Detection pretreatment method of amide herbicides in environmental water body

Abstract

The invention discloses a detection pretreatment method for an amide herbicide in an environmental water body, and belongs to the technical field of pesticide residue analys.The method comprises the steps that the environmental water body containing the amide herbicide is centrifuged, and supernate is obtained; adding sodium tartrate and ascorbic acid into the supernate, and carrying out vortex mixing to obtain a mixed solution; the pH value of the mixed solution is measured, and if the pH value is not in the range of 6.5-7.5, the pH value of the mixed solution is adjusted to 6.5-7.5; filtering the mixed solution with the pH value of 6.5-7.5 to obtain a filtrate; cooling the filtrate to 60 DEG C below zero to 80 DEG C below zero, and pre-freezing; freeze-drying the pre-frozen filtrate, wherein the vacuum degree is kept to be less than or equal to 10Pa in the freeze-drying process; dissolving the freeze-dried sample by using acetonitrile or normal hexane, and standing; filtering the sample after standing for the second time for subsequent detection; according to the pretreatment method, the recovery rate of the sample is improved, and the variable coefficient of a test result is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticide residue analysis, and in particular relates to a pre-treatment method for detecting amide herbicides in environmental water. Background Art

[0002] The widespread use of herbicides in agricultural production, while promoting agricultural production, has also caused a series of environmental problems. After application, herbicides can enter water bodies through rainfall and surface runoff, posing potential risks to ecosystems and human health. Amide herbicides are currently one of the most widely used types of selective herbicides globally, widely used to control weed growth in agricultural production. Their residues in aquatic environments are a growing concern. Amide herbicide residues in water bodies not only affect water quality but can also accumulate through the food chain, causing toxic effects on organisms. Therefore, accurately monitoring the concentration of amide herbicides in water is particularly important.

[0003] Among them, the extraction method is an important link in the herbicide detection process. An efficient, stable and environmentally friendly extraction method can ensure the scientificity and accuracy of the detection data. Therefore, the development of an efficient, stable and environmentally friendly amide herbicide extraction method is one of the current research focuses in this field. At present, the commonly used amide herbicide extraction methods mainly include liquid-liquid extraction and solid-phase extraction, but there are problems such as unstable recovery rate and easy secondary pollution. Specifically, they include: (1) high organic solvent usage, which is easy to cause environmental pollution; (2) high cost of solid-phase extraction columns; (3) strict control of elution conditions, unstable recovery rate; (4) evaporation and concentration operation steps during extraction are prone to high-temperature decomposition of amide herbicides; (5) amide herbicides in water are easily interfered by metal ions, resulting in reduced recovery rate; (6) amide herbicides are easily oxidized, resulting in reduced recovery rate; (7) the pH of the water sample affects the unstable recovery rate of amide herbicides. Summary of the Invention

[0004] In response to the defects of existing methods for extracting amide herbicides from water, the present invention proposes a pretreatment method for detecting amide herbicides in environmental water, which aims to achieve: 1. significantly reduce the use of organic solvents; 2. reduce the interference of metal ions, oxides, etc.; 3. avoid complex operating steps that affect the recovery rate of the target; 4. stably increase the recovery rate of the target to more than 90%. The sample to be tested after extraction using the method of the present invention can meet the measurement requirements of methods such as GC (gas chromatography), HPLC (high performance liquid chromatography), GC-MS (gas chromatography-mass spectrometry), HPLC-MS (high performance liquid chromatography-mass spectrometry), GC-MS / MS (gas chromatography-tandem mass spectrometry), and HPLC-MS / MS (high performance liquid chromatography-tandem mass spectrometry).

