A method and device for determining triazine pesticides in site soil

Abstract

The present invention discloses a triazine pesticide determination device, comprising a DGT device, comprising a diffusion layer, an impurity filtration layer, and a fixed layer. The diffusion layer comprises a diffusion membrane and a filter membrane; the impurity filtration layer is a membrane containing ethylenediamine-N-propyl bonded silica gel; and the fixed layer is an adsorption membrane containing carbon nanotubes. The DGT technique is used to determine triazine pesticides in water or soil to be measured.

Description

Technical Field

[0001] The present invention relates to a triazine pesticide, in particular to a determination method and device for atrazine. Background Art

[0002] Triazine pesticides are a traditional herbicide class introduced as early as the 1950s. They work by inhibiting plant photosynthesis by targeting the D1 protein in photosynthetic system II (PSII). While this class of herbicide once played a significant role in agriculture, its market has declined due to its high usage, long residual effects, and the rapid development of new herbicides such as sulfonylureas. Despite this, it still ranks fifth among major herbicide classes, behind amino acids (such as glyphosate), sulfonylureas, amides, and aryloxyphenoxypropionic acid herbicides. For example, atrazine, a member of the triazine class, has been widely used in my country due to its excellent weed control effectiveness. Atrazine is highly persistent in the environment, with a half-life varying depending on environmental conditions, ranging from over a month to two years. Its half-life is longer in soil than in aquatic environments. Atrazine in soil can spread into surrounding water bodies through precipitation or irrigation, causing wider environmental pollution. It can then accumulate through the food chain, posing a threat to ecological safety and human health. Atrazine can also affect the growth and reproduction of aquatic organisms, potentially causing denaturation, and is a potential human carcinogen. Atrazine can also be absorbed into the body through inhalation and through the skin and digestive tract. It is moderately toxic to humans and mammals, causing abdominal pain, diarrhea, and vomiting. Although the production and use of atrazine have been controlled to a certain extent, its use is not completely banned and it tends to remain in the environment for a long time. Therefore, accurate and precise monitoring technologies and methods are crucial for the analysis, research, and early warning of atrazine in aquatic environments and soils. Reliable and stable sampling and measurement technologies are crucial not only for assessing the environmental risks of atrazine but also for understanding its environmental behavior.

[0003] Currently, the main method for detecting triazine pesticides in the environment, such as atrazine, is to collect environmental samples through active sampling methods and transport them back to the laboratory. The samples are then prepared into a state that can be measured on the instrument through pretreatment techniques such as filtration, extraction, concentration, and volume adjustment. However, the active sampling method requires the collection of a large number of water or soil samples, and the samples need to be refrigerated. Water samples need to undergo filtration, SPE column enrichment, elution and other treatment processes. The pretreatment of soil samples is more complicated. It is necessary to first use a suitable organic solvent to extract the atrazine adsorbed in the soil, and then enrich, elute and filter to adjust the volume to meet the instrument injection requirements. These processes are not only very cumbersome, but also prone to errors. In addition, for atrazine in soil, the general solvent extraction method cannot determine the biologically effective concentration, which is more scientifically meaningful for risk assessment.

[0004] The biggest advantage of passive sampling techniques over active sampling techniques is that they can measure the time-averaged concentration of pollutants in water bodies, better capture concentration fluctuations of pollutants in water, and are simple to operate, saving time and effort. No tedious sample pretreatment steps are required before measurement, and the introduction of errors is relatively small. The diffusion gradient in thin films (DGT) technology mainly uses the principle of free diffusion (Fick's first law). By studying the gradient diffusion of the target in the diffusion layer and its buffering kinetics, it obtains information on the (biologically) effective state content and spatial distribution of the target in the environmental medium, the ionic-complexed state binding kinetics, and the solid-liquid exchange kinetics. Since its invention, DGT technology was first applied to the detection of metal cations in water environments. Since then, after improvements and expansions by a large number of researchers, the targets that can be measured by DGT technology have expanded from conventional metal cations to precious metals, organic metals, oxidizing anions, radioactive substances, nutrients, organic matter, and rare earth elements. A DGT device consists of a stationary layer (i.e., an adsorption membrane, also known as a stationary phase), a diffusion layer (diffusion membrane and filter membrane), and a jacket that anchors these three membranes. Target ions diffuse through the diffusion layer and are subsequently captured by the adsorption membrane, forming a linear gradient distribution within the diffusion layer. A key measure of the effectiveness of DGT technology is its ability to accurately and quantitatively determine the concentration of the target ion in the environment and its available state (the ability to rapidly exchange the target ion into solution). It is generally believed that the factors that influence DGT's ability to measure target concentration and available state primarily include the adsorption efficiency of the adsorption membrane, the pore size of the diffusion membrane, and the dynamic exchange of various forms within the diffusion membrane. Therefore, the study of adsorption membranes has long been a key focus of DGT technology. Adsorption membranes are generally made of an adsorbent material embedded in a gel. Their ability to measure target ions depends on the type of adsorbent material. Currently, various types of stationary phases are used for DGT determination, including single stationary phases, composite stationary phases, and liquid-phase adsorption phases.

