Method for detecting chlormequat chloride and mepiquat chloride in cereal grains based on modified porous material

Abstract

The invention provides a method for detecting chlormequat chloride and mepiquat chloride in cereal grains based on a modified porous material, and relates to the technical field of food safety inspection. The detection method comprises the following steps: preparing a standard solution with gradient concentration by adopting a standard substance of a pesticide to be detected, and carrying out ultra-high performance liquid chromatography-quadrupole tandem mass spectrometry detection to obtain a standard curve of the pesticide to be detected; the method comprises the following steps: extracting to-be-detected cereal grains by using an acetonitrile solution of formic acid, passing an extracting solution through a solid-phase extraction column to obtain a to-be-detected solution, determining the to-be-detected solution by using an ultra-high performance liquid chromatography-quadrupole tandem mass spectrometer, and obtaining the residual quantity of pesticides (chlormequat chloride and mepiquat chloride) in the to-be-detected cereal grains according to an external standard curve method. Compared with an existing detection method, the detection method has the advantages that the detection time is greatly shortened, solvent conversion and purification processes are omitted in the whole pretreatment process, the recovery rate is stable, and the reliability is high.

Description

Technical Field

[0001] The present invention relates to the technical field of food safety inspection, and particularly relates to a method for detecting chlormequat and mepiquat in grain based on modified porous materials. Background Art

[0002] Chlormequat (CQ) and mepiquat (also known as mepiquat chloride, MQ) are two widely used quaternary ammonium salt (quaternary-N) plant growth regulators. They can increase the ability of plants to resist disasters by inhibiting excessive plant growth, thereby increasing agricultural product yields. Both of these compounds are strongly alkaline polar cationic compounds. Such compounds are soluble in water and not volatile, and are likely to leave residues in the environment and migrate into the human body through the food chain. Since grain agricultural products have a long growth cycle, most of the pesticide residues in grains enter the internal tissues through pathways such as root absorption and conduction. Pesticides remaining on crops can enter the bodies of humans and livestock through the food chain, posing a serious threat to the health and life safety of humans and livestock. The maximum residue limits of pesticides in food (GB2763-2021) stipulate that the maximum residue limit of chlormequat in grains is 2-10 mg / kg, and that of mepiquat is 0.5 mg / kg. Therefore, it is of great significance to establish a detection technology for pesticide residues of chlormequat and mepiquat in grains.

[0003] The detection of quaternary ammonium salt pesticides in grains has always been a difficult point in the analysis field. With the continuous development of detection technologies, liquid chromatography-tandem mass spectrometry is currently often used to analyze such pesticides in grains. However, the residues of quaternary ammonium salt pesticides in grains are mostly trace or microscale, and the matrix contains a large amount of starch, oil, etc., which further increases the difficulty of analysis. Coupled with the increasing requirements for the detection cycle, rapid and sufficient purification of samples before instrumental analysis has become an exploration direction for many researchers in the detection of such pesticides. Those skilled in the art urgently need to develop a detection method with a short detection cycle, high accuracy, and capable of purifying starch, oil, and protein in grains for detecting the contents of chlormequat and mepiquat in grains. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for detecting chlormequat and mepiquat in grains based on modified porous materials to solve the problem that a large amount of starch and oil in the grain matrix is not conducive to the quantitative detection of quaternary ammonium salt pesticides therein.

[0005] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for detecting chlormequat and mepiquat in grains based on modified porous materials, comprising the following steps:

[0007] 1) Prepare standard solutions with gradient concentrations using the reference substance of the pesticide to be detected;

[0008] 2) Perform ultra-high performance liquid chromatography - triple quadrupole mass spectrometry detection on the standard solutions with gradient concentrations prepared in step 1) to obtain the standard curve of the pesticide to be detected;

[0009] 3) Take the grain to be tested, crush and sieve it, mix it with an acetonitrile solution of formic acid, and then perform homogenization, centrifugation, and solid-phase extraction column treatment in sequence to obtain the extract of the sample to be tested;

[0010] 4) Use an ultra-high performance liquid chromatography - triple quadrupole mass spectrometer to measure the extract of the sample to be tested, and obtain the pesticide residue in the grain to be tested according to the external standard curve method; the pesticides to be detected are chlormequat chloride and / or mepiquat chloride;

[0011] Among them, the solid-phase extraction column in step 3) is an SPE column loaded with adsorbent MPD-HCP.

