A pretreatment method for determining multi-pesticide residues in patchouli

Abstract

The present application discloses a pretreatment method for determining multi-pesticide residues in patchouli, belonging to the technical field of pesticide residue detection. The present application applies magnetic graphitized carboxylation multi-walled carbon nanotubes to the adsorption purification of patchouli matrix, utilizes magnetic graphitized carboxylation multi-walled carbon nanotubes to adsorb impurities in patchouli samples, improves matrix effect, makes analysis results more accurate, and after purification, the magnetic graphitized carboxylation multi-walled carbon nanotubes can be quickly separated by magnetic separation, saving operation time; in addition, the sample pretreatment process of the present application does not artificially introduce exogenous interferences, the sample matrix is ​​relatively simple, the analyte is pure, and the quantitative analysis is more accurate.

Description

Technical Field

[0001] The present application relates to the technical field of pesticide residue detection and preparation, and in particular to a pretreatment method for determining multiple pesticide residues in patchouli. Background Art

[0002] As a Chinese herbal medicine, patchouli has the effects of aromatic turbidity, stopping vomiting, and relieving heat. In June 2022, patchouli was listed as a protected type of Chinese herbal medicine in the "Guangdong Province Lingnan Chinese Herbal Medicine Protection Regulations". With the increase in the application value of patchouli, the demand has also increased, and the area of ​​artificial cultivation has continued to expand. In the process of planting, pests and diseases occur. In order to ensure the yield and quality of patchouli, the use of pesticides is inevitable, resulting in impurities such as pesticides and special derivatives of toxicological significance remaining in the medicinal parts. In order to reduce the amount of pesticide residues in patchouli, pesticide residue detection and analysis is particularly important.

[0003] The main medicinal components of patchouli are volatile oils, the main components of which are patchouli ketone, patchouli alcohol, hexadecanoic acid, d-bitter orange oil alcohol, δ-guaiacene and trans-caryophyllene. The presence of multiple chemical components makes the detection of pesticide residues in patchouli difficult. How to eliminate the interference of these impurities through sample pretreatment technology is a major problem in the determination of multiple pesticide residues in patchouli. At present, the main pretreatment methods for pesticide residues in traditional Chinese medicine include solvent extraction, accelerated solvent extraction, liquid-liquid distribution, solid phase microextraction, etc. These methods have the problems of long time consumption, large reagent consumption, unstable recovery of the analyte, easy decomposition, and high cost of solid phase microextraction. In addition, the pretreatment process of the QuEChERS method and the SPE method published in the Pharmacopoeia in 2020 is complex, costly, and time-consuming. How to develop a more efficient, convenient, low-cost, and effective method for detecting banned pesticide residues in patchouli that can effectively reduce the matrix effect compared to the pharmacopoeia method and improve the accuracy of the detection method is a problem worth studying. Summary of the invention

[0004] The purpose of the present disclosure is to overcome the shortcomings of the prior art and provide a pretreatment method for determining multiple pesticide residues in patchouli. The pretreatment method provided by the present application has good purification effect, simple operation, and short processing time. The sample pretreatment method of the present application is used to extract and purify the pesticide residues in patchouli before testing, which has the advantages of accurate test results, low matrix effect, and simultaneous analysis of 33 pesticide residues.

[0005] To achieve the above object, the technical solution adopted by the present disclosure is: providing a pretreatment method for determining multi-pesticide residues in patchouli, comprising the following steps:

[0006] The sample to be tested and acetonitrile are mixed and homogenized, shaken, and centrifuged to obtain an acetonitrile extract;

[0007] The acetonitrile extract is injected into a gas-liquid microextraction device for a first purification to obtain an extract;

[0008] The magnetic graphitized carboxylated multi-walled carbon nanotubes are added to the extract for a second purification, and then magnetic separation is performed. The obtained purified liquid is filtered through a filter membrane, and the clear liquid is collected as the test liquid after pre-treatment.

