Method for determining residual quantity of cyprosulfamide in chive based on ultra-high performance liquid chromatography-tandem mass spectrometry

Abstract

The invention belongs to the technical field of cyprosulfuron, and particularly relates to a method for determining the residual quantity of cyprosulfuron in chive based on ultra-high performance liquid chromatography-tandem mass spectrometry. A sample is measured by using an ultra-high performance liquid chromatography-tandem mass spectrometry method, and the detection conditions are as follows: the liquid chromatography condition comprises that the flow rate is 0.25 mL / min; the mobile phase A is an aqueous solution, and the mobile phase B is methanol; the column box temperature is 40 DEG C; the sample size is 2 [mu] L; the constant current is 0-3 min, and 80% B is obtained; the mass spectrum conditions are as follows: the ionization source mode is ESI; the ionization source is positive in polarity; the temperature of an ion source is 110 DEG C; the temperature of the desolventizing gas is 450 DEG C; the capillary voltage is 3.5 kV; the type and flow of the desolventizing gas are nitrogen, 500L / Hr; and the type and the flow of the collision gas are argon, and the flow rate is 0.18 mL / min. The method is simple and convenient to operate, efficient, accurate and suitable for large-scale detection of cyprosulfuron residues in chives.

Description

Technical Field

[0001] This invention belongs to the field of cyclofop-propargyl technology, and in particular relates to a method for determining the residue of cyclofop-propargyl in scallions based on ultra-high performance liquid chromatography-tandem mass spectrometry. Background Technology

[0002] Cyproflanilide is a novel meta-diamide insecticide with characteristics such as high efficiency, low toxicity, broad insecticidal spectrum, rapid onset of action, long-lasting effect, and environmental friendliness; its common English name is Cyproflanilide. CAS name: N-[3-[[[2-bromo-4-[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]-6-(trifluoromethyl)phenyl]amino]carbonyl]-2-fluorophenyl]-N-(cyclopropylmethyl)-4-fluorobenzamide. CAS Registry Number: 2375110-88-4; Molecular formula: C28H17BrF12N2O2. The structural formula is as follows:

[0003] Currently, there are few reports on the detection of cyprodinil residues both domestically and internationally. The main detection method is liquid chromatography (LC), which is applied to both the technical grade pesticide and suspension concentrate. According to our research, cyprodinil is registered on cabbage and Chinese cabbage, which suggests the possibility of exceeding the limit in agricultural products on the market. Furthermore, cyprodinil is not listed in the "GB 2763-2021 National Food Safety Standard Maximum Residue Limits for Pesticides in Food," indicating a lack of relevant detection standards for cyprodinil residues in agricultural products.

[0004] We purified the matrix extract through dispersive solid-phase extraction and then used ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS / MS) to determine the residue of cyprofen in scallions. This method is simple, efficient, sensitive, and accurate, and is suitable for the detection of cyprofen residues in large quantities of scallions, providing a reference for the trace detection of cyprofen in scallions. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for determining the residue of cyprodinil in scallions based on ultra-high performance liquid chromatography-tandem mass spectrometry.

[0006] To achieve the above and other related objectives, the present invention provides the following technical solutions: A method for determining the residue of cyprodinil in scallions based on ultra-high performance liquid chromatography-tandem mass spectrometry includes the following steps: The ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS / MS) method was used to determine the sample. The detection conditions for UHPLC-MS / MS include: The liquid chromatography conditions included a flow rate of 0.25 mL / min; mobile phase A was an aqueous solution, and mobile phase B was methanol; the column oven temperature was 40℃; the injection volume was 2 μL; and the constant flow rate was 0-3 min at 80% B. Mass spectrometry conditions: Ionization source mode: ESI; Ionization source polarity: positive; Ion source temperature: 110℃; Desolvation gas temperature: 450℃; Capillary voltage: 3.5kV; Desolvation gas type and flow rate: nitrogen, 500L / Hr; Collision gas type and flow rate: argon, 0.18mL / min.

[0007] Preferably, the mass spectrometry conditions also include:

[0008] Preferably, the samples include blank scallion samples, scallion matrix solutions, standard solutions, and samples for recovery tests.

[0009] Preferably, the preparation method of the scallion matrix solution includes the following steps: Place the scallions in a centrifuge tube, add the extraction solvent, mechanically shake, add sodium chloride, vortex, centrifuge for the first time, quantitatively transfer the supernatant to a centrifuge tube containing the purification solvent, vortex, centrifuge for the second time, remove the supernatant and filter through a membrane to obtain the scallion matrix solution.

