Mass spectrum ionization element of phthalate compound

Abstract

The invention discloses a phthalate ionization element and a preparation method and application thereof, and the ionization element comprises a conductive substrate which is made of stainless steel; the adsorption layer covers at least part of the surface of the substrate, the adsorption layer is formed by a covalent organic framework material, and the covalent organic framework material is composed of repeated multi-element ring units shown in the formula I in the specification. The ionization element is uniform in coating, good in phthalate enrichment effect and high in adsorption capacity, the ionization element can serve as a fixed substrate, mass spectrometric detection is carried out through ionization and ionization, the detection steps are simple, the background noise of detection is low, sensitivity and accuracy are high, and the detection cost is low. The method is especially suitable for enrichment and detection of phthalate in a complex food matrix sample.

Description

Technical Field

[0001] The invention relates to the field of analytical chemistry, in particular to an ionization element for specifically adsorbing phthalate compounds and a preparation method and application thereof. Background Art

[0002] Phthalates are one of the most important chemicals, commonly used as plasticizers to improve the flexibility and processability of materials, and are widely used in food packaging materials. They are usually not covalently bound to polymers, which means that they may penetrate into the environment and harm the ecology. Phthalates can accumulate in water and soil through the food chain and pose a real exposure risk through inhalation and skin contact, and food ingestion is the main route of exposure to phthalates. Phthalates can mimic, compete with or impair the synthesis of endogenous hormones, leading to endocrine disruption. In addition, it is known to affect the reproductive system of fish and invertebrates and cause genetic abnormalities. Phthalates can cause mutagenicity, carcinogenicity and teratogenicity by interfering with biological processes in humans and wildlife, and are an important source of food contamination in recent years.

[0003] Therefore, the research on highly selective adsorption materials and mass spectrometry detection methods for phthalate compounds needs to be advanced urgently. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide an ionization element for specifically adsorbing phthalate compounds, which can achieve the extraction of various phthalates, has a simple extraction method, and is suitable for detection by analytical methods such as open solid substrate electrospray mass spectrometry, and has broad application prospects.

[0005] According to one aspect of the present invention, the present invention provides an ionization element for specifically adsorbing phthalate compounds. According to an embodiment of the present invention, the ionization element comprises: a conductive substrate, the substrate is formed of stainless steel; and an adsorption layer, the adsorption layer is coated on at least a portion of the surface of the substrate, the adsorption layer is formed of a covalent organic framework material, and the covalent organic framework material is composed of repeated polycyclic units shown in Formula I.

[0006]

[0007] The ionization element according to the embodiment of the present invention has a uniform coating, good phthalate enrichment effect, strong adsorption force, and the ionization element can be used as a fixed substrate to perform mass spectrometry detection through ionization. The detection steps are simple, the background noise of the detection is low, and the sensitivity and accuracy are high. It is particularly suitable for the enrichment and detection of phthalates in complex food matrix samples.

[0008] In addition, the ionization element for specifically adsorbing phthalate compounds according to the above embodiment of the present invention may also have the following additional technical features:

[0009] According to an embodiment of the present invention, the stainless steel is 304 stainless steel.

[0010] According to an embodiment of the present invention, the conductive base has a conical tip, preferably an isosceles triangle.

[0011] According to an embodiment of the present invention, the bottom side of the conductive substrate is no more than 2 cm, and the height of the conductive substrate is no more than 3 cm. Preferably, it is an isosceles triangle with a bottom side of 1 cm, a height of 2 cm, and a thickness of 0.2 mm.

[0012] According to an embodiment of the present invention, the thickness of the adsorption layer is 5-30 μm.

[0013] According to an embodiment of the present invention, the hydrophilic contact angle of the adsorption layer is 78-80 degrees.

[0014] According to an embodiment of the present invention, the phthalate compound is at least one selected from dimethyl phthalate (DMP), diethyl phthalate (DEP), (2-methoxy)ethyl phthalate (DMEP), (2-ethoxy)ethyl phthalate (DEEP), dipentyl phthalate (DPP), dihexyl phthalate (DHXP) and benzyl butyl phthalate (BBP).

[0015] According to another aspect of the present invention, the present invention provides a method for preparing the aforementioned ionization element for specifically adsorbing phthalate compounds. According to an embodiment of the present invention, the method comprises: subjecting a stainless steel sheet to an acidification treatment to obtain an acidified substrate; subjecting the acidified substrate to a first contact with an amino monomer, and subjecting the substrate to an ultrasonic and first oscillation treatment to obtain an ultrasonically oscillated mixture; and subjecting the ultrasonically oscillated mixture to a second contact with an aldehyde monomer, and subjecting the mixture to a Schiff base reaction to obtain the ionization element.

[0016] According to the preparation method of the embodiment of the present invention, the ionization element prepared by the method has a uniform coating, good specificity for enrichment of phthalate compounds, and strong adsorption capacity. In addition, the preparation method has mild conditions, simple steps, and is convenient for industrial production.

[0017] According to an embodiment of the present invention, the first contacting is performed in 1,4-dioxane.

