Preparation and application of mass spectrometry ionization source elements for carbamate pesticide analysis

Abstract

This invention discloses the preparation and application of a dedicated mass spectrometry ionization source element for the analysis of carbamate pesticides. The mass spectrometry ionization source 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 is formed of a covalent organic framework material composed of repeating units as shown in Formula I. This mass spectrometry ionization source element has a uniform extraction layer coating, a porous structure, and a large specific surface area, enabling targeted high-throughput enrichment of various trace carbamate pesticides. It enriches a wide variety of carbamate pesticides and exhibits strong adsorption. 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 and fast, with low background noise, high sensitivity, and high accuracy. In addition, this mass spectrometry ionization source element is reusable, resulting in low operating costs.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and more specifically, to a separation and ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides, its preparation method, and its application. Background Technology

[0002] Liquid chromatography-tandem mass spectrometry (LC-MS / MS) is the standard method for detecting carbamate pesticides, enabling accurate trace detection. However, its complex pretreatment and long chromatographic separation time make it unsuitable for rapid detection. As timeliness, convenience, and accuracy of detection have become increasingly important, technologies such as enzyme-linked immunosorbent assay (ELISA), electrochemical sensors, near-infrared spectroscopy, and Raman spectroscopy have been developed for rapid on-site detection of carbamate pesticides. However, these technologies also suffer from drawbacks such as false positives, low repeatability, and poor sensitivity.

[0003] Therefore, solid-substrate mass spectrometry ionization sources and corresponding detection methods for the rapid detection of various carbamate pesticides in complex matrices need to be studied. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one object of this invention is to provide a separation and ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides. The extraction layer of this element has a porous structure and a large specific surface area, exhibiting broad-spectrum and efficient enrichment of carbamate pesticides, and is particularly suitable for the extraction, enrichment, and detection of trace carbamate pesticides in complex matrices.

[0005] According to one aspect of the present invention, an integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides is provided. According to an embodiment of the present invention, the mass spectrometry ionization source 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 mass spectrometry ionization source 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, high-throughput enrichment of various trace carbamate pesticides. It enriches a wide variety of carbamate pesticides, exhibits strong adsorption, and allows for direct mass spectrometry detection via ionization, eliminating the need for chromatographic separation. This results in a simple and rapid detection process with low background noise, high sensitivity, and high accuracy. Furthermore, the mass spectrometry ionization source element is reusable, leading to low operating costs.

[0008] In addition, the separation and ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides 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 stainless steel.

[0010] According to an embodiment of the present invention, the conductive substrate is in the shape of an isosceles triangle, the height of which 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 thickness of the extraction layer is 10-20 μm.

[0013] According to another aspect of the present invention, the present invention provides a method for preparing the aforementioned integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides. 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, followed by ultrasonic and oscillation treatment to coat the surface of the acidified conductive substrate with the amino monomer, 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 integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides.

[0014] According to the preparation method of the present invention, the extraction layer coating of the prepared mass spectrometry ionization source element is uniform, has a large specific surface area, a porous structure, and strong stability. It can selectively enrich a variety of trace carbamate pesticides in large throughput, has strong adsorption capacity, and the preparation method is mild, simple, and has good reproducibility of the extraction coating, which is convenient for industrial production.

[0015] According to an embodiment of the present invention, the amino monomer is 1,3,5-tris(4-aminophenoxy)benzene (TAPOB); and the aldehyde monomer is N,N,N',N'-tetra(4-aldehydephenyl)-1,4-phenylenediamine (BDTB).

[0016] According to an embodiment of the present invention, the concentration of the amino monomer is 1.5-3.5 mg / mL, preferably 2.5 mg / mL.

[0017] According to an embodiment of the present invention, the concentration of the aldehyde monomer is 5-7 mg / mL, preferably 6 mg / mL.

[0018] According to an embodiment of the present invention, the molar ratio of the amino monomer to the aldehyde monomer is 1-2:1, preferably 1.3:1.

