A method for determining a pesticide in a water sample

Abstract

The application belongs to the field of pesticide residue detection, and particularly relates to a method for determining pesticides in water samples. The method comprises the following steps: amino modification is performed on MIL-100(Fe) to obtain an amino-functionalized MIL-100(Fe) material; and the pesticides in the water sample are analyzed and detected by using SALDI-TOF-MS with the amino-functionalized MIL-100(Fe) material as a substrate. The application forms a special MOF material by performing amino functionalization modification on MIL-100(Fe), which can enhance the interaction force between the substrate and the analyte, exhibits good ultraviolet absorption and energy transfer capacity, and thus improves the desorption / ionization efficiency in LDI detection. The method is used to detect pesticide residues, and in the low mass region, lower background noise and higher signal intensity are exhibited, so that the detection of pesticide substances in the small molecule region is greatly broken through, and the detection limit is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of pesticide residue detection, specifically relating to a method for determining pesticides in water samples. Background Technology

[0002] Pesticides play a crucial role in agricultural production by controlling pests and weeds and regulating plant growth. However, due to their toxicity and non-degradability, widespread use and improper disposal lead to pesticide residues in agricultural products, soil, and environmental water. Through the food chain, pesticides accumulate in plants and animals and eventually enter the human body, threatening human safety. Therefore, monitoring pesticide residues in food and the environment is extremely important. Currently, widely used pesticide analysis methods include gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC), immunoassay, and biosensor methods, but all suffer from insufficient stability and accuracy, and cannot achieve high-throughput detection. Therefore, there is an urgent need for a rapid, accurate, and high-throughput method to determine pesticides.

[0003] Matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF-MS) offers advantages such as speed, high throughput, high sensitivity, good salt tolerance, and small sample volume requirements, making it widely used for the analysis and detection of biomolecules such as proteins, peptides, nucleic acids, and polymers. In MALDI-TOF-MS detection, the matrix plays a crucial role in efficiently transferring laser energy, accelerating sample ionization, improving sample crystallization, and calibrating internal standards. However, common MALDI matrices (such as α-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB)) exhibit severe correlation peak interference in the low-mass region (<500 DA), and the problem of uneven matrix / analyte co-crystallization leads to poor reproducibility and unreliable quantification. Furthermore, pesticide signals in MALDI are also located in the low-mass region; therefore, these organic matrices are unsuitable for pesticide detection. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining pesticides in water samples, which solves the problems of existing methods for analyzing small molecule substances such as pesticides, including numerous matrix interference peaks, poor reproducibility, and low sensitivity.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for determining pesticides in water samples includes the following steps: amino-modifying MIL-100(Fe) to obtain amino-functionalized MIL-100(Fe) material; using the amino-functionalized MIL-100(Fe) material as a matrix, analyzing and detecting pesticides in the water sample using SALDI-TOF-MS.

[0007] This invention is pioneering. By amino-functionalizing MIL-100(Fe) to form a special MOF material, it enhances the interaction between the matrix and the analyte, exhibiting excellent UV absorption and energy transfer capabilities, thereby improving the desorption / ionization efficiency in LDI detection. Using this method to detect pesticide residues, it demonstrates low background noise and high signal intensity in the low-mass region, representing a significant breakthrough in the detection of pesticides in small molecule regions and greatly reducing the detection limit.

[0008] Preferably, the testing conditions of the SALDI-TOF-MS are as follows: the acquisition mode is positive ion mode, the molecular weight scan range is 100-600 Da, the laser frequency is 1000 Hz, and the scan frequency is 400.

[0009] Preferably, the pesticide includes one or more of the following: azoxystrobin, chlorantraniliprole, indoxacarb, triazophos, benzyl sulfoxide, benzalkonium chloride, chlorpyrifos sulfone, piperonyl butyl ether, phosmet, dimethoate, phorate, 3-hydroxycarbofuran, sulfoxide, oxadixyl, ethionyl sulfoxide, and benzyl sulfoxide.

