MOFs / PDMS solid-phase microextraction membrane, preparation method thereof and application of MOFs / PDMS solid-phase microextraction membrane in electronic cigarette analysis

Abstract

The invention relates to an MOFs / PDMS solid-phase micro-extraction membrane, a preparation method thereof and application of the MOFs / PDMS solid-phase micro-extraction membrane in electronic cigarette analysis, and the MOFs / PDMS solid-phase micro-extraction membrane is prepared by mixing polydimethylsiloxane, modified MIL-101 and a solvent and carrying out drying treatment and curing treatment. The prepared composite solid-phase microextraction membrane is used for pretreatment of volatile benzene series in electronic cigarettes, and the result shows that the composite membrane has a good adsorption effect on benzene and ethylbenzene and has more potential compared with a traditional liquid-liquid extraction pretreatment method. According to the solid-phase microextraction membrane prepared by combining the modified MOFs and the polydimethylsiloxane, benzene series components can be efficiently enriched from a complex electronic cigarette matrix, impurity interference is reduced, and follow-up detection accuracy and sensitivity are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of physical and chemical index detection of electronic cigarettes, and particularly relates to a MOFs / PDMS solid-phase microextraction membrane, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid growth of the electronic cigarette market, the regulatory requirements for the quality and safety of electronic cigarette products are becoming increasingly urgent. The components of electronic cigarette samples are complex. In addition to nicotine, flavors, and additives, they may also contain harmful substances such as benzene series. As a class of common volatile organic compounds, some benzene series have carcinogenic, teratogenic, and mutagenic properties. Accurately analyzing the components such as benzene series in electronic cigarettes is crucial for evaluating the quality and safety of electronic cigarettes. Sample pretreatment, as a key link in analytical detection, directly affects the accuracy and reliability of subsequent analysis results.

[0003] Solid-phase microextraction (SPME) technology, as a new type of sample pretreatment technology, has been widely used in the fields of environment, food, biology, etc. due to its advantages such as no need for organic solvents, simple operation, and integration of sampling, extraction, and concentration. However, traditional solid-phase microextraction devices are mostly fibrous, with low mechanical strength, easy to break in actual operation, and limited extraction area, which affects the extraction efficiency. In addition, conventional solid-phase microextraction coating materials have less than ideal selectivity for certain specific components when facing complex electronic cigarette samples. Metal-organic framework (MOFs) materials, as a class of new porous materials, have advantages such as high specific surface area, adjustable pore structure, and rich active sites, and show excellent performance in the fields of gas adsorption, separation, catalysis, etc. Polydimethylsiloxane (PDMS) is a commonly used solid-phase microextraction coating material with good chemical stability, flexibility, and biocompatibility.

[0004] At present, in the field of electronic cigarette sample pretreatment, traditional methods have many limitations. On the one hand, traditional liquid-liquid extraction methods require the use of a large amount of organic solvents, which not only pollute the environment, but also the use of organic solvents may introduce impurities and interfere with the analysis results. On the other hand, some conventional solid-phase extraction technologies have limited selectivity and enrichment efficiency when dealing with complex samples, and it is difficult to meet the requirements for accurate analysis of trace components in electronic cigarettes. For example, in the extraction and purification method disclosed in CN118217668A, traditional organic solvents or membrane filtration are used, which not only introduce organic solvents and reduce purity, but also the sample purity obtained by simply using membrane filtration is reduced and further purification is still required. Therefore, it is of great practical significance to develop a highly efficient, environmentally friendly, and selective sample pretreatment method. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a MOFs / PDMS solid-phase microextraction membrane, its preparation method and application in e-cigarette analysis. In the present invention, the solid-phase microextraction membrane prepared by combining modified MOFs and polydimethylsiloxane can efficiently enrich benzene series components from complex e-cigarette matrices, reduce impurity interference, and improve the accuracy and sensitivity of subsequent detection.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a preparation method of a MOFs / PDMS solid-phase microextraction membrane, and the preparation method includes: mixing polydimethylsiloxane, modified MIL-101 and a solvent, and performing drying treatment and curing treatment to obtain it.

[0008] In the present invention, the solid-phase microextraction membrane prepared by combining polydimethylsiloxane and MIL-101(Cr) modified by 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine significantly improves the extraction sensitivity. Compared with the traditional method, it can significantly shorten the pretreatment time, improve the detection efficiency, and meet the requirements of rapid analysis.