[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, based on 1-1.5 mmol of the amino monomer, the amount of acetic acid used is 2 mL.

[0021] According to an embodiment of the present invention, the organic solvents of both the organic solution containing an amino monomer and the organic solution containing an aldehyde monomer are tetrahydrofuran. According to another aspect of the present invention, the present invention provides an integrated separation and ionization mass spectrometry device. According to an embodiment of the present invention, the device includes: the aforementioned integrated separation and ionization mass spectrometry ionization source element for the detection of trace carbamate pesticides; an open mass spectrometry detector including an inlet disposed opposite to the tip of the mass spectrometry ionization source element; and a high-voltage power supply connected to the mass spectrometry ionization source element.

[0022] According to the integrated separation and ionization mass spectrometry device of the present invention, the aforementioned mass spectrometry ionization substrate for enriching carbamate pesticides 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 mass spectrometer inlet to obtain the acquired signal, without the need for chromatographic separation process. The detection steps are simple and fast, and it can simultaneously detect multiple trace carbamate pesticides with high detection throughput and low background noise. It is especially suitable for complex matrices, such as the enrichment and detection of multiple carbamate pesticides in food samples.

[0023] According to another aspect of the present invention, a method for enriching carbamate pesticides 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 oscillating contact treatment with a aforementioned integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides, to obtain a mass spectrometry ionization source element with the carbamate pesticide adsorbed on its surface. Therefore, this method can specifically enrich multiple trace carbamate pesticides, exhibiting strong adsorption, which is beneficial for the sufficient enrichment of target substances, such as carbamate pesticides in food. Furthermore, the enrichment method of the embodiments of the present invention is simple to operate, requiring no complex sample pretreatment process, and has high sample extraction efficiency. In addition, the mass spectrometry ionization source element is reusable, resulting in low operating costs.

[0024] According to an embodiment of the present invention, the rotational speed of the oscillating contact treatment is 1700-1900 rpm, and the time is 5-15 minutes.

[0025] According to another aspect of the present invention, a method for qualitative / quantitative detection of carbamate pesticides is provided. According to an embodiment of the present invention, the method includes: enriching a sample of test carbamate pesticides using the aforementioned method for enriching carbamate pesticides to obtain a mass spectrometry ionization source element on which the carbamate pesticides are adsorbed; and detecting the mass spectrometry ionization source element on which the carbamate pesticides are adsorbed using the aforementioned integrated separation and ionization mass spectrometry device to perform qualitative / quantitative detection of the carbamate pesticides. Therefore, the aforementioned mass spectrometry ionization source element can specifically enrich multiple trace carbamate pesticides in food. It exhibits strong adsorption, which is beneficial for fully enriching carbamate pesticides in complex matrices. Furthermore, the mass spectrometry ionization source element for enriching carbamate pesticides is directly connected to a high-voltage power supply. Under the influence of the high voltage, the target analyte on the mass spectrometry ionization source element ionizes under the action of the elution solvent. The generated ions directly enter the mass spectrometer through the detector inlet to obtain the acquired signal, eliminating the need for chromatographic separation. The detection procedure is simple and fast, enabling the simultaneous detection of multiple trace carbamate pesticides. It boasts high throughput, low background noise, and high sensitivity, making it particularly suitable for high-throughput, rapid, and accurate analysis of trace carbamate pesticides. In addition, this mass spectrometry ionization source element is reusable, resulting in low detection costs.

[0026] 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: 3.5kV; ionization elution solvent: methanol solution.

[0027] 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: 30 psi; ion spray voltage: 4500 V; ion source temperature: 550 °C; residence time: 100 ms.

[0028] According to an embodiment of the present invention, the volume of the ionization elution solvent is 15-25 μL.

[0029] According to embodiments of the present invention, the carbamate pesticide is at least one selected from carbaryl, isoprocarb, fenofarad, bendioxon, dietofencarb, pirimicarb, propoxur, methiocarb, or methyl carbonate.

