Nano-plastic detection device and method based on magnetic adsorption-thermal cracking mass spectrometry technology

Abstract

The invention provides a nano-plastic detection device and method based on a magnetic adsorption-thermal cracking mass spectrometry technology, and solves the technical problem that the variety, content and physicochemical properties of nano-plastic in a water matrix are difficult to rapidly and accurately capture in the prior art. The pyrolysis device comprises a closed heating cavity, a resistance wire is wound on the closed heating cavity, the closed heating cavity is communicated with a carrier gas inlet pipe, a water vapor outlet pipe and a pyrolysis gas outlet pipe, and a sample groove is formed in the closed heating cavity; the sample introduction device comprises a sample introduction pipeline, and the sample introduction pipeline penetrates into the closed heating cavity in a sealed manner and is communicated with the sample groove; the groove bottom of the sample groove is a filter layer, the filter layer comprises a filter membrane layer, the filter membrane layer is connected to a ferromagnetic metal sheet, the aperture of filter holes of the filter membrane layer is smaller than the particle size of the nano-plastic, the heat-resistant temperature of the filter membrane layer is higher than the boiling point of the nano-plastic, and the ferromagnetic metal sheet is provided with a filtrate channel; the suction filtration device comprises a suction filtration head; the suction filtration head is communicated with the sample groove through a filter layer; the method can be widely applied to the technical field of nano-plastic pollution detection.

Description

Technical Field

[0001] This application relates to the technical field of nanoplastics pollution detection, and particularly to a nanoplastics detection device and method based on magnetic adsorption-pyrolysis mass spectrometry technology. Background Art

[0002] Plastic is the most common organic synthetic polymer material in daily life and is widely used due to its many advantages such as low price, light weight, and convenient use. According to statistics, the global consumption of plastic products reached as high as 300 million tons in 2013. The Greenpeace report in 2016 stated that about 200 kg of plastic enters the ocean per second, and the use of plastic is still increasing. Among them, about 10% of plastic waste enters the ocean, and the remaining plastic waste pollutes the terrestrial environment through recycling, incineration, landfilling, discarding and other ways. Plastic waste accumulates continuously in the environment. Its chemical properties are relatively stable, and most plastics are difficult to degrade and will exist for more than hundreds of years. Subject to the combined action of external forces such as physical, chemical and biological in the environment, such as wind and waves, ocean currents, sunlight, and marine microorganisms, large pieces of plastic will continuously break into tiny plastic fragments. In addition, facial cleansers, some cosmetics, and industrial abrasives we use daily all contain plastic particles. These plastic fragments and particles can migrate continuously in the environment with rivers, wind, and ocean currents, showing a global distribution trend.

[0003] The earliest report on marine plastic waste was in the 1970s. Currently, plastic fragment pollution has been found in the Atlantic Ocean, Pacific Ocean, polar regions, deep sea, and even high-altitude lakes. In 2004, British scientists published a paper on plastic fragments in ocean water and sediments in science, which attracted worldwide attention, and more and more researchers have carried out related research on microplastics.

[0004] Currently, plastic fragments with a particle size less than 5 mm are collectively referred to as microplastics. Microplastics are also known as "PM2.5 in the ocean", and are listed as the second major scientific problem in the field of environmental and ecological science research, and have become a major global environmental problem on a par with global climate change, ozone depletion, and ocean acidification. Marine microplastics will cause serious harm to the marine environment and ecology. Microplastics suspended in seawater will affect the photosynthesis of marine algae; they are easily ingested by some marine organisms and are difficult to digest in the gastrointestinal tract, causing malnutrition or even death of marine organisms. Some studies have found that microplastics can also affect the spawning and reproductive ability of some marine organisms such as fish; in addition, microplastics themselves contain some toxic plastic additives, and their surfaces are also prone to enrichment of organic pollutants and heavy metals, etc., which will have a toxic effect on surrounding organisms; microplastics enter the human body through the food chain and will have an impact on human health that cannot be ignored. In recent years, the problem of microplastic pollution has received more and more attention, and microplastics have been detected in more and more environmental media.

[0005] At present, the damage to the marine ecological environment caused by microplastic pollution and its threat to human health have attracted great attention. Various studies on microplastics are also actively underway, and the detection technology of microplastics is a foundation to support microplastic research. The detection methods of microplastics include visual method, microscopic spectroscopy, thermal analysis mass spectrometry, etc. Among them, the visual method is convenient to operate, but it takes a long time, is difficult to detect micron-sized samples, and is easily affected by subjective judgment, resulting in difficult quantitative comparison. The main measurement methods rely on counting (pieces / km 2 、pieces / L, pieces / kg, etc.), and it is difficult to obtain direct mass concentration information; the microscopic spectroscopy combines microscope imaging technology and infrared spectroscopy or Raman spectroscopy to identify three-dimensional information of particle size, type and quantity, but there is a lack of acquisition of microplastic mass information, and it may encounter challenges of overlapping test information and decreased accuracy; the thermal analysis mass spectrometry combines pyrolysis technology and mass spectrometry technology to analyze the two-dimensional information of the type and mass of microplastics, but due to its destructive analysis characteristics, the particle size and quantity information of microplastics cannot be obtained.

[0006] With the continuous in-depth research on microplastics, various studies on nanoplastics are also actively underway. Nanoplastics usually refer to plastic particles with a diameter <1μm, which also belong to the category of nanoplastics in terms of size. In recent years, magnetic adsorption separation technology has made remarkable progress in the field of nanoplastics treatment. Research shows that magnetic nanomaterials can efficiently adsorb nanoplastics in water and achieve rapid removal through magnetic separation, with the advantages of low cost, high efficiency, simple operation, and environmental friendliness. However, current research on the adsorption of micro / nanoplastics by magnetic nanoparticles mostly uses counting methods and differential methods to perform secondary separation of nanoplastics, and after obtaining the nanoplastic samples, qualitative and quantitative analysis is carried out on them through spectroscopy, pyrolysis-gas-phase-mass spectrometry, etc. However, due to errors in the results caused by subjective judgment, sample loss, etc. during secondary separation and the technical limitations of the above detection methods, it is difficult to accurately analyze the adsorption performance of the adsorption material, the removal rate of nanoplastics, and the changes in the mass, type, and physical and chemical properties of nanoplastics. Therefore, there are still many blanks to be filled in this research direction.