[0018] According to an embodiment of the present invention, the ratio of the amino monomer to 1,4-dioxane is 0.08-0.12 mol:10 mL.

[0019] According to an embodiment of the present invention, the solvent of the aldehyde monomer is 1,4-dioxane, and the ratio is 0.08-0.12 mol:5 mL.

[0020] According to an embodiment of the present invention, the molar ratio of the aldehyde monomer to the amino monomer is 0.8-1.2:1.

[0021] According to an embodiment of the present invention, the aldehyde monomer is N,N,N',N'-tetrakis(4-formylphenyl)-1,4-phenylenediamine (NFPBD), and the amino monomer is 4',5'-bis(4-aminophenyl)-[1,1':2',1"-terphenyl]-4,4"-diamine (BAPTPDA).

[0022] According to an embodiment of the present invention, the ultrasonic treatment time is 15-30 minutes.

[0023] According to an embodiment of the present invention, the temperature of the shaking treatment is 55-65° C., the time is 0.5-1.5 hours, and the shaking frequency is 180-250 rpm.

[0024] According to an embodiment of the present invention, the temperature of the Schiff base reaction is 55-65° C., the time is 2-4 hours, preferably 3 hours, and the oscillation frequency is 180-250 rpm.

[0025] According to an embodiment of the present invention, the catalyst for the Schiff base reaction is acetic acid.

[0026] According to another aspect of the present invention, 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 ionization element for specific adsorption of phthalate compounds; an open mass spectrometry detector, the open mass spectrometry detector includes an injection port, the injection port is arranged relative to the tip of the ionization element; and a high-voltage power supply, the high-voltage power supply is connected to the ionization element. Thus, the aforementioned ionization element for specific adsorption of phthalate compounds is directly connected to the high-voltage power supply, and under the action of high voltage electricity, the target on the ionization 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, the detection step is simple, and the background noise of the detection is low, which is particularly suitable for the enrichment and detection of phthalate compounds in complex samples.

[0027] According to another aspect of the present invention, the present invention provides a method for enriching and purifying phthalate compounds. According to an embodiment of the present invention, the method comprises: pre-treating the sample to be tested so as to obtain a liquid to be tested; and subjecting the liquid to be tested to an ionization element that specifically adsorbs phthalate compounds as described above in an oscillating contact treatment so as to obtain an ionization element that adsorbs the phthalate compounds on the surface. As a result, the purification method has good specificity for phthalate compounds and strong adsorption capacity, which is conducive to fully enriching complex matrices, such as phthalate compounds in food. In addition, the enrichment and purification method of the embodiment of the present invention is simple to operate, does not require a complex sample pre-treatment process, and has a high sample extraction efficiency.

[0028] According to an embodiment of the present invention, the rotation speed of the oscillating contact treatment is 500-700 rpm, and the time is 25-35 minutes.

[0029] According to another aspect of the present invention, the present invention provides a method for qualitative / quantitative detection of phthalate compounds. According to an embodiment of the present invention, the method comprises: using the aforementioned method for enriching and purifying phthalate compounds to enrich phthalate compounds in a sample to be tested, so as to obtain an ionization element with surface enriched phthalate compounds; and using the aforementioned separation and ionization integrated mass spectrometry device to detect the ionization element with surface enriched phthalate compounds, so as to perform qualitative / quantitative detection of the phthalate compounds. Therefore, the aforementioned ionization element has good specificity for phthalate compounds in complex matrices and strong adsorption capacity, which is conducive to fully enriching phthalate compounds in complex matrices, and the ionization element for enriching phthalate compounds is directly connected to a high-voltage power supply. Under the action of high voltage electricity, the target on the ionization element is ionized under the action of an elution solvent, and the generated ions directly enter the mass spectrometer through the inlet of a mass spectrometer detector to obtain a collection signal. The detection step is simple, the background noise of the detection is low, and the detection sensitivity is high. It is particularly suitable for rapid and accurate analysis of trace phthalate compounds.

[0030] According to an embodiment of the present invention, the detection conditions of the separation and ionization integrated mass spectrometer are: high voltage power supply voltage: -3.0 kV; ionization elution solvent: methanol solution containing 0.1% formic acid.

[0031] According to an embodiment of the present invention, the detection conditions of the mass spectrometer are: detection mode: multiple reaction monitoring (MRM); electrospray voltage (IS): 5500V; nebulizer gas pressure (GS1): 55psi; auxiliary gas pressure (GS2): 50psi; curtain gas pressure (CUR): 20psi; ion source temperature (TEM): 550°C; dwell time (DT): 100ms.

[0032] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0034] Figure 1 A scanning electron microscope schematic diagram of a mass spectrometry element according to an embodiment of the present invention is shown, wherein A is a scanning electron microscope image of a solid substrate; B is a scanning electron microscope image of an acid-treated conductive substrate; and C is a scanning electron microscope image of COF (BAPTPDA-NFPBD)-SSS.

