Preparation and application of mass spectrum ionization source element special for carbamate pesticide analysis

Abstract

The invention discloses preparation and application of a mass spectrum ionization source element special for carbamate pesticide analysis, and the mass spectrum ionization source element comprises a conductive substrate; the extraction layer is formed on at least part of the surface of the conductive substrate, and the extraction layer is made of a covalent organic framework material composed of repetitive units shown in the formula I. The extraction layer of the mass spectrum ionization source element is uniform in coating, has a porous structure, is large in specific surface area, can specifically enrich various trace carbamate pesticides in a large flux manner, is rich in variety of enriched carbamate pesticides, is high in adsorption capacity, can directly perform mass spectrum detection through ionization and ionization, does not need a chromatographic separation process, and is high in detection efficiency. The detection steps are simple, the speed is high, the detected background noise is low, and the sensitivity and the accuracy are high. In addition, the mass spectrum ionization source element can be reused and is low in use cost.

Description

Technical Field

[0001] The present invention relates to the field of analytical chemistry, and in particular, to a separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection, a preparation method thereof, and an application thereof. Background Art

[0002] Liquid chromatography tandem mass spectrometry (LC-MS / MS) is a standard detection method for carbamate pesticides, which can accurately detect trace amounts of carbamate pesticides. However, the pretreatment is complex and the chromatographic separation time is long, which cannot meet the requirements of rapid detection. With the increasing emphasis on the timeliness, convenience, and accuracy of detection, enzyme-linked immunosorbent assay, electrochemical sensors, near-infrared spectroscopy, Raman spectroscopy, etc., which can realize the on-site rapid detection technology of carbamate pesticides, have been gradually developed. However, these technologies also have the disadvantages of false positives, low repeatability, and poor sensitivity.

[0003] Therefore, a solid substrate mass spectrometry ionization source and a corresponding detection method for rapid detection of multiple carbamate pesticides in complex matrices need to be studied. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. For this purpose, an object of the present invention is to provide a separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection. 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 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, the present invention provides a separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection. According to an embodiment of the present invention, the mass spectrometry ionization source element includes: a conductive substrate; and an extraction layer, the extraction layer is formed on at least a part of the surface of the conductive substrate, and the extraction layer is formed of a covalent organic framework material composed of repeating units shown in formula I.

[0006]

[0007] According to the mass spectrometry ionization source element of the embodiment of the present invention, the extraction layer coating is uniform, has a porous structure and a large specific surface area, can specifically enrich a variety of trace carbamate pesticides with large throughput, has a large variety of enriched carbamate pesticides and strong adsorption force, and moreover, the mass spectrometry ionization source element can directly perform mass spectrometry detection through ionization and ion formation without a chromatographic separation process, the detection steps are simple and fast, and the detection background noise is low, and the sensitivity and accuracy are high. In addition, the mass spectrometry ionization source element can be reused and has a low use cost.

[0008] In addition, the separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection according to the above embodiments of the present invention may further 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 an isosceles triangle shape, the height of the isosceles triangle 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] On the other hand, the present invention provides a method for preparing the aforementioned separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection. 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; making the acidified conductive substrate in first contact with an organic solution containing an amino monomer, and performing ultrasonic and shaking treatments so that the amino monomer adheres to the surface of the acidified conductive substrate to obtain a first reaction mixture; and making an organic solution containing an aldehyde monomer in second contact with the first reaction mixture and performing a Schiff base reaction to obtain the separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection.

[0014] According to the preparation method of the embodiment of the present invention, the extraction layer coating of the prepared mass spectrometry ionization source element is uniform, has a large specific surface area, has a porous structure, and has strong stability, can specifically enrich a variety of trace carbamate pesticides in a large flux, has a strong adsorption force, and moreover, the preparation method has mild conditions, simple steps, good reproducibility of the extraction coating, and 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); the aldehyde monomer is N,N,N',N'-tetrakis(4-formylphenyl)-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 dosage of acetic acid is 2 mL.

[0021] According to an embodiment of the present invention, the organic solvents of the organic solution containing the amino monomer and the organic solution containing the aldehyde monomer are both tetrahydrofuran. On the other hand, 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 trace carbamate pesticide detection; an open mass spectrometry detector, the open mass spectrometry detector includes a sampling port, and the sampling port is oppositely arranged relative to the tip of the mass spectrometry ionization source element; and a high-voltage power supply, the high-voltage power supply is connected to the mass spectrometry ionization source element.

