Method for detecting residual quantity of ethiprole and metabolite thereof in eggplant

Abstract

The invention provides a method for detecting ethiprole and metabolite residues of ethiprole in eggplants, and belongs to the technical field of pesticide residue detection. The method comprises the following steps: adding acetonitrile into a crushed eggplant sample, carrying out ultrasonic extraction, adding sodium chloride, mixing, and carrying out centrifugal separation to obtain an extracting solution; adding N-propylethylenediamine and anhydrous magnesium sulfate into the extracting solution, mixing, standing, and filtering to obtain a to-be-detected solution; and detecting the liquid to be detected by adopting high performance liquid chromatography-tandem mass spectrometry. According to the method, a dispersive solid-phase extraction pretreatment technology is combined with a high-performance liquid-phase tandem mass spectrometry detection technology, so that the ethiprole and metabolite residues thereof in the eggplant can be rapidly detected. The average recovery rate of the ethiprole and the metabolite of the ethiprole is 78%-96%, the relative standard deviation (RSD) is 2.5%-5.3%, the detection limit is 0.002 mg / kg, and the quantification limit is 0.01 mg / kg.

Description

Technical Field

[0001] The invention relates to the technical field of pesticide residue detection, and in particular to a method for detecting the residues of ethiprole and its metabolites in eggplant. Background Art

[0002] Ethiopromide is a phenylpyrazole insecticide. Its mechanism of action is to interfere with the chloride ion channel by inhibiting the influx of chloride ions, thus destroying the normal activity of the central nervous system (CMS), causing insects to become overexcited and die. This drug mainly kills insects by contact, has a broad spectrum of insecticides, and has significant effects. It is widely used in vegetable crops. Therefore, it is particularly important to establish a method for determining the residues of ethiprole in vegetables.

[0003] At present, there are only reports on the detection method of ethiprole in rice in China. The instrument used is gas chromatography (ECD), the retention time is more than 15min, and the detection limit is high. Solid phase extraction is used for purification, and the pre-treatment is complicated and more solvents are used. At present, there is no detection method for ethiprole metabolites ethiprole sulfone and ethiprole amide in China. Therefore, it is very necessary to invent a rapid and efficient method for determining the residue analysis of ethiprole and its metabolites in eggplant, which is intended to provide technical support for the residue registration test of ethiprole on eggplant, and also provide a method reference for the screening of pesticide residues such as ethiprole in vegetables such as eggplant. Summary of the invention

[0004] The object of the present invention is to provide a method for detecting the residual amount of ethiprole and its metabolites in eggplant, so as to solve the problem that the ethiprole metabolites ethiprole sulfone and ethiprole amide cannot be detected in the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for detecting the residual amount of ethidium bromide and its metabolites in eggplant, comprising the following steps:

[0007] S1: Add acetonitrile to the crushed eggplant sample for ultrasonic extraction, then add sodium chloride, mix and centrifuge to obtain an extract;

[0008] S2: Add N-propylethylenediamine and anhydrous magnesium sulfate to the extract, mix, let stand, and filter to obtain a test solution;

[0009] S3: Detecting the test solution by high performance liquid chromatography tandem mass spectrometry;

[0010] The HPLC column is a T3 column with gradient elution.

[0011] Mobile phase: Mobile phase A is 0.1% formic acid aqueous solution containing 5 mmol ammonium acetate, and mobile phase B is acetonitrile;

[0012] The gradient elution of the high performance liquid chromatography comprises:

[0013] 0-0.3min, the volume fraction of mobile phase A is 80%, and the volume fraction of mobile phase B is 20%;

[0014] 0.3-1.5min, the volume fraction of mobile phase A changes from 80% to 30%, and the volume fraction of mobile phase B changes from 20% to 70%;

[0015] 1.5-3.2 min, the volume fraction of mobile phase A is 30%, and the volume fraction of mobile phase B is 70%;

[0016] 3.2-3.5 min, the volume fraction of mobile phase A changes from 30% to 80%, and the volume fraction of mobile phase B changes from 70% to 20%;

[0017] 3.5~5.0min, the volume fraction of mobile phase A is 80%, and the volume fraction of mobile phase B is 20%.

