Method for determining pesticide residues in cotton fibers

Abstract

The invention relates to the technical field of fiber detection, and particularly discloses a method for determining pesticide residues in cotton fibers. The method for determining the pesticide residues in the cotton fibers comprises the following steps: crushing and drying the cotton fibers to obtain a cotton fiber sample; acetonitrile and glacial acetic acid are mixed, a salting-out agent is added, an extraction reagent is obtained, a cotton fiber sample is added into the extraction reagent for extraction, and an extracting solution sample is obtained; adding quaternary ammonium salt bonded silica gel, octadecylsilane bonded silica gel and a carbon adsorbent into the extracting solution sample, and adding anhydrous magnesium sulfate to obtain an adsorption solution sample; and concentrating the adsorption liquid sample, uniformly mixing the concentrated adsorption liquid sample with an acetone / normal hexane mixed solution to obtain a to-be-detected liquid sample, and determining the to-be-detected liquid sample by using a liquid chromatography-mass spectrometry method. According to the method, the extraction effect of the pesticide residues in the cotton fibers is improved, impurity interference and loss of the extracted pesticide residues are reduced, and the recovery rate of the pesticide residues in the process of measuring the pesticide residues in the cotton fibers can be increased.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber detection, and particularly to a method for determining pesticide residues in cotton fibers. Background Art

[0002] As an important global natural textile raw material, cotton fibers are often involved in the use of various pesticides such as insecticides, herbicides, and fungicides during the planting process to ensure the growth and yield of cotton. However, pesticide residues can enter textiles through the fiber processing link, potentially posing a threat to human health and environmental safety. Therefore, establishing an efficient, sensitive, and accurate method for detecting pesticide residues in cotton fibers is of great significance for ensuring the safety of textiles and promoting the development of green agriculture.

[0003] In related technologies, a method for determining pesticide residues is disclosed, belonging to the technical field of pesticide determination. The UPLC-QTOF-MS method is used to determine the contents of various pesticide components in a sample to be tested, and the pesticide components include both insecticides and fungicides; the liquid chromatography conditions include: mobile phase A is methanol, mobile phase B is an aqueous ammonium acetate solution or an aqueous formic acid solution; the flow rate is 0.3 - 0.5 mL / min; the elution program of mobile phase A is: 0 - 0.5 min, 2%; 0.5 - 15 min, 2 - 98%; 15 - 17 min, 98%; 17 - 17.1 min, 98 - 2%; 17.1 - 20 min, 2%; the mass spectrometry conditions include: using an electrospray ionization source, positive ion mode; full scan mode, and the scanning mass range is 50 - 1000 m / z, etc.

[0004] However, cotton fibers are hydrophobic, which may cause some pesticides to adsorb on the fiber surface, resulting in low extraction efficiency of traditional solvents. Pigments and lipids in cotton fibers may clog the chromatographic column or interfere with mass spectrometry detection. Therefore, the recovery rate of pesticide residues may be low, affecting the accuracy of the determination method. Summary of the Invention

[0005] In order to improve the recovery rate of pesticide residues in the process of determining pesticide residues in cotton fibers, the present application provides a method for determining pesticide residues in cotton fibers.

[0006] A method for determining pesticide residues in cotton fibers provided by the present application adopts the following technical solution:

[0007] A method for determining pesticide residues in cotton fibers includes the following steps:

[0008] S1. Crush and dry the cotton fibers to obtain a cotton fiber sample;

[0009] S2. Mix acetonitrile and glacial acetic acid in a volume ratio of 100:(0.5 - 1.8), add a salting - out agent at a dosage of 1 - 1.4 g / 100 mL, mix evenly to obtain an extraction reagent. Add the cotton fiber sample to the extraction reagent for extraction, perform ultrasonic oscillation at 280 - 350 W and 35 - 55 °C for 15 - 40 min, centrifuge, and collect the supernatant to obtain an extract sample;

[0010] S3. Add quaternary ammonium salt - bonded silica gel, octadecylsilane - bonded silica gel, and carbon adsorbent to the extract sample. After mixing evenly, add anhydrous magnesium sulfate at a dosage of 3.6 - 4.2 g / 100 mL, mix evenly, centrifuge, and collect the supernatant to obtain an adsorbed liquid sample; the addition amount of quaternary ammonium salt - bonded silica gel in every 100 mL of the extract sample is 0.01 - 0.015 g, and the mass ratio of the quaternary ammonium salt - bonded silica gel, octadecylsilane - bonded silica gel, and carbon adsorbent is 10:(4 - 6):(1 - 3);

[0011] S4. Concentrate the adsorbed liquid sample, remove the solution, then mix it evenly with an acetone / n - hexane mixed solution to obtain a sample to be measured, and use liquid chromatography - mass spectrometry to measure the sample to be measured.

