A solid phase microextraction probe, a preparation method and application thereof

Abstract

The application provides a solid-phase microextraction probe, a preparation method and application thereof, and relates to the field of solid-phase microextraction probes. The zirconium-based organometallic framework is synthesized first, and then two kinds of copolymerized monomers are polymerized on the zirconium-based organometallic framework through a crosslinking agent, and at the same time, the two kinds of copolymerized monomers are polymerized into copolymerized microsphere particles, so that a coating material with uniformly polymerized copolymerized microsphere particles on the surface of the zirconium-based organometallic framework is formed, the dissolution of the copolymerized microsphere particles can be avoided, and a stable solid-phase microextraction coating material is formed. After optimization, the coating material is fixed on a stainless steel wire carrier to form a solid-phase microextraction probe with high selectivity and high sensitivity, and the solid-phase microextraction probe is applied to the detection of organic phosphorus pesticide residues in an aqueous solution.

Description

Technical Field

[0001] This invention relates to the field of safety testing, specifically to a solid-phase microextraction probe, its preparation method, and its application. Background Technology

[0002] Organophosphorus pesticides (OPPs) are among the most widely used insecticides, sprayed on crops or soil, resulting in residues found in surface and groundwater, fruits and vegetables, tea, and drinking water. The misuse of OPPs can cause significant environmental damage and ultimately harm human health through the food chain. Pesticide residue analysis involves extraction, purification, and detection. The first two steps are sample pretreatment techniques, which are the most time-consuming and labor-intensive part of pesticide residue detection and determine the accuracy and precision of the analytical method.

[0003] Conventional methods for determining OPPs are based on chromatographic techniques, such as gas chromatography (GC), high-performance liquid chromatography (HPLC), and capillary electrophoresis (CE). GC is equipped with various detectors, such as flame ionization detector (FID), flame photometric detector (FPD), electron capture detector (ECD), nitrogen-phosphorus detector (NPD), and mass spectrometry (MS), and is the most widely used method for OPP analysis due to its excellent analytical performance. However, due to the complexity of sample matrices and the low levels of OPPs, it is difficult to directly determine OPPs in actual samples via GC. Therefore, appropriate sample pretreatment techniques are usually required before GC analysis, including liquid phase microextraction (LPME), solid phase extraction (SPE), and solid phase microextraction (SPME). SPME (Spectrum Extraction Mechanism) technology, a novel sample pretreatment, enrichment, and preconcentration technique that emerged in the 1990s, has attracted widespread attention due to its unique functions. It involves immobilizing a material with adsorption and extraction capabilities on a specific matrix surface, utilizing the principle that the analyte can achieve an equilibrium distribution between the stationary and aqueous phases. When used in conjunction with a GC (Gas Chromatography) injection device, it integrates sample collection, purification, concentration, and analysis of the analyte, offering advantages such as solvent-free operation, high efficiency, speed, and convenience. Compared to SPE (Spectrum Extraction Mechanism), SPME boasts higher recovery rates, simpler operation, greater portability, and is more economical and environmentally friendly.

[0004] The core of SPME (Spectrum Extraction Mechanism) is the microextraction coating, whose properties directly determine the selectivity and sensitivity of the extraction process. Therefore, the development of novel coatings has become one of the most important research directions in SPME. However, some unmodified materials may suffer from poor dispersibility and poor hydrophilic-lipophilic balance during the extraction process, making it difficult to extract target analytes from aqueous systems. Summary of the Invention

[0005] To overcome the aforementioned deficiencies in the prior art, the first aspect of the present invention proposes a solid-phase microextraction probe comprising a zirconium-based organometallic framework and copolymer microspheres. The copolymer microspheres are polymerized on the surface of the zirconium-based organometallic framework through a crosslinking agent to form a coating material on the surface of the zirconium-based organometallic framework in which the copolymer microspheres are uniformly distributed, achieving a suitable hydrophilic-lipophilic balance and exhibiting good polar interaction with organophosphorus pesticides in aqueous solution.

[0006] Furthermore, the copolymer microspheres are polymerized from two comonomers: divinylbenzene and N-vinylpyrrolidone.

[0007] Furthermore, the volume ratio of the comonomers divinylbenzene and N-vinylpyrrolidone is 6:4.

[0008] Furthermore, it also includes a carrier that is bonded to the coating material, the coating material and the carrier being bonded together by an adhesive.