[0010] Preferably, the method for preparing the standard solution includes the following steps: Weigh out the cyclopyralid standard, dissolve it in methanol and dilute to volume to prepare a stock solution; dilute it with acetonitrile to prepare a standard working solution, and then dilute it with scallion blank sample and scallion matrix solution to prepare a series of standard solutions with concentrations of 1, 0.2, 0.1, 0.02, 0.01 and 0.002 mg / L.

[0011] Preferably, the method for preparing the scallion blank sample includes the following steps: cutting the scallion sample into small pieces less than 2 cm, mixing them thoroughly, and pulverizing them into a homogeneous paste to obtain the scallion blank sample.

[0012] More specifically, the preparation method of the scallion blank sample includes the following steps: cut the scallion sample into small pieces less than 2 cm with a stainless steel knife, mix them thoroughly in a stainless steel bowl, grind them into a homogeneous slurry using a pulverizing device, put them into a polytetrafluoroethylene self-sealing bag, affix a laboratory sample label, weigh the sample into a centrifuge tube immediately after preparation, and complete the pretreatment within 24 hours to prepare the analytical sample.

[0013] Preferably, the method for preparing the recovery test sample includes the following steps: Weigh a blank scallion sample and place it in a centrifuge tube. Add cyprodinil standard at concentrations of 0.02, 0.2, and 2 mg / kg, respectively. After adding, shake to mix thoroughly and let stand. Place the sample in a centrifuge tube, add the extraction reagent, shake mechanically, add sodium chloride, vortex, centrifuge for the first time, quantitatively transfer the supernatant to a centrifuge tube containing the purification reagent, vortex, centrifuge for the second time, and filter the supernatant through a membrane to obtain the sample for the recovery test.

[0014] Furthermore, the extraction agent includes acetonitrile.

[0015] Furthermore, the purifying agents include anhydrous magnesium sulfate, PSA, HC-C18, and GCB.

[0016] Furthermore, the parameters for the first centrifugation were 4000-6000 r / min for 4-6 min; the parameters for the second centrifugation were 10000-20000 r / min for 4-6 min.

[0017] The beneficial effects of this invention are: This invention establishes an analytical method for determining the residues of cyprodinil in scallions using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS / MS). Acetonitrile extraction was employed, followed by matrix-dispersive solid-phase extraction (MDS) purification. Separation was performed using a ZORBAX Eclipse Plus C18 UHPLC column, and determination was conducted using electrospray ionization (ESI) in positive ion mode via multiple reaction monitoring (MRM). Quantification was performed using a matrix-matched standard curve and external standard method. This establishes a method for detecting cyprodinil residues in scallions. The average recovery rate of cyprodinil in scallions was 90%-102%, with a relative standard deviation of 2.1%-7.0%. The results of the spiking recovery test indicate that the sensitivity and accuracy of this analytical method meet the requirements for spiking recovery tests in the guidelines for pesticide residue testing in crops (NY / T 788-2018). This method is simple, convenient, efficient, and accurate, and is suitable for the large-scale detection of cyprodinil residues in scallions.

[0018] More specifically, The method of this invention has high sensitivity, low detection limit, and a quantification limit as low as 0.02 mg / kg, which can meet the detection requirements for trace residues of cyclopyridamole in scallions.

[0019] The pretreatment process of this invention employs acetonitrile extraction and matrix dispersion solid-phase extraction purification, shortening the sample pretreatment time. Combined with rapid UPLC-MS / MS analysis, it is ideal for rapid screening and quantitative detection of large batches of samples.

[0020] The method of this invention has strong anti-interference ability. By systematically optimizing the extractant, purifying agent and mobile phase, and using matrix-matched standard curves for quantification, it effectively eliminates the ion inhibition or enhancement effect caused by the complex matrix of scallions, and ensures the accuracy of quantification.

[0021] This invention is the first to apply ultra-high performance liquid chromatography-tandem mass spectrometry to the detection of cyprodinil residues in the complex matrix of scallions, filling a technological gap in this specific detection field.

[0022] This invention optimizes and determines the best purification combination for scallion matrix: 60 mg anhydrous magnesium sulfate, 20 mg PSA, 20 mg HC-C18, and 10 mg GCB. This combination can effectively remove interfering substances such as pigments, organic acids, sugars, and some lipids from scallions. Existing technologies do not provide purification and extraction solutions for this specific matrix.