[0007] To sum up, with the current separation and detection technology level, it is difficult to quickly and accurately capture the types, contents, and changes in physical and chemical properties of nanoplastics in the water matrix, and it cannot meet the research needs of the adsorption performance of adsorbents, the pollution characteristics of nanoplastics, environmental ecological risks, and toxicity stress, etc. Summary of the Invention

[0008] The purpose of the present invention is to solve the above technical deficiencies, and provide a nanoplastic detection device and method based on magnetic adsorption-pyrolysis mass spectrometry technology to achieve rapid and accurate capture of the types, contents, and changes in physical and chemical properties of nanoplastics in the water matrix.

[0009] To this end, the present invention provides a nanoplastics detection device based on magnetic adsorption-pyrolysis mass spectrometry technology, which includes a pyrolysis device, a filter and a mass spectrometry device, and also includes a resistance heating device, a sampling device and a sample tank suction filtration device.

[0010] The resistance heating device is provided with a resistance wire. The pyrolysis device includes a sealed heating cavity. The cavity wall of the sealed heating cavity is wound with a resistance wire. The cavity wall of the sealed heating cavity is respectively and hermetically connected with a carrier gas inlet pipe, a water vapor outlet pipe, and a pyrolysis gas outlet pipe connected to the mass spectrometry device. The sample tank is arranged in the sealed heating cavity; the filter is installed in the pyrolysis gas outlet pipe.

[0011] The sampling device includes a sampling pipeline, and one end of the sampling pipeline is hermetically inserted into the sealed heating cavity and communicated with the sample tank.

[0012] The bottom of the sample tank is a filter layer, which includes a filter membrane layer and a ferromagnetic metal sheet. The filter membrane layer is connected to the ferromagnetic metal sheet. The pore diameter of the filter holes of the filter membrane layer is smaller than the particle size of the nanoplastics, and the heat-resistant temperature of the filter membrane layer is higher than the pyrolysis temperature of the nanoplastics. The ferromagnetic metal sheet is provided with a filtrate channel. The suction filtration device includes a suction filtration head, which is arranged in the sealed heating cavity, and the suction filtration head is communicated with the sample tank through the filter layer.

[0013] The present invention also provides a nanoplastics detection method based on magnetic adsorption-pyrolysis mass spectrometry technology. Using the nanoplastics detection device based on magnetic adsorption-pyrolysis mass spectrometry technology described in any one of the above, the method includes the following steps: S1. Open the sampling pipeline and rinse the sampling pipeline with a rinsing solution; after the rinsing is completed, add the water body to be measured and the magnetic adsorbent into the sample tank through the sampling pipeline, and then close the sampling pipeline.

[0014] S2. Start the suction filtration device to complete the separation of the adsorbent-nanoplastics polymer, the adsorbent, the unadsorbed nanoplastics and the water body in the sample tank, and then close the suction filtration device.

[0015] S3. Open the water vapor outlet pipe and start the resistance heating device. Heat is generated by energizing the resistance wire, so that the ferromagnetic metal sheet generates heat. The residual water in the sample tank is heated to turn into water vapor, and the water vapor is discharged through the water vapor outlet pipe; control the temperature in the sealed heating cavity so that the residual water in the sample tank turns into water vapor, while the nanoplastics themselves do not undergo pyrolysis.

[0016] S4. Close the water vapor outlet pipe, open the carrier gas inlet pipe and the pyrolysis gas outlet pipe, and introduce the carrier gas into the sealed heating cavity; increase the temperature in the sealed heating cavity through the resistance heating device, so that the nanoplastics in the adsorbent-nanoplastic polymer in the sample tank and the unadsorbed nanoplastics undergo pyrolysis to be transformed into pyrolysis gas; driven by the carrier gas, the pyrolysis gas is discharged through the pyrolysis gas outlet pipe, enters the mass spectrometry device through the filter for detection and analysis, and completes the qualitative and quantitative analysis of nanoplastics.

[0017] The beneficial effects of the present invention are as follows: The present invention provides a nanoplastics detection device and method based on magnetic adsorption-pyrolysis mass spectrometry technology. Compared with the traditional detection methods with complex pretreatment, through the integrated design of water body sampling, water sample / nanoplastics separation and pyrolysis analysis, the present invention adopts direct sampling of water samples, and realizes the enrichment and separation of nanoplastics in water samples through a suction filtration device, avoiding complex pretreatment steps, simplifying the operation process of accurately qualitatively and quantitatively detecting nanoplastics, reducing the loss of nanoplastics in the water samples to be detected in the operation process, and significantly reducing the operation difficulty and cost. Compared with the current detection methods for the adsorption performance of adsorbents and nanoplastics detection methods, the present invention can quickly and accurately capture the content, types and physicochemical property change characteristics of nanoplastics, and synchronously and accurately detect the adsorption performance of the adsorbent. This feature breaks through the current dilemma of synchronous, accurate and rapid analysis of nanoplastics separation and detection technologies. It can reduce the influence of subjective judgment on the detection results, improve the accuracy of analysis, and at the same time provide information on nanoplastics components, concentration and physicochemical properties. The present invention will provide more comprehensive, accurate and efficient technical support for the monitoring and evaluation of nanoplastics pollution and the screening of high-efficiency adsorbents, and contribute to the in-depth development of the field of nanoplastics pollution research. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a schematic structural diagram of the present invention; Figure 2 is Figure 1 a schematic structural diagram of a partial cross-sectional view of related components such as the flared outlet section, the sample tank, and the suction filtration device in

[0020] Markings in the figure: 1. Sample cell, 2. Resistance wire, 3. Sealed heating cavity, 4. Carrier gas inlet pipe, 5. Water vapor outlet pipe, 6. Pyrolysis gas outlet pipe, 7. Filter, 8. Sampling pipeline, 9. Filter layer, 10. Filter membrane layer, 11. Ferromagnetic metal sheet, 12. Filtrate channel, 13. Suction filtration head, 14. Sand core filter, 15. Flared outlet section, 16. Sampling funnel, 17. Thermal insulation layer, 18. Encapsulation layer, 19. Gas outlet pipe, 20. Carrier gas channel support pipe, 21. Cover, 22. Base, 23. Suction filtration pipeline, 24. Vacuum pump, 25. Capillary, 26. First valve, 27. Second valve, 28. Third valve, 29. Main pipeline, 30. Mass spectrometry device. Detailed implementation mode

[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application clearer, the following further details this application in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application. The methods used in the present invention are all conventional methods without special regulations; the raw materials and devices used are all conventional commercially available products without special regulations.