[0009] The solid-phase microextraction probe proposed in this invention is coated with a coating material composed of a zirconium-based organometallic framework and copolymer microspheres. The DVB monomer exhibits strong oleophilicity, while the NVP monomer possesses strong hydrophilicity. The copolymer microspheres formed by these two monomers polymerize on the hydrophilic zirconium-based organometallic framework surface, which helps improve the probe's wettability and increase polar interactions, thereby enhancing the probe's extraction capability for organophosphorus pesticides in aqueous solutions. Coated onto a stainless steel carrier, magnetic stirring extraction is employed to reduce the "loss zone" effect caused by the liquid film protective sheath formed on the probe's outer wall, resulting in a solid-phase microextraction probe with high selectivity and sensitivity.

[0010] A second aspect of the present invention provides a method for preparing a solid-phase microextraction probe, used to prepare the probe proposed in the first aspect of the present invention, comprising:

[0011] S5.1 Synthesizing organometallic frameworks;

[0012] S5.2 Mix the two comonomers with acetonitrile solution, add the organometallic framework and crosslinking agent, seal, stir magnetically and heat to obtain the coating material;

[0013] S5.3 Pre-treat the carrier by dipping it in adhesive and bonding it with an appropriate amount of coating material and then drying it. The carrier and coating material are bonded twice, and after drying, a solid-phase microextraction probe is obtained.

[0014] Furthermore, the crosslinking agent is azobisisobutyronitrile.

[0015] The proposed method for preparing a solid-phase microextraction probe involves first synthesizing a zirconium-based organometallic framework, then polymerizing two comonomers on the zirconium-based organometallic framework using a crosslinking agent. Simultaneously, the two comonomers polymerize into copolymer microspheres, forming a coating material on the surface of the zirconium-based organometallic framework that uniformly polymerizes the copolymer microspheres. This prevents the copolymer microspheres from dissolving, resulting in a stable solid-phase microextraction coating material. The probe is then bonded to the carrier using polydimethylsiloxane (PDMS) as an adhesive. PDMS provides adhesion and protects the extraction probe.

[0016] The third aspect of this invention provides a method for detecting organophosphorus pesticide residues, which uses the solid-phase microextraction probe proposed in the first aspect of this invention to detect organophosphorus pesticide residues in aqueous samples. The steps include:

[0017] S7.1 Preparation of working solution: Add an appropriate amount of acetone solution to the mixed sample solution of pesticide and water.

[0018] S7.2 Extraction: The working solution is transferred to a glass vial with the probe inserted through the vial diaphragm to immerse the coating material below the surface of the working solution. Extraction is performed using magnetic stirring at a rotor speed of 1000 rpm.

[0019] S7.3 Instrument Setup and Probe Thermal Desorption Application: Set the injection port and detector temperature for the gas chromatograph, quickly insert the probe after extraction into the injection port, and remove it after thermal desorption.

[0020] Furthermore, the acetone solution in S7.1 accounts for 5% of the volume of the working solution.

[0021] Furthermore, the extraction time in S7.2 is 25 min.

[0022] Furthermore, the thermal desorption time in S7.3 is 4 minutes.

[0023] This scheme optimizes the detection method of organophosphorus pesticide residues in aqueous solution using the solid-phase microextraction probe proposed in this invention, enabling better enrichment and extraction of organophosphorus pesticide residues in aqueous solution samples. Combined with gas chromatography-flame photometry (GC-FPD), it achieves rapid and accurate determination of organophosphorus pesticide residues in water systems. Attached Figure Description

[0024] The accompanying drawings illustrate embodiments and, together with the description, serve to explain the principles of this application. Elements in the drawings are not necessarily to scale. The same reference numerals refer to corresponding similar parts.

[0025] Figure 1 This is a schematic diagram illustrating the synthesis of the coating material in a specific embodiment of the present invention;

[0026] Figure 2This is a scanning electron microscope image of coating material particles in a specific embodiment of the present invention;

[0027] Figure 3 This is a water contact angle diagram of coating material particles in a specific embodiment of the present invention.

[0028] Figure 4 This is a graph showing experimental data comparing the optimal monomer polymerization volume ratio of copolymerized microspheres in a specific embodiment of the present invention;

[0029] Figure 5 This is a schematic flowchart of a probe preparation method according to another specific embodiment of the present invention;

[0030] Figure 6 This is a graph showing experimental data comparing the optimal acetone ratio in another specific embodiment of the present invention;

[0031] Figure 7 This is a graph showing experimental data comparing the optimal magnetic stirring speed in another specific embodiment of the present invention.

