SPME fiber coated with COP-OMe aerogel, its preparation method and application

Abstract

This invention relates to the field of solid-phase microextraction (SPME) technology, and particularly to an SPME fiber coated with COP-OMe aerogel, its preparation method, and its applications. Preparation method: 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde are dissolved in N,N-dimethylformamide to obtain a monomer solution; a metal salt is dissolved in N,N-dimethylformamide to obtain a catalyst solution; S2, the monomer solution and catalyst solution are mixed and added to a capillary containing a fiber carrier. After static reaction, the mixture is freeze-dried, washed, and then vacuum-dried to obtain SPME fiber based on COP-OMe aerogel coating; the fiber is then aged under a protective atmosphere. This invention features mild reaction conditions, a simple synthesis method, low cost, and short preparation time. The prepared product exhibits advantages such as fast extraction efficiency, good extraction performance, and reusability in the extraction of phenolic compounds.

Description

Technical Field

[0001] This invention relates to the field of solid-phase microextraction technology, and in particular to an SPME fiber coated with COP-OMe aerogel, its preparation method, and its application. Background Technology

[0002] Phenolic compounds are a class of organic pollutants widely found in environmental water bodies, soil, and food samples, originating from various sources including industrial wastewater discharge, pesticide use, and food processing. These compounds exhibit toxicity and bioaccumulation; even trace levels in environmental or food samples can pose potential hazards to the ecological environment and human health with prolonged exposure. Therefore, achieving accurate detection of trace phenolic compounds has significant practical importance and application value.

[0003] However, because phenolic compounds are present in extremely low concentrations in samples, direct analysis using detection instruments is easily affected by interference from other components in the sample matrix, leading to insufficient detection sensitivity and decreased accuracy, making it difficult to meet the needs of trace detection. Therefore, before detecting phenolic compounds, effective pre-separation and enrichment of the sample are necessary to increase the concentration of the target analyte, reduce matrix interference, and ensure the reliability of the detection results.

[0004] Currently, commonly used pretreatment technologies for phenolic compounds in the industry mainly include solvent extraction, accelerated solvent extraction, solid-phase extraction, and solid-phase microextraction (SPME). Among them, solvent extraction and accelerated solvent extraction have drawbacks such as large consumption of organic solvents, cumbersome operation, long extraction time, and serious environmental pollution; although solid-phase extraction can achieve a certain enrichment effect, it still requires a certain amount of organic solvents, and the operation process is relatively complex, which is not conducive to the requirements of efficient and green detection.

[0005] SPME, as a novel, green, and multifunctional pretreatment technology, is widely used in the field of trace organic matter pretreatment due to its advantages such as no need for organic solvents, simple operation, fast extraction speed, high enrichment efficiency, and direct interface with detection instruments such as gas chromatography-mass spectrometry (GC-MS). Among various SPME technologies, in-tube SPME has become one of the most widely used forms of SPME due to its large extraction capacity, good operational stability, and ease of automation.

[0006] The core technology of in-tube SPME lies in the fiber carrier inside the tube and the coating material on its surface. The performance of the coating material directly determines key indicators such as extraction efficiency, selectivity, stability, and reusability. An ideal SPME coating material should have a loose and porous structure to expose sufficient active sites and improve the adsorption capacity for target analytes. At the same time, it should also have the characteristics of simple preparation method, low cost, mild reaction conditions, and short reaction time, so as to facilitate industrial production and practical application.

[0007] While a variety of SPME coating materials have been developed in the existing technology, most suffer from problems such as complex preparation processes, high costs, long preparation times, or low extraction efficiency, poor selectivity, and poor reusability for phenolic compounds, making it difficult to meet the practical needs for efficient, rapid, and green detection of trace phenolic compounds. For example, currently used COP coating materials are mostly powdered materials, which usually require physical adhesion and sol-gel methods for coating preparation. The weak physical interactions for fixation affect mechanical stability, and the material powder is prone to agglomeration, while the binder easily blocks the pores, reducing the available adsorption sites for COPs and hindering rapid extraction / desorption.

