Extraction detection treatment method

Abstract

The invention discloses an extraction detection treatment method, and belongs to the technical field of agricultural product safety detection. The method comprises the following steps: homogenizing and extracting a sample by using an extraction solvent, adding a multifunctional magnetic composite material of which the surface is modified with a weak cation exchange group, adjusting the pH value to 6-9, and carrying out vortex adsorption; and separating the material through an external magnetic field, washing, eluting by using an eluent compatible with a liquid chromatography mobile phase, collecting the eluent, and directly injecting the eluent into LC-MS / MS or HPLC for analysis. The magnetic composite material is formed by compounding Fe3O4 nanoparticles, C18 bonded silica gel and a covalent organic framework material, has multiple adsorption mechanisms, and can synchronously enrich various pesticide residues such as organic phosphorus, pyrethroids, carbamates and neonicotinoid. The method is easy and convenient to operate, good in purification effect, stable in recovery rate and suitable for high-throughput rapid screening of pesticide residues in matrixes of various agricultural products such as fruits, vegetables and grains.

Description

Technical Field

[0001] This invention relates to the field of agricultural product safety testing technology, specifically to an extraction and detection method based on multifunctional magnetic composite materials, which is particularly suitable for rapid pretreatment and detection of various pesticide residues in agricultural products such as fruits, vegetables, and grains. Background Technology

[0002] The detection of pesticide residues in agricultural products is a crucial step in ensuring food safety and public health. With the diversification of pesticide types and the increase in usage, traditional pretreatment methods such as liquid-liquid extraction and solid-phase extraction often suffer from problems such as cumbersome operation, large amounts of organic solvents, low recovery rates, and difficulty in simultaneously enriching multiple pesticides. In particular, they are easily affected by pigments, proteins, and oils in complex matrices, which can impact the sensitivity and accuracy of detection.

[0003] Currently, while QuEChERS technology has improved pretreatment efficiency to some extent, it still suffers from limited purification effects, easy clogging of packing materials, and difficulty in achieving high-throughput automation. Particularly in the simultaneous detection of multiple pesticide residues, existing methods often rely on the combined use of various adsorbent materials, increasing operational complexity and cost, and making it difficult to achieve balanced adsorption and efficient elution for pesticides with significant polarity differences.

[0004] Furthermore, while magnetic solid-phase extraction (MSE) technology has been applied in environmental and biological samples, a magnetic composite material system that combines high adsorption capacity, good selectivity, reusability, and compatibility with subsequent chromatographic detection systems is still lacking in the detection of multiple pesticide residues in agricultural products. Therefore, developing a simple, efficient, and effective magnetic extraction method suitable for the simultaneous detection of multiple pesticide residues is of significant practical value and technical necessity. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned technical difficulties and provide a magnetic extraction method that is simple to operate, highly efficient in purification, and suitable for simultaneous detection of multiple pesticide residues.

[0006] To achieve the above objectives, the technical solution adopted is: an extraction and detection processing method, comprising the following steps: (1) Sample pretreatment: After homogenizing the agricultural product sample to be tested, add the extraction solvent containing the internal standard and vortex mix; (2) Magnetic solid phase extraction purification: Add multifunctional magnetic composite material to the extract, adjust the pH to 6-9, and vortex adsorption for 5-20 min; the multifunctional magnetic composite material is composed of Fe3O4 nanoparticles, C18 bonded silica gel and covalent organic framework material, and the surface is modified with weak cation exchange groups; (3) Magnetic separation and washing: Separate the adsorbent material with an external magnetic field, discard the supernatant, and wash with washing liquid; (4) Elution and detection: Elute with an eluent compatible with the liquid chromatography mobile phase, collect the eluent and directly inject it into LC-MS / MS or HPLC for analysis.

[0007] Furthermore, in the multifunctional magnetic composite material, the mass ratio of Fe3O4 nanoparticles, C18 bonded silica gel, and covalent organic framework material is 1:0.5-2:0.2-1; the covalent organic framework material is triazine-based COF, formed by the reaction of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine with 2,5-dihydroxyterephthalic acid.

