Preparation method of solid-phase extraction filler special for carboxylic acid herbicide

Abstract

The application discloses a preparation method of a solid-phase extraction filler special for carboxylic acid herbicides, and the method comprises the following steps: firstly, modifying a template molecular composition into a polymerizable monomer through esterification, then bonding the polymerizable monomer into a cross-linked polymer, and finally hydrolyzing and removing the template molecular composition to obtain the solid-phase extraction filler special for carboxylic acid herbicides. The solid-phase extraction filler special for carboxylic acid herbicides provided by the application has the advantages of good specificity adsorption for carboxylic acid herbicides, high detection sensitivity, complete impurity removal, good stability of the filler, high strength, strong chemical resistance, and the like. Meanwhile, the template molecular composition does not belong to the detected molecules, and a small amount of residual template molecular composition does not affect the detection, so that the problems of low purification efficiency and easy pollution of the sample inlet of a chromatograph in the prior art, which affect the detection effect, are solved.

Description

Technical Field

[0001] This invention belongs to the field of analytical detection technology, specifically relating to a method for preparing a solid-phase extraction packing material for carboxylic acid herbicides. Background Technology

[0002] Carboxylic acid herbicides are a class of herbicides containing carboxylic acid groups and are commonly used. While their weed-control mechanisms are diverse, all carboxylic acid herbicides pose a certain degree of toxicity to humans and animals after application. The degradation and removal of carboxylic acid herbicides require sufficient time. To monitor and regulate the use of carboxylic acid herbicides and reduce their harm to humans, animals, and the environment, technicians have conducted extensive work in the field of herbicide detection and removal, developing various standard methods for the detection of carboxylic acid herbicide residues. Examples include "NY / T 1434-2007 Determination of Multiple Residues of 13 Herbicides including 2,4-D in Vegetables by Liquid Chromatography-Mass Spectrometry" and "GB / T23200.4-2016 National Food Safety Standard for Herbicide Residue Determination Method Part 4: Gas Chromatography-Mass Spectrometry / Mass Spectrometry for the Determination of Aromatic Oxyphenoxypropionate Herbicide Residues in Food".

[0003] In the prior art, CN109283276A discloses a gas chromatography method for determining the residues of eight phenoxycarboxylic acid herbicides in corn. Specifically, it discloses extraction with an alkaline 10% acetone aqueous solution, enrichment of the target compound in the extract with a novel p-toluenesulfonate-magnesium aluminum type hydrotalcite calcination product adsorbent, complete elution of the target compound by acid dissolution of the adsorbent, efficient extraction of the compound with a small dose of organic solvent, and rapid analysis and determination by gas chromatography after derivatization. The method of this patent uses an acidic eluent to elute the target compound, which may also elute acidic impurities in the extract, resulting in low purification efficiency and potentially affecting the detection results.

[0004] Patent CN110387019A discloses a method for preparing a molecularly imprinted polymer for removing 2,4-dichlorophenoxyacetic acid pesticide residues and its application. The method involves reacting 3-aminopropyltriethoxysilane with isobutyryl bromide to obtain APTES-Br; hydrolyzing APTES-Br with tetraethyl orthosilicate under the action of ammonia to obtain silica nanospheres with an ATRP initiator on the surface; and using vinylpyridine ionic liquid as the functional monomer, 2,4-dichlorophenoxyacetic acid as the template molecule, ethylene glycol dimethacrylate as the crosslinking agent, and tris(2-dimethylamino)amine as the ligand, the polymer is prepared by ATRP polymerization under the initiation of cuprous chloride. The use of 2,4-dichlorophenoxyacetic acid as a template molecule in this scheme is not designed for pesticide residue detection. If the polymer is used for residue detection, all 2,4-dichlorophenoxyacetic acid template molecules must be completely removed, which places extremely high demands on the preparation of molecularly imprinted polymers and takes a very long time.

[0005] Patent CN114570299A discloses a method for preparing an artificial antibody for 2,4-D detection. The method involves using 2,4-D as the imprinted molecule, adding functional monomers, cross-linking agents, and initiators to prepare a 2,4-D magnetic molecularly imprinted polymer. The 2,4-D molecules located in the imprinted shell are eluted with an elution buffer. The eluted artificial antibody possesses a specific recognition site for enzyme-labeled 2,4-D, achieving selective recognition of the enzyme-labeled 2,4-D. Finally, a chemiluminescent substrate is added to achieve trace detection of 2,4-D. However, this method still uses the target pesticide molecule as a template, and trace residues of the template molecule in the molecularly imprinted polymer may severely affect the detection results.

[0006] Existing detection methods have the following problems: 1. Since herbicides target plants, the extraction step in residue detection may introduce a large amount of impurities such as chlorophyll, cellulose, protein, and pectin. The purification principle of dispersion solid-phase extraction is that the solid-phase extraction packing material adsorbs impurities and pigments in the solution to be purified, resulting in low purification efficiency. 2. Extensive testing practice has shown that the headspace inlet of gas chromatographs often accumulates a large amount of solid impurities such as pigments, requiring frequent cleaning, which seriously affects the detection cycle and sometimes even affects the detection results due to contamination of the inlet. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention provides a solid-phase extraction (SPE) packing material specifically for carboxylic acid herbicides and its preparation method. The SPE packing material is a core-shell structured spherical cross-linked polymer. The core layer is essentially free of template molecule voids, while the voids are almost entirely located in the outer shell. During residue detection, a small amount of eluent can be used for complete elution while ensuring sufficient adsorption of the carboxylic acid herbicide. Based on the principle of molecular imprinting, the template molecule composition is structurally and volutely similar to the target carboxylic acid herbicide. After ester hydrolysis, the template molecule composition detaches from the polymer, and after solvent extraction, the polymer forms voids. This results in good specificity for carboxylic acid herbicides, high detection sensitivity, thorough impurity removal, good packing stability, high strength, and strong chemical resistance. Furthermore, the template molecule composition is not part of the target molecule, and a small amount of residual template molecule composition does not affect detection.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing a solid-phase extraction packing material specifically for carboxylic acid herbicides includes the following steps:

[0010] S1. By weight, add 15 parts of carboxylic acid compound, 8-9.5 parts of enyl alcohol and 0.1-0.12 parts of hydroquinone to a reaction vessel, add 40-60 parts of methylcyclohexane and 2-2.6 parts of catalyst, heat to 75-85℃, react for 4-7 hours until no water is generated; cool to 20-30℃, filter to remove catalyst, wash catalyst with 10-15 parts of methylcyclohexane, combine the washing liquid with the filtrate, and remove methylcyclohexane and excess enyl alcohol by vacuum distillation at 70℃; cool to 20-30℃, add 30-35 parts of saturated sodium bicarbonate aqueous solution, shake to remove hydroquinone; let stand to remove aqueous phase, wash organic phase 3 times with 300 parts of deionized water, discard aqueous phase, and obtain enyl alcohol modified monomer composition;

[0011] S2. By weight, mix and dissolve 100 parts styrene, 5-10 parts crosslinking agent, and 0.5-1.2 parts initiator to obtain oil phase A; mix and dissolve 4-6 parts of the enyl alcohol modified monomer composition, 10-15 parts styrene, 10-15 parts crosslinking agent, and 10-15 parts vinyl acetate to obtain oil phase B; add 30-40 parts of 0.25% sodium dodecyl sulfate aqueous solution and stir at 800-1000 rpm for 0.5-1 hour to obtain oil phase B; mix 4-6 parts of polyethylene glycol... Enol 1788 and 10-15 parts of sodium chloride were dissolved in 400-500 parts of deionized water. Oil phase A was added, and the mixture was stirred at 1200-1500 rpm and heated to 60-70°C. After maintaining the temperature for 2-3 hours, oil phase B was added dropwise to the reactor over 2-4 hours. After the addition was completed, the mixture was kept at the same temperature for 3-5 hours and then cooled to 20-30°C. The polymer spheres were washed three times with 300 parts of deionized water, dried at 60°C, and sieved to obtain 400-1000 mesh microspheres, thus obtaining cross-linked polymer microspheres.

[0012] S3. By weight, add 10 parts of polymer microspheres to 160-180 parts of 24% sodium hydroxide solution, heat to 90-100℃, react for 3-5 hours, cool to 20-30℃, wash with deionized water until neutral, extract with a mixed solvent of 400 parts of ethanol, toluene and acetic acid under boiling conditions for 10-12 hours, wash the microspheres with 200 parts of ethanol, wash with deionized water until neutral, and vacuum dry at 60℃ to obtain solid phase extraction packing material for carboxylic acid herbicides.

[0013] Further, in step S1, the carboxylic acid compound is a combination of at least three of the following: 5-(2,4-dichlorophenyl)-2-furoic acid, 4-(3,4-dichlorophenyl)-4-phenylbutyric acid, 2-(2,4-dichlorophenyl)thiazol-4-carboxylic acid, 3-amino-4-(3,5-dichlorophenyl)butyric acid, 3-(3-(2,4,5-trichlorophenyl)ureoyl)benzoic acid, or 5-(3,4-dichlorophenyl)nicotinic acid.

[0014] Furthermore, in step S1, the alkenyl alcohol is one of allyl alcohol and 2-methyl-2-propen-1-ol.

[0015] Furthermore, in step S1, the catalyst is a macroporous strong acid cation exchange resin, which is pre-washed with ethanol and dried to remove moisture before use.

[0016] Furthermore, in step S2, the crosslinking agent is one or a combination of several of the following: 80% divinylbenzene, N-methyldiallylamine, and ethylene glycol diallyl ether.

[0017] Furthermore, in step S2, the initiator is either dodecyl peroxide or azobisisobutyronitrile.

[0018] Furthermore, in step S3, the volume ratio of ethanol, toluene, and acetic acid in the mixed solvent is 2:8:1.

[0019] Furthermore, solid-phase extraction packing material specifically for carboxylic acid herbicides is applied to the residue detection of aryloxycarboxylic acid and arylformic acid herbicides in food and agricultural products.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The core of the solid-phase extraction packing material for carboxylic acid herbicides described in this invention is mainly composed of a polymer of styrene and a crosslinking agent, and essentially contains no voids formed by the template molecule composition. The outer shell is mainly composed of styrene, vinyl alcohol, a crosslinking agent, an alkenyl alcohol, and voids formed by the template molecule composition. The molecular structure and volume of the polymer template molecule composition are similar to those of carboxylic acid herbicides. The template molecule composition is not the molecule to be detected. After alkaline hydrolysis and solvent extraction, the polymer in the solid-phase extraction packing material forms voids. Incomplete extraction does not affect detection. During residue detection, impurities can be thoroughly washed away while ensuring adsorption of the target analyte, and complete elution can be achieved with a smaller amount of eluent, reducing solvent consumption and shortening the detection cycle.