[0022] In the integrated separation and ionization mass spectrometry device according to an embodiment of the present invention, the aforementioned mass spectrometry ionization substrate for enriching carbamate pesticides is directly connected to the high-voltage power supply. Under the action of high voltage, the target substance on the mass spectrometry ionization source element is ionized under the action of the elution solvent, and the generated ions directly enter the mass spectrometer through the mass spectrometer inlet to obtain a collection signal. There is no need for a chromatographic separation process, the detection steps are simple and fast, multiple trace carbamate pesticides can be detected simultaneously, the detection throughput is large, and the detection background noise is low. It is especially suitable for enriching and detecting multiple carbamate pesticides in complex matrices, such as food samples.

[0023] On another aspect of the present invention, the present invention provides a method for enriching carbamate pesticides. According to an embodiment of the present invention, the method includes: performing extraction treatment on a sample to be tested to obtain a test solution; and performing a shaking contact treatment on the test solution and the aforementioned integrated separation and ionization mass spectrometry ionization source element for trace carbamate pesticide detection to obtain a mass spectrometry ionization source element with the carbamate pesticide adsorbed on its surface. Thus, the method can specifically enrich multiple trace carbamate pesticides, has a strong adsorption force, is beneficial to fully enrich the target substance, such as carbamate pesticides in food; and, the enrichment method of the embodiment of the present invention is simple to operate, does not require a complex sample pretreatment process, and has a high sample extraction efficiency. In addition, the mass spectrometry ionization source element can be reused, and the use cost is low.

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

[0025] According to another aspect of the present invention, the present invention provides a method for qualitative / quantitative detection of carbamate pesticides. According to an embodiment of the present invention, the method includes: enriching carbamate pesticides in a sample to be tested by using the aforementioned method for enriching carbamate pesticides, so as to obtain a mass spectrometry ionization source element with the carbamate pesticides adsorbed on its surface; and detecting the mass spectrometry ionization source element with the carbamate pesticides adsorbed on its surface by using the aforementioned integrated separation and ionization mass spectrometry device, so as to perform qualitative / quantitative detection of the carbamate pesticides. Thus, the aforementioned mass spectrometry ionization source element can specifically enrich various trace carbamate pesticides in food, has a strong adsorption force, is conducive to fully enriching carbamate pesticides in complex matrices, and the mass spectrometry ionization source element enriched with carbamate pesticides is directly connected to a high-voltage power supply. Under the action of high voltage, the target substances on the mass spectrometry ionization source element are ionized under the action of an elution solvent, and the generated ions directly enter the mass spectrometer through the mass spectrometry detector inlet to obtain a collection signal. There is no need for a chromatographic separation process, the detection steps are simple and fast, multiple trace carbamate pesticides can be detected simultaneously, the detection throughput is large, the detection background noise is low, and the detection sensitivity is high. It is particularly suitable for high-throughput, fast, and accurate analysis of micro-trace carbamate pesticides. In addition, this mass spectrometry ionization source element can be reused, and the detection cost is low.

[0026] According to an embodiment of the present invention, the detection conditions of the integrated separation and ionization mass spectrometry device are: high-voltage power supply voltage: 3.5 kV; ionization elution solvent: methanol solution.

[0027] According to an embodiment of the present invention, the detection conditions of the mass spectrometry detector are: detection mode: multiple reaction monitoring (MRM); nebulizing gas pressure: 55 psi; auxiliary gas pressure: 50 psi; curtain gas pressure: 30 psi; ion spray voltage: 4500 V; ion source temperature: 550 °C; dwell 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 an embodiment of the present invention, the carbamate pesticide is at least one selected from Carbaryl, Isoprocarb, Fenobucarb, Bendiocarb, Diethofencarb, Pirimicarb, Propoxur, Methiocarb, or Metolcarb.

