Pretreatment enrichment method of phenolic substances

Abstract

The invention relates to the technical field of testing or analyzing materials by means of measuring chemical or physical properties of the materials, and particularly discloses a pretreatment enrichment method of phenolic substances. The method comprises the following steps: reacting 1, 3, 5-trimethoxy-2, 4, 6-triformyl benzene with 4, 4 '-(naphthalene-2, 7-diyl) diphenylamine to prepare a covalent organic framework adsorbent, and filling a solid-phase extraction column with the adsorbent to carry out pretreatment enrichment on phenolic substances; the compound is large in pore diameter and multiple in adsorption sites, so that the adsorption rate and the adsorption capacity of the compound are improved, and diffusion of pollutant molecules in pores of the compound is facilitated. The pretreatment enrichment method has great application potential in the aspect of detecting organic pollutants in a water system ecological system.

Description

Technical Field

[0001] The present invention relates to the technical field of testing or analyzing materials by means of measuring the chemical or physical properties of the materials, and in particular to a pre-treatment enrichment method for phenolic substances. Background Art

[0002] Currently, analytical tasks face two major challenges: first, complex sample matrices can severely interfere with accurate determination; second, target analytes are present at trace or ultratrace levels, making them difficult to detect with sensitivity using existing instruments and methods. To achieve accurate and sensitive analysis, sample pretreatment is essential prior to instrumental detection. In recent years, sample pretreatment techniques such as solid-phase extraction (SPE) and solid-phase microextraction (SPME) have attracted increasing attention and are widely used in numerous fields, including environmental, food, biological, and pharmaceutical applications. Various advanced materials, such as mesoporous materials, nanomaterials, ionic liquids, aerogels, and metal-organic frameworks (MOFs), have been applied to the development of efficient extraction materials, promoting the advancement of sample pretreatment technologies. Sample pretreatment techniques play an increasingly important role in sample analysis, and the ability to enrich analytes and the degree of sample matrix purification primarily depend on efficient sample pretreatment materials. Therefore, the development of high-performance sample pretreatment materials has been a cutting-edge research direction in this field. In recent years, various advanced materials have been introduced into the field of sample pretreatment, resulting in the development of a variety of high-performance extraction materials.

[0003] Phenolic endocrine disruptors (EDCs) pose a serious threat to human health by mimicking endogenous hormones and interfering with the function of endocrine organs. They can cause reproductive dysfunction, birth defects, metabolic disorders, and some malignant tumors. Therefore, there is a great demand for rapid, simple, accurate, and sensitive analytical techniques to monitor EDCs in diverse sample matrices. Due to their trace levels in food and water matrices, direct identification and quantification are challenging. Therefore, there is an urgent need for efficient and sensitive sample pretreatment methods to extract and enrich the target analytes and remove major interferences prior to instrumental analysis. As one of the most widely used sample pretreatment techniques, solid-phase extraction (SPE) is advantageous for trace analysis in complex sample matrices due to its rapid phase separation, simplicity, high enrichment factor, low cost, and availability of a wide range of highly effective adsorbents. The effectiveness of SPE depends crucially on the adsorbent employed, which serves as the core and foundation for preconcentration and enrichment of target analytes.

[0004] Chinese patent 201911155019.2 discloses a method for preparing a highly efficient adsorption material for bisphenol compounds and its application. The preparation method comprises: fully mixing a mixed functional monomer and a hydrophilic organic framework material in an organic solvent, adding a cross-linking agent and an initiator, deoxygenating, and heating the reaction to obtain a composite material for adsorbing bisphenol compounds. The composite material prepared by this invention has stable chemical properties, good hydrophilicity, high porosity, and strong adsorption performance for bisphenol chemicals. The raw materials used in this invention are low in cost, the material preparation process is simple, the adsorption rate is fast, the adsorption capacity is high, and it is easy to recycle. As an efficient adsorption material, it can be used for the rapid enrichment and removal of bisphenol compounds in an aqueous environment, and can also be used as an extractant in a pretreatment process. Combined with instrumental analysis, a highly sensitive detection method for bisphenol substances is established.