[0035] Figure 2 The material characterization diagram of the ionization element according to one embodiment of the present invention is shown, wherein (a) is an infrared spectrum diagram; (b) is a thermogravimetric analysis curve; (c) is C1s of X-ray photoelectron spectroscopy; (d) is N1s of X-ray photoelectron spectroscopy; (e) and (f) are the contact angles of the stainless steel substrate and COF (BAPTPDA-NFPBD)-SSS, respectively;

[0036] Figure 3 A schematic diagram showing the optimization results of enrichment conditions and ionization conditions according to one embodiment of the present invention is shown;

[0037] Figure 4 A schematic diagram showing the enrichment capability of the mass spectrometry element prepared in Example 1 for seven phthalates is shown. DETAILED DESCRIPTION

[0038] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

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

[0040] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0041] According to one aspect of the present invention, the present invention provides an ionization element for specifically adsorbing phthalate compounds. The ionization element according to the embodiment of the present invention has a uniform coating, good phthalate enrichment effect, strong adsorption, and the ionization element can be used as a fixed substrate to perform mass spectrometry detection through ionization ionization, with simple detection steps, low background noise, high sensitivity and accuracy, and is particularly suitable for the enrichment and detection of phthalates in complex food matrix samples.

[0042] In order to facilitate understanding of the ionization element, the ionization element is explained here. According to an embodiment of the present invention, the ionization element includes:

[0043] Conductive substrate 100

[0044] According to an embodiment of the present invention, the substrate is formed of stainless steel. The inventors have found that when a paper base or a wood base is used as a solid substrate, when used for open solid substrate electrospray mass spectrometry, due to the poor conductivity of the paper base or the wood base, the electrospray formed after applying high voltage thereon has high background interference, and the generated mass spectrometry signal is unstable. However, due to the good conductivity of the stainless steel substrate, high voltage can be directly applied to the substrate, the ionization efficiency is high, and the experimental operation can be further simplified.

[0045] According to an embodiment of the present invention, the stainless steel is 304 stainless steel. Therefore, the substrate formed by the 304 stainless steel material has good processing performance, is convenient for cutting, and has good electrical conductivity and heat resistance.

[0046] According to an embodiment of the present invention, the conductive substrate has a conical tip, that is, the substrate has a tip shape in a top view. Thus, it is convenient to perform open solid substrate electrospray mass spectrometry, fix the ionization element at the horizontal front end position of the mass spectrometer injection port, and estrogen adsorbed on the substrate surface can be eluted by applying a spray solvent, and ionized at the tip to form a Taylor cone spray through the action of a high voltage power supply, so as to directly enter the mass spectrometry detection. According to an embodiment of the present invention, the substrate is an isosceles triangle.

[0047] According to an embodiment of the present invention, the bottom side of the conductive substrate is no more than 2 cm, and the height of the conductive substrate is no more than 3 cm. Preferably, it is an isosceles triangle with a bottom side of 1 cm, a height of 2 cm, and a thickness of 0.2 mm. Thus, a spray Taylor cone is formed at the tip of the triangle. If the angle is too large, the elution solvent will be hindered from spraying due to surface tension. If the angle is too small, the substrate area is small, which affects the adsorption capacity of the substrate. At this size, the elution solvent is more efficient in forming a spray.

[0048] Adsorption layer 200

[0049] According to an embodiment of the present invention, the adsorption layer is coated on at least part of the surface of the substrate, and the adsorption layer is formed by a covalent organic framework material, and the covalent organic framework material is composed of repeated polycyclic units shown in Formula I. Compared with the acid-treated stainless steel substrate, the adsorption efficiency of the adsorption layer (COFCS) of the embodiment of the present invention is significantly improved, which may be due to π-π interaction, van der Waals force, pore filling and electrostatic interaction. First, since both phthalates and this COF material have aromatic rings, there will be π-π interaction between the two, thereby significantly enhancing the adsorption effect; secondly, the adsorption layer organic polymer (COF) material of the embodiment of the present invention has a rich pore structure, and phthalates can enter these pores and be adsorbed, especially when the molecular size of the target analyte matches the pore size of the material, the adsorption effect will be more significant; in addition, the surface of the COF material of the embodiment of the present invention is charged, and electrostatic interaction can occur with phthalates under neutral and alkaline conditions, thereby further enhancing the adsorption effect. Finally, the COF material of the embodiment of the present invention has a large specific surface area and can generate a certain force on phthalates through van der Waals force. Although the van der Waals force is weak, it still contributes to the adsorption effect.

[0050] According to an embodiment of the present invention, the thickness of the adsorption layer is 5-30 μm. Therefore, this thickness range indicates that the covalent organic framework material of the embodiment of the present invention is completely adsorbed on the conductive material and has a large adsorption capacity.

[0051] According to an embodiment of the present invention, the hydrophilic contact angle of the adsorption layer is 78-80 degrees. Therefore, the adsorption layer has good hydrophilicity and can adsorb phthalates in aqueous solution.

[0052] According to an embodiment of the present invention, the phthalate compound is at least one selected from dimethyl phthalate (DMP), diethyl phthalate (DEP), (2-methoxy)ethyl phthalate (DMEP), (2-ethoxy)ethyl phthalate (DEEP), dipentyl phthalate (DPP), dihexyl phthalate (DHXP) and benzyl butyl phthalate (BBP).