[0005] Chelex-100 resin, XAD series resins, or HLB resins are all typical single-fixing materials and are the most mature adsorption materials. XAD series resins utilize macroporous adsorption, while HLB resins are anion-cation equilibrium resins with an ion exchange adsorption mechanism. Laboratory testing has shown good adsorption of triazine pesticides such as atrazine. However, they suffer from low capacity. Furthermore, field conditions differ from laboratory characterization conditions, with various impurities present in both water and soil. Triazine pesticides such as atrazine are particularly prevalent in heavily polluted field environments, such as pesticide production plants or heavily contaminated sites and their surrounding waters. Therefore, when measuring triazine pesticides such as atrazine in the field, the DGT capacity has been found to be further reduced compared to laboratory results, leading to significant deviations in the results due to exceeding the DGT capacity. Furthermore, some low concentrations of atrazine cannot be detected. Summary of the Invention

[0006] 1. Problem to be solved

[0007] In view of the problem of large deviation in the results of sampling and detection of triazine pesticides in water bodies using existing sampling technologies, the present invention provides a method and device for determining triazine pesticides, which can particularly solve the above-mentioned problem caused by field sampling.

[0008] In addition, the method and device for determining triazine pesticides provided by the present invention can further solve the problem that low-concentration triazine pesticides cannot be detected, and are particularly suitable for solving the sampling of low-concentration triazine pesticides in field environments.

[0009] 2. Technical solution

[0010] Traditional adsorption materials such as Chelex-100 resin, XAD series resins, or HLB resins generally have good adsorption effects on triazine pesticides such as atrazine under laboratory conditions, but they have low capacity. When measuring triazine pesticides such as atrazine in actual field environments, it was found that the DGT determination capacity was further reduced compared to laboratory results, resulting in significant deviations in the measurement results due to exceeding the DGT capacity.

[0011] In addition, the inventors also found in actual applications that when using high-performance liquid chromatography-secondary mass spectrometry to detect the eluate, there would be an increase in the baseline, an increase in impurity peaks, and a decrease in instrument sensitivity; ultimately, the detection limit of the DGT method was affected, reducing its sensitivity, resulting in some low-concentration atrazine being unable to be detected; in response to this problem, the inventors conducted repeated studies and found that it was mainly related to the presence of substances such as fatty acids, organic acids, and chlorophyll in the water body.

[0012] Based on the above, the present invention provides the following technical solutions:

[0013] [1] In a first aspect of the present invention, a device for determining triazine pesticides is provided, wherein the device is a DGT device, and the DGT device comprises: a diffusion layer, an impurity filtering layer, and a fixed layer; wherein:

[0014] The diffusion layer includes a diffusion membrane and a filter membrane;

[0015] The impurity filtering layer is a membrane containing ethylenediamine-N-propyl bonded silica gel;

[0016] The fixed layer is an adsorption film containing carbon nanotubes.

[0017] [1.1] According to any embodiment of the first aspect of the present invention, the triazine pesticide assay device, wherein the adsorption membrane containing carbon nanotubes is based on an agarose membrane, and the carbon nanotubes are distributed in the agarose membrane;

[0018] In a further optimized solution, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10-30 nm and a length of 1-2 μm.

[0019] Based on this, in some embodiments of the present invention, the carbon nanotubes can be prepared by experimental means or obtained commercially, but they need to be pretreated before being used to prepare the adsorption film. The pretreatment method is as follows:

[0020] Methanol washing: Add carbon nanotubes to methanol solvent. The nanotubes are light and need to be fully shaken and soaked. Centrifuge and remove the supernatant to obtain a precipitated solid. The volume-to-mass ratio of the methanol solvent to the carbon nanotubes is 7:(3-5) mL / g.

[0021] Ultrapure water cleaning: Add pure water to the sedimented solid, shake it, centrifuge it, remove the supernatant, and repeat three times.

[0022] [1.2] According to the triazine pesticide assay device of any embodiment of the first aspect of the present invention, the adsorption film containing carbon nanotubes is prepared by the following method:

[0023] (1) Mixing water, agar powder, and pretreated carbon nanotubes, and mixing them by ultrasound, vibration, etc.; and heating to boiling to make them as uniform as possible to obtain a carbon nanotube agar solution;

[0024] (2) The carbon nanotube agar solution was injected into the gap between two glass plates sandwiched between U-shaped Teflon sheets, and the bubbles between the glass plates were squeezed out. The glass plates were placed horizontally and cooled at room temperature for 50 to 80 minutes, and the solution in the glass plates solidified to form an adsorption film.