[0005] Chinese Patent 202210135489.8 discloses an adsorbent, its preparation method, and application, belonging to the field of analytical detection technology. The method comprises: obtaining mesoporous carbon nitride (MCN); dissolving the MCN in a first solvent to obtain a magnetic mesoporous carbon nitride (MCN) solution; mixing the MCN solution with CoCl2·6H2O and FeCl3·6H2O, and then adjusting the pH to obtain a mixed solution; and reacting the mixed solution to obtain an adsorbent. An MCN / CoFe2O4 magnetic solid-phase extraction adsorbent was prepared by hydrothermal synthesis. MCN / CoFe2O4 was used as an MSPE adsorbent, and combined with high-performance liquid chromatography-variable wavelength detection, a new method for analyzing bisphenol estrogens (BPs) in water environments was established. This method can simply, efficiently, and economically analyze BPs in water environments, providing new ideas for the enrichment and purification of organic pollutants in water environments and breaking through the bottleneck of BPs sample pretreatment.

[0006] The types of adsorbents in the existing technology include bonded silica gel, molecularly imprinted polymers, carbon nanotubes, etc. However, bonded silica gel has a narrow scope of application, molecularly imprinted polymers can only selectively adsorb pollutants in water, and carbon nanotubes have poor dispersion. Therefore, it is necessary to develop a covalent organic framework adsorbent with good enrichment effect for pretreatment of phenolic substances in water. Summary of the Invention

[0007] In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a pretreatment enrichment method for phenolic substances.

[0008] The covalent bonds in covalent organic framework compounds (COFs) can provide good chemical stability, allowing COFs to remain stable under complex and harsh environmental conditions; secondly, the ordered crystal structure and uniform pores enable COFs to fully contact guest molecules, which is conducive to the rapid diffusion of reactants; the large specific surface area can expose more active sites, allowing it to fully interact with guest substances. In the present invention, 1,3,5-trimethoxy-2,4,6-triformylbenzene is reacted with 4,4'-(naphthalene-2,7-diyl)diphenylamine to prepare a covalent organic adsorbent. The resulting compound exhibits extremely high adsorption capacity due to its unique large pore size and skeleton structure. The compound has a large pore size and many adsorption sites, so the adsorption capacity of phenolic substances is large. The large number of carbon-nitrogen double bond functional groups in the structure can interact with phenolic substances to form hydrogen bonds and π-π interactions to achieve rapid adsorption of the target. The large pore size of the compound helps to improve its adsorption rate and adsorption capacity, and is more conducive to the diffusion of pollutant molecules in its pores. The adsorbent prepared by the present invention can still exhibit good adsorption capacity under extreme conditions, indicating its excellent chemical stability. This pretreatment enrichment method has great application potential in the detection of organic pollutants in aquatic ecosystems.

[0009] The technical solution of the present invention:

[0010] A pretreatment and enrichment method for phenolic substances comprises the following steps:

[0011] S1: 5-10 parts by weight of 1,3,5-trimethoxy-2,4,6-triformylbenzene and 10-18 parts by weight of 4,4'-(naphthalene-2,7-diyl)diphenylamine are added to a mixed solution of 200-350 parts by weight of ethanol and dimethyl sulfoxide, stirred for 10-30 minutes, vacuumized, and then injected with nitrogen. The mixture is heated to 80-120° C. and stirred for 24-72 hours under a nitrogen atmosphere. After the reaction is completed, the mixture is cooled to room temperature and centrifuged, the supernatant is collected, and the mixture is added to 50-100 parts by weight of N,N-dimethylformamide, heated to 100-130° C. and stirred for 1-2 hours, and then 100-150 parts by weight of ethanol are added and stirred at 80-100° C. for 1-2 hours to exchange N,N-dimethylformamide. After the stirring is completed, the mixture is cooled to room temperature, centrifuged, the lower precipitate is collected, and dried to obtain a covalent organic framework adsorbent;

[0012] S2 weighs a covalent organic framework adsorbent as a solid phase extraction adsorbent, fills it into an empty solid phase extraction column, activates the solid phase extraction column with ethanol and water, and then adds a phenolic substance solution for pretreatment and enrichment. The target substance is adsorbed onto the covalent organic framework adsorbent, and the unadsorbed impurities are discharged as waste liquid. The target substance is eluted with ethanol, and the eluate is collected and blown dry before proceeding to the next test.