[0053] According to another aspect of the present invention, the present invention provides a method for preparing the aforementioned ionization element for specific adsorption of phthalate compounds. According to the preparation method of the embodiment of the present invention, the ionization element prepared by the method has a uniform coating, good specificity for enrichment of phthalate compounds, strong adsorption capacity, and the preparation method has mild conditions, simple steps, and is convenient for industrial production.

[0054] In order to facilitate understanding of the method for preparing the aforementioned ionization element for specifically adsorbing phthalate ester compounds, the method is explained here. According to an embodiment of the present invention, the method includes:

[0055] S100 acid treatment

[0056] According to an embodiment of the present invention, the stainless steel sheet is subjected to an acidification treatment to obtain an acidified substrate, thereby eliminating the interference of stains or other ions on the stainless steel surface, so that the subsequent reaction has a better synthesis effect.

[0057] S200 Ultrasonic Oscillation

[0058] According to an embodiment of the present invention, the acidified substrate is first contacted with an amino monomer and subjected to ultrasound and a first oscillation treatment to obtain an ultrasound-oscillated mixture.

[0059] According to an embodiment of the present invention, the first contact is performed in 1,4-dioxane, that is, the acidified substrate is contacted with a 1,4-dioxane solution in which the amino monomer is dissolved.

[0060] According to an embodiment of the present invention, the ratio of the amino monomer to 1,4-dioxane is 0.08-0.12 mol:10 mL. Therefore, within this ratio range, 1,4-dioxane is conducive to fully dissolving and dispersing the amino monomer without causing waste of 1,4-dioxane.

[0061] Amino Monomer According to an embodiment of the present invention, the ultrasonic time is 15-30 minutes, which is conducive to the full dissolution of the amino monomer in 1,4-dioxane.

[0062] According to an embodiment of the present invention, the temperature of the shaking treatment is 55-65° C., the time is 0.5-1.5 hours, and the shaking frequency is 180-250 rpm, which is conducive to the reactants being fully contacted for reaction.

[0063] S300 Schiff base reaction

[0064] According to an embodiment of the present invention, the mixture after ultrasonic oscillation is brought into second contact with an aldehyde monomer to perform a Schiff base reaction, so as to obtain the ionization element.

[0065] According to an embodiment of the present invention, the solvent of the aldehyde monomer is 1,4-dioxane, and the ratio is 0.08-0.12 mol:5 mL. Therefore, at this ratio, 1,4-dioxane is conducive to fully dissolving and dispersing the amino monomer, and no waste of 1,4-dioxane is caused.

[0066] According to an embodiment of the present invention, the molar ratio of the aldehyde monomer to the amino monomer is 0.8-1.2: 1, preferably 1: 1. Thus, this ratio is conducive to keeping the number of amino groups and aldehyde groups in the amino monomer close to that in the aldehyde monomer, so as to achieve complete reaction as much as possible and reduce the waste of monomers.

[0067] According to an embodiment of the present invention, the aldehyde monomer is N,N,N',N'-tetrakis(4-formylphenyl)-1,4-phenylenediamine (NFPBD), and the amino monomer is 4',5'-bis(4-aminophenyl)-[1,1':2',1"-terphenyl]-4,4"-diamine (BAPTPDA). Since the chemical structure of phthalate plasticizers has no special functional groups, only aromatic rings. Therefore, the inventors compared a variety of amino monomers and aldehyde monomers to select amino monomers and aldehyde monomers with multiple benzene rings to synthesize the COF, and used π-π conjugation to adsorb the target. In addition, the inventors also adjusted the pore size of COF according to aldehyde monomers with different numbers of benzene rings to match the size of phthalate molecules and enhance their adsorption.

[0068] According to an embodiment of the present invention, the temperature of the Schiff base reaction is 55-65°C, the time is 2-4 hours, preferably 3 hours, and the oscillation frequency is 180-250rpm. This is conducive to efficient and sufficient reaction and high product yield.

[0069] According to an embodiment of the present invention, the catalyst of the Schiff base reaction is acetic acid, thereby achieving good catalytic effect and high reaction efficiency.

[0070] According to another aspect of the present invention, 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 ionization element for specific adsorption of phthalate compounds; an open mass spectrometry detector, the open mass spectrometry detector includes an injection port, the injection port is arranged relative to the tip of the ionization element; and a high-voltage power supply, the high-voltage power supply is connected to the ionization element. Thus, the aforementioned ionization element for specific adsorption of phthalate compounds is directly connected to the high-voltage power supply, and under the action of high voltage electricity, the target on the ionization 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, the detection step is simple, and the background noise of the detection is low, which is particularly suitable for the enrichment and detection of phthalate compounds in complex samples.

[0071] According to another aspect of the present invention, the present invention provides a method for enriching and purifying phthalate compounds. According to an embodiment of the present invention, the method comprises: pre-treating the sample to be tested so as to obtain a liquid to be tested; and subjecting the liquid to be tested to an ionization element that specifically adsorbs phthalate compounds as described above in an oscillating contact treatment so as to obtain an ionization element that adsorbs the phthalate compounds on the surface. As a result, the purification method has good specificity for phthalate compounds and strong adsorption capacity, which is conducive to fully enriching complex matrices, such as phthalate compounds in food. In addition, the enrichment and purification method of the embodiment of the present invention is simple to operate, does not require a complex sample pre-treatment process, and has a high sample extraction efficiency.