[0012] Preferably, the measurement conditions of the ultra-high performance liquid chromatography - triple quadrupole mass spectrometer in step 2) and step 4) are as follows:

[0013] Ultra-high performance liquid chromatography: The chromatographic column is Waters ACQUITY UPLC BEH Amide, with parameters of 2.1 mm × 100 mm, 1.7 μm; the mobile phase is an aqueous solution of formic acid - acetonitrile, the flow rate is 0.4 mL / min; the column temperature is 35 °C; the injection volume is 5 μL;

[0014] Mass spectrometer: Electrospray ionization source ESI, multiple reaction monitoring mode, electrospray voltage is 5500 V, curtain gas pressure is 35 psi, ion source temperature is 550 °C, nebulizing gas pressure is 60 psi, auxiliary gas pressure is 50 psi, declustering voltage is 40 V, collision cell entrance voltage is 10 V, collision cell exit voltage is 11 V.

[0015] Preferably, the concentration of the pesticide to be detected in the standard solutions with gradient concentrations is 0.5 - 200 ng / mL.

[0016] Preferably, the concentration of formic acid in the acetonitrile solution of formic acid in step 3) is 0.5%.

[0017] Preferably, the preparation method of the adsorbent MPD-HCP is: Mix m-phenylenediamine, dimethoxymethane, 1,2-dichloroethane, and aluminum chloride, and then perform a two-stage heating reaction to obtain the adsorbent MPD-HCP.

[0018] Preferably, the mixing ratio of m-phenylenediamine, dimethoxymethane, 1,2-dichloroethane, and aluminum chloride is 2 - 2.1 mmol: 2 - 2.1 mmol: 30 - 32 mL: 6 - 6.2 mmol.

[0019] Preferably, the temperature of the first-stage heating reaction in the two-stage heating reaction is 80-83 °C, and the time is 5-5.5 h;

[0020] The temperature of the second-stage heating reaction in the two-stage heating reaction is 120-123 °C, and the time is 24-25 h.

[0021] The present invention has at least the following beneficial effects:

[0022] The present invention uses a solid-phase extraction column filled with adsorbent MPD-HCP to treat the grain extract. The surface of this column has a large number of positive charges and has no adsorption for quaternary ammonium salt pesticides with positive charges on the same surface. The target compounds can pass through quickly. Fats, proteins, and a large amount of starch in the grain matrix are retained in the solid-phase extraction column. This purification method is simple and convenient, eliminating solvent conversion in the entire pretreatment process, and the recovery rate is stable during the purification process. For the sample purified by the solid-phase extraction column filled with MPD-HCP of the present invention, the matrix components are significantly reduced, which can effectively reduce the pollution of the chromatographic column and the instrument, and make the detection results of chlormequat chloride and mepiquat chloride more accurate. Description of the Drawings

[0023] Figure 1 SEM micrograph of the adsorbent MPD-HCP prepared in Example 1;

[0024] Figure 2 Photos before and after purifying the grain leaching solution to be measured with an extraction column containing adsorbent MPD-HCP;

[0025] Figure 3 Curve of the change in recovery rate when different grains are soaked and extracted with different solvents;

[0026] Figure 4 Total ion current chromatogram of the grain leaching solution without purification by the extraction column in Example X;

[0027] Figure 5 Total ion current chromatogram of the grain leaching solution purified by the extraction column in Example X;

[0028] Figure 6 Statistical chart of matrix effects of chlormequat chloride and mepiquat chloride in different matrices;

[0029] Figure 7 MRM chromatogram of chlormequat chloride and mepiquat chloride in corn matrix detected by Waters ACQUITY UPLC BEH Amide chromatographic column. Detailed Description of the Invention

[0030] The present invention provides a method for detecting chlormequat chloride and mepiquat chloride in grain based on a modified porous material, comprising the following steps:

[0031] 1) Prepare standard solutions with gradient concentrations using standard substances of the pesticides to be detected;