[0018] Preferably, in step S1, the mass ratio of the eggplant sample to the volume of acetonitrile is 10 g:20 mL; the time of the ultrasonic extraction is 5 to 15 min; and the mass ratio of the eggplant sample to sodium chloride is 10:4 to 8.

[0019] Preferably, in step S2, the usage ratio of the extract, N-propylethylenediamine and anhydrous magnesium sulfate is 2 mL: 80-120 mg: 130-170 mg.

[0020] Preferably, the chromatographic column of the high performance liquid chromatography is: HSS T32.1×100mm 1.8μm, the column temperature is 40℃, the flow rate is 0.4mL / min, and the injection volume is 5μL.

[0021] Preferably, the main parameters of the mass spectrometer include:

[0022] The ion source was an electrospray ion source (ESI), and the scanning mode was: positive ion scanning for ethiprole and ethiprole amide, and negative ion scanning for ethiprole sulfone;

[0023] Ion source parameters: curtain gas (nitrogen): 30 psi, ion source gas 1 (nitrogen): 55 psi, ion source gas 2 (nitrogen): 55 psi;

[0024] Ion source voltage: 4500 V in positive ion mode, -4500 V in negative ion mode;

[0025] Ion source temperature: 450°C;

[0026] The detection method was multiple reaction monitoring (MRM).

[0027] Preferably, the mass spectrometry parameters of ethiprole, ethiprole sulfone and ethiprole amide are:

[0028] The retention time of ethiprole was 2.61min, the qualitative ion pairs were 397.1 / 255.0, 397.1 / 351.0, the quantitative ion pair was 397.1 / 255.0, the EP voltage was 10V, the CXP voltage was 14V, the DP voltage was 70V, and the CE voltage was 47V / 28V;

[0029] The retention time of ethiprole sulfone was 2.87min, the qualitative ion pairs were 411.0 / 281.9, 411.0 / 244.0, the quantitative ion pair was 411.0 / 281.9, the EP voltage was -10V, the CXP voltage was -14V, the DP voltage was -70V, and the CE voltage was -28V / -51V;

[0030] The retention time of ethidium bromide was 2.21min, the qualitative ion pairs were 415.2 / 255.0 and 415.2 / 240.9, the quantitative ion pair was 415.2 / 255.0, the EP voltage was 10V, the CXP voltage was 14V, the DP voltage was 70V, and the CE voltage was 49V / 39V.

[0031] Preferably, the method further comprises the step of preparing a matrix mixed standard solution: taking stock solutions of ethidium bromide, ethidium bromide sulfone and ethidium bromide, mixing them evenly, and adding eggplant blank matrix to obtain a matrix mixed standard solution.

[0032] Preferably, the standard curves and correlation coefficients of ethiprole, ethiprole sulfone and ethiprole amide are:

[0033] The standard curve of ethiprole is y=43300x+4810, and the correlation coefficient is 0.9965;

[0034] The standard curve of ethiprole sulfone is y=68800x+44300, and the correlation coefficient is 0.9974;

[0035] The standard curve of ethidium bromide is y=9030x+1780, and the correlation coefficient is 0.9990.

[0036] Beneficial effects of the present invention:

[0037] (1) The present invention adopts high performance liquid chromatography tandem mass spectrometry for the first time to determine ethiprole and its metabolites ethiprole sulfone and ethiprole amide, and establishes an analytical method for rapid detection of the residues of ethiprole and its metabolites ethiprole sulfone and ethiprole amide in eggplant. The method is simple and has good reproducibility, and can meet the requirements for rapid detection and confirmation of ethiprole and its metabolites ethiprole sulfone and ethiprole amide in eggplant, providing a theoretical basis for the safe and scientific use of ethiprole on eggplant, and filling the gap in the detection method of the residues of ethiprole and its metabolites in eggplant. The method meets the requirements of green environmental protection and has the advantages of simple operation, high efficiency, rapidity, accuracy and sensitivity.