[0009] Preferably, the preparation method of the modified MIL-101 includes dissolving a metal salt in a sodium hydroxide solution, then adding terephthalic acid and a modifying material to dissolve and react, and adding a cleaning agent and then performing vacuum drying to obtain it.

[0010] Preferably, the metal salt includes chromium(III) nitrate nonahydrate and / or iron(III) chloride hexahydrate.

[0011] Preferably, the mass ratio of the metal salt to terephthalic acid is 1:(0.4 - 0.5), for example, it can be 1:0.4, 1:0.45, 1:0.5, etc.

[0012] Preferably, the modifying material is 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine.

[0013] Preferably, the molar ratio of terephthalic acid to the modifying material is (4 - 16):1; the (4 - 16):1 can be 4:1, 8:1, 10:1, 12:1, 14:1, 16:1, etc.;

[0014] In the present invention, the ratio of the modifying material and terephthalic acid is designed and controlled to avoid changing the crystal crystallization mode and affecting the crystal crystallinity.

[0015] Preferably, the cleaning agent includes anhydrous ethanol and / or N,N-dimethylformamide.

[0016] Preferably, the temperature of the reaction is 150 - 200 °C and the time is 12 - 36 h. The 150 - 200 °C can be, for example, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C or 200 °C, etc. The 12 - 36 h can be, for example, 12 h, 24 h or 36 h, etc.

[0017] Preferably, the curing time is 1 - 2 h and the temperature is 60 - 80 °C. The 1 - 2 h can be, for example, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h or 2.0 h, etc. The 60 - 80 °C can be, for example, 60 °C, 65 °C, 70 °C, 75 °C or 80 °C, etc.

[0018] Preferably, the mass ratio of the modified MIL - 101, polydimethylsiloxane and curing agent is (1 - 2):(8 - 10):(0.8 - 1). The (1 - 2) can be 1, 1.2, 1.4, 1.6, 1.8 or 2, etc.; the (8 - 10) can be 8, 9 or 10, etc.; the (0.8 - 1) can be 0.8, 0.9 or 1, etc.

[0019] In the present invention, by designing and controlling the specific ratio of the modified MIL - 101, polydimethylsiloxane and curing agent, the premature curing of the composite solid - phase microextraction membrane and the agglomeration of MOFs materials are avoided.

[0020] Preferably, the solvent includes n - hexane and / or cyclohexane.

[0021] In a second aspect, the present invention provides a MOFs / PDMS solid - phase microextraction membrane prepared by the preparation method of the MOFs / PDMS solid - phase microextraction membrane described in the first aspect.

[0022] In a third aspect, the present invention provides an application of the MOFs / PDMS solid - phase microextraction membrane described in the second aspect in extracting benzene series compounds in electronic cigarettes.

[0023] In a fourth aspect, the present invention provides a method for extracting benzene series compounds in electronic cigarettes using the MOFs / PDMS solid - phase microextraction membrane described in the second aspect. It is characterized in that after the headspace extraction of the electronic cigarette sample using the MOFs / PDMS solid - phase microextraction membrane, the composite solid - phase microextraction membrane is taken out and an eluent is added for elution.

[0024] Preferably, the time of the headspace extraction is 2 - 3 h and the temperature is 20 - 30 °C. The 2 - 3 h can be, for example, 2 h, 2.5 h or 3 h, etc. The 20 - 30 °C can be, for example, 20 °C, 25 °C or 30 °C, etc.

[0025] Preferably, the eluent includes n - pentane.

[0026] Preferably, the benzene series includes any one or a combination of at least two of benzene, toluene, ethylbenzene, p-xylene, m-xylene, isopropylbenzene, o-xylene, or styrene.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] 1. The MOFs / PDMS solid-phase microextraction membrane prepared in this application can efficiently enrich benzene series components from complex e-cigarette matrices, reduce impurity interference, and improve the accuracy and sensitivity of subsequent detection. Compared with traditional methods, it can significantly shorten the pretreatment time, improve the detection efficiency, and meet the requirements of rapid analysis.