[0008] Furthermore, the extraction solvent is an acetonitrile solution containing 1% acetic acid, and the mass-to-volume ratio of the sample to the extraction solvent is 1:1 to 1:3; the reagent used to adjust the pH is an ammonium acetate buffer solution.

[0009] Furthermore, the washing solution is an acetonitrile-water solution with a washing volume of 2 to 5 mL; the eluent is an acetonitrile-water-formic acid solution, wherein the volume fraction of acetonitrile is 20% to 40% and the volume fraction of formic acid is 0.1% to 0.2%.

[0010] Furthermore, the elution method is vortex-assisted elution, the time is 5-10 min, and the elution volume is 2-5 mL; magnetic separation is achieved using a porous magnetic separation plate or an automated magnetic bead extractor.

[0011] Furthermore, the detection is performed by LC-MS / MS analysis, using multiple reaction monitoring mode.

[0012] Furthermore, the pesticides include at least three of the following: organophosphates, pyrethroids, carbamates, and neonicotinoids.

[0013] Furthermore, the agricultural product sample includes at least one of fruits, vegetables, and grains.

[0014] Furthermore, the multifunctional magnetic composite material can be reused more than three times, and after each use, it is regenerated through washing and drying. The extraction and detection processing method provided by this invention has been systematically optimized based on existing magnetic solid-phase extraction technology, and has the following beneficial effects: 1. Improved the simultaneous enrichment efficiency of multiple pesticide residues. By combining Fe3O4 nanoparticles, C18 bonded silica gel and triazine covalent organic framework materials, and introducing weak cation exchange groups, this magnetic material has multiple interaction mechanisms such as hydrophobicity, π-π stacking, hydrogen bonding and ion exchange.

[0015] 2. The pretreatment process has been simplified and the operational stability has been enhanced. External magnetic field separation is used to replace centrifugation or filtration steps, and vortex-assisted adsorption and elution are combined to significantly shorten the sample processing time.

[0016] 3. It reduces the cost of a single test and supports high-throughput processing. The magnetic composite material can be reused at least 3 times after washing and drying.

[0017] 4. This method is applicable to the pretreatment of various agricultural product matrices. By using an acetonitrile solution containing 1% acetic acid as the extraction solvent during the extraction stage, combined with pH adjustment and washing steps, interference from pigments, organic acids, and other matrices can be effectively reduced. This method has good matrix applicability in typical agricultural products such as fruits, vegetables, and grains, providing reliable pretreatment support for the simultaneous detection of multiple pesticide residues. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Example 1: An extraction and detection processing method, comprising the following steps: (1) Sample pretreatment: After homogenizing the agricultural product sample to be tested, add the extraction solvent containing the internal standard and vortex mix; (2) Magnetic solid phase extraction purification: Add multifunctional magnetic composite material to the extract, adjust the pH to 6-9, and vortex adsorption for 5-20 min; the multifunctional magnetic composite material is composed of Fe3O4 nanoparticles, C18 bonded silica gel and covalent organic framework material, and the surface is modified with weak cation exchange groups; (3) Magnetic separation and washing: Separate the adsorbent material with an external magnetic field, discard the supernatant, and wash with washing liquid; (4) Elution and detection: Elute with an eluent compatible with the liquid chromatography mobile phase, collect the eluent and directly inject it into LC-MS / MS or HPLC for analysis.

[0020] The preparation method of the multifunctional magnetic composite material includes the following steps: (1) Preparation of Fe3O4 nanoparticles: Weigh out FeCl3·6H2O and FeCl2·4H2O, dissolve them in deionized water at a molar ratio of 2:1, stir and heat to 80°C under nitrogen protection, add ammonia dropwise until pH=10, and continue the reaction for 1 h. After the reaction is complete, collect the precipitate by magnetic separation, wash it alternately with deionized water and ethanol until neutral, dry it under vacuum at 60°C, and grind it for later use.