[0038] (2) The present invention adopts dispersed solid phase extraction pretreatment technology combined with high performance liquid phase tandem mass spectrometry detection technology to quickly detect the residual amount of ethiprole and its metabolites in eggplant. The average recovery rate of ethiprole and its metabolites is 78% to 96%, the relative standard deviation (RSD) is 2.5% to 5.3%, the detection limit is 0.002 mg / kg, and the quantitative limit is 0.01 mg / kg.

[0039] (3) The accuracy and precision of the detection method of the present invention meet the technical requirements of residue analysis, and the detection limit meets the requirements of domestic and international technical regulations and limit standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the primary mass spectrum of ethiprole standard;

[0041] Figure 2 This is the secondary mass spectrum of ethiprole standard;

[0042] Figure 3 This is the primary mass spectrum of ethiprole sulfone standard;

[0043] Figure 4 This is the secondary mass spectrum of ethiprole sulfone standard;

[0044] Figure 5 This is the primary mass spectrum of ethidium bromide standard;

[0045] Figure 6 This is the secondary mass spectrum of ethidium bromide standard;

[0046] Figure 7 It is the total ion current chromatogram of ethiprole, ethiprole sulfone and ethiprole amide;

[0047] Figure 8 This is the standard curve of ethiprole;

[0048] Fig. 9 This is the standard curve of ethiprole sulfone;

[0049] Fig.10 This is the standard curve of ethidium bromide. DETAILED DESCRIPTION

[0050] The present invention provides a method for detecting the residual amount of ethidium bromide and its metabolites in eggplant, comprising the following steps:

[0051] S1: Add acetonitrile to the crushed eggplant sample for ultrasonic extraction, then add sodium chloride, mix and centrifuge to obtain an extract;

[0052] S2: Add N-propylethylenediamine (PSA) and anhydrous magnesium sulfate to the extract, mix, let stand, and filter to obtain a test solution;

[0053] S3: Detecting the test solution by high performance liquid chromatography tandem mass spectrometry;

[0054] The HPLC column is a T3 column with gradient elution.

[0055] Mobile phase: Mobile phase A is 0.1% formic acid aqueous solution containing 5 mmol ammonium acetate, and mobile phase B is acetonitrile;

[0056] The gradient elution of the high performance liquid chromatography comprises:

[0057] 0-0.3min, the volume fraction of mobile phase A is 80%, and the volume fraction of mobile phase B is 20%;

[0058] 0.3-1.5min, the volume fraction of mobile phase A changes from 80% to 30%, and the volume fraction of mobile phase B changes from 20% to 70%;

[0059] 1.5-3.2 min, the volume fraction of mobile phase A is 30%, and the volume fraction of mobile phase B is 70%;

[0060] 3.2-3.5 min, the volume fraction of mobile phase A changes from 30% to 80%, and the volume fraction of mobile phase B changes from 70% to 20%;

[0061] 3.5~5.0min, the volume fraction of mobile phase A is 80%, and the volume fraction of mobile phase B is 20%.

[0062] In the present invention, in step S1, the mass ratio of the eggplant sample to the volume of acetonitrile is 10 g:20 mL; the time of the ultrasonic extraction is 5 to 15 min, preferably 10 min; the mass ratio of the eggplant sample to sodium chloride is 10:4 to 8, preferably 10:5 to 7, and further preferably 10:6.

[0063] In the present invention, in step S2, the usage ratio of the extract, N-propylethylenediamine and anhydrous magnesium sulfate is 2 mL: 80-120 mg: 130-170 mg, preferably 2 mL: 90-110 mg: 140-160 mg, and more preferably 2 mL: 100 mg: 150 mg.