[0032] 2) Perform ultra-high performance liquid chromatography - triple quadrupole mass spectrometry detection on the standard solutions with gradient concentrations prepared in step 1) to obtain the standard curves of the pesticides to be detected;

[0033] 3) Take the grain to be tested, crush and sieve it, mix it with an acetonitrile solution of formic acid, and then perform homogenization, centrifugation, and solid-phase extraction column treatment in sequence to obtain an extract of the sample to be tested;

[0034] 4) Use an ultra-high performance liquid chromatography - triple quadrupole mass spectrometer to measure the extract of the sample to be tested, and obtain the pesticide residue content in the grain to be tested according to the external standard curve method; the pesticides to be detected are chlormequat chloride and / or mepiquat chloride;

[0035] Among them, the solid-phase extraction column in step 3) is an SPE column loaded with the adsorbent MPD-HCP.

[0036] In the present invention, the measurement conditions of the ultra-high performance liquid chromatography - triple quadrupole mass spectrometer in step 2) and step 4) are as follows:

[0037] Ultra-high performance liquid chromatography: The chromatographic column is Waters ACQUITY UPLC BEH Amide, with parameters of 2.1 mm × 100 mm, 1.7 μm; the mobile phase is an aqueous solution of formic acid - acetonitrile, the flow rate is 0.4 mL / min; the column temperature is 35 °C; the injection volume is 5 μL;

[0038] Mass spectrometer: Electrospray ionization source ESI, multiple reaction monitoring mode, electrospray voltage is 5500 V, curtain gas pressure is 35 psi, ion source temperature is 550 °C, nebulizing gas pressure is 60 psi, auxiliary gas pressure is 50 psi, declustering voltage is 40 V, collision cell entrance voltage is 10 V, collision cell exit voltage is 11 V.

[0039] In the present invention, the concentration of the pesticide to be detected in the standard solution with gradient concentrations is 0.5 - 200 ng / mL

[0040] In the present invention, the concentration of formic acid in the acetonitrile solution of formic acid in step 3) is 0.5%.

[0041] In the present invention, the preparation method of the adsorbent MPD-HCP is: Mix m-phenylenediamine, dimethoxymethane, 1,2-dichloroethane, and aluminum chloride, and then perform a two-stage heating reaction to obtain the adsorbent MPD-HCP.

[0042] In the present invention, the mixing ratio of m-phenylenediamine, dimethoxymethane, 1,2-dichloroethane and aluminum chloride is 2 - 2.1 mmol : 2 - 2.1 mmol : 30 - 32 mL : 6 - 6.2 mmol, preferably 2.02 - 2.08 mmol : 2.02 - 2.08 mmol : 30.5 - 31.5 mL : 6.05 - 6.15 mmol, and further preferably 2.05 mmol : 2.05 mmol : 31 mL : 6.1 mmol.

[0043] In the present invention, for the first-stage heating reaction in the two-stage heating reaction, the temperature is 80 - 83°C, preferably 81 - 82°C; the time is 5 - 5.5 h, preferably 5.1 - 5.4 h, and further preferably 5.2 - 5.3 h;

[0044] for the second-stage heating reaction in the two-stage heating reaction, the temperature is 120 - 123°C, preferably 121 - 122°C; the time is 24 - 25 h, preferably 24.25 - 24.75 h, and further preferably 24.5 h.

[0045] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0046] Example 1

[0047] (1) Preparation of the solid-phase extraction column:

[0048] Add m-phenylenediamine (MPD, 2 mmol), dimethoxymethane (FDA, 2 mmol) and 1,2-dichloroethane (DCE, 30 mL) to a 100 mL round-bottom flask. After ultrasonic dissolution for 5 min, add anhydrous aluminum chloride (AlCl3, 6 mmol) thereto. The mixture is heated under reflux in an oil bath to 80°C for reaction for 5 h, and then the temperature is raised to 120°C for reaction for 24 h to obtain a brownish-black solid. The brownish-black solid is washed three times with methanol and water. Finally, the obtained solid is placed in a Soxhlet extractor and extracted with methanol for 24 h, and then dried in a vacuum drying oven at 80°C for 12 h to obtain a pure adsorbent MPD-HCP. Finally, 20 mg of the adsorbent is loaded into an empty SPE column (with a volume of 3 mL) and fixed with upper and lower sieve plates to obtain the solid-phase extraction column. Figure 1 is the scanning electron microscope micrograph of the adsorbent MPD-HCP. As can be seen from Figure 1 it that MPD-HCP presents a spherical shape. The spherical material can ensure its tight packing performance and low surface energy, which is beneficial to its application in adsorption.