[0021] (2) Preparation of COF materials: 2,4,6-Tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 2,5-dihydroxyterephthalic acid (DHTA) were dissolved in a 1:1 molar ratio in a mixed solvent of 1,4-dioxane and butanol. Acetic acid catalyst was added, and the reaction was carried out at 70 °C for 48 h. After the reaction was completed, the precipitate was collected by centrifugation, washed successively with DMF and methanol, and dried under vacuum at 60 °C.

[0022] (3) Composite material assembly and functionalization: Fe3O4 nanoparticles, C18 bonded silica gel, and the above-mentioned COF material were dispersed in acetonitrile at a mass ratio of 1:1:0.5. The mixture was ultrasonically treated for 30 min, followed by the addition of an appropriate amount of succinic anhydride (for introducing carboxyl weak cation exchange groups), and the reaction was stirred at 60 °C for 6 h. After the reaction was completed, the product was magnetically separated, washed three times with acetonitrile, and dried under vacuum at 60 °C to obtain a multifunctional magnetic composite material with carboxyl weak cation exchange groups modified on its surface.

[0023] The weak cation exchange group is at least one of carboxyl (-COOH), sulfonic acid (-SO3H), or phosphate (-PO3H2), preferably carboxyl. These groups can partially ionize under weakly acidic to neutral conditions and adsorb positively charged pesticide molecules (such as organophosphates, carbamates, etc.) through electrostatic interactions, thereby enhancing the adsorption selectivity of the material for polar pesticides.

[0024] The washing solution has a pH range of 4.0 to 6.0, preferably 5.0. Under this pH condition, acidic interfering substances in the sample matrix can be effectively removed, while avoiding premature elution of the target pesticide.

[0025] The pH range of the eluent is 2.0–4.0, preferably 3.0. Under acidic conditions, the protonation degree of the weak cation exchange groups is increased, and the electrostatic interaction is weakened, which is conducive to the efficient desorption of pesticide molecules. Moreover, this pH range is compatible with the LC-MS / MS mobile phase and requires no subsequent adjustment.

[0026] I. Experimental Materials and Instruments Samples: Commercially available apple, spinach, and rice samples were homogenized and then used for later use.

[0027] Standards and reagents: Pesticide standards: chlorpyrifos (organophosphate), cypermethrin (pyrethroid), carbofuran (carbamate), and imidacloprid (neonicotinoid), all with a purity ≥98% and a stock solution concentration of 100 mg / L (solvent is acetonitrile).

[0028] Internal standard: deuterated chlorpyrifos (d10), concentration 10 mg / L.

[0029] Extraction solvent: Acetonitrile solution containing 1% (v / v) acetic acid.

[0030] pH adjuster: 0.1 M ammonium acetate buffer solution (pH 7.0).

[0031] Washing solution: Acetonitrile-water (30:70, v / v).

[0032] Eluent: Acetonitrile-water-formic acid (30:70:0.15, v / v / v).

[0033] Multifunctional magnetic composite material: prepared in the laboratory (see supplementary examples for preparation method), with a mass ratio of Fe3O4:C18:triazine COF of 1:1:0.5, and the surface is modified with carboxyl groups (-COOH) as weak cation exchange groups.

[0034] Instruments and equipment: vortex mixer, porous magnetic separation plate (12 wells), high performance liquid chromatography-tandem mass spectrometry (LC-MS / MS, equipped with electrospray ionization source), pH meter, analytical balance (sensitivity 0.1 mg), high speed centrifuge.

[0035] II. Experimental Procedure (1) Sample pretreatment Accurately weigh 5.0 g (accurate to 0.01 g) of homogenized sample into a 50 mL polypropylene centrifuge tube. Add 10.0 mL of acetonitrile extraction buffer containing 1% acetic acid (sample to solvent mass-to-volume ratio 1:2), followed by 10.0 μL of deuterated chlorpyrifos internal standard solution (to achieve a final concentration of approximately 0.1 mg / L in the extraction buffer). Immediately vortex for 2 min to ensure thorough dispersion and wetting of the sample.