[0072] According to an embodiment of the present invention, the rotation speed of the oscillating contact treatment is 500-700 rpm and the time is 25-35 minutes, which is conducive to the ionization element fully absorbing the phthalate compounds in the test liquid.

[0073] According to another aspect of the present invention, the present invention provides a method for qualitative / quantitative detection of phthalate compounds. According to an embodiment of the present invention, the method comprises: using the aforementioned method for enriching and purifying phthalate compounds to enrich phthalate compounds in a sample to be tested, so as to obtain an ionization element with surface enriched phthalate compounds; and using the aforementioned separation and ionization integrated mass spectrometry device to detect the ionization element with surface enriched phthalate compounds, so as to perform qualitative / quantitative detection of the phthalate compounds. Therefore, the aforementioned ionization element has good specificity for phthalate compounds in complex matrices and strong adsorption capacity, which is conducive to fully enriching phthalate compounds in complex matrices, and the ionization element for enriching phthalate compounds is directly connected to a high-voltage power supply. Under the action of high voltage electricity, the target on the ionization element is ionized under the action of an elution solvent, and the generated ions directly enter the mass spectrometer through the inlet of a mass spectrometer detector to obtain a collection signal. The detection step is simple, the background noise of the detection is low, and the detection sensitivity is high. It is particularly suitable for rapid and accurate analysis of trace phthalate compounds.

[0074] According to an embodiment of the present invention, the detection conditions of the separation and ionization integrated mass spectrometer are: high voltage power supply voltage: -3.0 kV; ionization elution solvent: methanol solution containing 0.1% formic acid. Therefore, when the high voltage power supply voltage is -3.0 kV, the signal response is strong; the methanol solution containing 0.1% formic acid is used as the ionization elution solvent for elution, and the signal response is high.

[0075] According to an embodiment of the present invention, the detection conditions of the mass spectrometer are: detection mode: multiple reaction monitoring (MRM); electrospray voltage (IS): 5500V; nebulizer gas pressure (GS1): 55psi; auxiliary gas pressure (GS2): 50psi; curtain gas pressure (CUR): 20psi; ion source temperature (TEM): 550°C; dwell time (DT): 100ms. Therefore, under the above conditions, phthalate compounds are detected, the target response value is high, the background noise of the detection is low, the detection sensitivity and accuracy are high, and it is particularly suitable for the rapid and accurate analysis of trace phthalate compounds.

[0076] The present invention is 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.

[0077] Below in conjunction with embodiment, the scheme of the present invention will be explained.It will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.Unrepresented specific techniques or conditions in the embodiment, according to the technology or conditions described in the document in this area or according to the product specification sheet.Reagents used or instruments that do not indicate manufacturers are conventional products that can be obtained commercially, for example, can be purchased from Sigma company.

[0078] The materials and reagents used in the examples of the present invention are shown in Table 1.

[0079] Table 1

[0080]

[0081] Example 1

[0082] According to the method for preparing an ionization element according to an embodiment of the present invention, 4',5'-bis(4-aminophenyl)-[1,1':2',1"-terphenyl]-4,4"-diamine (BAPTPDA) is used as an amino monomer and N,N,N',N'-tetrakis(4-formylphenyl)-1,4-phenylenediamine (NFPBD) is used as an aldehyde monomer to prepare an ionization element. The specific method is as follows:

[0083] 1. Disperse or dissolve the acidified solid substrate (6 pieces) and 4',5'-bis(4-aminophenyl)-[1,1':2',1"-terphenyl]-4,4"-diamine (44 mg, 0.1 mmol) in 10 mL of 1,4-dioxane in a conical flask (200 mL) and sonicate for 20 min.

[0084] 2. Then transfer the mixture to a water bath oscillator at 60°C and oscillate at 210 rpm for 1 h; dissolve N,N,N',N'-tetrakis(4-formylphenyl)-1,4-phenylenediamine (60 mg, 0.1 mmol) in 5 mL of 1,4-dioxane and slowly add the above system.

[0085] 3. Acetic acid (500 μL) was added dropwise into the conical flask as a catalyst to accelerate the reaction. The mixture was mechanically stirred at 210 rpm at 60°C for 3 h.

[0086] 4. The obtained yellow solid substrate coating material was washed alternately with methanol and acetonitrile until the supernatant was clear. Finally, the material was stored in acetonitrile. The reaction formula is as follows:

[0087]

[0088] Example 2

[0089] A detailed characterization experiment was conducted on the ionization element (COF (BAPTPDA-NFPBD)-SSS) prepared in Example 1 to demonstrate the successful preparation of the material and its excellent physical and chemical properties. The specific contents are as follows:

[0090] 1. The surface morphologies of conductive substrates, acid-treated conductive substrates, and COF (BAPTPDA-NFPBD)-SSS were characterized, providing evidence for the successful synthesis of COFs on solid substrate surfaces. Figure 1 As shown in (a), the surface of the solid substrate is smooth. After being treated with sulfuric acid, the surface presents a rough and uneven texture, as shown in Figure 1 (b) It is conducive to the subsequent coating of COF materials. When COFs are coated on a solid substrate as a coating, the surface presents relatively uniformly distributed spherical small particles, such as Figure 1 (c).