[0008] Therefore, developing an SPME coating that is simple to prepare, low in cost, has excellent extraction performance, and is reusable is of great significance for promoting the development of phenolic compound detection technology and has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0009] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing an SPME fiber coated with COP-OMe aerogel, its preparation method, and its application.

[0010] The first objective of this invention is to provide a method for preparing SPME fibers coated with COP-OMe aerogel, comprising the following steps: S1. A monomer solution is obtained by dissolving 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde in N,N-dimethylformamide, and a catalyst solution is obtained by dissolving the metal salt in N,N-dimethylformamide. S2. Mix the monomer solution with the catalyst solution, add it into a capillary containing a fiber support, and allow it to react to obtain COP-OMe hydrogel. S3. The COP-OMe hydrogel is freeze-dried, washed, and then vacuum-dried to obtain COP-OMe aerogel. S4. The COP-OMe aerogel is aged at 250°C for 1-2 hours under a protective atmosphere to obtain SPME fibers with COP-OMe aerogel as the coating.

[0011] Furthermore, the molar ratio of 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde is 1:2 to 1:1.

[0012] Further, in step S1, the concentration of the catalyst solution is 30~50 mg / mL, and the volume ratio of the monomer solution to the catalyst solution is 3:1~6:1.

[0013] Furthermore, in step S2, the reaction is allowed to stand at room temperature for 1-30 minutes; the metal salt is an iron salt.

[0014] Furthermore, in step S3, the freeze-drying cold trap temperature is -30~-40℃, and the freeze-drying time is 8-12 hours.

[0015] Furthermore, the protective atmosphere is nitrogen; the temperature is increased from 10°C to 250°C and maintained for 1-2 hours.

[0016] Furthermore, the fiber carrier is a low-cost stainless steel wire etched with concentrated hydrochloric acid; or a nickel-titanium alloy wire or titanium wire etched with a mixed solution of hydrochloric acid and hydrofluoric acid; or an aluminum wire etched with dilute hydrochloric acid; or an aluminum wire etched with nitric acid.

[0017] A second objective of this invention is to provide an SPME fiber coated with COP-OMe aerogel prepared by the above-described preparation method.

[0018] A third objective of this invention is to provide an application of the COP-OMe aerogel SPME coating as described above in the extraction and detection of phenolic compounds.

[0019] Furthermore, the phenolic compound is one or more of 2-nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2,6-dichlorophenol, and 2,4,6-trichlorophenol.

[0020] This invention utilizes an in-situ growth method to prepare COP aerogel coatings, exposing more adsorption sites and effectively improving extraction efficiency. This method uses Fe metal salts as catalysts and 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxyterephthalaldehyde as monomers, enabling rapid gelation in a short time. A capillary tube is used as a glass liner to ensure uniform gel growth on a fiber support. After preparing a hydrogel that encapsulates the fiber support, it is freeze-dried to shrink into an aerogel that adheres tightly to the fiber support. This rapid gelation method overcomes the shortcomings of traditional in-situ growth methods, such as the need for pre-functionalization of the fiber support and long growth time. Furthermore, the absence of binders occupying active sites results in coatings with higher extraction performance.

[0021] In the preparation method provided by the present invention, COP-OMe aerogels of different thicknesses can be obtained as SPME coatings by selecting capillaries of different diameters; and COP-OMe aerogels with different extraction properties can be obtained as SPME coatings by changing the reaction time.

[0022] This preparation method is simple and rapid. COP-OMe aerogel materials are prepared at room temperature using N,N-dimethylformamide as a solvent via a simple sol-gel method. The aerogel network structure is combined with the high selectivity, large adsorption capacity, and rapid adsorption performance of COPs materials to prepare SPME coatings. The method is simple to operate, fast to prepare, and has very good application prospects.