[0036] (2) Magnetic solid phase extraction purification Add 50.0 mg of the multifunctional magnetic composite material to the above extract. Adjust the pH of the mixture to 7.5 ± 0.2 using 0.1 M ammonium acetate buffer. Fix the centrifuge tubes on a vortex mixer and vortex at 200 rpm for 15 min.

[0037] (3) Magnetic separation and washing Place the centrifuge tubes on a porous magnetic separation plate. After 1 minute, the magnetic material will be completely adsorbed onto the tube walls. Carefully pour off and discard the supernatant. Add 3.0 mL of washing buffer (acetonitrile-water, 30:70) to the tubes and vortex for 30 seconds to clean the material surface. Place the tubes back on the magnetic separation plate for separation and discard the washing buffer. Repeat this washing step once.

[0038] (4) Elution and detection Add 3.0 mL of eluent (acetonitrile-water-formic acid, 30:70:0.15, pH approximately 3.0) to the washed adsorbent material. Vortex for 8 min to elute the target analyte. After magnetic separation, collect all eluent, filter directly through a 0.22 μm nylon needle filter without nitrogen blowing concentration, and transfer to an LC-MS / MS vial for analysis.

[0039] (5) LC-MS / MS analysis conditions Chromatographic conditions: Chromatographic column: C18 column (2.1 mm × 100 mm, 1.7 μm) Mobile phases: Phase A is 0.1% formic acid aqueous solution, and Phase B is acetonitrile. Gradient elution program: 0-2.0 min, 10% B; 2.0-8.0 min, 10% B → 90% B; 8.0-9.0 min, 90% B; 9.0-10.0 min, 90% B → 10% B.

[0040] Flow rate: 0.30 mL / min; column temperature: 40℃; injection volume: 5.0 μL.

[0041] Mass spectrometry conditions: Ion source: Electrospray ionization (ESI); Polarity: Positive ion mode.

[0042] Detection method: Multiple reaction monitoring (MRM).

[0043] Main parameters: Ion source temperature 150℃; desolvation gas temperature 500℃; conical gas flow rate 150 L / h; desolvation gas flow rate 1000 L / h.

[0044] The MRM monitoring ion pairs, cone voltage, and collision energy of the four pesticides and internal standards were determined after optimization (see Table 1).

[0045] Table 1: LC-MS / MS mass spectrometry parameters of four target pesticides and internal standards (Note: * indicates quantitative ions) .

[0046] III. Results and Discussion The above method was used to conduct spiked recovery experiments on blank samples of apples, spinach, and rice. Three spiked concentrations were set: low (0.01 mg / kg), medium (0.05 mg / kg), and high (0.10 mg / kg), with each level measured in triplicate (n=3). Quantification was performed using the internal standard method (deuterated chlorpyrifos). The average recovery rate and relative standard deviation (RSD) of each pesticide were calculated, and the method limit of detection (LOD, signal-to-noise ratio S / N=3) and limit of quantitation (LOQ, signal-to-noise ratio S / N=10) were evaluated.

[0047] 1. Method accuracy and precision The results are shown in Table 2. In three different agricultural product matrices, the average recoveries of the four pesticides at three spiking levels ranged from 85.2% to 108.7%, with all RSDs ≤ 9.5%. This indicates that the method has good accuracy and repeatability at different concentrations and in different matrices, meeting the general requirements for pesticide multi-residue analysis (typically requiring recoveries of 70%-120% and RSD ≤ 20%).

[0048] Table 2: Spiking recoveries and precision of four pesticides in three agricultural products (n=3) .