[0025] [1.3] In the triazine pesticide determination device according to any embodiment of the first aspect of the present invention, the mass ratio of the agar powder, the pretreated carbon nanotubes, and the pure water is 1:(8-15):50.

[0026] [1.4] According to any embodiment of the first aspect of the present invention, the triazine pesticide assay device, wherein the membrane containing ethylenediamine-N-propyl bonded silica gel is based on an agarose membrane, and the ethylenediamine-N-propyl bonded silica gel is distributed in the agarose membrane;

[0027] Among them, in a further optimized solution, the ethylenediamine-N-propyl bonded silica gel needs to be pretreated before being used for adsorption film preparation. The pretreatment method is as follows:

[0028] Methanol cleaning: Add ethylenediamine-N-propyl bonded silica gel to methanol solvent and shake and soak;

[0029] Ultrapure water cleaning: Then use pure water to continue cleaning the ethylenediamine-N-propyl bonded silica gel;

[0030] The pretreated ethylenediamine-N-propyl bonded silica gel has a particle size of 30 to 40 μm.

[0031] [1.5] According to the triazine pesticide assay device of any embodiment of the first aspect of the present invention, the membrane containing ethylenediamine-N-propyl bonded silica gel is prepared as follows:

[0032] (1) Mixing water, agar powder, and pretreated ethylenediamine-N-propyl bonded silica gel, and mixing them by ultrasound, vibration, etc.; and heating to boiling to make it as uniform as possible to obtain an ethylenediamine-N-propyl bonded silica gel agar solution;

[0033] (2) Inject the agar solution of ethylenediamine-N-propyl bonded silica gel into the gap between two glass plates sandwiched between U-shaped Teflon sheets, squeeze out the bubbles between the glass plates, place the glass plates horizontally and cool them at room temperature for 50 to 80 minutes, and the solution in the glass plates solidifies to form a film.

[0034] [1.6] In the triazine pesticide determination device according to any embodiment of the first aspect of the present invention, the mass ratio of the agar powder, the pretreated ethylenediamine-N-propyl bonded silica gel and the pure water is 1:(8-15):50.

[0035] [1.7] According to the triazine pesticide assay device of any embodiment of the first aspect of the present invention, the membrane containing ethylenediamine-N-propyl bonded silica gel has a thickness of 0.3 to 0.5 mm;

[0036] The adsorption film containing carbon nanotubes has a thickness of 0.3 to 0.5 mm.

[0037] [1.8] The triazine pesticide assay device according to any embodiment of the first aspect of the present invention, wherein the DGT device further comprises a housing having a base and a lid, wherein the lid has a water inlet window;

[0038] A filter membrane, a diffusion membrane, a membrane containing ethylenediamine-N-propyl bonded silica gel, and an adsorption membrane containing carbon nanotubes are sequentially stacked between the lid with a window and the base;

[0039] The filter membrane is a PES (polyethersulfone) filter membrane;

[0040] The diffusion membrane is an agar diffusion membrane.

[0041] [1.9] According to any embodiment of the first aspect of the present invention, the DGT device is used to sample triazine pesticides in water;

[0042] It can also be used for sampling triazine pesticides in soil.

[0043] [2] In a second aspect of the present invention, a method for determining triazine pesticides is provided, comprising the following steps:

[0044] 1) The DGT device is placed in the liquid to be tested, and the liquid to be tested passes through the filter membrane, the diffusion membrane, the membrane containing ethylenediamine-N-propyl bonded silica gel, and the adsorption membrane containing carbon nanotubes in sequence to sample triazine pesticides;

[0045] 2) After sampling, the adsorption membrane in the DGT device is removed and eluted with an eluent to obtain an eluate;

[0046] 3) High performance liquid chromatography-tandem mass spectrometry (HPLC-MS / MS) was used to determine the concentration of triazine pesticides in the eluate.

[0047] [2.1] According to the method for determining triazine pesticides in any embodiment of the second aspect of the present invention, the eluent is a mixture of methanol and ammonia water, wherein the ammonia water is chromatographic grade ammonia water, and the added volume ratio of ammonia water is 10% based on the mixture.

[0048] [2.2] According to the method for determining triazine pesticides in any embodiment of the second aspect of the present invention, the water to be tested contains triazine pesticides, fatty acids, organic acids, and chlorophyll;

[0049] The concentration of the triazine pesticide is between 0.005 and 500 mg / L;

[0050] The concentrations of the fatty acids, organic acids and chlorophyll are lower than 15 mg / L.