[0010] Preferably, the amino-functionalized MIL-100(Fe) material is obtained by mixing and reacting MIL-100(Fe) and 3-amino-4,5-dihydroxybenzoic acid in water, with a mass ratio of MIL-100(Fe) to 3-amino-4,5-dihydroxybenzoic acid of 80:30. Using 3-amino-4,5-dihydroxybenzoic acid as a ligand to modify MIL-100(Fe with amino groups enhances the interaction between the matrix and the analyte. Because the lone electrons of the nitrogen atom in the aromatic amine form conjugated π molecular orbitals with the benzene ring, electronic transitions occur, causing it to absorb most wavelengths related to ultraviolet light, thus improving the desorption / ionization efficiency in LDI detection.

[0011] More preferably, the mixing reaction is carried out by stirring at room temperature for 1 to 2 hours.

[0012] Preferably, during the analysis and detection, the amino-functionalized MIL-100(Fe) material is prepared into a matrix solution, spotted onto a matching target plate, dried, and then dropped into the water sample to be tested. After the solvent evaporates and crystallizes, SALDI-TOF-MS testing is performed.

[0013] More preferably, the concentration of amino-functionalized MIL-100(Fe) material in the matrix solution is 1 mg / mL, and the volume ratio of the matrix solution to the water sample is 1:1.

[0014] Preferably, the water sample is environmental water or an extract of agricultural products, and the extraction solvent used for the extract is water or a mixture of water and organic solvents.

[0015] More preferably, the agricultural product is tobacco leaves, and the extraction solvent is a methanol-water solution with a volume ratio of 60-80%. Attached Figure Description

[0016] Figure 1 The FTIR spectra of MIL-100(Fe) and MIL-100(Fe)-NH2 in Example 1 of this invention;

[0017] Figure 2 XPS and high-resolution XPS spectra of MIL-100(Fe) and MIL-100(Fe)-NH2 in Example 1 of this invention;

[0018] Figure 3 MIL-100(Fe) in Example 1 of this invention Figure 3 a) and MIL-100(Fe)-NH2( Figure 3 b) SEM image;

[0019] Figure 4 The XRD patterns of MIL-100(Fe) and MIL-100(Fe)-NH2 in Example 1 of this invention are shown below.

[0020] Figure 5 The TAG diagrams of MIL-100(Fe) and MIL-100(Fe)-NH2 in Example 1 of this invention are shown below.

[0021] Figure 6 The nitrogen adsorption-desorption curves and pore size distribution diagrams of MIL-100(Fe) and MIL-100(Fe)-NH2 in Example 1 of this invention are shown.

[0022] Figure 7 The UV bandgap spectra of MIL-100(Fe) and MIL-100(Fe)-NH2 in Example 1 of this invention;

[0023] Figure 8 The images shown are SALDI-TOF-MS images of pesticides detected by CHCA, DHB, and MIL-100(Fe)-NH2 as matrices in Experimental Example 4 of this invention.

[0024] Figure 9 This is a comparison of mass spectrum peak intensities for MIL-100(Fe) and MIL-100(Fe)-NH2 as matrices in Experimental Example 4 of this invention;

[0025] Figure 10The image shows the SALDI-TOF-MS chromatograms of six pesticides at a concentration of 1 mg / mL detected by MIL-100(Fe)-NH2 in Experiment Example 4 of this invention.

[0026] Figure 11 This is a molecular docking binding energy diagram of MIL-100(Fe)-NH2 and six pesticide molecules in Experimental Example 7 of this invention. Detailed Implementation

[0027] Given the severe correlation peak interference of organic matrices in the low-mass region (<500 DA) and the poor reproducibility and inability to achieve reliable quantification due to inhomogeneous matrix / analyte co-crystallization, various types of nanomaterials (including silicon-based nanomaterials, carbon-based nanomaterials, metal-organic frameworks (MOFs), and covalent organic frameworks) have been developed as matrices for MALDI analysis of small molecule compounds. This type of desorption ionization is called surface-assisted laser desorption / ionization time-of-flight mass spectrometry (SALDI-TOF-MS). Among them, MOFs are porous nanomaterials composed of metal ions or metal clusters and organic ligands through coordination bonds. They are widely used due to their advantages such as high specific surface area, high porosity, uniform crystal structure, and ease of functionalization. The affinity between metal ions and analytes can promote the ionization of the target analyte. Some MOF materials have excellent absorption performance in the ultraviolet-visible range, meeting the requirements for LDI matrices.