[0013] Furthermore, the mass ratio of ethanol to dimethyl sulfoxide in step S1 is 1.5 to 3:1.

[0014] Furthermore, in step S1, the centrifugal speed is 8000-10000 rpm, and the centrifugal time is 5-15 min.

[0015] Furthermore, in step S1, the drying temperature is 25-35° C., and the drying time is 12-24 hours.

[0016] Furthermore, the phenolic substance in step S2 includes any one of bisphenol A, bisphenol B, bisphenol S, bisphenol AF, octylphenol, and nonylphenol.

[0017] Furthermore, in step S2, the amount of the covalent organic framework adsorbent added is 0.01 to 10 parts by weight.

[0018] Furthermore, in step S2, the mass ratios of ethanol to adsorbent and water to adsorbent are 100-500:1 and 100-300:1, respectively.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) In the present invention, 1,3,5-trimethoxy-2,4,6-triformylbenzene is reacted with 4,4'-(naphthalene-2,7-diyl)diphenylamine to prepare a covalent organic adsorbent. The resulting compound exhibits extremely high adsorption capacity due to its unique macropore size and structure.

[0021] (2) The covalent organic compound has a large pore size and numerous adsorption sites, resulting in a high adsorption capacity for phenolic substances. The large number of carbon-nitrogen double bond functional groups in the structure can interact with phenolic substances to form hydrogen bonds and π-π interactions, thereby achieving rapid adsorption of the target substance. The large pore size of the compound helps to increase its adsorption rate and adsorption capacity, and is more conducive to the diffusion of pollutant molecules within its pores;

[0022] (3) The adsorbent prepared by the present invention can still show good adsorption capacity under extreme conditions, indicating its excellent chemical stability. This pretreatment enrichment method has great application potential in the detection of organic pollutants in aquatic ecosystems. DETAILED DESCRIPTION

[0023] Hereinafter, the technical solutions of the present invention will be described in detail through specific embodiments. However, it should be clearly stated that these embodiments are provided for illustration only and are not to be construed as limiting the scope of the present invention.

[0024] The parameters of some raw materials in the embodiment of the present invention are as follows:

[0025] Carbon nanotubes, model: XFS05, Xianfeng Nano.

[0026] Comparative Example 1

[0027] A pretreatment and enrichment method for phenolic substances comprises the following steps:

[0028] Weigh 0.1 g of carbon nanotubes as a solid phase extraction adsorbent and fill them into an empty solid phase extraction column. Activate the solid phase extraction column with 20 mL of anhydrous ethanol and 20 mL of water, then add 30 mg / L of phenolic substance solution for pretreatment and enrichment. The target substance is adsorbed onto the covalent organic framework adsorbent, and the unadsorbed impurities are discharged as waste liquid. Elute the target substance with 10 mL of anhydrous ethanol, collect the eluate, blow dry it with nitrogen, and proceed to the next test.

[0029] The phenolic substance includes any one of bisphenol A, bisphenol B, bisphenol S, bisphenol AF, octylphenol and nonylphenol.

[0030] Example 1

[0031] A pretreatment and enrichment method for phenolic substances comprises the following steps:

[0032] S1: 7.5 g of 1,3,5-trimethoxy-2,4,6-triformylbenzene and 14 g of 4,4'-(naphthalene-2,7-diyl)diphenylamine were weighed and added to a mixed solution of 215 mL of anhydrous ethanol and dimethyl sulfoxide (volume ratio = 2:1), stirred for 30 min, evacuated, and then injected with nitrogen. The mixture was heated to 100°C and stirred for 48 h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature and centrifuged at 10,000 rpm for 10 min. The supernatant was collected and added to 100 mL of N,N-dimethylformamide. The mixture was heated to 120°C and stirred for 2 h. 150 mL of anhydrous ethanol was added and stirred at 85°C for 2 h to exchange N,N-dimethylformamide. After the stirring was completed, the mixture was cooled to room temperature and centrifuged at 10,000 rpm for 10 min. The lower precipitate was collected and dried at 30°C for 12 h to obtain a covalent organic framework adsorbent.