[0051] [2.3] According to any embodiment of the second aspect of the present invention, the triazine pesticide is determined by the method, wherein the triazine pesticide includes atrazine.

[0052] Beneficial effects

[0053] (1) The device provided by the present invention is based on gradient diffusion thin film (DGT) technology, which uses an adsorption film prepared from carbon nanotubes as a fixed membrane and can effectively increase the adsorption capacity of atrazine in water and soil;

[0054] The adsorption membrane containing carbon nanotubes is based on an agarose membrane with carbon nanotube particles distributed on its surface. The carbon nanotubes are very small and can be evenly distributed within the membrane matrix, making their distribution more uniform than that of activated carbon, XAD, and HLB resin adsorption membranes. Furthermore, they can provide more adsorption sites for triazine pesticides, resulting in strong adsorption ability and a large adsorption capacity. Tests have shown that the adsorption capacity of the adsorption membrane prepared with carbon nanotubes is 3.3 times and 2.1 times greater than that of the adsorption membrane prepared with XAD18 resin or HLB resin, respectively.

[0055] At the same time, the DGT device adds a layer of membrane containing ethylenediamine-N-propyl bonded silica gel between the diffusion membrane and the adsorption membrane. The membrane containing ethylenediamine-N-propyl bonded silica gel can selectively adsorb impurities such as organic acids, fatty acids, chlorophyll in water without adsorbing triazine pesticides.

[0056] (2) The method for determining atrazine in water and soil provided by the present invention uses an adsorption film prepared from carbon nanotubes as a fixed film, which can effectively increase the adsorption capacity of atrazine in water and soil;

[0057] Compared with general activated carbon adsorption membranes, adsorption membranes containing carbon nanotubes have a larger adsorption capacity, and the carbon nanotubes are more evenly distributed in the adsorption membrane, which has better anti-interference ability when sampling in complex field environments;

[0058] At the same time, the DGT device adds a layer of ethylenediamine-N-propyl bonded silica gel between the diffusion membrane and the adsorption membrane, which can effectively reduce the impurities such as organic acids, fatty acids, and chlorophyll adsorbed by the adsorption membrane during field environmental sampling;

[0059] It can effectively solve the problems of increased baseline, increased impurity peaks and decreased instrument sensitivity when using high performance liquid chromatography-secondary mass spectrometry to detect the eluate; it can minimize the impact on the detection limit of the DGT method, improve its sensitivity, and realize the detection of low-concentration triazine pesticides.

[0060] It is particularly suitable for the treatment of outdoor water bodies containing a sum of fatty acids, organic acids and chlorophyll concentrations of 2 to 7 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Schematic diagram of the structure of the DGT device used in the embodiment of the present invention;

[0062] Figure 2 This is a diagram showing the adsorption effect of atrazine at different pH values ​​using a DGT device in Example 3 of the present invention;

[0063] Figure 3 This is a diagram showing the adsorption effect of atrazine at different ion concentrations using a DGT device in Example 4 of the present invention;

[0064] In the figure: 1. Base; 2. Adsorption membrane; 3. Impurity filter layer; 4. Diffusion membrane; 5. Filter membrane; 6. Lid. DETAILED DESCRIPTION

[0065] The present disclosure may be more readily understood by reference to the following description in conjunction with the accompanying drawings and examples, all of which constitute a part of this disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions, or parameters described and / or illustrated herein. Further, the terms used herein are for the purpose of describing specific embodiments by way of example only and are not intended to be limiting unless otherwise indicated.

[0066] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically not included, each separate embodiment is considered to be combinable with any other embodiment, and the combination is considered to represent another different embodiment. Conversely, for the sake of simplicity, various features of the present disclosure described in the context of a single embodiment may also be provided individually or in any sub-combination. Finally, although a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or sub-structure itself may also be considered to be an independent embodiment.

[0067] Unless otherwise indicated, it should be understood that each individual element in a list and each combination of individual elements in that list will be interpreted as a different embodiment. For example, a list of embodiments expressed as "A, B, or C" should be interpreted to include embodiments "A," "B," "C," "A or B," "A or C," "B or C," or "A, B, or C."

[0068] In this disclosure, the singular forms of the articles "a," "an," and "the" also include the corresponding plural reference, and a reference to a specific value includes at least that specific value unless the context clearly dictates otherwise. Thus, for example, a reference to "a substance" is a reference to at least one of that substance and equivalents thereof.

[0069] Terms including ordinal numbers such as "first" and "second" may be used to explain various components or fluids, but these components and fluids are not limited by these terms. Therefore, without departing from the teachings of the present disclosure, these terms are only used to distinguish the component / fluid from another component / fluid.

[0070] When items are described by using the conjunction terms "... and / or..." etc., the description should be understood to include any one and all combinations of one or more of the associated listed items.

