Mass spectrometry ionization element for adsorbing amide herbicide, preparation method and application thereof

Abstract

The application discloses an adsorption ionization mass spectrometry element for amide herbicides, a preparation method and application, and comprises: a conductive substrate; and an extraction layer formed on at least part of the surface of the conductive substrate, wherein the extraction layer is formed by a covalent organic framework material composed of a repeating unit shown in formula I. According to the adsorption ionization mass spectrometry element provided by the embodiment of the application, the extraction layer coating is uniform, has a porous structure, a large specific surface area, can selectively enrich a plurality of trace amide herbicides, has strong adsorption, and the mass spectrometry ionization element can be directly subjected to mass spectrometry detection through ionization ionization, without a chromatographic separation process, so that the detection process is simple, fast, and has low background noise, high sensitivity and high accuracy.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and more specifically, to an adsorption mass spectrometry ionization element for amide herbicides, its preparation method, and its application. Background Technology

[0002] Amide herbicides are a class of highly selective and efficient herbicides. Due to their broad spectrum, low price, ease of use, and good weed-control effects, they are widely used and have become the second most used herbicide. Currently, the global usage of amide herbicides exceeds 170,000 tons per year. In China, the usage of metolachlor and acetochlor reaches as high as 4,700 tons and 10,000 tons respectively, and their usage continues to increase. However, amide herbicides are highly water-soluble, have low soil adsorption rates, poor biodegradability, and long biological half-lives, making them easily persistent in the soil. The most common amide herbicides include metolachlor, metolachlor, and acetochlor. In the soil, they can be converted into ethyl sulfonic acid products (such as ethanesulfonic acid, ESA) at concentrations higher than their parent compounds. These products are even more water-soluble, have longer degradation times, and are highly toxic. Coupled with the excessive use of amide herbicides globally, this further contributes to their accumulation in the soil, posing a serious threat to the ecological environment, food safety, and human health. In addition, amide herbicides have low concentrations in food, and food matrix interference significantly affects the sensitivity of detection, necessitating effective sample pretreatment techniques for efficient separation and purification.

[0003] Therefore, enrichment and separation elements for amide herbicides require further research. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide an adsorption ionization mass spectrometry element, wherein the extraction layer of the element has a porous structure and a large specific surface area, and has a broad-spectrum and efficient enrichment effect on amide herbicides, and is particularly suitable for the extraction, enrichment and detection of trace amide herbicides in complex matrices.

[0005] According to one aspect of the present invention, an adsorption ionization mass spectrometry element is provided. According to an embodiment of the present invention, the adsorption ionization mass spectrometry element comprises: a conductive substrate; and an extraction layer formed on at least a portion of the surface of the conductive substrate, the extraction layer being formed of a covalent organic framework material composed of repeating units as shown in Formula I.

[0006]

[0007] The adsorption-ionization mass spectrometry element according to embodiments of the present invention has a uniform extraction layer coating, a porous structure, and a large specific surface area, which can selectively enrich a variety of trace amide herbicides. It has strong adsorption capacity. Furthermore, this mass spectrometry ionization source element can directly perform mass spectrometry detection through ionization without the need for chromatographic separation. The detection steps are simple and fast, and the background noise, sensitivity, and accuracy are low.

[0008] In addition, the adsorption ionization mass spectrometry element according to the above embodiments of the present invention may also have the following additional technical features:

[0009] According to an embodiment of the present invention, the conductive substrate is formed of acidified stainless steel.

[0010] According to an embodiment of the present invention, the conductive substrate is in the shape of an isosceles triangle, wherein the base of the isosceles triangle is no greater than 2 cm and the height is no greater than 3 cm. Preferably, the height is 1.5-2.5 cm and the base is 0.5-1.5 cm.

[0011] According to an embodiment of the present invention, the thickness of the conductive substrate is 0.1-0.5 mm.

[0012] According to an embodiment of the present invention, the contact angle of the mass spectrometry ionization source element is 69-70°.

[0013] According to another aspect of the present invention, the present invention provides a method for preparing the aforementioned adsorption ionization mass spectrometry element. According to an embodiment of the present invention, the method includes: providing a conductive substrate; acidifying the conductive substrate to obtain an acidified conductive substrate; first contacting the acidified conductive substrate with an organic solution containing an amino monomer, and subjecting it to ultrasonic and oscillation treatment to allow the amino monomer to coat the surface of the acidified conductive substrate, obtaining a first reaction mixture; and second contacting the organic solution containing an aldehyde monomer with the first reaction mixture to perform a Schiff base reaction, thereby obtaining the adsorption ionization mass spectrometry element.

[0014] According to the preparation method of the present invention, the extraction layer coating of the prepared adsorption ionization mass spectrometry element is uniform, has a large specific surface area, has a porous structure, and has strong stability. It can selectively enrich a variety of trace amide herbicides in large throughput, has strong adsorption capacity, and the preparation method is mild, simple in steps, and easy to industrialize.

[0015] According to an embodiment of the present invention, the amino monomer is N,N,N',N'-tetra(p-aminophenyl)p-phenylenediamine (TAPPD).

[0016] According to an embodiment of the present invention, the aldehyde monomer is 5'-(4-formyl-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1'-:3',1”-terphenyl]-4,4”-dicarboxaldehyde (FHDTD). According to an embodiment of the present invention, the ratio of the amino monomer to 1,4-dioxane is 0.09-0.13 mol: 10 mL.

[0017] According to an embodiment of the present invention, the solvent for the aldehyde monomer is 1,4-dioxane, in a ratio of 0.13-0.17 mol: 5 mL.

[0018] According to an embodiment of the present invention, the molar ratio of the amino monomer to the aldehyde monomer is 1:1-1.8, preferably 1.1:1.5.

