Sample pretreatment technology and analysis method of triazine herbicide

Abstract

The invention belongs to the technical field of chemical analysis, and particularly relates to a sample pretreatment technology and an analysis method of a triazine herbicide. The ionic type conjugated microporous polymer is formed by polymerization of 2, 4, 6-tri (4-ethynyl phenyl)-1, 3, 5-triazine (TEPT) and 1, 3-bis (4-bromophenyl)-1H-imidazole-3-onium bromide, and the ionic type conjugated microporous polymer is formed by polymerization of 1, 3-bis (4-bromophenyl)-1H-imidazole-3-onium bromide. The ionic type conjugated microporous polymer is prepared by cross coupling of 2, 4, 6-tri (4-ethynyl phenyl)-1, 3, 5-triazine (TEPT) and 1, 3-bis (4-bromophenyl)-1H-imidazole-3-onium bromide, and the ionic type conjugated microporous polymer is prepared by cross coupling of 2, 4, 6-tri (4-ethynyl phenyl)-1, 3, 5-triazine (TEPT) and 1, 3-bis (4-bromophenyl)-1H- The ionic conjugated microporous polymer is used for preparing a solid phase extraction (SPE) small column, an SPE-LC-MS / MS is established after the extraction condition is optimized, and the SPE-LC-MS / MS is used for selective enrichment and accurate detection of trace triazine herbicides in environmental water bodies (such as underground water and waste water) and food samples.

Description

Technical Field

[0001] This invention belongs to the field of chemical analysis technology, specifically relating to a sample pretreatment technique and analytical method for triazine herbicides. Background Technology

[0002] Triazine herbicides are widely used in traditional agriculture due to their broad spectrum of weed control, wide applicability to various crops, and low cost, playing a vital role in the cultivation of various crops such as corn, soybeans, sugarcane, and fruit trees. However, these compounds generally have low volatility, strong environmental persistence, and are prone to accumulation in organisms, remaining in soil and aquatic environments for extended periods, thus posing a potential threat to ecosystems, aquatic organisms, and human health. Currently, strict limits have been established for the residue levels of triazine herbicides in the environment and food. Because environmental samples often have complex matrices and the target pollutant concentrations are typically low, accurate detection using direct instrumental analysis is often difficult.

[0003] Before instrumental analysis, sample pretreatment is usually required. This helps to enrich target analytes, eliminate matrix interference, and thus improve the sensitivity and accuracy of analytical methods. Common sample pretreatment techniques include solid-phase extraction (SPE), solid-phase microextraction (SPME), and magnetic solid-phase extraction (MSPE). Among these, solid-phase extraction technology is widely used in environmental, food, and pharmaceutical analysis due to its advantages such as ease of operation, high efficiency, and low solvent consumption. Developing efficient and stable solid-phase extraction adsorption materials is crucial. Conjugated microporous polymers (CMPs), as a new type of porous organic material, possess characteristics such as high specific surface area, abundant microporous structure, tunable chemical composition, and good chemical stability, showing broad application prospects in electrochemistry, adsorption separation, catalysis, and optoelectronics.

[0004] In recent years, based on the excellent adsorption performance of CMPs, studies have shown that they are used as adsorbent materials for solid-phase microextraction (SPE) or magnetic solid-phase extraction (MSPE) for the detection and analysis of organophosphorus pesticides and carbamate pesticides in the environment. Ionic conjugated microporous polymers (CMPs) are a new type of material that combines ionic properties with a porous structure, and their physicochemical properties meet the requirements of efficient solid-phase extraction adsorbents. However, ionic conjugated microporous polymers still face the following problems in practical applications: poor mass transfer kinetics, which prolongs the extraction equilibrium time and severely limits the overall efficiency of the detection process; difficulty in synergistically optimizing the structural stability and regeneration performance of the material, leading to skeletal collapse and loss of active sites after adsorption-desorption cycles, resulting in a significant decrease in adsorption capacity. In addition, research on this type of material in sample pretreatment is still relatively limited, and its extraction performance and application potential for triazine herbicides in complex matrices require further exploration. Summary of the Invention

[0005] The purpose of this invention is to provide a sample pretreatment technique and analytical method for triazine herbicides, thereby overcoming the shortcomings of existing technologies. A novel ionic conjugated microporous polymer is prepared by polymerizing two monomers, 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (TEPT) and 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromium bromide (BIBM), through a Sonogashira-Hagihara cross-coupling reaction. This polymer is then used for the analytical study of seven triazine herbicides.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides an ionic conjugated microporous polymer having the following repeating structural units: .

[0007] In some other embodiments, the ionic conjugated microporous polymer is formed by cross-coupling of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (TEPT) and 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromodium (BIBM).

[0008] In some other embodiments, the molar ratio of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (TEPT) to 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromodium (BIBM) is (0.7-0.75):(0.9-1.0).

[0009] For example, the molar ratio of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine and 1,3-bis(4-bromophenyl)-1H-imidazol-3-bromodium is 0.7:0.9, 0.72:0.96 or 0.75:1.0; preferably 0.72:0.96.