[0032] Figure 8 This is a graph showing the comparative experimental data of extraction time in another specific embodiment of the present invention;

[0033] Figure 9 This is a graph showing the analytical temperature comparison experiment data in another specific embodiment of the present invention;

[0034] Figure 10 This is a comparative experimental data graph of thermal desorption in another specific embodiment of the present invention;

[0035] Figure 11 This is a comparative experimental data graph of extraction effect in another specific embodiment of the present invention. Detailed Implementation

[0036] The following description of examples of this application is provided to better understand it, and many anticipated advantages of other embodiments and embodiments will become apparent from the following detailed description. It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element. It is understood that the use of directional terms for illustrative purposes is by no means limiting.

[0037] Figure 1 This is a schematic diagram illustrating the synthesis of the coating material in a specific embodiment of the present invention. Copolymer microspheres formed from divinylbenzene (DVB) and N-vinylpyrrolidone (NVP) are polymerized on the surface of a zirconium-based organometallic framework (Zr-MOF-UiO-66-(OH)2) to form a DVB-NVP@UiO-66-(OH)2 coating material. Figure 2 This is a scanning electron microscope image of the coating material in a specific embodiment of the present invention. By adjusting the polymerization ratio of the two comonomers, NVP and DVB, and through optimization, it was found to have good polar interaction with organophosphorus pesticides. Figure 3 The image shows the water contact angle of the coating material particles in a specific embodiment of the present invention. The coating material is bonded to the stainless steel wire carrier with an adhesive, and the bonding is performed twice to ensure that the surface of the stainless steel wire carrier is uniformly covered with the coating material.

[0038] Preferably, to determine the optimal volume ratio of comonomers for the copolymerized microspheres, divinylbenzene (DVB) and N-vinylpyrrolidone (NVP) in volume ratios of 9:1, 8:2, 7:3, 6:4, and 5:5 were added to round-bottom flasks, respectively, and dissolved in 100 mL of acetonitrile solution. Figure 4 This is a comparative experimental data graph showing the optimal monomer polymerization volume ratio for copolymer microspheres in a specific embodiment of the present invention. The optimal polymerization volume ratio for comonomers is 6:4 when the volume ratio of divinylbenzene to N-vinylpyrrolidone is 6:4. At this point, the solid-phase microextraction probe has the highest extraction efficiency for organophosphorus pesticides.

[0039] The proposed solid-phase microextraction probe utilizes a DVB-NVP@UiO-66-(OH)2 coating material. DVB monomers exhibit strong oleophilicity, while NVP monomers possess strong hydrophilicity. The resulting copolymer microspheres polymerize on a hydrophilic zirconium-based organometallic framework, improving probe wettability and increasing polar interactions to enhance extraction capabilities in aqueous solutions. UiO-66-(OH)2, as a porous metal-organic framework, exhibits thermal and chemical stability. Optimal extraction performance is achieved by adjusting the polymerization ratio of NVP and DVB monomers; after optimization, the optimal DVB:NVP volume ratio is found to be 6:4.

[0040] In another specific embodiment, Figure 5 This is a schematic flowchart of a probe preparation method according to another specific embodiment of the present invention. The preparation of the solid-phase microextraction probe in the above embodiment includes:

[0041] S5.1 Synthesis of zirconium-based organometallic frameworks;

[0042] UiO-66-(OH)2 was synthesized by a hot solvent method: 2.15 mmol of zirconium tetrachloride and 1.95 mmol of 2,5-dihydroxyterephthalic acid were fully dissolved in 60 mL of N,N-dimethylformamide at room temperature and sonicated for 20 min. The mixture was then placed in a forced-air drying environment (oven) and heated at 100 °C for 36 h. After the reaction, the mixture was allowed to cool naturally, centrifuged to obtain the precipitate, soaked in ethanol at 60 °C for 48 h, and then centrifuged and dried to obtain a powder.

[0043] S5.2 Mix the two comonomers with acetonitrile solution, add the organometallic framework and crosslinking agent, seal, stir magnetically and heat to obtain the coating material;

[0044] Polymerization of coating material DVB-NVP@UiO-66-(OH)2: Divinylbenzene (DVB) and N-vinylpyrrolidone (NVP) in a volume ratio of 6:4 were dissolved in 100 mL of acetonitrile solution in a round-bottom flask and dispersed by sonication for 10 min. The flask was then placed in a magnetically heated stirring jacket and purged with dry nitrogen for 15 min while stirring. Next, 0.03 g of the UiO-66-(OH)2 yellow powder synthesized in the first step and 0.02 g of the crosslinking agent azobisisobutyronitrile (AIBN) were added. The mixture was sealed, stirred, and heated to 90 °C for 24 h. The precipitate obtained by centrifugation was washed three times thoroughly with ethanol and acetonitrile, and then completely dried in an oven to obtain the material powder.