[0071] In general, the use of the term "about" indicates an approximate value that can vary depending on the desired properties obtained by the disclosed subject matter and will be interpreted in a context-dependent manner based on function. Therefore, one of ordinary skill in the art will be able to interpret a certain degree of difference on a case-by-case basis. In some cases, the number of important figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about". In other cases, a gradient in a range of values ​​can be used to determine the range of differences allowed by the term "about". Further, all ranges in this disclosure are inclusive and combinable, and reference to a value stated in a range includes every value within that range.

[0072] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; and the terms used herein include any and all combinations of one or more of the associated listed items.

[0073] The present invention is further described below in conjunction with specific embodiment, but embodiment does not limit the present invention in any form.Unless otherwise specified, the reagent, method and equipment adopted in the present invention are conventional reagents, methods and equipment in the art.The essential characteristics of the present invention and remarkable effect can be reflected from the following examples, and described embodiment is a part of embodiment of the present invention, rather than whole embodiment, therefore, they do not limit the present invention in any way, and those skilled in the art make some non-essential improvements and adjustments based on the content of the present invention, all belong to protection scope of the present invention.

[0074] The DGT device used in the following specific examples is as follows:

[0075] like Figure 1 As shown, the DGT device consists of a base 1, a fixing layer, an impurity filtering layer, a diffusion layer and a cover 6.

[0076] The fixed layer is an adsorption film 2 containing carbon nanotubes;

[0077] The impurity filtering layer is a membrane 3 containing ethylenediamine-N-propyl bonded silica gel;

[0078] The diffusion layer includes a diffusion membrane 4 and a filter membrane 5; wherein the diffusion membrane 4 is an agar diffusion membrane; the filter membrane 5 is a PES filter membrane;

[0079] The base 1 and the cover 6 are made of acrylonitrile-butadiene-styrene copolymer.

[0080] The adsorption film containing carbon nanotubes is prepared by the following steps:

[0081] (1) cleaning and soaking carbon nanotubes with methanol, and then washing with ultrapure water for later use; the carbon nanotubes have a diameter of 10-30 nm and a length of 1-2 μm;

[0082] (2) mixing agar powder, carbon nanotubes (wet weight) and pure water in a mass ratio of 1:8:50, shaking thoroughly and heating the solution to boiling to obtain a carbon nanotube agar solution;

[0083] (3) The prepared carbon nanotube agar solution was injected into the gap between two glass plates sandwiched between U-shaped Teflon sheets, and the bubbles between the glass plates were squeezed out. The glass plates were placed horizontally and cooled at room temperature for 80 minutes. The solution in the glass plates solidified to form a carbon nanotube adsorption film.

[0084] Finally, an adsorption film is obtained, which takes agarose film as a matrix and has carbon nanotubes distributed on the surface of the agarose film.

[0085] The adsorption membrane of this embodiment can be used to adsorb atrazine.

[0086] The PSA-containing membrane used is prepared through the following steps:

[0087] (1) Pretreatment of ethylenediamine-N-propyl bonded silica gel;

[0088] Methanol cleaning: Add ethylenediamine-N-propyl bonded silica gel to methanol solvent, shake and sonicate until completely immersed, soak, centrifuge, and remove the supernatant to obtain a precipitated solid; the volume mass ratio of the methanol solvent to the ethylenediamine-N-propyl bonded silica gel is 7:5 mL / g;

[0089] Ultrapure water cleaning: Add pure water to the sedimented solid, shake it, centrifuge it, remove the supernatant, and repeat three times;

[0090] Pretreated ethylenediamine-N-propyl bonded silica gel, with a particle size of 30 to 40 μm;

[0091] (2) Mix agar powder, prepared ethylenediamine-N-propyl bonded silica gel and pure water in a certain mass ratio, shake well and heat to boiling to form a uniform ethylenediamine-N-propyl bonded silica gel agar suspension; the mass ratio of the agar powder, pretreated ethylenediamine-N-propyl bonded silica gel and pure water is 1:8:50.

[0092] (3) The prepared carbon nanotube agar suspension was injected into the gap between two glass plates sandwiched between U-shaped Teflon sheets, and the bubbles between the glass plates were squeezed out. The glass plates were placed horizontally and cooled at room temperature for 50 to 80 minutes. The solution in the glass plates solidified to form a film containing PSA.