[0029] 2. The MOFs / PDMS solid-phase microextraction membrane prepared in this application can be directly used for the extraction of e-cigarette oil samples, and can be seamlessly docked with a variety of detection instruments such as gas chromatography-mass spectrometry (GC-MS), adapting to different laboratory conditions and analysis processes, improving the convenience and versatility of detection. And conduct actual detection and analysis of samples, providing technical support for the supervision and quality evaluation of e-cigarettes, and providing technical reserves for the improvement of relevant detection standards. Description of the Drawings

[0030] Figure 1 is a schematic flow chart of the preparation method of the MOFs / PDMS solid-phase microextraction membrane.

[0031] Figure 2 are SEM images of MIL-101(Cr), modified MIL-101(Cr), MIL-101(Cr) / PDMS, and the solid-phase microextraction membrane. Among them, Figure A is the SEM image of MIL-101(Cr), Figure B is the modified MIL-101(Cr), Figure C is the SEM image of MIL-101(Cr) / PDMS, and Figure D is the SEM image of the solid-phase microextraction membrane.

[0032] Figure 3 are XRD patterns of MIL-101(Cr) and modified MIL-101(Cr) powders. Detailed Embodiments

[0033] The technical solutions of the present invention will be further described below with reference to the drawings and through specific embodiments. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention is subject to the claims.

[0034] Sources of reagents and instruments used in the following examples:

[0035] Polydimethylsiloxane (PDMS): containing PDMS components and curing agent, Dow Corning DC184;

[0036] 2,4,6-Tris(4-carboxyphenyl)-1,3,5-triazine, terephthalic acid, chromium(III) nitrate nonahydrate, N,N-dimethylformamide, sodium hydroxide, n-hexane, n-pentane: analytically pure, Beijing MRD Technology Co., Ltd.;

[0037] Gas chromatography-mass spectrometry: GCMS-TQ8040 NX, Shimadzu;

[0038] Vortex oscillator: Thermo Fisher Scientific, USA;

[0039] Electronic analytical balance: ME204E, Mettler Toledo.

[0040] Example 1

[0041] In this example, the MOFs / PDMS solid-phase microextraction membrane was prepared.

[0042] Precisely weigh 1.0 g of NaOH and dissolve it in 125 mL of deionized water. Take 10 g of chromium(III) nitrate nonahydrate and add it to the above solution, then ultrasonicate for 10 min. Next, precisely weigh 4.15 g of terephthalic acid and add it to the above mixed solution, ultrasonicate for 10 min. Finally, take 1.0 g of 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine and dissolve it in the above solution, where the molar ratio of terephthalic acid to 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 12:1. Transfer the mixed solution to a reaction kettle, heat the reaction kettle to 170 °C, after reacting for 24 h, take out the sample, first wash it with N,N-dimethylformamide, then wash it with absolute ethanol, after centrifugal separation, place the sample in a beaker, vacuum dry it overnight, and after grinding the sample, the 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine modified MIL-101(Cr) material is obtained.

[0043] Adopt the dip-coating method. Add 0.5 g of the modified MIL-101(Cr) to a 20 mL headspace vial, add 2 mL of n-hexane, vortex for 1 min and ultrasonicate for 30 min, add 2.5 g of PDMS, vortex for 1 min and ultrasonicate for 60 min, and at room temperature, vacuum dry to evaporate n-hexane. Then weigh 0.25 g of the curing agent and add it to the mixture and ultrasonicate for 10 min. Place all the mixture in a stainless-steel tray, after coating evenly, cure it at 80 °C for 1 h to obtain the MOFs / PDMS solid-phase microextraction membrane, and then cut it into 1.0×1.0 cm for standby. The specific preparation method is as Figure 1 shown.

[0044] Example 2

[0045] In this example, the MOFs / PDMS solid-phase microextraction membrane was prepared.

[0046] Accurately weigh 1.0 g of NaOH and dissolve it in 125 mL of deionized water. Take 10.374 g of chromium(III) nitrate nonahydrate and add it to the above solution. Ultrasonic for 10 min. Then accurately weigh 4.15 g of terephthalic acid and add it to the above mixed solution. Ultrasonic for 10 min. Finally, take 3.02 g of 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine and dissolve it in the above solution. The molar ratio of terephthalic acid to 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 4:1. Transfer the mixed solution to a reaction kettle, heat the reaction kettle to 150 °C, after reacting for 36 h, take out the sample, first wash it with N,N-dimethylformamide, then wash it with absolute ethanol, after centrifugal separation, place the sample in a beaker, vacuum dry overnight, and after grinding the sample, 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine modified MIL-101(Cr) material is obtained.