[0005] To achieve the above object, the present invention provides a pre-treatment method for detecting amide herbicides in environmental water, comprising the following steps:

[0006] The environmental water containing the amide herbicide is centrifuged to obtain a supernatant;

[0007] adding sodium tartrate and ascorbic acid to the supernatant, vortex mixing, and obtaining a mixed solution;

[0008] Determining the pH of the mixed solution, and if the pH is not within the range of 6.5-7.5, adjusting the pH of the mixed solution to 6.5-7.5;

[0009] Filtering the mixed solution with a pH of 6.5-7.5 to obtain a filtrate;

[0010] Cooling the filtrate to -60 to -80°C for pre-freezing;

[0011] The pre-frozen filtrate is freeze-dried, and the vacuum degree is maintained at ≤10Pa during the freeze-drying process;

[0012] Dissolve the freeze-dried sample in acetonitrile or n-hexane (if gas chromatography is used for subsequent detection, dissolve it in n-hexane; if liquid chromatography is used for subsequent detection, dissolve it in acetonitrile) and let it stand;

[0013] The samples after standing were filtered twice for subsequent testing.

[0014] Freeze drying is a drying method that removes moisture from a sample by means of low-temperature freezing and vacuum dehydration, which can maintain the structure and chemical composition of the sample. In the present invention, freeze drying technology can not only effectively remove the moisture of the sample matrix, but also reduce the interference of the sample matrix to detection, and low-temperature treatment can avoid the decomposition or volatilization of amide herbicides at high temperatures, ensuring its chemical stability, thereby improving the recovery rate of the target object. At the same time, freeze drying technology does not need to use a large amount of organic solvents, reducing environmental pollution and the health risks of operators. Freeze drying technology, as a kind of efficient and environmentally friendly sample pretreatment method, has significant advantages in the pretreatment of detecting amide herbicides. The sample to be tested after extraction using the inventive method can meet the needs of the main detection technologies such as current GC, HPLC, GC-MS, HPLC-MS, GC-MS / MS, HPLC-MS / MS, and has the advantages of environmental protection, easy operation, high recovery rate and stability, and provides a new technical method for the detection of amide herbicides in water.

[0015] Furthermore, the amide herbicide includes acetochlor, pretilachlor or butachlor.

[0016] Furthermore, the centrifugal speed is 1800-2200 rpm, and the centrifugal time is 3-5 min.

[0017] Furthermore, the volume ratio of the supernatant, sodium tartrate and ascorbic acid is (10-20):(0.5-1):(0.5-1).

[0018] Furthermore, the concentration of the sodium tartrate is 0.01 mol / L, and the concentration of the ascorbic acid is 0.01 mol / L.

[0019] Furthermore, the pH of the mixed solution is adjusted to 6.5-7.5 using 0.01 mol / L hydrochloric acid or 0.01 mol / L sodium hydroxide solution.

[0020] Furthermore, the filtration is performed using a 0.45 μm water filter membrane.

[0021] Exemplarily, the water filter membrane is selected from mixed cellulose ester (CN-CA) membrane.

[0022] Furthermore, the cooling rate to -60 to -80°C is -3°C / min;

[0023] The pre-freezing time is 2 hours, that is, in this step, the temperature is first lowered to -60 to -80°C at a cooling rate of -3°C / min, and then kept warm for 2 hours, that is, the pre-freezing time is 2 hours.

[0024] Furthermore, the freeze-drying temperature is -40 to -60°C, and the freeze-drying time is 4 to 6 hours.

[0025] Furthermore, the secondary filtration is performed using a 0.22 μm organic filter membrane.

[0026] Exemplarily, the organic filter membrane is selected from polyvinylidene fluoride (PVDF) membrane.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] The present invention is the first to apply freeze drying technology to the pretreatment of amide herbicide detection in water, and improves the recovery rate by adjusting the pH to the neutral range; the metal masking agent sodium tartrate is used to reduce the metal ions (such as Fe 3+ 、Al 3+The invention also reduces the interference of oxidative stress (e.g., oxidative stress) on sample extraction by using ascorbic acid to prevent oxidative interference, thereby further improving the recovery rate. It also avoids the problem of amide herbicide decomposition caused by high temperatures during the evaporation and concentration process in liquid-liquid extraction. It also avoids the problem of reduced recovery caused by solvent conversion in traditional extraction methods. It also avoids the problem of reduced recovery caused by incomplete elution in solid-phase extraction. The method of the present invention does not include high-temperature operation steps, nor does it have elution and solvent conversion steps, thus avoiding the problems caused by these operating steps. The invention uses gradient cooling for pre-freezing followed by freeze-drying, thereby improving the recovery rate and stability of the method. DETAILED DESCRIPTION