[0023] This invention systematically screened and established the optimal extraction solvent (acetonitrile), mobile phase system (methanol-water), and mass spectrometry monitoring ion pairs (722.3>122.7 for quantitative ion pairs, 722.3>628.9 for qualitative ion pairs), resulting in a reliable and specific detection method. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0025] In the attached diagram: Figure 1 This is the chromatogram of cyclopropionamide of the present invention.

[0026] Figure 2 This is a diagram showing the optimization of the mobile phase for cyclopropionate flufenoxuron in this invention.

[0027] Figure 3 This is the standard spectrum of the blank solvent of this invention.

[0028] Figure 4 This is the standard spectrum of the scallion matrix liquid of the present invention.

[0029] Figure 5 This is the standard spectrum of the present invention at a concentration of 0.002 mg / L. Detailed Implementation

[0030] The applicant will now describe the embodiments of the present invention in detail. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Furthermore, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized by referring to existing literature or known methods. For reactions or test conditions not listed, they are all conventional techniques readily available to those skilled in the art. The terminology used in this invention is common in the art, and its meaning will be clearly understood by those skilled in the art; therefore, it will not be elaborated upon individually.

[0031] The following information pertains to some instruments and reagents: Triple quadrupole mass spectrometry: Waters xevo TQMS, Waters; Chromatographic column: ZORBAX Eclipse Plus C18 column (2.1mm × 50mm, 1.8µm), Agilent; Formic acid (analytical grade) Sinopharm Chemical Reagent Co., Ltd.; Acetic acid (analytical grade) Sinopharm Chemical Reagent Co., Ltd.; Ammonium acetate (analytical grade) Sinopharm Chemical Reagent Co., Ltd.; Methanol (chromatographic grade) TEDIA; Acetonitrile (chromatographic grade) TEDIA; Sodium chloride (analytical grade) Jiangsu Qiangsheng Functional Chemical Co., Ltd.; N-propylethylenediamine (PSA) Shanghai Anpu Experimental Technology Co., Ltd.; Anhydrous magnesium sulfate (analytical grade) Shanghai Maclean Biochemical Technology Co., Ltd.; HC-C18 (40-63μm) Shanghai Anpu Experimental Technology Co., Ltd.; GCB (analytical grade) Nanjing Chemical Reagent Co., Ltd.; Filter membrane (0.22µm) Tianjin Jinteng Experimental Equipment Co., Ltd.

[0032] Ciprofloxacin standard (purity 99.1%).

[0033] The scallion samples were purchased from the market, and laboratory testing revealed no target compound.

[0034] Preparation steps of scallion blank sample: Cut the scallion sample into small pieces less than 2cm using a stainless steel knife, mix thoroughly in a stainless steel bowl, grind into a homogeneous slurry using a pulverizer, place in a polytetrafluoroethylene self-sealing bag, affix a laboratory sample label, and obtain the scallion blank sample. Immediately after preparation, weigh the sample into a centrifuge tube, and complete subsequent pretreatment within 24 hours to prepare the analytical sample.

[0035] Example 1 The aforementioned instruments and reagents were used to pretreat the test samples.

[0036] Extraction and purification: Accurately weigh 10.0 g of scallion sample and place it in a 50 mL centrifuge tube. Add 25 mL of acetonitrile and mechanically shake for 30 min. Add 5 g of sodium chloride, vortex for 30 s, and centrifuge at 5000 r / min for 5 min. Quantitatively transfer 1 mL of the supernatant to a 2.0 mL centrifuge tube containing 60 mg of anhydrous magnesium sulfate, 20 mg of PSA, 20 mg of HC-C18, and 10 mg of GCB (graphitized carbon black). Vortex for 30 s and centrifuge at 10000 r / min for 5 min. Absorb the supernatant and filter it through a 0.22 μm filter membrane to obtain the scallion matrix solution, which is then analyzed by liquid chromatography-tandem mass spectrometry.

[0037] Example 2 In this embodiment, chromatographic and mass spectrometric detection conditions are provided: Liquid chromatography conditions: flow rate 0.25 mL / min; mobile phase A: aqueous solution; mobile phase B: methanol; column temperature 40℃; injection volume 2 μL. Constant flow: 0-3 min 80% B. That is, isocratic elution with mobile phase B.