[0022] As Figure 1 、 Figure 2 shown, this embodiment provides a nanoplastics detection device based on magnetic adsorption-pyrolysis mass spectrometry technology, which includes a pyrolysis device, a filter 7 and a mass spectrometry device 30, and also includes a resistance heating device, a sampling device, a sample cell 1, and a suction filtration device.

[0023] The resistance heating device is provided with a resistance wire 2. The pyrolysis device includes a sealed heating cavity 3. The cavity wall of the sealed heating cavity 3 is wound with a resistance wire 2. The cavity wall of the sealed heating cavity 3 is respectively sealed and communicated with a carrier gas inlet pipe 4, a water vapor outlet pipe 5, and a pyrolysis gas outlet pipe 6 connected to the mass spectrometry device 30. The sample cell 1 is arranged in the sealed heating cavity 3. Among them, the carrier gas enters the sealed heating cavity 3 through the carrier gas inlet pipe 4, making the inside of the sealed heating cavity 3 have a vacuum environment, protecting the ferromagnetic metal sheet 11 from being oxidized during the high-temperature process, transporting the water vapor converted from the residual water in the sample cell 1 after suction filtration out, and transporting the gas small molecules generated by the pyrolysis of nanoplastics into the mass spectrometry device 30; the water vapor outlet pipe 5 is used to discharge the water vapor formed by the residual water in the sample cell out of the sealed heating cavity 3 to avoid the influence of water vapor on the mass spectrometry analysis result; the pyrolysis gas outlet pipe 6 is used to transport the pyrolysis gas to the mass spectrometry device 30. The filter 7 is installed in the pyrolysis gas outlet pipe 6 to filter impurities such as ash that may be generated by pyrolysis. The pyrolysis gas enters the mass spectrometry device 30 through the capillary 25 to improve the accuracy of detection.

[0024] The pyrolysis device is provided with a resistance wire 2. By energizing the resistance wire 2 wound around the inner wall of the sealed heating cavity 3, the inside of the sealed heating cavity 3 is heated and the temperature is raised, so that the ferromagnetic metal sheet 11 generates heat energy when heated. The resistance wire 2 can be heated by a dense winding method. The heating range is 6 cm, with double-layer heating, the overall thickness is 12 cm, the heating current is 5.6 A, the heating rate is 462 °C / minute, and the heating power is 202 W, meeting the pyrolysis requirements.

[0025] The sample injection device includes a sample injection pipe 8. One end of the sample injection pipe 8 is hermetically inserted into the sealed heating cavity 3 and communicates with the sample tank 1.

[0026] The bottom of the sample tank 1 is a filter layer 9. The filter layer 9 includes a filter membrane layer 10 and a ferromagnetic metal sheet 11. The filter membrane layer 10 is connected and arranged on the ferromagnetic metal sheet 11. The pore diameter of the filter holes of the filter membrane layer 10 is smaller than the particle size of the nano-plastics. The heat-resistant temperature of the filter membrane layer 10 is higher than the pyrolysis temperature of the nano-plastics. The ferromagnetic metal sheet 11 is provided with a filtrate channel 12; wherein, the filter membrane layer 10 is used to filter the nano-plastics in the water sample, and filter membrane layers 10 with different pore diameters and heat-resistant degrees can be selected according to the detection requirements of the nano-plastics in the water sample; on the one hand, the ferromagnetic metal sheet 11 is used to absorb the heat generated by the resistance wire 2, raise the temperature to convert the remaining water in the sample tank 1 (including the filter layer 9 and the nano-plastics) into water vapor and discharge it from the water vapor outlet pipe 5, and continue to raise the temperature to pyrolyze the nano-plastics into pyrolysis gas. That is, when the temperature is raised, compared with the filter layer 10 of the sample tank 1, the ferromagnetic metal sheet 11 absorbs the heat from the resistance wire 2 and raises the temperature faster, causing a temperature difference between the ferromagnetic metal sheet 11 and the filter layer 10, so that the filter layer 10 absorbs not only the heat directly generated by the resistance wire 2, but also the heat indirectly transferred from the ferromagnetic metal sheet 11, accelerating the heating process; on the other hand, using its own magnetism, it firmly adsorbs the adsorbent-nano-plastic polymer and the remaining adsorbent after pyrolysis on the filter membrane layer 10 located at the bottom of the sample tank 1, preventing it from leaving the sample tank 1 under the action of the carrier gas, and at the same time facilitating the efficient recovery of the adsorbent. The ferromagnetic metal sheet 11 is provided with a filtrate channel 12, which does not affect the heating effect while ensuring the water sample suction filtration efficiency. During the suction filtration process, since the particle size of the nano-plastics is larger than the pore diameter of the filter holes of the filter membrane layer 10, that is, the pore diameter of the filter holes of the filter membrane layer 10 is nanoscale, the adsorbent-nano-plastic polymer, nano-plastics, and adsorbent are retained on the filter membrane layer 10. It is required that the heat-resistant temperature of the filter membrane layer 10 is higher than the pyrolysis temperature of the nano-plastics to prevent the filter membrane layer 10 from decomposing due to the high temperature generated by the pyrolysis of the adsorbent-nano-plastic polymer and nano-plastics, thus ensuring the accuracy of the mass spectrometry analysis results.

[0027] The suction filtration device includes a suction filtration head 13. The suction filtration head 13 is arranged in the sealed heating cavity 3. The suction filtration head 13 is connected to the sample tank 1 through a filter layer 9. One end of the suction filtration head 13 is connected to one end of a suction filtration pipe 23, and the other end of the suction filtration pipe 23 passes through the sealed heating cavity 3 and is connected to a suction pump 24. The suction filtration device is an existing device and includes a suction pump 24. During suction filtration, the suction pump 24 will pump out the air in the sample tank 1 to generate negative pressure inside. Under the influence of the pressure difference, the water body in the sample tank 1 will pass downward through the filter layer 9 into the suction filtration head 13 and finally be discharged through the suction filtration pipe 23, realizing the separation of the adsorbent-nanoplastic polymer, nanoplastic, adsorbent and water body in the sample tank 1, thereby achieving the purpose of removing moisture.