[0029] 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 rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 any conflict with any incorporated document, the contents of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] At present, the detection of amide herbicides in water bodies has the following pain points: metal ions in water (such as Fe 3+etc.) can combine with amide herbicide molecules to form insoluble complexes, thereby reducing the recovery rate; traditional liquid-liquid extraction uses rotary evaporation for heating and concentration, and the high temperature conditions during the heating process can easily lead to the decomposition of amide compounds, reducing the recovery rate; both liquid-liquid extraction and solid-phase extraction methods require the use of large amounts of organic solvents, which can easily cause secondary environmental pollution; the solid-phase extraction elution process requires precise control of the flow rate and solvent ratio, and incomplete elution can easily lead to a reduction in the recovery rate; under different pH conditions, the recovery rate of existing methods for extracting amide herbicides is unstable; amide compounds in water are prone to decomposition in the presence of oxidizing substances (such as dissolved oxygen, etc.). In view of this, an embodiment of the present invention provides a pretreatment method for detecting amide herbicides in environmental water, comprising the following steps:

[0035] The environmental water containing the amide herbicide is centrifuged to obtain a supernatant;

[0036] Sodium tartrate and ascorbic acid were added to the supernatant, and the mixture was vortexed to obtain a mixed solution;

[0037] Measure the pH of the mixed solution. If the pH is not within the range of 6.5-7.5, adjust the pH of the mixed solution to 6.5-7.5;

[0038] Filtering the mixed solution with a pH of 6.5-7.5 to obtain a filtrate;

[0039] The filtrate is cooled to -60 to -80°C for pre-freezing;

[0040] The pre-frozen filtrate is freeze-dried, and the vacuum degree is maintained at ≤10Pa during the freeze-drying process;

[0041] Dissolve the freeze-dried sample in acetonitrile or n-hexane and let it stand;

[0042] The samples after standing were filtered twice for subsequent testing.

[0043] In the embodiments of the present invention, environmental water refers to natural waters bounded by relatively stable land in nature, including water, suspended matter, sediment, and aquatic organisms. This encompasses surface water, groundwater, and marine waters, and is an important component of the aquatic environment. In the following embodiments of the present invention, paddy field water is used as an example for illustration.

[0044] Freeze drying is a drying method that removes moisture from a sample by means of low-temperature freezing and vacuum dehydration, which can maintain the structure and chemical composition of the sample. In the present invention, freeze drying technology can not only effectively remove the moisture of the sample matrix, but also reduce the interference of the sample matrix to detection, and low-temperature treatment can avoid the decomposition or volatilization of amide herbicides at high temperatures, ensuring its chemical stability, thereby improving the recovery rate of the target object. At the same time, freeze drying technology does not need to use a large amount of organic solvents, reducing environmental pollution and the health risks of operators. Freeze drying technology, as a kind of efficient and environmentally friendly sample pretreatment method, has significant advantages in the pretreatment of detecting amide herbicides. The sample to be tested after extraction using the inventive method can meet the needs of the main detection technologies such as current GC, HPLC, GC-MS, HPLC-MS, GC-MS / MS, HPLC-MS / MS, and has the advantages of environmental protection, easy operation, high recovery rate and stability, and provides a new technical method for the detection of amide herbicides in water.

[0045] In an embodiment of the present invention, the amide herbicide includes acetochlor, pretilachlor or butachlor.

[0046] In the embodiment of the present invention, the centrifugal speed is 1800-2200 rpm, the centrifugal time is 3-5 min, and the centrifugal temperature is 4° C.; preferably, the centrifugal speed is 2000 rpm and the time is 5 min.

