] Sample pretreatment: The environmental water samples used in this test were taken from the river water near the orchard and the city tap water. Before testing, the water samples were filtered using a filter membrane to remove suspended matter, particulate matter and other impurities in the water samples to avoid these substances interfering with the analysis results. The treated water samples were stored in brown glass bottles and analyzed and tested on the same day.

[0052] Pesticide enrichment by magnetic solid phase extraction: 20 mg of the garlic straw magnetic biochar prepared in Example 1 was accurately weighed into a 50 mL centrifuge tube, 40 mL of the treated water sample was added, and the mixture was preliminarily mixed by vortexing, and the mixture was placed in an oscillator and shaken for 30 seconds. After the adsorption was completed, the supernatant was separated by a magnet to recover the garlic straw magnetic biochar, and the recovered garlic straw magnetic biochar and 1 mL of acetone solution were added to the centrifuge tube, and the analyte was fully desorbed by vortexing for 40 seconds, and the eluate was collected. The elution process was repeated 3 times. The eluate was filtered through a 0.22 μm nylon filter membrane and analyzed by high performance liquid chromatography (HPLC).

[0053] HPLC detection conditions:

[0054] Chromatographic column: (5 μm, 150 × 6 mm);

[0055] Flow rate: 0.8mLmin -1 ;

[0056] Column temperature: 25°C;

[0057] Injection volume: 20 μL;

[0058] Mobile phase: 0.1% formic acid-water (A) and methanol (B);

[0059] The gradient elution program was as follows: 0-2 min 10% (B), 2-5 min 10%-40% (B), 5-9 min 40%-80% (B), 9-12 min 80% (B), 12-14 min 80%-10% (B), 14-16 min 10% (B).

[0060] The standard curve was prepared as follows:

[0061] Dilute 2ug / mL strobilurin fungicide (orysastrobin) standard solution with ultrapure water, and prepare standard solutions with concentrations of 0.02, 0.1, 0.5, 1, 2, 5, and 10ug / mL step by step. Detect, and obtain the standard substance curve based on the results, and make a standard curve based on the detection peak area versus concentration.

[0062] Dilute 1ug / mL neonicotinoid insecticide (acetamiprid, imidacloprid, thiacloprid) standard solution with ultrapure water, and gradually prepare standard solutions with concentrations of 0.01, 0.05, 0.25, 0.5, 1, 2.5, and 5ug / mL. Detect, and obtain the standard material curve based on the results, and make a standard curve based on the detection peak area versus concentration.

[0063] The recovery and precision of the pesticides tested are as follows:

[0064] The four pesticides had good linearity in the range of 0.05-20 ng / mL, R 2 ≥0.9997. LODs (limit of detection) and LOQs (limit of quantification) are 0.21-0.75 ng / mL and 1.70-2.60 ng / mL, respectively, and RSD values ​​(relative standard deviation) are 0.30%-1.90%. At 10, 50, 100 ng / mL for spiking, the spiked recoveries of neonicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid) are 70.2%-99.5%. At 20, 100, 200 ng / mL for spiking, the spiked recoveries of strobilurin fungicides (oxazolidinone) are 70%-97.5%.

[0065] The present invention also verifies the recovery rate of garlic straw magnetic biochar on pesticides, namely, methyl parathion, chlorpyrifos and malathion. The verification method is the same as that of effect example 1. The results are statistically shown in Table 1.

[0066] Table 1

[0067]

[0068] It can be seen from Table 1 that the garlic straw magnetic biochar of the present invention has a good recovery rate and adsorption effect on neonicotinoids and strobilurin pesticides such as orysastrobin, acetamiprid, imidacloprid and thiacloprid, but has a poor adsorption effect on other pesticides (organophosphorus), which proves that the obtained magnetic biochar has a certain specificity.

[0069] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing magnetic biochar from garlic straw, characterized in that: The following steps are involved: The garlic straw is placed in an alkaline solution for activation, and then calcined and carbonized to obtain garlic straw biochar; The garlic straw biochar is dispersed in a mixed solvent of water and ethanol, and then a trivalent iron salt solution is first added, and then a divalent iron salt solution and an alkaline precipitant are added to react to obtain the garlic straw magnetic biochar.

2. The method for preparing magnetic biochar from garlic straw according to claim 1, characterized in that: The alkaline solution is a mixed solution of KOH and water in a mass ratio of 1:(1-2); the activation time is 17 hours; and stirring is required during the activation process.

3. The method for preparing magnetic biochar from garlic straw according to claim 1, characterized in that: The calcination and carbonization temperature is 800° C. and the time is 4.5 h.

4. The method for preparing magnetic biochar from garlic straw according to claim 1, characterized in that: In the mixed solvent, the volume ratio of water to ethanol is 1:1; the ferric iron salt is ferric chloride; the ferrous iron salt is ferrous chloride; the alkaline precipitant is ammonia water; and the mass ratio of the garlic straw biochar to the ferric iron salt and the ferrous iron salt is 1:2:

1.

5. The method for preparing magnetic biochar from garlic straw according to claim 1, characterized in that: After adding the ferric salt solution, stir at 70°C for 15 minutes, then heat to 80°C, add the ferrous salt solution and alkaline precipitant, and react at 80°C for 70 minutes.

6. Garlic straw magnetic biochar prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the garlic straw magnetic biochar as claimed in claim 6 in enriching and detecting neonicotinoid insecticides or strobilurin fungicides.

8. The use according to claim 7, characterized in that: The neonicotinoid insecticide is acetamiprid, imidacloprid and / or thiacloprid; the strobilurin fungicide is orysastrobin.

9. A method for enriching and detecting pesticides based on the magnetic biochar of garlic straw according to claim 6, characterized in that: The magnetic biochar of garlic straw is placed in a water sample for mixing and oscillation, and the magnetic biochar of garlic straw in the water sample is separated by a magnet and then placed in an acetone solution for desorption to obtain an eluent; the eluent is filtered and then subjected to high performance liquid chromatography analysis and detection, and the pesticide content is calculated according to a standard curve; The pesticide is acetamiprid, imidacloprid, thiacloprid or orysastrobin.

10. The method according to claim 9, characterized in that The mass ratio of the garlic straw magnetic biochar to the water sample is 1:(1000-3000); the oscillation time is 30s; The parameters of the HPLC analysis and detection were set as follows: chromatographic column: 5 μm, 150×6 mm; flow rate: 1-5 mL min -1 ; Column temperature: 25°C; Injection volume: 20 μL; Mobile phases are A and B; A is a formic acid aqueous solution with a mass concentration of 0.1%; B is methanol; The gradient elution program is as follows: 0-2 minutes 10% B, 2-5 minutes 10%-40% B, 5-9 minutes 40%-80% B, 9-12 minutes 80% B, 12-14 minutes 80%-10% B, 14-16 minutes 10% B.

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