[0033] S2 weighed 0.1g of covalent organic framework adsorbent as solid phase extraction adsorbent, filled it into an empty solid phase extraction column, activated the solid phase extraction column with 20mL of ethanol and 20mL of water, and then added 30mg / L of phenolic substance solution for pretreatment and enrichment. The target substance was adsorbed onto the covalent organic framework adsorbent, and the unadsorbed impurities were discharged as waste liquid. The target substance was eluted with 10mL of ethanol, and the eluent was collected and dried with nitrogen before proceeding to the next test.

[0034] The phenolic substance in step S2 includes any one of bisphenol A, bisphenol B, bisphenol S, bisphenol AF, octylphenol, and nonylphenol.

[0035] Example 2

[0036] A pretreatment and enrichment method for phenolic substances comprises the following steps:

[0037] S1 Weigh 7.5 g of 1,3,5-trimethoxy-2,4,6-triformylbenzene and 14 g of 4,4'-(naphthalene-2,7-diyl)diphenylamine and add them to a mixed solution of 215 mL of anhydrous ethanol and dimethyl sulfoxide (volume ratio = 2:1), stir for 30 minutes, evacuate, inject nitrogen, heat to 100 ° C under a nitrogen atmosphere and stir for 48 hours. After the reaction is completed, cool to room temperature and centrifuge at 10000 rpm for 10 minutes. Collect the supernatant and add it to 100 mL of N,N-dimethylformamide. Heat to 120 ° C and stir for 2 hours. Then add 150 mL of anhydrous ethanol and continue stirring at 85 ° C for 2 hours to exchange N,N-dimethylformamide. After stirring, cool to room temperature and centrifuge at 10000 rpm for 10 minutes. Collect the lower precipitate and dry at 30 ° C for 12 hours to obtain a covalent organic framework adsorbent;

[0038] S2 weighed 0.05 g of covalent organic framework adsorbent as a solid phase extraction adsorbent, filled it into an empty solid phase extraction column, activated the solid phase extraction column with 20 mL of ethanol and 20 mL of water, and then added 30 mg / L of phenolic substance solution for pretreatment and enrichment. The target substance was adsorbed onto the covalent organic framework adsorbent, and the unadsorbed impurities were discharged as waste liquid. The target substance was eluted with 10 mL of ethanol, and the eluate was collected and dried with nitrogen before proceeding to the next test.

[0039] The phenolic substance in step S2 includes any one of bisphenol A, bisphenol B, bisphenol S, bisphenol AF, octylphenol, and nonylphenol.

[0040] Example 3

[0041] A pretreatment and enrichment method for phenolic substances comprises the following steps:

[0042] S1 Weigh 7.5 g of 1,3,5-trimethoxy-2,4,6-triformylbenzene and 14 g of 4,4'-(naphthalene-2,7-diyl)diphenylamine and add them to a mixed solution of 215 mL of anhydrous ethanol and dimethyl sulfoxide (volume ratio = 2:1), stir for 30 minutes, evacuate, inject nitrogen, heat to 100 ° C under a nitrogen atmosphere and stir for 48 hours. After the reaction is completed, cool to room temperature and centrifuge at 10000 rpm for 10 minutes. Collect the supernatant and add it to 100 mL of N,N-dimethylformamide. Heat to 120 ° C and stir for 2 hours. Then add 150 mL of anhydrous ethanol and continue stirring at 85 ° C for 2 hours to exchange N,N-dimethylformamide. After stirring, cool to room temperature and centrifuge at 10000 rpm for 10 minutes. Collect the lower precipitate and dry at 30 ° C for 12 hours to obtain a covalent organic framework adsorbent;

[0043] S2 weighed 0.15g of covalent organic framework adsorbent as a solid phase extraction adsorbent, filled it into an empty solid phase extraction column, activated the solid phase extraction column with 20mL of ethanol and 20mL of water, and then added 30mg / L of phenolic substance solution for pretreatment and enrichment. The target substance was adsorbed onto the covalent organic framework adsorbent, and the unadsorbed impurities were discharged as waste liquid. The target substance was eluted with 10mL of ethanol, and the eluent was collected and dried with nitrogen before proceeding to the next test.