[0047] In the embodiment of the present invention, the volume ratio of the supernatant, sodium tartrate and ascorbic acid is (10-20): (0.5-1): (0.5-1), wherein the concentration of sodium tartrate is 0.01 mol / L, and the concentration of ascorbic acid is 0.01 mol / L. There are some metal ions (such as Fe 3+ 、Al 3+ , Ca 2+ Mg 2+ 、Cu 2+The tartrate ion can form a stable, water-soluble complex with these metal ions, preventing the metal ions from reacting with the target amide herbicide molecules or their subsequent detection reagents, which may cause the herbicide to be precipitated, adsorbed, or change the reaction characteristics; reduce the possibility of certain metal ions catalyzing the oxidative decomposition or other side reactions of the amide herbicide molecules; reduce the deposition of metal ions and their hydroxides, carbonates, etc. on subsequent filter membranes, chromatographic columns or detectors, protect the instruments and ensure smoothness; reduce the loss of target substances due to precipitation, adsorption or degradation, and improve the recovery rate; reduce the potential interference of metal ions with subsequent analytical steps (such as chromatographic separation and detection), make the results more reliable and reproducible, and ensure the stability of the method. Oxidizing substances (such as dissolved oxygen, residual chlorine, ozone, peroxides, high-valent metal ions, etc.) may also exist in environmental water bodies. Ascorbic acid preferentially reacts with oxidizing substances and is oxidized itself (dehydroascorbic acid), thereby consuming or eliminating these oxidants, preventing oxidizing substances from causing oxidative degradation of target amide herbicide molecules (especially some amide herbicides containing easily oxidizable groups), generating interferences or causing target loss. It can also eliminate other side reactions caused by oxidants that may interfere with detection, protect oxidation-sensitive reagents or chromatographic column fillers that may be used in subsequent freeze-drying, dissolution and analysis processes, ensure that intact, undegraded target amide herbicide molecules are detected, and improve detection accuracy; significantly reduce target loss caused by oxidative degradation, and improve recovery rate; extend the service life of chromatographic columns and detectors, and protect the analysis system. Sodium tartrate and ascorbic acid can also produce a synergistic effect, ensuring that the target is effectively extracted and accurately measured by eliminating metal ion complexation, precipitation, and oxidative degradation, avoiding erroneous results due to loss (false negatives) or introduction of degradation product interference (false positives), and significantly improving the recovery rate of the target; by controlling the two main sources of interference, metal ions and oxidants, the pretreatment process is made more controllable, ensuring that the measurement results of different batches of samples have smaller fluctuations and better reproducibility.

[0048] In an embodiment of the present invention, the pH of the mixed solution is adjusted to 6.5-7.5 using 0.01 mol / L hydrochloric acid or 0.01 mol / L sodium hydroxide solution.

[0049] In an embodiment of the present invention, the filtration is performed using a 0.45 μm water filter membrane. Ambient water bodies contain a large amount of inorganic particles (such as sediment, minerals) and organic particles (such as algae fragments, plant residues, and microorganisms). The 0.45 μm water filter membrane can efficiently intercept these impurities, ensuring that the samples processed subsequently are clear liquids. Filtration with a 0.45 μm water filter membrane can also prevent particulate matter from contaminating the freeze-dried sample container, and more importantly, it can prevent it from entering the final detection instrument (such as the injection needle or chromatographic column of HPLC or GC), causing irreversible damage. Particulate matter may carry interfering substances (such as humic acid and metal oxides), and filtration can reduce the complexity of the sample matrix and reduce interference. The particulate matter content in the unfiltered sample fluctuates with the sampling position and time, resulting in increased differences between samples from the same batch. The liquid matrix homogenized after filtration significantly improves the reproducibility of the method.

[0050] In an embodiment of the present invention, the water filter membrane is a mixed cellulose ester (CN-CA) membrane.