[0064] In the present invention, the chromatographic column of the high performance liquid chromatography is: HSS T32.1×100mm 1.8μm, the column temperature is 40℃, the flow rate is 0.4mL / min, and the injection volume is 5μL.

[0065] In the present invention, the main parameters of the mass spectrometer include:

[0066] The ion source was an electrospray ion source (ESI), and the scanning mode was: positive ion scanning for ethiprole and ethiprole amide, and negative ion scanning for ethiprole sulfone;

[0067] Ion source parameters: curtain gas (nitrogen): 30 psi, ion source gas 1 (nitrogen): 55 psi, ion source gas 2 (nitrogen): 55 psi;

[0068] Ion source voltage: 4500 V in positive ion mode, -4500 V in negative ion mode;

[0069] Ion source temperature: 450°C;

[0070] The detection method was multiple reaction monitoring (MRM).

[0071] In the present invention, the mass spectrometry parameters of ethiprole, ethiprole sulfone and ethiprole amide are:

[0072] The retention time of ethiprole was 2.61min, the qualitative ion pairs were 397.1 / 255.0, 397.1 / 351.0, the quantitative ion pair was 397.1 / 255.0, the EP voltage was 10V, the CXP voltage was 14V, the DP voltage was 70V, and the CE voltage was 47V / 28V;

[0073] The retention time of ethiprole sulfone was 2.87min, the qualitative ion pairs were 411.0 / 281.9, 411.0 / 244.0, the quantitative ion pair was 411.0 / 281.9, the EP voltage was -10V, the CXP voltage was -14V, the DP voltage was -70V, and the CE voltage was -28V / -51V;

[0074] The retention time of ethidium bromide was 2.21min, the qualitative ion pairs were 415.2 / 255.0 and 415.2 / 240.9, the quantitative ion pair was 415.2 / 255.0, the EP voltage was 10V, the CXP voltage was 14V, the DP voltage was 70V, and the CE voltage was 49V / 39V.

[0075] The present invention also includes the step of preparing a matrix mixed standard solution: taking stock solutions of ethiprole, ethiprole sulfone and ethiprole amide, mixing them evenly, and adding eggplant blank matrix to obtain a matrix mixed standard solution.

[0076] In the present invention, preferably, 100 μL of ethidium bromide, ethidium bromide sulfone and ethidium bromide stock solutions with a concentration of 10 mg / L are transferred into an injection vial, and 700 μL of eggplant blank matrix is ​​added to prepare a matrix mixed standard solution with a concentration of 1000 ng / mL.

[0077] A series of mixed working solutions with concentrations of 2, 5, 10, 20, 50, 100 and 200 ng / mL were prepared using the eggplant blank matrix by serial dilution method.

[0078] In the present invention, the standard curves and correlation coefficients of ethiprole, ethiprole sulfone and ethiprole amide are:

[0079] The standard curve of ethiprole is y=43300x+4810, and the correlation coefficient is 0.9965;

[0080] The standard curve of ethiprole sulfone is y=68800x+44300, and the correlation coefficient is 0.9974;

[0081] The standard curve of ethidium bromide is y=9030x+1780, and the correlation coefficient is 0.9990.

[0082] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0083] 1. Reagents used in the embodiments of the present invention:

[0084] Ethiopromide standard (purity 97.2%, Tanmo Quality Inspection Standard Material Center);

[0085] Ethiopromide sulfone standard (purity 98.28%, DrEhrenstorferTM);

[0086] Ethiopromide standard (purity 98.9%, Beijing Qincheng Yixin Technology Development Co., Ltd.);

[0087] Acetonitrile (chromatographic grade, Sigma-Aldrich, Co.);

[0088] Formic acid (chromatographic grade, Thermo Fisher Scientific (China) Co., Ltd.);

[0089] Ammonium acetate and sodium chloride (analytical grade, Sinopharm Chemical Reagent Co., Ltd.);

[0090] PSA (40~60μm, Agela Technologies);

[0091] Wahaha ultrapure water (Shenyang Wahaha Qili Food Co., Ltd.).