[0047] Using the dip coating method, add 0.5 g of modified MIL-101(Cr) to a 20 mL headspace vial, add 2 mL of n-hexane, vortex for 1 min and ultrasonic for 30 min, add 2 g of PDMS, vortex for 1 min and ultrasonic for 60 min, and vacuum dry at room temperature to evaporate n-hexane. Then weigh 0.23 g of curing agent and add it to the mixture and ultrasonic for 10 min. Place all the mixture in a stainless steel tray, after coating evenly, cure it at 80 °C for 1 h to obtain the MOFs / PDMS solid phase microextraction membrane, and then cut it into 1.0×1.0 cm for standby. The specific preparation method is as Figure 1 shown.

[0048] Example 3

[0049] In this example, the MOFs / PDMS solid phase microextraction membrane was prepared.

[0050] Accurately weigh 1.0 g of NaOH and dissolve it in 125 mL of deionized water. Take 8.3 g of chromium(III) nitrate nonahydrate and add it to the above solution. Ultrasonic for 10 min. Then accurately weigh 4.15 g of terephthalic acid and add it to the above mixed solution. Ultrasonic for 10 min. Finally, take 1.51 g of 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine and dissolve it in the above solution. The molar ratio of terephthalic acid to 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 16:1. Transfer the mixed solution to a reaction kettle, heat the reaction kettle to 200 °C, after reacting for 12 h, take out the sample, first wash it with N,N-dimethylformamide, then wash it with absolute ethanol, after centrifugal separation, place the sample in a beaker, vacuum dry overnight, and after grinding the sample, 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine modified MIL-101(Cr) material is obtained.

[0051] Using the dip - coating method, 0.5 g of modified MIL - 101(Cr) was added into a 20 - mL headspace vial, 2 mL of n - hexane was added, vortexed for 1 min and sonicated for 30 min, 4 g of PDMS was added, vortexed for 1 min and sonicated for 60 min, and the n - hexane was evaporated by vacuum drying at room temperature. Then, 0.4 g of curing agent was weighed and added into the mixture and sonicated for 10 min. All the mixture was placed in a stainless - steel dish, cured at 60 °C for 2 h after being evenly coated to obtain the MOFs / PDMS solid - phase microextraction membrane, and then cut into 1.0×1.0 cm for standby. The specific preparation method is as follows Figure 1 shown

[0052] Example 4

[0053] In this example, the MOFs / PDMS solid - phase microextraction membrane was prepared

[0054] Precisely weigh 0.25 g of NaOH and dissolve it in 125 mL of deionized water. Take 10 g of chromium(III) nitrate nonahydrate and add it into the above solution, sonicate for 10 min. Then precisely weigh 4.15 g of terephthalic acid and add it into the above mixed solution, sonicate for 10 min. Finally, take 1.21 g of 2,4,6 - tris(4 - carboxyphenyl)-1,3,5 - triazine and dissolve it in the above solution, where the molar ratio of terephthalic acid to 2,4,6 - tris(4 - carboxyphenyl)-1,3,5 - triazine is 10:1. Transfer the mixed solution to a reaction kettle, heat the reaction kettle to 170 °C, take out the sample after reacting for 24 h, wash it first with N,N - dimethylformamide, then with absolute ethanol, place the sample in a beaker after centrifugal separation, and vacuum - dry it overnight. After grinding the sample, the 2,4,6 - tris(4 - carboxyphenyl)-1,3,5 - triazine - modified MIL - 101(Cr) material is obtained.

[0055] Using the dip - coating method, 0.5 g of modified MIL - 101(Cr) was added into a 20 - mL headspace vial, 2 mL of n - hexane was added, vortexed for 1 min and sonicated for 30 min, 2.5 g of PDMS was added, vortexed for 1 min and sonicated for 60 min, and the n - hexane was evaporated by vacuum drying at room temperature. Then, 0.25 g of curing agent was weighed and added into the mixture and sonicated for 10 min. All the mixture was placed in a stainless - steel dish, cured at 80 °C for 1 h after being evenly coated to obtain the MOFs / PDMS solid - phase microextraction membrane, and then cut into 1.0×1.0 cm for standby. The specific preparation method is as follows Figure 1 shown

[0056] The difference between this example and Example 1 is only that the molar ratio of terephthalic acid to 2,4,6 - tris(4 - carboxyphenyl)-1,3,5 - triazine is 10:1, and the rest is the same as that of Example 1.