[0038] Mass spectrometry conditions: Ionization source mode: ESI; Ionization source polarity: positive; Ion source temperature: 110℃; Desolvation gas temperature: 450℃; Capillary voltage: 3.5kV; Desolvation gas type and flow rate: nitrogen, 500L / Hr; Collision gas type and flow rate: argon, 0.18mL / min. The retention time, parent ion, daughter ion, cone voltage, and collision energy of cyclopropion are shown in Table 1.

[0039] Table 1 Mass Spectrometry Parameters of Cyprofen

[0040] Example 3 In this embodiment, a standard solution is prepared: Accurately weigh 0.0132 g of cyprodinil standard, dissolve it in methanol and dilute to 10 mL to prepare a stock solution with a mass concentration of 1308 mg / L; dilute it with acetonitrile to prepare a standard working solution with a concentration of 10 mg / L, and then dilute it with blank solvent extracted with acetonitrile and scallion matrix solution to prepare a series of standard solutions with concentrations of 1, 0.2, 0.1, 0.02, 0.01 and 0.002 mg / L.

[0041] The blank solvent was obtained by extracting and purifying acetonitrile according to the method in Example 1. The scallion matrix solution was prepared according to Example 1.

[0042] Example 4 This embodiment provides a method for adding a recovery rate test. Weigh 10.0g of scallion blank sample into a 50mL centrifuge tube, add cyprodinil standard at concentrations of 0.02, 0.2, and 2mg / kg, respectively, shake thoroughly after addition, let stand for 30min, and then analyze the sample according to the extraction and purification steps of Example 1 and the chromatographic and mass spectrometric detection conditions of Example 2, and calculate the recovery rate and relative standard deviation.

[0043] Example 5 In this embodiment, the process of selecting UPLC-MS / MS conditions is given. The signal intensity of cyprofen was measured under ESI source positive ion and ESI source negative ion scanning modes, respectively. The ESI source positive ion mode exhibited less solvent effect and matrix interference. After optimizing parameters such as cone voltage and collision energy, 722.3 / 122.7 was selected as the quantitative ion pair, and 722.3 / 628.9 was selected as the qualitative ion pair for monitoring. The chromatogram of cyprofen is shown below. Figure 1 .

[0044] The mobile phases selected were acetonitrile-0.1% formic acid water, acetonitrile-water, acetonitrile-5 mmol / L ammonium acetate, methanol-0.1% formic acid water, methanol-water, and methanol-5 mmol / L ammonium acetate, and the same liquid phase conditions were used for the detection of cyclopropionibacterium.

[0045] The results showed that cyclopropiconazole exhibited better peak shape and higher peak response when methanol-water solution was used as the mobile phase. Therefore, methanol-water solution was ultimately chosen as the mobile phase. (See attached image) Figure 2 .

[0046] Example 6 In this embodiment, the process of selecting extraction conditions is given. Acetonitrile, 0.1% formic acid acetonitrile, and 1% formic acid acetonitrile were selected as extraction agents, and extraction was carried out under the same conditions.

[0047] The results showed that when acetonitrile was used as the extractant, the average recovery rate of cyclopropionibacterium was 93%-97%, with a relative standard deviation of 2.2%-4.4%; when 0.1% formic acid acetonitrile was used as the extractant, the average recovery rate of cyclopropionibacterium was 94%-100%, with a relative standard deviation of 2.0%-5.3%; and when 1% formic acid acetonitrile was used as the extractant, the average recovery rate of cyclopropionibacterium was 80%-96%, with a relative standard deviation of 2.8%-3.2%. The relevant recovery data when acetonitrile was used as the extractant are shown in Table 2.

[0048] Table 2. Spike recoveries and relative standard deviations of cyprodinil with different extractants

[0049] Example 7 In this embodiment, the process of selecting the purifier is given. 50 mg anhydrous magnesium sulfate and 50 mg PSA, 60 mg anhydrous magnesium sulfate, 10 mg PSA and 10 mg HC-C18, 60 mg anhydrous magnesium sulfate, 20 mg PSA, 20 mg HC-C18 and 10 mg GCB were selected as purifying agents and purified under the same conditions.