[0012] By adopting the above - mentioned technical solution, acetonitrile has excellent solubility for pesticides. Glacial acetic acid adjusts the pH of the extract to weakly acidic, inhibits the hydrolysis of pesticides, and at the same time enhances the protonation extraction efficiency for basic pesticides. The salting - out agent promotes the stratification of the acetonitrile phase and the water phase through the salting - out effect, concentrating the target substances in the acetonitrile layer. The ultrasonic cavitation effect destroys the wax layer of cotton fibers and releases the encapsulated pesticide residues. Therefore, in this application, the cotton fibers are first crushed and dried, and then through the synergistic effect of acetonitrile, glacial acetic acid, the salting - out agent, and the ultrasonic process, the extraction effect of pesticide residues in cotton fibers is improved. Then, the quaternary ammonium salt - bonded silica gel adsorbs fatty acids, organic acids, and sugar interferents in cotton fibers through ion - exchange. Octadecylsilane - bonded silica gel removes non - polar impurities such as lipids and sterols through hydrophobic interaction. The carbon adsorbent selectively adsorbs planar - structured pigments and has less adsorption for non - planar pesticides, which can reduce adsorption loss. Anhydrous magnesium sulfate is used for thorough dehydration to eliminate the interference of moisture on subsequent liquid chromatography - mass spectrometry analysis. After concentration, it is replaced with an acetone / n - hexane mixed solution. Acetone enhances the solubility of polar pesticides, and n - hexane inhibits the matrix effect, adapts to the liquid chromatography - mass spectrometry mobile phase system, reduces ion suppression, can reduce the interference of components such as pigments and lipids in cotton fibers, and reduces the loss of pesticide residues extracted in step S2. Therefore, this application helps to improve the recovery rate of pesticide residues in the process of measuring pesticide residues in cotton fibers by improving the extraction effect of pesticide residues in cotton fibers, reducing impurity interference, and reducing the loss of extracted pesticide residues.

[0013] In a specific feasible implementation, in step S2, a non-ionic surfactant is added to the extraction reagent, mixed evenly, and then the cotton fiber sample is added to the extraction reagent for extraction.

[0014] By adopting the above technical solution, the non-ionic surfactant can penetrate and destroy the waxy structure on the surface of cotton fibers by reducing the surface tension of the solvent, which helps to release the encapsulated pesticide residues. Moreover, the non-ionic surfactant binds to the pigments in the cotton fibers through hydrogen bonds, reducing the migration of pigments to the acetonitrile phase, which helps to reduce the pigment dissolution amount, thereby further reducing the interference of pigments.

[0015] In a specific feasible implementation, the salting-out agent includes sodium sulfate and sodium citrate with a mass ratio of (3 - 5):1.

[0016] By adopting the above technical solution, Na 2 SO 4 By binding the free water in the extract, reducing the water activity of the acetonitrile phase, and forcing the pesticides to transfer from the water phase to the acetonitrile phase, the pesticide loss can be reduced. The citrate ion binds to the metal ions in the cotton fibers, preventing the formation of metal-pesticide complexes, and can also maintain the pH of the extract in weakly acidic, inhibiting the hydrolysis of acidic or alkaline pesticides, which helps to reduce the pesticide loss. Therefore, through the synergistic effect of sodium sulfate and sodium citrate, the recovery rate of pesticide residues in the process of determining pesticide residues in cotton fibers can be improved. Moreover, it is found in this application that when the proportion of sodium citrate is too low or too high, the recovery rate of pesticide residues will decrease. This may be because when the proportion of sodium citrate is too low, the chelating ability is insufficient, resulting in the phenomenon of metal ion interference. When the proportion of sodium citrate is too high, the volume of the acetonitrile phase decreases, resulting in poor extraction efficiency.