[0023] The preparation method of COP-OMe aerogel is simple, and the loose and porous structure of this aerogel exposes active sites composed of the amino group of 1,3,5-tris(4-aminophenyl)benzene, the aldehyde group of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, methoxy groups, and imine bonds. These sites can selectively enrich phenolic compounds through π-π stacking, hydrogen bonding, and hydrophobic synergistic effects, thereby significantly improving extraction performance. Therefore, combining it with GC-MS has broad application prospects in the field of phenolic compound detection.

[0024] Compared with the prior art, the present invention has the following advantages and effects: The method provided by this invention has the advantages of mild reaction conditions, simple synthesis method, low cost, and short preparation time.

[0025] The SPME fiber coated with COP-OMe aerogel prepared by this invention exhibits advantages such as fast extraction efficiency, good extraction performance, and reusability in the extraction of phenolic compounds, and can be applied to the detection of phenolic compounds in practical complex samples. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the preparation process of the present invention; Figure 2 The image shows a scanning electron microscope (SEM) image of the SPME fibers coated with COP-OMe aerogel prepared in Example 1. Figure 3 The FT-IR spectrum of the SPME fiber coated with COP-OMe aerogel prepared in Example 1; Figure 4 The XRD pattern of the SPME fiber coated with COP-OMe aerogel prepared in Example 1; Figure 5 The N2 adsorption-desorption isotherm spectrum of the SPME fiber coated with COP-OMe aerogel prepared in Example 1; Figure 6The figure shows the relationship between the extraction performance of five phenolic compounds (2-nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2,6-dichlorophenol and 2,4,6-trichlorophenol) on SPME fibers coated with COP-OMe aerogel prepared in Examples 1-3 and Comparative Example 1 (effect of reaction time). Figure 7 The figure shows a comparison of the extraction performance of SPME fibers coated with COP-OMe aerogel prepared in Example 1 and commercially coated PASPME fibers prepared in Comparative Example 1 for five phenolic compounds: 2-nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2,6-dichlorophenol and 2,4,6-trichlorophenol. Figure 8 The extraction kinetics diagram of five phenolic compounds by SPME fibers coated with COP-OMe aerogel prepared in Example 1 is shown. Figure 9 The graph shows a comparison of the extraction performance of five phenolic compounds between SPME fibers coated with COP-OMe aerogel prepared in Example 1 and the coating in Example 1 that has not undergone tube furnace aging. Detailed Implementation

[0027] The following are specific embodiments of the present invention and their accompanying drawings, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0028] Example 1 Preparation of SPME fibers coated with COP-OMe aerogel, such as... Figure 1 As shown: COP-OMe hydrogel was prepared by sol-gel method: 0.03 mmol of 1,3,5-tris(4-aminophenyl)benzene and 0.05 mmol of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde were added to 1.5 mL of N,N-dimethylformamide and ultrasonically mixed. 10 mg of Fe(NO3)3·9H2O was dissolved in 200 μL of N,N-dimethylformamide. The monomer solution was mixed with the catalyst and quickly added to a 0.9 mm capillary tube containing a fiber support (stainless steel wire etched with concentrated hydrochloric acid). After standing at room temperature for 5 minutes, the mixture was washed with water to obtain COP-OMe hydrogel.

[0029] COP-OMe aerogel was synthesized by freeze-drying: the water-washed aerogel was freeze-dried to obtain COP-OMe aerogel, which was then passed through N,N-dimethylformamide, acetone, tetrahydrofuran, ethanol, hydrochloric acid (pH=3) and sodium hydroxide (pH=11) in sequence, and finally washed with water.

[0030] SPME fibers coated with COP-OMe aerogel were obtained by aging them in a tube furnace at 250°C under a nitrogen atmosphere for 1 hour.

[0031] Example 2 The only difference was that the reaction was allowed to stand at room temperature for 15 minutes, otherwise it was the same as in Example 1.

[0032] Example 3 The change was that the reaction was allowed to stand at room temperature for 30 minutes, otherwise it was the same as in Example 1.

[0033] Comparative Example 1 The change was that the reaction was allowed to stand at room temperature for 60 minutes, otherwise it was the same as in Example 1.