[0049] 2. Method sensitivity Calculated using the signal-to-noise ratio (S / N) method, the limits of detection (LODs) for chlorpyrifos, cypermethrin, carbofuran, and imidacloprid are 0.001 mg / kg, 0.002 mg / kg, 0.003 mg / kg, and 0.002 mg / kg, respectively; the limits of quantitation (LOQs) are 0.003 mg / kg, 0.005 mg / kg, 0.010 mg / kg, and 0.005 mg / kg, respectively. This sensitivity meets the routine limit detection requirements for these pesticide residues in agricultural products both domestically and internationally.

[0050] 3. Assessment of matrix effects The matrix effect (ME) was assessed by comparing the slope ratios of pesticides in pure solvent standard curves and matrix-matched standard curves. The results showed that the matrix effects of the four pesticides in apple, spinach, and rice matrices ranged from 88% to 112%, indicating a weak to moderate matrix effect. This experiment used matrix-matched standard curves for quantification, effectively compensating for the matrix effect and ensuring the accuracy of the quantification.

[0051] IV. Conclusion Example 1 provides a detailed verification of the extraction and detection method provided by this invention. This method utilizes a self-made multifunctional magnetic composite material and, through optimized extraction, purification, washing, and elution steps, combined with LC-MS / MS detection, successfully achieved simultaneous analysis of four representative pesticides (chlorpyrifos, cypermethrin, carbofuran, and imidacloprid) in apples, spinach, and rice. The method verification results show that its accuracy, precision, and sensitivity all meet the technical specifications for multi-pesticide residue analysis, and the operation procedure is simple and rapid, making it suitable for high-throughput screening of multiple pesticide residues in the aforementioned agricultural product matrices.

[0052] Example 2: Performance Comparison of Multifunctional Magnetic Composite Materials with Different Mass Ratios This embodiment aims to verify the effect of different mass ratios of the multifunctional magnetic composite material in claim 2 on its adsorption performance.

[0053] I. Materials and Methods Three composite materials with different mass ratios were prepared respectively: A:Fe3O4:C18:COF = 1:0.5:0.2 B: Fe3O4:C18:COF = 1:1:0.5 (Same as Example 1) C:Fe3O4:C18:COF = 1:2:1 The sample was an apple sample, and the spike concentration was 0.05 mg / kg. The remaining steps were the same as in Example 1.

[0054] II. Results Composite material B (1:1:0.5) showed the highest recovery rate for all four types of pesticides (average 92%), while A and C achieved 85% and 89%, respectively. Material B exhibited the best overall adsorption performance within the adsorption equilibrium time (15 min).

[0055] Example 3: Comparison of different extraction solvent systems This embodiment aims to verify the effect of the extraction solvent system in claim 3.

[0056] I. Materials and Methods The extraction solvents were: pure acetonitrile, acetonitrile containing 1% acetic acid (same as in Example 1), and acetone containing 1% acetic acid.

[0057] The sample was spinach, and the other conditions were the same as in Example 1.

[0058] II. Results The acetonitrile system containing 1% acetic acid showed the highest recovery rate (102%) for polar pesticides (such as carbofuran), with an overall recovery rate ranging from 88% to 105%, which was superior to the other two solvents.

[0059] Example 4: Optimization and Validation of Washing and Eluting System This embodiment aims to verify the optimization effect of the washing liquid and elution liquid in claim 4.

[0060] I. Materials and Methods Comparison of washing solutions: water, acetonitrile-water (30:70), methanol-water (30:70) Comparison of eluents: acetonitrile-water (30:70), acetonitrile-water-formic acid (30:70:0.15), methanol-water-formic acid (30:70:0.15) The sample was rice, and the other conditions were the same as in Example 1.

[0061] II. Results When acetonitrile-water was used as the washing solution and acetonitrile-water-formic acid (30:70:0.15) was used as the eluent, the pesticide recovery rate was the highest (average 94%), and the chromatogram baseline was stable with the fewest interference peaks.

[0062] Example 5: Comparison of Vortex-Assisted Elution and Magnetic Separation Methods This embodiment aims to verify the selection of the elution method and magnetic separation method in claim 5.

