Method for determining benzene series pollutants in water sample through solid-phase microextraction

Abstract

The invention discloses a solid-phase microextraction determination method for benzene series pollutants in a water sample, and belongs to the technical field of chemical analysis detection and sample pretreatment. The method is used for solving the problems that in the prior art, conventional extraction fibers are weak in mechanical force, so that the stability of an extraction head is poor; in order to solve the technical problems that in the prior art, in the prior art, the adsorption force between an extraction head of a metal matrix and a coating material is weak, the solid-phase micro-extraction determination method for benzene series pollutants in a water sample comprises the following steps: S1, collecting a polluted water source in a headspace bottle, and shaking up by oscillation to obtain a sample solution; and S2, carrying out constant-temperature water bath on the headspace bottle, inserting an extraction handle provided with an extraction head coated with a coating, and detecting the adsorption concentration of the benzene series pollutants in the water sample. The extraction head adopted by the determination method is prepared by uniformly mixing high-temperature carbonized and water vapor activated modified fibers and calixarene and performing high pressure; and inserting the combined fiber into the polysiloxane-epoxy resin viscous solution, drying and curing to prepare the extraction head coated with the coating.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical analysis and detection and sample pretreatment, and specifically relates to a method for determining benzene series pollutants in water samples by solid-phase microextraction. Background Art

[0002] With the rapid development of China's industry, the types of organic pollutants in the environment are constantly increasing with the increase in wastewater discharge; among them, benzene series pollutants, as the main components of gasoline and chemical synthesis raw materials, are also common organic water pollutants in the environment. Among them, polychlorinated biphenyls, as benzene series pollutants, have the characteristics of high persistence, low volatility, and high harmfulness; therefore, accurately measuring benzene series pollutants represented by polychlorinated biphenyls in environmental samples is the goal that analytical workers have been constantly pursuing.

[0003] Solid-phase microextraction (SPME), as a sample pretreatment method, has the advantages of simple operation, short time consumption, and small sample usage; if the solid-phase microextraction method is applied to the determination of benzene series pollutants, it can achieve rapid, efficient, and sensitive analysis of benzene series pollutants; among them, the extraction head material, the shape and structure of the extraction head, and the coating material used are crucial for the analysis of the target substance. However, common coating materials fail to specifically extract benzene series pollutants represented by polychlorinated biphenyls.

[0004] Patent application CN115282640A discloses a molecularly imprinted solid-phase microextraction fiber coating and its preparation method and application. Using 4,4'-biphenyldichlorobenzyl as a template molecule, in-situ polymerization with a functional monomer is carried out to prepare a molecularly imprinted solid-phase microextraction fiber coating with a rough surface and uniform thickness. The above-mentioned molecularly imprinted solid-phase microextraction fiber contains various functional groups such as mercapto and phenyl, so it has a good strong specific adsorption function for polychlorinated biphenyls. However, the above-mentioned prior art does not disclose the material and components of the extraction fiber filament used. Conventional extraction fibers have the disadvantage of weak mechanical force, resulting in poor stability of the extraction head; while the extraction head with a metal matrix has the disadvantage of weak adsorption force with the coating material; selecting and designing a suitable extraction fiber filament material plays an important role in extraction sensitivity, stability, and accuracy.

[0005] In view of the technical defects in this regard, a solution is now proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for determining benzene series pollutants in water samples by solid-phase microextraction, which is used to solve the technical problems that in the existing solid-phase microextraction technology, common coating materials fail to specifically extract benzene series pollutants represented by polychlorinated biphenyls; and organic extraction heads have weak mechanical force and poor stability.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for determining benzene series pollutants in water samples by solid-phase microextraction, comprising the following steps:

[0009] S1. Collect the polluted water source in a headspace bottle, then seal it with a sealing film and shake it well to obtain a sample solution.

[0010] S2. Keep the headspace bottle in a constant-temperature water bath, insert an extraction handle equipped with an extraction head coated with a coating, expose the extraction head coated with the coating, and quickly insert it into the injection port of a gas chromatography-mass spectrometer for determination after equilibration, and the adsorption concentration of benzene series pollutants in the water sample can be detected.