[0019] According to an embodiment of the present invention, the catalyst for the Schiff base reaction is acetic acid.

[0020] According to an embodiment of the present invention, the amount of acetic acid used is 500 μL, based on 0.1-0.15 mmol of the amino monomer.

[0021] According to an embodiment of the present invention, the organic solvent of both the organic solution containing amino monomers and the organic solution containing aldehyde monomers is 1,4-dioxane.

[0022] According to an embodiment of the present invention, the duration of the ultrasound is 15-25 minutes.

[0023] According to an embodiment of the present invention, the conditions for the oscillation treatment are a temperature of 55-65°C, a rotation speed of 180-250 rpm, and a time of 40-80 min.

[0024] According to an embodiment of the present invention, the conditions for the Schiff base reaction are a temperature of 55-65°C, a rotation speed of 180-250 rpm, and a time of 40-80 min.

[0025] According to another aspect of the present invention, an integrated separation and ionization mass spectrometry device is provided. According to an embodiment of the present invention, the device includes: the aforementioned adsorption ionization mass spectrometry element; an open-type mass spectrometry detector including an inlet disposed opposite to the tip of the adsorption ionization mass spectrometry element; and a high-voltage power supply connected to the adsorption ionization mass spectrometry element.

[0026] According to the integrated separation and ionization mass spectrometry device of the present invention, the aforementioned adsorption-ionization mass spectrometry element is directly connected to a high-voltage power supply. Under the action of high voltage, the target analyte on the adsorption-ionization mass spectrometry element is ionized by the elution solvent. The generated ions directly enter the mass spectrometer through the mass spectrometer inlet to obtain the acquired signal. No chromatographic separation process is required. The detection steps are simple and fast. It can simultaneously detect multiple trace amide herbicides, has a large detection throughput, and low background noise. It is especially suitable for the enrichment and detection of multiple amide herbicides in complex matrices, such as food samples.

[0027] According to an embodiment of the present invention, the distance between the injection port and the tip of the adsorption ionization mass spectrometry element is 3-8 mm, preferably 5 mm.

[0028] According to another aspect of the present invention, a method for enriching amide herbicides is provided. According to an embodiment of the present invention, the method includes: extracting a sample to be tested to obtain a test solution; and subjecting the test solution to a vortexing contact treatment with a aforementioned adsorption ionization mass spectrometry element to obtain a mass spectrometry ionization source element with the amide herbicides adsorbed on its surface. Therefore, this method can specifically enrich multiple trace amounts of amide herbicides, exhibiting strong adsorption capacity, which is beneficial for fully enriching target substances, such as amide herbicides in food; furthermore, the enrichment method of the embodiments of the present invention is simple to operate, requires no complex sample pretreatment process, and has high sample extraction efficiency.

[0029] According to an embodiment of the present invention, the extraction processing time is 15-25 min, preferably 20 min.

[0030] According to another aspect of the present invention, the present invention provides a method for qualitative / quantitative detection of amide herbicides. According to an embodiment of the present invention, the method includes: enriching amide herbicides in a test sample using the aforementioned method for enriching amide herbicides to obtain a mass spectrometry ionization source element on which the amide herbicides are adsorbed; and detecting the mass spectrometry ionization source element on which the amide herbicides are adsorbed using the aforementioned integrated separation and ionization mass spectrometry device to perform qualitative / quantitative detection of the amide herbicides.

[0031] According to the qualitative / quantitative detection method of the present invention, the aforementioned adsorption ionization mass spectrometry element can specifically enrich multiple trace amide herbicides in food. It has strong adsorption capacity, which is beneficial for fully enriching amide herbicides in complex matrices. Furthermore, the adsorption ionization mass spectrometry element for enriching amide herbicides is directly connected to a high-voltage power supply. Under the action of high voltage, the target analyte on the mass spectrometry ionization source element is ionized under the action of the elution solvent. The generated ions directly enter the mass spectrometer through the inlet of the mass spectrometer detector to obtain the acquired signal. No chromatographic separation process is required. The detection steps are simple and fast. It can simultaneously detect multiple trace amide herbicides, with high detection throughput, low background noise, and high detection sensitivity. It is especially suitable for high-throughput, rapid, and accurate analysis of trace amide herbicides.

[0032] According to an embodiment of the present invention, the detection conditions of the integrated separation and ionization mass spectrometry device are as follows: high voltage power supply voltage: 2.0-4.0kV, preferably 3.0kV; ionization elution solvent: a methanol solution containing (0.05-0.2)% formic acid, preferably a methanol solution containing 0.1% formic acid.

[0033] According to an embodiment of the present invention, the detection conditions of the mass spectrometer detector are as follows: Detection mode: Multiple reaction monitoring (MRM); Nebulizer gas pressure: 55 psi; Auxiliary gas pressure: 50 psi; Curtain gas pressure: 20 psi; Ion source temperature: 550 °C; Residence time: 100 ms.

[0034] According to an embodiment of the present invention, the volume of the ionization elution solvent is 10-30 μL, preferably 20 μL.

[0035] According to embodiments of the present invention, the amide herbicide is at least one selected from Alachlor, Metolachor, Acetochlor, Pretilachlor, Butachlor, Napropamide, or Propachlor.

[0036] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0037] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0038] Figure 1A schematic diagram of a mass spectrometry element according to an embodiment of the present invention is shown, wherein A is a scanning electron microscope image of a solid substrate; B is a scanning electron microscope image of an acid-treated solid substrate; and C is a scanning electron microscope image of COF(TAPPD-FHDTD)-SSS.