[0063] I. Materials and Methods Elution methods: vortex-assisted (5, 10, 15 min) and ultrasound-assisted (10 min). Magnetic separation methods: Magnetic separation plates vs. automated magnetic bead extractors The sample was an apple, and the other conditions were the same as in Example 1.

[0064] II. Results Vortexing for 10 minutes yields the best elution results, with a stable recovery rate exceeding 90%. Automated extractors offer higher throughput, and their recovery rates are not significantly different from those of manual magnetic separation plates.

[0065] Example 6: Optimization of LC-MS / MS Multiple Reaction Monitoring Mode This embodiment aims to verify the applicability of the detection method in claim 6.

[0066] I. Materials and Methods Mass spectrometry methods: MRM mode vs. full scan mode The sample was spiked spinach, and the other conditions were the same as in Example 1.

[0067] II. Results In MRM mode, the signal-to-noise ratio of the four pesticides was improved by 3–5 times, and the detection limit was reduced to 0.001–0.002 mg / kg, which was significantly better than the full scan mode.

[0068] Example 7: Suitability verification for different pesticide categories This embodiment aims to verify the applicability of the method in claim 7 to different pesticide categories.

[0069] I. Materials and Methods The pesticide categories have been expanded to include: organophosphates (chlorpyrifos), pyrethroids (cypermethrin), carbamates (carbofuran), neonicotinoids (imidacloprid), and triazoles (tebuconazole). The samples were apples and rice, and the other conditions were the same as in Example 1.

[0070] II. Results The recoveries of all five pesticide classes were between 82% and 110% in both matrices, with RSD < 10%, indicating that the method has good class applicability.

[0071] Example 8: Applicability verification of different agricultural product samples This embodiment aims to verify the applicability of the method in claim 8 to different agricultural product samples.

[0072] I. Materials and Methods Sample types: Fruits (apples), Vegetables (spinach), Grains (rice), Tea (green tea) The remaining conditions are the same as in Example 1.

[0073] II. Results The pesticide recoveries in all samples ranged from 80% to 108%. The recoveries in tea were slightly higher due to interference from pigments and polyphenols, but still met the detection requirements.

[0074] Example 9: Verification of the reusability of magnetic composite materials This embodiment aims to verify the reusability of the multifunctional magnetic composite material described in claim 9 and to examine the changes in its pesticide adsorption capacity after multiple uses.

[0075] I. Materials and Methods 1. Materials and Reagents Multifunctional magnetic composite material: Same as in Example 1, but with surface modified with carboxyl weak cation exchange groups.

[0076] Pesticide standards: Chlorpyrifos (organophosphate) and Carbofuran (carbamate), both at a concentration of 100 mg / L.

[0077] Extraction solvent, washing solution, eluent, etc.: Same as in Example 1.

[0078] Sample: Apple sample, homogenized and ready for use.

[0079] 2. Reuse of experimental designs Using the same batch of magnetic composite material, repeat the following operation cycle 5 times: (1) Adsorption operation: Take 50 mg of material and perform adsorption experiment according to step (2) of Example 1. The spike concentration is 0.05 mg / kg.

[0080] (2) Washing and regeneration: After each use, wash the material three times with ethanol-water (1:1, v / v), 5 mL each time, vortex for 1 min, discard the washing liquid after magnetic separation, and dry at 60℃ for later use.

[0081] (3) Adsorption capacity determination: After each cycle, the adsorption capacity of the test material for chlorpyrifos and carbofuran was calculated based on the initial use capacity.

[0082] 3. Adsorption capacity determination method Prepare a series of pesticide standard solutions (0.01–0.5 mg / L), and conduct adsorption experiments according to step (2) of Example 1. Calculate the adsorption capacity (mg / g) of a unit mass of material by the concentration difference of the solution before and after adsorption.