[0017] In a specific feasible implementation, in step S2, diatomaceous earth is added to the extraction reagent, mixed evenly, and then the cotton fiber sample is added to the extraction reagent for extraction.

[0018] By adopting the above technical solution, the porous particle structure of diatomaceous earth can disperse cotton fibers, avoid fiber agglomeration during ultrasonic treatment, increase the solvent contact area, and can also adsorb anionic pigments and polar lipids in cotton fibers, and assist the salting-out agent in dehydration, making the acetonitrile phase clearer. Therefore, the recovery rate of pesticide residues can be further improved.

[0019] In a specific feasible implementation, in step S3, the carbon adsorbent is multi-walled carbon nanotubes or graphitized carbon black.

[0020] By adopting the above technical solutions, the multi-walled carbon nanotubes have a large specific surface area, and the tubular structure provides dual adsorption sites on the inner and outer surfaces, with a large adsorption capacity for pigments, waxes, and polycyclic aromatic hydrocarbons in cotton fibers. The layered structure of graphitized carbon black enhances the adsorption of planar molecules, while the adsorption of non-planar pesticides is weak. Therefore, using multi-walled carbon nanotubes or graphitized carbon black can reduce impurity interference and improve the recovery rate of pesticide residues.

[0021] In a specific feasible implementation, in step S3, after passing the supernatant through a nylon filter membrane with a pore size of 0.20 - 0.25 μm, an adsorbed liquid sample is obtained.

[0022] By adopting the above technical solutions, the filter membrane with the above pore size allows pesticide molecules to pass through freely, which can improve the pesticide recovery rate. The nylon filter membrane is a non-adsorbent material, which can reduce the adsorption loss of pesticide residues.

[0023] In a specific feasible implementation, in step S4, the acetone / n-hexane mixed solution includes acetone and n-hexane with a mass ratio of 1:(0.8 - 1.2).

[0024] By adopting the above technical solutions, acetone dissolves polar pesticides, and n-hexane dissolves non-polar pesticides. The mixing ratio of 1:(0.8 - 1.2) has a polarity between acetone and n-hexane, covering most pesticides, and keeping pesticide molecules stable through the principle of similar solubility, avoiding crystallization or adsorption loss caused by the volatilization of a single solvent.

[0025] In summary, the present application has the following beneficial effects:

[0026] 1. The present application helps to improve the recovery rate of pesticide residues in the process of determining pesticide residues in cotton fibers by improving the extraction effect of pesticide residues in cotton fibers, reducing impurity interference, and reducing the loss of the extracted pesticide residues.

[0027] 2. In the present application, it is preferably to use a non-ionic surfactant and diatomaceous earth, which can further improve the recovery rate of pesticide residues.

[0028] 3. The present application preferably uses sodium sulfate and sodium citrate with a mass ratio of (3 - 5):1. Through the synergistic effect of sodium sulfate and sodium citrate, the recovery rate of pesticide residues in the process of determining pesticide residues in cotton fibers can be improved. Detailed implementation

[0029] Unless otherwise specified, the raw materials and reagents used in this application are all purchased from the market. Among them, quaternary ammonium salt-bonded silica gel (Kepunuo, pore size 60A); octadecylsilane-bonded silica gel (Bangkai Jiaao, pore size 100A); multi-walled carbon nanotubes (Hongwu Nano, diameter 30-60nm, length 1-2um); diatomite (Fe2O3 content ≤ 0.5%, 200 mesh); non-ionic surfactant (AEO-9); graphitized carbon black (N110).

[0030] The following further elaborates on this application in combination with examples and comparative examples.

[0031] Example

[0032] Example 1

[0033] This example provides a method for determining pesticide residues in cotton fibers, which includes the following steps:

[0034] S1. Crush the cotton fibers to a particle size of 0.1-0.5 mm, and after vacuum drying, obtain a cotton fiber sample.