[0030] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned by practice of the present invention. Description of the Drawings

[0031] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 A schematic diagram of the scanning electron microscope results according to an embodiment of the present invention is shown, where A is the surface of a blank stainless-steel substrate, B is the surface of the stainless-steel substrate after acid treatment, C and D are the surfaces of the separation-ionization integrated mass spectrometry ionization source elements for trace carbamate pesticide detection, 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 trace carbamate pesticide detection;

[0033] Figure 2 A schematic diagram of the energy spectrum results according to an embodiment of the present invention is shown, where A is the Fe element distribution, B is the N element distribution, C is the C element distribution, and D is the O element distribution;

[0034] Figure 3 A schematic diagram of the results of repeated use of the mass spectrometry ionization source element according to an embodiment of the present invention is shown;

[0035] Figure 4 A schematic diagram of the results of optimization of the extraction conditions according to an embodiment of the present invention is shown, where A is the optimization result of the extraction time and B is the optimization result of the extraction volume;

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

[0037] Figure 6 A schematic diagram of the process for preparing a separation-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 Description of the Embodiments

[0038] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where 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 by referring to the accompanying drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0039] In the description of the present invention, the orientation or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and do not require the present invention to be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0040] According to one aspect of the present invention, the present invention provides a separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection. The mass spectrometry ionization source element according to an embodiment of the present invention has a uniform extraction layer coating, a large specific surface area, and a porous structure. It can specifically enrich trace carbamate pesticides, has a large variety of enriched carbamate pesticides, and a strong adsorption force. Moreover, this mass spectrometry ionization source element can directly perform mass spectrometry detection through ionization without a chromatographic separation process. The detection steps are simple and fast, and the detection background noise is low, with high sensitivity and accuracy. In addition, this mass spectrometry ionization source element can be reused, and the usage cost is low.

[0041] To facilitate the understanding of the mass spectrometry ionization source element of the embodiment of the present invention, according to the embodiment of the present invention, the mass spectrometry ionization source element is explained herein. 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 inventor found that when using a paper-based or wood-based solid substrate for open solid substrate electrospray mass spectrometry analysis, due to the poor conductivity of the paper-based or wood-based substrate, when a high voltage is applied thereto, the electrospray formed has a high background interference, and the generated mass spectrometry signal is unstable. However, due to the good conductivity of the stainless steel substrate, the high voltage can be directly applied to the substrate, and the ionization efficiency is high, which can further simplify the experimental operation.

[0044] According to an embodiment of the present invention, the conductive substrate is in an isosceles triangle shape. Thus, the stainless steel sheet is cut into a triangle, enabling it to have multiple application scenarios. It can not only be used as an ordinary extraction plate but also be conveniently applied to open electrospray mass spectrometry detection. When the extraction element is applied to open electrospray mass spectrometry detection, it is fixed at the horizontal front end position of the mass spectrometry inlet. By applying a high voltage, the spray solvent can elute the target substance adsorbed on the extraction element, ionize at the tip, and form a Taylor cone spray, which directly enters the mass spectrometry for detection. According to an embodiment of the present invention, the height of the isosceles triangle is 1. five - 2. five centimeters, and the base is 0. five - 1. five centimeters. Thus, a spray Taylor cone is formed at the triangular tip. Otherwise, if the angle is too small or too large, the elution solvent will be hindered by surface tension from forming a spray.

[0045] According to an embodiment of the present invention, the thickness of the conductive substrate is 0.1 - 0.5 mm. Thus, a substrate with this thickness can allow the liquid to wet the entire surface more quickly, forming a uniform liquid film, which is beneficial for generating stable and uniform spraying, and can enhance the electric field strength and stability, accelerate the heat transfer and evaporation rate, 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 part of the surface of the conductive substrate, and the extraction layer includes a covalent organic framework material composed of repeating units represented by Formula I. Thus, the extraction layer has a large specific surface area, a porous structure, and a granular accumulation shape, and can specifically enrich trace carbamate pesticides with strong adsorption force.

[0048] According to an embodiment of the present invention, the thickness of the extraction layer is 10 - 20 μm. Thus, this extraction layer thickness results in a short diffusion path between the functional particles or ligands on the membrane porous matrix and the liquid flow, fast mass transfer, and a significant reduction in the separation time of membrane adsorption, improving the separation efficiency.

[0049] According to an embodiment of the present invention, the carbamate pesticide is at least one selected from Carbaryl, Isoprocarb, Fenobucarb, Bendiocarb, Diethofencarb, Pirimicarb, Propoxur, Methiocarb, or Metolcarb.