[0057] Example 5

[0058] The preparation of MOFs / PDMS solid-phase microextraction membrane is carried out in this example.

[0059] Precisely weigh 1.0 g of NaOH and dissolve it in 125 mL of deionized water. Take 10 g of chromium nitrate nonahydrate and add it to the above solution, sonicate for 10 min. Then precisely weigh 4.15 g of terephthalic acid and add it to the above mixed solution, sonicate for 10 min. Finally, take 0.75 g of 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine and dissolve it in the above solution, where the molar ratio of terephthalic acid to 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 10:1. Transfer the mixed solution to a reaction kettle, heat the reaction kettle to 170 °C, after reacting for 24 h, take out the sample, first wash it with N,N-dimethylformamide, then wash it with absolute ethanol, after centrifugal separation, place the sample in a beaker and dry it overnight in vacuo. After grinding the sample, the 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine modified MIL-101(Cr) material is obtained.

[0060] Using the dip-coating method, add 0.5 g of the modified MIL-101(Cr) to a 20 mL headspace vial, add 2 mL of n-hexane, vortex for 1 min and sonicate for 30 min, add 2.5 g of PDMS, vortex for 1 min and sonicate for 60 min, and dry and evaporate n-hexane at room temperature in vacuo. Then weigh 0.25 g of the curing agent and add it to the mixture and sonicate for 10 min. Place all the mixture on a stainless steel plate, after coating evenly, cure it at 80 °C for 1 h to obtain the MOFs / PDMS solid-phase microextraction membrane, and then cut it into 1.0×1.0 cm for standby. The specific preparation method is as Figure 1 shown.

[0061] The difference between this example and Example 1 is only that the molar ratio of terephthalic acid to 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 16:1, and the rest is the same as that of Example 1.

[0062] Example 6

[0063] The preparation of MOFs / PDMS solid-phase microextraction membrane is carried out in this example.

[0064] Accurately weigh 1.0 g of NaOH and dissolve it in 125 mL of deionized water. Add 10 g of chromium(III) nitrate nonahydrate to the above solution and sonicate for 10 min. Then accurately weigh 4.15 g of terephthalic acid into the above mixed solution and sonicate for 10 min. Finally, add 1.0 g of 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine to the above solution. The molar ratio of terephthalic acid to 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 12:1. Transfer the mixed solution to a reaction kettle, heat the reaction kettle to 170 °C, take out the sample after reacting for 24 h, first wash it with N,N-dimethylformamide, then wash it with absolute ethanol, place the sample in a beaker after centrifugal separation, and dry it overnight under vacuum. After grinding the sample, the 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine modified MIL-101(Cr) material is obtained.

[0065] Using the dip-coating method, add 0.25 g of the modified MIL-101(Cr) to a 20 mL headspace vial, add 2 mL of n-hexane, vortex for 1 min and sonicate for 30 min, add 2.5 g of PDMS, vortex for 1 min and sonicate for 60 min, and dry and evaporate n-hexane under vacuum at room temperature. Then weigh 0.25 g of the curing agent and add it to the mixture and sonicate for 10 min. Place all the mixture on a stainless steel plate, cure it at 80 °C for 1 h after coating evenly, and the MOFs / PDMS solid-phase microextraction membrane is obtained. Then cut it into 1.0×1.0 cm for standby. The specific preparation method is as Figure 1 shown.

[0066] The difference from Example 1 is only that the mass ratio of MIL-101(Cr), polydimethylsiloxane and the curing agent is adjusted to 1:10:1, and the rest is the same as in Example 1.

[0067] Example 7

[0068] In this example, the MOFs / PDMS solid-phase microextraction membrane is prepared.

[0069] Accurately weigh 1.0 g of NaOH and dissolve it in 125 mL of deionized water. Add 10 g of chromium(III) nitrate nonahydrate to the above solution and ultrasonicate for 10 min. Then accurately weigh 4.15 g of terephthalic acid into the above mixed solution and ultrasonicate for 10 min. Finally, take 1.0 g of 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine and dissolve it in the above solution. The molar ratio of terephthalic acid to 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 12:1. Transfer the mixed solution to a reaction kettle, heat the reaction kettle to 170 °C, take out the sample after reacting for 24 h, first wash it with N,N-dimethylformamide, then wash it with absolute ethanol, place the sample in a beaker after centrifugal separation, dry it overnight under vacuum, and grind the sample to obtain 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine modified MIL-101(Cr) material.