[0028] The technical concept of this invention is to modify MIL-100(Fe) with amino groups to enhance the interaction between the matrix and the analyte, improve the matrix's UV absorption and energy transfer capabilities, thereby increasing the desorption / ionization efficiency of LDI detection. Furthermore, 3-amino-4,5-dihydroxybenzoic acid is selected as the amino-modifying ligand. Its aromatic amine structure can form conjugated π molecular orbitals with the benzene ring, resulting in electronic transitions and absorbing most wavelengths related to UV light, thus improving its performance in electron and energy transfer processes.

[0029] Using the above-mentioned amino-functionalized MIL-100(Fe) material for SALDI-TOF-MS testing, it exhibited low background noise and detection limit in the low-quality region, as well as high signal intensity. It can achieve rapid, high-throughput, and accurate detection of pesticides such as azoxystrobin, chlorantraniliprole, indoxacarb, triazophos, benzyl sulfoxide, benzo[a]pyrethrum, triphenyl phosphate, phosmet, piperonyl butyl ether, phosmet, dimethoate, phorate, 3-hydroxycarbofuran, sulfoxide, oxadixyl, ethionyl sulfoxide, and benzyl sulfoxide.

[0030] The implementation process of the present invention will be described in detail below with reference to specific embodiments. In the following embodiments, deionized water, methanol, and acetone were all HPLC grade and purchased from Shanghai MACKLIN; MIL-100 (Fe) was purchased from Beijing Bailingwei Technology Co., Ltd.; α-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) were purchased from Sigma Aldrich. The matrix-assisted laser desorption / ionization time-of-flight mass spectrometer was a 5800MALDI-TOF / TOF. TM (AB SCIEX, USA).

[0031] I. Specific Embodiments of the Method for Determining Pesticides in Water Samples of the Present Invention

[0032] Example 1

[0033] The method for determining pesticides in water samples in this embodiment mainly includes the synthesis of amino-functionalized MIL-100(Fe) material and SALDI-TOF-MS analysis using amino-functionalized MIL-100(Fe) material as a matrix.

[0034] 1. Synthesis of amino-functionalized MIL-100(Fe) materials

[0035] 80 mg of MIL-100(Fe) was added to 20 mL of deionized water and stirred for 10 min to form a homogeneous suspension. 30 mg of 3-amino-4,5-dihydroxybenzoic acid was added as a ligand to the suspension, and the mixture was stirred at room temperature for 1 h. After the reaction, solid-liquid separation was performed to obtain a precipitate. The precipitate was washed three times with deionized water and methanol, respectively. The washed precipitate was then dried overnight in a vacuum oven at 60 °C to obtain a light brown powder, namely MIL-100(Fe)-NH2.

[0036] 2. SALDI-TOF-MS Analysis and Testing

[0037] Dissolve MIL-100(Fe)-NH2 powder at a ratio of 1 mg / mL in a mixed solvent of ethanol and water at a volume ratio of 4:1, and sonicate for 15 min to completely dissolve it, thus completing the preparation of the matrix solution.

[0038] Place 20 mg of lyophilized tobacco powder in a 2 mL centrifuge tube, add 1 mL of 80% (v / v) methanol-water solution, add internal standard TPP (triphenyl phosphate) internal standard solution (solvent is 70% (v / v) acetone-water solution) to a concentration of 10 ng / mL, sonicate under ice bath conditions for half an hour, and then centrifuge at 4℃ and 14000 r / min for 10 min, and take the supernatant for sample loading.

[0039] 1 μL of matrix solution was spotted onto the matching target plate, dried at room temperature, and then 1 μL of supernatant was added. After the solvent evaporated and crystallized, SALDI-TOF-MS analysis was performed directly. Positive ion scanning mode was used during the test; the scanning range was 100-600 DA; equipped with an ND:YAG high peak power high pulse energy laser, providing 1000 Hz high frequency laser, and the MS spectrum was obtained by shooting signals at an average of 400 times per position.