[0049] (2) Preparation of the mixed standard solution:

[0050] Weigh 100 μL each of the standard samples of two compounds, chlormequat chloride and mepiquat chloride (both purchased from Tianjin Aladdin Chemistry Co., Ltd., namely, a solution of chlormequat chloride with a concentration of 100 μg / mL and a solution of mepiquat chloride with a concentration of 100 μg / mL) into a 10 mL brown volumetric flask, and make up the volume with methanol-water (1:1, V / V) to obtain a mixed standard intermediate solution with a concentration of 1 μg / mL. (This mixed standard intermediate solution should be stored in the dark at 4 °C and has a validity period of 1 month). Accurately pipette the mixed standard intermediate solution and dilute it with a 0.5% formic acid-acetonitrile extraction solution to obtain a mixed standard solution with gradient concentrations of 0.5 ng / mL, 1 ng / mL, 5 ng / mL, 20 ng / mL, 50 ng / mL, 100 ng / mL, and 200 ng / mL for chlormequat chloride and mepiquat chloride with independent concentrations.

[0051] (3) Use an ultra-high performance liquid chromatography-quadrupole tandem mass spectrometer to sequentially measure the mixed standard solutions with gradient concentrations prepared in step (2). Take the peak area of the target substance as the ordinate (y) and the concentration of the measured component as the abscissa (x, ng / mL) to make a linear regression curve, and determine the detection limit (LOD) and quantification limit (LOQ) with a signal-to-noise ratio S / N≥3 and S / N≥10. The linear range, equation, correlation coefficient, detection limit, and quantification limit of the analyte are shown in Table 1.

[0052] Table 1 Linear range, equation, correlation coefficient, detection limit, and quantification limit of the analyte

[0053]

[0054] (4) Sample treatment

[0055] Weigh 5 g (accurate to 0.01 g) of a homogeneous sample (corn, crushed and passed through a standard sieve with a pore size of 425 μm, and stored in a polyethylene sealed bag), place it in a 50 mL centrifuge tube, add 20 mL of 0.5% formic acid-acetonitrile extraction solution, homogenize at high speed for 1 min, and then centrifuge at 8000 r / min for 5 min. Take an appropriate amount of the supernatant and pass it through a self-made solid-phase extraction column, and collect 1 mL of the effluent and pass it through a 0.22 μm organic filter membrane to obtain the test solution. Figure 2 are photos of the test solution before and after passing through the solid-phase extraction column. It can be seen from Figure 2 that the color of the solution in the injection vial becomes significantly lighter after purification. Use an ultra-high performance liquid chromatography-quadrupole tandem mass spectrometer to measure the test solution.

[0056] The parameters of the ultra-high performance liquid chromatography-quadrupole tandem mass spectrometer in steps (3) and (4) are as follows:

[0057] Ultra-high performance liquid chromatography conditions: Waters ACQUITY UPLC BEH Amide column (2.1 mm × 100 mm, 1.7 μm); mobile phase: aqueous solution containing 0.1% formic acid (A) and acetonitrile (B); flow rate: 0.4 mL / min; column temperature: 35 °C; injection volume: 5 μL; gradient elution program: 0 - 1.0 min, 90% B; 1.0 - 3.0 min, 90% - 40% B; 3.0 - 5.0 min, 40% B; 5.0 - 5.1 min, 40% - 90% B; 5.1 - 7.0 min, 90% B.

[0058] Mass spectrometry conditions: electrospray ionization source ESI(+), operating in multiple reaction monitoring (MRM) mode. Electrospray voltage (IS): 5500 V; curtain gas pressure (CUR): 35 psi; ion source temperature: 550 °C; nebulizing gas pressure (GS1): 60 psi; auxiliary gas pressure (GS2): 50 psi; declustering potential (DP): 40 V; entrance potential of the collision cell (EP): 10 V; exit potential of the collision cell (CXP): 11 V. The mass spectrometry analysis parameters of chlormequat chloride and mepiquat chloride are shown in Table 2.