[0030] 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

[0031] 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:

[0032] Figure 1 The diagram shows a scanning electron microscope result according to an embodiment of the present invention, wherein A is the surface of a blank stainless steel substrate, B is the surface of a stainless steel substrate after acid treatment, C and D are the surfaces of the separation-ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides, E is the cross-section of the blank stainless steel substrate, and F is the cross-section of the separation-ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides.

[0033] Figure 2 A schematic diagram of energy dispersive spectroscopy (EDS) results according to an embodiment of the present invention is shown, wherein A represents the Fe element distribution, B represents the N element distribution, C represents the C element distribution, and D represents the O element distribution;

[0034] Figure 3 This diagram illustrates the result of reusing a mass spectrometry ionization source element according to an embodiment of the present invention.

[0035] Figure 4 A schematic diagram showing the results of optimizing extraction conditions according to an embodiment of the present invention is provided, wherein A represents the result of optimizing extraction time and B represents the result of optimizing extraction volume;

[0036] Figure 5 A schematic diagram showing the results of optimizing desorption conditions according to an embodiment of the present invention is provided, wherein A represents the voltage optimization result and B represents the extraction solvent optimization result;

[0037] Figure 6 A schematic flowchart of a method for preparing a separation and ionization integrated mass spectrometry ionization source element and using it for analysis and detection according to an embodiment of the present invention is shown. Detailed Implementation

[0038] 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.

[0039] In the description of this invention, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and do not require that this invention must be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0040] According to one aspect of the present invention, an integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides is provided. The mass spectrometry ionization source element according to embodiments of the present invention has a uniform extraction layer coating with a large specific surface area and a porous structure, enabling targeted enrichment of trace carbamate pesticides. It enriches a wide variety of carbamate pesticides and exhibits strong adsorption. 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 and fast, with low background noise, high sensitivity, and high accuracy. In addition, this mass spectrometry ionization source element is reusable, resulting in low operating costs.

[0041] To facilitate understanding of the mass spectrometry ionization source element in the embodiments of the present invention, the mass spectrometry ionization source element is explained and described herein according to the embodiments of the present invention. The mass spectrometry ionization source element includes:

[0042] conductive substrate

[0043] According to an embodiment of the present invention, the conductive substrate is formed of 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.

[0044] 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 that directly enters the mass spectrometer for detection. According to an embodiment of the present invention, the height of the isosceles triangle is 1.5-2.5 cm, and the base is 0.5-1.5 cm. This forms a Taylor cone spray at the tip of the triangle; otherwise, if the angle is too small or too large, the surface tension of the elution solvent will hinder spray formation.

[0045] 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.

[0046] Extraction layer

[0047] 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 comprises a covalent organic framework material composed of repeating units as shown in Formula I. Thus, the extraction layer has a large specific surface area, a porous structure, and is arranged in a granular aggregate form, enabling targeted enrichment of trace amounts of carbamate pesticides with strong adsorption capacity.

[0048] According to an embodiment of the present invention, the thickness of the extraction layer is 10-20 μm. This extraction layer thickness results in a shorter diffusion path between the functional particles or ligands on the porous membrane matrix and the liquid flow, leading to faster mass transfer, significantly shortened membrane adsorption separation time, and improved separation efficiency.

[0049] According to embodiments of the present invention, the carbamate pesticide is at least one selected from carbaryl, isoprocarb, fenofarad, bendioxon, dietofencarb, pirimicarb, propoxur, methiocarb, or methyl carbonate.

[0050] According to another aspect of the present invention, the present invention provides a method for preparing the aforementioned integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides. According to the preparation method of the embodiments of the present invention, the prepared mass spectrometry ionization source element has a uniform extraction layer coating, a large specific surface area, a porous structure, and strong stability. It can specifically enrich trace carbamate pesticides, exhibits strong adsorption, and the preparation method is mild, simple in steps, and has good reproducibility of the extraction coating, facilitating industrial production.

