Method for detecting multiple pesticide residues in tea leaves

Abstract

The invention relates to a method for detecting multiple pesticide residues in tea leaves, which is suitable for quantitative analysis of organophosphorus, organochlorine and pyrethroid pesticides. The method comprises the following steps: adding water and acetonitrile into a tea sample, extracting to form a first extraction system, centrifuging, taking supernate, concentrating, and mixing with normal hexane and a saturated sodium chloride solution to form a second extraction system; and respectively taking an n-hexane layer, blow-drying the n-hexane layer, dissolving the n-hexane layer by using an elution solvent, purifying the n-hexane layer by using a solid-phase extraction column, fixing the volume, filtering the n-hexane layer, and detecting the n-hexane layer by using a gas chromatograph-tandem mass spectrometer. The method is high in sensitivity, good in linearity and suitable for various tea leaf samples; a PSA / Carb combined filler and an acetone-ethyl acetate elution system are adopted, so that the purification effect and the operation safety are improved, and the method is suitable for popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of pesticide residue detection, and particularly relates to a method for detecting multi-pesticide residues in tea. Background Art

[0002] As a globally widely consumed beverage, the quality and safety of tea have always been highly regarded. Due to the inevitable use of various pesticides in the tea planting process to control pests and diseases, there are risks of pesticide residues in the final products to varying degrees. To ensure the health of consumers and the smooth progress of tea export trade, strict pesticide residue limit standards have been established in China, the European Union, the United States and other major tea consumption and export regions. For example, China's "National Food Safety Standard Maximum Residue Limits of Pesticides in Foods" (GB 2763-2021) and the European Union's "Regulation on Pesticide Residue Limits" (EC 396 / 2005). Under this background, it has become an urgent need in the industry to establish a high-throughput, low-interference, green and environmentally friendly method for detecting multi-pesticide residues in tea.

[0003] There are still three major technical difficulties in the application of existing detection methods. First, the matrix components of tea samples are complex, especially rich in interfering substances such as tea polyphenols, caffeine, pigments, etc. Among them, the caffeine content can reach 1-5%, which easily leads to matrix effect problems such as mass spectrometry ion suppression, false positives or quantitative deviations. Traditional purification methods such as QuEChERS or using a single filler solid-phase extraction column are often difficult to effectively remove the above interferences, and the purification effect is limited. Second, the ability to synchronously detect multiple pesticides is insufficient. Taking the currently widely used "GB 23200.113-2018 Determination of Organochlorine and Pyrethroid Pesticide Residues in Tea Gas Chromatography-Mass Spectrometry" as an example, this method only covers a small number of pesticide types, lacks compatibility with broad-spectrum pesticides such as organophosphorus and carbamate pesticides, and cannot meet the need for simultaneous detection of multiple pesticides in actual samples. Third, the extraction and elution solvents used in the standard method, such as acetonitrile-toluene, have strong toxicity. Long-term use not only poses risks to the health of experimental operators, but also is not conducive to the realization of laboratory environmental safety and the concept of green detection.

[0004] Although some public documents and patents have optimized the detection process, there are still obvious defects. For example, CN106124674A discloses a tea pretreatment technology with PSA / MgSO4 as the purification method, but it fails to solve the problem of caffeine interference, and the recovery rate of pesticides fluctuates greatly, with poor stability; CN104764832A uses a combined purification method of PSA / GCB column. Although it has a certain effect on removing pigments, the adsorption of GCB on polar pesticides is obvious, resulting in a significant reduction in detection sensitivity, and the recovery rate of some pesticides is even lower than 50%; in addition, although some high-throughput detection methods based on automated pretreatment equipment perform well in terms of efficiency, they rely on imported instruments, with high costs, and do not meet the popularization conditions of general laboratories, so their practical applications are limited. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for detecting multiple pesticide residues in tea, including the following steps: Weigh the tea sample, add water to soak it, and then add an acetonitrile solution for extraction to form a first extraction system; Centrifuge and separate the first extraction system, take the supernatant for nitrogen blowing and concentration, add n-hexane and saturated sodium chloride solution and mix them to form a second extraction system; Take the n-hexane layer in the second extraction system, dry it, dissolve it with an elution solvent, purify it through a solid-phase extraction column, make it up to volume, filter it, and then perform detection.