[0092] II. Instruments and equipment used in the embodiments of the present invention:

[0093] Triple quadrupole liquid spectrometer: Shimadzu LC30AD-AB Sciex TRIPLE QUAD 5500;

[0094] Analytical balance BP211D: Sartorius Scientific Instruments (Beijing) Co., Ltd.;

[0095] Electronic balance JJ300: Changshu Shuangjie Testing Instrument Factory;

[0096] Tabletop high-speed centrifuge HT16MM: Hunan Hexi Instrument Equipment Co., Ltd.;

[0097] Mixer ST-300: Guangdong Zhuoliang Co., Ltd.

[0098] Ultrasonic cleaner KQ-500DE: Kunshan Ultrasonic Instrument Co., Ltd.

[0099] Example

[0100] Preparation of stock solution:

[0101] Ethiopromide stock solution 1000 mg / L: Accurately weigh 0.01029 g of ethiprole standard substance into a small beaker, dissolve it in acetonitrile, transfer it to a 10 mL volumetric flask, and dilute to the mark.

[0102] Ethiopromide sulfone stock solution 1000 mg / L: Accurately weigh 0.01018 g of ethipromide sulfone standard substance into a small beaker, dissolve it in acetonitrile, transfer it to a 10 mL volumetric flask, and dilute to the mark.

[0103] Ethiopromide stock solution 1000 mg / L: Accurately weigh 0.01011 g of ethipromide standard substance into a small beaker, dissolve it in acetonitrile, transfer it to a 10 mL volumetric flask, and dilute to the mark.

[0104] The stock solutions of ethiprole, ethiprole sulfone and ethiprole amide were prepared by serial dilution with acetonitrile into standard solutions with concentrations of 100 mg / L, 10 mg / L and 1 mg / L, respectively.

[0105] Preparation of matrix mixed standard solution:

[0106] Step 1, pretreatment. Weigh 10.00 g of the blank sample of crushed eggplant into a centrifuge tube, add 20 ml of acetonitrile, extract by ultrasonic for 10 min, then add 6 g of sodium chloride, vortex mix for 30 s, centrifuge at 5000 rpm for 3 min, take 2.00 mL of the extract, add 100 mg of PSA and 150 mg of anhydrous magnesium sulfate, vortex mix, let stand, and filter through a 0.22 μm organic filter membrane to obtain the test solution.

[0107] Step 2: Draw the standard curve. Accurately pipette 100 μL of 10 mg / L ethiprole, ethiprole sulfone and ethiprole amide standard solutions into the injection vials, and then add 700 μL of eggplant blank matrix to prepare a matrix mixed standard solution with a concentration of 1000 ng / mL. Use the stepwise dilution method to prepare a series of mixed working solutions with concentrations of 2, 5, 10, 20, 50, 100 and 200 ng / mL using eggplant blank matrix, and test on the machine.

[0108] Step three, test sample detection. Inject the mixed working solution of the above series concentration into high performance liquid chromatography tandem mass spectrometry. Qualitative analysis is performed on the retention time and ion pair mass spectrometry information of ethiprole, ethiprole sulfone and ethiprole amide, and linear regression analysis is performed on the corresponding concentrations in multiple reaction monitoring mode ion peak area to obtain a standard curve. Under the same conditions, the test solution of step one is injected into high performance liquid chromatography tandem mass spectrometry to obtain the ion peak areas of ethiprole, ethiprole sulfone and ethiprole amide, and the contents of ethiprole, ethiprole sulfone and ethiprole amide in the eggplant sample can be calculated by substituting into the standard curve.