[0051] To facilitate understanding of the method for preparing the aforementioned separation and ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides, please refer to... Figure 6 The method is explained herein, and according to an embodiment of the present invention, the method includes:

[0052] S100 provides a base

[0053] 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.

[0054] S200 acidification treatment

[0055] 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.

[0056] S300 Ultrasonic Vibration

[0057] The acidified conductive substrate is first brought into contact with an organic solution containing amino monomers, followed by ultrasonic and agitation treatment to coat the surface of the acidified conductive substrate with the amino monomers, resulting in a first reaction mixture. This binds the amino monomers to the conductive substrate, facilitating the subsequent formation of a covalent organic framework polymer.

[0058] According to an embodiment of the present invention, the ultrasonication time is 15-25 minutes, the oscillation time is 0.5-1.5 hours, the temperature is 55-65°C, and the rotation speed is 190-210 rpm. This facilitates the complete dissolution of the amino monomer in the organic solvent and ensures sufficient contact between the reactants for the reaction.

[0059] S400 Schiff base reaction

[0060] An organic solution containing an aldehyde monomer and an acetic acid solution are brought into a second contact with the first reaction mixture to perform a Schiff base reaction, thereby obtaining the separation and ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides. Thus, through the Schiff base reaction, the aldehyde monomer polymerizes with the amino monomer on the conductive substrate to form a covalent organic framework (COF).

[0061] According to an embodiment of the present invention, the amino monomer is 1,3,5-tris(4-aminophenoxy)benzene; according to an embodiment of the present invention, the aldehyde monomer is N,N,N',N'-tetra(4-aldehydephenyl)-1,4-phenylenediamine. Thus, the rigid organic framework structure formed by the reaction of these two monomers has a specific stereogeometry and can form π-π conjugation and hydrogen bonding with the target analytes, enabling targeted simultaneous adsorption of nine carbamate target analytes.

[0062] According to an embodiment of the present invention, the concentration of the amino monomer is 1.5-3.5 mg / mL, preferably 2.5 mg / mL. This concentration is beneficial 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.

[0063] According to an embodiment of the present invention, the concentration of the aldehyde monomer is 5-7 mg / mL, preferably 6 mg / 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.

[0064] According to embodiments of the present invention, the molar ratio of the amino monomer to the aldehyde monomer is 1-2:1, preferably 1.3:1. At this ratio, the resulting product exhibits a more regular and ordered molecular structure, reducing the occurrence of side reactions.

[0065] 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.

[0066] According to an embodiment of the present invention, based on 1-1.5 mmol of the amino monomer, the amount of acetic acid used is 2 mL. 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.

[0067] According to embodiments of the present invention, the organic solvents for both the organic solution containing the amino monomer and the organic solution containing the aldehyde monomer are tetrahydrofuran. This results in high solubility of both the amino and aldehyde monomers, enabling uniform dispersion of the monomers in the solution, reducing inhomogeneity caused by excessively high or low local concentrations, and thereby improving the yield and quality stability of the product.

[0068] According to another aspect of the present invention, the present invention provides a separation-ionization integrated mass spectrometry device. According to an embodiment of the present invention, the device includes: the aforementioned separation-ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides; an open mass spectrometry detector including a sample inlet disposed opposite to the tip of the mass spectrometry ionization source element; and a high-voltage power supply connected to the mass spectrometry ionization source element.

[0069] According to the integrated separation and ionization mass spectrometry device of the present invention, the aforementioned mass spectrometry ionization substrate for enriching carbamate pesticides 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 mass spectrometer inlet to obtain the acquired signal, without the need for chromatographic separation process. The detection steps are simple and fast, and it can simultaneously detect trace amounts of carbamate pesticides. It has a high detection throughput and low background noise, and is especially suitable for complex matrices, such as the enrichment and detection of multiple types of carbamate pesticides in food samples.

