Pesticide residue detection method

Abstract

The invention relates to the technical field of pesticide residue detection, in particular to a pesticide residue detection method which comprises the following steps: (1) freezing and crushing a sample, and performing microwave extraction to obtain extract liquor; (2) detecting and analyzing the extract by adopting a gas chromatograph-mass spectrometer, and determining the content of pesticide residues in the sample; the gas chromatography conditions of the gas chromatograph-mass spectrometer are as follows: a chromatographic column heating procedure is as follows: the temperature is kept for 1-2 minutes at the temperature of 100-110 DEG C, the temperature is raised to 220-230 DEG C at the heating rate of 10-15 DEG C / min, then the temperature is raised to 320-330 DEG C at the heating rate of 20-25 DEG C / min, and the temperature is kept for 3-3.5 minutes. Pretreatment and detection conditions in the method are optimized, rapid and accurate detection of the pesticide residues in the fruit and vegetable food is achieved, the method is simple, and monitoring of the pesticide residues is easy to promote.

Description

Technical Field

[0001] This invention relates to the field of pesticide residue detection technology, specifically a method for detecting pesticide residues. Background Technology

[0002] Pesticide residues refer to the total amount of pesticide parent material, its metabolites, degradation products, and toxic impurities that remain in agricultural products, food, or environmental media after pesticide application. The detection of pesticide residues is crucial for protecting public health, addressing regulatory challenges, adapting to international trade, and promoting high-quality agricultural development. Currently, pesticide residue detection mainly includes biochemical assays and chromatographic methods. For example, Chinese patent (authorization announcement number CN112326646B) discloses a method for detecting pesticide residues in food, and Chinese patent application (publication number CN109001195A) discloses a method for detecting pesticide residues in vegetables. Existing detection methods mainly improve detection efficiency and ensure detection quality by optimizing extraction and detection devices and enzyme selection. However, due to the complexity of sample matrices, numerous interferences, and the need for rapid and accurate detection of multiple pesticide residues to meet practical requirements, higher demands are placed on detection methods. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for detecting pesticide residues. The method optimizes the coordination of pretreatment and detection conditions, effectively overcomes interference from samples, and enables rapid and accurate detection of pesticide residues in fruits, vegetables, and food. Furthermore, the method is simple and easy to promote the monitoring of pesticide residues.

[0004] This invention provides a method for detecting pesticide residues, comprising the following steps: (1) The sample was frozen, crushed and then microwave extracted to obtain the extract; (2) The extract was analyzed by gas chromatography-mass spectrometry to determine the pesticide residue content in the sample; The gas chromatography-mass spectrometry (GC-MS) conditions include: The column temperature program is as follows: hold at 100-110℃ for 1-2 min, increase the temperature to 220-230℃ at a rate of 10-15℃ / min, and then increase the temperature to 320-330℃ at a rate of 20-25℃ / min and hold for 3-3.5 min.

[0005] In one embodiment, the sample is a food product, which includes fruits and vegetables.

[0006] In one embodiment, the freezing method is liquid nitrogen freezing, and the temperature of liquid nitrogen freezing is -80~-90℃.

[0007] In one embodiment, the pulverization method is grinding, and the fineness of the grinding is <200 mesh.

[0008] In one embodiment, the microwave extraction step includes: placing the frozen and pulverized sample in a microwave extractor and performing microwave extraction with an extractant.

[0009] In one embodiment, the extractant is selected from at least one of methanol, ethanol, isopropanol, acetone, and N-methylpyrrolidone.

[0010] In one embodiment, the mass ratio of the sample to the extractant is 1:15-30.

[0011] In one embodiment, the mass ratio of the sample to the extractant is 1:20-25.

[0012] In one embodiment, the microwave power of the microwave extraction is 40-60W.

[0013] In one embodiment, the microwave power of the microwave extraction is 50-55W.

[0014] In one embodiment, the microwave extraction time is 20-30 minutes.

[0015] In one embodiment, the gas chromatographic conditions of the gas chromatography-mass spectrometry system further include: Inlet temperature: 250-280℃, split injection, split ratio 40-50:1; Chromatographic column: HP-5MS, 30m × 0.25mm × 0.25µm; Column flow rate: 1.0-1.2 mL / min; Carrier gas: High-purity helium, purity ≥ 99.999%.

[0016] In one embodiment, the mass spectrometry conditions of the gas chromatography-mass spectrometry system include: Ionization method: Electron impact ion source (EI), ion source temperature is 220-230℃, quadrupole temperature is 140-150℃; Scanning method: full scan, scanning range is 30-600m / z.