[0044] The phenolic substance in step S2 includes any one of bisphenol A, bisphenol B, bisphenol S, bisphenol AF, octylphenol, and nonylphenol.

[0045] Test Example 1

[0046] Bisphenol A, bisphenol B, bisphenol S, bisphenol AF, octylphenol, and nonylphenol were respectively prepared into 0.1 mg / L standard solutions to replace the phenolic substance solutions in the above-mentioned control examples and embodiments. The pretreatment methods in the above-mentioned control examples and embodiments were used for enrichment and then the recovery rates were tested. A mixed standard solution of five bisphenol substances was used for sample loading, the sample volume was 50 mL, the sample flow rate was 1 mL / min, and the target substance was adsorbed on the adsorbent in the solid phase extraction column. The eluate was dried with nitrogen and then redissolved with 1 mL of ethanol. The solution was passed through a 0.45 μm organic filter membrane, and 20 μL of the sample solution was taken for high performance liquid chromatography analysis. Taking a 0.1 mg / L mixed standard solution as an example, a sample without the detected target substance was used as a blank, and the mixed solution was used for spike recovery experiments. The spike levels of bisphenol A, bisphenol B, and bisphenol S were 2.5 μg / L, and the spike levels of bisphenol AF, octylphenol, and nonylphenol were 5.0 μg / L. The recovery rates of the various phenolic substances are shown in Table 1.

[0047] Table 1 Recovery rates of phenolic compounds by various pretreatment enrichment methods

[0048]

[0049]

[0050] The recovery rate test shows that the pretreatment enrichment method for phenolic substances has high practical value and can achieve efficient separation and enrichment of phenolic compounds in water environments. The covalent organic compounds in Examples 1 to 3 have lone pairs of electrons, which can act as Lewis bases to bind to acidic phenolic molecules. This acid-base interaction also plays an important role in the adsorption process. The hydrogen bond formed between the phenolic hydroxyl group in the phenolic substance and the covalent organic compound is still the main factor in the adsorption force, and the π-π interaction generated by the aromatic ring and the benzene ring in the structure is also an important part of the adsorption effect. In the embodiment, due to the larger pores of the prepared compound, the phenolic substance can diffuse into it faster, so the adsorption is stronger, which leads to better pretreatment enrichment effect.

[0051] Test Example 2

[0052] Adsorption experiments were performed on the adsorbents obtained in the control examples and the examples under different pH and ionic strengths to verify their enrichment effects on phenolic substances under different chemical environments. The adsorbent in each example was added to 40 mL of 30 mg / L bisphenol S or bisphenol A solutions with pH = 4, 7, and 11, and the mixture was shaken in a water bath at 25° C. and 220 rpm for 3 h to reach adsorption equilibrium. Subsequently, 1 mL of the suspension was extracted and filtered through a 0.45 μm organic filter membrane, and 20 μL of the sample was analyzed by high performance liquid chromatography to test its concentration. For the ionic strength test, the adsorbent in each example was added to 40 mL of 30 mg / L NaCl solution of bisphenol S or bisphenol A, with a NaCl concentration of 1 mol / L. The mixture was shaken in a water bath at 25° C. and 220 rpm for 3 h to reach adsorption equilibrium. Subsequently, 1 mL of the suspension was extracted and filtered through a 0.45 μm organic filter membrane, and 20 μL of the sample was analyzed by high performance liquid chromatography to test its concentration. Adsorption capacity (mg / g) = (concentration at adsorption equilibrium - initial concentration) * volume of bisphenol mixed solution / mass of adsorbent. Specific test results are shown in Table 2. Table 2 Enrichment effect of different adsorbents on bisphenols under different chemical environments

[0053]

[0054] Adsorbents are negatively charged, and their negative charge increases with increasing pH. At the same time, BPS and BPA may also be deprotonated at higher pH values. Under these conditions, negatively charged BPS and BPA are difficult to adsorb on the negatively charged COF surfaces. Electrostatic repulsion may be the reason for the decreased adsorption capacity at high pH values. However, electrostatic interactions cannot fully explain the adsorption of BPS / BPA on COFs under acidic conditions. Under acidic conditions, since BPS / BPA exists in molecular form, electrostatic attraction does not occur between COFs and the bisphenol compounds. Additional interactions occur between the pollutants, allowing COFs to maintain a high adsorption capacity over a wide pH range.