[0010] In a second aspect, the present invention provides a method for preparing the ionic conjugated microporous polymer described in the first aspect, comprising the following steps: Under an inert atmosphere, 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (TEPT), 1,3-bis(4-bromophenyl)-1H-imidazol-3-bromium, cuprous iodide, and tetra(triphenylphosphine)palladium were mixed, and after gas replacement with solvent, the mixture was heated to react. After the reaction was completed, the mixture was cooled to room temperature and purified to obtain the final product.

[0011] In some other embodiments, the molar ratio of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromium, cuprous iodide, and tetra(triphenylphosphine)palladium is (0.7-0.75): (0.9-1.0): (0.1-0.15): (0.05-0.08). The solvent is a mixture of N,N-dimethylformamide and triethylamine, with a volume ratio of 1:(1-2).

[0012] For example, the molar ratios of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromium, cuprous iodide, and tetra(triphenylphosphine)palladium are 0.7:0.9:0.1:0.05, 0.72:0.96:0.11:0.06, or 0.75:1.0:0.15:0.08; and the volume ratios of N,N-dimethylformamide and triethylamine are 1:1 or 1:2. Preferably, the molar ratio of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromium, cuprous iodide and tetra(triphenylphosphine)palladium is 0.72:0.96:0.11:0.06, and the volume ratio of N,N-dimethylformamide and triethylamine is 1:1.

[0013] In some other embodiments, the heating reaction is carried out at a temperature of 90-110°C for a time of 70-80 h; For example, the temperature of the heating reaction is 90, 100 or 110°C, and the time is 70, 72, 75 or 80 h; preferably, the temperature of the heating reaction is 100°C, and the time is 72 h.

[0014] The purified solution was washed 2-5 times each with N,N-dimethylformamide, tetrahydrofuran, methanol, and acetone, then soaked in a saturated sodium bromide solution with stirring, followed by multiple washes with water and methanol. Finally, it was subjected to Soxhlet extraction with methanol and tetrahydrofuran, and then vacuum dried.

[0015] Specifically, the purification steps are as follows: The material is washed three times each with N,N-dimethylformamide, tetrahydrofuran, methanol, and acetone to remove unreacted monomers and catalysts; then, the material is immersed in a saturated sodium bromide solution and magnetically stirred for 20-30 hours to fully exchange any unreplaced Br₂. - After washing with water and methanol multiple times, the material was extracted with methanol and tetrahydrofuran for 45-50 h. Finally, the obtained material was dried in a vacuum drying oven at 55-65℃ for 10-15 h until fully dried.

[0016] Thirdly, this invention provides the application of the ionic conjugated microporous polymer described in the first aspect in the pretreatment and analysis of triazine herbicides. Based on the triazine conjugated backbone and imidazole ionic groups of the polymer, multiple intermolecular forces are formed with the target analyte, significantly improving the adsorption performance and exhibiting excellent anti-interference ability in complex matrices such as environmental water and fruit juice.

[0017] Fourthly, the present invention provides an analytical method for triazine herbicides, comprising the following steps: The ionic conjugated microporous polymer described in the first aspect was used as a solid-phase extractant. The sample to be tested was added to extract and enrich triazine herbicides. Desorption solvent was added for elution. The eluent was collected and dried with nitrogen to obtain the residue. After redissolution and filtration, the residue was quantitatively analyzed by liquid chromatography-tandem mass spectrometry.

[0018] Specifically, an ionic conjugated microporous polymer was immobilized in a solid-phase extraction column, which was then activated sequentially with acetonitrile and water. The sample to be tested was added to the activated solid-phase extraction column and loaded under vacuum. After loading, the solid-phase extraction column was rinsed with water and then dried to remove any residual water. The enriched triazine herbicides were eluted with a desorption solvent and dried with nitrogen to obtain the residue. After redissolving and filtration, the residue was quantitatively analyzed by liquid chromatography-tandem mass spectrometry.

[0019] More specifically, the activation rate with acetonitrile and water is 0.4-0.6 mL / min; methanol is used for ultrasonic dissolution and vortex mixing and resolution, and filtration is performed using an organic phase filter membrane of 0.2-0.25 μm.

[0020] In some other embodiments, the triazine herbicide is one or more of atrazine, diquat, atrazine, chlorpyrifos, chlorpyrifos, terbufos, and chlorpyrifos; The samples to be tested are fruit juice or water; specifically, fruit juice includes peach juice and grape juice; water includes groundwater and wastewater.

[0021] Before solid-phase extraction, the samples to be tested are pretreated by filtering them through an aqueous filter membrane with a pore size of 0.4-0.5 μm and then refrigerating them for later use.

[0022] The pH of the sample to be tested should be 4-6; 5-35 L of sample should be added per gram of adsorbent; the addition rate of the sample should be 1-2 mL / min. -1 The desorption solvent is one of acetonitrile, acetone, ethyl acetate, dichloromethane, and n-hexane; the volume ratio of the desorption solvent to the sample is (2-10):500; the elution time is 15-20 min.