[0039] Figure 2 The material characterization diagram of the mass spectrometry element according to an embodiment of the present invention is shown, wherein (a) is an infrared spectrum; (b) is a thermogravimetric analysis curve; (c) is the C1s of the X-ray photoelectron spectrum; (d) is the N1s of the X-ray photoelectron spectrum; (e) and (f) are the contact angles of the stainless steel substrate and the COF(TAPPD-FHDTD)-SSS, respectively.

[0040] Figure 3 The diagram shows the results under different enrichment and ionization conditions according to embodiments of the present invention;

[0041] Figure 4 A schematic diagram showing the enrichment capacity of the mass spectrometry element prepared in Example 1 according to an embodiment of the present invention for seven amide herbicides is displayed.

[0042] Figure 5 A schematic diagram of the process for preparing a mass spectrometry element and using the mass spectrometry element to extract and analyze the analyte compound is shown according to an embodiment of the present invention;

[0043] Figure 6 A schematic diagram showing the results of mass spectrometry detection according to an embodiment of the present invention is displayed. Detailed Implementation

[0044] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0045] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0046] According to one aspect of the present invention, an adsorption-ionization mass spectrometry element is provided. The adsorption-ionization mass spectrometry element according to embodiments of the present invention has a uniform extraction layer coating with a porous structure and a large specific surface area, enabling targeted enrichment of various trace amide herbicides. It exhibits strong adsorption capacity. Furthermore, this mass spectrometry ionization source element can directly perform mass spectrometry detection via ionization, eliminating the need for chromatographic separation. The detection procedure is simple, fast, and features low background noise, high sensitivity, and high accuracy.

[0047] To facilitate understanding of the adsorption ionization mass spectrometry element in the embodiments of the present invention, the adsorption ionization mass spectrometry element is explained and described herein according to the embodiments of the present invention, which includes:

[0048] conductive substrate

[0049] According to an embodiment of the present invention, the conductive substrate is formed of acidified stainless steel. The inventors have discovered that when paper or wood is used as a solid substrate for open-substrate electrospray mass spectrometry analysis, the poor conductivity of paper or wood leads to high background interference after applying high voltage, resulting in unstable mass spectrometry signals. In contrast, stainless steel substrates, due to their excellent conductivity, allow for direct application of high voltage, resulting in high ionization efficiency and further simplifying experimental procedures.

[0050] According to an embodiment of the present invention, the conductive substrate is an isosceles triangle. Thus, the stainless steel sheet is cut into a triangle, making it suitable for multiple applications, not only as a standard extraction plate but also for open-circuit electrospray mass spectrometry (ESMS). When the extraction element is used in open-circuit EMS, it is fixed at the horizontal front end of the mass spectrometer inlet. By applying a high voltage, the spray solvent elutes the target analyte adsorbed on the extraction element, ionizing it at the tip and forming a Taylor cone spray, which directly enters the mass spectrometer for detection. According to an embodiment of the present invention, the base of the isosceles triangle is no greater than 2 cm, and the height is no greater than 3 cm. This ensures the formation of a Taylor cone spray at the apex of the triangle. Otherwise, if the angle is too small or too large, the surface tension of the eluting solvent will hinder spray formation. Furthermore, a height of 1.5-2.5 cm and a base of 0.5-1.5 cm result in a better Taylor cone spray formation.

[0051] According to an embodiment of the present invention, the thickness of the conductive substrate is 0.1-0.5 mm. This thickness allows the liquid to more quickly wet the entire surface, forming a uniform liquid film, which is beneficial for producing a stable and uniform spray. Furthermore, it enhances the electric field strength and stability, accelerates heat transfer and evaporation rates, thereby improving the accuracy and repeatability of the analysis.

[0052] Extraction layer

[0053] According to an embodiment of the present invention, the extraction layer is formed on at least a portion of the surface of a conductive substrate, and the extraction layer is formed of a covalent organic framework material composed of repeating units as shown in Formula I.

[0054] According to an embodiment of the present invention, the contact angle of the mass spectrometry ionization source element is 69-70°. Therefore, the ionization element has good hydrophilicity, which is more conducive to enriching the target analyte in aqueous solution.

[0055] According to another aspect of the present invention, the present invention provides a method for preparing the aforementioned adsorption ionization mass spectrometry element. According to the preparation method of the embodiments of the present invention, the prepared adsorption ionization mass spectrometry element has a uniform extraction layer coating, a large specific surface area, a porous structure, and strong stability. It can specifically enrich a variety of trace amide herbicides in large throughput, exhibiting strong adsorption capacity. Furthermore, the preparation method is mild, simple in steps, and easy for industrial production.

[0056] To facilitate understanding of the method for preparing the aforementioned adsorption ionization mass spectrometry element, the method is explained herein. According to an embodiment of the present invention, the method includes:

[0057] S100 provides a base

[0058] According to an embodiment of the present invention, a conductive substrate is provided. Thus, high voltage can be directly connected to the substrate, forming an electrospray through ionization.

[0059] S200 acidification treatment

[0060] According to an embodiment of the present invention, the conductive substrate is acidified to obtain an acidified conductive substrate. This slightly dissolves the passivation film through acidification, forming a micro-roughened surface, increasing the specific surface area, and thereby improving the mechanical adhesion and chemical bonding strength of the coating or plating.

[0061] S300 Ultrasonic Vibration

[0062] According to an embodiment of the present invention, the acidified conductive substrate is first contacted with an organic solution containing an amino monomer, and then subjected to ultrasonic and vibration treatment so that the amino monomer is coated on the surface of the acidified conductive substrate to obtain a first reaction mixture.

[0063] According to an embodiment of the present invention, the ultrasonication time is 15-25 min. According to an embodiment of the present invention, the vibration treatment conditions are a temperature of 55-65°C, a rotation speed of 180-250 rpm, and a time of 40-80 min. This facilitates the complete dissolution of the amino monomer in the organic solvent and ensures sufficient contact between the reactants for the reaction.