[0070] Adopt the dip-coating method. Add 0.4 g of modified MIL-101(Cr) to a 20 mL headspace vial, add 2 mL of n-hexane, vortex for 1 min and ultrasonicate for 30 min. Add 2.5 g of PDMS, vortex for 1 min and ultrasonicate for 60 min, and dry and evaporate n-hexane under vacuum at room temperature. Then weigh 0.25 g of curing agent and add it to the mixture and ultrasonicate for 10 min. Place all the mixture in a stainless steel tray, cure it at 80 °C for 1 h after coating evenly to obtain the MOFs / PDMS solid-phase microextraction membrane, and then cut it into 1.0×1.0 cm for standby. The specific preparation method is as Figure 1 shown.

[0071] The difference from Example 1 is only that the mass ratio of MIL-101(Cr), polydimethylsiloxane and curing agent is adjusted to 1.6:10:1, and the rest is the same as Example 1.

[0072] Comparative Example 1

[0073] This comparative example is for the preparation of the MOFs / PDMS solid-phase microextraction membrane

[0074] Accurately weigh 1.0 g of NaOH and dissolve it in 125 mL of deionized water. Add 10 g of chromium(III) nitrate nonahydrate to the above solution and ultrasonicate for 10 min. Then accurately weigh 4.15 g of terephthalic acid into the above mixed solution and ultrasonicate for 10 min. Transfer the mixed solution to a reaction kettle, heat the reaction kettle to 170 °C, take out the sample after reacting for 24 h, first wash it with N,N-dimethylformamide, then wash it with absolute ethanol, place the sample in a beaker after centrifugal separation, dry it overnight under vacuum, and grind the sample to obtain MIL-101(Cr) material.

[0075] Using the dip coating method, 0.5 g of MIL-101(Cr) was added to a 20 mL headspace vial, 2 mL of n-hexane was added, vortexed for 1 min and sonicated for 30 min, 2.5 g of PDMS was added, vortexed for 1 min and sonicated for 60 min, and the n-hexane was evaporated by vacuum drying at room temperature. Then, 0.25 g of curing agent was weighed and added to the mixture and sonicated for 10 min. All the mixtures were placed in a stainless-steel dish, cured at 80 °C for 1 h after uniform coating, and the MOFs / PDMS solid-phase microextraction membrane was obtained and then cut into 1.0×1.0 cm for standby.

[0076] The difference from Example 1 is only that MIL-101(Cr) is not modified, and the rest is the same as Example 1.

[0077] Comparative Example 2

[0078] Precisely weigh 1.0 g of e-cigarette oil and place it in a 25 mL centrifuge tube, add 1 mL of ultrapure water and shake to disperse the sample evenly. Then add 20 mL of extraction solution (n-pentane solution containing 0.5 mg·L-1 toluene-d4), seal it with a lid and place it in a vortex shaker, vortex and shake for extraction at a speed of 3000 r·min-1 for 60 min. After standing, take the upper organic phase, filter it, centrifuge it and take the supernatant to obtain the test solution for injection analysis.

[0079] The difference between this comparative example and Example 1 is that the thin-film solid-phase microextraction method is not used, and the traditional liquid-liquid extraction method is selected to compare the difference in extraction efficiency.

[0080] Test Example 1

[0081] This test example detects the extraction effect of the MOFs / PDMS solid-phase microextraction membrane prepared in the above examples and comparative examples

[0082] (1) Material characterization

[0083] This test example observes the MOFs / PDMS solid-phase microextraction membrane prepared in Example 1 by electron microscopy. As Figure 2 shown in A, B, C, and D in it, it can be found that the crystal morphology of the modified MIL-101(Cr) material is irregular and blurred, agglomeration occurs, and the distribution is also uneven, indicating that the modified material has an impact on the crystal morphology of MIL-101(Cr). Figure 3 The results show that the H3TATB-modified MIL-101(Cr) product shows strong diffraction peaks at 2.9°, 3.4°, 5.2°, 8.5°, and 9.1°, which are consistent with the characteristic diffraction peaks of MIL-101(Cr), but there are differences in peak intensity. The introduction of H3TATB does not change the crystallization mode of the crystal, but affects the crystallinity of the crystal.