[0023] In some other embodiments, the liquid chromatography conditions are as follows: using an Agilent EclipsePlus C18 column, with mobile phases A and B, wherein mobile phase A is acetonitrile and mobile phase B is formic acid-water mixture, and a gradient elution program is used as follows: 0–6.0 min, 25% mobile phase A; 6.0–6.1 min, 75%–25% mobile phase A; and 6.1–9.0 min, 25% mobile phase A; the flow rate is 0.2–0.4 mL / min. -1 The column temperature is 25-30℃, and the injection volume is 1-3 μL; Specifically, the mobile phase B is 0.1% formic acid in water; the flow rate is 0.2, 0.3, or 0.4 mL / min. -1 The column temperature is 25 or 30℃, and the injection volume is 1, 2 or 3 μL.

[0024] Mass spectrometry conditions: electrospray ionization source was used, and quantification was performed in selected multiple reaction monitoring mode; desiccator temperature was 220-270℃, and desiccator flow rate was 3-6 L·min. -1 Nebulizer voltage: 25-30 psi, capillary voltage: 3000-4000V, sheath flow rate: 10-12 L·min -1 The sheath gas temperature is 180-220℃.

[0025] Specifically, the dryer temperature is 250℃, and the drying gas flow rate is 5 L·min. -1 The atomizer voltage is 30 psi, the capillary voltage is 3500 V, and the sheath flow rate is 11 L·min. -1 The sheath gas temperature was 200℃. The MRM parameters, including qualitative ions, quantitative ions, their fragmentation voltage, collision energy, and retention time, are listed in Table 1.

[0026] Under optimized conditions, this method exhibits high sensitivity, wide linear range, and good reproducibility in the detection of seven triazine herbicides, meeting the requirements for accurate quantification of trace pollutants in food and environmental samples.

[0027] The beneficial effects of this invention are: (1) This invention uses 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine and 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromium as monomers and synthesizes a novel ionic conjugated microporous polymer (i-CMP) with both imidazolium ionic groups and a triazine conjugated skeleton via a Sonogashira-Hagihara coupling reaction. This allows it to form strong π-π interactions with triazine herbicides, providing a favorable foundation for subsequent enrichment and detection processes. Furthermore, this material possesses excellent thermal stability and a rich microporous structure, providing a stable adsorption platform for high-capacity, reusable solid-phase extraction.

[0028] (2) This invention utilizes the ionic conjugated microporous polymer to prepare solid phase extraction (SPE) columns, and after optimizing the extraction conditions, establishes a new method for the determination of triazine herbicides using SPE-LC-MS / MS. This method has been successfully applied to the selective enrichment and accurate detection of trace triazine herbicides in environmental water bodies (such as groundwater and wastewater) and food samples. The method has high sensitivity and good reproducibility, providing reliable technical support for the monitoring of environmental and food safety. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 These are SEM, TEM, and EDS images of i-CMP in Embodiment 1 of the present invention; where a is an SEM image, b is a TEM image, and c is an EDS image. Figure 2 The infrared spectra of i-CMP and two monomers in Embodiment 1 of the present invention are shown below. Figure 3 The images show the XRD, XPS, and N1s XPS spectra of i-CMP in Embodiment 1 of the present invention, where a is the XRD spectrum, b is the XPS spectrum, and c is the N1s XPS spectrum. Figure 4 Thermogravimetric analysis diagram of i-CMP in Embodiment 1 of the present invention; Figure 5 The diagram shows the specific surface area and pore size distribution of the i-CMP material in Example 1 of this invention, where a is the N2 adsorption-desorption curve and b is the pore size distribution diagram. Figure 6 The diagram shows the optimization of extraction conditions under adsorption conditions in Example 1 of the present invention, where a represents different amounts of materials, b represents different pH values, c represents different ionic strengths, d represents different loading flow rates, and e represents different loading volumes. Figure 7This is a graph showing the effect of the type and volume of the desorption solvent on the extraction efficiency in Example 1 of the present invention, where a represents the type of desorption solvent and b represents the volume of the desorption solvent; Figure 8 The diagram shows the stability performance of i-CMP as a solid-phase extraction adsorbent in Example 1 of the present invention, where a is the repeatability performance diagram of the same solid-phase extraction column and b is the repeatability performance diagram between SPE batches. Figure 9 The images show the blank and spiked chromatograms of seven triazine herbicides at different concentrations in groundwater in Example 1 of this invention. Detailed Implementation

[0031] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components whose manufacturers are not specified are all commercially available conventional products.

[0032] Example 1 1.1 Preparation of Ionic Conjugated Microporous Polymers The ionic conjugated microporous polymer (i-CMP) was prepared via a Sonogashira-Hagihara cross-coupling reaction, and the specific steps are as follows: First, 274.6 mg of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (0.72 mmol), 440.6 mg of 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromide (0.96 mmol), 20.9 mg of cuprous iodide (0.11 mmol), and 69.3 mg of tetra(triphenylphosphine)palladium (0.06 mmol) were weighed and added to a 100 mL three-necked flask under an argon atmosphere. Then, a mixed solution of 20 mL of N,N-dimethylformamide and 20 mL of triethylamine was added, followed by a vacuum-argon purging process. Finally, under argon protection, the reaction system was heated in a constant-temperature oil bath at 100 °C for 72 h, during which a brownish-red mixture gradually formed.