[0064] S400 Schiff base reaction

[0065] According to an embodiment of the present invention, an organic solution containing an aldehyde monomer is brought into a second contact with the first reaction mixture to perform a Schiff base reaction in order to obtain the adsorption ionization mass spectrometry element.

[0066] According to embodiments of the present invention, the amino monomer is N,N,N',N'-tetra(p-aminophenyl)p-phenylenediamine (TAPPD). According to embodiments of the present invention, the aldehyde monomer is 5'-(4-formyl-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1'-:3',1”-terphenyl]-4,4”-dicarboxaldehyde (FHDTD). The chemical structure of amide herbicides, containing N and O atoms, can act as hydrogen bond acceptors under certain conditions. Based on this, the inventors selected aldehyde monomers containing hydroxyl groups and designed and synthesized hydroxyl-functionalized COF materials, which can enhance the adsorption of amide herbicides through hydrogen bonding.

[0067] According to an embodiment of the present invention, the ratio of the amino monomer to 1,4-dioxane is 0.09-0.13 mol: 10 mL. This concentration is advantageous in ensuring a high binding rate of the amino monomer to the active sites of the stainless steel substrate, while also reducing unnecessary waste caused by excessive use of raw materials.

[0068] According to an embodiment of the present invention, the solvent for the aldehyde monomer is 1,4-dioxane, with a ratio of 0.13-0.17 mol: 5 mL. This concentration is advantageous in ensuring a high reaction conversion rate between the aldehyde and amino monomers, thereby maximizing the coverage of the synthesized extraction layer on the stainless steel substrate surface, while also avoiding unnecessary waste due to excessive use of raw materials.

[0069] According to embodiments of the present invention, the molar ratio of the amino monomer to the aldehyde monomer is 1:1-1.8, preferably 1.1:1.5. Therefore, at this ratio, the resulting product exhibits a more regular and ordered molecular structure, reducing the occurrence of side reactions.

[0070] According to an embodiment of the present invention, the catalyst for the Schiff base reaction is acetic acid. Therefore, the catalytic effect is good and the reaction efficiency is high.

[0071] According to an embodiment of the present invention, based on 0.1-0.15 mmol of the amino monomer, the amount of acetic acid used is 500 μL. Therefore, this volume ratio range allows for sufficient contact between the components in the reaction system and ensures a suitable concentration of the catalyst acetic acid, thereby guaranteeing that the reaction proceeds at a relatively ideal rate.

[0072] According to embodiments of the present invention, the organic solvents of both the organic solution containing the amino monomer and the organic solution containing the aldehyde monomer are 1,4-dioxane. Therefore, the amino and aldehyde monomers have high solubility, enabling uniform dispersion of the monomers in the solution, reducing the problem of uneven reaction caused by excessively high or low local concentrations, and thus improving the yield and quality stability of the product.

[0073] According to an embodiment of the present invention, the Schiff base reaction conditions are a temperature of 55-65°C, a rotation speed of 180-250 rpm, and a reaction time of 40-80 min. Therefore, the reaction is fast and efficient.

[0074] According to another aspect of the present invention, an integrated separation and ionization mass spectrometry device is provided. According to an embodiment of the present invention, the device includes: the aforementioned adsorption ionization mass spectrometry element; an open-type mass spectrometry detector including an inlet disposed opposite to the tip of the adsorption ionization mass spectrometry element; and a high-voltage power supply connected to the adsorption ionization mass spectrometry element.

[0075] According to the integrated separation and ionization mass spectrometry device of the present invention, the aforementioned adsorption-ionization mass spectrometry element is directly connected to a high-voltage power supply. Under the action of high voltage, the target analyte on the adsorption-ionization mass spectrometry element is ionized by the elution solvent. The generated ions directly enter the mass spectrometer through the mass spectrometer inlet to obtain the acquired signal. No chromatographic separation process is required. The detection steps are simple and fast. It can simultaneously detect multiple trace amide herbicides, has a large detection throughput, and low background noise. It is especially suitable for the enrichment and detection of multiple amide herbicides in complex matrices, such as food samples.

[0076] According to an embodiment of the present invention, the distance between the injection port and the tip of the adsorption ionization mass spectrometry element is 3-8 mm, preferably 5 mm. If the distance between the ionization element and the MS inlet is too close, the elution solvent will be ejected into the mass spectrometer, damaging the instrument; while if the distance is too far, the elution solvent will not easily enter the mass spectrometer, resulting in a decrease in signal intensity. The aforementioned distance is beneficial for the elution solvent to fully enter the mass spectrometer and avoids damage to the instrument, with a distance of 5 mm being more effective.

[0077] According to another aspect of the present invention, a method for enriching amide herbicides is provided. According to an embodiment of the present invention, the method includes: extracting a sample to be tested to obtain a test solution; and subjecting the test solution to a vortexing contact treatment with a aforementioned adsorption ionization mass spectrometry element to obtain a mass spectrometry ionization source element with the amide herbicides adsorbed on its surface. Therefore, this method can specifically enrich multiple trace amounts of amide herbicides, exhibiting strong adsorption capacity, which is beneficial for fully enriching target substances, such as amide herbicides in food; furthermore, the enrichment method of the embodiments of the present invention is simple to operate, requires no complex sample pretreatment process, and has high sample extraction efficiency.

[0078] According to an embodiment of the present invention, the extraction time is 15-25 min, preferably 20 min. Thus, because the analyte in the sample solution and the analyte adsorbed on the enrichment element reach a dynamic equilibrium, rapid extraction of amide herbicides is achieved, wherein the extraction time of 20 min results in a larger adsorption capacity.