[0035] S2. Mix acetonitrile (analytical pure) and glacial acetic acid (analytical pure) according to a volume ratio of 100:1.2, add sodium sulfate according to a dosage of 1.2 g / 100 mL, and after mixing evenly, obtain an extraction reagent. Add the cotton fiber sample to the extraction reagent, perform ultrasonic oscillation at 320 W and 45 °C for 30 min, centrifuge, and collect the supernatant to obtain an extract sample.

[0036] S3. Add quaternary ammonium salt-bonded silica gel to the extract sample according to a dosage of 0.013 g of quaternary ammonium salt-bonded silica gel per 100 mL of the extract sample, and then add octadecylsilane-bonded silica gel and multi-walled carbon nanotubes according to a mass ratio of quaternary ammonium salt-bonded silica gel, octadecylsilane-bonded silica gel, and multi-walled carbon nanotubes of 10:5:2. After stirring evenly, add anhydrous magnesium sulfate according to a dosage of 4.0 g / 100 mL, continue to stir evenly, centrifuge, and collect the supernatant to obtain an adsorption liquid sample.

[0037] S4. Concentrate the adsorbed liquid sample at a nitrogen flow rate of 5 L / min and 35 °C. After removing the solution, add an acetone / n-hexane mixed solution and stir until uniform to obtain a sample of the test solution. Use liquid chromatography-mass spectrometry to measure the sample of the test solution. The acetone / n-hexane mixed solution includes acetone / n-hexane with a mass ratio of 1:1. Liquid chromatography conditions: The chromatographic column is a C18 column, 2.1 mm × 100 mm, 1.7 μm; the column temperature is 40 °C; the injection volume is 10 μL; mobile phase A is an aqueous formic acid solution with a concentration of 0.1%, and mobile phase B is an acetonitrile formic acid solution with a concentration of 0.1%; the gradient elution program of mobile phase A is as follows: 0 - 2 min, 5%, flow rate 0.3 mL / min; 2 - 8 min, 5 - 30%, flow rate 0.3 - 0.4 mL / min; 8 - 12 min, 30 - 95%, flow rate 0.4 mL / min; 12 - 12.1 min, 95%, flow rate 0.4 mL / min; 12.1 - 15 min, 5%, flow rate 0.4 - 0.3 mL / min; Mass spectrometry conditions: Use an electrospray ionization source, positive ion mode, ion source temperature 250 °C; full scan mode, scanning mass range 50 - 1000 m / z.

[0038] Example 2

[0039] The difference between this example and Example 1 is only that in step S2 of this example: Mix acetonitrile and glacial acetic acid according to a volume ratio of 100:0.5, add sodium sulfate according to a dosage of 1 g / 100 mL, and after mixing evenly, obtain an extraction reagent. Add the cotton fiber sample to the extraction reagent, ultrasonically vibrate at 280 W and 35 °C for 40 min, centrifuge, and collect the supernatant to obtain a sample of the extract.

[0040] Example 3

[0041] The difference between this example and Example 1 is only that in step S2 of this example: Mix acetonitrile and glacial acetic acid according to a volume ratio of 100:1.8, add sodium sulfate according to a dosage of 1.4 g / 100 mL, and after mixing evenly, obtain an extraction reagent. Add the cotton fiber sample to the extraction reagent, ultrasonically vibrate at 350 W and 55 °C for 15 min, centrifuge, and collect the supernatant to obtain a sample of the extract.

[0042] Example 4

[0043] The difference between this embodiment and Embodiment 1 lies only in that in Step S3 of this embodiment: according to the dosage of adding 0.01 g of quaternary ammonium salt-bonded silica gel per 100 mL of the extract sample, add quaternary ammonium salt-bonded silica gel to the extract sample, and then according to the mass ratio of quaternary ammonium salt-bonded silica gel, octadecylsilane-bonded silica gel, and multi-walled carbon nanotubes of 10:6:3, add octadecylsilane-bonded silica gel and multi-walled carbon nanotubes. After stirring until uniform, add anhydrous magnesium sulfate according to the dosage of 3.6 g / 100 mL, continue to stir until uniform, centrifuge, and collect the supernatant to obtain the adsorbed liquid sample.