[0091] 2. FT-IR spectroscopy further confirmed the successful synthesis of COFs. Figure 2 As shown in (a), compared with amino monomers and aldehyde monomers, -NH 2 At 3352cm -1 The NH stretching band at 1693 cm -1 The C=O stretching band at 1589 cm -1 A newly observed peak appeared at , which can be attributed to the formation of C=N bonds in COFs. The results indicate that COFs were successfully synthesized via the Schiff base reaction.

[0092] 3. The thermal stability of COFs in the range of 40-800℃ was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Figure 2 As shown in (b), the small amount of weight loss at around 102°C is due to the evaporation of the solvent. When the temperature reaches around 600°C, the weight of the material decreases significantly, corresponding to the exothermic peak of the DTA curve. This phenomenon is believed to be caused by the degradation and carbonization of the COFs material. These results confirm that COFs have good thermal stability.

[0093] 4. If Figure 2 As shown in (c) and (d), the chemical composition of COFs was evaluated by X-ray photoelectron spectroscopy (XPS) analysis. In COFs, the XPS (C1s) spectrum showed peaks corresponding to C=C / CC bonds at 284.84 eV and C=N bonds at 285.04 eV, and the XPS (N1s) spectrum showed peaks corresponding to C=N bonds at 400.08 eV and NC bonds at 398.81 eV, further proving the successful synthesis of COF (BAPTPDA-NFPBD)-SSS.

[0094] 5. The hydrophobic properties of the solid substrate and COF (BAPTPDA-NFPBD)-SSS surface were studied by contact angle measurement: the water contact angle of the solid substrate was 96.4°, e.g. Figure 2 (e), indicating that it is hydrophobic, which can be attributed to the presence of an antioxidant oil film on the surface; after coating the COFs layer, the contact angle was measured to be 78.7° ( Figure 2 (f)), indicating that COF(BAPTPDA-NFPBD)-SSS has good hydrophilicity and can adsorb phthalates in aqueous solution.

[0095] Example 3

[0096] In this embodiment, the mass spectrometry detection parameters of phthalates in beverage samples were optimized using the ionization element prepared in Example 1, as follows:

[0097] 1. Experimental methods

[0098] (1) Take a beverage sample, dilute it five times, and store it in a refrigerator at 4°C.

[0099] (2) Phthalate esters are enriched to obtain enriched products. The specific operation is as follows: take the above test solution, add a piece of ionization element, vortex enrich for 30 minutes at 600 rpm, and then take it out and quickly wash the surface with deionized water to remove non-specific co-extracts.

[0100] (3) The ionization element that has adsorbed the target is detected by using a separation and ionization integrated mass spectrometry ionization device. The conditions for the analysis and detection of the mass spectrometry ionization device include: placing the ionization element on the mass spectrometry detection platform, adjusting the tip of the ionization element to be in the same straight line with the mass spectrometry inlet, and adjusting the tip of the ionization element to be 5 mm away from the mass spectrometry injection port; then, dripping 20 μL of a methanol solution containing 0.1% formic acid on the surface of the ionization element, then turning on the high-voltage power supply, applying a high voltage of 3.0 kV, and the test solution moves toward the tip of the ionization element, generating analyte ions at the tip and forming a spray, and entering the mass spectrometry analysis. The mass spectrometry conditions include: detection mode: multiple reaction monitoring (MRM); electrospray voltage (IS): 5500 V; nebulizer gas pressure (GS1): 55 psi; auxiliary gas pressure (GS2): 50 psi; curtain gas pressure (CUR): 20 psi; ion source temperature (TEM): 550° C.; dwell time (DT): 100 ms.

[0101] 2. Experimental results

[0102] (1) The optimized MRM mass spectrometry parameters of the seven phthalate esters are shown in Table 2, and the peak area of ​​the quantitative ion is used as the measurement indicator.

[0103] Table 2:

[0104]

[0105]

[0106] Note: * is the quantitative ion

[0107] Example 4

[0108] In this example, the effects of extraction condition parameters such as sample enrichment time, pH value, ionic strength, and ionization condition parameters such as applied voltage and elution solvent on the detection results are studied. Taking the analysis of 7 phthalates in beverage samples as an example, 7 phthalate spiked samples to be tested (spiked concentration: 20 μg / L) were prepared and analyzed three times in parallel using the mass spectrometry detection conditions of Example 2.

[0109] 1. Optimization of enrichment time

[0110] Enrichment time is an important factor in the enrichment process. In order to obtain the optimal extraction time, the effects of different extraction times of 5, 10, 20, 30, 40, and 50 min on the enrichment amount were studied. The enrichment amount was detected using the above detection steps three times in parallel. The results are shown in Figure 2. Figure 3As shown in (a), within 5-30 min, as the extraction time increases, the signal intensity of the seven PAEs (phthalates) also increases; then, when the extraction time exceeds 30 min, the signal intensity of the analyte remains almost unchanged, which is mainly due to the dynamic equilibrium between the analyte in the sample solution and the analyte adsorbed on the ionization element, proving that the extraction process of the ionization element can be completed in a shorter time, indicating that the ionization element has the potential to quickly extract analytes. Therefore, the extraction time is preferably 30 min to obtain a larger adsorption capacity.