[0017] This invention involves freezing fruits and vegetables in liquid nitrogen at -80 to -90°C and then grinding them. This significantly inhibits thermal degradation reactions and avoids the damage to pesticide molecular structures caused by localized high temperatures from mechanical grinding, thus ensuring the accuracy of subsequent detection. On the other hand, it also facilitates efficient extraction.

[0018] Furthermore, this invention uses methanol as the extractant and performs microwave extraction at 40-60W for 20-30 minutes to efficiently extract the target pesticide, reduce impurity interference, and achieve a stable recovery rate of 80%-120% (RSD≤10%).

[0019] Based on this, the present invention further optimizes the column temperature program and other conditions by using an HP-5MS column, effectively solving the problem of peak overlap of multi-component pesticides, balancing separation efficiency and analysis time, and achieving complete separation of 21 pesticides.

[0020] Beneficial effects 1. This invention provides a method for detecting pesticide residues, which optimizes the combination of pretreatment and detection conditions to effectively overcome interference from samples, achieves rapid and accurate detection of pesticide residues in fruits, vegetables and food, and is simple and easy to promote the monitoring of pesticide residues.

[0021] 2. This invention involves freezing fruits and vegetables with liquid nitrogen at -80 to -90°C and then grinding them. This significantly inhibits thermal degradation reactions and avoids the damage to pesticide molecular structures caused by localized high temperatures generated by mechanical grinding, thus ensuring the accuracy of subsequent detection. On the other hand, it also facilitates efficient extraction.

[0022] 3. This invention uses methanol as the extractant and microwaves it for 20-30 minutes at 40-60W to efficiently extract the target pesticide, reduce impurity interference, and achieve a stable recovery rate of 80%-120% (relative standard deviation RSD≤10%).

[0023] 4. This invention, by employing an HP-5MS chromatographic column and further optimizing the column temperature program and other conditions, effectively solves the problem of peak overlap in multi-component pesticides, balances separation efficiency and analysis time, and achieves complete separation of 21 pesticides.

[0024] 5. The detection method provided by this invention can analyze more types of pesticides in a shorter time, and the detection results are highly accurate, meeting the needs of rapid detection. Attached Figure Description

[0025] Figure 1 The total ion current chromatogram obtained by the pesticide residue detection method provided in Example 1.

[0026] Figure 2 The total ion chromatogram obtained by a pesticide residue detection method provided for Comparative Example 1.

[0027] Figure 3 , Figure 4 Standard curves for each pesticide. Figure 3The numbers 1-12 correspond to propoxur, simazine, atrazine, chlorpyrifos, terbufos, cypermethrin, tetrafluorobenzyl, chlorpyrifos, tetrafluoromethrin, and triazophos, respectively. Figure 4 In the formulas 13-21, the corresponding compounds are synergistic ether, methamidophos, bifenthrin, cypermethrin, difenomethrin, permethrin, deltamethrin, cypermethrin, and deltamethrin, respectively. Detailed Implementation

[0028] Example 1 Embodiment 1 of the present invention provides a method for detecting pesticide residues, comprising the following steps: (1) The sample was frozen, crushed and then microwave extracted to obtain the extract; (2) The extract was analyzed by gas chromatography-mass spectrometry to determine the pesticide residue content in the sample; The gas chromatography-mass spectrometry (GC-MS) conditions include: The column temperature program was as follows: hold at 100℃ for 1 min, increase to 220℃ at a rate of 10℃ / min, and then increase to 320℃ at a rate of 20℃ / min and hold for 3 min.

[0029] The sample was vegetables (randomly selected sample).

[0030] The freezing method is liquid nitrogen freezing, and the temperature of liquid nitrogen freezing is -90℃.

[0031] The pulverization method is grinding, and the fineness of the grinding is 100 mesh.

[0032] The microwave extraction steps include: placing the frozen and pulverized sample in a microwave extractor and performing microwave extraction with an extractant.

[0033] The extractant is methanol, and the mass ratio of the sample to the extractant is 1:20.

[0034] The microwave power for the microwave extraction is 50W, and the extraction time is 20 minutes.

[0035] The gas chromatography-mass spectrometry (GC-MS) system also includes the following gas chromatography-mass spectrometry (GC-MS) conditions: Inlet temperature: 280℃, split injection, split ratio 50:1; Chromatographic column: HP-5MS, 30m × 0.25mm × 0.25µm; Column flow rate: 1.0 mL / min; Carrier gas: High-purity helium, purity ≥ 99.999%.