[0040] Example 2

[0041] The method for determining pesticides in water samples in this embodiment is basically the same as that in Example 1, except that the water sample preparation process is as follows: 15 mL of environmental water sample is concentrated to complete dryness using a vacuum concentrator, and then 200 μL of 70% (v / v) acetone-water solution is added. Then, 2 μL of TPP (triphenyl phosphate) internal standard solution (solvent is 70% (v / v) acetone-water solution) with a concentration of 1 μg / mL is added to the above solution to obtain a test solution with an internal standard concentration of 10 ng / mL. Then, the solution is centrifuged at 14000 rpm for 10 min, and the supernatant is retained for SALDI-TOF-MS testing.

[0042] II. Experimental Examples

[0043] Experimental Example 1: Infrared and X-ray photoelectron spectroscopy analysis of MIL-100(Fe) and MIL-100(Fe)-NH2

[0044] Infrared spectroscopy and X-ray photoelectron spectroscopy were performed on MIL-100(Fe) in Example 1 and the prepared MIL-100(Fe)-NH2. The results are as follows: Figure 1 and Figure 2 As shown.

[0045] Figure 1 The FT-IR spectra of MIL-100(Fe) and MIL-100(Fe)-NH2 are shown below. Figure 1 As shown, 1622cm -1 The peaks at 1446 and 1382 cm⁻¹ are characteristic vibrations of the C=O bond. -1 The peaks at 1712 cm⁻¹ represent the symmetric and asymmetric vibrations of the -OCO- group, respectively. -1 A C=O vibration peak can be observed at 713 cm⁻¹. -1 The CH vibration is present. In addition to the characteristic peaks shared by these two MOFs, an additional peak at 1246 cm⁻¹ is observed in amino-modified MIL-100(Fe)-NH₂. -1 2590cm -1 and 3210cm -1The peaks are due to the stretching vibrations of the CN, CH, and NH bonds in the aromatic amine. This demonstrates that the ligands have been successfully loaded into the structure of MIL-100(Fe).

[0046] Figure 2 The XPS spectra of MIL-100(Fe) and MIL-100(Fe)-NH2 are shown. Compared with MIL-100(Fe), the amino-functionalized MOF material shows an N1s peak at 398 eV. In the high-resolution N1s spectrum, 396.8 eV and 398.9 eV correspond to NH2 and NC, respectively, indicating the presence of amino groups in the ligand-modified MIL-100(Fe)-NH2. The high-resolution C1s peak at 282 eV is divided into three parts: 271.4 eV, 272.8 eV, and 275.1 eV, corresponding to CC / CN, C=C, and OC=O in MIL-100(Fe)-NH2. The XPS experimental results confirm the successful modification of MIL-100(Fe).

[0047] Experimental Example 2: SEM and XRD Analysis of MIL-100(Fe) and MIL-100(Fe)-NH2

[0048] SEM and XRD analyses were performed on MIL-100(Fe) and MIL-100(Fe)-NH2 in Example 1, and the results were... Figure 3 and Figure 4 As shown.

[0049] Figure 3 MIL-100(Fe)( Figure 3 a) and MIL-100(Fe)-NH2( Figure 3 b) SEM image, by Figure 3 It can be seen that both MOFs exhibit irregular shapes and obvious aggregation, with particles interconnected to form a porous structure. Compared with MIL-100(Fe), the amino-modified MIL-100(Fe)-NH2 shows more adhesion between the layered structures.

[0050] The crystal structures of MIL-100(Fe) and MIL-100(Fe)-NH2 were verified by XRD analysis. Figure 4 The figures show the XRD patterns of two MOFs. As can be seen from the figures, the intensity of these characteristic peaks decreases after amino ligand modification.