[0028] As a preferred embodiment, the filter membrane layer 10 is a high-temperature resistant filter membrane. A filter membrane with a heat resistance temperature above 700 °C is a high-temperature resistant filter membrane. For example, existing products such as alumina filter membranes (with a pore diameter of 20 nm and can withstand a high temperature of 800 °C) etc. The pore diameter of the filter membrane layer 10 is preferably 20 nm to ensure that the adsorbent-nanoplastic polymer, adsorbent and nanoplastic will not be lost through the filter membrane layer 10 during the suction filtration process. The particle size of the nanoplastic particles is 100 - 1000 nm and will not pass through the 20 nm filter membrane layer 10.

[0029] As a preferred embodiment, the ferromagnetic metal sheet 11 is a nickel sheet. The melting point of the nickel sheet is 1453 °C and can withstand the high temperature (about 700 °C) generated during the thermal cracking of nanoplastic; the ferromagnetic metal sheet 11 can also be replaced by an iron-cobalt alloy sheet, an iron-nickel alloy sheet, etc. The filtrate channels 12 can be multiple holes, and the pore diameter is preferably set to 10 μm. It can be set according to the hole density and quantity to ensure that the water can pass through the nickel sheet smoothly, thereby removing the moisture in the sample tank 1.

[0030] As a preferred embodiment, a sand core filter 14 is installed in the suction filtration head 13. The sand core filter 14 is connected to the bottom of the ferromagnetic metal sheet 11. The sand core filter 14 plays a role in supporting the filter membrane layer 10 and the ferromagnetic metal sheet 11 while ensuring the water seepage effect during the suction filtration process.

[0031] As a preferred embodiment, the sampling device further includes a flared outlet section 15. One end of the sampling pipe 8 is sealed and penetrates into the sealed heating cavity 3 and is connected to the flared outlet section 15. The outlet of the flared outlet section 15 is arranged in the sample tank 1. The outlet of the flared outlet section 15 is spaced from the bottom of the sample tank 1, and the outlet of the flared outlet section 15 faces the bottom of the sample tank 1. The flared outlet section 15 is designed to guide the liquid sample to smoothly enter the sample tank 1, reduce impact and splash, and at the same time can prevent turbulence and bubble generation, adapt to different flow rates, improve the versatility of the equipment, and ensure the filtration efficiency.

[0032] As a preferred embodiment, the sampling device further includes a sampling funnel 16. One end of the sampling pipeline 8 located outside the sealed heating cavity 3 is communicated with the sampling funnel 16. During use, the water body to be measured and the magnetic adsorbent are added into the sampling pipeline 8 through the sampling funnel 16 and flow into the sample tank 1, and then the rinsing liquid is flushed into the sampling pipeline 8 through the sampling funnel 16 and flows into the sample tank 1. After the sampling of the water body to be measured and the magnetic adsorbent is completed, some substances such as nanoplastics inevitably adhere to the inner walls of the sampling funnel 16 and the sampling pipeline 8. Through rinsing with the rinsing liquid, the substances such as nanoplastics adhering to the inner walls of the sampling funnel 16 and the sampling pipeline 8 are rinsed into the sample tank 1, minimizing the loss of nanoplastics to the greatest extent.

[0033] As a preferred embodiment, the pyrolysis device is further provided with a carrier gas channel support pipe 20. The carrier gas channel support pipe 20 is longitudinally arranged in the sealed heating cavity 3. The bottom of the carrier gas channel support pipe 20 is hermetically communicated with the carrier gas inlet pipe 4, and the top of the carrier gas channel support pipe 20 is connected to the suction filter head 13. The suction filter head 13 together with the sample tank 1 is fixed in the sealed heating cavity 3. An air outlet pipe 19 is communicated with the body of the carrier gas channel support pipe 20. The carrier gas enters the carrier gas channel support pipe 20 from the carrier gas inlet pipe 4 and enters the sealed heating cavity 3 through the air outlet pipe 19, filling the sealed heating cavity 3 with the carrier gas. The suction filter head 13 is communicated with one end of the suction filter pipeline 23, and the other end of the suction filter pipeline 23 sequentially passes through the carrier gas channel support pipe 20 and the sealed heating cavity 3 and is communicated with the suction pump 24. As a further preferred embodiment, the carrier gas channel support pipe 20 is made of quartz material; the melting point of quartz is about 1650 °C and it can remain stable at high temperatures. In the heating cavity, quartz can resist the high temperature generated during the pyrolysis of nanoplastics and will not melt or deform.

[0034] As a preferred embodiment, the sealed heating cavity 3 includes a cover 21 with an opening facing downwards and a base 22. The bottom of the cover 21 is detachably and sealingly connected to the base 22. For example, the bottom of the cover 21 and the base 22 adopt a flange design and are detachably and sealingly connected through a sealing ring, ensuring the sealing performance while achieving quick disassembly and assembly, and improving the operation efficiency. As a further preferred embodiment, the suction filter head 13 is connected to one end of the suction filter pipe 23, and the other end of the suction filter pipe 23 passes through the base 22 and is connected to the suction pump 24. The suction filter pipe 23 located inside the sealed heating cavity 3 and the suction filter pipe 23 located outside the sealed heating cavity 3 are detachably and sealingly connected. During use, the cover 21 and the base 22 are disassembled and separated, the suction filter pipes 23 located inside and outside the sealed heating cavity 3 are disassembled and separated, and the cover 21 is removed to complete operations such as replacing the filter layer 9, which is convenient and fast. The suction filter pipe 23 located inside the sealed heating cavity 3 is preferably made of quartz material to resist the high temperature generated during pyrolysis; the suction filter pipe 23 located outside the sealed heating cavity 3 is preferably made of rubber material. As a further preferred embodiment, as the main structure of the sealed heating cavity 3, the cover 21 is made of quartz material. The melting point of quartz is 1650 °C. While having good heat preservation performance, heat resistance performance, and plasticity, it can resist the high temperature during pyrolysis, so it is selected to prepare the cover 21; the inner diameter is 57.8 mm, the wall thickness is 0.1 mm, and the overall height is 180 mm. This size ensures that the pyrolysis cavity has a relatively fast heating rate during heating.