[0033] After the reaction was complete, the mixture was cooled to room temperature, and the resulting material required further purification: it was washed three times each with 30 mL of N,N-dimethylformamide, tetrahydrofuran, methanol, and acetone to remove unreacted monomers and catalyst; then the material was immersed in 100 mL of saturated sodium bromide solution and magnetically stirred for 24 h to fully exchange the undisplaced Br₂. -After washing with water and methanol multiple times, the material was extracted with methanol and tetrahydrofuran for 48 h. Finally, the obtained material was dried in a vacuum drying oven at 60 °C for 12 h. After thorough drying, brown i-CMP material (labeled as i-CMP) was obtained.

[0034] 1.2 Liquid Chromatography-Tandem Mass Spectrometry Conditions Instrument model: Liquid Chromatography Triple quadrupole mass spectrometer (6470 LC / TQ, Agilent Technologies, USA). LC column conditions: Agilent EclipsePlus C18 column (1.8 μm, 150 mm × 2.1 mm); mobile phase: phase A was acetonitrile, phase B was 0.1% formic acid in water; gradient elution conditions: 0–6.0 min, 25% A; 6.0–6.1 min, 75–25% A; and 6.1–9.0 min, 25% A; flow rate: 0.3 mL / min. -1 Column temperature: 30℃. Injection volume: 2 μL.

[0035] Mass spectrometry parameters: Electrospray ionization (ESI) source was used for quantification in selected multiple reaction monitoring (MRM) mode; drying gas temperature: 250℃, dryer flow rate: 5 L·min -1 Atomizer voltage: 30 psi, capillary voltage: 3500 V, sheath flow rate: 11 L·min -1 Sheath gas temperature: 200℃. Optimized MRM parameters, including qualitative ions, quantitative ions, their fragmentation voltages, collision energies, and retention times, are listed in Table 1.

[0036] Table 1 shows the MRM parameters of seven triazine herbicides.

[0037] * For quantitative ions 1.3 Sample Pretreatment Wastewater, groundwater, peach juice, and grape juice were selected as actual samples for analysis. Wastewater was collected from factories surrounding Jinan City, Shandong Province; groundwater was collected from within Jinan City; and peach and grape juice were purchased from local supermarkets in Jinan. All four samples were filtered through a 0.45 μm pore size aqueous filter membrane, and the pH was adjusted to 6 with dilute hydrochloric acid and dilute sodium hydroxide. The samples were then stored in clean brown glass bottles at 4°C for subsequent solid-phase extraction experiments.

[0038] 1.4 Solid-phase extraction process Accurately weigh 15 mg of uniformly ground i-CMP material and pack it into a self-made solid-phase extraction (SPE) column. Activate the SPE column sequentially with 6 mL of acetonitrile and 6 mL of ultrapure water at a flow rate of 0.5 mL / min. Accurately transfer 100 mL of water sample, connect one end of a PTFE pipette to the inlet of the SPE column, and immerse the other end in the sample solution. Connect the entire apparatus to a vacuum pump, and drive the 100 mL water sample onto the column at a uniform flow rate using negative pressure. After sample loading, rinse the SPE column with 6 mL of ultrapure water to remove matrix impurities, and then dry the residual water inside the column for 1 min under maximum negative pressure. Triazine herbicides enriched on the column were eluted with 8 mL of acetonitrile for 20 min. After the eluent was purged and dried with nitrogen, 1 mL of methanol was added, and the mixture was sonicated and vortexed for 1 min. The eluent was then filtered through a 0.22 μm organic phase filter membrane, and the filtrate was collected into a 2 mL autosampler vial. The triazine herbicides were then quantitatively analyzed by LC-MS / MS.

[0039] 2 Results and Discussion 2.1 Characterization of Ionic Conjugated Microporous Polymers The surface morphology and microstructure of the i-CMP material were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the results are as follows: Figure 1 As shown. By Figure 1 As can be seen in a, the i-CMP nanoparticles exhibit a slightly aggregated spherical morphology, and the polymer shows a compact cluster structure with a rough surface and uneven particle size distribution, indicating that the cluster is formed by the aggregation of a large number of i-CMP nanoparticles. Figure 1 b further confirms that the i-CMP nanoparticles remain in a spherical aggregate state, consistent with the morphological characteristics reported in the literature. Simultaneously, energy-dispersive X-ray spectroscopy (EDS) further confirms this. Figure 1 c) The elemental composition and distribution of i-CMP were analyzed, confirming that the material contains three elements: C, N, and Br, with mass fractions of 61.82%, 18.33%, and 4.49%, respectively.