[0051] Experimental Example 3: Thermal stability, specific surface area, pore size distribution, and UV-VIS analysis of MIL-100(Fe) and MIL-100(Fe)-NH2

[0052] Thermogravimetric analysis was performed on MIL-100(Fe) and MIL-100(Fe)-NH2 from Example 1 to test the thermodynamic stability of the materials. Figure 5 As shown, due to the release of water and solvent vapor from the MOF structure and the dehydration of bound water at 100℃, MIL-100(Fe) exhibits its first significant mass loss at 100℃. At 400℃, the MOF decomposes, leading to a sharp decrease in mass. Between 100 and 450℃, the weight loss of MIL-100(Fe)-NH2 occurs earlier than that of MIL-100(Fe), indicating that amino functionalization has a slight effect on the thermal stability of MIL-100(Fe).

[0053] The specific surface area and pore size distribution of the two MOF materials were determined using a 77K N2 adsorption-desorption isotherm, and the results are as follows: Figure 6 As shown, both MIL-100(Fe) and MIL-100(Fe)-NH2 exhibit typical type I adsorption isotherms. The specific surface area of ​​MIL-100(Fe)-NH2 decreases after ligand modification, indicating that the introduction of amino groups leads to the aggregation of MIL-100(Fe) and pore blockage.

[0054] MIL-100(Fe) and MIL-100(Fe)-NH2 were characterized by UV-Vis, and their UV absorption spectra (TAUC diagrams) are shown below. Figure 7 As shown, after ligand modification, the band gap of MIL-100(Fe) decreased from 2.06 eV to 1.51 eV. The lower band gap allows the MOF to absorb light over a wider wavelength range, indicating that the introduction of amino groups lowers the laser absorption threshold and improves the laser desorption / ionization (LDI) efficiency of the analyte.

[0055] Experiment Example 4: Comparison of SALDI-TOF-MS Analysis of Different Matrix

[0056] CHCA was dissolved in a 70% (v / v) acetonitrile-water solution at a concentration of 10 mg / mL to obtain the CHCA matrix. DHB was dissolved in a 50% (v / v) acetonitrile-water solution at a concentration of 10 mg / mL to obtain the DHB matrix. The performance of the CHCA matrix, DHB matrix, and MIL-100(Fe)-NH2 from Example 1 in pesticide detection by SALDI-TOF-MS was compared. The concentration of the pesticide standard solution (diluted with 70% (v / v) acetone-water solution) was 1 mg / mL. The results are as follows. Figure 8 As shown.

[0057] The above three matrices were used to detect the pesticide standards pyraclostrobin (AZ), triphenyl phosphate (TPP), and ethyl phosphonate sulfoxide (DS). TPP is typically used as an internal standard for pesticide detection. When CHCA ( Figure 8When a1, b1, and c1 are used as matrices, SALDI-TOF-MS mass spectrometry exhibits numerous matrix-related background noises that interfere with the detection of analytes, such as [M+H]. + [M+Na] + and [M+K] + Use DHB ( Figure 8 When a2, b2, c2) are used as the matrix, the background noise is less than that of CHCA, but the signal intensity is lower. This may be because the crystallization of DHB with the analyte is uneven, and it cannot effectively transfer laser energy to promote the LDI process. Meanwhile, MIL-100(Fe)-NH2( Figure 8 When a3, b3, and c3 are used as matrices, mass spectrometry peaks with low background interference and high signal intensity are obtained. Less matrix effect avoids the suppression of analyte ionization and signal intensity.

[0058] To verify the performance of amino-modified MOF materials, pesticide concentrations of 1 mg / mL were analyzed using MIL-100(Fe) and MIL-100(Fe)-NH2 under the same conditions. The results are as follows: Figure 9 As shown, Figure 9 a1-c1 are SALDI-TOF-MS mass spectra of the pesticides azoxystrobin (AZ), benzalkonium chloride (BX), and monocrotophos (MCP) detected using MIL-100 (Fe) as the matrix. Figure 9 a2-c2 are SALDI-TOF-MS mass spectra of the pesticides azoxystrobin (AZ), benzalkonium chloride (BX), and monocrotophos (MCP) using MIL-100(Fe)-NH2 as the matrix. Taking azoxystrobin (AZ) as an example, the SALDI-TOF-MS mass spectrum using MIL-100(Fe) as the matrix shows [AZ+Na]. + Signal strength is 1017, [AZ+K] + The signal strength is 1260. When using MIL-100(Fe)-NH2 as the matrix, [AZ+Na] + The signal strength increased to 72748, [AZ+K] + The value increased to 81411. This indicates that the modification with amino groups significantly improved the LDI process of MOFs, resulting in higher signal intensity.