[0044] Embodiment 5

[0045] The difference between this embodiment and Embodiment 1 lies only in that in Step S3 of this embodiment: according to the dosage of adding 0.015 g of quaternary ammonium salt-bonded silica gel per 100 mL of the extract sample, add quaternary ammonium salt-bonded silica gel to the extract sample, and then according to the mass ratio of quaternary ammonium salt-bonded silica gel, octadecylsilane-bonded silica gel, and multi-walled carbon nanotubes of 10:4:1, add octadecylsilane-bonded silica gel and multi-walled carbon nanotubes. After stirring until uniform, add anhydrous magnesium sulfate according to the dosage of 4.2 g / 100 mL, continue to stir until uniform, centrifuge, and collect the supernatant to obtain the adsorbed liquid sample.

[0046] Embodiment 6

[0047] The difference between this embodiment and Embodiment 1 lies only in that the following is Step S2 of this embodiment: Mix acetonitrile and glacial acetic acid according to a volume ratio of 100:1.2, add sodium sulfate according to the dosage of 1.2 g / 100 mL, and after mixing evenly, obtain the extraction reagent. Add a non-ionic surfactant to the extraction reagent according to the dosage of 0.2 g / mL, and stir until uniform. Then add the cotton fiber sample to the extraction reagent, and perform ultrasonic oscillation at 320 W and 45 °C for 30 min, centrifuge, and collect the supernatant to obtain the extract sample.

[0048] Embodiment 7

[0049] The difference between this embodiment and Embodiment 1 lies only in that in Step S2 of this embodiment: Replace sodium sulfate with an equal amount of sodium citrate.

[0050] Embodiment 8

[0051] The difference between this embodiment and Embodiment 1 lies only in that in Step S2 of this embodiment: Replace sodium sulfate with an equal amount of salting-out agent. The salting-out agent includes sodium sulfate and sodium citrate with a mass ratio of 2:1.

[0052] Embodiment 9

[0053] The difference between this embodiment and Embodiment 1 is only that in step S2 of this embodiment: sodium sulfate is replaced with an equal amount of salting-out agent. The salting-out agent includes sodium sulfate and sodium citrate with a mass ratio of 3:1.

[0054] Embodiment 10

[0055] The difference between this embodiment and Embodiment 1 is only that in step S2 of this embodiment: sodium sulfate is replaced with an equal amount of salting-out agent. The salting-out agent includes sodium sulfate and sodium citrate with a mass ratio of 4:1.

[0056] Embodiment 11

[0057] The difference between this embodiment and Embodiment 1 is only that in step S2 of this embodiment: sodium sulfate is replaced with an equal amount of salting-out agent. The salting-out agent includes sodium sulfate and sodium citrate with a mass ratio of 5:1.

[0058] Embodiment 12

[0059] The difference between this embodiment and Embodiment 1 is only that in step S2 of this embodiment: sodium sulfate is replaced with an equal amount of salting-out agent. The salting-out agent includes sodium sulfate and sodium citrate with a mass ratio of 6:1.

[0060] Embodiment 13

[0061] The difference between this embodiment and Embodiment 1 is only that the S2 step of this embodiment is as follows: Mix acetonitrile and glacial acetic acid according to a volume ratio of 100:1.2, add sodium sulfate according to a dosage of 1.2 g / 100 mL, mix evenly to obtain an extraction reagent. Add diatomaceous earth to the extraction reagent according to a dosage of 0.5 g / mL, add the cotton fiber sample to the extraction reagent, perform ultrasonic oscillation at 320 W and 45 °C for 30 min, centrifuge, and collect the supernatant to obtain an extract sample.

[0062] Embodiment 14

[0063] The difference between this embodiment and Embodiment 1 is only that the S2 step of this embodiment is as follows: Mix acetonitrile and glacial acetic acid according to a volume ratio of 100:1.2, add a salting-out agent according to a dosage of 1.2 g / 100 mL, mix evenly to obtain an extraction reagent. Add a non-ionic surfactant to the extraction reagent according to a dosage of 0.2 g / mL, add diatomaceous earth to the extraction reagent according to a dosage of 0.5 g / mL, add the cotton fiber sample to the extraction reagent, perform ultrasonic oscillation at 320 W and 45 °C for 30 min, centrifuge, and collect the supernatant to obtain an extract sample. The salting-out agent includes sodium sulfate and sodium citrate with a mass ratio of 3:1.