[0070] According to another aspect of the present invention, a method for enriching carbamate pesticides 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 oscillating contact treatment with a aforementioned integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides, to obtain a mass spectrometry ionization source element with the carbamate pesticide adsorbed on its surface. Thus, the method can specifically enrich nine trace carbamate pesticides, exhibiting strong adsorption capacity, which is beneficial for fully enriching complex matrices, such as carbamate pesticides in food. Furthermore, the enrichment method of the embodiments of the present invention is simple to operate, requiring no complex sample pretreatment process, and has high sample extraction efficiency. In addition, the mass spectrometry ionization source element is reusable, resulting in low operating costs.

[0071] According to an embodiment of the present invention, the rotation speed of the oscillating contact treatment is 1700-1900 rpm, and the time is 5-15 minutes. This facilitates the full adsorption of carbamate pesticides in the test solution by the mass spectrometry ionization source element.

[0072] According to another aspect of the present invention, a method for qualitative / quantitative detection of carbamate pesticides is provided. (Reference) Figure 6 According to an embodiment of the present invention, the method includes: enriching the carbamate pesticide in the test sample using the aforementioned method for enriching carbamate pesticides, so as to obtain a mass spectrometry ionization source element on which the carbamate pesticide is adsorbed on the surface; and detecting the mass spectrometry ionization source element on which the carbamate pesticide is adsorbed on the surface using the aforementioned integrated separation and ionization mass spectrometry device, so as to perform qualitative / quantitative detection of the carbamate pesticide. Therefore, the aforementioned mass spectrometry ionization source element can specifically enrich nine trace carbamate pesticides in food. It exhibits strong adsorption, which is beneficial for fully enriching carbamate pesticides in complex matrices. Furthermore, the mass spectrometry ionization source element for enriching carbamate pesticides is directly connected to a high-voltage power supply. Under the influence of the high voltage, the target analytes on the mass spectrometry ionization source element are ionized by the elution solvent. The generated ions directly enter the mass spectrometer through the detector inlet to obtain the acquired signal, eliminating the need for chromatographic separation. The detection procedure is simple and fast, enabling simultaneous detection of trace carbamate pesticides. It boasts high throughput, low background noise, and high sensitivity, making it particularly suitable for high-throughput, rapid, and accurate analysis of trace carbamate pesticides. In addition, this mass spectrometry ionization source element is reusable, resulting in low detection costs.

[0073] 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: 3.5 kV; ionization elution solvent: methanol solution. Therefore, the signal response is stronger when the voltage is 3.5 kV; the signal response is even higher when methanol is used as the elution solvent. Thus, selecting the above voltage and elution solvent is beneficial to improving the detection signal of the analyte, resulting in higher detection sensitivity and accuracy.

[0074] 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: 30 psi; ion spray voltage: 4500 V; ion source temperature: 550 °C; 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 carbamate pesticides.

[0075] According to an embodiment of the present invention, the volume of the ionization elution solvent is 15-25 μL. This volume of ionization elution solvent not only facilitates thorough elution of the target analyte but also avoids solvent waste.

[0076] According to embodiments of the present invention, the carbamate pesticide is at least one selected from carbaryl, isoprocarb, fenofarad, bendioxon, dietofencarb, pirimicarb, propoxur, methiocarb, or methyl carbonate.

[0077] 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.

[0078] 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 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 Accustandard.

[0079] The materials and reagents used in the embodiments of this invention are shown in Table 1.

[0080] Table 1

[0081]

[0082] Example 1

[0083] Using the method of this invention, a trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source element with stainless steel as the conductive substrate and TAPOB-BDD covalent organic framework as the extraction layer is prepared. The preparation process is as follows:

[0084] (a) Cut the stainless steel base into an isosceles triangle with a waist length of 2cm, a base length of 1cm, and a thickness of 0.3mm.