[0059] To further investigate the feasibility of using amino-functionalized MIL-100(Fe)-NH2 to detect more pesticide compounds, we selected six pesticides for SALDI-TOF-MS testing in positive ion mode. Figure 10 As shown, Figure 10a1–10a6 are SALDI-TOF-MS mass spectra of the pesticides azoxystrobin (AZ), indoxacarb (INX), triazophos (TZP), omethoate (OMT), chlorpyrifos sulfone (FSO2), and piperonyl butyl ether (PBO) detected using MIL-100(Fe)-NH2 as the matrix. This method successfully detected all pesticide standards at a concentration of 1 mg / mL with high signal intensity and low background interference. [M+Na] + and [M+K] + The peaks all exhibited high signal intensity, providing a solid foundation for quantitative analysis of real samples using SALDI-TOF-MS.

[0060] To verify the analytical performance of amino-functionalized MIL-100(Fe)-NH2 based on SALDI-TOF-MS in pesticide detection, linearity (R0.05) of 16 pesticides was determined using MIL-100(Fe)-NH2 as the matrix. 2 The limits of detection (LOD) and quantitation (LOQ) were determined. 10 ng / mL TPP was added as an internal standard to each standard solution to achieve accurate pesticide quantification. Standard curves were plotted based on the ionic strength of each pesticide standard and the ionic strength of TPP, and the results are shown in Table 1.

[0061] Table 1. SALDI-TOF-MS detection results of 16 pesticides

[0062]

[0063] As shown in Table 1, the regression coefficients of all analytes were within the acceptable range of 0.90–0.99. The limits of quantitation and detection were 1.02–260.63 μg / L and 0.064–32.578 μg / L, respectively. The LOQs for 3-hydroxycarbofuran (HCF), ethionyl sulfoxide (DS), azoxystrobin (APE), and pyraclostrobin (AZ) reached 1.02 μg / L, and the signal-to-noise ratio (S / N) for all analytes was greater than or equal to 3. This demonstrates that the method for analyzing pesticides according to the present invention has high sensitivity and acceptable linearity.

[0064] Experimental Example 5: Detection Results of Pesticide Spikes in Tobacco Extract

[0065] A tobacco leaf-based supernatant was prepared as described in Example 1. Pesticide standards were added to the supernatant until the concentration of each standard reached 5 mg / L. The supernatant was then diluted twofold using tobacco extract to obtain test samples with analyte concentrations ranging from 5 mg / L to 0.0076 μg / L. The limits of detection for 16 pesticides in the tobacco extract were determined individually, and [M+K] were selected. + As a source of signal strength, the detection limits and signal-to-noise ratios of 16 pesticides in tobacco extract are shown in Table 2.

[0066] Table 2. SALDI-TOF-MS detection results of 16 pesticides in tobacco extract.

[0067]

[0068]

[0069] As shown in Table 2, the signal-to-noise ratios for all 16 pesticides were greater than or equal to 10. The limits of detection ranged from 0.076 μg / L to 1250 μg / L, indicating that this method has the potential to be effectively applied to the detection of pesticide residues in tobacco samples and other agricultural products.

[0070] Experimental Example 6: Detection of pesticide residues in environmental water samples

[0071] Since pesticides may be present in environmental water, it is crucial to develop an effective and rapid method for the sensitive detection of pesticides in actual water samples. We collected actual water samples from a certain region and selected the MIL-100(Fe)-NH2 matrix for quantitative analysis of pesticides. After pretreatment as described in Example 2, the water samples were detected by SALDI-TOF-MS (using the standard curve in Table 1). Components with excessively high concentrations were diluted before detection. The results are shown in Table 3.