[0050] The results showed that the average recovery rate of cyclopropiconazole using 50 mg anhydrous magnesium sulfate and 50 mg PSA as purifying agents was 90%-96%, the average recovery rate using 60 mg anhydrous magnesium sulfate, 10 mg PSA and 10 mg HC-C18 as purifying agents was 92%-104%, and the average recovery rate using 60 mg anhydrous magnesium sulfate, 20 mg PSA, 20 mg HC-C18 and 10 mg GCB as purifying agents was 96%-105%. The recovery rate of cyclopropiconazole was acceptable with all three purifying agents, but the recovery rate was higher when using 60 mg anhydrous magnesium sulfate, 20 mg PSA, 20 mg HC-C18 and 10 mg GCB as purifying agents. Finally, 60 mg anhydrous magnesium sulfate, 20 mg PSA, 20 mg HC-C18 and 10 mg GCB were selected as purifying agents.

[0051] Table 3. Spiked recoveries of cyclopyralid using different purification agents

[0052] Example 8 In this embodiment, the linearity of the method is examined. The prepared series of standard solutions (1, 0.2, 0.1, 0.02, 0.01, 0.002 mg / L) were tested in ascending order of concentration, with each concentration repeated three times. A standard curve was constructed with the solution concentration as the x-axis and the corresponding peak area as the y-axis.

[0053] The results showed that within the concentration range of 0.002-1 mg / L, cyprodinil in the scallion substrate exhibited a good linear relationship with the instrument response, with a correlation coefficient R of 0.999866, meeting the requirement that the correlation coefficient of the linear regression equation of the standard curve be greater than or equal to 0.99 (NY / T 788-2018 "Guidelines for Pesticide Residue Testing in Crops"). The results are shown in Table 4.

[0054] Table 4. Linear equations and correlation coefficients of cyprodinil in shallot substrate

[0055] Example 9 In this embodiment, the recovery rate and relative standard deviation were examined. Referring to Example 4, recovery experiments were conducted at three levels in the scallion matrix, with each treatment repeated five times. The recovery results of cyprofen in the scallion matrix are shown in Table 5.

[0056] The results showed that the average recovery rate of cyclopyrrolizamide in scallion matrix was 90%-102%, with a relative standard deviation of 2.1%-7.0%, which met the requirements for pesticide residue detection.

[0057] Table 5. Recovery rate and relative standard deviation of cyprodinil in scallions

[0058] Example 10 In this embodiment, the method limit of quantitation (LOQ) is given. The limit of quantification (LOQ) of cyprofen on scallions was determined to be 0.02 mg / kg based on the addition and recovery test in Example 4.

[0059] Example 11 In this embodiment, an evaluation of the blank matrix effect is given. Solvent blanks and scallion matrix blanks were pretreated and then analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry to obtain the results. Figure 3 , 4 Figures 5 and 6 represent the standard curve spectra for the blank solvent, the onion matrix solution, and a concentration of 0.002 mg / L, respectively (the standard concentration corresponding to the 30% limit of quantitation is 0.0024 mg / L). The responses of the blank solvent and the onion matrix solution are lower than the response of the standard curve at a concentration of 0.002 mg / L, i.e., lower than the 30% limit of quantitation peak response. Therefore, it can be concluded that the interference peak responses of the blank solvent and the onion matrix solution at the target peak position both meet the requirement of not exceeding the 30% limit of quantitation peak response.

[0060] In summary, this invention establishes an analytical method for determining the residues of cyprodinil in scallions using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS / MS). Acetonitrile extraction is employed, followed by matrix-dispersive solid-phase extraction (MDPE) purification. Separation is performed using a ZORBAX Eclipse Plus C18 UHPLC column, and determination is conducted in positive ion electrospray ionization mode using multiple reaction monitoring (MRM). Quantification is achieved using a matrix-matched standard curve and external standard method. This establishes a method for detecting cyprodinil residues in scallions. The average recovery rate of cyprodinil in scallions is 90%-102%, with a relative standard deviation of 2.1%-7.0%. The results of the spiking recovery test show that the sensitivity and accuracy of this analytical method meet the requirements for spiking recovery tests in the guidelines for pesticide residue testing in crops (NY / T 788-2018). This method is simple, convenient, efficient, and accurate, and is suitable for the large-scale detection of cyprodinil residues in scallions.

[0061] Example 12 In this embodiment, the detection of field-grown scallion samples containing cyprodinil was examined. Referring to Example 4, two field scallion samples from Jiangsu Hengsheng Testing Co., Ltd. containing cyprofenoflavone were tested, and a quality control sample with an added concentration of 0.02 mg / kg was prepared.