[0050] On the other hand, the present invention provides a method for preparing the aforementioned separation and ionization integrated mass spectrometry ionization source element for detecting trace carbamate pesticides. According to the preparation method of the embodiment of the present invention, the prepared extraction layer of the mass spectrometry ionization source element has a uniform coating, a large specific surface area, a porous structure, and strong stability, can specifically enrich trace carbamate pesticides with strong adsorption force, and moreover, the preparation method has mild conditions, simple steps, good reproducibility of the extraction coating, and is convenient for industrial production.

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

[0052] S100 Provide a substrate

[0053] According to an embodiment of the present invention, a conductive substrate is provided. Thus, high voltage electricity can be directly connected to the substrate, and electrospray is formed through ionization.

[0054] S200 Acidification treatment

[0055] According to an embodiment of the present invention, the conductive substrate is subjected to acidification treatment to obtain an acidified conductive substrate. Thus, the passivation film is slightly dissolved through acidification to form a microscopically rough surface, increasing the specific surface area, thereby enhancing the mechanical bite force and chemical bonding strength of the coating or plating.

[0056] S300 Ultrasonic oscillation

[0057] The acidified conductive substrate is brought into first contact with an organic solution containing an amino monomer, and ultrasonic and oscillation treatments are performed so that the amino monomer adheres to the surface of the acidified conductive substrate to obtain a first reaction mixture. Thus, the amino monomer is bonded to the conductive substrate, facilitating the subsequent formation of a covalent organic framework polymer.

[0058] According to an embodiment of the present invention, the time of ultrasonic treatment is 15 - 25 minutes, the time of oscillation is 0.5 - 1.5 hours, the temperature is 55 - 65 °C, and the rotation speed is 190 - 210 rpm. Thus, it is beneficial for the amino monomer to be fully dissolved in the organic solvent and for the reactants to come into sufficient contact for reaction.

[0059] S400 Schiff base reaction

[0060] An organic solution containing an aldehyde monomer and an acetic acid solution are brought into second contact with the first reaction mixture, and a Schiff base reaction is performed to obtain 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 - aldehyde phenyl)-1,4 - phenylenediamine. Thus, the rigid organic framework structure formed by the reaction of these two monomers has a specific three - dimensional geometric configuration and can form π - π conjugation, hydrogen bond forces, etc. with the target substances, enabling targeted simultaneous adsorption of 9 carbamate target substances.

[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. Thus, this concentration is beneficial for ensuring a high binding rate of the amino monomer to the active sites of the stainless - steel substrate and can reduce unnecessary waste caused by excessive use of raw materials.

[0063] According to an embodiment of the present invention, the concentration of the aldehyde group monomer is 5-7 mg / mL, preferably 6 mg / mL. Thus, this concentration is conducive to ensuring a high reaction conversion rate of the reaction between the aldehyde group monomer and the amino monomer, so that the synthesized extraction layer can cover the surface of the stainless steel substrate to the greatest extent, and can also avoid unnecessary waste caused by excessive use of raw materials.

[0064] According to an embodiment of the present invention, the molar ratio of the amino monomer to the aldehyde group monomer is 1-2:1, preferably 1.3:1. At this ratio, the generated product can exhibit a more regular and ordered arrangement in the 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. Thus, 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 dosage of acetic acid is 2 mL. Thus, this volume ratio range can enable the components in the reaction system to fully contact, and enable the catalyst acetic acid to have a suitable concentration, thereby ensuring that the reaction proceeds at a relatively ideal rate.

[0067] According to an embodiment of the present invention, the organic solvents of the organic solution containing the amino monomer and the organic solution containing the aldehyde group monomer are both tetrahydrofuran. Thus, the solubility of the amino monomer and the aldehyde group monomer is high, which can make the monomers uniformly dispersed in the solution, reduce the problem of uneven reaction caused by too high or too low local concentration, and further improve the yield and quality stability of the product.

[0068] On the other hand, the present invention provides a separation and ionization integrated mass spectrometry device. According to an embodiment of the present invention, the device includes: the aforementioned separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection; an open mass spectrometry detector, the open mass spectrometry detector includes a sample inlet, and the sample inlet is oppositely arranged relative to the tip of the mass spectrometry ionization source element; and a high-voltage power supply, the high-voltage power supply is connected to the mass spectrometry ionization source element.