[0072] Table 3. Environmental water sample test results

[0073] name Concentration (μg / L) RSD (%) Benzene sulfoxide 6.2 8.0％ β-phosphite 7.2 5.8％ Piperyl Butyl Ether 48.2 1.3％

[0074] Quantitative analysis of environmental water samples revealed three pesticide compounds, with RSDs ranging from 1.3% to 8.0% across three replicate determinations. The results demonstrate that this method possesses high accuracy and can effectively and rapidly determine pesticide residues in actual water samples with simple pretreatment.

[0075] Experimental Example 7: Binding Energy Analysis of MIL-100(Fe)-NH2 and 6 Pesticides

[0076] This experimental example uses density functional theory (DFT) to further explore the interaction between pesticide analytes and MIL-100(Fe)-NH2, thereby gaining a deeper understanding of adsorption behavior.

[0077] Thermodynamic data of MIL-100(Fe)-NH2 and six pesticides during the complex formation process were calculated. The binding energies of the six pesticide molecules (azoxystrobin AZ, indoxacarb INX, triazophos TZP, dimethoate OMT, phosmet ODM, and fenpropathrin FNP) with MIL-100(Fe)-NH2 were analyzed. Figure 11 As shown. Figure 11In the figure, the binding energies are all negative, indicating that these complexes are stable and that the adsorption of pesticides on amino-functionalized MOFs is a spontaneous process, demonstrating the excellent adsorption capacity of MIL-100(Fe)-NH2.

Claims

1. A method for determining pesticides in water samples, characterized in that, The process includes the following steps: amino-modifying MIL-100(Fe) to obtain amino-functionalized MIL-100(Fe) material; using the amino-functionalized MIL-100(Fe) material as a matrix, analyzing and detecting pesticides in water samples using SALDI-TOF-MS.

2. The method for determining pesticides in water samples as described in claim 1, characterized in that, The testing conditions for the SALDI-TOF-MS are as follows: acquisition mode is positive ion mode, molecular weight scan range is 100-600 Da, laser frequency is 1000 Hz, and scan frequency is 400.

3. The method for determining pesticides in water samples as described in claim 1, characterized in that, The pesticides include one or more of the following: pyraclostrobin, chlorantraniliprole, indoxacarb, triazophos, benzyl sulfoxide, benzoxazine, chlorpyrifos sulfone, piperonyl butyl ether, phosmet, dimethoate, phorate, 3-hydroxycarbofuran, sulfoxide, oxadixyl, ethionyl sulfoxide, and benzyl sulfoxide.

4. The method for determining pesticides in water samples as described in claim 1, characterized in that, The amino-functionalized MIL-100(Fe) material is obtained by mixing and reacting MIL-100(Fe) and 3-amino-4,5-dihydroxybenzoic acid in water, with a mass ratio of MIL-100(Fe) to 3-amino-4,5-dihydroxybenzoic acid of 80:

30.

5. The method for determining pesticides in water samples as described in claim 4, characterized in that, The mixing reaction was carried out by stirring at room temperature for 1 to 2 hours.

6. The method for determining pesticides in water samples as described in claim 1, characterized in that, During the analysis and detection, the amino-functionalized MIL-100(Fe) material is prepared into a matrix solution, spotted onto a matching target plate, dried, and then dropped into the water sample to be tested. After the solvent evaporates and crystallizes, SALDI-TOF-MS testing is performed.

7. The method for determining pesticides in water samples as described in claim 6, characterized in that, The concentration of amino-functionalized MIL-100(Fe) material in the matrix solution was 1 mg / mL, and the volume ratio of the matrix solution to the water sample was 1:

1.

8. The method for determining pesticides in water samples according to any one of claims 1 to 7, characterized in that, The water sample is an extract of environmental water or agricultural products, and the extraction solvent used for the extract is water or a mixture of water and organic solvents.

9. The method for determining pesticides in water samples as described in claim 8, characterized in that, The agricultural product is tobacco leaves, and the extraction solvent is a methanol-water solution with a volume ratio of 60-80%.

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