[0006] In some preferred embodiments, the feeding mass ratio of the tea sample to water in the first extraction system is 1:1 - 1:3.

[0007] In some preferred embodiments, the feeding mass ratio of the tea sample to water in the first extraction system is 1:1, 1:2, 1:3.

[0008] In some preferred embodiments, the feeding mass ratio of the tea sample to acetonitrile in the first extraction system is 1:1 - 1:5.

[0009] In some preferred embodiments, the feeding mass ratio of the tea sample to acetonitrile in the first extraction system is 1:1, 1:2, 1:3, 1:4, 1:5.

[0010] In some preferred embodiments, the feeding volume ratio of n-hexane to saturated sodium chloride solution in the second extraction system is 1:1 - 1:2.

[0011] In some preferred embodiments, the feeding volume ratio of n-hexane to saturated sodium chloride solution in the second extraction system is 1:1, 1:2.

[0012] In some preferred embodiments, the elution solvent is a mixed solution of acetone / ethyl acetate, and the feeding volume ratio of acetone to ethyl acetate is 1:1.

[0013] In some preferred embodiments, the solid-phase extraction column is a PSA / Carb column, and the packing specifications are 500 - 600 mg PSA and 6 - 10 mL Carb.

[0014] In some preferred embodiments, the solid-phase extraction column is a PSA / Carb column, and the packing specifications are 500 mg PSA and 6 mL Carb.

[0015] In some preferred embodiments, the detection is performed by using a gas chromatograph-tandem mass spectrometer to quantitatively detect pesticide residues in tea samples.

[0016] In some preferred embodiments, the conditions of the gas chromatography are as follows: a capillary chromatographic column is used, the injection volume is 1 - 2 μL, the injection port temperature is 280 - 290 °C, the carrier gas is high-purity helium, and the chromatographic column temperature programming conditions are: the initial temperature is 60 - 70 °C, held for 1 - 2 min, heated to 150 - 160 °C at a rate of 15 - 20 °C / min, then heated to 230 - 240 °C at a rate of 10 - 15 °C / min, and finally heated to 300 - 310 °C at a rate of 25 - 30 °C / min and held for 5 - 10 min.

[0017] In some preferred embodiments, the mass spectrometry conditions are as follows: the ionization mode is an electron impact source, the electron energy is 70 - 80 eV, the ion source temperature is 230 - 240 °C, the transfer line temperature is 280 - 300 °C, the solvent delay time is 5 - 10 minutes, and the detection mode is a multiple reaction monitoring mode.

[0018] In some preferred embodiments, the conditions of the gas chromatography are as follows: a capillary chromatographic column is used, the injection volume is 2 μL, the injection port temperature is 290 °C, the carrier gas is high-purity helium, and the chromatographic column temperature programming conditions are: the initial temperature is 60 °C, held for 1 min, heated to 150 °C at a rate of 20 °C / min, then heated to 230 °C at a rate of 10 °C / min, and finally heated to 300 °C at a rate of 25 °C / min and held for 5 min.

[0019] In some preferred embodiments, the mass spectrometry conditions are as follows: the ionization mode is an electron impact source, the electron energy is 70 eV, the ion source temperature is 230 °C, the transfer line temperature is 280 °C, the solvent delay time is 5 minutes, and the detection mode is a multiple reaction monitoring mode.

[0020] In some preferred embodiments, the pesticide is one or more of organophosphorus pesticides, pyrethroid pesticides, or organochlorine pesticides.