[0109] The instrumental analysis conditions for ethiprole and its metabolites ethiprole sulfone and ethiprole amide are as follows:

[0110] Chromatographic conditions:

[0111] Liquid chromatography column: HSS T32.1×100mm 1.8μm;

[0112] Column temperature: 40°C;

[0113] Injection volume: 5 μL;

[0114] The gradient elution program is shown in Table 1.

[0115] Table 1 Gradient elution program

[0116]

[0117] Mass spectrometry conditions:

[0118] Ion source: electrospray ionization source ESI;

[0119] Scanning mode: positive ion (ethiprole and ethiprole amide), negative ion (ethiprole sulfone); ion source voltage: 4500V (ethiprole and ethiprole amide), -4500V (ethiprole sulfone); ion source temperature: 450℃;

[0120] Curtain gas (nitrogen): 35psi;

[0121] Ion source gas 1 (nitrogen), ion source gas 2 (nitrogen): 55 psi;

[0122] EP voltage: 10V (ethiprole and ethiprole amide), -10V (ethiprole sulfone); CXP voltage: 14V (ethiprole and ethiprole amide), -14V (ethiprole sulfone);

[0123] DP: 70V (ethiprole and ethiprole amide), -70V (ethiprole sulfone).

[0124] Detection method: Multiple reaction monitoring (MRM)

[0125] Table 2 Mass spectrometry parameters of ethiprole and its metabolites

[0126]

[0127]

[0128] The determination was carried out under the above-mentioned instrumental analysis conditions, with the solution concentration as the abscissa and the peak area as the ordinate, to produce a standard curve. The linear equation and correlation coefficient are shown in Table 3:

[0129] Table 3 Standard curve and correlation coefficient

[0130] name Standard curve Correlation coefficient Ethiopromide y=43300x+4810 0.9965 Ethiopromide Sulfone y=68800x+44300 0.9974 Ethiopromide y=9030x+1780 0.9990

[0131] The detection limits of ethiprole, ethiprole sulfone and ethiprole amide in eggplant were all 2 ng / mL, and the quantification limits were all 0.01 mg / kg.

[0132] Addition recovery tests were conducted on ethiprole, ethiprole sulfone and ethiprole amide at three addition levels in blank eggplant (n=5). The results are shown in Table 4.

[0133] Table 4 Recovery test results of ethiprole, ethiprole sulfone and ethiprole amide

[0134]

[0135] As can be seen from Table 4, at the three addition levels of 0.01, 0.1 and 0.5 mg / kg, the average recovery of ethiprole in eggplant is 78-90%, and the relative standard deviation (RSD) is 2.9-3.5%; the average recovery of ethiprole sulfone in eggplant is 87-96%, and the relative standard deviation (RSD) is 3.0-3.9%; the average recovery of ethiprole amide in eggplant is 86-89%, and the relative standard deviation (RSD) is 2.5-5.3%. This method can meet the requirements for the residual analysis of ethiprole, ethiprole sulfone and ethiprole amide in eggplant.

[0136] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting the residual amount of ethidium bromide and its metabolites in eggplant, characterized in that: The steps include: S1: Add acetonitrile to the crushed eggplant sample for ultrasonic extraction, then add sodium chloride, mix and centrifuge to obtain an extract; S2: Add N-propylethylenediamine and anhydrous magnesium sulfate to the extract, mix, let stand, and filter to obtain a test solution; S3: Detecting the test solution by high performance liquid chromatography tandem mass spectrometry; The HPLC column is a T3 column with gradient elution. Mobile phase: Mobile phase A is 0.1% formic acid aqueous solution containing 5 mmol ammonium acetate, and mobile phase B is acetonitrile; The gradient elution of the high performance liquid chromatography comprises: 0-0.3min, the volume fraction of mobile phase A is 80%, and the volume fraction of mobile phase B is 20%; 0.3-1.5min, the volume fraction of mobile phase A changes from 80% to 30%, and the volume fraction of mobile phase B changes from 20% to 70%; 1.5-3.2 min, the volume fraction of mobile phase A is 30%, and the volume fraction of mobile phase B is 70%; 3.2-3.5 min, the volume fraction of mobile phase A changes from 30% to 80%, and the volume fraction of mobile phase B changes from 70% to 20%; 3.5~5.0min, the volume fraction of mobile phase A is 80%, and the volume fraction of mobile phase B is 20%.