[0034] Figure 2 This is a scanning electron microscope (SEM) image of the SPME fibers coated with COP-OMe aerogel prepared in Example 1; from Figure 2 It can be seen that the material is in the form of irregular granules.

[0035] Figure 3 The FT-IR spectrum of the SPME fibers coated with COP-OMe aerogel prepared in Example 1; from Figure 3 It can be seen that 3444 cm -1 and 1677 cm -1 The two absorption bands correspond to the NH stretching vibration of 1,3,5-tris(4-aminophenyl)benzene and the C=O stretching vibration of the 2,5-dimethoxybenzene-1,4-dicarboxaldehyde monomer, respectively. Furthermore, 1604 cm⁻¹ -1 A distinct vibrational signal at the point indicates the formation of a C=N bond, confirming the occurrence of the Schiff base reaction and the synthesis of COP-OMe aerogel.

[0036] Figure 4 The image shows the XRD pattern of the SPME fibers coated with COP-OMe aerogel prepared in Example 1; from Figure 4 It can be seen that the synthesized COP-OMe aerogel has an amorphous structure. Figure 5 The N2 adsorption-desorption isotherm curve of the SPME fibers coated with COP-OMe aerogel prepared in Example 1 is shown below; Figure 5 It can be seen that nitrogen is rapidly adsorbed at lower relative pressures (p / p0<0.1), indicating that the material has a rich microporous structure

[41] ; while at higher relative pressures (p / p0>0.9), its adsorption capacity increases rapidly, indicating that COP-OMe-AG also contains macroporous structures. The isotherm curve is close to the type II isotherm, further confirming the existence of macroporous structures.

[0037] Extraction performance test of phenolic compounds In this embodiment, common contaminating phenolic compounds 2-nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2,6-dichlorophenol, and 2,4,6-trichlorophenol were selected as representatives to test the extraction performance of stainless steel wires etched with concentrated hydrochloric acid prepared in Examples 1-4. The test procedures are as follows: Take 10 mL of salt solution into a headspace extraction vial for solid-phase microextraction, and then add 10 μL of a mixed standard solution of 5 ppm 2-nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2,6-dichlorophenol and 2,4,6-trichlorophenol into the headspace vial. Combine with GC-MS, compare the extraction performance of the COP-OMe aerogel SPME coating prepared in Examples 1-4 for the five phenolic compounds.

[0038] Figure 6 The graph shows the extraction performance of five phenolic compounds—2-nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2,6-dichlorophenol, and 2,4,6-trichlorophenol—on SPME fibers coated with COP-OMe aerogel prepared in Examples 1-3 and Comparative Example 1. Figure 6 It can be seen that the extraction efficiency of the five phenolic compounds decreases with the extension of the coating synthesis time. The reason why the short-time synthesized material exhibits excellent extraction performance is that a large number of unreacted amino and aldehyde groups remain in COP-OMe-AG. Since both of these functional groups have lone electrons, they can effectively serve as binding sites for phenolic compounds, thereby significantly improving the extraction efficiency of phenolic compounds.

[0039] The SPME fibers coated with COP-OMe aerogel prepared in Example 1 were used to continue the following tests.

[0040] 10 mL of salt solution was added to an SPME headspace extraction vial, followed by 10 μL of a mixed standard solution of 5 ppm 2-nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2,6-dichlorophenol, and 2,4,6-trichlorophenol. GC-MS analysis showed that the SPME fiber coated with COP-OMe aerogel prepared in Example 1 exhibited higher extraction performance for the five phenolic compounds than commercially available coated PA SPME fiber (85 μm PA from Supelco, USA). Figure 7 ).