[0040] To further verify the successful synthesis of i-CMP materials, experiments were conducted at 4000-500 cm⁻¹. -1 Fourier transform infrared (FT-IR) spectra of i-CMP and two monomers, 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (TEPT) and 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromium bromide (BIBM), were measured in the wavenumber range. The results are as follows: Figure 2 As shown. By Figure 2 It can be seen that TEPT monomers are at 3290 cm⁻¹ -1 The absorption peak at that location belongs to The stretching vibration of C≡CH, the BIBM monomer at 653 cm⁻¹-1 The absorption peak at that point corresponds to C The stretching vibration of Br; however, in the FT-IR spectrum of i-CMP, both of the above characteristic absorption peaks completely disappear, and at 2202 cm⁻¹ -1 A new absorption peak appears at this point, and this peak belongs to C≡C The stretching vibrations indicate that the expected polymerization reaction occurred between the monomers. Furthermore, 1509 cm⁻¹ -1 and 1360 cm -1 The absorption peaks at these locations correspond to C=N and C=C in the triazine ring, respectively. The characteristic peaks of the stretching vibrations of N further confirmed the presence of the target functional group in the polymer molecular structure. The significant changes in the aforementioned infrared spectral characteristic peaks clearly confirmed the formation of the target polymer structure, indicating that the i-CMP material has been successfully synthesized.

[0041] The crystal phase and structure of i-CMP were analyzed using X-ray diffraction (XRD), and the results are as follows: Figure 3 As shown in Figure a, i-CMP exhibits a broad, diffuse diffraction peak at 20°, which may be related to the weak interaction stacking of aromatic rings in the interlayer of the i-CMP material; no obvious crystalline diffraction peaks were observed at other locations, indicating that the material possesses the typical amorphous structure of conjugated microporous polymers. Simultaneously, X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical composition and electronic structure of the i-CMP material surface. Figure 3 As shown in b, the XPS full spectrum of i-CMP shows four characteristic peaks at 68, 282, 396, and 530 eV, corresponding to Br3d, C1s, N1s, and O1s, respectively, confirming the presence of Br, C, N, and O elements in the material. Due to surface inhomogeneity, the contents of bromine and nitrogen are relatively low; the presence of oxygen originates from the adsorption of oxygen or water vapor from the air by the i-CMP material. Further analysis of the N1s XPS high-resolution spectrum... Figure 3 The characteristic peak at 396.3 eV corresponds to the CN single bond in the imidazole group, and the characteristic peak at 397.7 eV corresponds to the C=N double bond on the triazine ring. The above results confirm that the i-CMP material has been successfully polymerized.

[0042] To further investigate the physicochemical properties of the material, the thermal stability of i-CMP was characterized by thermogravimetric analysis curves. Figure 4 The figure shows the thermogravimetric curves of the material under N2 atmosphere, with a temperature range of 30℃-800℃ and a heating rate of 10℃·min. -1 .exist Figure 4The results show that the material loses 3.71% of its thermal stability in the 30-200℃ range due to the evaporation of water and solvents within the material structure; 10.26% in the 200-400℃ range due to unreacted organic monomers within the polymer structure; and 23.55% in the 400-800℃ range due to polymer decomposition. Therefore, i-CMP maintains a certain level of thermal stability at 400℃, exhibiting good heat resistance, meeting experimental requirements, and is beneficial for further practical applications.

[0043] To further analyze the specific surface area and pore size distribution characteristics of the i-CMP material, nitrogen adsorption-desorption isotherm tests were performed at 77.3 K. The results are as follows: Figure 5 As shown in the figure. Based on the adsorption-desorption curves, the specific surface area of ​​i-CMP is calculated to be 222.8 m². 2 ·g -1 Figure 5a shows the N2 adsorption-desorption isotherm of i-CMP. This isotherm exhibits typical characteristics of a Type I isotherm, confirming that the material is a typical microporous (<2 nm) material. Simultaneously, a clear hysteresis loop exists between the adsorption and desorption curves, indicating the presence of a certain amount of mesoporous (2-5 nm) structures in the polymer. Further calculations of the pore size distribution were performed using nonlocal functional theory (NLDFT), and the results are shown in Figure 5b: the sharp characteristic peaks at 0.73 nm, 1.48 nm, and 1.85 nm indicate that the material is predominantly microporous, while the weak peak at 2.73 nm confirms the presence of a small amount of mesoporous material. This rich pore structure of micropores and mesopores in the i-CMP material not only provides ample adsorption sites for subsequent solid-phase extraction but also helps enhance the interaction between the material and triazine herbicide molecules.

[0044] 2.2 Optimization of the solid-phase extraction process To achieve higher extraction efficiency, this experiment optimized several key experimental parameters, including adsorption conditions (material amount, sample solution pH, ionic strength, loading flow rate, and loading volume) and desorption conditions (eluent type and volume). 2.2.1 Optimization of Adsorption Conditions Material dosage is one of the core factors affecting the efficiency of solid-phase extraction. This experiment investigated the effect of different material dosages (5, 15, 30, 40, 50 mg) in the solid-phase extraction column on the extraction recovery rate of seven triazine herbicides. The results are as follows: Figure 6As shown in a, when the material dosage was 5 mg, the recovery rates of the seven herbicides were low because the material dosage was insufficient to completely adsorb the target substances in the sample solution. When the material dosage increased from 15 mg to 50 mg, there was no significant difference in the recovery rate, indicating that 15 mg of material was sufficient to adsorb the target substances in the sample. Therefore, 15 mg was selected as the material dosage for the solid-phase extraction column in subsequent experiments.