[0022] 2. The outer shell of the solid-phase extraction packing material for carboxylic acid herbicides described in this invention contains hydroxyl groups left after hydrolysis of vinyl acetate and alkenyl alcohol modified monomers, which improves the hydrophilicity of the packing surface and makes it more compatible with the extract for residue detection, thus facilitating the adsorption of the target herbicide in the solid-phase extraction packing material for carboxylic acid herbicides.

[0023] 3. The solid-phase extraction filler for carboxylic acid herbicides described in this invention refers to the principle of molecular imprinting, which has good specificity for carboxylic acid herbicides, high detection sensitivity, thorough impurity removal, minimal impact on detection equipment, good stability, high strength, strong chemical resistance, does not contain the substance to be detected, and does not affect residue detection.

[0024] Figure Labels

[0025] Figure 1 This is a scanning electron microscope image of the solid-phase extraction packing material for carboxylic acid herbicides in Example 1 of the present invention;

[0026] Figure 2 The liquid chromatograms of 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, 2,4-dichlorophenoxypropionic acid and dichloroquinoline acid in spinach sample 8 are shown.

[0027] Figure 3 This is a picture of the appearance of the liquid after purification of spinach sample No. 8-25. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0029] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0030] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0031] A method for preparing a solid-phase extraction packing material specifically for carboxylic acid herbicides includes the following steps:

[0032] S1. By weight, add 15 parts of carboxylic acid compound, 8-9.5 parts of enyl alcohol and 0.1-0.12 parts of hydroquinone to a reaction vessel, add 40-60 parts of methylcyclohexane and 2-2.6 parts of catalyst, heat to 75-85℃, react for 4-7 hours until no water is generated; cool to 20-30℃, filter to remove catalyst, wash catalyst with 10-15 parts of methylcyclohexane, combine the washing liquid with the filtrate, and remove methylcyclohexane and excess enyl alcohol by vacuum distillation at 70℃; cool to 20-30℃, add 30-35 parts of saturated sodium bicarbonate aqueous solution, shake to remove hydroquinone; let stand to remove aqueous phase, wash organic phase 3 times with 300 parts of deionized water, discard aqueous phase, and obtain enyl alcohol modified monomer composition;

[0033] S2. By weight, mix and dissolve 100 parts styrene, 5-10 parts crosslinking agent, and 0.5-1.2 parts initiator to obtain oil phase A; mix and dissolve 4-6 parts of the enyl alcohol modified monomer composition, 10-15 parts styrene, 10-15 parts crosslinking agent, and 10-15 parts vinyl acetate to obtain oil phase B; add 30-40 parts of 0.25% sodium dodecyl sulfate aqueous solution and stir at 800-1000 rpm for 0.5-1 hour to obtain oil phase B; mix 4-6 parts of polyethylene glycol... Enol 1788 and 10-15 parts of sodium chloride were dissolved in 400-500 parts of deionized water. Oil phase A was added, and the mixture was stirred at 1200-1500 rpm and heated to 60-70°C. After maintaining the temperature for 2-3 hours, oil phase B was added dropwise to the reactor over 2-4 hours. After the addition was completed, the mixture was kept at the same temperature for 3-5 hours and then cooled to 20-30°C. The polymer spheres were washed three times with 300 parts of deionized water, dried at 60°C, and sieved to obtain 400-1000 mesh microspheres, thus obtaining cross-linked polymer microspheres.

[0034] S3. By weight, add 10 parts of polymer microspheres to 160-180 parts of 24% sodium hydroxide solution, heat to 90-100℃, react for 3-5 hours, cool to 20-30℃, wash with deionized water until neutral, extract with a mixed solvent of 400 parts of ethanol, toluene and acetic acid under boiling conditions for 10-12 hours, wash the microspheres with 200 parts of ethanol, wash with deionized water until neutral, and vacuum dry at 60℃ to obtain solid phase extraction packing material for carboxylic acid herbicides.

[0035] Example 1:

[0036] A method for preparing a solid-phase extraction packing material specifically for carboxylic acid herbicides includes the following steps:

[0037] S1. 3.5g of 5-(2,4-dichlorophenyl)-2-furfuric acid, 5.5g of 3-amino-4-(3,5-dichlorophenyl)butyric acid, 2g of 4-(3,4-dichlorophenyl)-4-phenylbutyric acid, and 4g of... 2-(2,4-Dichlorophenyl)thiazol-4-carboxylic acid, 8g allyl alcohol, and 0.1g hydroquinone were added to a reaction vessel, followed by 60g methylcyclohexane and 2.6g catalyst macroporous strong acid cation exchange resin. The mixture was heated to 75°C and reacted for 7 hours until no anhydrous substances were formed. The temperature was then lowered to 20°C, and the catalyst was removed by filtration. The catalyst was washed with 15g methylcyclohexane, and the washings were combined with the filtrate. The methylcyclohexane and excess allyl alcohol were removed by vacuum distillation at 70°C. The temperature was then lowered to 20°C, and 35g saturated sodium bicarbonate aqueous solution was added. The hydroquinone was removed by shaking. The aqueous phase was removed by standing, and the organic phase was washed three times with 300g deionized water. The aqueous phase was discarded, yielding the reactive template molecular composition.