[0021] In some preferred embodiments, the pesticide is methamidophos, mevinphos, acephate, chloroanisole, oxydemeton, phorate, α-BHC, dimethoate, simazine, atrazine, β-BHC, γ-BHC, δ-BHC, chlorpyrifos, methyl parathion, fenitrothion, phorate sulfoxide, phorate sulfone, chlorpyrifos, dicofol, isocarbophos, methyl isofenphos, methidathion, chlorpyrifos, triflunitron, trifluoroacetic acid ... cypermethrin, profenofos, PP-DDE, ethyl chlorpyrifos, PP-DDD, OP-DDT, PP-DDT, bifenthrin, cypermethrin, methoxychlor, etoxazole, cyfluthrin and high-efficiency cyfluthrin, permethrin, pyridaben, cyfluthrin and high-efficiency cyfluthrin, cypermethrin and high-efficiency cypermethrin, flucythrin, cypermethrin and S-cypermethrin, fenpropimorph, deltamethrin.

[0022] In some preferred embodiments, the tea sample is selected from green tea or oolong tea.

[0023] The present invention has the following beneficial effects: (1) The method provided by the present invention combines liquid-liquid extraction with solid-phase extraction to effectively remove interferences such as caffeine, polyphenols, and pigments, thereby improving purification selectivity and detection accuracy. It can simultaneously detect 44 pesticides with high sensitivity and good linearity, meeting strict regulatory requirements. It does not require derivatization or complex equipment, is easy to operate, has strong applicability, and is easy to promote at the grassroots level.

[0024] (2) The method provided by the present invention adopts a PSA / Carb dual-filler extraction column combination, which overcomes the problem of excessive adsorption of some polar pesticides by a single filler, takes into account the removal of polar and non-polar interferences, and improves the recovery consistency of the target product.

[0025] (3) The method provided by the present invention establishes a chromatography-mass spectrometry analysis procedure that can be simultaneously applied to multiple types of pesticides such as organophosphorus, organochlorine, and pyrethroids, achieving high-throughput detection capability for multiple pesticides with a single injection.

[0026] (4) The method provided by the present invention uses acetone-ethyl acetate instead of acetonitrile-toluene as the elution solvent, which reduces the toxicity of the organic solvent, improves operational safety and environmental protection, and is suitable for routine laboratory promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the total ion current of 44 pesticides at a concentration of 0.1 μg / mL; Figure 2 This is a comparison chart of the blank spectra of tea leaves pretreated according to standard GB 23200.113-2018 and this method. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions of the present invention, some non-limiting embodiments are further disclosed below to further illustrate the present invention in detail.