2. The method for detecting the residual amount of ethidium bromide and its metabolites in eggplant according to claim 1, characterized in that: In the step S1, the mass ratio of the eggplant sample to the volume of acetonitrile is 10 g:20 mL; the ultrasonic extraction time is 5 to 15 min; and the mass ratio of the eggplant sample to sodium chloride is 10:4 to 8.

3. The method for detecting the residual amount of ethidium bromide and its metabolites in eggplant according to claim 1 or 2, characterized in that: In the step S2, the ratio of the extract, N-propylethylenediamine and anhydrous magnesium sulfate is 2 mL: 80-120 mg: 130-170 mg.

4. The method for detecting the residual amount of ethidium bromide and its metabolites in eggplant according to claim 3, characterized in that: The chromatographic column of the high performance liquid chromatography is HSS T32.1×100mm 1.8μm, the column temperature was 40°C, the flow rate was 0.4mL / min, and the injection volume was 5μL.

5. The method for detecting the residual amount of ethidium bromide and its metabolites in eggplant according to claim 1, characterized in that: The main parameters of the mass spectrometer include: The ion source was an electrospray ion source (ESI), and the scanning mode was: positive ion scanning for ethiprole and ethiprole amide, and negative ion scanning for ethiprole sulfone; Ion source parameters: curtain gas: 30 psi, ion source gas 1: 55 psi, ion source gas 2: 55 psi; Ion source voltage: 4500 V in positive ion mode, -4500 V in negative ion mode; Ion source temperature: 450°C; The detection method was multiple reaction monitoring (MRM).

6. The method for detecting the residual amount of ethidium bromide and its metabolites in eggplant according to claim 5, characterized in that: The mass spectrometry parameters of ethiprole, ethiprole sulfone and ethiprole amide are: The retention time of ethiprole was 2.61min, the qualitative ion pairs were 397.1 / 255.0, 397.1 / 351.0, the quantitative ion pair was 397.1 / 255.0, the EP voltage was 10V, the CXP voltage was 14V, the DP voltage was 70V, and the CE voltage was 47V / 28V; The retention time of ethiprole sulfone was 2.87min, the qualitative ion pairs were 411.0 / 281.9, 411.0 / 244.0, the quantitative ion pair was 411.0 / 281.9, the EP voltage was -10V, the CXP voltage was -14V, the DP voltage was -70V, and the CE voltage was -28V / -51V; The retention time of ethidium bromide was 2.21min, the qualitative ion pairs were 415.2 / 255.0 and 415.2 / 240.9, the quantitative ion pair was 415.2 / 255.0, the EP voltage was 10V, the CXP voltage was 14V, the DP voltage was 70V, and the CE voltage was 49V / 39V.

7. The method for detecting the residue of ethidium bromide and its metabolites in eggplant according to claim 1, 4 or 6, characterized in that: The method also includes the step of preparing a matrix mixed standard solution: taking stock solutions of ethiprole, ethiprole sulfone and ethiprole amide, mixing them evenly, and adding eggplant blank matrix to obtain a matrix mixed standard solution.

8. The method for detecting the residue of ethidium bromide and its metabolites in eggplant according to claim 7, characterized in that: The standard curves and correlation coefficients of ethiprole, ethiprole sulfone and ethiprole amide are as follows: The standard curve of ethiprole is y=43300x+4810, and the correlation coefficient is 0.9965; The standard curve of ethiprole sulfone is y=68800x+44300, and the correlation coefficient is 0.9974; The standard curve of ethidium bromide is y=9030x+1780, and the correlation coefficient is 0.9990.

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