[0038] S2. Mix and dissolve 100g styrene, 10g ethylene glycol diallyl ether, and 1.2g initiator dodecyl peroxide to obtain oil phase A. Mix and dissolve 6g reactive template molecular composition, 15g styrene, 15g ethylene glycol diallyl ether, and 10g vinyl acetate to obtain oil phase B. Add 40g of 0.25% sodium dodecyl sulfate aqueous solution and stir at 800rpm for 1 hour to obtain oil phase B. Dissolve 6g polyvinyl alcohol 1788 and 15g sodium chloride in 500g deionized water and add oil phase A. Stir at 1200rpm and heat to 60℃. After holding at this temperature for 3 hours, add oil phase B dropwise to the reactor over 4 hours. After the addition is complete, hold at this temperature for 5 hours and then cool to 20℃. Wash the polymer balls three times with 300g deionized water, dry at 60℃, and sieve to obtain 400-1000 mesh microspheres, thus obtaining cross-linked polymer microspheres.

[0039] S3. Add 10g of polymer microspheres to 160g of 24% sodium hydroxide solution, heat to 100℃, react for 3 hours, cool to 30℃, wash with deionized water until neutral, extract with a mixed solvent of 400g of ethanol, toluene and acetic acid under boiling conditions for 10 hours, wherein the volume ratio of ethanol, toluene and acetic acid in the mixed solvent is 2:8:1, wash the microspheres with 200g of ethanol, then wash with deionized water until neutral, and vacuum dry at 60℃ to obtain a solid phase extraction packing material for carboxylic acid herbicides.

[0040] Example 2:

[0041] A method for preparing a solid-phase extraction packing material specifically for carboxylic acid herbicides includes the following steps:

[0042] S1. Add 9g of 5-(2,4-dichlorophenyl)-2-furoic acid, 5g of 4-(3,4-dichlorophenyl)-4-phenylbutyric acid, 1g of 3-(3-(2,4,5-trichlorophenyl)ureo)benzoic acid, 9.5g of 2-methyl-2-propen-1-ol, and 0.12g of hydroquinone to a reaction vessel. Add 40g of methylcyclohexane and 2g of macroporous strong acid cation exchange resin catalyst. Heat to 85℃ and react for 4 hours until no anhydrous substances are formed. Cool to 30℃, filter to remove the catalyst, wash the catalyst with 10g of methylcyclohexane, combine the washings with the filtrate, and remove methylcyclohexane and excess 2-methyl-2-propen-1-ol by vacuum distillation at 70℃. Cool to 30℃, add 30g of saturated sodium bicarbonate aqueous solution, and shake to remove hydroquinone. The aqueous phase was removed by allowing the mixture to stand. The organic phase was then washed three times with 300g of deionized water, and the aqueous phase was discarded. A 2-methyl-2-propen-1-ol modified monomer composition was obtained.

[0043] S2. Mix and dissolve 100g styrene, 5g 80% divinylbenzene, and 0.5g initiator azobisisobutyronitrile to obtain oil phase A. Mix and dissolve 4g 2-methyl-2-propen-1-ol modified monomer composition, 10g styrene, 10g 80% divinylbenzene, and 15g vinyl acetate to obtain oil phase B. Add 30g 0.25% sodium dodecyl sulfate aqueous solution and stir at 1000rpm for 0.5 hours to obtain oil phase B. Dissolve 4g polyvinyl alcohol 1788 and 10g sodium chloride in 400g deionized water and add oil phase A. Stir at 1500rpm and heat to 70℃. After holding at this temperature for 2 hours, add oil phase B dropwise to the reactor over the next 2 hours. After the addition is complete, hold at this temperature for 3 hours and then cool to 30℃. Wash the polymer spheres three times with 300g deionized water, dry at 60℃, and sieve. Take 400-1000 mesh microspheres to obtain cross-linked polymer microspheres.

[0044] S3. Add 10g of polymer microspheres to 170g of 24% sodium hydroxide solution, heat to 90℃, react for 5 hours, cool to 25℃, wash with deionized water until neutral, extract with a mixed solvent of 400g of ethanol, toluene and acetic acid under boiling conditions for 10 hours, wherein the volume ratio of ethanol, toluene and acetic acid in the mixed solvent is 2:8:1, wash the microspheres with 200g of ethanol, then wash with deionized water until neutral, and vacuum dry at 60℃ to obtain a solid phase extraction packing material for carboxylic acid herbicides.

[0045] Example 3:

[0046] A method for preparing a solid-phase extraction packing material specifically for carboxylic acid herbicides includes the following steps:

[0047] S1. Add 5g of 4-(3,4-dichlorophenyl)-4-phenylbutyric acid, 8.5g of 2-(2,4-dichlorophenyl)thiazol-4-carboxylic acid, 1.5g of 3-(3-(2,4,5-trichlorophenyl)ureo)benzoic acid, 9g of 2-methyl-2-propen-1-ol, and 0.11g of hydroquinone to a reaction vessel, add 50g of methylcyclohexane, add 2.2g of catalyst macroporous strong acid cation exchange resin, heat to 80℃, react for 5 hours until no water is generated; cool to 25℃, filter to remove the catalyst, wash the catalyst with 13g of methylcyclohexane, combine the washing liquid with the filtrate, and remove methylcyclohexane and excess 2-methyl-2-propen-1-ol by vacuum distillation at 70℃. Cool to 30°C, add 33g of saturated sodium bicarbonate aqueous solution, shake to remove hydroquinone, let stand to remove the aqueous phase, wash the organic phase 3 times with 300g of deionized water, discard the aqueous phase, and obtain the 2-methyl-2-propen-1-ol modified monomer composition.