[0069] For the separation and ionization integrated mass spectrometry device according to an embodiment of the present invention, the aforementioned mass spectrometry ionization substrate for enriching carbamate pesticides is directly connected to the high-voltage power supply. Under the action of high voltage, the target substance on the mass spectrometry ionization source element is ionized under the action of the elution solvent, and the generated ions directly enter the mass spectrometer through the mass spectrometer inlet to obtain a collection signal. There is no need for a chromatographic separation process, the detection steps are simple and fast, trace carbamate pesticides can be detected simultaneously, the detection throughput is large, and the detection background noise is low. It is especially suitable for the enrichment and detection of multiple categories of carbamate pesticides in complex matrices, such as food samples.

[0070] According to another aspect of the present invention, the present invention provides a method for enriching carbamate pesticides. According to an embodiment of the present invention, the method includes: subjecting a sample to be tested to an extraction treatment to obtain a test solution; and performing a shaking contact treatment on the test solution and the aforementioned integrated separation and ionization mass spectrometry ionization source element for trace carbamate pesticide detection, so as to obtain a mass spectrometry ionization source element with the carbamate pesticides adsorbed on its surface. Thus, the method can specifically enrich 9 trace carbamate pesticides, has a strong adsorption force, is conducive to fully enriching carbamate pesticides in complex matrices, such as those in food; and the enrichment method of the embodiment of the present invention is simple to operate, does not require a complex sample pretreatment process, and has a high sample extraction efficiency. In addition, the mass spectrometry ionization source element can be reused, and the use cost is low.

[0071] According to an embodiment of the present invention, the rotation speed of the shaking contact treatment is 1700 - 1900 revolutions per minute, and the time is 5 - 15 minutes. Thus, it is conducive to the mass spectrometry ionization source element fully adsorbing the carbamate pesticides in the test solution.

[0072] According to another aspect of the present invention, the present invention provides a method for qualitative / quantitative detection of carbamate pesticides. Refer to Figure 6 , according to an embodiment of the present invention, the method includes: using the aforementioned method for enriching carbamate pesticides to perform an enrichment treatment on the carbamate pesticides in the sample to be tested, so as to obtain a mass spectrometry ionization source element with the carbamate pesticides adsorbed on its surface; and using the aforementioned integrated separation and ionization mass spectrometry device to detect the mass spectrometry ionization source element with the carbamate pesticides adsorbed on its surface, so as to perform qualitative / quantitative detection on the carbamate pesticides. Thus, the aforementioned mass spectrometry ionization source element can specifically enrich 9 trace carbamate pesticides in food, has a strong adsorption force, is conducive to fully enriching carbamate pesticides in complex matrices, and the mass spectrometry ionization source element for enriching carbamate pesticides is directly connected to a high-voltage power supply. Under the action of high voltage, the target substances on the mass spectrometry ionization source element are ionized under the action of an elution solvent, and the generated ions directly enter the mass spectrometer through the mass spectrometry detector inlet to obtain a collected signal, without the need for a chromatographic separation process. The detection steps are simple and fast, can simultaneously detect trace carbamate pesticides, have a large detection throughput, a low detection background noise, and a high detection sensitivity, and are particularly suitable for the large-throughput, fast, and accurate analysis of micro-trace carbamate pesticides. In addition, the mass spectrometry ionization source element can be reused, and the detection cost is low.

[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. Thus, when the voltage is 3.5 kV, the signal response is stronger; when methanol is used as the elution solvent, the signal response is higher. Furthermore, selecting the above voltage and elution solvent is beneficial to improving the detection signal of the analyte, making the detection sensitivity and accuracy higher.

[0074] According to an embodiment of the present invention, the detection conditions of the mass spectrometry detector are as follows: detection mode: multiple reaction monitoring (MRM); nebulizing gas pressure: 55 psi; auxiliary gas pressure: 50 psi; curtain gas pressure: 30 psi; ion spray voltage: 4500 V; ion source temperature: 550 °C; dwell time: 100 ms. Thus, under the above conditions, when detecting carbamate pesticides, the target compound has a high response value, the detection background noise is low, and the detection sensitivity and accuracy are high, which is especially suitable for the rapid and accurate analysis of trace carbamate pesticides.