[0064] Embodiment 15

[0065] The difference between this embodiment and Embodiment 1 is only that in step S3 of this embodiment, multi-walled carbon nanotubes are replaced with an equal amount of graphitized carbon black.

[0066] Embodiment 16

[0067] The difference between this embodiment and Embodiment 1 is only that the S3 step of this embodiment is as follows: According to the dosage of adding 0.013 g of quaternary ammonium salt-bonded silica gel per 100 mL of the extract sample, add quaternary ammonium salt-bonded silica gel to the extract sample, and then according to the mass ratio of quaternary ammonium salt-bonded silica gel, octadecylsilane-bonded silica gel, and multi-walled carbon nanotubes of 10:5:2, add octadecylsilane-bonded silica gel and carbon adsorbent. After stirring until uniform, add anhydrous magnesium sulfate according to the dosage of 4.0 g / 100 mL, continue to stir until uniform, centrifuge, collect the supernatant, and after passing the supernatant through a nylon filter membrane with a pore size of 0.20 μm, an adsorbed liquid sample is obtained.

[0068] Embodiment 17

[0069] The difference between this embodiment and Embodiment 1 is only that the S3 step of this embodiment is as follows: According to the dosage of adding 0.013 g of quaternary ammonium salt-bonded silica gel per 100 mL of the extract sample, add quaternary ammonium salt-bonded silica gel to the extract sample, and then according to the mass ratio of quaternary ammonium salt-bonded silica gel, octadecylsilane-bonded silica gel, and multi-walled carbon nanotubes of 10:5:2, add octadecylsilane-bonded silica gel and carbon adsorbent. After stirring until uniform, add anhydrous magnesium sulfate according to the dosage of 4.0 g / 100 mL, continue to stir until uniform, centrifuge, collect the supernatant, and after passing the supernatant through a nylon filter membrane with a pore size of 0.23 μm, an adsorbed liquid sample is obtained.

[0070] Embodiment 18

[0071] The difference between this embodiment and Embodiment 1 is only that the S3 step of this embodiment is as follows: According to the dosage of adding 0.013 g of quaternary ammonium salt-bonded silica gel per 100 mL of the extract sample, add quaternary ammonium salt-bonded silica gel to the extract sample, and then according to the mass ratio of quaternary ammonium salt-bonded silica gel, octadecylsilane-bonded silica gel, and multi-walled carbon nanotubes of 10:5:2, add octadecylsilane-bonded silica gel and carbon adsorbent. After stirring until uniform, add anhydrous magnesium sulfate according to the dosage of 4.0 g / 100 mL, continue to stir until uniform, centrifuge, collect the supernatant, and after passing the supernatant through a nylon filter membrane with a pore size of 0.25 μm, an adsorbed liquid sample is obtained.

[0072] Embodiment 19

[0073] The difference between this embodiment and Embodiment 1 is only that in step S4 of this embodiment, the acetone / n-hexane mixed solution includes acetone / n-hexane with a mass ratio of 1:0.6.

[0074] Embodiment 20

[0075] The difference between this embodiment and Embodiment 1 is only that in step S4 of this embodiment, the acetone / n - hexane mixed solution includes acetone / n - hexane with a mass ratio of 1:0.8.

[0076] Embodiment 21

[0077] The difference between this embodiment and Embodiment 1 is only that in step S4 of this embodiment, the acetone / n - hexane mixed solution includes acetone / n - hexane with a mass ratio of 1:1.2.

[0078] Embodiment 22

[0079] The difference between this embodiment and Embodiment 1 is only that in step S4 of this embodiment, the acetone / n - hexane mixed solution includes acetone / n - hexane with a mass ratio of 1:1.4.

[0080] Comparative Example

[0081] Comparative Example 1

[0082] The difference between this comparative example and Embodiment 1 is only that the step S2 of this comparative example is as follows: Acetonitrile and glacial acetic acid are mixed evenly according to a volume ratio of 100:1.2 to obtain an extraction reagent. The cotton fiber sample is added to the extraction reagent, and ultrasonic oscillation is carried out at 320W and 45°C for 30 min, followed by centrifugation, and the supernatant is collected to obtain an extract sample.