[0011] Furthermore, the preparation method of the extraction head coated with the coating comprises the following steps:

[0012] A1. Heat ethylenediamine to 100 - 110 °C, then add polyacrylonitrile fiber and H2O2 solution, mix well, react at 70 - 80 °C for 5 - 6 h, and then take out the fiber solid; wash the fiber solid with deionized water until it is neutral, and dry it at 50 - 60 °C for 10 - 12 h to obtain modified polyacrylonitrile fiber;

[0013] The polyacrylonitrile fiber is aminated to obtain modified polyacrylonitrile fiber.

[0014] A2. Mix the modified polyacrylonitrile fiber, graphite and an additive to obtain a raw material.

[0015] A3. Transfer the raw material to a resistance furnace, under a nitrogen atmosphere, heat the raw material from room temperature to 800 - 850 °C at a heating rate of 10 - 20 °C / min, then keep it at a constant temperature for 2 - 3 h, and introduce water vapor during the heating process; then stop heating and let the raw material cool naturally to room temperature to obtain the activated fiber; mix the activated fiber and calixarene, and then make a combined fiber with a diameter of 0.2 - 0.25 mm and a length of 1 - 2 cm under high pressure.

[0016] The modified polyacrylonitrile fiber, graphite and the additive kaolin are used as inorganic materials, and after mixing, they are calcined at high temperature. During the high-temperature calcination process, high-temperature water vapor is used for activation, so as to introduce functional groups such as hydroxyl groups on the fiber surface to obtain the activated fiber. Mix the activated fiber and calixarene to prepare a combined fiber.

[0017] A4. Install the combined fiber in a solid-phase microextraction injection device, then insert the combined fiber into a polydimethylsiloxane-epoxy resin viscous solution and dry and cure it to prepare an extraction head coated with a coating.

[0018] Further, in step A1, the concentration of the H2O2 solution is 30-40% wt; the dosage ratio of ethylenediamine, polyacrylonitrile fiber, and H2O2 solution is 20-30 mL: 3-5 g: 1-2 mL; in step A2, the auxiliary agent is kaolin; the weight ratio of the modified polyacrylonitrile fiber, graphite, and auxiliary agent is 30-40: 40-50: 5-10.

[0019] Further, in step A3, the rate of introducing steam is 50 mL / min, and the duration of introducing steam is 3-5 min; the weight ratio of the activated fiber and calixarene is 50-60: 10-20, and the pressing pressure is 10-20 MPa; in step A4, the insertion duration is 20-30 min, the temperature for drying and curing is 120-180 °C, and the duration for drying and curing is 2-3 h.

[0020] Further, the preparation method of the polysiloxane-epoxy resin viscous solution includes the following steps:

[0021] B1. Add 2-chloroethyltriethoxysilane and solid phase transfer catalyst into the high-pressure reactor in sequence, then introduce hydrogen sulfide gas into the high-pressure reactor until the pressure of the high-pressure reactor is 305-345 kPa, and then stop introducing hydrogen sulfide gas; stir the inside of the high-pressure reactor evenly to obtain a mixture; introduce sodium hydrosulfide solution into the mixture, and carry out a constant-temperature reaction at 75-80 °C for 4-5 h to obtain a reactant; cool the reactant to room temperature, and collect the organic liquid phase, which is the synthesized mercaptoethyltriethoxysilane.

[0022] Using sodium hydrosulfide solution as a catalyst, 2-chloroethyltriethoxysilane reacts with hydrogen sulfide gas to prepare mercaptoethyltriethoxysilane, and its reaction formula is as follows:

[0023]

[0024] B2. Add isocyanuric acid triglycidyl ester into DMF, stir until isocyanuric acid triglycidyl ester is completely dissolved to obtain an isocyanuric acid triglycidyl ester solution; then mix the mercaptoethyltriethoxysilane, isocyanuric acid triglycidyl ester solution, and curing agent evenly, and carry out rotary evaporation and concentration to obtain the polysiloxane-epoxy resin viscous solution.

[0025] Isocyanuric acid triglycidyl ester and mercaptoethyltriethoxysilane can undergo a cross-linking reaction under high-temperature conditions, and are cured using a curing agent to prepare the polysiloxane-epoxy resin viscous solution.

[0026] Further, in step B1, the solid phase transfer catalyst is tetrabutylammonium bromide; the dosage ratio of 2-chloroethyltriethoxysilane to the solid phase transfer catalyst is 22.6 - 45.2 g : 0.3 - 0.48 g; the concentration of the sodium hydrosulfide solution is 50 - 60% wt, and the dosage ratio of the mixture to the sodium hydrosulfide solution is 45 g : 30 - 40 g.