[0009] In one embodiment, the preparation method of the magnetic graphitized carboxylated multi-walled carbon nanotubes comprises the following steps: reacting graphitized multi-walled carbon nanotubes and sulfuric acid at 55-65° C. for 2-4 hours, filtering, washing and drying the obtained product to obtain graphitized carboxylated multi-walled carbon nanotubes, wherein the mass ratio of the graphitized multi-walled carbon nanotubes to the volume ratio of sulfuric acid is 1 g:70-90 mL; placing ferroferric oxide and graphitized carboxylated multi-walled carbon nanotubes in acetonitrile, shaking, and magnetically separating, and the obtained solid product is magnetic graphitized carboxylated multi-walled carbon nanotubes; wherein the mass ratio of ferroferric oxide to graphitized carboxylated multi-walled carbon nanotubes is 3-5:1, and the volume ratio of the total mass of ferroferric oxide and graphitized carboxylated multi-walled carbon nanotubes to acetonitrile is 7-10 mg:1 mL.

[0010] In one embodiment, the volume ratio of the sample to be tested to acetonitrile is 1 g: 3-15 mL.

[0011] In one embodiment, the conditions for the first purification are as follows: heating temperature: 250-280°C, condensing temperature: (-2)-(-3)°C, gas flow rate: 1.5-2SSCM, extraction time: 10-15min, extraction solvent: 30-50μL, elution solvent: 20-50μL; wherein the extraction solvent is ethyl acetate and the elution solvent is acetonitrile.

[0012] In one embodiment, the mass ratio of the magnetic graphitized carboxylated multi-walled carbon nanotubes to the volume ratio of the extract is 5-30 mg:1 mL.

[0013] In one embodiment, the homogenization time is 60-150 s.

[0014] In one embodiment, the second purification is performed under vortex conditions, and the time of the second purification is 20-80 seconds.

[0015] In one embodiment, the types of the multi-pesticides are methamidophos, fenamidophos, fenamidophos sulfone, fenamidophos sulfoxide, fenthion, chlorsulfuron, carbofuran, 3-hydroxycarbofuran, ethametsulfuron, metsulfuron, chlorsulfuron, cadusafos, chlorfenapyr, phorate, phorate sulfoxide, phorate sulfone, coumaphos, thiocyanate, phosphamidon, aldicarb, aldicarb sulfone, aldicarb sulfoxide, monocrotophos, demeton, ethophos, terbufos sulfone, terbufos sulfoxide, isocarbophos, chlordimeform, methyl isoflavone At least one of phosphorus, α-BHC, terbuthion, γ-BHC, fluonitrile, β-BHC, δ-BHC, aldrin, methyl parathion, o,p'-dicofol, fipronil sulfoxide, fipronil, parathion, p,p'-dicofol, α-endosulfan, fipronil sulfone, dieldrin, 4,4'-DDE, methyl thiocyclophosphite, herbicide ether, 2,4'-DDT, 4,4'-DDT, β-endosulfan, 4,4'-DDT, and endosulfan sulfate.

[0016] Compared with the prior art, the beneficial effects of the present disclosure are as follows: the present application applies gas-liquid microextraction to the primary purification of patchouli, and the gas-liquid microextraction technology is a green and environmentally friendly pretreatment technology that integrates extraction, purification, and concentration. It can effectively extract various volatile and semi-volatile organic compounds from various matrices, and this technology helps to remove impurities such as patchouli ketone, patchouli alcohol, and d-bitter orange oil alcohol in patchouli. The method has the advantages of being fast, efficient, economical, simple, with low solvent usage, and strong operability. Magnetic graphitized carboxylated multi-walled carbon nanotubes are applied to the adsorption purification of patchouli matrix, and magnetic graphitized carboxylated multi-walled carbon nanotubes are used to adsorb impurities in patchouli samples, improve matrix effects, and make analysis results more accurate. After purification, the magnetic graphitized carboxylated multi-walled carbon nanotubes can be quickly separated by magnetic separation, saving operation time; in addition, the sample pretreatment process of the present application does not artificially introduce exogenous interferences, the sample matrix is ​​relatively simple, the analyte is pure, and the quantitative analysis is more accurate. DETAILED DESCRIPTION

[0017] In order to better illustrate the purpose, technical scheme and advantages of the present disclosure, the present disclosure will be further described below in conjunction with specific embodiments and comparative examples, the purpose of which is to understand the content of the present disclosure in detail, rather than to limit the present disclosure. All other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure. The experimental reagents and instruments involved in the implementation of the present disclosure are all commonly used ordinary reagents and instruments unless otherwise specified.