[0035] As a preferred embodiment, the carrier gas can be an inert gas such as argon or helium. During the process of transporting the carrier gas into the sealed heating cavity 3, based on the characteristic that the pumping speed of argon by the vacuum pump is significantly higher than that of helium, argon is preferably used as the carrier gas, which not only meets the requirement of high-efficiency vacuum pumping in the sealed heating cavity 3 but also forms an inert protection atmosphere during the high-temperature process to prevent the ferromagnetic metal sheet 11 from oxidizing and extend the service life of key components.

[0036] As a preferred embodiment, the carrier gas inlet pipe 4 and the water vapor outlet pipe 5 are sealingly connected to the top of the sealed heating cavity 3, enabling the carrier gas, water vapor, and pyrolysis gas to be smoothly discharged from the sealed heating cavity 3.

[0037] As a preferred embodiment, the resistance wire 2 is a nickel-chromium alloy wire and is wound around the cavity wall of the sealed heating cavity 3 in multiple layers densely to improve the heating efficiency through intensive heating; the resistance wire 2 is sleeved in a quartz fiber sleeve. The quartz fiber sleeve has the advantages of high temperature resistance and insulation, and the long-term use temperature can reach 1050 °C. The adjacent resistance wires 2 are isolated from each other through the quartz fiber sleeve to ensure safety.

[0038] As a preferred embodiment, the sample cell 1 is a cylindrical cavity with an inner diameter of 47.8 mm, a height of 30 mm, and a thickness of 0.1 mm. Such a structural design allows for a relatively large amount of sample to be added during a single detection and also ensures that there is no moisture inside that could affect the mass spectrometry analysis results after suction filtration.

[0039] As a preferred embodiment, a heat-insulating layer 17 is wrapped and connected outside the sealed heating cavity 3. The heat-insulating layer 17 is connected with a high-silica cloth and a ceramic fiber blanket from the inside out. Among them, the high-silica cloth is a soft fabric made of heat-resistant and heat-insulating inorganic fibers and is used to cover the heating layer (i.e., the heating layer formed by winding resistance wires). The ceramic fiber blanket belongs to inorganic silicate materials, is fireproof, insulating, and heat-resistant, can withstand 1260 °C for long-term use, and can effectively prevent and / or slow down heat conduction. The thickness of the ceramic fiber blanket is preferably 3 cm, and the overall thickness of the heat-insulating layer 17 is preferably 5 cm. As a further preferred embodiment, an encapsulation layer 18 is wrapped and connected outside the heat-insulating layer 17. The encapsulation layer 18 is a Teflon high-temperature cloth, with a heat resistance of up to 260 °C, and is used to wrap and encapsulate the internal heat-insulating layer 17 to prevent the fiber particles in the heat-insulating layer 17 from falling off. The overall thickness of the encapsulation layer 18 is preferably 1 cm. The general pyrolysis temperature of nanoplastics is 300 - 500 °C. Under the above structure, the internal temperature of the pyrolysis chamber can be stably raised to 600 - 700 °C, thus meeting the requirements.

[0040] As a preferred embodiment, the filter 7 is a high-purity quartz wool filter to improve the filtering effect and further enhance the accuracy of detection.

[0041] By Figure 1 、 Figure 2 shown, this embodiment also provides a method for detecting nanoplastics based on magnetic adsorption - pyrolysis mass spectrometry technology. Using the nanoplastics detection device based on magnetic adsorption - pyrolysis mass spectrometry technology described in any one of the above, the steps are as follows: S1. Open the sampling pipeline 8 and rinse the sampling pipeline 8 with the rinsing solution. After completion of the rinsing, add the water body to be measured and the magnetic adsorbent into the sample cell 1 through the sampling pipeline 8, and then close the sampling pipeline 8. At this time, the water body to be measured in the sample cell 1 contains adsorbent - nanoplastics polymer, adsorbent, and unadsorbed nanoplastics.

[0042] S2. Start the suction filtration device to complete the separation of the adsorbent - nanoplastics polymer, adsorbent, unadsorbed nanoplastics, and water body in the sample cell 1. The adsorbent - nanoplastics polymer, adsorbent, and unadsorbed nanoplastics are enriched on the filter membrane layer 10 at the bottom of the sample cell 1, and then close the suction filtration device.

[0043] S3. Open the water vapor outlet pipe 5, start the resistance heating device, energize the resistance wire 2 to generate heat, cause the ferromagnetic metal sheet 11 to generate heat, the residual moisture in the sample cell 1 is heated to turn into water vapor, and the water vapor is discharged through the water vapor outlet pipe 5 to avoid the influence of water vapor on the mass spectrometry analysis results; control the temperature in the sealed heating chamber 3 so that the residual moisture in the sample cell 1 turns into water vapor, while the nano-plastics themselves do not undergo thermal cracking, and the thermal cracking temperature should be lower than the heat resistance temperature of the filter membrane layer 10.

[0044] S4. Close the water vapor outlet pipe 5, open the carrier gas inlet pipe 4 and the pyrolysis gas outlet pipe 6, and introduce carrier gas into the sealed heating chamber 3; increase the temperature in the sealed heating chamber 3 through the resistance heating device, so that the adsorbent-nano-plastic polymer and nano-plastics in the sample cell 1 undergo thermal cracking and turn into pyrolysis gas. Among them, the nano-plastics in the adsorbent-nano-plastic polymer undergo thermal cracking and turn into pyrolysis gas, and the adsorbent remains on the filter membrane layer 10 at the bottom of the sample cell 1; driven by the carrier gas, the pyrolysis gas is discharged through the pyrolysis gas outlet pipe 6, passes through the filter 7 and enters the mass spectrometry device 30 for detection and analysis, and completes the qualitative and quantitative analysis of nano-plastics.