[0045] S5.3 Pre-treat the carrier by dipping it in adhesive and bonding it with an appropriate amount of coating material and then drying it. The carrier and coating material are bonded twice, and after drying, a solid-phase microextraction probe is obtained.

[0046] Stainless steel wire was washed and soaked in acetone, ethanol, and pure water in sequence, and then dried for later use. Polydimethylsiloxane (PDMS) adhesive and its curing agent were ultrasonically dispersed in n-hexane at a ratio of 1 g : 500 μL, and then refrigerated for later use.

[0047] Dip a stainless steel wire in an appropriate amount of PDMS and spread it evenly on a smooth weighing paper, ensuring one end is coated with a thin, uniform layer of PDMS. Insert the wire vertically into the powder material to pick up the powder, carefully rotating and pulling it out to separate any loose powder. Dry the wire in an oven at 60°C, then recoat it with PDMS and dry it thoroughly again before use. Before use, assemble the coated stainless steel wire into a recycled commercial SPME assembly, and then age it at 260°C for 40 minutes in the injection port of a gas chromatograph (GC) to remove any potential contaminants.

[0048] The proposed method for preparing solid-phase microextraction probes involves first synthesizing a zirconium-based organometallic framework (ZAM). Two comonomers are then polymerized on the ZAM using a crosslinking agent, simultaneously forming copolymer microspheres. This creates a coating material of uniformly polymerized copolymer microspheres on the ZAM surface, preventing dissolution and ensuring a stable solid-phase microextraction coating. A polydimethylsiloxane (PDMS) binder is used to bond the probe to the carrier. PDMS provides adhesion and protects the extraction probe. Finally, contaminants are removed in gas chromatography to ensure accurate detection results.

[0049] In another specific embodiment of the present invention, the solid-phase microextraction probe obtained in the above embodiments is used to detect organophosphorus pesticide residues in aqueous solution, and the analytical procedure is applied by the direct-solid-phase microextraction-gas chromatography-flame photometric detection (DI-SPME-GC-FPD) method.

[0050] S7.1 Preparation of working solution: Add an appropriate amount of acetone solution to the mixed sample solution of pesticide and water.

[0051] Preferably, to determine the optimal ratio of acetone solution volume fraction to total volume, working solutions containing 0.5%, 1%, 5%, 10%, 15%, and 25% acetone were prepared respectively. Figure 6 The figure shows experimental data comparing the optimal ratio of acetone in another specific embodiment of the present invention. It can be seen that 5% of the volume of acetone solution is the optimal working solution ratio.

[0052] S7.2 Extraction: Transfer the working solution to a glass vial, with the probe inserted through the vial septum to immerse the coating material below the surface of the working solution, and extract using magnetic stirring at 1000 rpm.

[0053] Transfer 1 mL of the working solution to a 2 mL glass vial with a septum cap. Insert the SPME probe through the vial septum, immersing the coating material below the solution surface, and extract using magnetic stirring.

[0054] Preferably, to determine the optimal magnetic stirring speed, 250 rpm, 500 rpm, 750 rpm, 1000 rpm, 1250 rpm, and 1500 rpm are set respectively. Figure 7 The figure shows experimental data comparing the optimal magnetic stirring speed in another specific embodiment of the present invention. It can be seen that the extraction efficiency of the sample is the highest at 1000 rpm, and the optimal magnetic stirring speed is 1000 rpm.

[0055] Preferably, to determine the optimal extraction time, extraction was performed for 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, and 45 min, respectively. Figure 8The figure shows the extraction time comparison experiment data in another specific embodiment of the present invention. It can be seen that 25 min of extraction is the optimal extraction time for the solid phase microextraction probe.

[0056] S7.3 Instrument Setup and Probe Thermal Desorption Application: Set the injection port and detector temperature for the gas chromatograph, quickly insert the probe after extraction into the injector, and remove it after thermal desorption.

[0057] The injection port and detector temperatures of the GC-FPD instrument were set to 260℃ and 270℃, respectively. The column oven temperature program was set as follows: maintain at 60℃ for 3 min, increase to 130℃ at 35℃ / min, maintain for 3 min, then increase to 180℃ at 12℃ / min, maintain for 6 min, then increase to 240℃ at 7℃ / min, and finally increase to 260℃ at 5℃ / min. The probe, after the extraction time was completed, was quickly inserted into the GC injector, removed after thermal desorption, and the entire DI-SPME-GC-FPD process took approximately 46 minutes.

[0058] Preferably, to determine the optimal resolution temperature, the injection port temperature is set to 230℃, 240℃, 250℃, 260℃, 270℃, and 280℃ respectively. Figure 9 This is a comparison of analytical temperature data in another specific embodiment of the present invention. Considering the residual analytical temperature and to maximize the probe lifespan, 260°C is selected as the optimal analytical temperature.