[0079] According to another aspect of the present invention, the present invention provides a method for qualitative / quantitative detection of amide herbicides. According to an embodiment of the present invention, the method includes: enriching amide herbicides in a test sample using the aforementioned method for enriching amide herbicides to obtain a mass spectrometry ionization source element on which the amide herbicides are adsorbed; and detecting the mass spectrometry ionization source element on which the amide herbicides are adsorbed using the aforementioned integrated separation and ionization mass spectrometry device to perform qualitative / quantitative detection of the amide herbicides.

[0080] According to the qualitative / quantitative detection method of the present invention, the aforementioned adsorption ionization mass spectrometry element can specifically enrich multiple trace amide herbicides in food. It has strong adsorption force, which is beneficial for fully enriching amide herbicides in complex matrices. Furthermore, the adsorption ionization mass spectrometry element for enriching amide herbicides is directly connected to a high-voltage power supply. Under the action of high voltage, the target analyte on the mass spectrometry ionization source element is ionized under the action of the elution solvent. The generated ions directly enter the mass spectrometer through the inlet of the mass spectrometer detector to obtain the acquired signal. No chromatographic separation process is required. The detection steps are simple and fast. It can simultaneously detect multiple trace amide herbicides, with high detection throughput, low background noise, and high detection sensitivity. It is especially suitable for high-throughput, rapid, and accurate analysis of trace amide herbicides. In some embodiments, mass spectrometry detection can be completed in just 1.5 minutes.

[0081] According to an embodiment of the present invention, the detection conditions of the integrated separation and ionization mass spectrometry device are as follows: high voltage power supply voltage: 2.0–4.0 kV, preferably 3.0 kV; ionization elution solvent: a methanol solution containing (0.05–0.2)% formic acid, preferably a methanol solution containing 0.1% formic acid. Therefore, when the voltage is 2.0–4.0 kV, the signal response is strong, and the signal response is even better when the voltage is 3.0 kV; the signal response is high when using methanol containing (0.05–0.2)% formic acid as the elution solvent, and the signal response is even higher when using a methanol solution containing 0.1% formic acid. Furthermore, selecting the above voltage and elution solvent is beneficial for improving the detection signal of the analyte, resulting in higher detection sensitivity and accuracy.

[0082] According to an embodiment of the present invention, the detection conditions of the mass spectrometer detector are as follows: Detection mode: Multiple reaction monitoring (MRM); Nebulizer gas pressure: 55 psi; Assist gas pressure: 50 psi; Curtain gas pressure: 20 psi; Ion source temperature: 550℃; Residence time: 100 ms. Therefore, under the above conditions, the detection of carbamate pesticides exhibits high target response values, low background noise, and high detection sensitivity and accuracy, making it particularly suitable for the rapid and precise analysis of trace amounts of amide herbicides.

[0083] According to an embodiment of the present invention, the volume of the ionization elution solvent is 10-30 μL, preferably 20 μL. This volume of ionization elution solvent not only facilitates thorough elution of the target analyte but also avoids solvent waste.

[0084] According to embodiments of the present invention, the amide herbicide is at least one selected from Alachlor, Metolachor, Acetochlor, Pretilachlor, Butachlor, Napropamide, or Propachlor.

[0085] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and should not be construed as limiting the present invention.

[0086] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products, such as those purchased from Sigma.

[0087] The materials and reagents used in the embodiments of this invention are shown in Table 1.

[0088] Table 1

[0089]

[0090] Example 1

[0091] The method for preparing adsorption ionization mass spectrometry elements according to embodiments of the present invention is described in reference to... Figure 5 Using N,N,N',N'-tetra(p-aminophenyl)p-phenylenediamine (TAPPD) as the amino monomer and 5'-(4-formyl-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1'-:3',1”-terphenyl]-4,4”-dicarboxaldehyde (FHDTD) as the aldehyde monomer, a solid substrate coating material, i.e., an enrichment element, was prepared. The specific method is as follows:

[0092] 1. Disperse or dissolve the acidified solid substrate (6 pieces) and N,N,N',N'-tetra(p-aminophenyl)p-phenylenediamine (53 mg, 0.11 mmol) in 10 mL of 1,4-dioxane in a conical flask (200 mL) and sonicate for 20 min.

[0093] 2. The mixture was then transferred to a water bath shaker at 60°C and shaken at 210 rpm for 1 h. 5'-(4-formyl-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1'-:3',1”-terphenyl]-4,4”-dicarboxaldehyde (65 mg, 0.15 mmol) was dissolved in 5 mL of 1,4-dioxane and slowly added to the above system.

[0094] 3. Acetic acid (500 μL) was added dropwise to the conical flask as a catalyst to accelerate the reaction. The mixture was shaken in a water bath at 210 rpm for 4 hours at 60 °C to obtain a yellow solid substrate coating material.

[0095] 4. The obtained yellow solid substrate coating material was washed alternately with methanol and acetonitrile until the supernatant was clear. Finally, the material was stored in acetonitrile, as shown in the following reaction formula:

[0096]

[0097] Example 2

[0098] Detailed characterization experiments were conducted on the solid substrate coating material (COF(TAPPD-FHDTD)-SSS) prepared in Example 1 to demonstrate the successful preparation of the material and its excellent physicochemical properties. The specific details are as follows:

[0099] 1. The surface morphology of the solid substrate, the acid-treated solid substrate, and COF(TAPPD-FHDTD)-SSS was characterized, demonstrating the successful synthesis of COFs on the solid substrate surface. Results are as follows: Figure 1 As shown, Figure 1 As shown in (a), the surface of the solid substrate is smooth, but after sulfuric acid treatment, the surface exhibits a rough and uneven texture; as Figure 1 (b) This facilitates the subsequent coating of COF materials; when COFs are used as a coating on a solid substrate, the surface exhibits relatively uniformly distributed spherical particles, such as... Figure 1 (c)

[0100] 2. FT-IR spectroscopy further confirmed the successful synthesis of COFs, as shown in the following results. Figure 2 (a). Compared to amino and aldehyde monomers, -NH2 at 3347 cm⁻¹ in the FT-IR spectra of COFs. -1 The NH stretch band and -CHO at 1656cm -1 The C=O extension band at this location weakens or disappears. Furthermore, at 1625cm... -1 A newly observed peak appeared, which can be attributed to the formation of C=N bonds in COFs. The results indicate that COFs were successfully synthesized via the Schiff base reaction.