[0059] Table 2 Mass spectrometry analysis parameters of chlormequat chloride and mepiquat chloride

[0060]

[0061] It can be seen from Table 2 that the m / z values of the product ions of chlormequat chloride and mepiquat chloride are relatively small, and they are easily interfered by the matrix.

[0062] Example 2

[0063] Steps (1) - (3) are the same as those in Example 1

[0064] (4) Blank matrix samples of rice, wheat, corn, and soybeans (i.e., samples without analytes to be measured) were selected, crushed, and passed through a standard sieve with a pore size of 425 μm (the degree of crushing was based on all particles passing through the sieve). A total of 4 mass concentrations of mixed standard solutions equivalent to 2 μg / kg, 4 μg / kg, 20 μg / kg, and 100 μg / kg were added (10 μL, 20 μL, 100 μL, and 500 μL of the mixed standard solution with a concentration of 1 μg / mL were added respectively). After mixing evenly, spiked samples were obtained. Then, 5 g (accurate to 0.01 g) of the homogeneous sample was taken and placed in a 50 mL centrifuge tube. 20 mL of 0.5% formic acid - acetonitrile extraction solution was added, and it was homogenized at high speed for 1 min, and then centrifuged at 8000 r / min for 5 min. An appropriate amount of the supernatant was taken and placed on a self-made through - type solid - phase extraction column. 1 mL of the effluent was collected and passed through a 0.22 μm organic filter membrane to obtain the test solution. The test solution was detected (the instrument parameters during detection were the same as in Example 1), and a spiked recovery experiment was carried out. Each level was measured 6 times. The accuracy of the method was determined by calculating the recovery rate, and the precision of the method was evaluated by the relative standard deviation (RSD) of the calculation results. The recovery rate and relative standard deviation are shown in Table 3. As can be seen from Table 3, the recovery rate of this method is 75.6% - 108.0%, and the relative standard deviation (RSD) is 2.9% - 8.5%. Its accuracy and recovery rate both meet the experimental requirements.

[0065] Table 3 Spiked recovery rate and relative standard deviation of this detection method

[0066]

[0067]

[0068] The matrix effect (ME) of this method was investigated using blank matrices of rice, wheat, corn, and soybeans. A series of concentration solutions were prepared using 4 kinds of matrix blank solutions and acetonitrile - 0.5% formic acid (1:1, V / V) as solvents respectively. The calculation formula for ME is ME(%) = A / B * 100%. Among them, A and B are the slopes of the grain matrix solution curve and the solvent solution curve respectively. When ME is 80% - 120%, it indicates that the matrix effect is not obvious and can be ignored. When ME > 120% or ME < 80%, it indicates the presence of enhanced or inhibited matrix effect. The matrix effects of the 2 compounds in this study are shown in Figure 6 . The matrix effect of chlormequat is between 61% and 89%, and the matrix effect of mepiquat chloride is between 63% and 93%. To eliminate the interference of the matrix effect, standard solutions with the same matrix were used for calibration.

[0069] Comparative Example 1

[0070] According to the content recorded in "Determination of chlormequat residue in grain and cereal - GB / T 5009.219 - 2008", a neutral alumina solid - phase extraction column combined with a gas chromatography - mass spectrometry (GC - MS) was used to detect the samples.

[0071] Comparative Example 2

[0072] According to the content recorded in "Determination of chlormequat and mepiquat residues in foods by high performance liquid chromatography - tandem mass spectrometry" (Lü Liliang, Luo Xiaoling, Wang Yuan, et al. Journal of Instrumental Analysis, 2011, 30(3): 321 - 325.), a Strata - X - C solid - phase extraction column combined with an ultra - high performance liquid chromatography - quadrupole tandem mass spectrometer was used to detect the samples.

[0073] Comparative Example 3

[0074] According to the content recorded in "Janice Z. Francesquett, Tiele M. Rizzetti, Tito R. S. Cadaval, et al. Simultaneous determination of the quaternary ammonium pesticides paraquat, diquat, chlormequat, and mepiquat in barley and wheat using a modified quick polar pesticides method, diluted standard addition calibration and hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry", a modified QuPPe method with chitosan introduced, combined with an ultra - high performance liquid chromatography - quadrupole tandem mass spectrometer was used to detect the samples.