[0051] In an embodiment of the present invention, the cooling rate to -60 to -80°C is -3°C / min; the pre-freezing time is 2 hours. During the pre-freezing process, the water in the sample can be slowly and directionally crystallized by controlling the cooling rate, thereby avoiding irregular distribution of ice crystals or local liquid residue caused by rapid freezing. If directly freeze-dried by vacuum, the instantaneous boiling of liquid water will cause splashing loss of the sample. Pre-freezing completely solidifies the water and ensures the safety of subsequent freeze-drying. The uniform ice crystal structure can prevent the herbicide molecules from being wrapped in tiny ice crystals, thereby improving the efficiency of subsequent freeze-drying.

[0052] In the embodiments of the present invention, the freeze-drying temperature is -40 to -60°C, and the freeze-drying time is 4 to 6 hours. Freeze-drying can avoid volatile / thermosensitive losses caused by heating, converting the aqueous sample into an anhydrous solid residue, facilitating the subsequent efficient extraction of the herbicide using an organic solvent (acetonitrile / n-hexane). The vacuum environment significantly shortens the drying time and isolates oxygen, preventing oxidation reactions or chemical denaturation of the sample during the drying process.

[0053] In an embodiment of the present invention, the secondary filtration is performed using a 0.22 μm organic filter membrane. The secondary filtration can remove micron / submicron impurities in the organic phase (such as salt crystals (such as sodium tartrate and ascorbate) precipitated during the dissolution of the freeze-dried residue, silica gel particles on the tube wall (abrasion of the centrifuge tube / test tube) brought out during organic solvent extraction, and incompletely dissolved colloidal humic acid (a common interferent in environmental water bodies), thereby preventing clogging of the chromatography system, avoiding detector contamination, and eliminating injection needle clogging or injection volume errors caused by particulates.

[0054] In an embodiment of the present invention, the organic filter membrane is a polyvinylidene fluoride (PVDF) membrane.

[0055] Exemplary, a pre-treatment method for detecting amide herbicides in environmental water includes the following steps:

[0056] 1. Pretreatment: Place 20-40 mL of environmental water containing amide herbicides in a 50 mL centrifuge tube and centrifuge at 4°C and 2000 rpm for 5 minutes;

[0057] 2. Add anti-interference agent: Accurately measure 10-20 mL of the supernatant after centrifugation into a 25 mL test tube, add 0.5-1 mL of 0.01 mol / L sodium tartrate and 0.5-1 mL of 0.01 mol / L ascorbic acid, and vortex mix for 1 min to obtain a mixed solution;

[0058] 3. Adjust pH: Measure the pH of the mixture. If the pH is not within the range of 6.5-7.5, adjust the pH to between 6.5-7.5 with 0.01 mol / L hydrochloric acid or 0.01 mol / L sodium hydroxide solution.

[0059] 4. Filtration: Filter through a 0.45 μm water filter membrane;

[0060] 5. Pre-freezing: In a freeze dryer, cool the filtrate to -60--80°C at a cooling rate of -3°C / min and pre-freeze for 2 hours;

[0061] 6. Freeze drying: After pre-freezing, freeze dry (lyophilize) at -40 to -60°C in a vacuum for 4 to 6 hours. Keep the vacuum degree ≤10Pa during the freeze drying process.

[0062] 7. Extraction: Take out the freeze-dried sample, rinse the tube wall thoroughly with 1-2 mL acetonitrile or 1-2 mL n-hexane, and let it stand for 10 minutes;

[0063] 8. Secondary filtration for testing: After standing, the sample is filtered through a 0.22 μm organic filter membrane and transferred to a 2 mL brown bottle for testing.

[0064] Unless otherwise specified, the room temperature in the present invention is 25±2°C.

[0065] It should be pointed out that the matters not described in detail in the present invention are all conventional operating means in the field and are not the focus of the present invention. For example, specific detection methods such as GC (gas chromatography), HPLC (high performance liquid chromatography), GC-MS (gas chromatography-mass spectrometry (GC-MS)), HPLC-MS (high performance liquid chromatography-mass spectrometry (LC-MS)), GC-MS / MS (gas chromatography-tandem mass spectrometry), and HPLC-MS / MS (high performance liquid chromatography-tandem mass spectrometry) are all carried out using conventional methods.

[0066] The technical solution of the present invention is further illustrated by the following examples.