[0084] (2) Performance test

[0085] Accurately weigh six portions of 1.0 g of e-cigarette oil and place them in 20 mL headspace vials. Insert the syringe needle through the silicone rubber gasket with a PTFE liner on the bottle cap. The MOFs / PDMS membrane prepared in Example 1, which has been activated at 180 °C for 10 h, naturally adheres to the clean syringe needle. Tighten the bottle cap to seal the sample, then adjust the syringe position so that the MOFs / PDMS membrane is in the headspace position of the headspace vial, and perform headspace extraction at room temperature for 2 h. Take out the MOFs / PDMS membrane and place it in a centrifuge tube. Add 2 mL of n-pentane containing 0.5 mg / L toluene-d4 to dissolve and aspirate for 20 min. After desorption, directly inject the sample for analysis using GC-QTOF-MS.

[0086] The GC-QTOF-MS conditions are as follows: DA-WAX (30 m × 0.25 mm × 0.25 μm) chromatographic column, column temperature program: 40 °C (held for 3 min) → 10 °C / min → 130 °C (held for 3 min) → 20 °C / min → 200 °C (held for 5 min), transfer line temperature: 240 °C; column flow rate: 1.5 mL / min; purge flow rate: 1.5 mL / min; split ratio: 20:1; chromatographic mass spectrometry interface temperature: 240 °C; ion source temperature: 230 °C; acquisition mode: Q3SCAN + SIM mode. The detection information of 8 volatile organic compounds and internal standards is shown in Table 1.

[0087] Table 1

[0088]

[0089] The specific detection results are shown in Table 2.

[0090] Table 2

[0091]

[0092]

[0093] It can be seen from the test results that:

[0094] (1) It can be seen from Examples 1 to 2-7 that the composite matrix membrane prepared by the present invention enables MOFs and PDMS to cooperate, and through specific interactions, precise recognition and efficient selective extraction of benzene series compounds in e-cigarettes are achieved.

[0095] (2) It can be seen from Examples 1 and 2-5 that during the preparation of MIL-101 materials, increasing or decreasing the ratio of terephthalic acid and 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine has little effect on the extraction efficiency of the two benzene series compounds.

[0096] (3) It can be seen from Example 1 and Examples 6 - 7 that changing the mass ratio of MOFs to PDMS does not significantly affect the extraction efficiency of the two benzene series compounds. When the ratio reaches 1.6:1, the extraction efficiency slightly increases.

[0097] (4) It can be seen from Example 1 and Comparative Examples 1 - 2 that compared with liquid - liquid extraction, using the MOFs / PDMS composite solid - phase microextraction membrane for extraction can significantly improve the extraction efficiency of the two benzene series compounds. The modified MIL - 101 material has a better effect than the unmodified material, indicating that the modified material can increase the adsorption capacity of the MIL - 101 material.

[0098] Test Example 2

[0099] This test example conducts a stability test.

[0100] E - cigarette samples: 35 commercially available national standard e - cigarettes were numbered S1 - S35 respectively. Among them, S1 - S12 were from brand A, S13 - S22 were from brand B, S23 - S27 were from brand C, S28 - S29 were from brand D, S30 - S31 were from brand D, and S32 - S35 were from brand F.

[0101] Precisely weigh 1.0 g of the e - cigarette oil of S1 - S35 six times and place them in 20 - mL headspace vials. Insert the syringe needle through the silicone rubber pad with a polytetrafluoroethylene liner on the vial cap. Naturally adhere the MOFs / PDMS membrane prepared in Example 1, which has been activated at 180 °C for 10 h, to the clean syringe needle. Tighten the vial cap to seal the sample, then adjust the syringe position so that the MOFs / PDMS membrane is placed in the headspace position of the headspace vial, and perform headspace extraction at room temperature for 2 h. Take out the MOFs / PDMS membrane and place it in a centrifuge tube, add 2 mL of n - pentane containing 0.5 mg / L toluene - d4 to dissolve and adsorb for 20 min. After desorption, directly inject the sample for analysis by GC - QTOF - MS.