[0111] 2. pH Optimization

[0112] The effect of different enrichment pH values ​​(3, 5, 7, 9, 11) on the enrichment amount of beverage samples was studied. The experiment was repeated three times. The results are as follows: Figure 3 As shown in (b), when the pH value is in the range of 3-7, the signal intensity increases with the increase of pH value, and when the enrichment pH value continues to increase, the signal intensity decreases. This may be because PAEs are easily hydrolyzed in strong acid and strong base environments, resulting in a decrease in the amount of PAEs, thereby affecting the enrichment of the analyte. Therefore, neutral pH is selected as the preferred enrichment pH to achieve greater enrichment of phthalates.

[0113] 3. Optimization of ionic strength

[0114] The ionic strength of the solution was studied by changing the concentration of sodium chloride. The experiment was repeated three times. The results are as follows: Figure 3 As shown in (c), 0-12% NaCl was added to evaluate the effect of salt concentration. As the NaCl concentration increased, the recovery of PAEs decreased significantly, which may be attributed to the increase in solution viscosity inhibiting the mass transfer process. Therefore, NaCl was not added in subsequent experiments.

[0115] 4. Optimization of spray ionization conditions

[0116] Spray ionization conditions determine the content of the target eluted from the ionization element and the detectable target signal, and play an important role in open mass spectrometry analysis. The two experimental parameters of spray voltage and spray solvent were studied, and the signal intensity of 7 PAEs analytes was compared to obtain better spray ionization conditions.

[0117] A. Spray voltage optimization

[0118] The spray voltage has a great influence on the signal of the analyte in the open mass spectrometry experiment. Here, different voltages are compared and studied. When the voltage is too low, the analyte eluted by the eluent cannot be ionized, and thus the signal cannot be detected. However, if the voltage is too high, the spray movement speed will be too fast, and the target to be tested cannot be fully ionized, resulting in the instrument being unable to collect all effective signals. The signal intensity of 7 phthalates was detected by applying different voltages, and each voltage was tested three times. The results are as follows: Figure 3 As shown in (d), the signal intensity of all analyte PAEs increases with the increase of applied voltage. When the absolute value of the voltage increases to 3.0 kV, most analytes can obtain the highest signal intensity, and then the signal intensity decreases with the increase of voltage. Therefore, in order to obtain stable and high signal intensity for most compounds, 3.0 kV is the preferred voltage.

[0119] B. Spray Solvent Optimization

[0120] For the spray solvent, it is required not only to maximize the elution of the analytes adsorbed on the ionization element, but also to have a higher ionization efficiency for the analytes. In order to obtain a higher signal intensity, the effects of methanol (MeOH), ethanol (EtOH), acetonitrile (ACN) and ethyl acetate (EAC) as spray solvents on the PAEs signal intensity were investigated and analyzed three times in parallel. The results are shown in Figure 3 As shown in (e), methanol has a better elution effect. Then, 0.1%, 0.2%, 0.3%, and 0.4% formic acid (FA) were added to methanol. The results are shown in Figure 3 As shown in (f), the results show that methanol containing 0.1% formic acid has better elution ability for 7 PAEs. Therefore, methanol containing 0.1% formic acid is preferred as the elution solvent.

[0121] 5. Detection limit, linear range and repeatability of mass spectrometry detection method

[0122] Seven different concentrations of phthalate standard solutions were prepared with blank beverage matrix solution to obtain standard curves, and the LODs, LOQs and precision of the method were investigated. The results are shown in Table 3. The linear range of the seven phthalate compounds to be tested was 0.1-80 μg / L, and the determination coefficient (r 2 ) is greater than 0.99, LODs are 0.03-0.4μg / L, LOQs are 0.1-2.0μg / L, and intra-day and inter-day precisions are 2.0%-8.4% and 2.53%-8.2%, respectively. Therefore, the detection of phthalate compounds using this element has good repeatability and the detection limit can meet the requirements. It has a good application prospect.

[0123] Table 3

[0124]

[0125] 6. Recovery rate of mass spectrometry detection method at different spike concentrations

[0126]

[0127] ND=not detected.

[0128] Example 5

[0129] In this example, the enrichment ability of the ionization element prepared in Example 1 was investigated. In order to study the enrichment ability of the material, the adsorption efficiency of the acid-treated solid substrate and COF (BAPTPDA-NFPBD)-SSS on 7 phthalates was compared. Figure 4 As shown in Figure 2, the peak area range of the four phthalates (20 μg / L) was 1.13x10 6 ~4.31x10 7 , while when COF(BAPTPDA-NFPBD)-SSS was used for extraction, their peak areas were 1.11x10 7 ~4.23x10 8 The adsorption efficiency of COF (BAPTPDA-NFPBD) -SSS for phthalates is 9.4 to 132.4 times that of the acid-treated solid substrate, which proves that the enrichment capacity of the ionization element of the embodiment of the present invention is significantly improved.