[0041] 10 mL of salt solution was added to a headspace extraction flask for solid-phase microextraction (SPE), followed by 10 μL of a mixed standard solution of 5 ppm 2-nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2,6-dichlorophenol, and 2,4,6-trichlorophenol. The extraction equilibrium time was determined using SPME fibers coated with COP-OMe aerogel prepared in Example 1, and extraction equilibrium was reached within 40 minutes. (e.g.) Figure 8 ) Figure 9 This is a comparison chart showing the extraction performance of five phenolic compounds between the COP-OMe aerogel SPME extraction fiber from Example 1 and the coating from Example 1 that had not undergone tube furnace aging. From... Figure 9 It can be seen that the extraction performance of fibers that have not undergone tubular furnace aging is lower than that of fibers that have undergone tubular furnace aging. This is because the high temperature causes the solvent and oligomers in the coating to evaporate, avoiding contamination and clogging of the pores. It promotes the cross-linking reaction to form a regular porous framework and makes the coating bond more firmly to the metal wire, reducing detachment and ensuring stable extraction.

[0042] A detection method was established using COP-OMe aerogel coating combined with GC-MS. The linear range was 2.0–1.0 × 10⁴ ng / L, the detection limit was as low as 0.18 ng / L, and the enrichment factor was as high as 22037 (as shown in Table 1). Table 1 shows the analytical performance of the established method for detecting five phenolic compounds.

[0043] The actual samples consisted of locally sourced grapes and pears. After crushing and centrifuging, the supernatant was collected to obtain juice for analysis. 2,6-DMP was detected only in the grapes, indicating that this analytical method is suitable for fruit samples with complex matrices. (See Table 2) Table 2. Analytical results of five phenolic compounds in actual samples.

[0044] The tests conducted above show that the prepared COP-OMe aerogel SPME coating has good extraction performance, is simple to prepare, has a short preparation time, can achieve rapid extraction, has good reproducibility of extraction effect, and the results are satisfactory.

[0045] For any points not covered above, existing technologies shall apply.

[0046] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the preparation of a SPME fiber coated with COP-OMe aerogel, characterized in that, Includes the following steps: S1. A monomer solution is obtained by dissolving 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde in N,N-dimethylformamide, and a catalyst solution is obtained by dissolving the metal salt in N,N-dimethylformamide. S2. Mix the monomer solution with the catalyst solution, add it into a capillary containing a fiber support, and allow it to react to obtain COP-OMe hydrogel. S3. The COP-OMe hydrogel is freeze-dried, washed, and then vacuum-dried to obtain COP-OMe aerogel. S4. The COP-OMe aerogel is aged at 250°C for 1-2 hours under a protective atmosphere to obtain SPME fibers with COP-OMe aerogel as the coating.

2. The preparation method according to claim 1, characterized in that, The molar ratio of 1,3,5-tris(4-aminophenyl)benzene to 2,5-dimethoxybenzene-1,4-dicarboxaldehyde is 1:2 to 1:

1.

3. The preparation method according to claim 1, characterized in that, In step S1, the concentration of the catalyst solution is 30~50 mg / mL, and the volume ratio of the monomer solution to the catalyst solution is 3:1~6:

1.

4. The preparation method according to claim 1, characterized in that, In step S2, the reaction is allowed to stand at room temperature for 1-30 minutes; the metal salt is an iron salt.

5. The preparation method according to claim 1, characterized in that, In step S3, the freeze-drying cold trap temperature is -30~-40℃, and the freeze-drying time is 8~12 hours.

6. The preparation method according to claim 1, characterized in that, The protective atmosphere is nitrogen; the temperature is raised from 10°C to 250°C and maintained for 1-2 hours.

7. The preparation method according to claim 1, characterized in that, The fiber carrier is a stainless steel wire etched with concentrated hydrochloric acid; or a nickel-titanium alloy wire or titanium wire etched with a mixed solution of hydrochloric acid and hydrofluoric acid; or an aluminum wire etched with dilute hydrochloric acid; or an aluminum wire etched with nitric acid.

8. An SPME fiber coated with COP-OMe aerogel, prepared by the preparation method according to any one of claims 1-7.

9. An application of SPME fiber coated with COP-OMe aerogel as described in claim 8 in the extraction and detection of phenolic compounds.

10. The application as described in claim 9, characterized in that, The phenolic compound is one or more of 2-nitrophenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2,6-dichlorophenol, and 2,4,6-trichlorophenol.

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