[0062] The results showed that the average concentration of cyprodinil in scallion samples was 0.036 mg / kg, the precision was 0.28, and the average recovery rate was 98%. This method meets the requirements for detecting scallion samples that directly contain cyprodinil.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the residue of cyprodinil in shallots based on ultra-high performance liquid chromatography-tandem mass spectrometry, characterized in that, Includes the following steps: The ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS / MS) method is used to determine the sample. The detection conditions for UHPLC-MS / MS include: The liquid chromatography conditions included a flow rate of 0.25 mL / min; mobile phase A was an aqueous solution, and mobile phase B was methanol; the column oven temperature was 40℃; the injection volume was 2 μL; and the constant flow rate was 0-3 min for 80% B. Mass spectrometry conditions: Ionization source mode: ESI; Ionization source polarity: positive; Ion source temperature: 110℃; Desolvation gas temperature: 450℃; Capillary voltage: 3.5kV; Desolvation gas type and flow rate: nitrogen, 500L / Hr; Collision gas type and flow rate: argon, 0.18mL / min.

2. The method for determining the residue of cyprodinil in scallions based on ultra-high performance liquid chromatography-tandem mass spectrometry according to claim 1, characterized in that, Mass spectrometry conditions also include:

3. The method for determining the residue of cyprodinil in scallions based on ultra-high performance liquid chromatography-tandem mass spectrometry according to claim 1, characterized in that, The samples included blank scallion samples, scallion matrix solution, standard solution, and samples for recovery testing.

4. The method for determining the residue of cyprodinil in scallions using ultra-high performance liquid chromatography-tandem mass spectrometry according to claim 3, characterized in that, The preparation method of scallion matrix solution includes the following steps: Place the scallions in a centrifuge tube, add the extraction solvent, mechanically shake, add sodium chloride, vortex, centrifuge for the first time, quantitatively transfer the supernatant to a centrifuge tube containing the purification solvent, vortex, centrifuge for the second time, remove the supernatant and filter through a membrane to obtain the scallion matrix solution.

5. The method for determining the residue of cyprodinil in scallions using ultra-high performance liquid chromatography-tandem mass spectrometry according to claim 3, characterized in that, The preparation method of standard solutions includes the following steps: Weigh out the cyclopyralid standard, dissolve it in methanol and dilute to volume to prepare a stock solution; dilute it with acetonitrile to prepare a standard working solution, and then dilute it with scallion blank sample and scallion matrix solution to prepare a series of standard solutions with concentrations of 1, 0.2, 0.1, 0.02, 0.01 and 0.002 mg / L.

6. The method for determining the residue of cyprodinil in scallions using ultra-high performance liquid chromatography-tandem mass spectrometry according to claim 3, characterized in that, The preparation method of the scallion blank sample includes the following steps: cut the scallion sample into small pieces less than 2 cm, mix them thoroughly, and crush them into a homogenous paste to obtain the scallion blank sample.

7. The method for determining the residue of cyprodinil in scallions using ultra-high performance liquid chromatography-tandem mass spectrometry according to claim 3, characterized in that, The preparation method for samples used in recovery tests includes the following steps: Weigh a blank scallion sample and place it in a centrifuge tube. Add cyprodinil standard at concentrations of 0.02, 0.2, and 2 mg / kg, respectively. After adding, shake to mix thoroughly and let stand. Place the sample in a centrifuge tube, add the extraction reagent, shake mechanically, add sodium chloride, vortex, centrifuge for the first time, quantitatively transfer the supernatant to a centrifuge tube containing the purification reagent, vortex, centrifuge for the second time, and filter the supernatant through a membrane to obtain the sample for the recovery test.

8. The method for determining the residue of cyprodinil in scallions using ultra-high performance liquid chromatography-tandem mass spectrometry according to claim 4 or 7, characterized in that, The extractant includes acetonitrile.

9. The method for determining the residue of cyprodinil in shallots based on ultra-high performance liquid chromatography-tandem mass spectrometry according to claim 4 or 7, characterized in that, The purifying agents include anhydrous magnesium sulfate, PSA, HC-C18, and GCB.

10. The method for determining the residue of cyprodinil in scallions using ultra-high performance liquid chromatography-tandem mass spectrometry according to claim 4 or 7, characterized in that, The parameters for the first centrifugation were 4000-6000 r / min for 4-6 min; the parameters for the second centrifugation were 10000-20000 r / min for 4-6 min.

Images