[0083] Comparative Example 2

[0084] The difference between this comparative example and Embodiment 1 is only that the step S2 of this comparative example is as follows: Sodium sulfate is added to acetonitrile according to a dosage of 1.2 g / 100 mL, and after mixing evenly, an extraction reagent is obtained. The cotton fiber sample is added to the extraction reagent, and ultrasonic oscillation is carried out at 320W and 45°C for 30 min, followed by centrifugation, and the supernatant is collected to obtain an extract sample.

[0085] Comparative Example 3

[0086] The difference between this comparative example and Embodiment 1 is only that the step S2 of this comparative example is as follows: Acetonitrile and glacial acetic acid are mixed according to a volume ratio of 100:1.2, and sodium sulfate is added according to a dosage of 1.2 g / 100 mL, and after mixing evenly, an extraction reagent is obtained. The cotton fiber sample is added to the extraction reagent, and left standing at 45°C for 30 min, followed by centrifugation, and the supernatant is collected to obtain an extract sample.

[0087] Comparative Example 4

[0088] The difference between this comparative example and Example 1 is only that the S3 step of this comparative example is as follows: According to the dosage of adding 0.013 g of quaternary ammonium salt-bonded silica gel to every 100 mL of the extract sample, add quaternary ammonium salt-bonded silica gel to the extract sample, stir until uniform, then add anhydrous magnesium sulfate according to the dosage of 4.0 g / 100 mL, continue to stir until uniform, centrifuge, and collect the supernatant to obtain the adsorbed liquid sample.

[0089] Comparative Example 5

[0090] The difference between this comparative example and Example 1 is only that the S3 step of this comparative example is as follows: According to the dosage of adding 0.013 g of quaternary ammonium salt-bonded silica gel to every 100 mL of the extract sample, add quaternary ammonium salt-bonded silica gel to the extract sample, and then add octadecylsilane-bonded silica gel and carbon adsorbent according to the mass ratio of quaternary ammonium salt-bonded silica gel, octadecylsilane-bonded silica gel, and multi-walled carbon nanotubes of 10:5:2, stir until uniform, centrifuge, and collect the supernatant to obtain the adsorbed liquid sample.

[0091] Comparative Example 6

[0092] The difference between this comparative example and Example 1 is only that in the S4 step of this comparative example: directly use the liquid chromatography-mass spectrometry method to measure the sample of the liquid to be adsorbed.

[0093] Performance detection test

[0094] For Examples 1-22 and Comparative Examples 1-6, the following performance detections were carried out:

[0095] Prepare the standard stock solution: Accurately weigh 30 pesticide standard products respectively, dissolve them with acetone to obtain a standard stock solution with a mass concentration of 1000 mg / L for standby. The basic information of the 30 pesticide standard products is shown in Table 1.

[0096] Prepare the mixed pesticide standard stock solution: Take 1.0 mL of the standard stock solution into a 100 mL volumetric flask respectively, dilute with acetone and make the volume constant to a mass concentration of 10.0 mg / L to obtain the mixed pesticide standard stock solution for standby.

[0097] Spiking experiment design: Select blank cotton fibers not contaminated by the target pesticides as the measurement object, conduct a spiking recovery experiment on the blank cotton fibers, set 3 groups of comparative experiments, and the spiking concentrations of the 3 groups of comparative experiments are 10, 50, and 100 mg / kg respectively, with at least 3 parallels for each spiking concentration. The spiking method is as follows: Weigh 2.00 g of blank cotton fibers into a centrifuge tube, accurately add the mixed pesticide standard stock solution with a micro syringe, let it stand for 10 minutes, take out the cotton fibers, and complete the spiking.

[0098] The labeled cotton fibers were measured according to each example and comparative example, and then the pesticide residue recovery rate of each spiked concentration was calculated according to the formula: recovery rate = measured concentration ÷ spiked concentration × 100%, and then the average value of the pesticide residue recovery rates of the 3 spiked concentrations was calculated as the average recovery rate.

[0099] The test results are shown in Table 2.

[0100] Table 1

[0101]

[0102]

[0103] Table 2

[0104]

[0105]

[0106] Combining Example 1 and Comparative Examples 1-6 and referring to Table 1, it can be seen that compared with Example 1, the average recovery rates of Comparative Examples 1-6 are significantly reduced and less than 70%. This shows that adopting the measurement method of Example 1 helps to improve the recovery rate of pesticide residues in cotton fibers.