[0102] The GC - QTOF - MS conditions are as follows: DA - WAX (30 m × 0.25 mm × 0.25 μm) chromatographic column, column temperature program: 40 °C (for 3 min) → 10 °C / min → 130 °C (for 3 min) → 20 °C / min → 200 °C (for 5 min), transfer line temperature: 240 °C; chromatographic column flow rate: 1.5 mL / min; purge flow rate: 1.5 mL / min; split ratio: 20:1; chromatographic - mass spectrometry interface temperature: 240 °C; ion source temperature: 230 °C; acquisition mode: Q3SCAN + SIM mode. The detection information of 8 volatile organic compounds and internal standards is shown in Table 3.

[0103] Table 3

[0104] Number Compound Quantitative ion (m / z) Qualitative ion (m / z) 1 Benzene 78 51 2 Toluene 91 51 3 <![CDATA[Toluene-d8]]> 81 96 4 Ethylbenzene 91 106 5 p-Xylene 91 106 6 m-Xylene 91 106 7 Isopropylbenzene 105 120 8 o-Xylene 91 106 9 Styrene 78 104

[0105] The specific detection results are shown in Table 4. Benzene and ethylbenzene were detected in the e-cigarettes, with their contents ranging from 0.837 to 5.107 μg / g and from 0 to 0.798 μg / g respectively. However, toluene, p-xylene, m-xylene, cumene, o-xylene, and styrene were not detected, which is basically consistent with the results of liquid-liquid extraction, indicating that the contents of the above components in the e-cigarette products are relatively low.

[0106] Table 4

[0107]

[0108]

[0109] In summary, the solid-phase microextraction membrane prepared by combining modified MOFs and polydimethylsiloxane in the present invention can efficiently enrich the benzene series components from the complex e-cigarette matrix, reduce the interference of impurities, and improve the accuracy and sensitivity of subsequent detection.

[0110] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived within the technical scope disclosed by the present invention by those skilled in the art all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a MOFs / PDMS solid-phase microextraction membrane, characterized in that, The preparation method includes: mixing polydimethylsiloxane, modified MIL-101 and a solvent, and obtaining the product after drying treatment and curing treatment.

2. The preparation method of the MOFs / PDMS solid-phase microextraction membrane according to claim 1, wherein, The preparation method of the modified MIL-101 includes dissolving a metal salt in a sodium hydroxide solution, then adding terephthalic acid and a modifying material for dissolution and reaction, and vacuum drying after adding a cleaning agent.

3. The preparation method of the MOFs / PDMS solid-phase microextraction membrane according to claim 2, wherein The metal salt includes chromium(III) nitrate nonahydrate and / or iron(III) chloride hexahydrate; Preferably, the mass ratio of the metal salt to terephthalic acid is 1:(0.4 - 0.5); Preferably, the modifying material is 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine.

4. The preparation method of the MOFs / PDMS solid-phase microextraction membrane according to claim 2 or 3, characterized in that, The molar ratio of terephthalic acid to the modifying material is (4 - 16):1; Preferably, the cleaning agent includes anhydrous ethanol and / or N,N-dimethylformamide; Preferably, the temperature of the reaction is 150 - 200 °C and the time is 12 - 36 h.

5. The preparation method of the MOFs / PDMS solid-phase microextraction membrane according to any one of claims 1-4, characterized in that, The curing time is 1 - 2 h and the temperature is 60 - 80 °C.

6. The preparation method of the MOFs / PDMS solid-phase microextraction membrane according to any one of claims 1-5, characterized in that, The mass ratio of the modified MIL-101, polydimethylsiloxane and curing agent is (1 - 2):(8 - 10):(0.8 - 1); Preferably, the solvent includes n-hexane and / or cyclohexane.

7. A MOFs / PDMS solid-phase microextraction membrane prepared by the preparation method of the MOFs / PDMS solid-phase microextraction membrane according to any one of claims 1 - 6.

8. An application of the MOFs / PDMS solid-phase microextraction membrane according to claim 8 in extracting benzene series compounds in electronic cigarettes.

9. A method for extracting benzene series compounds in electronic cigarettes by using the MOFs / PDMS solid-phase microextraction membrane described in claim 8, characterized in that, The method includes: after performing headspace extraction on an electronic cigarette sample using the MOFs / PDMS solid-phase microextraction membrane, taking out the composite solid-phase microextraction membrane and adding a desorption solution for elution.

10. The method for extracting benzene series compounds in e-cigarettes by using the MOFs / PDMS solid-phase microextraction membrane according to claim 9, characterized in that, The time of the headspace extraction is 2 - 3 h and the temperature is 20 - 30 °C; Preferably, the desorption solution includes n-pentane.

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