[0101] 3. The thermal stability of COFs in the range of 40-800℃ was studied using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and the results are as follows. Figure 2 As shown in (b), the slight weight loss near 100°C is due to solvent evaporation. When the temperature reaches near 400°C, the material weight decreases significantly, corresponding to the exothermic peak in the DTA curve. This phenomenon is thought to be caused by the degradation and carbonization of the COFs. These results confirm the good thermal stability of COFs in the 0-400°C range.

[0102] 4. For example Figure 2 As shown in (c) and (d), the chemical composition of COFs was evaluated using X-ray photoelectron spectroscopy (XPS). In the COFs, the XPS (C1s) spectrum showed a C=C / CC bond at 283.84 eV and a C=N bond at 284.80 eV, while the XPS (N1s) spectrum showed peaks corresponding to a CN bond at 98.85 eV and a C=N bond at 398.12 eV, further confirming the successful synthesis of COF(TAPPD-FHDTD)-SSS.

[0103] 5. The hydrophobic properties of the solid substrate and the COF(TAPPD-FHDTD)-SSS surface were studied by contact angle measurement. The water contact angle of the solid substrate was 96.4°. Figure 2(e) indicates that it is hydrophobic. This can be attributed to the presence of an antioxidant oil film on the surface. After the COFs layer was coated, the contact angle was measured to be 87.1°. Figure 2 (f) indicates that COF(TAPPD-FHDTD)-SSS has a certain degree of hydrophilicity and can adsorb amide herbicides in aqueous solution.

[0104] Example 3

[0105] In this embodiment, reference Figure 5 The mass spectrometry detection parameters for amide herbicides in Astragalus membranaceus samples were optimized using the enrichment element from Example 1, as detailed below:

[0106] 1. Experimental Methods

[0107] (1) Extract the Astragalus membranaceus sample to obtain a solution. The specific operation is as follows:

[0108] First, prepare a 50mL centrifuge tube, weigh 1g of Astragalus powder and add 20mL of acetonitrile into it, vortex for 5min (1600rpm) to evenly disperse the Astragalus in the acetonitrile.

[0109] Secondly, it is ultrasonically treated for 10 minutes to transfer the pesticide components in Astragalus membranaceus into acetonitrile.

[0110] Then, the ultrasonically treated Astragalus-acetonitrile was centrifuged for 5 minutes (4℃, 8000 rpm) to separate the Astragalus and acetonitrile, and the supernatant was collected.

[0111] Finally, the supernatant was dried with nitrogen, reconstituted in 20 mL of ultrapure water, filtered through a 0.22 μm filter, and the filtrate was stored in a 4 °C refrigerator for later use.

[0112] (2) The amide herbicide was enriched to obtain the enriched product. The specific operation was as follows: take the above filtrate, add one enrichment element, vortex enrich for 30 minutes at 600 rpm, take it out and quickly wash the surface with deionized water to remove non-specific co-extractants.

[0113] (3) The enrichment element that has adsorbed the target analyte is detected by an integrated mass spectrometry ionization device. The analytical conditions of this device include: placing the enrichment element on the mass spectrometry detection platform, adjusting the tip of the enrichment element to be in the same straight line as the mass spectrometer inlet, and adjusting the tip of the enrichment element to be 5 mm away from the mass spectrometer inlet; then, adding 20 μL of methanol solution containing 0.1% formic acid to the surface of the enrichment element; then, turning on the high voltage power supply and applying a high voltage of 3.0 kV; the test solution moves towards the tip of the enrichment element, generating analyte ions at the tip and forming a spray, which enters the mass spectrometer for analysis.

[0114] Mass spectrometry conditions included: detection mode: multiple reaction monitoring (MRM); electrospray voltage (IS): 5500V; nebulizer gas pressure (GS1): 55psi; auxiliary gas pressure (GS2): 50psi; curtain gas pressure (CUR): 20psi; ion source temperature (TEM): 550℃; residence time (DT): 100ms.

[0115] 2. Experimental Results

[0116] (1) The optimized MRM mass spectrometry parameters of the seven amide herbicides are shown in Table 2, and the peak area of ​​the quantitative ions is used as the evaluation index.

[0117] Table 2:

[0118]

[0119]

[0120] Note: * indicates quantitative ions.

[0121] Mass spectrometry detection results as follows Figure 6 As shown, an analysis can be completed within 1.5 minutes, which is short.

[0122] Example 4

[0123] In this embodiment, the effects of extraction conditions such as sample enrichment time, pH value, and ionic strength, as well as ionization conditions such as applied voltage and elution solvent, on the detection results were studied. Taking the analysis of seven amide herbicides in Astragalus membranaceus samples as an example, seven spiked samples of the amide herbicides to be tested were prepared (spiking concentration: 20 μg / L), and analyzed in parallel three times using the mass spectrometry detection conditions of Example 2.