[0083] II. Results and Analysis 1. The effect of repeated use on adsorption capacity The following table shows the decrease in the adsorption capacity of the material for two representative pesticides after it was reused five times: Number of times used Chlorpyrifos adsorption capacity reduction rate (%) Carbofuran adsorption capacity reduction rate (%) 1st time 0.0 0.0 2nd time 2.1 3.5 3rd 4.7 6.2 4th 7.8 9.1 5th 11.3 13.6

[0084] The results showed that the adsorption capacity of the material decreased slowly with increasing use. By the fifth use, the adsorption capacity for chlorpyrifos and carbofuran remained above 88.7% and 86.4% of the initial values, respectively, demonstrating good structural stability and reusability.

[0085] 2. Material structural stability analysis Scanning electron microscopy (SEM) was used to observe the morphology of the material after the first and fifth uses, and no obvious structural damage or agglomeration was found. Fourier transform infrared spectroscopy (FT-IR) analysis showed that the characteristic peaks of the functional groups on the material surface remained clear after repeated use, and no significant degradation was observed.

[0086] III. Conclusion This embodiment demonstrates through systematic repeated use experiments that the multifunctional magnetic composite material maintains a high pesticide adsorption capacity (>85%) after five reuses, exhibits structural stability, and shows no significant degradation of functional groups. This material possesses excellent regeneration capabilities and economic efficiency, making it suitable for repeated use in pesticide residue detection of agricultural products.

[0087] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0088] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An extraction and detection processing method, characterized in that... Includes the following steps: (1) Sample pretreatment: After homogenizing the agricultural product sample to be tested, add the extraction solvent containing the internal standard and vortex mix; (2) Magnetic solid phase extraction and purification: Add multifunctional magnetic composite material to the extract, adjust the pH to 6-9, and vortex adsorption for 5-20 min; the multifunctional magnetic composite material is composed of Fe3O4 nanoparticles, C18 bonded silica gel and covalent organic framework material, and the surface is modified with weak cation exchange groups. (3) Magnetic separation and washing: The adsorbent material is separated by an external magnetic field, the supernatant is discarded, and the material is washed with a washing solution; (4) Elution and detection: Elution was performed using an eluent compatible with the liquid chromatography mobile phase. The eluent was collected and directly injected into LC-MS / MS or HPLC for analysis.

2. The extraction and detection processing method according to claim 1, characterized in that: In the multifunctional magnetic composite material, the mass ratio of Fe3O4 nanoparticles, C18 bonded silica gel, and covalent organic framework material is 1:0.5-2:0.2-1; the covalent organic framework material is triazine-based COF, which is formed by the reaction of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine with 2,5-dihydroxyterephthalic acid.

3. The extraction and detection processing method according to claim 1, characterized in that: The extraction solvent is an acetonitrile solution containing 1% acetic acid, and the mass-volume ratio of the sample to the extraction solvent is 1:1 to 1:3; the reagent used to adjust the pH is an ammonium acetate buffer solution.

4. The extraction and detection processing method according to claim 1, characterized in that: The washing solution is an acetonitrile-water solution with a washing volume of 2 to 5 mL; the eluent is an acetonitrile-water-formic acid solution with an acetonitrile volume fraction of 20% to 40% and a formic acid volume fraction of 0.1% to 0.2%.

5. The extraction and detection processing method according to claim 1 or 4, characterized in that: The elution method was vortex-assisted elution, with a time of 5–10 min and an elution volume of 2–5 mL; magnetic separation was achieved using a porous magnetic separation plate or an automated magnetic bead extractor.

6. The extraction and detection processing method according to claim 1, characterized in that: The detection was performed by LC-MS / MS analysis using multiple reaction monitoring mode.

7. The extraction and detection processing method according to claim 1, characterized in that: The pesticides include at least three of the following: organophosphates, pyrethroids, carbamates, and neonicotinoids.

8. The extraction and detection processing method according to claim 1, characterized in that: The agricultural product samples include at least one of fruits, vegetables, and grains.

9. The extraction and detection processing method according to claim 1, characterized in that: The multifunctional magnetic composite material can be reused more than 3 times, and is regenerated after each use by washing and drying.