[0029] Explanation of terms: (1) Tea samples: Tea raw materials used for pesticide residue testing must be representative and meet the testing requirements. (2) Pesticide residues: The general term for pesticide precursors, toxic metabolites, degradation products and impurities present in plants, animals and the environment after pesticide use. (3) Gas chromatography-mass spectrometry (GC-MS): An instrument that combines the separation capabilities of gas chromatography with the qualitative and quantitative functions of mass spectrometry and is used for the analysis of complex mixtures. (4) DB-17 MS capillary column: a medium polarity gas chromatography column suitable for separating compounds with moderate thermal stability and polarity. (5) Electron impact ionization (EI): This is an ionization method that ionizes sample molecules by bombarding them with high-energy electrons. It is suitable for GC-MS analysis. (6) Multiple ion monitoring mode (SIM): The mass spectrometer selects specific ions for detection, improving the sensitivity and selectivity of the target compound. (7) Sample pretreatment: The process of preparing samples by physical or chemical methods to make them suitable for instrumental analysis. (8) Solid phase extraction (SPE) cartridge: a cartridge filled with adsorbent used to separate and enrich target compounds from complex matrices. (9) PSA filler: Ethylenediamine-N-propyl silanized filler, used to remove organic acids and polar impurities in samples. (10) Carb filler: graphitized carbon black filler, mainly used for adsorbing non-polar and medium-polar compounds. (11) Anhydrous sodium sulfate: a commonly used desiccant used to remove moisture from organic solvents. (12) Matrix-matched standard curve: A curve established by preparing standard solutions with blank matrix to reduce the influence of matrix effect on quantification. (13) Recovery rate: The ratio of the detected amount of target compound in the spiked sample to the actual added amount, which is used to evaluate the accuracy of the method. (14) Relative standard deviation (RSD): The ratio of the standard deviation to the mean, which indicates the precision of the analysis results. (15) Matrix effect: The sample matrix interferes with the response of the target compound, resulting in signal suppression or enhancement. (16) Limit of detection (LOD): The lowest concentration of the target compound that can be reliably detected by the method, usually determined by a signal-to-noise ratio of 3:1. (17)Limit of Quantitation (LOQ): The lowest concentration at which the method can accurately quantify the target compound, usually determined by a signal-to-noise ratio of 10:1. (18)Nitrogen blow tube: A glass tube used for nitrogen blow concentration, which evaporates the solvent through a nitrogen stream to enrich the target. (19)Acetone / ethyl acetate solvent: A mixed solvent commonly used for the extraction or purification of pesticide residues. (20)Acetone / n-hexane solvent: A mixed solvent of non-polar and polar solvents, suitable for the extraction of various pesticides. (21)Pulse splitless injection: A gas chromatography injection technique that rapidly injects the sample into the chromatographic column through a high-pressure pulse. (22)Programmed temperature rise: In gas chromatography, the column temperature is increased according to a set program to optimize the separation effect. (23)Linear range: The range in which the instrument response is linearly related to the concentration of the target. (24)Peak area: The integrated area corresponding to the peak in the chromatogram, used for quantitative analysis. (25)Mass concentration: The content of the target compound per unit volume or mass, commonly expressed as μg / mL or mg / kg. (26)Target compound: A specific pesticide or chemical substance that needs to be qualitatively and quantitatively analyzed in the detection method. (27)Liquid-liquid extraction (LLE): A method for separating the target by utilizing the difference in the partition coefficients of two immiscible solvents. (28)Soaking pre-dissolution: A pretreatment step of soaking the sample in a solvent to preliminarily dissolve the target. (29)Centrifuge tube with stopper: A centrifuge tube with a sealed cap, used for sample oscillation, extraction, and centrifugation. (30)Multi-tube vortex mixer: A device that can simultaneously vortex and oscillate multiple samples, improving the efficiency of pretreatment. (31)Analytical balance: A high-precision balance used for accurately weighing samples or standards. (32)Rotary evaporation: A technique for concentrating samples by evaporating the solvent through reduced pressure and heating while rotating. (33)Tea matrix: Other components in tea besides the target compound, which may interfere with the analysis results. (34)Spiked recovery experiment: An experiment of adding a known amount of the target to a blank sample to verify the accuracy of the method. (35)Standard solution in matrix: A standard solution prepared with a blank matrix, used to correct the matrix effect. (36)Mixed standard solution: A standard solution containing multiple target compounds, used for multi-residue analysis. (37)Sample purification efficiency: The ability of the pretreatment process to remove impurities, which affects the sensitivity and accuracy of the method. (38)Dilution gradient series: Dilute the standard solution proportionally into different concentrations for establishing the standard curve. (39)Minimum added concentration: The lowest spiked concentration that can be accurately determined in method validation. (40)Pesticide compound standard curve: The linear relationship between the response value and the concentration established by a series of concentration standard solutions.

[0030] Sample preparation: Crush the tea samples and sieve them (20 mesh), then put them into sealed plastic bags and store them in a refrigerator at -18 °C.

[0031] Instruments and equipment: Gas chromatograph (8890) - tandem mass spectrometer (7000D), DB-17 MS capillary column (30 m × 0.25 mm × 0.25 μm): Agilent Technologies; GL-20G-II low-high speed centrifuge: Shanghai Anting Scientific Instrument Factory; SDC-3000 multi-tube vortex mixer: Dou Dian Biotechnology Co., Ltd.; JJ323BC analytical balance: Changshu Shuangjie Testing Instrument Factory.

[0032] Example 1 Experimental procedure: Weigh 5.00 g of dry green tea or oolong tea samples respectively and place them in 50 mL centrifuge tubes. Add 10 mL of water respectively and soak at room temperature for 30 min to promote full expansion and pre-dissolution of the samples. Then add 20 mL of acetonitrile, shake well for 5 min, centrifuge at 4000 r / min for 5 min using a high-speed centrifuge, take 2 mL of the supernatant and transfer it to a new 10 mL stoppered centrifuge tube, add 5 mL of n-hexane and 5 mL of saturated sodium chloride solution, vortex vigorously for 1 min and then let it stand for layer separation. Take the upper n-hexane layer and transfer it to a nitrogen blowing tube, and dry it under nitrogen.