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

[0076] According to an embodiment of the present invention, the carbamate pesticide is at least one selected from Carbaryl, Isoprocarb, Fenobucarb, Bendiocarb, Diethofencarb, Pirimicarb, Propoxur, Methiocarb, or Metolcarb.

[0077] The present invention will be described below 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 solution of the present invention will be explained below in conjunction with the embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments regarding specific techniques or conditions, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase, for example, they can be purchased from Accustandard.

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

[0080] Table 1

[0081]

[0082] Example 1

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

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

[0085] (b) Ultrasonically treat the stainless steel sheet in step (a) with 2 mol / L sulfuric acid for 3 hours, then repeatedly wash it with ultrapure water until neutral, continue to ultrasonically treat it in ultrapure water for 3 hours, dry it quickly by nitrogen blowing, and store it in acetonitrile for later use to obtain the acidified stainless steel substrate.

[0086] (c) Take 10 stainless steel substrates in step (b) in a 200 mL conical flask, weigh TAPOB (53 mg, 0.13 mmol), then add 10 mL of THF, shake well, transfer it to a shaker after ultrasonication for 20 minutes, and react at 60 °C with a shaking frequency of 200 rpm for 1 hour.

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

[0088] (e) After the reaction, wash the element alternately with methanol and acetonitrile 3 times, and soak it in acetonitrile for storage for later use.

[0089] Example 2

[0090] In this example, the scanning electron microscope characterization and energy spectrum elemental analysis are carried out on the mass spectrometry ionization source element prepared in Example 1 to prove the successful preparation and physicochemical properties of the element, as follows:

[0091] 1. Characterize the morphology of the surface of the blank stainless steel substrate, the surface of the stainless steel substrate after acid treatment, the surface of the mass spectrometry ionization source element prepared in Example 1, and the cross-section of the element by scanning electron microscopy (ZEISS GeminiSEM 300) with an acceleration voltage of 3 kV. The experimental results are as Figure 1 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 after sulfuric acid treatment shows a rough and uneven morphology ( Figure 1B), which is caused by the sulfuric acid corroding the surface of the stainless-steel substrate. After removing the stainless-steel coating on the surface, it is further oxidized, which provides more binding sites for the modification of amino monomers and is beneficial to the synthesis of the covalent organic framework extraction layer. A granular dense packing structure can be seen on the surface of the synthesized ionization source element ( Figure 1 C and D), indicating the successful modification of the covalent organic framework extraction layer. There are various functional groups on the surface of these granular structures, and these groups can provide sites for selectively adsorbing target substances. Compare the cross-section of the blank stainless-steel substrate ( Figure 1 E) with the cross-section of the modified element ( Figure 1 F). The thickness of the extraction layer on the surface of the element is about 15 μm, further confirming that the covalent organic framework extraction layer has been successfully modified on the surface of the stainless-steel substrate. 2. Perform EDS analysis on the surface of the mass spectrometry ionization source element, and the distribution of C, N, and O elements in the synthesized COF layer can be clearly seen ( Figure 2 ), which once again confirms the successful synthesis of COF on the surface of the stainless-steel substrate.

[0092] Example 3

[0093] In this example, the trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source element prepared in Example 1 was used to selectively enrich 9 kinds of carbamate pesticides, and this element was used as an open electrospray ionization mass spectrometry ion source for direct detection and analysis, as follows:

[0094] (1) Extraction method

[0095] Crush the commercially available ready-to-eat cowpea samples, weigh 2.0 g and place it in a 50 mL centrifuge tube, add 5 mL of extraction solvent (acetonitrile: water: glacial acetic acid, v:v:v = 90:9:1), vortex the mixture for 2 min, and then ultrasonically treat for 5 min. Then, centrifuge at 9000 r / min for 10 min at 4 °C. After centrifugation, take the supernatant and blow it to near dryness with nitrogen, then add 5 mL of water to redissolve it, add the mass spectrometry ionization source element of Example 1, and shake and extract at 1800 rpm for 10 minutes. Take out the element loaded with the target compound, dry it, and perform open electrospray ionization mass spectrometry detection.