[0075] The comparison results of the detection methods described in Example 1 and Comparative Examples 1 - 3 are shown in Table 4.

[0076] Table 4 Comparison results of the detection methods described in Example 1 and Comparative Examples 1 - 3

[0077]

[0078] From the data recorded in Table 4, it can be seen that the self-made MPD-HCP solid-phase extraction column is adopted in this method, and the detection can be completed within 15 minutes. The recovery rates are comparable to those of other methods such as GB / T 5009.219-2008, but this method takes less time, and the pretreatment process is simple and easy to operate, which can meet the analysis requirements of chlormequat chloride and mepiquat chloride in grain and cereal.

[0079] Comparative Example 4

[0080] 100 μL of the mixed standard solution with a concentration of 1 μg / mL was added to the rice and corn matrices respectively to obtain the simulated analytes to be detected with an added level of 20 μg / kg.

[0081] The above-mentioned simulated analytes to be detected were detected with reference to the detection method in Example 1. During the detection process, different concentrations of formic acid solution were mixed with acetonitrile to soak and extract the samples. Formic acid solutions with concentrations of 0.1%, 0.2%, 0.5%, 0.7%, and 1% were mixed with acetonitrile (the ratio of formic acid solution to acetonitrile was 1:1), and then the samples were soaked and extracted to prepare the solutions to be detected; the extraction solvents with the mixing ratios of formic acid solution (concentration of 0.5%) to acetonitrile of 9:1, 7:3, 1:1, 3:7, and 1:9 were used to soak and extract the samples to prepare the solutions to be detected. The above-mentioned solutions to be detected were determined with the instrument parameters in Example 1, and the detection results and recovery rates are as Figure 3 shown. It can be seen from Figure 3 that both the concentration of formic acid solution and the amount of acetonitrile used have an impact on the extraction efficiency. The recovery rates of chlormequat chloride and mepiquat chloride increase with the increase in the concentration of formic acid solution, and chlormequat chloride has a more obvious change trend than mepiquat chloride. When the formic acid concentration is 0.5%, the recovery rates of both tend to be stable. The recovery rates of chlormequat chloride and mepiquat chloride are between 70% and 80% when the acetonitrile is 10%, but too many impurity matrix effects are extracted and the compound response is inhibited. When the acetonitrile ratio is increased to 50%, the compound recovery rate and response value are both good. When the acetonitrile ratio is 70%, the extraction efficiency of both starts to decrease, and when the ratio is 90%, the recovery rates of chlormequat chloride and mepiquat chloride are only about 60%.

[0082] Comparative Example 5

[0083] The difference from Example 1 is only that the step of purifying the sample extract with an extraction column is omitted and the test is carried out directly. The total ion chromatogram of the sample is as Figure 5 shown (the scanning range is 50 Da - 800 Da).

[0084] The total ion chromatogram of the sample after purification with the extraction column in Example 1 is as Figure 6 shown (the scanning range is 50 Da - 800 Da).

[0085] By comparing Figure 5And Figure 6 It can be seen that for the corn samples purified by the self-made MPD-HCP solid-phase extraction column, estimated by the intensity of the matrix components, the matrix components are significantly reduced, which can effectively reduce the contamination of the chromatographic column and the instrument, and make the detection results of chlormequat chloride and mepiquat chloride more accurate.

[0086] Comparative Example 6

[0087] The difference from Example 1 is only that the chromatographic columns used in ultra-high performance liquid chromatography are different. The Waters ACQUITY UPLC HSS T3 chromatographic column (2.1 mm × 100 mm, 1.8 μm), Waters ACQUITY UPLC Cortecs HILIC chromatographic column (2.1 mm × 100 mm, 1.6 μm), and Waters ACQUITY UPLC BEH Amide chromatographic column (2.1 mm × 100 mm, 1.7 μm) are respectively used to detect chlormequat chloride and mepiquat chloride in corn. The retention of chlormequat chloride and mepiquat chloride on the T3 chromatographic column is still weak and the peak appears at about 1 min; when using the BEH Amide column, 0.1% formic acid-acetonitrile is selected as the mobile phase, and the response values of chlormequat chloride and mepiquat chloride are about 20% higher than those of the HILIC chromatographic column, and the peak shape is sharp. Figure 7 Figure 10 is the chromatogram of chlormequat chloride and mepiquat chloride on Waters ACQUITY UPLC BEH Amide. It can be seen from the figure that the peak shapes of chlormequat chloride and mepiquat chloride are sharp and symmetrical, without background interference.