[0018] The present application provides a pretreatment method for determining multi-pesticide residues in patchouli, comprising the following steps:

[0019] The sample to be tested and acetonitrile are mixed and homogenized, shaken, and centrifuged to obtain an acetonitrile extract;

[0020] The acetonitrile extract is injected into a gas-liquid microextraction device for a first purification to obtain an extract;

[0021] The magnetic graphitized carboxylated multi-walled carbon nanotubes are added to the extract for a second purification, and then magnetic separation is performed. The obtained purified liquid is filtered through a filter membrane, and the clear liquid is collected as the test liquid after pre-treatment.

[0022] In the present application, the sample to be tested and acetonitrile are mixed and homogenized to obtain a homogenate. In the present application, the sample to be tested is a powdered patchouli sample. Preferably, the particle size of the patchouli sample is ≤75 nm. The present application has no special requirements on the source of the patchouli sample. Patchouli from any source can be pre-treated using the method of the present application.

[0023] In the present application, the mass ratio of the sample to be tested to the volume ratio of acetonitrile is 1g:3-15mL, for example, it can be but not limited to 1g:3mL, 1g:6mL, 1g:9mL, 1g:12mL, 1g:15mL, preferably 1g:6mL.

[0024] In the present application, the homogenization time is 60-150s, for example, it can be but not limited to 60s, 80s, 100s, 120s, 150s, preferably 100s; the homogenization does not require a medium. The homogenization method described in the present application is preferably carried out using a homogenizer. The homogenization method described in the present application is not particularly limited, and the homogenization method well known to those skilled in the art can be used. The homogenization is conducive to breaking the patchouli, releasing the pesticides in the patchouli, and extracting them with acetonitrile.

[0025] In the present application, the oscillation method is not particularly limited, and any oscillation method known to those skilled in the art can be used. In the embodiment of the present application, the oscillation is specifically performed by a vortex method.

[0026] In the present application, the method of solid-liquid separation is not particularly limited, and the method of solid-liquid separation well known to those skilled in the art can be used. In the embodiment of the present application, solid-liquid separation is specifically carried out by centrifugation. The centrifugation time is 5-15min, preferably 10min. The centrifugation speed is preferably 4000-6500rpm, more preferably 6000rpm.

[0027] After obtaining the acetonitrile extract, the present application injects the acetonitrile extract into a gas-liquid microextraction device for a first purification to obtain an extract.

[0028] Gas-liquid microextraction technology is a green and environmentally friendly pretreatment technology that integrates extraction, purification and concentration. It can effectively extract various volatile and semi-volatile organic compounds from various matrices. This technology helps to remove impurities such as patchouli ketone, patchouli alcohol and d-bitter orange oil alcohol in patchouli.

[0029] Specifically, the conditions for the first purification are as follows: heating temperature: 250-280°C, condensing temperature: (-2)-(-3)°C, gas flow rate: 1.5-2SSCM, extraction time: 10-15min, extraction solvent: 30-50μL, elution solvent: 20-50μL; wherein the extraction solvent is ethyl acetate and the elution solvent is acetonitrile.

[0030] Selecting the above parameters can more effectively remove impurities such as patchouli ketone, patchouli alcohol and d-bitter orange oil alcohol in patchouli.

[0031] After obtaining the extract, the present invention adds magnetic graphitized carboxylated multi-walled carbon nanotubes into the extract for a second purification, and obtains a purified liquid after magnetic separation.