[0045] The pH value of the sample solution is a key factor in regulating the speciation of the target compound and directly affects the interaction between the adsorbent and the target analyte. To screen for the optimal sample solution pH, this experiment systematically investigated the effects of different sample solution pH conditions (2, 4, 6, 8, 10) on the recovery rate of triazine herbicides. Figure 6 The experimental results in section b show that the optimal recovery rates for all seven target compounds were achieved when the sample solution pH=6. Combined with the physicochemical property analysis of the target compounds: the pKa values ​​of this type of herbicide range from 2.28 to 4.31; when pH<4, the H+ in the solution... + At higher concentrations, some target molecules undergo protonation, forming positively charged ions, which is detrimental to the formation of π-π interactions. While at pH > 6, although the target molecules remain predominantly neutral, the increasing alkalinity of the solution may lead to deprotonation of acidic groups on the adsorbent surface, or the increased solvation effect may reduce the accessibility of π-π interaction sites, thereby weakening the conjugated interaction strength between i-CMP and the target molecules. Based on the above experimental results and mechanistic analysis, subsequent experiments determined the optimal pH for the sample solution to be 6.

[0046] To investigate the effect of ionic strength on the extraction efficiency of triazine herbicides, this experiment prepared NaCl solutions with concentrations of 0, 0.1, 0.2, 0.4, and 0.8 mol·L⁻¹. -1 A series of sample solutions. Results are as follows. Figure 6 As shown in Figure c, the extraction recovery rate of triazine herbicides did not change significantly with increasing ionic strength, indicating that ionic strength had no significant impact on the efficiency of the extraction system. Therefore, subsequent experiments used sample solutions without added NaCl to simplify the operation.

[0047] The loading flow rate directly affects the interaction time between the target compound and the solid-phase extraction adsorbent, thus affecting the extraction efficiency. This experiment investigated loading rates of 1, 2, 3, 4, and 5 mL / min. -1 The effect of five different loading flow rates on extraction efficiency is shown in Figure 6d. When the flow rate is between 1-2 mL / min... -1Within the specified flow rate range, the recoveries of all seven herbicides exceeded 90%, and there was no significant difference in recoveries at different flow rates, indicating that this flow rate range could guarantee optimal extraction efficiency. As the flow rate further increased, the recovery rate showed a slight decreasing trend. This is because excessively fast flow rates shorten the interaction time between the target compound and i-CMP, which is not conducive to the sufficient adsorption of the target compound by the adsorbent. Considering both extraction efficiency and experimental efficiency, subsequent experiments determined a flow rate of 2 mL / min. -1 As the optimal loading flow rate.

[0048] In addition, this experiment also investigated the effect of different loading volumes (100, 200, 300, 400, 500 mL) on extraction efficiency, and the results are as follows: Figure 6 As shown in Figure e, when the sample loading volume increased from 100 mL to 500 mL, the extraction recoveries of the seven triazine herbicides did not change significantly. This result indicates that even at a sample loading volume of 500 mL, i-CMP can maintain high extraction efficiency, fully demonstrating its excellent and efficient enrichment performance for triazine herbicides. Based on these advantages, subsequent experiments determined 500 mL to be the optimal sample loading volume.

[0049] 2.2.2 Optimization of Desorption Conditions To achieve efficient desorption of the target analytes, this experiment investigated the effects of five organic solvents—acetonitrile, acetone, ethyl acetate, dichloromethane, and n-hexane—on the extraction recovery rate of triazine herbicides. As shown in Figure 7a, acetonitrile exhibited the best desorption efficiency for all seven triazine herbicides compared to the other four solvents, enabling more complete desorption and release of the target analytes. Therefore, acetonitrile was selected as the preferred desorption solvent for subsequent experiments.

[0050] In addition, this experiment investigated the effect of different acetonitrile volumes (2, 4, 6, 8, and 10 mL) on desorption efficiency. The results are shown in Figure 7b. When the acetonitrile volume was only 2 mL, the triazine herbicides adsorbed on the solid-phase extraction column could not be completely eluted due to insufficient volume. As the acetonitrile volume increased, the recovery rate of the target analytes gradually increased. When the acetonitrile volume increased to 8 mL, the recovery rates of the seven triazine herbicides reached 90.1%–98.5%, and the desorption efficiency tended to stabilize. Further increasing the acetonitrile volume did not result in a significant increase in recovery rate. Therefore, subsequent experiments determined that 8 mL was the optimal desorption volume for acetonitrile.

