Particle collection and thermal desorption integrated full-automatic device and application thereof in quantitative analysis of non-volatile components in chemical ionization time-of-flight mass spectrometry

Abstract

The invention belongs to the technical field of pollutant monitoring, and relates to a particulate matter collection and thermal desorption integrated full-automatic device and application of the particulate matter collection and thermal desorption integrated full-automatic device in quantitative analysis of non-volatile components in chemical ionization time-of-flight mass spectrometer.The particulate matter collection and thermal desorption integrated full-automatic device comprises a thermal desorption sampling unit, a particulate matter collection unit and an automatic control unit; a sample collection tray in the particulate matter collection unit comprises a cylindrical cavity and a conical cavity at the bottom of the cylindrical cavity, a ring groove is formed in the top of the cylindrical cavity, and a sealing ring, a screen and a filter membrane are arranged in the ring groove; a preheating airflow pipeline and a thermal desorption sampling pipeline are arranged at the two ends of the outer side wall of the cylindrical cavity; a gas discharge pipeline is arranged at the bottom of the conical cavity; the thermal desorption sample introduction unit comprises a convex heating body, and the convex part of the convex heating body can be hermetically connected with the cylindrical cavity in the sample collection tray. According to the invention, automatic switching of a plurality of working modes such as collection, analysis and sample introduction can be realized, pretreatment is not needed, and support is provided for particle source analysis and pollution prevention and control.

Description

Technical Field

[0001] This invention belongs to the field of pollutant source tracing and monitoring technology, specifically involving an integrated fully automated device for particulate matter collection and thermal desorption and its application in the quantitative analysis of non-volatile components using chemical ionization time-of-flight mass spectrometry. Background Technology

[0002] Air pollutants are fine particulate matter (PM2.5). 2.5 PM2.5 is a complex pollutant comprised of both haze pollution, primarily caused by PM2.5, and photochemical pollution, primarily caused by ozone (O3). 2.5 Secondary organic aerosols (SOA) constitute 30%-60% of atmospheric air, making them a key target for air pollution control. Organic carbon, as a core reactant in SOA formation and evolution, has attracted widespread attention due to its light-absorbing component—brown carbon (BrC)—due to its significant optical effects. Brown carbon not only reduces atmospheric visibility by absorbing solar radiation but also generates a direct radiative forcing effect (approximately 0.1-0.6 W / m²). 2 Brown carbon has a significant impact on regional climate and environment. Therefore, accurately analyzing the light absorption properties of brown carbon is of great scientific significance for improving atmospheric chemical models and formulating precise pollution prevention and control strategies.

[0003] However, the sources of brown carbon are extremely complex. Various precursors, such as aliphatic hydrocarbons, alkenes, and aromatic organic compounds, can be generated into brown carbon through atmospheric oxidation reactions. More importantly, brown carbon is not stable. Under the influence of atmospheric reactive substances (such as O3 and ·OH radicals), its chemical composition will continuously evolve dynamically. That is, the proportion of high oxidation state and high boiling point components increases, resulting in a longer residence time in the atmosphere and undergoing a complex cycle of "generation-reduction-secondary generation".