[0048] S2. Mix and dissolve 100g styrene, 7g N-methyldiallylamine, and 0.7g initiator azobisisobutyronitrile to obtain oil phase A. Mix and dissolve 5g 2-methyl-2-propen-1-ol modified monomer composition, 12.5g styrene, 11g N-methyldiallylamine, and 14g vinyl acetate to obtain oil phase B. Add 30-40g of 0.25% sodium dodecyl sulfate aqueous solution and stir at 900rpm for 1 hour to obtain oil phase B. Dissolve 5g polyvinyl alcohol 1788 and 12.5g sodium chloride in 450g deionized water and add oil phase A. Stir at 1300rpm and heat to 68℃. After holding at this temperature for 2.5 hours, add oil phase B dropwise to the reactor over 3 hours. After the addition is complete, hold at this temperature for 4 hours and then cool to 25℃. Wash the polymer balls three times with 300g deionized water, dry at 60℃, and sieve to obtain 400-1000 mesh microspheres, thus obtaining cross-linked polymer microspheres.

[0049] S3. Add 10g of polymer microspheres to 165g of 24% sodium hydroxide solution, heat to 95℃, react for 4 hours, cool to 28℃, wash with deionized water until neutral, extract with a mixed solvent of 400g of ethanol, toluene and acetic acid under boiling conditions for 12 hours, wherein the volume ratio of ethanol, toluene and acetic acid in the mixed solvent is 2:8:1, wash the microspheres with 200g of ethanol, then wash with deionized water until neutral, and vacuum dry at 60℃ to obtain a solid phase extraction packing material for carboxylic acid herbicides.

[0050] Example 4:

[0051] A method for preparing a solid-phase extraction packing material specifically for carboxylic acid herbicides includes the following steps:

[0052] S1. Add 2g of 3-(3-(2,4,5-trichlorophenyl)ureoyl)benzoic acid, 3g of 4-(3,4-dichlorophenyl)-4-phenylbutyric acid, 5g of 2-(2,4-dichlorophenyl)thiazol-4-carboxylic acid, 1g of 3-amino-4-(3,5-dichlorophenyl)butyric acid, 4g of 5-(3,4-dichlorophenyl)nicotinic acid, 8.5g of allyl alcohol, and 0.1g of hydroquinone to a reaction vessel. Add 40g of methylcyclohexane and 2g of catalyst macroporous strong acid cation exchange resin. Heat to 78°C and react for 6 hours until no water is generated. Cool to 25°C, filter to remove the catalyst, wash the catalyst with 15g of methylcyclohexane, combine the washings with the filtrate, and remove methylcyclohexane and excess allyl alcohol by vacuum distillation at 70°C. Cool to 25°C, add 30g of saturated sodium bicarbonate aqueous solution, and shake to remove hydroquinone. After standing to remove the aqueous phase, the organic phase was washed three times with 300g of deionized water, and the aqueous phase was discarded to obtain a reactive template molecule composition.

[0053] S2. Mix and dissolve 100g styrene, 8g ethylene glycol diallyl ether, and 0.9g initiator dodecyl peroxide to obtain oil phase A. Mix and dissolve 5.5g reactive template molecular composition, 15g styrene, 10g ethylene glycol diallyl ether, and 13g vinyl acetate to obtain oil phase B. Add 33g of 0.25% sodium dodecyl sulfate aqueous solution and stir at 1000rpm for 0.5 hours to obtain oil phase B. Dissolve 4.5g polyvinyl alcohol 1788 and 11g sodium chloride in 480g deionized water and add oil phase A. Stir at 1250rpm and heat to 65℃. After holding at this temperature for 2.5 hours, add oil phase B dropwise to the reactor over 3 hours. After the addition is complete, hold at this temperature for 4 hours and then cool to 30℃. Wash the polymer balls three times with 300g deionized water, dry at 60℃, and sieve to obtain 400-1000 mesh microspheres, thus obtaining cross-linked polymer microspheres.

[0054] S3. Add 10g of polymer microspheres to 180g of 24% sodium hydroxide solution, heat to 100℃, react for 3 hours, cool to 24℃, wash with deionized water until neutral, extract with a mixed solvent of 400g of ethanol, toluene and acetic acid under boiling conditions for 11 hours, wherein the volume ratio of ethanol, toluene and acetic acid in the mixed solvent is 2:8:1, wash the microspheres with 200g of ethanol, then wash with deionized water until neutral, and vacuum dry at 60℃ to obtain a solid phase extraction packing material for carboxylic acid herbicides.