[0124] 1. Enrichment time optimization

[0125] Enrichment time is a crucial factor in the enrichment process. To obtain optimal extraction time, the effects of different extraction times (5, 10, 20, 30, 40, and 50 min) on the enrichment amount were investigated. The studies were performed in triplicate, and the enrichment amount was detected using the aforementioned detection steps. The results are as follows: Figure 3 As shown in (a), within the range of 5-20 min, the signal intensities of the seven amide herbicides increased with increasing extraction time. However, when the extraction time exceeded 20 min, the signal intensities of the analytes remained almost constant. This is mainly because the analytes in the sample solution and those adsorbed on the enrichment element reached a dynamic equilibrium, demonstrating that the extraction process of the enrichment element can be completed in a relatively short time. This indicates that the enrichment element has the potential for rapid analyte extraction. Therefore, an extraction time of 20 min is preferred to obtain a larger adsorption capacity.

[0126] 2. pH optimization

[0127] This embodiment investigated the effect of different enrichment pH values ​​(3, 5, 7, 9, 11) on the enrichment amount of Astragalus membranaceus samples. The experiment was performed in triplicate, and the results are as follows: Figure 3 As shown in (b), when the pH value is in the range of 3-7, the signal intensity increases with increasing pH value; however, as the enrichment pH value continues to increase, the signal intensity decreases. This may be because amide herbicides are easily hydrolyzed under strong acid or alkaline conditions, leading to a reduction in the amount of amide herbicides and thus affecting the enrichment of the analyte. Therefore, neutral pH is selected as the preferred condition to enrich more amide herbicides.

[0128] 3. Ion strength optimization

[0129] The ionic strength of the solution was studied by changing the concentration of sodium chloride. The experiment was performed in triplicate, and the results are as follows: Figure 3 As shown in (c). 0-12% NaCl was added to evaluate the effect of salt concentration. The recovery rate of amide herbicides decreased significantly with increasing NaCl concentration, which may be attributed to the increased solution viscosity inhibiting the mass transfer process. Therefore, NaCl was not added in subsequent experiments.

[0130] 4. Optimization of spray ionization conditions

[0131] Spray ionization conditions determine the concentration of target analytes eluted from enrichment elements and the detectable target analyte signals, playing a crucial role in open-field mass spectrometry analysis. This study investigated two experimental parameters: spray voltage and spray solvent, comparing the signal intensities of seven amide herbicides to determine optimal spray ionization conditions.

[0132] A. Spray voltage optimization

[0133] Spray voltage has a significant impact on the analyte signal in open-type mass spectrometry experiments. This study compares different voltages. When the voltage is too low, the analyte eluted by the eluent cannot be ionized, resulting in no detectable signal. However, when the voltage is too high, the spray velocity is too fast, preventing sufficient ionization of the target analyte and preventing the instrument from collecting all effective signals. The signal intensity of seven amide herbicides was detected by applying different voltages, with each voltage measured three times. The results are as follows: Figure 3 As shown in (d), the signal strength of all analytes increases with increasing applied voltage. The highest signal strength is achieved for most analytes at 3.0 kV, after which the signal strength decreases with further voltage increases. Therefore, 3.0 kV is the preferred voltage for obtaining stable and high signal strength for most compounds.

[0134] B. Spray solvent optimization

[0135] For spray solvents, not only is maximal elution of analytes adsorbed on the enrichment element required, but also high ionization efficiency for the analytes. To obtain higher signal intensities, the effects of methanol (MeOH), ethanol (EtOH), acetonitrile (ACN), and ethyl acetate (EA) as spray solvents on the signal intensity of amide herbicides were investigated, with three parallel analyses performed. The results are as follows: Figure 3 As shown in (e), methanol provides better elution. Subsequently, 0.1%, 0.2%, 0.3%, and 0.4% formic acid (FA) were added to methanol, and the results are as follows... Figure 3 As shown in (f), the results indicate that methanol containing 0.1% formic acid has better elution ability for the seven amide herbicides. Therefore, methanol containing 0.1% formic acid is preferred as the elution solvent.

[0136] 5. Detection limit and linear range of mass spectrometry detection methods

[0137] Seven standard solutions of amide herbicides at different concentrations were prepared using a blank Astragalus membranaceus matrix solution. Standard curves were obtained, and the LODs and LOQs of the method were investigated. The results are shown in Table 3. The linear range of the seven tested amide herbicides was 0.05-100 μg / kg, and the coefficient of determination (r) was [missing value]. 2 For concentrations greater than 0.99, LODs are 0.03-0.1 μg / kg, and LOQs are 0.1-0.4 μg / kg.

[0138] Table 3

[0139]

[0140] Example 5

[0141] In this embodiment, the enrichment capacity of the mass spectrometry element prepared according to the present invention was investigated. To study the enrichment capacity of the element, the adsorption efficiency of acid-treated solid substrates and COF(TAPPD-FHDTD)-SSS for seven amide herbicides was compared. Figure 4 As shown, when using acid-treated solid substrate extraction, the peak area range of the seven amide herbicides (20 μg / L) was 3.67 x 10⁻⁶. 5 ~1.87x10 7 When extracted using COF(TAPPD-FHDTD)-SSS, their peak areas are around 1.20 x 10⁻⁶. 7 ~3.16x10 8 Between 25.8 and 100.2 times that of acid-treated solid substrates, COF(TAPPD-FHDTD)-SSS showed a significant improvement in the enrichment capacity of this mass spectrometry element.

[0142] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0143] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An adsorption ionization mass spectrometry element, characterized in that, include: Conductive substrate; as well as An extraction layer is formed on at least a portion of the surface of a conductive substrate, the extraction layer being formed of a covalent organic framework material consisting of repeating units as shown in Formula I. 。 2. The adsorption ionization mass spectrometry element according to claim 1, characterized in that, The conductive substrate is formed of acidified stainless steel.

3. The adsorption ionization mass spectrometry element according to claim 1, characterized in that, The conductive substrate is in the shape of an isosceles triangle, with the base not exceeding 2 cm, the height not exceeding 3 cm, and the base being 0.5-1.5 cm.