[0027] Further, in step B2, the dosage ratio of triglycidyl isocyanurate to DMF is 3 - 5 g : 20 - 30 mL; the curing agent is any one of curing agent HT901, curing agent HT933 or curing agent HT906, and the dosage ratio of mercaptoethyltriethoxysilane, triglycidyl isocyanurate solution to the curing agent is 20 - 25 g : 20 - 30 mL : 0.5 - 1 g; the duration of rotary evaporation and concentration is 20 - 30 min, and the temperature of rotary evaporation and concentration is 80 - 90 °C.

[0028] Further, in step S2, the temperature of the constant temperature water bath is 60 - 65 °C, and the equilibration duration is 30 - 40 min.

[0029] The present invention has the following beneficial effects:

[0030] 1. The present invention uses solid-phase microextraction to determine benzene series pollutants. The present invention uses a modified fiber filament as the extraction head, and then coats the synthesized polysiloxane-epoxy resin viscous solution on the extraction head. The prepared extraction device has the advantages of high sensitivity, good accuracy and stable detection results. Polyacrylonitrile fiber contains abundant nitrile functional groups. If polyacrylonitrile fiber is mixed with inorganic materials such as graphite and kaolin, the components of the prepared raw materials can adsorb each other; then the above raw materials are jointly subjected to high-temperature calcination, carbonization and pressing to prepare the extraction head. The above extraction head and the coating material modified epoxy resin can adhere through various methods such as electrostatic adsorption and reaction, so as to improve the connection density and stability between the synthesized extraction head and the coating; further, the mixed raw materials prepared from modified polyacrylonitrile fiber, graphite and kaolin additives are carbonized, and the carbonized fiber and inorganic material have a larger specific surface area, faster adsorption speed and larger extraction amount. In addition, high-temperature steam activation can enrich the number of hydroxyl functional groups contained in the extraction head. Calixarene, as the third-generation macrocyclic compound, has a unique hydrophobic cavity size, with hydrophilic carboxyl groups at the upper end and hydrophobic alkyl chains at the lower end. It can self-assemble with the activated fiber to form an extraction head containing a porous structure.

[0031] 2. The present invention uses epoxy resin as the coating material for synthesizing the extraction head. Due to having multiple epoxy groups, its crosslinking density with curing agents, etc. is greater, making triglycidyl isocyanurate have excellent high-temperature resistance and chemical stability. The present invention modifies triglycidyl isocyanurate with mercaptoethyltriethoxysilane to prepare a polysiloxane-epoxy resin viscous solution. As an organic polymer, polysiloxane has the advantages of high viscosity, good wettability, and easy impregnation. Just by using the physical coating method to coat it on the extraction head, it has excellent film-forming properties. 2-chloroethyltriethoxysilane is reacted to prepare mercaptoethyltriethoxysilane; mercaptoethyltriethoxysilane can react with triglycidyl isocyanurate under high-temperature conditions to prepare a polysiloxane-epoxy resin viscous solution. The present invention inserts the synthesized extraction head into the polysiloxane-epoxy resin viscous solution, and through organic reactions of various functional groups, the prepared extraction device has the advantages of sensitive, accurate, and high-stability detection of benzene series pollutants in water samples. Detailed Embodiments

[0032] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0033] The triglycidyl isocyanurate used in Examples 1-3 of the present invention was purchased from Nanjing Bermuda Biotechnology Co., Ltd., with an EINECS number of 219-514-3; the curing agents HT901, HT933, and HT906 used in Examples 1-3 of the present invention were purchased from Jiaxing Dongzhen Chemical Products Co., Ltd.; the polyacrylonitrile fibers used in Examples 4-6 of the present invention were purchased from Changzhou Tianyi Engineering Fiber Co., Ltd., with a density of 1.18 g / cm 3 ; the graphite used in Examples 4-6 of the present invention was purchased from Jiushun Mineral Products Co., Ltd. in Lingshou County, with a crystal particle size of 0.5 mm; the kaolin used in Examples 4-6 of the present invention was purchased from Changhe Mineral Products Processing Factory in Lingshou County, with a product number of h8955555; the calixarene used in Examples 4-6 of the present invention was specifically 4-tert-butylcalix[6]arene, purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd., with a product number of PA22231; the bisphenol A epoxy resin used in Comparative Example 2 was purchased from Linzi Shuangli Resin Factory in Zibo City, with a product number of 005 and a brand number of 604.