[0067] Example 1

[0068] A pre-treatment method for detecting amide herbicides in environmental water bodies comprises the following steps:

[0069] 1. Pretreatment: In this example, the environmental water body is paddy water. Take 20 mL of water sample containing 0.5 mg / L acetochlor and place it in a 50 mL centrifuge tube. Centrifuge at 4°C and 2000 rpm for 5 min.

[0070] 2. Add anti-interference agent: Accurately measure 10 mL of the supernatant after centrifugation, place it in a 25 mL test tube, add 0.5 mL of 0.01 mol / L sodium tartrate and 0.5 mL of 0.01 mol / L ascorbic acid, and vortex mix for 1 min;

[0071] 3. Adjust pH: Use 0.01 mol / L hydrochloric acid or 0.01 mol / L sodium hydroxide solution to adjust the pH of the water sample to 6.8;

[0072] 4. Filtration: Filter through a 0.45 μm water filter membrane (mixed cellulose ester (CN-CA) membrane);

[0073] 5. Pre-freezing: In a freeze dryer, cool the filtrate to -60°C at a temperature gradient of -3°C / min and pre-freeze for 2 hours;

[0074] 6. Freeze drying: After pre-freezing, freeze-dry at -40℃ for 4 hours in a vacuum environment. Keep the vacuum degree ≤10Pa during the freezing process.

[0075] 7. Extraction: Take out the freeze-dried sample, rinse the tube wall thoroughly with 1 mL of acetonitrile, and let it stand for 10 minutes;

[0076] 8. Secondary filtration for testing: After standing, the sample is filtered through a 0.22 μm organic filter membrane (polyvinylidene fluoride (PVDF) membrane) and transferred to a 2 mL brown bottle for testing.

[0077] The concentration of acetochlor in the sample was determined by liquid chromatography, where the chromatographic column was C 18 The chromatographic column was used, and the mobile phase consisted of acetonitrile and ultrapure water, with volumes of 70 mL and 30 mL respectively; the detection wavelength was 230 nm; the isocratic elution method was adopted, and the elution time was set to 10 min; the flow rate was 1.0 mL / min; the column temperature was 30°C; and the injection volume was 20 μL.

[0078] The above operation was repeated 6 times, and the average recovery was 94.33% and the coefficient of variation was 1.88%.

[0079] Example 2

[0080] A pre-treatment method for detecting amide herbicides in environmental water bodies comprises the following steps:

[0081] 1. Pretreatment: In this example, the environmental water body is paddy water. 30 mL of water sample containing 0.5 mg / L pretilachlor was placed in a 50 mL centrifuge tube and centrifuged at 4°C and 2000 rpm for 5 min.

[0082] 2. Add anti-interference agent: Accurately measure 15 mL of the supernatant after centrifugation and place it in a 25 mL test tube. Add 1.0 mL of 0.01 mol / L sodium tartrate and 1.0 mL of 0.01 mol / L ascorbic acid, and vortex mix for 1 min.

[0083] 3. Adjust pH: Use 0.01 mol / L hydrochloric acid or 0.01 mol / L sodium hydroxide solution to adjust the pH of the water sample to 7.0;

[0084] 4. Filtration: Filter through a 0.45 μm water filter membrane (CN-CA membrane);

[0085] 5. Pre-freezing: In a freeze dryer, cool the filtrate to -70°C at a cooling rate of -3°C / min and pre-freeze for 2 hours;

[0086] 6. Freeze drying: After pre-freezing, freeze-dry at -50℃ for 5 hours in a vacuum environment. Keep the vacuum degree ≤10Pa during the freezing process.

[0087] 7. Extraction: Take out the freeze-dried sample, rinse the tube wall thoroughly with 2 mL of acetonitrile, and let it stand for 10 minutes;

[0088] 8. Secondary filtration for testing: After standing, the sample is filtered through a 0.22 μm organic filter membrane (PVDF membrane) and transferred to a 2 mL brown bottle for testing.