[0045] As a preferred embodiment, in the above step S1, after the injection of the water body to be measured and the magnetic adsorbent, some nano-plastics will inevitably adhere to the inner wall of the injection pipe 8. Through rinsing with the rinsing solution, the attachments (including nano-plastics, etc.) on the inner wall of the injection pipe 8 are rinsed into the sample cell 1, minimizing the loss of nano-plastics during the experiment and further improving the accuracy of the nano-plastic test analysis results.

[0046] As a preferred embodiment, in the above step S1, the rinsing solution can be deionized water, distilled water, pure water, purified water, etc.

[0047] As a preferred embodiment, in the above step S1, the adsorbent can be magnetite modified with hexadecyltrimethoxysilane, which has been proven to be an efficient adsorbent, or other existing products can also be used. At the same time, when adding nano-plastic products and the adsorbent, the two will completely combine into a nano-plastic-adsorbent polymer and be magnetically adsorbed on the filter membrane layer 10 in the sample cell 1 through their own and the ferromagnetic metal sheet 11, ensuring the stability of the nano-plastics in the sample cell 1 during the processes of heating to remove water vapor and further heating for pyrolysis.

[0048] The above steps S3 and S4 are illustrated by an example: Suppose the temperature at which a certain nano-plastic turns into pyrolysis gas (i.e., the pyrolysis temperature) is 700 °C. The heating temperature can be first increased to 120 °C and maintained for 5 min. After the residual moisture in the sample cell 1 turns into water vapor and is discharged, then the heating temperature is increased to above 700 °C, so that the nano-plastics in the adsorbent-nano-plastic polymer and the unadsorbed nano-plastics undergo thermal cracking and turn into pyrolysis gas for subsequent detection and analysis by the mass spectrometry device 30.

[0049] For a better understanding of the working principle of the technical solution of the present invention, the specific embodiments are as follows: From Figure 1 , Figure 2 As shown, during use, open the sampling pipeline 8, first rinse the sample addition funnel 16 and the sampling pipeline 8 with pure water for 1 minute; then, simultaneously add the water sample to be measured and the adsorbent cetyltrimethoxysilane-modified magnetite into the sample addition funnel 16. After the addition is completed, wait for 5 minutes. During the 5 minutes when the water sample to be measured and the adsorbent flow to the sample tank 1 and wait, the two will completely combine into nanoplastics-adsorbent polymers and magnetically adsorb on the alumina filter membrane 10 directly above the nickel sheet by their own magnetism with the ferromagnetic metal sheet 11 (nickel sheet); rinse the sample addition funnel 16 and the sampling pipeline 8 with pure water and let the water flow into the sample tank 1, and then close the sampling pipeline 8.

[0050] Open the air pump 24 to filter the water sample in the sample tank 1 for 2 - 3 minutes. The nanoplastics-adsorbent polymers, the adsorbent, and the unadsorbed nanoplastics are retained on the alumina filter membrane, realizing the enrichment and separation of nanoplastics in the water sample. After the filtration is completed, close the air pump 24.

[0051] Subsequently, adopt the pyrolysis technology to apply high temperature to the sample tank 1 (especially the residues intercepted on the alumina filter membrane). Open the resistance heating device and simultaneously open the steam outlet pipe 5. Manipulate the temperature control program to heat the pyrolysis chamber to 100 - 150 °C and then maintain the temperature and continue to calcine for 5 - 10 minutes to volatilize all the remaining moisture inside the sample tank 1, thus avoiding the influence of steam on the accuracy of the mass spectrometry analysis results; when discharging the steam, due to the pressure difference formed by the different air pressures inside and outside the closed heating chamber 3, the steam moves upward and leaves the closed heating chamber 3 from the steam outlet pipe 5.

[0052] After observing that there is no water vapor in the water vapor outlet pipe 5, close the water vapor outlet pipe 5, open the pyrolysis gas outlet pipe 6, and operate the temperature control program to heat the pyrolysis chamber by calcination to 600 °C - 700 °C and then maintain the temperature for continuous calcination for 5 - 10 minutes, so that the nanoplastics and the unadsorbed nanoplastics in the nanoplastics-adsorbent polymer in the sample tank 1 are cracked into gas small molecules, namely pyrolysis gas; the pyrolysis gas enters the pyrolysis gas outlet pipe 6 under the carrier of argon, passes through the filter 7 and the capillary 25 and enters the mass spectrometry device 30; the flow rule of the gas is from a high-pressure environment to a low-pressure environment. Since the air pressure inside the mass spectrometry device 30 is lower, the gas inside the whole device, including the pyrolysis gas, flows from the sealed heating chamber 3 to the mass spectrometry device 30, and argon plays an auxiliary role in the flow of the pyrolysis gas; after the nanoplastics become pyrolysis gas on the surface of the alumina filter membrane, they flow directly upward, that is, in the direction of the mass spectrometry device 30, so there will be no situation where the pyrolysis gas remains in the sample tank 1. The mass spectrometry device 30 realizes the qualitative analysis of the nanoplastics category based on the characteristic ion peaks in the pyrolysis products, and completes the accurate quantitative analysis by measuring the peak area or peak height of the characteristic pyrolysis products.

[0053] The present invention provides a nanoplastics detection device and method based on magnetic adsorption-pyrolysis mass spectrometry technology. Compared with the conventional methods in the prior art: (1) In terms of structural design, the whole detection device includes a pyrolysis device, a resistance heating device, a sampling device, a sample tank 1, a suction filtration device, and a mass spectrometry device 30. After adding the water body to be tested and the magnetic adsorbent into the sample tank 1 through the sampling device, the nanoplastics are magnetically adsorbed together; first, use the suction filtration device to drain the water, then use the resistance heating device to heat the remaining water in the sample tank (including nanoplastics and the filter membrane layer) to turn it into water vapor and remove it, then raise the temperature to crack the nanoplastics into pyrolysis gas, and finally use the mass spectrometry device to conduct qualitative and quantitative analysis on the pyrolysis gas.

[0054] (2) In terms of function, the present invention can quickly, efficiently and systematically detect the content, types and changes in physical and chemical properties of nanoplastics in water bodies.