[0034] Example 1

[0035] This example provides a method for preparing a polysiloxane-epoxy resin viscous solution for a solid-phase microextraction fiber coating for benzene series pollutants in water samples, including the following steps:

[0036] B1. Select a 500 mL stainless steel high-pressure reaction kettle for laboratory use. Sequentially add 22.6 g of 2-chloroethyltriethoxysilane and 0.3 g of the solid phase transfer catalyst tetrabutylammonium bromide into the high-pressure reaction kettle. Then, introduce hydrogen sulfide gas into the high-pressure reaction kettle until the pressure in the high-pressure reaction kettle reaches 305 kPa, and stop introducing hydrogen sulfide gas. Stir the inside of the high-pressure reaction kettle through a stirring device to mix the above reactants to obtain a mixture, and retain 45 g of the mixture for further reaction. Then, introduce 30 g of a 50% wt sodium hydrosulfide solution into the above high-pressure reaction kettle. The high-pressure reaction kettle is maintained at a constant temperature of 75 °C for 4 h by means of jacket electric heating to obtain a reaction product. Then, naturally cool the high-pressure reaction kettle to room temperature, and collect the organic liquid phase, which is the synthesized mercaptoethyltriethoxysilane.

[0037] B2. Add 3 g of triglycidyl isocyanurate into 20 mL of DMF, and stir until it is completely dissolved to obtain a triglycidyl isocyanurate solution. Then, mix 20 g of mercaptoethyltriethoxysilane, 20 mL of the triglycidyl isocyanurate solution and 0.5 g of curing agent HT901, and rotary evaporate and concentrate part of the DMF solvent. The temperature for rotary evaporation and concentration is 80 °C, and the duration of rotary evaporation and concentration is 20 min to obtain a polysiloxane-epoxy resin viscous solution.

[0038] Example 2

[0039] This example provides a method for preparing a polysiloxane-epoxy resin viscous solution for a solid-phase microextraction fiber coating for benzene series pollutants in water samples, including the following steps:

[0040] B1. Select a 500 mL stainless steel high-pressure reaction kettle for laboratory use. Sequentially add 23.9 g of 2-chloroethyltriethoxysilane and 0.39 g of the solid phase transfer catalyst tetrabutylammonium bromide into the high-pressure reaction kettle. Then, introduce hydrogen sulfide gas into the high-pressure reaction kettle until the pressure in the high-pressure reaction kettle reaches 325 kPa, and stop introducing hydrogen sulfide gas. Stir the inside of the high-pressure reaction kettle through a stirring device to mix the above reactants to obtain a mixture, and retain 45 g of the mixture for further reaction. Then, introduce 35 g of a 55% wt sodium hydrosulfide solution into the above high-pressure reaction kettle. The high-pressure reaction kettle is maintained at a constant temperature of 78 °C for 4.5 h by means of jacket electric heating to obtain a reaction product. Then, naturally cool the high-pressure reaction kettle to room temperature, and collect the organic liquid phase, which is the synthesized mercaptoethyltriethoxysilane.

[0041] B2. Add 4 g of triglycidyl isocyanurate to 25 mL of DMF, stir until completely dissolved to obtain a triglycidyl isocyanurate solution. Then mix 22 g of mercaptoethyltriethoxysilane, 25 mL of the triglycidyl isocyanurate solution and 0.8 g of curing agent HT933, rotary evaporate and concentrate part of the DMF solvent. The temperature of rotary evaporation and concentration is 85 °C and the duration is 25 min to obtain a polysiloxane-epoxy resin viscous solution.

[0042] Example 3

[0043] This example provides a method for preparing a polysiloxane-epoxy resin viscous solution for a solid-phase microextraction fiber coating for benzene series pollutants in water samples, including the following steps:

[0044] B1. Select a 500 mL laboratory stainless steel high-pressure reactor, sequentially add 45.2 g of 2-chloroethyltriethoxysilane and 0.48 g of solid phase transfer catalyst tetrabutylammonium bromide to the high-pressure reactor, and then introduce hydrogen sulfide gas into the high-pressure reactor until the pressure of the high-pressure reactor is 345 kPa, and stop introducing hydrogen sulfide gas; stir the inside of the high-pressure reactor through a stirring device to mix the above reactants to obtain a mixture, and retain 45 g of the mixture for continued reaction. Then introduce 40 g of 60% wt sodium hydrosulfide solution into the above high-pressure reactor; the high-pressure reactor is kept at a constant temperature of 80 °C for 5 h by means of jacket electric heating to obtain a reactant; then naturally cool the high-pressure reactor to room temperature and collect the organic liquid phase, which is the synthesized mercaptoethyltriethoxysilane.