[0055] Comparative Example 1:

[0056] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not use a reactive template molecular composition, but uses an equal amount of styrene instead of the reactive template molecular composition. The remaining raw materials and preparation process are the same as in Example 1. The preparation method includes the following steps:

[0057] S1. Mix and dissolve 100g styrene, 10g ethylene glycol diallyl ether, and 1.2g initiator dodecyl peroxide to obtain oil phase A; mix and dissolve 21g styrene, 15g ethylene glycol diallyl ether, and 10g vinyl acetate to obtain oil phase B; add 40g of 0.25% sodium dodecyl sulfate aqueous solution and stir at 800rpm for 1 hour to obtain oil phase B; dissolve 6g polyvinyl alcohol 1788 and 15g sodium chloride in 500g deionized water, add oil phase A, stir at 1200rpm and heat to 60℃, keep at this temperature for 3 hours, then add oil phase B dropwise to the reactor over 4 hours; keep at this temperature for 5 hours after the addition is complete, then cool to 20℃; wash the polymer balls three times with 300g deionized water, dry at 60℃ and sieve to obtain 400-1000 mesh microspheres, thus obtaining cross-linked polymer microspheres;

[0058] S2. Add 10g of polymer microspheres to 160g of 24% sodium hydroxide solution, heat to 100℃, react for 3 hours, cool to 30℃, wash with deionized water until neutral, extract with a mixed solvent of 400g of ethanol, toluene and acetic acid in a volume ratio of 2:8:1 under boiling conditions for 10 hours, wash the microspheres with 200g of ethanol, wash with deionized water until neutral, and vacuum dry at 60℃ to obtain the comparative solid phase extraction packing.

[0059] Example 6:

[0060] Comparative tests were conducted using the packing material of Example 1 of this invention, the packing material of Comparative Example 1, and a conventional solid-phase extraction column. The pretreatment and instrument conditions for the comparative tests are described below:

[0061] Preparation of a solid-phase extraction column for carboxylic acid herbicides: The solid-phase extraction packing material for carboxylic acid herbicides prepared in Example 1 consists of spherical polydisperse particles with a very small amount of fragments. Its regular morphology is advantageous for the adsorption and elution of the target analyte during detection. The scanning electron microscope image of the solid-phase extraction packing material for carboxylic acid herbicides is shown below. Figure 1 As shown, 150 mg of the solid-phase extraction packing material for carboxylic acid herbicides from Example 1 was weighed and added to a 6 mL empty column. The solid-phase extraction packing material for carboxylic acid herbicides was located between two sintered polypropylene gaskets. The packing material was gently tapped to make it as uniform and compact as possible, thus obtaining the solid-phase extraction column for carboxylic acid herbicides.

[0062] Preparation of the comparative solid-phase extraction column: The steps are the same as those for the solid-phase extraction column for carboxylic acid herbicides, but the solid-phase extraction packing material obtained in the comparative example is used as the solid-phase extraction packing material to obtain the comparative solid-phase extraction column;

[0063] Conventional solid-phase extraction column: Add 250mg of graphitized carbon black packing and 200mg of amine packing to a 6mL empty column. The packing is located between two sintered polypropylene gaskets. Gently tap to make the packing as uniform and compact as possible to obtain a conventional solid-phase extraction column. A commercially available solid-phase extraction column with the same packing can also be used for conventional solid-phase extraction columns.

[0064] Preparation of mixed standard curve solution:

[0065] a) Accurately weigh 10.0 mg of 2,4-dichlorophenoxyacetic acid standard after purity conversion, dissolve it in acetonitrile and dilute to 100.0 mL, mix well to obtain a 100.0 mg / L 2,4-dichlorophenoxyacetic acid standard stock solution, store at -20℃ protected from light, shelf life is 6 months;

[0066] b) Accurately weigh 10.0 mg of 2,4-dichlorophenoxypropionic acid standard after purity conversion, dissolve it in acetonitrile and dilute to 100.0 mL, mix well to obtain 100.0 mg / L 2,4-dichlorophenoxypropionic acid standard stock solution, store at -20℃ protected from light, shelf life is 6 months;

[0067] c) Accurately weigh 10.0 mg of 2-methyl-4-chlorophenoxyacetic acid standard after purity conversion, dissolve it in acetonitrile and dilute to 100.0 mL, mix well to obtain a 100.0 mg / L 2-methyl-4-chlorophenoxyacetic acid standard stock solution, store at -20℃ protected from light, shelf life is 6 months;

[0068] d) Accurately weigh 10.0 mg of dichloroquinoline acid standard after purity conversion, dissolve it in acetonitrile and dilute to 100.0 mL, mix well to obtain 100.0 mg / L dichloroquinoline acid standard stock solution, store at -20℃ protected from light, shelf life is 6 months;

[0069] e) Accurately measure 1.00 mL of 2,4-dichlorophenoxyacetic acid standard stock solution, 1.00 mL of 2,4-dichlorophenoxypropionic acid standard stock solution, 1.00 mL of 2-methyl-4-chlorophenoxyacetic acid standard stock solution, and 1.00 mL of dichloroquinoline acid standard stock solution, add them together to a 100 mL volumetric flask, dilute to volume with 50 wt% acetonitrile-water, mix well to obtain a 1.00 mg / L mixed standard solution. This mixed standard solution should be prepared and used immediately.

[0070] f) Accurately measure 2.00 mL of the 1.00 mg / L mixed standard solution and dilute to 10.00 mL with 50 wt% acetonitrile water. Take 0 mL, 0.05 mL, 0.10 mL, 0.25 mL, 0.40 mL, 0.50 mL and 1.00 mL of the mixed standard solution respectively, and add 1.00 mL, 0.95 mL, 0.90 mL, 0.75 mL, 0.60 mL, 0.50 mL and 0 mL of 50 wt% acetonitrile water respectively. Mix well to obtain mixed standard curve solutions with concentrations of 0 μg / L, 10 μg / L, 20 μg / L, 50 μg / L, 80 μg / L, 100 μg / L and 200 μg / L respectively. The mixed standard curve solutions should be prepared and used immediately.