[0051] 2.3 Material Stability Study To evaluate the stability of i-CMP as a solid-phase extraction adsorbent, this experiment investigated both intra-batch reusability and inter-batch reproducibility. First, the reusability of the SPE column was examined: a single SPE column was used for solid-phase extraction cycle experiments. After each use, it was regenerated by washing with 6 mL of acetonitrile and 6 mL of purified water sequentially before being used in the next cycle. Figure 8 As can be seen from 'a', after 10 repeated uses, the extraction recovery rate of the seven triazine herbicides remained at a high level, indicating that it has excellent intra-batch reusability stability.

[0052] Furthermore, batch-to-batch reproducibility of solid-phase extraction (SPE) columns is a key factor in ensuring the reliability of experimental results. This experiment used different batches of i-CMP material to prepare SPE columns and systematically evaluated their batch-to-batch performance consistency. As shown in Figure 8b, the five batches of self-made SPE columns showed no significant difference in extraction efficiency for the target analyte, exhibiting good batch-to-batch repeatability. In summary, the i-CMP solid-phase extraction columns prepared in this experiment demonstrate excellent performance in both intra-batch reusability and batch-to-batch performance reproducibility, possessing stable potential for practical application.

[0053] 2.4 Method Validation This study applied the established i-CMP-based SPE-HPLC-MS / MS method to the trace analysis of seven triazine herbicides in groundwater, wastewater, peach juice, and grape juice matrices, and systematically investigated the comprehensive analytical performance of the method. The core evaluation parameters, including linear range, limit of detection (LOD), limit of quantitation (LOQ), and repeatability, are summarized in Table 2. The results showed that the trace amounts of the seven target analytes were within the range of 0.25–250 ng·L⁻¹. - ¹ It exhibits a good linear response within the concentration range, with a correlation coefficient (R²) 2 The LOD and LOQ of the method are as low as 0.03 to 0.11 ng·L⁻¹, ranging from 0.9929 to 0.9991. - ¹ and 0.10~0.37 ng·L - ¹ This demonstrates excellent detection sensitivity. Repeatability experiments show that the intra-day relative standard deviation (RSD) of five parallel analyses of the same sample within the same working day is less than 9.9%; the inter-day RSD over five consecutive working days is less than 10.8%. These data confirm that this method possesses both good precision and stability, and can fully meet the requirements for accurate quantitative analysis of trace triazine herbicides in complex matrices.

[0054] Table 2 lists the method parameters for seven triazine herbicides.

[0055] 2.5 Method Comparison This study systematically compared the established extraction method for triazine herbicides in environmental water samples and fruit juices with previously reported extraction methods for similar herbicides in food and water samples. The relevant results are summarized in Table 3. A comprehensive analysis of key indicators such as adsorbent type and dosage, sample volume, method detection limit, and enrichment factor reveals that this method possesses multiple advantages, including low adsorbent dosage, low detection limit, and suitability for large-volume sample analysis. In conclusion, i-CMP has broad practical application potential in the enrichment detection of triazine herbicides.

[0056] Table 3 Comparison of Methods

[0057] 2.6 Analysis of actual samples Using the method established in this study, residues of seven triazine herbicides were detected in four types of actual samples: groundwater, wastewater, peach juice, and grape juice. The results showed that none of the target analytes were detected in any of the tested samples.

[0058] In addition, to verify the accuracy and reliability of the method, actual samples of the above four different matrices were tested at three concentration levels (1 ng·L⁻¹). -1 10 ng·L -1 100 ng·L -1 Spiked recovery experiments were conducted. As shown in Table 4, the spiked recoveries of groundwater, wastewater, peach juice, and grape juice samples ranged from 77.4% to 109.1%, 85.1% to 108.6%, 82.8% to 102.5%, and 81.6% to 110.7%, respectively, with RSDs ranging from 0.1% to 12.2%.

[0059] Figure 9 The figure shows a chromatographic comparison of the blank and spiked groundwater samples. As can be seen from the figure, this method can effectively eliminate the interference of the matrix on the chromatographic analysis. The retention times of the seven triazine herbicides are stable and the separation is good, further verifying the reliability and accuracy of this analytical method in practical detection applications.

[0060] 2.7 Selective Experiments To investigate the selectivity of the method, this study conducted solid-phase extraction experiments on a mixture of triazine herbicides and polycyclic aromatic hydrocarbons (PAHs). The results are shown in Table 5. The experimental data show that the extraction recoveries of triazine herbicides remained at a high level, ranging from 88.51% to 95.69%; while the extraction recoveries of PAHs were relatively low, ranging from only 35.74% to 83.16%. This result fully confirms that i-CMP has an excellent enrichment advantage for triazine herbicides during solid-phase extraction. This phenomenon is presumably due to the strong π-π interaction between the triazine ring contained in i-CMP and the six-membered triazine heterocycle in the triazine herbicide molecule.