[0045] B2. Add 5 g of triglycidyl isocyanurate to 30 mL of DMF, stir until completely dissolved to obtain a triglycidyl isocyanurate solution. Then mix 25 g of mercaptoethyltriethoxysilane, 30 mL of the triglycidyl isocyanurate solution and 1 g of curing agent HT906, rotary evaporate and concentrate part of the DMF solvent. The temperature of rotary evaporation and concentration is 90 °C and the duration is 30 min to obtain a polysiloxane-epoxy resin viscous solution.

[0046] Example 4

[0047] This example provides a method for preparing an extraction head coated with a coating for solid-phase microextraction of benzene series pollutants in water samples:

[0048] A1. Add 20 mL of ethylenediamine to a 250 mL three-necked flask, and then heat it in a water bath to 100 °C; add 3 g of polyacrylonitrile fiber and 1 mL of 30% wt H₂O₂ solution to the three-necked flask and mix well, and react at 70 °C for 5 h; take out the fiber solid, and wash it with deionized water until the pH value of the liquid droplets on the surface of the fiber solid is neutral; then dry the fiber in an oven at 50 °C for 10 h to obtain modified polyacrylonitrile fiber.

[0049] A2. According to parts by weight, mix 30 parts of modified polyacrylonitrile fiber, 40 parts of graphite and 5 parts of kaolin as an additive evenly, and grind them to 200 mesh to obtain the raw material.

[0050] A3. Weigh 5 g of the raw material and add it to a quartz boat. Place the quartz boat in a small tubular resistance furnace (inner diameter 40 mm, length 600 mm), introduce nitrogen to displace the air in the tubular resistance furnace, and then heat the tubular resistance furnace; the heating rate is 10 °C / min, heat to 800 °C and keep it at a constant temperature for 2 h, and always introduce water vapor into the tubular resistance furnace at a rate of 50 mL / min during the heating process; then stop heating and naturally cool to room temperature to obtain the activated fiber. According to parts by weight, mix 50 parts of the activated fiber and 10 parts of calixarene evenly, and then press them into an extraction head with a diameter of 0.2 mm and a length of 1 cm at 10 MPa.

[0051] A4. Install the above extraction head in a solid-phase microextraction injection device, and then insert the extraction head into the polydimethylsiloxane-epoxy resin viscous solution in Example 1 for 20 min, and dry and cure it at 120 °C for 2 h to prepare an extraction head coated with a coating.

[0052] Example 5

[0053] This example provides a method for preparing an extraction head coated with a coating for solid-phase microextraction of benzene series pollutants in water samples:

[0054] A1. Add 25 mL of ethylenediamine to a 250 mL three-necked flask, and then heat it in a water bath to 105 °C; add 4 g of polyacrylonitrile fiber and 1.5 mL of 35% wt H₂O₂ solution to the three-necked flask and mix well, and react at 77 °C for 5.5 h; then take out the fiber solid, and wash it with deionized water until the pH value of the liquid droplets on the surface of the fiber solid is neutral; then dry the fiber in an oven at 55 °C for 11 h to obtain solid modified polyacrylonitrile fiber.

[0055] A2. According to parts by weight, mix 35 parts of modified polyacrylonitrile fiber, 45 parts of graphite and 8 parts of kaolin as an additive evenly, and grind them to 200 mesh to obtain the raw material.

[0056] A3. Weigh 8 g of the raw materials and add them into a quartz boat. Place the quartz boat in a small tubular resistance furnace (inner diameter: 40 mm, length: 600 mm). Introduce nitrogen to displace the air in the tubular resistance furnace, and then heat the tubular resistance furnace. When the heating rate is 12 °C / min, heat it to 830 °C and keep it at a constant temperature for 2.5 hours. During the heating process, introduce steam into the tubular resistance furnace at a rate of 80 mL / min. Then stop heating and let it cool naturally to room temperature to obtain the activated fibers. By weight, mix 55 parts of the activated fibers and 15 parts of calixarene evenly, and then press them into an extraction head with a diameter of 0.22 mm and a length of 1.5 cm under 15 MPa.