[0059] Preferably, to determine the optimal desorption time, thermal desorption is performed for 1 min, 2 min, 3 min, 4 min, 10 min, and 15 min, respectively. Figure 10 This is a thermal desorption comparison experiment data graph from another specific embodiment of the present invention. Considering the desorption residue and to maximize the probe lifetime, 4 minutes is taken as the optimal desorption time.

[0060] By analyzing the relationship between peak area in gas chromatography and pesticide concentration in the working solution, a working curve was plotted. The extraction effect was judged based on the peak area, and the pesticide concentration in the sample was calculated using the working curve. The linear equations for the five organophosphorus pesticides are shown in Table 1.

[0061] Table 1

[0062]

[0063] The extraction conditions of the solid-phase microextraction probe were optimized through experiments to enable its detection and enrichment of organophosphorus pesticide residues in aqueous samples. Combined with gas chromatography-flame photometry (GC-FPD), the rapid and accurate determination of organophosphorus pesticide residues in water systems was achieved.

[0064] In another specific embodiment, the extraction effects of the solid-phase microextraction probe DVB-NVP@UiO-66-(OH)2 obtained in the above embodiments are compared with those of commercial probe 1 (ACAR / PDMS), commercial probe 2 (ACAR / PDMS / DVB), DVB-NVP, and UiO-66-(OH)2. Figure 11 The figure shows the comparative experimental data of extraction effect in another specific embodiment of the present invention. It can be seen that the solid-phase microextraction probe DVB-NVP@UiO-66-(OH)2 obtained by the present invention has the best extraction effect.

[0065] The above are preferred embodiments of this application. Obviously, those skilled in the art can make various modifications and changes to the embodiments of this application without departing from the spirit and scope of this application. In this way, if such modifications and changes fall within the scope of the claims of this application and their equivalents, this application also intends to cover such modifications and changes.

Claims

1. A method for detecting organophosphorus pesticide residues, characterized in that, The detection of organophosphorus pesticide residues in aqueous samples using a solid-phase microextraction probe includes the following steps: S1 Preparation of working solution: Add an appropriate amount of acetone solution to the mixed sample solution of pesticide and water; S2 Extraction: The working solution is transferred to a glass vial, the probe is passed through the vial diaphragm, and the coating material is immersed below the surface of the working solution. Extraction is performed using magnetic stirring at a rotor speed of 1000 rpm. S3 Instrument Setup and Probe Thermal Desorption Application: Set the injection port and detector temperature for gas chromatography, quickly insert the probe after extraction into the injection port, and remove it after thermal desorption; The solid-phase microextraction probe comprises a zirconium-based organometallic framework and copolymer microspheres. The copolymer microspheres are polymerized on the surface of the zirconium-based organometallic framework through a crosslinking agent to form a coating material in which the copolymer microspheres are uniformly distributed on the surface of the zirconium-based organometallic framework. The copolymer microspheres are polymerized from two comonomers, namely divinylbenzene and N-vinylpyrrolidone.

2. The method for detecting organophosphorus pesticide residues according to claim 1, characterized in that, The volume ratio of the comonomers divinylbenzene and N-vinylpyrrolidone is 6:

4.

3. The method for detecting organophosphorus pesticide residues according to claim 1, characterized in that, The solid-phase microextraction probe also includes a carrier bonded to the coating material, the coating material and the carrier being bonded together by an adhesive.

4. The method for detecting organophosphorus pesticide residues according to claim 3, characterized in that, The preparation of the solid-phase microextraction probe includes the following steps: A1. Synthesis of zirconium-based organometallic frameworks; A2. Mix the two comonomers with acetonitrile solution, add the organometallic framework and crosslinking agent, seal, magnetically stir and heat to obtain the coating material; A3. The carrier is pretreated by dipping it in adhesive and bonding it with an appropriate amount of the coating material and then drying it. The carrier and the coating are bonded together twice and dried to obtain a solid-phase microextraction probe.

5. The method for detecting organophosphorus pesticide residues according to claim 4, characterized in that, The crosslinking agent is azobisisobutyronitrile.

6. The method for detecting organophosphorus pesticide residues according to claim 1, characterized in that, The acetone solution described in S1 accounts for 5% of the volume of the working solution.

7. The method for detecting organophosphorus pesticide residues according to claim 1, characterized in that, The extraction time described in S2 is 25 min.

8. The method for detecting organophosphorus pesticide residues according to claim 1, characterized in that, The thermal desorption time mentioned in S3 is 4 minutes.

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