[0055] (3) Compared with the prior art, in terms of technical effects: ① By using the conventional method, 60 - 65% of the nanoplastics samples in the water body can be collected, and qualitative and quantitative analysis is carried out on them by using pyrolysis-gas-mass spectrometry method, etc. For the 35 - 40% of the nanoplastics samples that are not collected, the errors generated in the test results will ultimately lead to large deviations in the detection results of nanoplastics; by using the device of the present invention with magnetic adsorption-pyrolysis technology and directly sampling and suction filtering the water body to be tested, the process loss of the nanoplastics samples is greatly reduced, and 95% - 100% of the nanoplastics samples can be collected, ensuring the accuracy and reliability of the test results. ②Compared with the conventional magnetic adsorption-thermal cracking mass spectrometry that involves adsorption, filtration, thermal cracking, and mass spectrometry analysis, the device of the present invention integrates and breaks through the above steps, eliminating a large number of existing intermediate processes and thus greatly shortening the detection time. Using the conventional method, it takes about 9 hours from sample preparation to obtaining all analysis results. Using the device of the present invention, it takes 30 to 40 minutes.

[0056] ③Using the conventional method, it takes about 15 minutes to first mix the magnetic material and then add the sample for every 100 ml of water sample; using the device of the present invention, it takes about 3 minutes to add every 100 ml of water sample.

[0057] It should be noted that: (1) The mass spectrometry device 30 is an existing device, which includes a mass spectrometer and can be any one of a portable or desktop ion trap mass spectrometer, a quadrupole mass spectrometer, a triple quadrupole mass spectrometer, a time-of-flight mass spectrometer, a quadrupole-time-of-flight mass spectrometer, an ion trap-time-of-flight mass spectrometer, a magnetic mass spectrometer, etc. Its detection method also belongs to the prior art, that is, qualitative analysis of the nanoplastics category is carried out according to the characteristic ion peaks of the cracking products, and qualitative and quantitative detection and analysis of the nanoplastics are completed by measuring the peak area or peak height of the characteristic cracking products.

[0058] (2) In order to effectively control the opening or closing of the water vapor outlet pipe 5 and the cracking gas outlet pipe 6 and increase the anti-error function, a main pipe 29 is connected and arranged at the top of the closed heating cavity 3. The water vapor outlet pipe 5 and the cracking gas outlet pipe 6 are respectively connected in parallel with the main pipe 29. A first valve 26 is installed at the cross-connection position of the water vapor outlet pipe 5, the cracking gas outlet pipe 6 and the main pipe 29. The first valve 26 is an external rotary knob valve. By controlling and adjusting the control valve knob, the water vapor outlet pipe 5 and the cracking gas outlet pipe 6 are always kept in a state where one pipeline is open and the other pipeline is closed, achieving the purpose of anti-error.

[0059] In addition, second valves 27, third valves 28, and fourth valves (not marked in the figure) are respectively installed corresponding to the sample injection pipeline 8, the suction filtration pipeline 23, and the carrier gas inlet pipe 4 to open or close the corresponding pipelines.

[0060] (3) The present invention also preferably has a program temperature control device for heating and temperature sensing of the pyrolysis device, which belongs to the prior art. For example, after turning on the power of the program temperature control device, the program heating process is set through the control system: during this process, the temperature collected by the temperature measurement wire is converted into an electrical signal through the temperature conversion circuit, then received by the acquisition card, and then the output power of the heating module circuit is regulated through the PID algorithm of the control system, that is, the temperature of the resistance wire 2 is adjusted, and further the heating rate in the closed heating cavity 3 is regulated.

[0061] (4) The heat resistance temperature refers to the temperature range within which a material can maintain its physical and chemical properties in a high-temperature environment. The pyrolysis temperature refers to the temperature at which a material undergoes a decomposition reaction under high-temperature conditions.

[0062] (5) The sand core filter 14 is an existing device, preferably a quartz sand core filter.

[0063] (6) The present invention is applicable to the detection of nano plastics and also to the detection of micro plastics, both within the scope of protection.

[0064] The present invention provides a nano plastic detection device and method based on magnetic adsorption-pyrolysis mass spectrometry technology. Compared with the traditional detection methods that require complex pretreatment, through the integrated design of water body sampling, water sample / nano plastic separation and pyrolysis analysis, the present invention adopts direct sampling of water samples, and realizes the enrichment and separation of nano plastics in water samples through a suction filtration device, avoiding complex pretreatment steps, simplifying the operation process for accurately qualitatively and quantitatively detecting nano plastics, reducing the loss of nano plastics in the water samples to be detected in the operation process, and significantly reducing the operation difficulty and cost. Compared with the current detection methods for the adsorption performance of adsorbents and the detection methods for nano plastics, the present invention can quickly and accurately capture the content, types and physicochemical property change characteristics of nano plastics, and can simultaneously and accurately detect the adsorption performance of the adsorbent. This feature breaks through the current dilemma of synchronous, accurate and rapid analysis of nano plastic separation and detection technologies. It can reduce the influence of subjective judgment on the detection results, improve the accuracy of analysis, and at the same time provide information on the components, concentration and physicochemical properties of nano plastics. The present invention will provide more comprehensive, accurate and efficient technical support for the monitoring and assessment of nano plastic pollution and the screening of efficient adsorbents, and contribute to the in-depth development of the research field of nano plastic pollution.

[0065] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "left", "right", "upper", "lower", "top", "bottom", "front", "rear", "inner", "outer", "back", "middle", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present invention. It should be noted that in the above embodiments, the "first", "second" and "third" do not represent an absolute distinction relationship in terms of structure and / or function, nor do they represent the order of execution, but are only for the convenience of description.