[0061] Table 4 Analysis of actual samples

[0062] Recoveries of spiked triazine herbicide at 1, 10, 100 ng·L -1 (a, b, c). ND: not detected. Table 5 Selectivity Experiment Targets and Recovery Rates

[0063] In summary, to achieve accurate quantification of triazine herbicides in food and environmental samples, this study successfully synthesized a novel ionic conjugated microporous polymer (i-CMP) with both imidazole ionic groups and a triazine conjugated skeleton using 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine and 1,3-bis(4-bromophenyl)-1H-imidazolium-3-bromium as monomers via a Sonogashira-Hagihara coupling reaction. This i-CMP was then used for the first time as a solid-phase extraction (SPE) adsorbent for the enrichment and analysis of seven triazine herbicides in environmental water samples and fruit juices. Under optimized experimental conditions, the established analytical method achieved rapid and efficient enrichment and detection of the target analytes, demonstrating excellent sensitivity, accuracy, and resistance to matrix interference. This study not only provides a stable and reliable technical solution for the accurate analysis of trace triazine herbicides but also offers new research ideas and practical references for the application of i-CMPs in the efficient adsorption and detection of organic pollutants in complex matrices.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An ionic conjugated microporous polymer, characterized in that, has the following structure repeating unit: 。 2. The ionic conjugated microporous polymer of claim 1, wherein, The ionic conjugated microporous polymer is prepared by cross-coupling of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine and 1,3-bis(4-bromophenyl)-1H-imidazole-3-bromonium.

3. The ionic conjugated microporous polymer according to claim 2, wherein, The molar ratio of the 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine and 1,3-bis(4-bromophenyl)-1H-imidazole-3-bromonium is (0.7-0.75):(0.9-1.0).

4. A method of preparing the ionic conjugated microporous polymer according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 1,3-bis(4-bromophenyl)-1H-imidazole-3-bromonium, cuprous iodide and tetrakis(triphenylphosphine)palladium are mixed under an inert atmosphere, and after gas replacement with a solvent, heating reaction is carried out; after the reaction is completed, cooling to room temperature, and purification to obtain the product.

5. The method of claim 4, wherein the ionotropic conjugated microporous polymer is prepared by the reaction of a compound of formula (I) with a compound of formula (II) in the presence of a base. The mixing molar ratio of the 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 1,3-bis(4-bromophenyl)-1H-imidazole-3-bromonium, cuprous iodide and tetrakis(triphenylphosphine)palladium is (0.7-0.75):(0.9-1.0):(0.1-0.15):(0.05-0.08); The solvent is a mixture of N,N-dimethylformamide and triethylamine, and the mixed volume ratio of N,N-dimethylformamide and triethylamine is 1:(1-2).

6. The method of claim 4, wherein the ionotropic conjugated microporous polymer is prepared by the reaction of a compound of formula (I) with a compound of formula (II) in the presence of a base. The temperature of the heating reaction is 90-110℃, and the time is 70-80 h; The purification is carried out by sequentially washing with N,N-dimethylformamide, tetrahydrofuran, methanol and acetone for 2-5 times, then soaking in a saturated sodium bromide solution and stirring, and then washing with water and methanol for multiple times, followed by Soxhlet extraction with methanol and tetrahydrofuran, and finally vacuum drying.

7. Use of the ionic conjugated microporous polymer according to any one of claims 1-3 in pretreatment and analysis of triazine herbicides.

8. A method for analyzing triazine herbicides, characterized by, The method comprises the following steps: The ionic conjugated microporous polymer according to any one of claims 1-3 is used as a solid-phase extraction agent, and is added to a sample to be tested to extract and enrich triazine herbicides, a desorption solvent is added for elution, the eluate is collected and blown dry with nitrogen to obtain a residue, which is redissolved and filtered, and then subjected to quantitative analysis by liquid chromatography-tandem mass spectrometry.

9. The method of analyzing triazine herbicides according to claim 8, wherein, The triazine herbicide is one or more of atraton, diquat, ametryn, prometon, prometryn, terbucarb and dimexano; The pH of the sample to be tested is 4-6; 5-35 L of sample to be tested is added per gram of adsorbent; the addition rate of the sample to be tested is 1-2 mL·min -1 ; the desorption solvent is one of acetonitrile, acetone, ethyl acetate, dichloromethane and n-hexane; the volume ratio of desorption solvent to sample to be tested is (2-10):500; the elution time is 15-20 min.

10. The analysis method of the triazine herbicide according to claim 8, wherein, The conditions of liquid chromatography are as follows: an Agilent Eclipse Plus C18 column is used, the mobile phase includes mobile phase A and mobile phase B, the mobile phase A is acetonitrile, the mobile phase B is formic acid water, a gradient elution procedure is used, that is, 0-6.0 min, 25% mobile phase A; 6.0-6.1 min, 75%-25% mobile phase A and 6.1-9.0 min, 25% mobile phase A; the flow rate is 0.2-0.4 mL·min -1 , the column temperature is 25-30 DEG C, and the injection amount is 1-3 mu L; The mass spectrometry conditions are using the selected multiple reaction monitoring mode for quantification; the temperature of the dryer is 220-270°C, the flow rate of the dryer is 3-6 L·min -1 , the atomizer voltage is 25-30 psi, the capillary voltage is 3000-4000 V, and the sheath gas flow rate is 10-12 L·min -1 , and the sheath gas temperature is 180-220°C.

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