[0057] A4. Install the above extraction head in a solid-phase microextraction injection device, and then insert the extraction head into the polydimethylsiloxane-epoxy resin viscous solution prepared in Example 2 for 25 minutes, and dry and cure it at 150 °C for 2.3 hours to prepare an extraction head coated with a coating.

[0058] Example 6

[0059] This example provides a method for preparing an extraction head coated with a coating for solid-phase microextraction of benzene series pollutants in water samples:

[0060] A1. Add 30 mL of ethylenediamine to a 250 mL three-necked flask, and then heat it in a water bath to 110 °C. Add 5 g of polyacrylonitrile fibers and 2 mL of 40% wt H2O2 solution to the three-necked flask and mix well. React at 80 °C for 6 hours. Take out the fiber solid, wash it with deionized water until the pH value of the liquid droplets on the surface of the fiber solid is neutral. Then dry the fiber in an oven at 60 °C for 12 hours to obtain solid modified polyacrylonitrile fibers.

[0061] A2. By weight, mix 40 parts of the modified polyacrylonitrile fibers, 50 parts of graphite, and 10 parts of the auxiliary agent kaolin evenly to obtain the raw materials.

[0062] A3. Weigh 10 g of the raw materials and add them into a quartz boat. Place the quartz boat in a small tubular resistance furnace (inner diameter: 40 mm, length: 600 mm). Introduce nitrogen to displace the air in the tubular resistance furnace, and then heat the tubular resistance furnace. The heating rate is 20 °C / min. Heat it to 850 °C and keep it at a constant temperature for 3 hours. During the heating process, always introduce steam into the tubular resistance furnace at a rate of 50 mL / min for 5 minutes. Then stop heating and let it cool naturally to room temperature to obtain the activated fibers. By weight, mix 60 parts of the activated fibers and 20 parts of calixarene evenly, and then press them into an extraction head with a diameter of 0.25 mm and a length of 2 cm under 20 MPa.

[0063] A4. Install the above extraction head in the solid-phase microextraction injection device, then insert the extraction head into the polydimethylsiloxane-epoxy resin viscous solution prepared in Example 3 for 30 min, and dry and cure it at 180 °C for 3 h to prepare an extraction head coated with a coating.

[0064] Example 7

[0065] This example provides a method for determining benzene series pollutants in water samples by solid-phase microextraction, which includes the following steps:

[0066] S1. Take 10.00 mL of the polluted water sample from a chemical plant. Remove the insoluble impurities from the water sample using a 0.5-μm microporous filter membrane, then store 5.00 mL of the water sample in a 20-mL polytetrafluoroethylene headspace bottle, tighten the cap of the headspace bottle, seal the sealing film, and shake well to obtain a sample solution.

[0067] S2. Then place the headspace bottle on a 60 °C constant temperature water bath, insert the extraction handle equipped with a solid-phase microextraction head, expose the extraction head, and quickly insert it into the injection port of the gas chromatography-mass spectrometer for determination after equilibration for 30 min, and the adsorption concentration of benzene series pollutants in the water sample can be detected.

[0068] Example 8

[0069] This example provides a method for determining benzene series pollutants in water samples by solid-phase microextraction, which includes the following steps:

[0070] S1. Take 10.00 mL of the polluted water sample from a chemical plant. Remove the insoluble impurities from the water sample using a 0.5-μm microporous filter membrane, then store 5.00 mL of the water sample in a 20-mL polytetrafluoroethylene headspace bottle, tighten the cap of the headspace bottle, seal the sealing film, and shake well to obtain a sample solution.

[0071] S2. Then place the headspace bottle on a 62 °C constant temperature water bath, insert the extraction handle equipped with a solid-phase microextraction head, expose the extraction head, and quickly insert it into the injection port of the gas chromatography-mass spectrometer for determination after equilibration for 35 min, and the adsorption concentration of benzene series pollutants in the water sample can be detected.

[0072] Example 9

[0073] This example provides a method for determining benzene series pollutants in water samples by solid-phase microextraction, which includes the following steps:

[0074] S1. Take 10.00 mL of the polluted water sample from a chemical plant. Remove the insoluble impurities from the water sample using a 0.5-μm microporous filter membrane, then store 5.00 mL of the water sample in a 20-mL polytetrafluoroethylene headspace bottle, tighten the cap of the headspace bottle, seal the sealing film, and shake well to obtain a sample solution.