[0093] Example 1

[0094] In this embodiment, the carbon nanotube adsorption membrane is used as a binding membrane in the DGT technology to detect atrazine in the water body to be tested. The specific detection steps are as follows:

[0095] (1) Assembly of DGT device: The adsorption membrane 2 containing carbon nanotubes, the membrane 3 containing ethylenediamine-N-propyl bonded silica gel, the diffusion membrane 4 and the filter membrane 5 are sequentially stacked between the DGT base and the cover with a window to form a device as shown in FIG. Figure 1 The DGT device shown, wherein the base and the cover of the DGT device are made of acrylonitrile-butadiene-styrene copolymer;

[0096] (2) Placement of the DGT device: The DGT device in step (1) is placed in fully stirred water containing atrazine to be tested, and is generally placed for 1 to 15 days. In this embodiment, the placement time is 7 days.

[0097] (3) Recovery and elution of the adsorption film 2: After removing the DGT device from the water to be tested, rinse the surface dirt of the device with pure water, then take out the adsorption film 2 containing carbon nanotubes, place it in a glass bottle, add an eluent and ultrasonically treat it to obtain the eluate;

[0098] The eluent is a mixture of methanol and ammonia water, wherein the ammonia water is chromatographic grade ammonia water, and the added volume ratio of the ammonia water is 10% based on the mixture.

[0099] (4) Determination of atrazine: The concentration of atrazine in the eluate obtained in step (3) was determined by high performance liquid chromatography-tandem mass spectrometry.

[0100] (5) Calculation of atrazine adsorption amount: The adsorption amount of atrazine on the adsorption film 2 was calculated according to the following formula (I):

[0101] M=C e (V g +V e ) / f e (I)

[0102] Where, M is the amount of atrazine adsorbed on the adsorption film 2, in ng; C e is the molar concentration of atrazine in the eluate, in ng / mL; V g is the volume of the adsorption film, in mL; V e is the volume of the eluent in mL; f e is the elution efficiency of atrazine, which is obtained by eluting an adsorption membrane with a known amount of atrazine adsorption;

[0103] According to Fick's first diffusion law, the DGT concentration was converted using the following formula (II) to calculate the atrazine concentration in water.

[0104] C DGT =M*Δ g / (D*A*t)(II)

[0105] Where C DGT is the concentration of atrazine in water, in ng / mL; Δ g is the sum of the thickness of the diffusion membrane, impurity filter layer and filter membrane, in cm; D is the diffusion coefficient of atrazine in the impurity filter layer and diffusion membrane, in cm 2 / s; A is the window area of ​​the DGT device, unit is cm 2; t is the placement time of the DGT device, in seconds.

[0106] Example 2

[0107] In this embodiment, the carbon nanotube adsorption membrane is used as a binding membrane in the DGT technology to determine the presence of atrazine in the soil to be tested. The specific detection steps are as follows:

[0108] (1) Assembly of DGT device: The adsorption membrane 2 containing carbon nanotubes, the membrane 3 containing ethylenediamine-N-propyl bonded silica gel, the diffusion membrane 4 and the filter membrane 5 are sequentially stacked between the DGT base and the cover with a window to form a device as shown in FIG. Figure 1 The DGT device shown, wherein the base and the cover of the DGT device are made of acrylonitrile-butadiene-styrene copolymer;

[0109] (2) Placement of the DGT device: Adjust the soil to be tested to a moisture content of 100% with pure water. Place the soil slurry in a glass Petri dish. Carefully apply a small amount of soil slurry to the window of the DGT device prepared in step (1). With the device window facing downward, screw it into the soil slurry in the Petri dish to ensure full contact.

[0110] (3) Recovery and elution of adsorption film 2: After removing the DGT device from the water body to be tested, rinse the dirt on the surface of the device with pure water, then remove the carbon nanotube adsorption film, place it in a glass bottle, add eluent (a mixture of methanol and ammonia water), and then ultrasonically treat it to obtain the eluate.

[0111] (4) Determination of atrazine: The concentration of atrazine in the eluate obtained in step (3) was determined by high performance liquid chromatography-tandem mass spectrometry.

[0112] (5) Calculation of atrazine adsorption amount: The adsorption amount of atrazine on the adsorption film 2 was calculated according to the following formula (I):

[0113] M=C e (V g +V e ) / f e (I)

[0114] Where, M is the amount of atrazine adsorbed on the adsorption film 2, in ng; C e is the molar concentration of atrazine in the eluate, in ng / mL; V g is the volume of the adsorption film, in mL; V e is the volume of the eluent in mL; f e is the elution efficiency of atrazine, which is obtained by eluting an adsorption membrane with a known amount of atrazine adsorption;

[0115] According to Fick's first diffusion law, the DGT concentration was converted using the following formula (II) to calculate the atrazine concentration in water.

[0116] C DGT =M*Δ g / (D*A*t)(II)

[0117] Where C DGT is the concentration of atrazine in water, in ng / mL; Δ g is the sum of the thickness of the diffusion membrane, impurity filter layer and filter membrane, in cm; D is the diffusion coefficient of atrazine in the impurity filter layer and diffusion membrane, in cm 2 / s; A is the window area of ​​the DGT device, unit is cm 2 ; t is the placement time of the DGT device, in seconds.