[0033] Dissolve the dried residue with 2 mL of acetone / ethyl acetate (feed volume ratio 1:1) and pass it through a self-made solid-phase extraction column. This solid-phase extraction column contains 500 mg of PSA and 6 mL of Carb packing, and about 2 cm thick anhydrous sodium sulfate is added on top to remove moisture. The column is activated with 5 mL of acetone / ethyl acetate (feed volume ratio 1:1) before use. After the sample is loaded onto the column, elute the target components with 10 mL of the same ratio solvent, collect the eluate, evaporate it to nearly dry in a 40 °C water bath rotary evaporator, and finally make the volume up to 1 mL with acetone / n-hexane (feed volume ratio 1:1). The sample is filtered through a 0.22 μm microporous filter membrane and used for gas chromatography-mass spectrometry detection.

[0034] A gas chromatography-mass spectrometry (GC-MS) instrument was used, with a DB-17 MS chromatographic column (30 m × 0.25 mm × 0.25 μm); the inlet temperature was set at 290 °C, the carrier gas was high-purity helium, and the flow rate was 2.0 mL / min. The temperature programming was as follows: the initial temperature was maintained at 60 °C for 1 min, then increased to 150 °C at a rate of 20 °C / min, then increased to 230 °C at a rate of 10 °C / min, and finally increased to 300 °C at a rate of 25 °C / min and maintained for 5 min. The injection method was pulsed splitless injection, and the injection volume was 2 μL. Mass spectrometry detection used an electron impact ionization source, with an energy of 70 eV, an ion source temperature of 230 °C, a transfer line temperature of 280 °C, and a multiple ion monitoring mode was adopted.

[0035] Detection of pesticide recovery rate: In this paper, the method of optimizing the solid-phase extraction column was used for pretreatment, and gas chromatography-tandem mass spectrometry was used as the detection instrument. Under the optimal experimental conditions, the average recovery rates of 44 compounds in green tea were 62.3 - 98.5%, and the relative standard deviation range was 1.9 - 9.7%. In oolong tea, the average recovery rates were 73.5 - 108.7%, and the relative standard deviation range was 1.2 - 10.3%.

[0036] Example 2 The mass ratio of tea sample to water for feeding was 1:1, and the other conditions were the same as in Example 1.

[0037] This example investigated the effect of reducing the ratio of tea sample to water to 1:1 on the recovery rate of methamidophos. The results showed that the recovery rate of methamidophos in green tea was 86.4%, and in oolong tea was 88.2%, with a relative standard deviation of 4.8% - 5.1%.

[0038] Example 3 The mass ratio of tea sample to acetonitrile for feeding was 1:2, and the other conditions were the same as in Example 1.

[0039] On the premise of maintaining the ratio of tea sample to water at 1:2, this example reduced the acetonitrile ratio to 1:2. The results showed that the average recovery rates of methamidophos in green tea and oolong tea decreased to 81.5% and 84.7% respectively.

[0040] Example 4 The volume ratio of n-hexane to saturated sodium chloride for feeding was adjusted to 1:2, and the other conditions were the same as in Example 1.

[0041] This example aimed to explore the effect of enhancing the volume of the aqueous phase (sodium chloride solution) on the liquid-liquid extraction process. The experimental results showed that the average recovery rates of methamidophos in green tea and oolong tea were 85.2% and 88.9% respectively.

[0042] Example 5 The specifications of the solid-phase extraction column packing were adjusted to 600 mg PSA and 10 mL Carb, and the other conditions were the same as those in Example 1.

[0043] This example aims to explore the effects of different specifications of PSA / Carb solid-phase extraction columns on the purification efficiency and the recovery rate of target pesticides. The experimental results show that the recovery rate of methamidophos in green tea samples is 94.1%, and in oolong tea samples is 95.8%, and the relative standard deviations are both controlled within 3.2%.