[0075] S2. Subsequently, place the headspace vial on a constant temperature water bath at 65 °C, insert the extraction handle equipped with a solid-phase microextraction fiber, expose the fiber, and after equilibration for 40 min, quickly insert it into the injection port of the gas chromatography-mass spectrometer for determination. The adsorbed concentration of benzene series pollutants in the water sample can be detected.

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 9 is that when preparing the extraction fiber coated with the coating, the fiber was not activated with water vapor during the carbonization process.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 9 is that when preparing the polysiloxane-epoxy resin viscous solution, bisphenol A epoxy resin with the same mass was used to replace triglycidyl isocyanurate.

[0080] Comparative Example 3

[0081] The difference between this comparative example and Example 9 is that when preparing the polysiloxane-epoxy resin viscous solution, step B1 was cancelled, and 2-chloroethyltriethoxysilane with the same amount of substance was used to replace mercaptoethyltriethoxysilane.

[0082] Performance test:

[0083] Quantitative analysis and evaluation were carried out on the water samples prepared by solid-phase microextraction in Examples 7-9 and Comparative Examples 1-3; the linear correlation coefficient (R) value, method detection limit, and linear range values were recorded. Subsequently, the solid-phase microextraction methods in Examples 7-9 and Comparative Examples 1-3 were used to test the recovery rate of PCBs with a concentration of 120 ng / L in water. The specific test results are shown in the following table.

[0084] Table 1 - Data sheet for performance detection of samples

[0085]

[0086] Data analysis: By comparing and analyzing the data in Table 1, the solid-phase microextraction method for benzene series pollutants in water samples used in the present invention has good ability to extract benzene series pollutants in water samples, showing a wide linear range, low detection limit, and good reproducibility (high linear correlation coefficient R value).

[0087] However, in Comparative Example 1, when preparing the extraction fiber, the fiber was not activated with water vapor during the carbonization process, and the number of functional groups such as hydroxyl groups on its surface decreased; the modified polyacrylonitrile fiber after activation has better adsorption performance with calixarene and the organic material coated on the extraction fiber, so the detection of benzene series pollutants is more sensitive and accurate.

[0088] In Comparative Example 2, when preparing the polysiloxane-epoxy resin viscous solution, bisphenol A epoxy resin of the same mass was used to replace triglycidyl isocyanurate; mercaptoethyltriethoxysilane has stronger reactivity and higher adsorption degree with triglycidyl isocyanurate, which is manifested as higher curing degree and viscosity of the prepared polysiloxane-epoxy resin viscous solution on the extraction head.

[0089] In Comparative Example 3, when preparing the polysiloxane-epoxy resin viscous solution, step B1 was cancelled, and 2-chloroethyltriethoxysilane of the same amount of substance was used to replace mercaptoethyltriethoxysilane; 2-chloroethyltriethoxysilane does not react with triglycidyl isocyanurate; the epoxy resin grafted with siloxane has good film-forming property and better adsorption performance. It is manifested that the prepared extraction head has better sensitivity to adsorb organic materials and more accurate detection data.

[0090] The above content is only an example and illustration of the structure of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

[0091] In the description of this specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0092] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the present invention to only the specific implementation manners. Obviously, according to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well. The present invention is only limited by the claim book and its full scope and equivalents.

Claims

1. A method for determining benzene-based pollutants in water samples by solid phase microextraction, characterized in that: The following steps are involved: S1. Collect the polluted water from the headspace bottle, seal it with a sealing film, shake it evenly, and get the sample solution; S2. Place the headspace bottle in a constant temperature water bath, insert the extraction handle equipped with the coated extraction head, expose the coated extraction head, and quickly insert it into the injection port of the gas chromatography-mass spectrometer for measurement after equilibrium, so as to detect the adsorption concentration of benzene pollutants in the water sample.