[0071] Preparation of mixed spiked samples: Take 1 kg of spinach that has been tested and found to be free of the carboxylic acid herbicide residue, cut it into small pieces, and homogenize it with a tissue homogenizer. Place it in a polyethylene bottle, weigh 10.00 g of spinach homogenate into 18 50 mL centrifuge tubes, add 1.00 mL of 0.50 mg / L mixed standard solution to each tube, tighten the centrifuge tubes, vortex for 10 minutes, let stand for 24 hours, and store in the refrigerator to obtain a 50 μg / L mixed spiked spinach sample.

[0072] Blank sample preparation: Weigh 10.00g of spinach homogenate into a 50mL centrifuge tube, refrigerate and store to obtain blank spinach samples.

[0073] The pretreatment process for the solution to be tested is described as follows:

[0074] a) Purification using a carboxylic acid herbicide-specific solid-phase extraction (SPE) column and a control SPE column: Add 25 mL of acetonitrile and 1 mL of 10% hydrochloric acid solution to a centrifuge tube containing the spiked sample. Shake at 200 rpm for 30 minutes, then centrifuge at 4000 rpm for 5 minutes. Accurately pipette 5 mL of the supernatant, add 5 mL of deionized water, mix well, and then add it to the carboxylic acid herbicide-specific SPE column and the control SPE column, which have been pre-activated with 50% acetonitrile-water. Maintain a drop rate of approximately 2 minutes / mL on the SPE column, then add 10 mL of... The sample was rinsed with 50% acetonitrile-water solution (acetonitrile to water volume ratio 1:1) and eluted with 10 mL of acetonitrile. The eluent was evaporated to near dryness under nitrogen in a 50°C water bath. 1.00 mL of 50% acetonitrile-water solution was accurately added, and the sample was vortexed for 30 seconds. The solution was then filtered through a 0.22 μm organic microporous membrane to obtain the test solution. One blank sample was selected and purified using a carboxylic acid herbicide-specific solid-phase extraction column according to the above pretreatment process. This sample was named Sample 7. Twelve spiked samples were selected and paralleled using six carboxylic acid herbicide-specific solid-phase extraction columns and six control solid-phase extraction columns, respectively. These were named Samples 8-13 and Samples 14-19.

[0075] b) Purification using a conventional solid-phase extraction column: Add 25 mL of acetonitrile and 1 mL of 10% hydrochloric acid solution to a centrifuge tube containing the spiked sample. Shake at 200 rpm for 30 minutes, then centrifuge at 4000 rpm for 5 minutes. Accurately pipette 5 mL of the supernatant, add 100 mg of PSA, and continue shaking at 200 rpm for 30 minutes, then centrifuge at 4000 rpm for 5 minutes. Accurately pipette 2.5 mL of the supernatant, evaporate to near dryness under nitrogen in a 50°C water bath, accurately add 1.00 mL of 50% acetonitrile aqueous solution, vortex for 30 seconds, and filter through a 0.22 μm organic microporous membrane to obtain the sample solution for analysis. Six conventional solid-phase extraction columns were used as parallel samples, numbered 20-25.

[0076] Liquid chromatography-tandem mass spectrometry detection conditions:

[0077] a) Chromatographic column: Acquity BEHC18 column, 50mm*2.1mm*1.7μm;

[0078] b) The mobile phase composition and gradient elution conditions are shown in Table 1;

[0079] c) Flow rate: 0.2 mL / min;

[0080] d) Liquid chromatography column temperature: 40℃;

[0081] e) Injection volume: 10 μL;

[0082] f) Ionization mode: ESI-;

[0083] g) Detection method: Multiple reaction monitoring (MRM);

[0084] h) Select the monitoring ion (m / z): See Table 2;

[0085] i) Tandem mass spectrometry ion source temperature: 250℃;

[0086] j) Quadrupole temperature: 200℃.

[0087] Table 1. Mobile phase and gradient elution conditions for liquid chromatography

[0088] Time, min 0.1wt% acetic acid aqueous solution, % Acetonitrile, % 0 70 30 1.5 70 30 6 90 10 9 90 10 10 70 30

[0089] Table 2. Retention times, quantitative and qualitative selected ions, declustering voltages, and collision energies of 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, 2,4-dichlorophenoxypropionic acid, and dichloroquinoline acid.

[0090]

[0091]

[0092] Figure 2 The chromatograms and recovery concentration data for 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, 2,4-dichlorophenoxypropionic acid, and dichloroquinoline acid in spinach sample 8 are shown in Table 3. Table 3 shows the average recovery rate and method precision of these four carboxylic acid herbicides in the spinach sample. As can be seen from Table 3, the recovery rates of the four carboxylic acid herbicides using a dedicated solid-phase extraction column for carboxylic acid herbicides are between 70% and 110%, and both the recovery rate and precision meet the requirements for residue detection. In contrast, solid-phase extraction columns, lacking specific pores, are less effective for targeting carboxylic acid herbicides. The traditional solid-phase extraction (SPE) column retains the target analyte molecules, resulting in low and unstable recovery rates and poor precision. Conventional SPE columns achieve recoveries between 70% and 110%, meeting residue detection requirements, but their precision is generally lower than that of dedicated SPE columns for carboxylic acid herbicides. This is because dedicated SPE columns for carboxylic acid herbicides utilize the target analyte retention mechanism, effectively removing impurities during elution, resulting in a colorless and transparent liquid after purification. In contrast, conventional SPE columns retain impurities, which are often larger and cannot be completely removed, and are easily eluted by the elution solution. Therefore, the purified liquid after purification contains some impurities and appears light green. Figure 3 As shown, these impurities will greatly increase the maintenance frequency of liquid chromatography-tandem mass spectrometry, affect the detection results, and even shorten the equipment life.