[0118] (6) Determination of atrazine in soil: The soil slurry in the culture dish was collected, dried, and the atrazine in it was extracted using acetonitrile and tested on a machine.

[0119] (7) Compare the atrazine concentration measured by DGT with the atrazine concentration in soil and obtain a stable ratio.

[0120] Example 3

[0121] In this example, the DGT technique was used to determine the effect of atrazine in water at different pH values, wherein the atrazine concentration in the water to be tested was 20 μg / L, and the pH values ​​of the aqueous solutions to be tested were 3.02, 5.04, 6.95, 8.34, and 9.42, respectively.

[0122] like Figure 2 As shown, the atrazine concentration C calculated according to the formula DGT The actual atrazine concentration C in the measured solution solu The ratio is between 0.9 and 1.1, indicating that the pH of water has no obvious effect on the determination of DGT.

[0123] Example 4

[0124] This embodiment is basically the same as Example 4, with the only difference being that in step (2) of determining atrazine in water using a DGT device in this embodiment, the DGT device is placed in fully stirred water containing atrazine and sodium chloride for 24 hours, wherein the concentration of atrazine in the water to be tested is 20 μg / L, and the ion concentrations (in terms of NaCl) of the aqueous solutions to be tested are 0.1, 1, 10, 100, and 500 mmol / L, respectively.

[0125] like Figure 3 As shown, the atrazine concentration C calculated according to the formula DGTThe actual atrazine concentration C in the measured solution solu The ratio is between 0.9 and 1.1, indicating that the ionic strength of water has no significant effect on the determination of DGT.

[0126] Comparative Example 1

[0127] This comparative example is basically the same as Example 1, except that there are two types of adsorption films described in this comparative example:

[0128] The first type: using agarose membrane as the matrix, with activated XAD18 resin distributed in the agarose membrane;

[0129] The second type: using agarose membrane as the matrix, with activated HLB resin distributed in the agarose membrane;

[0130] The third type: using agarose membrane as the matrix, with activated carbon particles distributed in the agarose membrane, and the activated carbon particle size is 40-60μm;

[0131] The preparation method of the adsorption film is the same as that of the adsorption film containing carbon nanotubes in the present invention.

[0132] Attachment tests were conducted on water bodies containing atrazine, and the results showed that the adsorption capacity of the adsorption membrane prepared using carbon nanotubes was 3.3 times, 2.1 times, and 1.8 times higher than that of the adsorption membrane prepared using XAD18 macroporous resin, HLB resin, and activated carbon particles, respectively.

[0133] Table 1. Adsorption capacity of atrazine by three different adsorption membranes

[0134] Adsorption film XAD18 HLB activated carbon carbon nanotubes Effective adsorption capacity (μg) 16.12 25.34 29.56 53.21

[0135] Comparative Example 2

[0136] This comparative example provides a traditional DGT device (DGT-2), which has only three parts: an adsorption membrane 2, a diffusion membrane 4, and a filter membrane 5. The adsorption membrane 2, the diffusion membrane 4, and the filter membrane 5 are the same as those in Example 1 (the DGT device in Example 1 is named DGT-1);

[0137] At the same time, this comparative example also provides a DGT device (DGT-3) with a different adsorption membrane (the adsorption membrane is activated carbon), and the impurity filtering layer 3, the diffusion membrane 4 and the filter membrane 5 are the same as those in Example 1;

[0138] DGT-1, DGT-2, and DGT-3 were placed in the same wild water body to collect atrazine. In addition, it should be noted that through testing, the water body also contains chlorophyll, fat, organic acid, etc., and the sum of the contents of the three is calculated to be 15 mg / L.

[0139] During sampling applications, it was discovered that under complex field conditions, impurities such as fatty acids and organic acids in the DGT-2 environment easily enter the adsorption membrane and subsequently enter the eluent. This can interfere with the instrument's detection sensitivity during the injection process, thereby affecting the DGT method's detection limit. After theoretical analysis and experiments, the inventors ultimately discovered that adding an impurity filter layer containing ethylenediamine-N-propyl bonded silica gel, which can adsorb a variety of fatty acids and organic acids, behind the diffusion membrane can effectively prevent interfering substances in the natural environment from entering the adsorption gel. This effectively improves the DGT method's detection limit. The specific research is as follows:

[0140] (1) Two DGT devices, DGT-1 and DGT-2, were assembled, one with an impurity filtration layer and the other without. The adsorption membranes of both devices contained carbon nanotubes.