[0032] In the present application, the purification reagent is magnetic graphitized carboxylation multi-walled carbon nanotubes. On the one hand, the functional groups bonded to the surface of the magnetic graphitized carboxylation multi-walled carbon nanotubes are used to form non-covalent bonds with hydroxyl groups in molecules such as organic acids in the matrix to remove such impurities; on the other hand, the hydrophilicity and polarity of the surface bonded magnetic graphitized carboxylation multi-walled carbon nanotubes are used to remove polar compounds in the acetonitrile extract; on the other hand, the pigments in the patchouli matrix are adsorbed by electrostatic adsorption. The above multiple aspects work together to purify the patchouli matrix, which can significantly reduce the matrix effect, increase the extraction amount of pesticides in the patchouli matrix, and improve the detection results of pesticide residues; optionally, the average particle size of the magnetic graphitized carboxylation multi-walled carbon nanotubes is 10-20nm.

[0033] Specifically, the mass ratio of the magnetic graphitized carboxylated multi-walled carbon nanotubes to the volume ratio of the extract is 5-30 mg:1 mL, for example, but not limited to 5 mg:1 mL, 10 mg:1 mL, 15 mg:1 mL, 20 mg:1 mL, 25 mg:1 mL, 30 mg:1 mL; preferably 15 mg:1 mL.

[0034] In the present application, the second purification is carried out under vortex conditions, and the time of the second purification is 20-80s, more preferably 30s.

[0035] In the present application, the method for preparing magnetic graphitized carboxylated multi-walled carbon nanotubes comprises the following steps:

[0036] (1) reacting graphitized multi-walled carbon nanotubes and sulfuric acid at 55-65° C. for 2-4 hours, filtering, washing, and drying the resulting product to obtain graphitized carboxylated multi-walled carbon nanotubes, wherein the mass ratio of the graphitized multi-walled carbon nanotubes to the volume ratio of sulfuric acid is 1 g:70-90 mL;

[0037] Specifically, the reaction conditions also include stirring and reflux; stirring and reflux can ensure that the graphitized multi-walled carbon nanotubes and sulfuric acid react fully.

[0038] Optionally, the reaction temperature can be but not limited to 55°C, 57°C, 60°C, 62°C, 65°C, preferably 60°C; the reaction time can be but not limited to 2h, 2.5h, 3h, 3.5h, 4h, preferably 3h.

[0039] Optionally, the volume ratio of the mass of the graphitized multi-walled carbon nanotubes to sulfuric acid can be, but is not limited to, 1g:70mL, 1g:75mL, 1g:80mL, 1g:85mL, 1g:90mL, preferably 1g:80mL.

[0040] Specifically, the filtering, washing and drying methods are not specifically limited and any filtering, washing and drying methods well known to those skilled in the art may be used.

[0041] Specifically, in the present application, the washing solvent is deionized water, and the end point of the washing is washing with deionized water until the filtrate is neutral; the drying temperature in the embodiment of the present application is 50-70°C, preferably 60°C, and the drying time is 3-24h, preferably 6-12h.

[0042] In the present application, there is no particular restriction on the source of graphitized carboxylated multi-walled carbon nanotubes, which can be purchased from a commodity or prepared by oneself.

[0043] (2) placing ferroferric oxide and graphitized carboxylated multi-walled carbon nanotubes in acetonitrile, shaking, and magnetically separating, thereby obtaining a solid product of magnetic graphitized carboxylated multi-walled carbon nanotubes; wherein the mass ratio of ferroferric oxide to graphitized carboxylated multi-walled carbon nanotubes is 2-8:1, and the volume ratio of the total mass of ferroferric oxide and graphitized carboxylated multi-walled carbon nanotubes to acetonitrile is 1.0 mg:5-25 mL.

[0044] In the present application, the mass ratio of the ferrosoferric oxide to the graphitized carboxylated multi-walled carbon nanotubes may be, but is not limited to, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1; preferably 4:1.