[0044] Example 6: Linear range, detection limit, quantification limit and matrix effect of the method Under the optimized experimental conditions, the mixed stock solution of 44 pesticide standard solutions was diluted with the extract of blank tea samples to prepare a series of matrix-matched standard solutions with concentrations of 10 μg / L, 20 μg / L, 50 μg / L, 100 μg / L, 200 μg / L, 500 μg / L and 1000 μg / L. After detection, the standard curves were plotted. The detection limits of 44 pesticide compounds in the matrix were calculated at 3 times the signal-to-noise ratio, and the minimum added concentration was used as the quantification limit. As can be seen from Table 2, in the range of 10 - 1000 μg / L, the mass concentrations of 44 pesticide compounds showed good linear relationships with their peak areas, and the correlation coefficients were all > 0.99. The detection limits of 44 compounds in green tea and oolong tea were 0.001 - 0.025 mg / kg and 0.001 - 0.03 mg / kg respectively, and the quantification limit of 44 compounds was 0.05 mg / kg, indicating that the method in this paper meets the actual detection requirements. The experimental results show that the matrix effects of each brand of tea are different, so matrix-matched standard curves were used for quantification.

[0045] Table 2 Linear range, detection limit, correlation coefficient, matrix effect and quantification limit of 44 pesticides in oolong tea and green tea

[0046] Example 7: Spike recovery test A mixed standard solution of 44 pesticides at three levels of 0.05 mg / kg, 0.1 mg / kg and 0.5 mg / kg was added to the blank tea matrix. Six parallel experiments were carried out for each spiked level, and after optimizing the detection conditions, the determination was carried out. The results are shown in Table 3. As can be seen from Table 3, the average recoveries of 44 compounds in green tea were 62.3 - 98.5%, and the relative standard deviation range was 1.9 - 9.7%. The average recoveries of 44 compounds in oolong tea were 73.5 - 108.7%, and the relative standard deviation range was 1.2 - 10.3%. Thus, it can be seen that the accuracy and precision of this method are relatively high, and it can be used to determine 44 kinds of pesticide residues in tea samples.

[0047] Table 3 Average Recovery Rates and Precision of 44 Pesticides in Green Tea and Oolong Tea

[0048] Comparative Example 1: Selection of Eluent The eluents acetonitrile - toluene (3:1, V / V) of the GB 23200.113 - 2018 standard and the eluents acetone - n - hexane (feed volume ratio of 1:1) and acetone - ethyl acetate (feed volume ratio of 1:1) designed in the experiment were compared. The recovery rates of 44 pesticides at the 0.1 mg / kg level were investigated. The experimental results showed that when the eluent was acetonitrile and toluene, the recovery rates were between 71.0% - 107%. When the eluent was acetone - n - hexane (feed volume ratio of 1:1), except for the recovery rate of acephate which was only 32%, the other 44 compounds were basically between 75.3% - 105%. As can be seen from its structural formula, it belongs to pesticides with relatively large polarity. Therefore, n - hexane was replaced with ethyl acetate for elution, and the recovery rates between 75.3% - 105% met the detection requirements. The elution abilities of the eluents of the two methods for 44 compounds were basically the same. However, the toxicity of the eluent toluene in the standard is much greater than that of acetone, and acetonitrile and toluene require a long time during the concentration process and toluene causes relatively large harm to the environment and the human body. Therefore, in this study, acetone - ethyl acetate (feed volume ratio of 1:1) was selected as the test eluent.

[0049] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for detecting multiple pesticide residues in tea, characterized in that, It includes the following steps: Weigh the tea sample, add water to soak it, and then add an acetonitrile solution for extraction to form a first extraction system; Centrifuge and separate the first extraction system, take the supernatant for nitrogen blowing and concentration, add n-hexane and saturated sodium chloride solution and mix them to form a second extraction system; Take the n-hexane layer in the second extraction system, dry it, dissolve it with an elution solvent, purify it through a solid-phase extraction column, make up the volume, filter it, and then conduct detection.