[0096] (2) Detection method

[0097] Place the component loaded with the target compound on a special three-dimensional moving platform. Adjust the tip of the component to a position 10 mm away from the mass spectrometry inlet and tilt it slightly downward to help overcome the surface tension and achieve ionization. Drop 20 μL of methanol solution onto the surface of the component, apply a high voltage of 3.5 kV at the tail of the component, generate analyte ions at the tip and form a spray, which enters the mass spectrometry analysis. The mass spectrometry conditions include: detection mode: multiple reaction monitoring (MRM); nebulizing 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; the monitored ion pairs and collision energies are shown in Table 2. Quantitative analysis is carried out using the peak area of the quantitative ion of the analyte.

[0098] Table 2

[0099]

[0100] *Quantitative ion

[0101] (3) Experimental results

[0102] The detection limit, quantification limit, precision, linear regression equation, linear range, determination coefficient, matrix effect of the method, and the between-batch reproducibility of the components are shown in Table 3. The quantification limit of this method is significantly lower than the maximum residue limits of GB 2763-2021 and EU Regulation No 396 / 2005, meeting the requirements of residue analysis. The precision is good both day-to-day and within-day, and there is good reproducibility between batches of components.

[0103] Add the target substances with concentrations of 1, 5, and 20 μg / kg respectively to blank cowpea samples to investigate the recovery rate of the method. The average spiked recovery rates of 9 carbamate pesticides are 81.25 - 112.18%, meeting the analysis requirements for daily detection.

[0104] Table 3

[0105]

[0106] Example 4

[0107] In this example, reuse the trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source component of Example 1, and use the experimental method of Example 3 to extract and detect the spiked samples to investigate the reusability of the component. The results are as Figure 3 shown that in the 5 experiments carried out, the recovery rates of 9 carbamate pesticides remained stable, proving that the trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source component of the embodiment of the present invention can be reused more than 5 times.

[0108] Example 5

[0109] In this example, the trace carbamate pesticide separation-ionization integrated mass spectrometry ionization source element of Example 1 was used to extract and detect the spiked sample. The difference is that parameters such as extraction time, extraction solvent volume, spray solvent type, formic acid concentration in the spray solvent, and spray voltage were changed respectively, and the effects of different extraction conditions, elution conditions, and spray conditions on the recovery rate were investigated. Specifically, the effects of extraction time (2 - 50 minutes), extraction solvent volume (5 - 25 mL), spray solvent type (methanol, acetonitrile, isopropanol, ethyl acetate, a mixed solution of methanol and acetonitrile (volume ratio 1:1)), and spray voltage (1 - 5 kV) on the recovery rates of 9 carbamate pesticides were investigated. All experiments were set up in triplicate, and the results were averaged. The error bars after plotting represent the standard deviation between parallel data.

[0110] The experimental results are as Figure 4 and Figure 5 shown. Specifically, as Figure 4 shown in A, within the adsorption time of 0 - 10 min, the adsorption amount of the element to the target analyte showed a continuous increasing trend and then reached saturation, indicating that the adsorption kinetics reached equilibrium. Therefore, the preferred extraction time was determined to be 10 minutes; as Figure 4 shown in B, when the extraction solution volume increased, the response of the target compound increased and reached stability after 10 mL. Therefore, 10 mL is a more economical and environmentally friendly extraction volume under the premise of ensuring the extraction effect; as Figure 5 shown in A, when acetonitrile is on top of the COF solid matrix, their surface tension is very large. This high surface tension makes it difficult for the droplets at the tip of the ionization source to form smoothly. The target substance accumulates continuously on the surface of the solid matrix, and the amount entering the mass spectrometry decreases. The molecular viscosities of ethyl acetate and isopropanol are relatively high, which significantly prolongs the time required for the ionization process. In contrast, methanol has excellent elution and ionization properties, so it becomes the preferred elution solvent. Figure 5 shown in B, when the voltage is set low (less than 2.5 kV), the driving force for eluting the target substance is significantly insufficient, seriously hindering the mass spectrometry from effectively collecting signals; if the voltage is too high, the solvent will move rapidly on the solid substrate, resulting in the diffusion of the target substance and the inhibition of the effective electrospray process, which is also not conducive to mass spectrometry signal collection. The results show that when the voltage is in the range of 3.1 - 3.7 kV, the mass spectrometry response increases with the increase of voltage. When the voltage exceeds 3.5 kV, the mass spectrometry signal will significantly weaken. Therefore, 3.5 kV was determined as the preferred spray voltage.