4. The adsorption ionization mass spectrometry element according to claim 1, characterized in that, The thickness of the conductive substrate is 0.1-0.5 mm.

5. The adsorption ionization mass spectrometry element according to claim 1, characterized in that, The contact angle of the adsorption ionization mass spectrometry element is 69-70°.

6. A method for preparing the adsorption ionization mass spectrometry element according to any one of claims 1-5, characterized in that, include: Provide a conductive substrate; The conductive substrate is acidified to obtain an acidified conductive substrate; The acidified conductive substrate is first brought into contact with an organic solution containing amino monomers, and then subjected to ultrasonic and vibration treatment to coat the surface of the acidified conductive substrate with the amino monomers, thereby obtaining a first reaction mixture; and An organic solution containing an aldehyde monomer is brought into a second contact with the first reaction mixture to perform a Schiff base reaction in order to obtain the adsorption ionization mass spectrometry element.

7. The method according to claim 6, characterized in that, The amino monomer is N,N,N',N'-tetra(p-aminophenyl)p-phenylenediamine.

8. The method according to claim 7, characterized in that, The aldehyde monomer is 5'-(4-formyl-3-hydroxyphenyl)-3,3''-dihydroxy-[1,1'-:3',1''-terphenyl]-4,4''-dicarboxaldehyde.

9. The method according to claim 7, characterized in that, The ratio of the amino monomer to 1,4-dioxane is 0.09-0.13 mol: 10 mL.

10. The method according to claim 8, characterized in that, The solvent for the aldehyde monomer is 1,4-dioxane, in a ratio of 0.13-0.17 mol: 5 mL.

11. The method according to claim 8, characterized in that, The molar ratio of the amino monomer to the aldehyde monomer is 1:1-1.

8.

12. The method according to claim 11, characterized in that, The molar ratio of the amino monomer to the aldehyde monomer is 1.1:1.

5.

13. The method according to claim 6, characterized in that, The catalyst for the Schiff base reaction is acetic acid.

14. The method according to claim 13, characterized in that, The molar ratio of the amino monomer to the aldehyde monomer is based on 0.1-0.15 mmol of the amino monomer, and the amount of acetic acid used is 500 μL.

15. The method according to claim 6, characterized in that, The organic solvents of both the organic solution containing amino monomers and the organic solution containing aldehyde monomers are 1,4-dioxane.

16. The method according to claim 6, characterized in that, The ultrasound session lasted 15-25 minutes.

17. The method according to claim 6, characterized in that, The conditions for the oscillation treatment are a temperature of 55-65 ℃, a rotation speed of 180-250 rpm, and a time of 40-80 min.

18. The method according to claim 6, characterized in that, The Schiff base reaction conditions are a temperature of 55-65℃, a rotation speed of 180-250 rpm, and a time of 40-80 min.

19. A mass spectrometry device integrating separation and ionization, characterized in that, include: The adsorption ionization mass spectrometry element according to any one of claims 1-5; An open-type mass spectrometer detector, the open-type mass spectrometer detector including an injection port, the injection port being disposed opposite to the tip of the adsorption ionization mass spectrometer element; as well as A high-voltage power supply is connected to the adsorption ionization mass spectrometry element.

20. The apparatus according to claim 19, characterized in that, The distance between the injection port and the tip of the adsorption ionization mass spectrometry element is 3-8 mm.

21. The apparatus according to claim 20, characterized in that, The distance between the injection port and the tip of the adsorption ionization mass spectrometry element is 5 mm.

22. A method for enriching amide herbicides, characterized in that, include: The sample to be tested is extracted and processed to obtain the test solution; as well as The test solution is subjected to a oscillating contact treatment with the adsorption ionization mass spectrometry element according to any one of claims 1-5 in order to obtain a mass spectrometry ionization source element with the amide herbicide adsorbed on its surface.

23. The method according to claim 22, characterized in that, The extraction process takes 15-25 minutes.

24. The method according to claim 23, characterized in that, The extraction process takes 20 minutes.

25. A method for qualitative / quantitative detection of amide herbicides, characterized in that, include: The method for enriching amide herbicides according to any one of claims 22-24 is used to enrich the amide herbicides in the test sample in order to obtain a mass spectrometry ionization source element with the amide herbicides adsorbed on the surface. as well as The mass spectrometry source element on which the amide herbicide is adsorbed on the surface is detected by the separation and ionization integrated mass spectrometry device according to any one of claims 19-21, so as to perform qualitative / quantitative detection of the amide herbicide.

26. The method according to claim 25, characterized in that, Detection conditions of the integrated separation and ionization mass spectrometry device: High voltage power supply voltage: 2.0~4.0 kV; The ionization elution solvent is a methanol solution containing (0.05-0.2)% formic acid.

27. The method according to claim 26, characterized in that, Detection conditions of the integrated separation and ionization mass spectrometry device: High voltage power supply voltage: 3.0 kV; The ionization elution solvent is a methanol solution of 0.1% formic acid.

28. The method according to claim 19, characterized in that, The detection conditions of the mass spectrometer detector are as follows: Detection method: Multiple reaction monitoring (MRM); Nebulizer gas pressure: 55 psi; Auxiliary gas pressure: 50 psi; Air curtain pressure: 20 psi; Ion source temperature: 550 ℃; Dwell time: 100 ms.

29. The method according to claim 26, characterized in that, The volume of the ionization elution solvent is 10-30 μL.

30. The method according to claim 29, characterized in that, The volume of the ionization elution solvent is 20 μL.

31. The method according to claim 25, characterized in that, The amide herbicide is selected from at least one of metolachlor, isopropylmetolachlor, acetochlor, propachlor, butachlor, diltiazem, or chlorpyrifos.

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