[0045] In the present application, the volume ratio of the total mass of the ferrosoferric oxide and graphitized carboxylated multi-walled carbon nanotubes to acetonitrile can be but not limited to 5 mg:1 mL, 10 mg:1 mL, 15 mg:1 mL, 20 mg:1 mL, 25 mg:1 mL; preferably 15 mg:1 mL.

[0046] After the second purification is completed, the present application performs magnetic separation on the mixed solution, filters the obtained purified solution through a filter membrane, and collects the clear liquid as the sample solution to be tested. In the present application, the method of magnetic separation is preferably to place the mixed solution in a magnetic environment for separation for 2-3s; the magnetic environment is preferably a magnet. Magnetic graphitized carboxylated multi-walled carbon nanotubes are magnetic. The present application uses magnetic separation to adsorb the magnetic graphitized carboxylated multi-walled carbon nanotube magnet on one side or the bottom to achieve solid-liquid phase separation. The present application uses magnetic separation to quickly separate the adsorbent in the mixed solution, saving operation time and improving processing efficiency.

[0047] In the present application, the pore size of the filtration membrane is preferably 0.22 μm.

[0048] In the present application, the types of the multi-pesticides are methamidophos, fenamidophos, fenamidophos sulfone, fenamidophos sulfoxide, fenthion, chlorpyrifos, carbofuran, 3-hydroxycarbofuran, ethametsulfuron, metsulfuron, chlorsulfuron, cadusafos, chlorfenapyr, phorate, phorate sulfoxide, phorate sulfone, coumaphos, thiocyanate, phosphamidon, aldicarb, aldicarb sulfone, aldicarb sulfoxide, monocrotophos, demeton, ethophos, terbufos sulfone, terbufos sulfoxide, isocarbophos, chlordimeform, methyl isoflavone , α-BHC, terbuthion, γ-BHC, fluonitrile, β-BHC, δ-BHC, aldrin, methyl parathion, o,p'-dicofol, fipronil sulfoxide, fipronil, parathion, p,p'-dicofol, α-endosulfan, fipronil sulfone, dieldrin, 4,4'-DDE, methyl thiocyclophosphite, herbicide ether, 2,4'-DDT, 4,4'-DDT, β-endosulfan, 4,4'-DDT, and at least one of endosulfan sulfate.

[0049] After obtaining the test liquid, the present application preferably uses LC-MS / MS or GC-MS / MS to analyze and detect the multi-pesticide residues in the test liquid. The present application has no special requirements for specific detection conditions, and conditions familiar to technicians in this field can be used.

[0050] The technical solution in the present application will be clearly and completely described below in conjunction with the embodiments in the present application.

[0051] In the following examples, the magnetic graphitized carboxylated multi-walled carbon nanotubes are homemade, and the preparation method thereof is as follows:

[0052] Preparation of graphitized carboxylated multi-walled carbon nanotubes: 1.0 g of graphitized multi-walled carbon nanotubes was placed in 80 mL of sulfuric acid and refluxed at 60° C. for 3 h; after the reaction was completed, the mixture was naturally cooled to room temperature, filtered, and washed with deionized water until the filtrate was neutral, and then the product was dried at 60° C. overnight to obtain graphitized carboxylated multi-walled carbon nanotubes, which were stored in a desiccator;

[0053] Preparation of magnetic graphitized carboxylated multi-walled carbon nanotubes: 400 mg of ferrosoferric oxide and 100 mg of graphitized carboxylated multi-walled carbon nanotubes were added to 100 mL of acetonitrile, shaken for 2 minutes, and then magnetically separated with a permanent magnet. The obtained solid product was placed in a vacuum drying oven and dried at 60° C. for 6 hours to obtain magnetic graphitized carboxylated multi-walled carbon nanotubes.