[0088] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for detecting chlormequat chloride and mepiquat chloride in grain based on modified porous materials, characterized in that, It includes the following steps: 1) Prepare standard solutions with gradient concentrations using the reference substance of the pesticide to be detected; 2) Perform ultra-high performance liquid chromatography - triple quadrupole mass spectrometry detection on the standard solutions with gradient concentrations prepared in step 1) to obtain the standard curve of the pesticide to be detected; 3) Take the grain to be tested, crush and sieve it, mix it with an acetonitrile solution of formic acid, and then perform homogenization, centrifugation, and solid-phase extraction column treatment in sequence to obtain the extract of the sample to be tested; 4) Use an ultra-high performance liquid chromatography - triple quadrupole mass spectrometer to measure the extract of the sample to be tested, and obtain the pesticide residue in the grain to be tested according to the external standard curve method; the pesticides to be detected are chlormequat chloride and / or mepiquat chloride; Wherein, the solid-phase extraction columns in step 2) and step 3) are independently SPE columns loaded with the adsorbent MPD-HCP.

2. The method for detecting chlormequat chloride and mepiquat chloride in grain based on modified porous materials according to claim 1, characterized in that, The measurement conditions of the ultra-high performance liquid chromatography - triple quadrupole mass spectrometer in step 2) and step 4) are as follows: Ultra-high performance liquid chromatography: The chromatographic column is Waters ACQUITY UPLC BEH Amide, with parameters of 2.1 mm × 100 mm, 1.7 μm; the mobile phase is an aqueous solution of formic acid - acetonitrile, the flow rate is 0.4 mL / min; the column temperature is 35 °C; the injection volume is 5 μL; Mass spectrometer: Electrospray ionization source ESI, multiple reaction monitoring mode, electrospray voltage is 5500 V, curtain gas pressure is 35 psi, ion source temperature is 550 °C, nebulizing gas pressure is 60 psi, auxiliary gas pressure is 50 psi, declustering voltage is 40 V, collision cell entrance voltage is 10 V, collision cell exit voltage is 11 V.

3. A method for detecting chlormequat chloride and mepiquat chloride in grain based on a modified porous material according to claim 2, characterized in that, The concentration of the pesticide to be detected in the standard solution with gradient concentrations is 0.5 - 200 ng / mL.

4. The method for detecting chlormequat chloride and mepiquat chloride in grain based on a modified porous material according to claim 3, wherein, In the acetonitrile solution of formic acid in step 3), the volume concentration of formic acid is 0.5%; The particle size of the crushed grain to be tested is ≤ 425 μm.

5. A method for detecting chlormequat chloride and mepiquat chloride in grain based on a modified porous material according to any one of claims 1 to 4, characterized in that, The preparation method of the adsorbent MPD-HCP is: mix m-phenylenediamine, dimethoxymethane, 1,2-dichloroethane, and aluminum chloride, and then perform a two-stage heating reaction to obtain the adsorbent MPD-HCP.

6. A method for detecting chlormequat chloride and mepiquat chloride in grain based on a modified porous material according to claim 5, wherein, The mixing ratio of m-phenylenediamine, dimethoxymethane, 1,2-dichloroethane, and aluminum chloride is 2 - 2.1 mmol: 2 - 2.1 mmol: 30 - 32 mL: 6 - 6.2 mmol.

7. A method for detecting chlormequat chloride and mepiquat chloride in grain based on a modified porous material according to claim 6, characterized in that, In the two-stage heating reaction, the temperature of the first-stage heating reaction is 80 - 83 °C, and the time is 5 - 5.5 h; In the two-stage heating reaction, the temperature of the second-stage heating reaction is 120 - 123 °C, and the time is 24 - 25 h.

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