[0141] and the DGT device DGT-3 with an impurity filtration layer, the adsorption membrane is an adsorption membrane containing activated carbon;

[0142] (2) Placement of the DGT device: Take water samples from the field and bring them back to the laboratory. Contaminate the water samples with different concentrations of the atrazine internal standard substance: atrazine-D5 (to make the concentrations in the water 1, 3, 5, 7, and 10 μg / L, respectively). Place the DGT in the water and shake it for 24 hours.

[0143] (3) Recovery and elution of the resin adsorption film: The specific operation is the same as in Example 1;

[0144] (4) Determination of atrazine-D5: Determine the concentration of atrazine D-5 in the eluate obtained in step (3);

[0145] (5) On-machine testing to test whether the two DGTs can be accurately detected under different water conditions.

[0146] Table 2. Detection capability of DGT with and without impurity filter layer at different atrazine concentrations (unit: μg / L)

[0147] Actual concentration 1.03 3.25 4.95 7.33 11.20 DGT-1 0.87 3.15 5.05 7.05 10.47 DGT-2 ND 1.21 4.57 7.14 10.34 DGT-3 ND ND 4.32 6.81 10.45

Claims

1. A device for determining triazine pesticides in field soil, characterized in that: The device is a DGT device, which includes: a diffusion layer, an impurity filtering layer, and a fixed layer; The diffusion layer includes a diffusion membrane and a filter membrane; The impurity filtration layer is a membrane containing ethylenediamine -N- propyl bonded silica gel; the membrane containing ethylenediamine -N- propyl bonded silica gel, with an agarose membrane as a matrix, distributed in the agarose membrane ethylenediamine -N- propyl bonded silica gel; The fixed layer is an adsorption film containing carbon nanotubes; the adsorption film containing carbon nanotubes is based on an agarose film, and the carbon nanotubes are distributed in the agarose film; The adsorption film containing carbon nanotubes is prepared by the following method: (1) Pure water, agar powder, and carbon nanotubes are mixed and heated to boiling to obtain an agar solution of carbon nanotubes; the mass ratio of the agar powder, carbon nanotubes, and pure water is 1: (8-15): 50; the diameter of the carbon nanotubes is 10-30 nm; (2) Pour the carbon nanotube agar solution into the film-forming apparatus, remove the bubbles, and cool it at room temperature until the solution forms a film; The membrane containing ethylenediamine-N-propyl bonded silica gel is prepared in the following manner: (1) Pure water, agar powder, and pretreated ethylenediamine-N-propyl bonded silica gel are mixed; and heated to boiling to make it as uniform as possible to obtain an agar solution of ethylenediamine-N-propyl bonded silica gel; the mass ratio of the agar powder, ethylenediamine-N-propyl bonded silica gel, and pure water is 1: (8-15): 50; (2) Inject the agar solution of ethylenediamine-N-propyl bonded silica gel into the film-forming device, remove the bubbles, and cool it at room temperature until the solution forms a film.

2. The device for measuring triazine pesticides in site soil according to claim 1, characterized in that: The carbon nanotubes need to be pretreated before being used to prepare the adsorption film. The pretreatment method is as follows: Methanol cleaning: Add carbon nanotubes into methanol solvent and soak them; Ultrapure water cleaning: Use pure water to clean the soaked carbon nanotubes; The ethylenediamine-N-propyl bonded silica gel needs to be pretreated before being used for membrane preparation. The pretreatment method is as follows: Methanol cleaning: Add ethylenediamine-N-propyl bonded silica gel to methanol solvent for soaking; Ultrapure water cleaning: Use pure water to clean the ethylenediamine-N-propyl bonded silica gel after soaking.

3. The device for measuring triazine pesticides in field soil according to any one of claims 1 to 2, characterized in that: The particle size of the pretreated ethylenediamine-N-propyl bonded silica gel is 30 ~ 40 μm.

4. A method for determining triazine pesticides in site soil, characterized in that: The measurement is performed using the measuring device according to any one of claims 1 to 3, comprising the following steps: 1) Place the DGT device in a soil slurry containing the triazine pesticide to be tested. The liquid passes through a filter membrane, a diffusion membrane, a membrane containing ethylenediamine-N-propyl bonded silica gel, and an adsorption membrane containing carbon nanotubes in sequence to sample the triazine pesticide. 2) After sampling, the adsorption membrane in the DGT device is removed and eluted with an eluent to obtain an eluate; 3) High performance liquid chromatography-tandem mass spectrometry (HPLC-MS / MS) was used to determine the concentration of triazine pesticides in the eluate.

5. A method for determining triazine pesticides in site soil according to claim 4, characterized in that: The soil slurry to be tested contains triazine pesticides, fatty acids, organic acids and chlorophyll; The concentration of the triazine pesticide is between 0.005 and 500 mg / L; The concentrations of the fatty acids, organic acids and chlorophyll are lower than 15 mg / L.

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