[0054] Example 1

[0055] This embodiment provides a pretreatment method for pesticide residues in patchouli, comprising the following steps:

[0056] Place patchouli in a vacuum drying oven and dry to constant weight, place the dried patchouli in a grinder and grind it, then sieve (200 mesh) 75 μm patchouli powder; weigh 1 g (accurate to 0.01 g) of patchouli powder in a 10 mL centrifuge tube, add 5.0 mL of acetonitrile to the centrifuge tube, homogenize for 1 min, shake, and centrifuge at 6000 r / min for 10 min. The resulting supernatant is the acetonitrile extract;

[0057] 1.0 mL of acetonitrile extract was injected into a gas-liquid microextraction device for the first purification to obtain an extract; wherein, the conditions for the first purification were heating temperature: 260°C, condensation temperature: -2°C, gas flow rate: 1.5 SSCM, extraction time: 12 min, extraction solvent: 50 μL, elution solvent: 50 μL; wherein, the extraction solvent was ethyl acetate, and the elution solvent was acetonitrile; 15 g of magnetic graphitized carboxylated multi-walled carbon nanotubes was added to 1 mL of the extract, vortexed for 30 seconds, and magnetic separation was performed, the supernatant was filtered through a 0.22 μm filter membrane, and the obtained filtrate was used as the test liquid for LC-MS / MS or GC-MS / MS analysis.

[0058] Example 2

[0059] This embodiment provides a pretreatment method for pesticide residues in patchouli, which is different from the pretreatment method in Example 1 only in that the mass of the magnetic graphitized carboxylated multi-walled carbon nanotubes is 25 mg.

[0060] Example 3

[0061] This embodiment provides a pretreatment method for pesticide residues in patchouli, which is different from the pretreatment method in Example 1 only in that the mass of the magnetic graphitized carboxylated multi-walled carbon nanotubes is 50 mg.

[0062] Comparative Example 1

[0063] This embodiment provides a pretreatment method for pesticide residues in patchouli, which is different from the pretreatment method in Example 1 only in that Crab / NH2 is used to replace magnetic graphitized carboxylated multi-walled carbon nanotubes.

[0064] Example 4

[0065] Taking 33 kinds of pesticides such as methamidophos, fenamiphos, and fenamiphos sulfone as the detection objects, the pretreatment method provided in the present application was evaluated, specifically: using pesticide standard products and chromatographic grade methanol to prepare a pesticide standard solution, adding the pesticide standard solution to the patchouli sample, controlling the addition concentration to be 40-250 μg / kg, standing for 30 minutes, and performing pretreatment according to the methods in Examples 1-3 and Comparative Example 1, and then performing LC-MS / MS or GC-MS / MS analysis on the obtained test solution;

[0066] 1. Gas chromatography-tandem mass spectrometry

[0067] Chromatographic conditions: an elastic quartz capillary column (column length 30m, column inner diameter 0.25mm, film thickness 0.25 / μm) with (50% phenyl)-methylpolysiloxane as the stationary phase. The injection port temperature was 250°C, and the injection was non-split. The carrier gas was high-purity helium (He). The injection port was in constant pressure mode, and the pressure before the column was 146kPa. Program temperature rise: initial temperature 60°C, maintained for 1 minute, raised to 120°C at 30°C / min, then raised to 160°C at a rate of 10°C per minute, then raised to 230°C at a rate of 2°C per minute, and finally raised to 300°C at a rate of 15°C per minute, and maintained for 6 minutes.

[0068] The mass spectrometry conditions were triple quadrupole tandem mass spectrometer detection; the ion source was electron impact source (EI), the ion source temperature was 250°C, and the collision gas was nitrogen or argon.

[0069] The mass spectrometer transmission interface temperature is 250℃. The mass spectrometer monitoring mode is multiple reaction monitoring (MRM). To improve the detection sensitivity, each pesticide can be monitored in segments according to the retention time.

[0070] 2. High performance liquid chromatography-tandem mass spectrometry

[0071] Chromatographic conditions: Octadecylsilane bonded silica gel was used as the filler (column length 10 cm, inner diameter 2.1 mm, particle size 2.6 μm. 0.1% formic acid solution (containing 5 mmol / L ammonium formate) was used as mobile phase A, acetonitrile-0.1% formic acid solution (containing 5 mmol / L ammonium formate) (95:5) was used as mobile phase B, and gradient elution was performed according to the conditions in Table 1; the flow rate was 0.3 mL per minute, and the column temperature was 40°C.