2. The method for determining benzene-based pollutants in water samples by solid phase microextraction according to claim 1, characterized in that: The method for preparing the extraction head coated with the coating comprises the following steps: A1. Heat ethylenediamine to 100-110°C, then add polyacrylonitrile fiber and H2O2 solution, mix well, react at 70-80°C for 5-6h, then take out the fiber solid; wash the fiber solid with deionized water until the fiber solid is neutral, and dry at 50-60°C for 10-12h to obtain modified polyacrylonitrile fiber; A2, mixing modified polyacrylonitrile fiber, graphite and additives to obtain a raw material; A3. The raw material is transferred to a resistance furnace, and heated from room temperature to 800-850°C at a heating rate of 10-20°C / min under a nitrogen atmosphere, and then isothermally reacted for 2-3 hours, and water vapor is introduced during the heating process; the heating is then stopped, and the raw material is naturally cooled to room temperature to obtain activated fibers; the activated fibers and calixarene are mixed, and then pressed into an extraction head with a diameter of 0.2-0.25 mm and a length of 1-2 cm; A4. The extraction head is installed in a solid phase microextraction sampling device, and then the extraction head is inserted into a polysiloxane-epoxy resin viscous solution and dried and solidified to prepare an extraction head coated with a coating.

3. The method for determining benzene-based pollutants in water samples by solid phase microextraction according to claim 2, characterized in that: In step A1, the concentration of the H2O2 solution is 30-40%wt; The dosage ratio of ethylenediamine, polyacrylonitrile fiber and H2O2 solution is 20-30mL:3-5g:1-2mL; in step A2, the auxiliary agent is kaolin; the weight ratio of modified polyacrylonitrile fiber, graphite and auxiliary agent is 30-40:40-50:5-10.

4. The method for determining benzene-based pollutants in water samples by solid phase microextraction according to claim 2, characterized in that: In step A3, the rate of introducing water vapor is 50 mL / min, and the duration of introducing water vapor is 3-5 min; the weight ratio of the activated fiber and calixarene is 50-60:10-20, and the pressing pressure is 10-20 MPa; In step A4, the insertion time is 20-30 minutes, the drying and curing temperature is 120-180° C., and the drying and curing time is 2-3 hours.

5. The method for determining benzene-based pollutants in water samples by solid phase microextraction according to claim 1, characterized in that: The method for preparing the polysiloxane-epoxy resin viscous solution comprises the following steps: B1. Add 2-chloroethyltriethoxysilane and a solid phase transfer catalyst to a high-pressure reactor in sequence, and then introduce hydrogen sulfide gas into the high-pressure reactor until the pressure of the high-pressure reactor reaches 305-345 kPa, and then stop introducing hydrogen sulfide gas; stir the inside of the high-pressure reactor to obtain a mixture; introduce sodium hydrosulfide solution into the mixture, and react at a constant temperature of 75-80° C. for 4-5 hours to obtain a reactant; cool the reactant to room temperature, and collect the organic liquid phase, which is the synthesized mercaptoethyltriethoxysilane; B2. Add triglycidyl isocyanurate into DMF and stir until triglycidyl isocyanurate is completely dissolved to obtain triglycidyl isocyanurate solution; then mix mercaptoethyl triethoxysilane, triglycidyl isocyanurate solution and curing agent, and concentrate by rotary evaporation to obtain polysiloxane-epoxy resin viscous solution.

6. The method for determining benzene-based pollutants in water samples by solid phase microextraction according to claim 5, characterized in that: In step B1, the solid phase transfer catalyst is tetrabutylammonium bromide; the usage ratio of 2-chloroethyltriethoxysilane to the solid phase transfer catalyst is 22.6-45.2 g:0.3-0.48 g; the concentration of the sodium hydrosulfide solution is 50-60%wt, and the usage ratio of the mixture to the sodium hydrosulfide solution is 45 g:30-40 g.

7. The method for determining benzene-based pollutants in water samples by solid phase microextraction according to claim 5, characterized in that: In step B2, the amount ratio of triglycidyl isocyanurate and DMF is 3-5g:20-30mL; the curing agent is any one of curing agent HT901, curing agent HT933 or curing agent HT906, and the amount ratio of mercaptoethyl triethoxysilane, triglycidyl isocyanurate solution and curing agent is 20-25g:20-30mL:0.5-1g; the time of rotary evaporation concentration is 20-30min, and the temperature of rotary evaporation concentration is 80-90°C.

8. The method for determining benzene-based pollutants in water samples by solid phase microextraction according to claim 1, characterized in that: In step S2, the temperature of the constant temperature water bath is 60-65° C., and the equilibration time is 30-40 min.

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