[0085] (b) The stainless steel sheet from step (a) was ultrasonically treated with 2 mol / L sulfuric acid for 3 hours, then repeatedly washed with ultrapure water until neutral, ultrasonicated again in ultrapure water for 3 hours, dried rapidly by blowing with nitrogen, and stored in acetonitrile for later use to obtain the acidified stainless steel substrate.

[0086] (c) Take 10 stainless steel substrates from step (b) into a 200 mL Erlenmeyer flask, weigh out TAPOB (53 mg, 0.13 mmol), add 10 mL THF, shake well, sonicate for 20 minutes, transfer to a shaker, and react for 1 hour at 60 °C and 200 rpm.

[0087] (d) Weigh 60 mg (0.1 mmol) of BDTB and dissolve it in 10 mL of THF. Add the mixed solution to the reaction system in step (c) and add 2 mL of acetic acid. Place the reaction system on a shaker and continue shaking at 60 °C and 200 rpm for 3 hours to obtain a trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source element.

[0088] (e) After the reaction is complete, the components are washed three times alternately with methanol and acetonitrile, and then soaked in acetonitrile for storage and future use.

[0089] Example 2

[0090] This embodiment characterizes the mass spectrometry ionization source element prepared in Example 1 using scanning electron microscopy and energy dispersive spectroscopy (EDS) to demonstrate the successful fabrication and physicochemical properties of the element, as detailed below:

[0091] 1. The morphology of the surface of the blank stainless steel substrate, the surface of the acid-treated stainless steel substrate, the surface of the mass spectrometry ionization source element prepared in Example 1, and the cross-section of the element were characterized by scanning electron microscopy (ZEISS GeminiSEM 300). The accelerating voltage was 3 kV. The experimental results are as follows: Figure 1 As shown, the surface morphology of the blank stainless steel substrate is flat and smooth. Figure 1 A), while the surface of the stainless steel substrate treated with sulfuric acid exhibits a rough and uneven appearance. Figure 1B) This is due to the sulfuric acid corroding the surface of the stainless steel substrate, which, after removing the stainless steel coating, is further oxidized. This provides more binding sites for the modification of amino monomers, which is beneficial for the synthesis of the covalent organic framework extraction layer. A densely packed, granular structure is visible on the surface of the synthesized ionization source element. Figure 1 (C and D) demonstrate the successful modification of the covalent organic framework extraction layer. These particulate structures possess a variety of functional groups on their surface, which can provide sites for the selective adsorption of target analytes. A cross-section of a blank stainless steel substrate (…) Figure 1 E) and the modified component cross-section ( Figure 1 F) Comparative observation showed that the thickness of the extraction layer on the element surface was approximately 15 μm, further confirming that the covalent organic framework extraction layer had been successfully modified onto the stainless steel substrate surface. 2. EDS analysis of the surface of the mass spectrometry ionization source element clearly showed the distribution of C, N, and O elements in the synthesized COF layer. Figure 2 This further confirms the successful synthesis of COF on a stainless steel substrate.

[0092] Example 3

[0093] In this embodiment, the trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source element prepared in Example 1 was used to selectively enrich nine carbamate pesticides. This element was then used as an open-type electrospray ionization mass spectrometry ionization source for direct detection and analysis, as detailed below:

[0094] (1) Extraction method

[0095] Commercially available ready-to-eat cowpeas were pulverized, and 2.0 g was weighed and placed in a 50 mL centrifuge tube. 5 mL of extraction solvent (acetonitrile:water:glacial acetic acid, v:v:v = 90:9:1) was added. The mixture was vortexed for 2 min, followed by sonication for 5 min. Then, it was centrifuged at 9000 r / min for 10 min at 4 °C. After centrifugation, the supernatant was collected and purged with nitrogen until nearly dry. 5 mL of water was added to redissolve the supernatant, and the mass spectrometry ionization source element from Example 1 was added. Extraction was performed by shaking at 1800 rpm for 10 min. The element loaded with the target compound was removed, dried, and then detected by open-circuit electrospray ionization mass spectrometry.