[0036] See gas chromatogram Figure 1 The chromatographic peaks in the spectrum were effectively separated.

[0037] The mass spectrometry conditions for the gas chromatography-mass spectrometry (GC-MS) system include: Ionization method: electron bombardment of ion source, ion source temperature 230℃, quadrupole temperature 150℃; Scanning method: full scan, scanning range is 30-600m / z.

[0038] Prepare standard solutions containing 21 pesticides according to the dosages in Table 1, and establish standard curves (see Table 2 for standard curves and ranges, and see the standard curve diagrams for each pesticide). Figure 3 , Figure 4 The pesticide residues and their content in the sample were determined by comparing the retention time, characteristic ions, and abundance of the sample and standard solution.

[0039] Table 1

[0040] Table 2

[0041] Comparative Example 1 Comparative Example 1 of the present invention provides a method for detecting pesticide residues, the specific implementation of which is the same as that of Example 1, except that the chromatographic column temperature program is replaced with: holding at 100°C for 1 min, increasing the temperature at a rate of 20°C / min to 320°C and holding for 3 min. See the gas chromatogram below. Figure 2 Some chromatographic peaks (chromatographic peaks 1 and 2) in the spectrum could not be effectively separated.

[0042] Performance testing The method provided in Example 1 was validated as follows.

[0043] (1) Prepare standard solutions containing 21 pesticides according to the dosage in Table 1.

[0044] Table 1

[0045] (2) The detection accuracy was verified according to the method shown in the example. The test was performed in parallel for 3 times, and the average recovery rate and standard deviation (repeatability) were calculated. The results are shown in Table 3.

[0046] Table 3

[0047] Analysis of the test results in Table 3 shows that the method provided in Example 1 has good recovery rates for 21 pesticides, all between 80% and 120%; the data repeatability is high, and the RSD ≤ 10% meets the standard for method validation and can meet the actual testing needs.

Claims

1. A method for detecting pesticide residues, characterized in that, Includes the following steps: (1) The sample was frozen, crushed and then microwave extracted to obtain the extract; (2) The extract was analyzed by gas chromatography-mass spectrometry to determine the pesticide residue content in the sample; The gas chromatography-mass spectrometry (GC-MS) conditions include: The column temperature program is as follows: hold at 100-110℃ for 1-2 min, increase the temperature to 220-230℃ at a rate of 10-15℃ / min, and then increase the temperature to 320-330℃ at a rate of 20-25℃ / min and hold for 3-3.5 min.

2. The method for detecting pesticide residues according to claim 1, characterized in that, The freezing method is liquid nitrogen freezing, and the temperature of liquid nitrogen freezing is -80~-90℃.

3. The method for detecting pesticide residues according to claim 1, characterized in that, The pulverization method is grinding, and the fineness of the grinding is <200 mesh.

4. The method for detecting pesticide residues according to claim 1, characterized in that, The microwave extraction steps include: placing the frozen and pulverized sample in a microwave extractor and performing microwave extraction with an extractant.

5. The method for detecting pesticide residues according to claim 4, characterized in that, The extractant is selected from at least one of methanol, ethanol, isopropanol, acetone, and N-methylpyrrolidone.

6. The method for detecting pesticide residues according to claim 4, characterized in that, The mass ratio of the sample to the extractant is 1:15-30.

7. The method for detecting pesticide residues according to claim 1, characterized in that, The microwave power for microwave extraction is 40-60W.

8. The method for detecting pesticide residues according to claim 1, characterized in that, The microwave extraction time is 20-30 minutes.

9. The method for detecting pesticide residues according to claim 1, characterized in that, The gas chromatography-mass spectrometry (GC-MS) system also includes the following gas chromatography-mass spectrometry (GC-MS) conditions: Inlet temperature: 250-280℃, split injection, split ratio 40-50:1; Chromatographic column: HP-5MS, 30m × 0.25mm × 0.25µm; Column flow rate: 1.0-1.2 mL / min; Carrier gas: High-purity helium, purity ≥ 99.999%.

10. The method for detecting pesticide residues according to claim 1, characterized in that, The mass spectrometry conditions for the gas chromatography-mass spectrometry (GC-MS) system include: Ionization method: Electron bombardment of the ion source, ion source temperature is 220-230℃, quadrupole temperature is 140-150℃; Scanning method: full scan, scanning range is 30-600m / z.

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