[0130] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0131] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. An ionization element for specifically adsorbing phthalate compounds, characterized in that: include: a conductive substrate formed of stainless steel; as well as The adsorption layer covers at least a portion of the surface of the substrate, and the adsorption layer is formed by a covalent organic framework material, and the covalent organic framework material is composed of repeated polycyclic units shown in Formula I.

2. The ionization element according to claim 1, characterized in that The stainless steel is 304 stainless steel, Optionally, the conductive substrate has a conical tip, preferably an isosceles triangle, Optionally, the bottom side of the conductive substrate is not greater than 2 cm, and the height of the conductive substrate is not greater than 3 cm. Preferably, it is an isosceles triangle with a bottom side of 1 cm, a height of 2 cm, and a thickness of 0.2 mm.

3. The ionization element according to claim 1, characterized in that: The thickness of the adsorption layer is 5-30 μm. Optionally, the hydrophilic contact angle of the adsorption layer is 78-80 degrees, Optionally, the phthalate compound is at least one selected from dimethyl phthalate (DMP), diethyl phthalate (DEP), (2-methoxy)ethyl phthalate (DMEP), dimethyl (2-ethoxy)ethyl phthalate (DEEP), dipentyl phthalate (DPP), dihexyl phthalate (DHXP) and butyl benzyl phthalate (BBP).

4. A method for preparing the ionization element for specifically adsorbing phthalate compounds according to any one of claims 1 to 3, characterized in that: include: Acidizing the stainless steel sheet to obtain an acidified substrate; The acidified substrate is first contacted with an amino monomer, and subjected to ultrasound and a first oscillation treatment to obtain an ultrasound-oscillated mixture; as well as The ultrasonically vibrated mixture is brought into second contact with an aldehyde monomer to undergo a Schiff base reaction, so as to obtain the ionization element.

5. The method according to claim 4, characterized in that The first contacting is carried out in 1,4-dioxane, Optionally, the ratio of the amino monomer to 1,4-dioxane is 0.08-0.12 mol:10 mL, Optionally, the solvent of the aldehyde monomer is 1,4-dioxane, with a ratio of 0.08-0.12 mol:5 mL, Optionally, the molar ratio of the aldehyde monomer to the amino monomer is 0.8-1.2:1, Optionally, the aldehyde monomer is N,N,N',N'-tetrakis(4-formylphenyl)-1,4-phenylenediamine (NFPBD), and the amino monomer is 4',5'-bis(4-aminophenyl)-[1,1':2',1"-terphenyl]-4,4"-diamine (BAPTPDA).

6. The method according to claim 4, characterized in that The ultrasound time is 15-30 minutes. Optionally, the shaking treatment temperature is 55-65°C, the time is 0.5-1.5 hours, and the shaking frequency is 180-250 rpm. Optionally, the temperature of the Schiff base reaction is 55-65° C., the time is 2-4 hours, preferably 3 hours, and the oscillation frequency is 180-250 rpm. Optionally, the catalyst for the Schiff base reaction is acetic acid.

7. A separation and ionization integrated mass spectrometer, characterized in that: include: The ionization element for specifically adsorbing phthalate compounds according to any one of claims 1 to 3; An open mass spectrometer detector, the open mass spectrometer detector comprising an injection port, the injection port being arranged opposite to the tip of the ionization element; as well as A high voltage power supply is connected to the ionization element.

8. A method for enriching and purifying phthalate compounds, characterized in that: include: Pre-treating the sample to be tested to obtain a test solution; as well as The test liquid is subjected to an oscillating contact treatment with the ionization element for specifically adsorbing phthalate ester compounds according to any one of claims 1 to 3, so as to obtain an ionization element with the phthalate ester compounds adsorbed on the surface thereof, Optionally, the rotation speed of the oscillating contact treatment is 500-700 rpm, and the time is 25-35 minutes.

9. A method for qualitative / quantitative detection of phthalate compounds, characterized in that: include: The method for enriching and purifying phthalate compounds according to claim 8 is used to enrich the phthalate compounds in the sample to be tested, so as to obtain an ionization element with enriched phthalate compounds on the surface; as well as The separation and ionization integrated mass spectrometer according to claim 7 is used to detect the ionization element enriched with phthalate compounds on the surface, so as to perform qualitative / quantitative detection of the phthalate compounds.

10. The method according to claim 9, characterized in that Detection conditions of the separation and ionization integrated mass spectrometer: High voltage power supply voltage: -3.0kV; Ionization elution solvent: methanol solution containing 0.1% formic acid, Optionally, the detection conditions of the mass spectrometer detector are: Detection method: multiple reaction monitoring (MRM); Electrospray voltage (IS): 5500 V; Atomizing gas pressure (GS1): 55psi; Auxiliary gas pressure (GS2): 50psi; Curtain air pressure (CUR): 20psi; Ion source temperature (TEM): 550°C; Dwell time (DT): 100ms.

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