[0093] Table 3. Average recoveries and precision of 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, 2,4-dichlorophenoxypropionic acid and dichloroquinolinic acid in spinach samples.

[0094]

[0095]

[0096] In summary, the solid-phase extraction column for carboxylic acid herbicides described in this invention has good specificity for carboxylic acid herbicides, high detection sensitivity, thorough impurity removal, minimal impact on detection equipment, good packing stability, high strength, strong chemical resistance, does not contain the analyte, and does not affect residue detection.

[0097] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a solid-phase extraction packing material specifically for carboxylic acid herbicides, characterized in that, Includes the following steps: S1. By weight, add 15 parts of carboxylic acid compound, 8-9.5 parts of enyl alcohol and 0.1-0.12 parts of hydroquinone to a reaction vessel, add 40-60 parts of methylcyclohexane and 2-2.6 parts of catalyst, heat to 75-85℃, react for 4-7 hours until no water is generated; cool to 20-30℃, filter to remove catalyst, wash catalyst with 10-15 parts of methylcyclohexane, combine the washing liquid with the filtrate, and remove methylcyclohexane and excess enyl alcohol by vacuum distillation at 70℃; cool to 20-30℃, add 30-35 parts of saturated sodium bicarbonate aqueous solution, shake to remove hydroquinone; let stand to remove aqueous phase, wash organic phase 3 times with 300 parts of deionized water, discard aqueous phase, and obtain enyl alcohol modified monomer composition; S2. By weight, mix and dissolve 100 parts styrene, 5-10 parts crosslinking agent, and 0.5-1.2 parts initiator to obtain oil phase A; mix and dissolve 4-6 parts of the enyl alcohol modified monomer composition, 10-15 parts styrene, 10-15 parts crosslinking agent, and 10-15 parts vinyl acetate to obtain oil phase B; add 30-40 parts of 0.25% sodium dodecyl sulfate aqueous solution and stir at 800-1000 rpm for 0.5-1 hour to obtain oil phase B; mix 4-6 parts of polyethylene glycol... Enol 1788 and 10-15 parts of sodium chloride were dissolved in 400-500 parts of deionized water. Oil phase A was added, and the mixture was stirred at 1200-1500 rpm and heated to 60-70°C. After maintaining the temperature for 2-3 hours, oil phase B was added dropwise to the reactor over 2-4 hours. After the addition was completed, the mixture was kept at the same temperature for 3-5 hours and then cooled to 20-30°C. The polymer spheres were washed three times with 300 parts of deionized water, dried at 60°C, and sieved to obtain 400-1000 mesh microspheres, thus obtaining cross-linked polymer microspheres. S3. By weight, add 10 parts of polymer microspheres to 160-180 parts of 24% sodium hydroxide solution, heat to 90-100℃, react for 3-5 hours, cool to 20-30℃, wash with deionized water until neutral, extract with a mixed solvent of 400 parts of ethanol, toluene and acetic acid under boiling conditions for 10-12 hours, wash the microspheres with 200 parts of ethanol, wash with deionized water until neutral, and vacuum dry at 60℃ to obtain solid phase extraction packing material for carboxylic acid herbicides.

2. The preparation method of a solid-phase extraction packing material for carboxylic acid herbicides according to claim 1, characterized in that, The carboxylic acid compound in step S1 is a combination of at least three of the following: 5-(2,4-dichlorophenyl)-2-furoic acid, 4-(3,4-dichlorophenyl)-4-phenylbutyric acid, 2-(2,4-dichlorophenyl)thiazol-4-carboxylic acid, 3-amino-4-(3,5-dichlorophenyl)butyric acid, 3-(3-(2,4,5-trichlorophenyl)ureoyl)benzoic acid, or 5-(3,4-dichlorophenyl)nicotinic acid.

3. The preparation method of a solid-phase extraction packing material for carboxylic acid herbicides according to claim 1, characterized in that, In step S1, the alkenyl alcohol is one of allyl alcohol and 2-methyl-2-propen-1-ol.

4. The preparation method of a solid-phase extraction packing material for carboxylic acid herbicides according to claim 1, characterized in that, The catalyst in step S1 is a macroporous strong acid cation exchange resin, which is pre-washed with ethanol and dried to remove moisture before use.

5. The preparation method of a solid-phase extraction packing material for carboxylic acid herbicides according to claim 1, characterized in that, In step S2, the crosslinking agent is one or a combination of several of the following: 80% divinylbenzene, N-methyldiallylamine, and ethylene glycol diallyl ether.

6. The preparation method of a solid-phase extraction packing material for carboxylic acid herbicides according to claim 1, characterized in that, In step S2, the initiator is either dodecyl peroxide or azobisisobutyronitrile.

7. The preparation method of a solid-phase extraction packing material for carboxylic acid herbicides according to claim 1, characterized in that, In step S3, the volume ratio of ethanol, toluene, and acetic acid in the mixed solvent is 2:8:

1.

8. The solid-phase extraction packing material for carboxylic acid herbicides prepared by the method according to any one of claims 1-7.

9. The solid-phase extraction packing material for carboxylic acid herbicides according to claim 8 is used for the residue detection of aryloxycarboxylic acids and arylformic acid herbicides in food and agricultural products.

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