[0072] Table 1

[0073] Time (minutes) Mobile phase A (%) Mobile phase B (%) 0-1 70 30 1-12 70-0 30-100 12-14 0 100

[0074] The mass spectrometry conditions were triple quadrupole tandem mass spectrometer detection; the ion source was electron impact source (EI), the ion source temperature was 250°C, and the collision gas was nitrogen or argon.

[0075] The mass spectrometer transmission interface temperature was 250°C. The mass spectrometer monitoring mode was multiple reaction monitoring (MRM). To improve the detection sensitivity, each pesticide could be monitored in segments according to the retention time.

[0076] 1. Investigation of linear relationships among 33 pesticides

[0077] 33 kinds of pesticides were accurately weighed and prepared into reference solutions of different concentrations. The concentration gradient of the reference solutions is shown in Table 2, and the concentration unit is μg / mL. 1 μL of 6 reference solutions of different concentrations was accurately drawn, and the samples were injected and analyzed under the specified chromatographic conditions. The chromatographic peak area was recorded, and the standard curve was drawn with the peak area as the ordinate and the reference concentration as the abscissa. The results are shown in Tables 3 and 4.

[0078] Table 2 Concentration of reference solution

[0079]

[0080]

[0081] Table 3 Results of linear relationship investigation of HPLC-MS / MS

[0082]

[0083]

[0084]

[0085] Table 4 Results of linear relationship investigation of gas chromatography-tandem mass spectrometry

[0086]

[0087]

[0088]

[0089] 2. Repeatability test

[0090] Take a blank patchouli matrix sample, and pre-treat the blank Chinese medicinal material matrix according to the pre-treatment method in Example 1. Then add the banned pesticide standard sample with the same concentration as in the third column of Table 1, inject and analyze under the specified chromatographic conditions, calculate the test concentration of the banned pesticide in the sample to be tested according to the standard curve in Table 3 or Table 4, perform 6 parallel tests, and calculate the relative standard deviation (RSD) based on the 6 measured test concentrations. The test results are shown in Tables 5 and 6.

[0091] Table 5 Results of investigation on the repeatability relationship of HPLC-MS / MS

[0092]

[0093]

[0094] Table 6 Results of investigation on the repeatability relationship of gas chromatography-tandem mass spectrometry

[0095]

[0096]

[0097] From the experimental data in Table 5 and Table 6, it can be seen that for the same batch of samples, the RSD values ​​of the banned pesticides measured 6 times are less than 5%, indicating that the pretreatment method of this application has good repeatability.

[0098] 3. Accuracy test

[0099] Take a blank patchouli matrix sample, and pre-treat the blank Chinese medicinal material matrix according to the pre-treatment method in Example 1. Then add the same banned pesticide standard as in Table 1, and the amount of banned pesticide standard added is shown in Table 7 and Table 8. Inject and analyze under the specified chromatographic conditions, calculate the test concentration of banned pesticides in the sample to be tested according to the standard curve in Table 3 or Table 4, test 6 times in parallel, calculate the relative standard deviation (RSD) according to the 6 times measured recovery rate, and the test results are shown in Table 7 and Table 8; wherein, recovery rate (Recoveries) = (measured concentration / added concentration) * 100%.

[0100] Table 7 Recovery results of HPLC-MS / MS

[0101]

[0102]

[0103] Table 8 Recovery results of gas chromatography-tandem mass spectrometry

[0104]

[0105]

[0106] It can be seen from the data in Tables 7 and 8 that the recovery rate of Example 1 varies depending on the type of pesticide. The different amounts of magnetic graphitized carboxylated multi-walled carbon nanotubes used will also result in differences in the recovery rate. Compared with Comparative Example 1 (i.e., not using magnetic graphitized carboxylated multi-walled carbon nanotubes for purification), the RSD values ​​of Examples 2-3 are smaller, indicating that the test results are more accurate.