[0096] (2) Detection method

[0097] The element loaded with the target compound was placed on a specially designed three-dimensional moving platform. The element tip was adjusted to be 10 mm away from the mass spectrometer inlet and slightly tilted downwards to help overcome surface tension and achieve ionization. 20 μL of methanol solution was dropped onto the element surface, and a high voltage of 3.5 kV was applied to the element tail, generating analyte ions at the tip and forming a spray that entered the mass spectrometer for analysis. The mass spectrometry conditions included: detection mode: multiple reaction monitoring (MRM); nebulizer gas pressure (GS1): 55 psi; auxiliary gas pressure (GS2): 50 psi; curtain gas pressure: 30 psi; ion spray voltage (IS): 4500 V; ion source temperature: 550 °C; and the monitored ion pairs and collision energies are shown in Table 2. Quantification was performed using the peak area of ​​the analyte ions.

[0098] Table 2

[0099]

[0100] *Quantitative Ions

[0101] (3) Experimental Results

[0102] The method's limit of detection, limit of quantitation, precision, linear regression equation, linear range, coefficient of determination, matrix effect, and batch-to-batch reproducibility are shown in Table 3. The method's limit of quantitation is significantly lower than the maximum residue limits stipulated in GB 2763-2021 and EU No. 396 / 2005, meeting the requirements for residue analysis. It exhibits good inter-day and intra-day precision and good batch-to-batch reproducibility.

[0103] The recovery rates of the method were investigated by adding target analytes at concentrations of 1, 5, and 20 μg / kg to blank cowpea samples. The average recoveries of the nine carbamate pesticides ranged from 81.25% to 112.18%, which meet the analytical requirements for routine testing.

[0104] Table 3

[0105]

[0106] Example 4

[0107] In this embodiment, the trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source element of Example 1 was reused. The experimental method of Example 3 was used to extract and analyze the spiked sample to examine the reusability of the element. The results are as follows: Figure 3 As shown, the recovery rates of the nine carbamate pesticides remained stable in the five experiments conducted, demonstrating that the trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source element of this invention can be reused more than five times.

[0108] Example 5

[0109] In this embodiment, the trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source element of Example 1 was used to extract and analyze the spiked samples. The difference lies in the changes in parameters such as extraction time, extraction solvent volume, type of spray solvent, formic acid concentration in the spray solvent, and spray voltage. The effects of different extraction, elution, and spray conditions on the recovery rate were investigated. Specifically, the effects of extraction time (2-50 minutes), extraction solvent volume (5-25 mL), type of spray solvent (methanol, acetonitrile, isopropanol, ethyl acetate, or a mixed solution of methanol and acetonitrile (volume ratio 1:1)), and spray voltage (1-5 kV) on the recovery rate of nine carbamate pesticides were investigated. All experiments were conducted in triplicate, and the results were averaged. The error bars in the graph represent the standard deviation between the parallel data.

[0110] Experimental results are as follows Figure 4 and Figure 5 As shown, specifically, as Figure 4 As shown in Figure A, within the adsorption time of 0–10 min, the adsorption capacity of the element for the target analyte continuously increases before reaching saturation, indicating that the adsorption kinetics have reached equilibrium. Therefore, the preferred extraction time is determined to be 10 minutes; Figure 4 As shown in Figure B, the response of the target compound increases with increasing extraction solution volume, and the response stabilizes after 10 mL. Therefore, 10 mL is a relatively economical and environmentally friendly extraction volume while ensuring extraction efficiency. Figure 5 As shown in Figure A, when acetonitrile is placed on a COF solid matrix, its surface tension is very high. This high surface tension makes it difficult for droplets to form smoothly at the tip of the ionization source, causing the target analyte to accumulate on the solid matrix surface and reducing the amount entering the mass spectrum. Ethyl acetate and isopropanol have relatively high molecular viscosity, which significantly prolongs the ionization process. In contrast, methanol possesses excellent elution and ionization properties, thus becoming the preferred elution solvent. Figure 5 As shown in Figure B, when the voltage is set too low (less than 2.5 kV), the driving force for target elution is significantly insufficient, severely hindering effective mass spectrometry signal acquisition. Conversely, if the voltage is too high, the solvent will move rapidly on the solid substrate, leading to target diffusion and suppressing the effective electrospray process, which is also detrimental to mass spectrometry signal acquisition. The results show that when the voltage is in the 3.1-3.7 kV range, the mass spectrometry response increases with increasing voltage, but the mass spectrometry signal weakens significantly when the voltage exceeds 3.5 kV. Therefore, 3.5 kV is determined to be the preferred electrospray voltage.