[0089] The concentration of pretilachlor in the sample was determined by liquid chromatography, where the chromatographic column was C 18 The chromatographic column was used, and the mobile phase consisted of methanol and ultrapure water, with volumes of 75 mL and 25 mL respectively; the detection wavelength was 220 nm; the isocratic elution method was adopted, and the elution time was set to 15 min; the flow rate was 1.0 mL / min; the column temperature was 40°C; and the injection volume was 20 μL.

[0090] The above operation was repeated 6 times, and the average recovery was 92.81% and the coefficient of variation was 2.21%.

[0091] Example 3

[0092] A pre-treatment method for detecting amide herbicides in environmental water bodies comprises the following steps:

[0093] 1. Pretreatment: In this example, the environmental water body is paddy water. 40 mL of water sample containing 0.5 mg / L butachlor was placed in a 50 mL centrifuge tube and centrifuged at 4°C and 2000 rpm for 5 min.

[0094] 2. Add anti-interference agent: Accurately measure 20 mL of the supernatant after centrifugation and place it in a 25 mL test tube. Add 1.0 mL of 0.01 mol / L sodium tartrate and 1.0 mL of 0.01 mol / L ascorbic acid, and vortex mix for 1 min.

[0095] 3. Adjust pH: Use 0.01 mol / L hydrochloric acid or 0.01 mol / L sodium hydroxide solution to adjust the pH of the water sample to 7.2;

[0096] 4. Filtration: Filter through a 0.45 μm water filter membrane (CN-CA membrane);

[0097] 5. Pre-freezing: In a freeze dryer, cool the filtrate to -80°C at a cooling rate of -3°C / min and pre-freeze for 2 hours;

[0098] 6. Freeze drying: After pre-freezing, freeze-dry at -60℃ under vacuum for 6 hours, and keep the vacuum degree ≤10Pa during the freezing process;

[0099] 7. Extraction: Take out the freeze-dried sample, rinse the tube wall thoroughly with 1 mL of n-hexane, and let it stand for 10 minutes;

[0100] 8. Secondary filtration for testing: After standing, the sample is filtered through a 0.22 μm organic filter membrane (PVDF membrane) and transferred to a 2 mL brown bottle for testing.

[0101] The concentration of butachlor in the sample was determined by liquid chromatography, where the chromatographic column was C 18 The chromatographic column was used, and the mobile phase consisted of acetonitrile and water, with volumes of 90 mL and 10 mL respectively; the detection wavelength was 215 nm; the isocratic elution method was adopted, and the elution time was set to 10 min; the flow rate was 1.0 mL / min; the column temperature was 40°C; and the injection volume was 10 μL.

[0102] The above experimental process was repeated 6 times, and the average recovery rate was measured to be 93.56% and the coefficient of variation was 1.71%.

[0103] Comparative Example 1 Liquid-Liquid Extraction Operation

[0104] 1. Pretreatment: The environmental water body in this comparative example is paddy field water. Take 20 mL of water sample containing 0.5 mg / L acetochlor and place it in a 50 mL separatory funnel rinsed with dichloromethane;

[0105] 2. Add extractant: Add 20 mL of dichloromethane and 1 g of sodium chloride to the separatory funnel and shake and extract for 15 minutes;

[0106] 3. Let stand and separate the layers: Place the separatory funnel on the funnel stand and let it stand for 10 minutes;

[0107] 4. Concentration: Transfer the separated dichloromethane phase to a rotary evaporator and evaporate to near dryness at 40°C.

[0108] 5. Volume adjustment: Add 1 mL of acetonitrile to dissolve and adjust to volume;

[0109] 6. Filtration: After the volume is fixed, the filtrate is filtered through a 0.22 μm organic filter membrane (PVDF membrane) and transferred to a 2 mL brown sample bottle for testing.

[0110] The concentration of acetochlor in the test samples was determined by liquid chromatography.

[0111] The above experimental process was repeated 6 times, and the average recovery rate was measured to be 83.12% and the coefficient of variation was 8.38%.