2. The detection method according to claim 1, wherein In the first extraction system, the mass ratio of the tea sample to water for feeding is 1:1 - 1:3, preferably 1:

2.

3. The detection method according to claim 1, characterized in that, In the first extraction system, the mass ratio of the tea sample to acetonitrile for feeding is 1:1 - 1:5, preferably 1:

4.

4. The detection method according to claim 1, characterized in that In the second extraction system, the volume ratio of n-hexane to saturated sodium chloride solution for feeding is 1:1 - 1:2, preferably 1:

1.

5. The detection method according to claim 1, wherein The elution solvent is a mixed solution of acetone / ethyl acetate, and the volume ratio of acetone to ethyl acetate for feeding is 1:

1.

6. The detection method according to claim 1, wherein The solid-phase extraction column is a PSA / Carb column, and the packing specifications are 500 - 600 mg PSA and 6 - 10 mL Carb, preferably 500 mg PSA and 6 mL Carb.

7. The detection method according to claim 1, wherein The detection uses a gas chromatograph-tandem mass spectrometer to quantitatively detect the pesticide residues in the tea sample.

8. The detection method according to claim 10, wherein The conditions of the gas chromatography are as follows: using a capillary chromatographic column, the injection volume is 1 - 2 μL, the injection port temperature is 280 - 290 °C, the carrier gas is high-purity helium, and the chromatographic column program temperature rising conditions are: the initial temperature is 60 - 70 °C, hold for 1 - 2 min, rise to 150 - 160 °C at a rate of 15 - 20 °C / min, then rise to 230 - 240 °C at a rate of 10 - 15 °C / min, and finally rise to 300 - 310 °C at a rate of 25 - 30 °C / min and hold for 5 - 10 min; and / or, the mass spectrometry conditions are: the ionization mode is electron impact source, the electron energy is 70 - 80 eV, the ion source temperature is 230 - 240 °C, the transfer line temperature is 280 - 300 °C, the solvent delay time is 5 - 10 minutes, and the detection mode is multiple reaction monitoring mode; Preferably, the conditions of the gas chromatography are as follows: using a capillary chromatographic column, the injection volume is 2 μL, the injection port temperature is 290 °C, the carrier gas is high-purity helium, and the chromatographic column program temperature rising conditions are: the initial temperature is 60 °C, hold for 1 min, rise to 150 °C at a rate of 20 °C / min, then rise to 230 °C at a rate of 10 °C / min, and finally rise to 300 °C at a rate of 25 °C / min and hold for 5 min; and / or, the mass spectrometry conditions are: the ionization mode is electron impact source, the electron energy is 70 eV, the ion source temperature is 230 °C, the transfer line temperature is 280 °C, the solvent delay time is 5 minutes, and the detection mode is multiple reaction monitoring mode.

9. The detection method according to claim 1, characterized in that The pesticide is one or more of organophosphorus pesticides, pyrethroid pesticides or organochlorine pesticides, preferably methamidophos, mevinphos, acephate, chlorobenzene methyl ether, omethoate, phorate, α-hexachlorocyclohexane, dimethoate, simazine, atrazine, β-hexachlorocyclohexane, γ-hexachlorocyclohexane, δ-hexachlorocyclohexane, chlorpyrifos-methyl, parathion-methyl, fenitrothion, phorate sulfoxide, phorate sulfone, chlorpyrifos, dicofol, isocarbophos, isofenphos-methyl, methidathion, insectevin, fluorodifen, profenofos, PP-DDE, ethyl chlorobenzilate, PP-DDD, OP-DDT, PP-DDT, bifenthrin, fenpropathrin, methoxychlor, etoxazole, cyhalothrin and lambda-cyhalothrin, permethrin, pyridaben, cyfluthrin and beta-cyfluthrin, cypermethrin and deltamethrin, flucythrinate, fenvalerate and esfenvalerate, difenoconazole, deltamethrin.

10. The detection method according to claim 1, characterized in that, The tea sample is selected from green tea or oolong tea.

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