[0111] 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.

[0112] 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. A separation and ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides, 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 mass spectrometry ionization source element according to claim 1, characterized in that, The conductive substrate is made of stainless steel and is in the shape of an isosceles triangle with a height of 1.5-2.5 cm and a base of 0.5-1.5 cm.

3. The mass spectrometry ionization source element according to claim 1, characterized in that, The thickness of the conductive substrate is 0.1-0.5 mm, and the thickness of the extraction layer is 10-20 μm.

4. A method for preparing the integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides as described in any one of claims 1-3, 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 separation and ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides. The amino monomer is 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), and the aldehyde monomer is N,N,N',N'-tetra(4-aldehydephenyl)-1,4-phenylenediamine (BDTB).

5. The method according to claim 4, characterized in that, The concentration of the amino monomer is 1.5-3.5 mg / mL; the concentration of the aldehyde monomer is 5-7 mg / mL; and the molar ratio of the amino monomer to the aldehyde monomer is 1-2:

1.

6. The method according to claim 5, characterized in that, The concentration of the amino monomer is 2.5 mg / mL; the concentration of the aldehyde monomer is 6 mg / mL; and the molar ratio of the amino monomer to the aldehyde monomer is 1.3:

1.

7. The method according to claim 4, characterized in that, The catalyst for the Schiff base reaction is acetic acid, based on 1-1.5 mmol of the amino monomer, with the amount of acetic acid being 2 mL. The organic solvents for both the organic solution containing the amino monomer and the organic solution containing the aldehyde monomer are tetrahydrofuran.

8. A mass spectrometry device integrating separation and ionization, characterized in that, include: The separation and ionization integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides as described in any one of claims 1-3; An open-type mass spectrometer detector, comprising an inlet disposed opposite to the tip of the mass ionization source element; and A high-voltage power supply is connected to the mass spectrometry ionization source element.

9. A method for enriching carbamate pesticides, 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 integrated mass spectrometry ionization source element for the detection of trace carbamate pesticides as described in any one of claims 1-3, so as to obtain a mass spectrometry ionization source element with the carbamate pesticide adsorbed on its surface. The oscillating contact treatment is performed at a speed of 1700-1900 rpm for 5-15 minutes.

10. A method for qualitative / quantitative detection of carbamate pesticides, characterized in that, include: The method for enriching carbamate pesticides according to claim 9 is used to enrich the carbamate pesticides in the test sample in order to obtain a mass spectrometry ionization source element with the carbamate pesticides adsorbed on the surface. as well as The mass spectrometry source element on which the carbamate pesticide is adsorbed on the surface is detected by the separation and ionization integrated mass spectrometry device according to claim 8, so as to perform qualitative / quantitative detection of the carbamate pesticide.

11. The method according to claim 10, characterized in that, Detection conditions of the integrated separation and ionization mass spectrometry device: High voltage power supply voltage: 3.5 kV; Ionization elution solvent: methanol solution; 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: 30 psi; Ion spray voltage: 4500 V; Ion source temperature: 550 ℃; Dwell time: 100 ms The volume of the ionization elution solvent is 15-25 μL. The carbamate pesticide is selected from at least one of carbaryl, isoprocarb, fenofarad, beniocarb, dietofencarb, pirimicarb, propoxur, methiocarb, or methyl carbonate.

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