[0066] The above are only the preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A nanoplastic detection device based on magnetic adsorption-pyrolysis mass spectrometry technology, comprising a pyrolysis device, a filter (7) and a mass spectrometry device (30), characterized in that: It also includes a resistance heating device, a sample injection device, a sample tank (1), and a filtration device; The resistance heating device is provided with a resistance wire (2); The pyrolysis device comprises a sealed heating cavity (3), the cavity wall of the sealed heating cavity (3) is wound with the resistance wire (2), the cavity wall of the sealed heating cavity (3) is respectively provided with a carrier gas inlet pipe (4), a water vapor outlet pipe (5), and a cracking gas outlet pipe (6) connected to the mass spectrometer (30), and the sample tank (1) is arranged in the sealed heating cavity (3); the filter (7) is installed in the cracking gas outlet pipe (6); The sampling device comprises a sampling pipeline (8), one end of which is sealed and penetrates into the sealed heating cavity (3) and is then connected to the sample tank (1); The bottom of the sample tank (1) is a filter layer (9), the filter layer (9) comprises a filter membrane layer (10) and a ferromagnetic metal sheet (11), the filter membrane layer (10) is connected to the ferromagnetic metal sheet (11), the filter pores of the filter membrane layer (10) have a pore size smaller than the particle size of the nanoplastic, the heat-resistant temperature of the filter membrane layer (10) is higher than the thermal cracking temperature of the nanoplastic, and the ferromagnetic metal sheet (11) is provided with a filtrate channel (12); The suction filtration device comprises a suction filtration head (13), wherein the suction filtration head (13) is arranged in the sealed heating cavity (3), and the suction filtration head (13) is connected to the sample tank (1) via the filter layer (9).

2. The nanoplastic detection device based on magnetic adsorption-pyrolysis mass spectrometry technology according to claim 1 is characterized in that: The filter membrane layer (10) is a high temperature resistant filter paper having a heat resistance temperature of above 700°C.

3. The nanoplastic detection device based on magnetic adsorption-pyrolysis mass spectrometry technology according to claim 1 is characterized in that: The ferromagnetic metal sheet (11) is a nickel sheet.

4. The nanoplastic detection device based on magnetic adsorption-pyrolysis mass spectrometry technology according to claim 1 is characterized in that: A sand core filter (14) is installed in the suction filter head (13), and the sand core filter (14) is connected to the bottom of the ferromagnetic metal sheet (11).

5. The nanoplastic detection device based on magnetic adsorption-pyrolysis mass spectrometry technology according to claim 1 is characterized in that: The sampling device further comprises a trumpet-shaped outlet section (15), one end of the sampling pipe (8) is sealed and penetrates into the sealed heating chamber (3) and is communicated with the trumpet-shaped outlet section (15), the outlet of the trumpet-shaped outlet section (15) is arranged in the sample tank (1), the outlet of the trumpet-shaped outlet section (15) is spaced from the bottom of the sample tank (1), and the outlet of the trumpet-shaped outlet section (15) faces the bottom of the sample tank (1).

6. The nanoplastic detection device based on magnetic adsorption-pyrolysis mass spectrometry technology according to claim 1 is characterized in that: The sample injection device further comprises a sample injection funnel (16), wherein the sample injection funnel (16) is arranged outside the sealed heating chamber (3) and is connected to the sample injection pipeline (8).

7. The nanoplastic detection device based on magnetic adsorption-pyrolysis mass spectrometry technology according to claim 1 is characterized in that: The pyrolysis device is also provided with a carrier gas channel support tube (20), and the carrier gas channel support tube (20) is longitudinally arranged in the closed heating cavity (3); the bottom of the carrier gas channel support tube (20) is sealed and connected to the carrier gas inlet tube (4), and the top of the carrier gas channel support tube (20) is connected to the suction filter head (13); the tube body of the carrier gas channel support tube (20) is connected to an air outlet pipe (19); the suction filter head (13) is connected to one end of the suction filter pipe (23), and the other end of the suction filter pipe (23) is sealed and successively passes through the carrier gas channel support tube (20), the closed heating cavity (3) and is connected to the suction pump (24).

8. The nanoplastic detection device based on magnetic adsorption-pyrolysis mass spectrometry technology according to claim 1 is characterized in that: The sealed heating cavity (3) comprises a cover body (21) with an opening facing downward and a base (22), wherein the bottom of the cover body (21) is detachably sealed and connected to the base (22); the suction filter head (13) is connected to one end of a suction filter pipe (23), and the other end of the suction filter pipe (23) passes through the base (22) and is connected to an air pump (24); the suction filter pipe (23) located inside the sealed heating cavity (3) is detachably sealed and connected to the suction filter pipe (23) located outside the sealed heating cavity (3).

9. A method for detecting nanoplastics based on magnetic adsorption-pyrolysis mass spectrometry, characterized in that: The nanoplastic detection device based on magnetic adsorption-pyrolysis mass spectrometry technology according to any one of claims 1 to 9 comprises the following steps: S1. Open the sampling pipe (8) and rinse the sampling pipe (8) with a rinse solution; after rinsing, add the water to be tested and the magnetic adsorbent into the sample tank (1) through the sampling pipe (8), and close the sampling pipe (8); S2. Start the filtration device to separate the adsorbent-nanoplastic polymer, adsorbent, unadsorbed nanoplastic and water in the sample tank (1), and then close the filtration device; S3. Open the water vapor outlet pipe (5), start the resistance heating device, and heat the resistance wire (2) so that the ferromagnetic metal sheet (11) generates heat, and the residual water in the sample tank (1) is converted into water vapor by the heat, and the water vapor is discharged through the water vapor outlet pipe (5); control the temperature in the closed heating chamber (3) so that the residual water in the sample tank (1) is converted into water vapor, and the nanoplastic itself does not undergo thermal cracking; S4. The water vapor outlet pipe (5) is closed, and the carrier gas inlet pipe (4) and the cracking gas outlet pipe (6) are opened to introduce the carrier gas into the sealed heating chamber (3); the temperature in the sealed heating chamber (3) is increased by a resistance heating device, so that the nanoplastics and the nanoplastics that have not been completely adsorbed in the adsorbent-nanoplastics polymer in the sample tank (1) are thermally cracked and converted into thermal cracking gas; driven by the carrier gas, the thermal cracking gas is discharged through the cracking gas outlet pipe (6), and enters the mass spectrometer (30) through the filter (7) for detection and analysis, thereby completing the qualitative and quantitative analysis of the nanoplastics.

10. The method for detecting nanoplastics based on magnetic adsorption-pyrolysis mass spectrometry technology according to claim 9, characterized in that: In the step S1, after the water body to be tested and the magnetic adsorbent are sampled, the rinse solution is used to flush the attachments on the inner wall of the sample injection pipe (8) into the sample tank (1).

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