[0055] It is well known that environmental water bodies contain not only various organic pollutants but also high concentrations of salts, which may affect the adsorbent's ability to enrich pollutants. Therefore, in this experiment, the effect of ionic strength on the adsorption of bisphenol S and bisphenol A by COFs was also studied. With the increase of NaCl concentration, the adsorption affinity did not change significantly. Many studies have shown that an increase in ionic strength can affect the adsorption of organic pollutants to a certain extent through salting-out effect or electrostatic screening effect. In the enrichment experiments conducted on the adsorbent prepared in the examples, the ionic strength had little effect on the adsorption of bisphenol S and bisphenol A by COFs, indicating that the two opposing effects are equivalent or too weak. In addition, the adsorption of bisphenol substances on COFs is driven by hydrogen bonds and π-π interactions. Therefore, changing the ionic strength within a small range does not significantly change these factors, so the adsorption effect is not significantly affected. The prepared adsorbent can still show good adsorption capacity under extreme chemical conditions, which proves its excellent chemical stability and will be more advantageous when facing complex environmental conditions.

Claims

1. A method for pre-treatment and enrichment of phenolic substances, characterized in that: A covalent organic framework adsorbent was prepared by reacting 1,3,5-trimethoxy-2,4,6-triformylbenzene with 4,4'-(naphthalene-2,7-diyl)diphenylamine, and the adsorbent was filled in a solid phase extraction column for pretreatment and enrichment of phenolic substances.

2. The pretreatment enrichment method according to claim 1, wherein The steps include: S1: 1,3,5-trimethoxy-2,4,6-triformylbenzene and 4,4'-(naphthalene-2,7-diyl)diphenylamine are added to a mixed solution of ethanol and dimethyl sulfoxide, stirred for 10-30 minutes, then vacuumed and injected with nitrogen. The mixture is heated to 80-120°C and stirred for 24-72 hours under a nitrogen atmosphere. After the reaction is completed, the mixture is cooled to room temperature and centrifuged. The supernatant is collected and added to N,N-dimethylformamide. The mixture is heated to 100-130°C and stirred for 1-2 hours. Ethanol is then added and stirred at 80-100°C for 1-2 hours to exchange N,N-dimethylformamide. After the stirring is completed, the mixture is cooled to room temperature, centrifuged, the lower precipitate is collected, and dried to obtain a covalent organic framework adsorbent. S2 weighs a covalent organic framework adsorbent as a solid phase extraction adsorbent, fills it into an empty solid phase extraction column, activates the solid phase extraction column with ethanol and water, and then adds a phenolic substance solution for pretreatment and enrichment. The target substance is adsorbed onto the covalent organic framework adsorbent, and the unadsorbed impurities are discharged as waste liquid. The target substance is eluted with ethanol, and the eluate is collected and blown dry before proceeding to the next test.

3. The pretreatment enrichment method according to claim 2, wherein: The mass ratio of ethanol to dimethyl sulfoxide in step S1 is 1.5 to 3:

1.

4. The pretreatment enrichment method according to claim 2, wherein: In step S1, the centrifugal speed is 8000-10000 rpm, and the centrifugal time is 5-15 minutes.

5. The pretreatment enrichment method according to claim 2, wherein: In step S1, the drying temperature is 25-35° C., and the drying time is 12-24 hours.

6. The pretreatment enrichment method according to claim 2, wherein: The phenolic substance in step S2 includes any one of bisphenol A, bisphenol B, bisphenol S, bisphenol AF, octylphenol, and nonylphenol.

7. The pretreatment enrichment method according to claim 2, wherein: In the step S2, the amount of the covalent organic framework adsorbent added is 0.01 to 10 parts by weight.

8. The pretreatment enrichment method according to claim 2, wherein: In step S2, the mass ratios of ethanol to adsorbent and water to adsorbent are 100-500:1 and 100-300:1, respectively.

Images