[0111] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

[0112] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. An integrated separation and ionization mass spectrometry ionization source element for trace carbamate pesticide detection, characterized in that, Comprising: A conductive substrate; And An extraction layer formed on at least a part of the surface of the conductive substrate, the extraction layer being formed of a covalent organic framework material composed of repeating units represented by Formula I.

2. The mass spectrometry ionization source element according to claim 1, wherein The conductive substrate is formed of stainless steel. Optionally, the conductive substrate is in the shape of an isosceles triangle, the height of the isosceles triangle being 1.5 - 2.5 cm and the base being 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. Optionally, the thickness of the extraction layer is 10 - 20 μm.

4. A method for preparing a separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection according to any one of claims 1-3, characterized in that, Comprising: Providing a conductive substrate; Subjecting the conductive substrate to an acidification treatment to obtain an acidified conductive substrate; Making a first contact between the acidified conductive substrate and an organic solution containing an amino monomer, and performing ultrasonic and shaking treatments to cause the amino monomer to adhere to the surface of the acidified conductive substrate, obtaining a first reaction mixture; and Making a second contact between an organic solution containing an aldehyde monomer and the first reaction mixture, and performing a Schiff base reaction to obtain the separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection.

5. The method according to claim 4, wherein The amino monomer is 1,3,5 - tris(4 - aminophenoxy)benzene (TAPOB). Optionally, the aldehyde monomer is N,N,N',N' - tetrakis(4 - aldehydephenyl)-1,4 - benzenediamine (BDTB). Optionally, the concentration of the amino monomer is 1.5 - 3.5 mg / mL, preferably 2.5 mg / mL. Optionally, the concentration of the aldehyde monomer is 5 - 7 mg / mL, preferably 6 mg / mL. Optionally, the molar ratio of the amino monomer to the aldehyde monomer is 1 - 2:1, preferably 1.3:

1.

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

7. An integrated separation and ionization mass spectrometry device, characterized in that, Comprising: The separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection according to any one of claims 1 - 3; An open - type mass spectrometry detector, the open - type mass spectrometry detector including an inlet, the inlet being oppositely arranged relative to the tip of the mass spectrometry ionization source element; and A high - voltage power supply connected to the mass spectrometry ionization source element.

8. A method for enriching carbamate pesticides, characterized in that, Comprising: Performing an extraction treatment on a sample to be measured to obtain a test solution; And Making a shaking contact treatment between the test solution and the separation and ionization integrated mass spectrometry ionization source element for trace carbamate pesticide detection according to any one of claims 1 - 3 to obtain a mass spectrometry ionization source element with the carbamate pesticide adsorbed on its surface. Optionally, the rotation speed of the shaking contact treatment is 1700 - 1900 revolutions and the time is 5 - 15 minutes.

9. A method for qualitatively / quantitatively detecting carbamate pesticides, characterized in that, Comprising: Enriching the carbamate pesticide in the sample to be measured by using the method for enriching carbamate pesticide according to claim 8 to obtain a mass spectrometry ionization source element with the carbamate pesticide adsorbed on its surface; And Use the integrated separation and ionization mass spectrometry device according to claim 7 to detect the mass spectrometry ionization source element with the carbamate pesticide adsorbed on the surface, so as to qualitatively / quantitatively detect the carbamate pesticide.

10. The method according to claim 9, wherein The detection conditions of the integrated separation and ionization mass spectrometry device: High-voltage power supply voltage: 3.5 kV; Ionization elution solvent: methanol solution; Optionally, the detection conditions of the mass spectrometry detector are: Detection mode: multiple reaction monitoring (MRM); Nebulizing gas pressure: 55 psi; Auxiliary gas pressure: 50 psi; Curtain gas pressure: 30 psi; Ion spray voltage: 4500 V; Ion source temperature: 550 °C; Dwell time: 100 ms, Optionally, the volume of the ionization elution solvent is 15 - 25 μL, Optionally, the carbamate pesticide is at least one selected from Carbaryl, Isoprocarb, Fenobucarb, Bendiocarb, Diethofencarb, Pirimicarb, Propoxur, Methiocarb or Metolcarb.

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