[0112] Comparative Example 2 Solid Phase Extraction Operation

[0113] 1. SPE column activation (C 18 Activate the SPE column by slowly passing 5 mL of dichloromethane, 5 mL of ethyl acetate, 10 mL of methanol, and 10 mL of ultrapure water through the column at a flow rate of 5 mL / min.

[0114] 2. Extraction: Take 20 mL of water sample containing 0.5 mg / L acetochlor (the environmental water body in this comparative example is rice field water) and pass the water sample through the SPE cartridge at a flow rate of 5 mL / min, and then blow dry with nitrogen;

[0115] 3. Elution: Elute the SPE column with 10 mL of ethyl acetate at a flow rate of 3 mL / min and collect the eluate on a rotary evaporator;

[0116] 4. Concentration: Rotary evaporate the eluate in a water bath at 40°C until nearly dry;

[0117] 5. Dilute to 1 mL with acetonitrile;

[0118] 6. Filtration: After the volume is fixed, the filtrate is filtered through a 0.22 μm organic filter membrane (PVDF membrane) and transferred to a 2 mL brown sample bottle for testing.

[0119] The concentration of acetochlor in the samples was determined by liquid chromatography.

[0120] The above experimental process was repeated 6 times, and the average recovery rate was measured to be 91.92% and the coefficient of variation was 9.88%.

[0121] The comparison of the amount of organic solvent (mL) used in the extraction process using the above different methods is shown in Table 1.

[0122] Table 1 Amount of organic solvent used in the extraction process of different methods (mL)

[0123] Liquid-liquid extraction Solid Phase Extraction Method of the present invention 20 30 0

[0124] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A pre-treatment method for detecting amide herbicides in environmental water, characterized in that: The following steps are involved: The environmental water containing the amide herbicide is centrifuged to obtain a supernatant; adding sodium tartrate and ascorbic acid to the supernatant, vortex mixing, and obtaining a mixed solution; Adjusting the pH of the mixed solution to 6.5-7.5; Filtering the mixed solution with a pH of 6.5-7.5 to obtain a filtrate; Cooling the filtrate to -60 to -80°C for pre-freezing; The pre-frozen filtrate is freeze-dried, and the vacuum degree is maintained at ≤10Pa during the freeze-drying process; Dissolve the freeze-dried sample in acetonitrile or n-hexane and let it stand; After standing, the sample is filtered twice for subsequent testing.

2. The pre-treatment method for detecting amide herbicides in environmental water according to claim 1, characterized in that: The amide herbicides include acetochlor, pretilachlor or butachlor.

3. The pre-treatment method for detecting amide herbicides in environmental water according to claim 1, characterized in that: The centrifugal speed is 1800-2200 rpm, and the centrifugal time is 3-5 min.

4. The pre-treatment method for detecting amide herbicides in environmental water according to claim 1, characterized in that: The volume ratio of the supernatant, sodium tartrate and ascorbic acid is (10-20):(0.5-1):(0.5-1).

5. The pre-treatment method for detecting amide herbicides in environmental water according to claim 1, characterized in that: The pH of the mixed solution is adjusted to 6.5-7.5 with 0.01 mol / L hydrochloric acid or 0.01 mol / L sodium hydroxide solution.

6. The pre-treatment method for detecting amide herbicides in environmental water according to claim 1, characterized in that: The filtration is carried out using a 0.45 μm water filter membrane.

7. The pre-treatment method for detecting amide herbicides in environmental water according to claim 1, characterized in that: The cooling rate to -60 to -80°C is -3°C / min; The pre-freezing time is 2 hours.

8. The pre-treatment method for detecting amide herbicides in environmental water according to claim 1, characterized in that: The freeze-drying temperature is -40 to -60°C, and the freeze-drying time is 4 to 6 hours.

9. The pre-treatment method for detecting amide herbicides in environmental water according to claim 1, characterized in that: The secondary filtration is performed by filtering with a 0.22 μm organic filter membrane.

10. The pre-treatment method for detecting amide herbicides in environmental water according to claim 9, characterized in that: The organic filter membrane is selected from polyvinylidene fluoride membrane.