[0107] Finally, it should be noted that the above embodiments are used to illustrate the technical solution of the present disclosure rather than to limit the protection scope of the present disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present disclosure can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present disclosure.

Claims

1. A pretreatment method for determining multi-pesticide residues in patchouli, characterized in that: The following steps are involved: The sample to be tested and acetonitrile are mixed and homogenized, shaken, and centrifuged to obtain an acetonitrile extract; The acetonitrile extract is injected into a gas-liquid microextraction device for a first purification to obtain an extract; Adding magnetic graphitized carboxylated multi-walled carbon nanotubes into the extract for a second purification, and then performing magnetic separation, filtering the obtained purified liquid through a filter membrane, and collecting the clear liquid as the test liquid after pre-treatment; The conditions of the first purification are as follows: heating temperature: 250-280°C, condensation temperature: (-2)-(-3)°C, gas flow rate: 1.5-2SSCM, extraction time: 10-15min, extraction solvent: 30-50μL, elution solvent: 20-50μL; wherein the extraction solvent is ethyl acetate and the elution solvent is acetonitrile; The second purification is carried out under vortex conditions, and the time of the second purification is 20-80s.

2. The pre-treatment method according to claim 1, characterized in that: The method for preparing magnetic graphitized carboxylated multi-walled carbon nanotubes comprises the following steps: The graphitized multi-walled carbon nanotubes and sulfuric acid are reacted at 55-65° C. for 2-4 hours, and the obtained product is filtered, washed, and dried to obtain graphitized carboxylated multi-walled carbon nanotubes, wherein the mass ratio of the graphitized multi-walled carbon nanotubes to the volume ratio of sulfuric acid is 1 g:70-90 mL; The ferroferric oxide and graphitized carboxylated multi-walled carbon nanotubes are placed in acetonitrile, shaken, and magnetically separated to obtain a solid product which is magnetic graphitized carboxylated multi-walled carbon nanotubes; wherein the mass ratio of the ferroferric oxide to the graphitized carboxylated multi-walled carbon nanotubes is 3-5:1, and the volume ratio of the total mass of the ferroferric oxide and the graphitized carboxylated multi-walled carbon nanotubes to acetonitrile is 7-10 mg:1 mL.

3. The pre-treatment method according to claim 1, characterized in that: The mass ratio of the sample to be tested to the volume ratio of acetonitrile is 1 g: 3-15 mL.

4. The pre-treatment method according to claim 1, characterized in that: The mass ratio of the magnetic graphitized carboxylated multi-walled carbon nanotubes to the volume ratio of the extract is 5-30 mg:1 mL.

5. The pre-treatment method according to claim 1, characterized in that: The homogenization time is 60-150s.

6. The pre-treatment method according to claim 1, characterized in that: The types of the multi-pesticides are methamidophos, fenamidophos, fenamidophos sulfone, fenamidophos sulfoxide, fenthion, chlorpyrifos, carbofuran, 3-hydroxycarbofuran, ethametsulfuron, metsulfuron, chlorsulfuron, cadusafos, chlorfenapyr, phorate, phorate sulfoxide, phorate sulfone, coumaphos, thiocyanate, phosphamidon, aldicarb, aldicarb sulfone, aldicarb sulfoxide, monocrotophos, demeton, ethophos, terbufos sulfone, terbufos sulfoxide, isocarbophos, chlordimeform, methyl isoflavone, α- At least one of Benzene hexachloride, terbuthion, γ-Benzene hexachloride, fluonitrile, β-Benzene hexachloride, δ-Benzene hexachloride, aldrin, methyl parathion, o,p'-dicofol, fipronil sulfoxide, fipronil, parathion, p,p'-dicofol, α-endosulfan, fipronil sulfone, dieldrin, 4,4'-DDE, methyl thiocyclophosphite, herbicide ether, 2,4'-DDT, 4,4'-DDT, β-endosulfan, 4,4'-DDT, and endosulfan sulfate.

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