[0107] Combining Examples 1-6 and referring to Table 1, it can be seen that the average recovery rates of Examples 1-6 are between 88% and 93%, and the difference between the maximum value and the minimum value is within 5%. This shows that adopting the measurement methods within the process conditions of Examples 1-6 can improve the recovery rate of pesticide residues in cotton fibers, and moreover, the recovery rate is relatively stable.

[0108] Combining Example 1 and Examples 7-22 and referring to Table 1, it can be seen that the recovery rates of Examples 7-22 are all between 87% and 96%. This shows that adopting the measurement methods within the process conditions of Examples 7-22 can also improve the recovery rate of pesticide residues in cotton fibers.

[0109] Moreover, by comparing the average recovery rates, it can be known that Example 8 < Example 12 < Example 9 < Example 11 < Example 10, while the proportion of sodium citrate in the salting-out agent is Example 12 < Example 11 < Example 10 < Example 9 < Example 8. This shows that too low or too high a proportion of sodium citrate will lead to a decrease in the recovery rate. Moreover, when the mass ratio of sodium sulfate to sodium citrate is (3-5):1, it helps to improve the recovery rate.

[0110] By comparing the average recovery rates, it can be known that in Step S2, adding diatomaceous earth and non-ionic surfactant can further improve the recovery rate.

[0111] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for determining pesticide residues in cotton fiber, characterized in that: The following technical solutions are adopted: S1. Crush and dry cotton fibers to obtain cotton fiber samples; S2, acetonitrile and glacial acetic acid are mixed in a volume ratio of 100: (0.5-1.8), a salting-out agent is added in an amount of 1-1.4 g / 100 mL, and the mixture is evenly mixed to obtain an extraction reagent, and the cotton fiber sample is added to the extraction reagent for extraction, ultrasonically shaken at 280-350 W and 35-55 ° C for 15-40 min, centrifuged, and the supernatant is collected to obtain an extract sample; S3, add quaternary ammonium salt bonded silica gel, octadecylsilane bonded silica gel and carbon adsorbent to the extract sample, mix well, add anhydrous magnesium sulfate in an amount of 3.6-4.2g / 100mL, mix well, centrifuge, collect the supernatant, and obtain an adsorption liquid sample; the addition amount of quaternary ammonium salt bonded silica gel in every 100mL extract sample is 0.01-0.015g, and the mass ratio of the quaternary ammonium salt bonded silica gel, octadecylsilane bonded silica gel and carbon adsorbent is 10:(4-6):(1-3); S4. Concentrate the adsorption liquid sample, remove the solution, and evenly mix it with an acetone / n-hexane mixed solution to obtain a liquid sample to be tested. Use a liquid chromatography-mass spectrometry method to measure the liquid sample to be tested.

2. The method for determining pesticide residues in cotton fibers according to claim 1, characterized in that: In step S2, a nonionic surfactant is added to the extraction reagent, mixed evenly, and then the cotton fiber sample is added to the extraction reagent for extraction.

3. The method for determining pesticide residues in cotton fibers according to claim 2, characterized in that: In step S2, diatomaceous earth is added to the extraction reagent and mixed evenly, and then the cotton fiber sample is added to the extraction reagent for extraction.

4. The method for determining pesticide residues in cotton fibers according to claim 1, characterized in that: The salting-out agent comprises sodium sulfate and sodium citrate in a mass ratio of (3-5):

1.

5. The method for determining pesticide residues in cotton fiber according to claim 1, characterized in that: In step S3, the carbon adsorbent is multi-walled carbon nanotubes or graphitized carbon black.

6. The method for determining pesticide residues in cotton fibers according to claim 1, characterized in that: In step S3, the supernatant is filtered through a nylon filter membrane with a pore size of 0.20-0.25 μm to obtain an adsorption liquid sample.

7. The method for determining pesticide residues in cotton fibers according to claim 1, characterized in that: In step S4, the acetone / n-hexane mixed solution comprises acetone and n-hexane in a mass ratio of 1:(0.8-1.2).

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