[0004] Currently, traditional offline analysis techniques (such as spectrometers and photometers) can only measure macroscopic absorption parameters (such as absorption coefficient and refractive index), and cannot obtain microscopic information such as molecular composition and oxidation state online and in situ. This seriously hinders the research process of parameterizing the absorption properties of brown carbon and embedding them into atmospheric models. To overcome these challenges, online analysis techniques such as single-particle aerosol mass spectrometry (SPAMS) and aerosol mass spectrometry (AMS) have been developed. In particular, the developed gas-phase and particulate phase sample introduction interface (FIGAERO), coupled with chemical ionization mass spectrometry (CIMS), has achieved simultaneous acquisition and thermal desorption analysis of gaseous and particulate samples, making a significant breakthrough in the analysis of oxygen-containing low-volatile organic compounds (OVOCs) in SOA. Furthermore, based on this technology, the oxygen-to-carbon ratio (O / C) has been introduced as a key parameter, successfully screening and parameterizing more than 330 oxygen-containing organic compounds, making outstanding contributions to revealing the formation mechanism of SOA and optimizing air quality models. Despite this, existing FIGAERO technology still faces the following challenges when applied to the study of brown carbon (especially non-volatile components): First, its nitrogen-heated thermal desorption method has low desorption efficiency for semi-volatile and non-volatile organic compounds, leading to systematic biases in the quantitative analysis of key components (such as organophosphates), constituting a fundamental bottleneck in the sensitivity of the analytical method. Second, the core three-interface platform lacks sufficient airtightness, easily causing sample leakage and cross-contamination during gas-phase / particulate phase switching, severely undermining the accuracy and reliability of the analytical results. Finally, the system is highly dependent on manual operation, with low automation, and cannot support long-term, continuous unattended monitoring, making it difficult to capture the dynamic evolution of the chemical composition of brown carbon. These problems severely restrict the in-depth application of this technology in revealing the quantitative relationship between the "structure-activity" of brown carbon and its environmental behavior. Summary of the Invention

[0005] The purpose of this invention is to provide an integrated fully automated device for particulate matter collection and thermal desorption and its application in the quantitative analysis of non-volatile components in chemical ionization time-of-flight mass spectrometry, thereby overcoming the shortcomings of existing technologies. It can efficiently collect fine particulate matter in the atmosphere and achieve rapid quantitative analysis of non-volatile components, with the advantages of high sensitivity, high stability and no need for any pretreatment.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: On one hand, the present invention provides an integrated fully automatic device for particulate matter collection and thermal desorption, including a particulate matter collection unit and a thermal desorption sample introduction unit. The particulate matter collection unit includes a sample collection tray, which includes a cylindrical cavity and a conical cavity at its bottom. The top of the cylindrical cavity is provided with a groove, and a polytetrafluoroethylene sealing ring is provided in the groove. The bottom of the cylindrical cavity is provided with a screen, and a filter membrane is provided on the screen. Sealing rings are provided on the top and sides of the screen. A preheating gas flow pipeline and a thermal desorption sample introduction pipeline are respectively horizontally provided at both ends of the outer wall of the cylindrical cavity. A gas exhaust pipeline is provided at the bottom of the conical cavity. The thermal desorption injection unit includes a raised heating element, the raised portion of which can be sealed to the cylindrical cavity in the sample collection tray. The raised heating element employs a hot gas flow-assisted vertical contact-separation heating technology, exhibiting excellent rapid heating performance.

[0007] This invention utilizes a raised heating element that forms a double-sealed structure with the sample collection tray, where a PTFE annular sealing ring and a filter membrane on the bottom screen create a tight seal. This completely eliminates bypass airflow and ensures that all airflow passes through the filter membrane. Simultaneously, the funnel-shaped space at the bottom of the screen guarantees smooth airflow, achieving highly efficient thermal desorption of particulate matter.

[0008] In some other embodiments, the thermal desorption sample introduction unit further includes a gas flow preheating device, which, in the direction of the gas flow, includes a heating tube, a thermally insulated tube, and a passivated metal sample introduction tube connected in sequence. The heating tube is connected to the thermal desorption sample introduction pipeline. The protruding heating element can rapidly and linearly heat up, and the gas flow preheating device can heat the gas flow in a short time, far exceeding the heating rate of traditional thermal desorption devices.

[0009] In some other embodiments, an automation unit is also included, which can control the particulate matter collection unit and the thermal desorption injection unit to automatically complete the collection and thermal desorption of particulate matter.

[0010] In some other implementations, the automation unit includes a robotic arm, a motor module, and supporting control software. The robotic arm possesses capabilities for precise sample tube gripping, high-precision three-dimensional spatial positioning, and intelligent path planning. Utilizing an existing structure, the robotic arm achieves a positioning accuracy of ±0.05mm and is equipped with a damping design to ensure smooth operation, allowing for continuous operation for over 24 hours.

[0011] The single-axis travel range of the motor module is 0-200 mm, the positioning accuracy is ±0.1 mm, and the moving speed is 10-200 mm / s.

[0012] In some other embodiments, the motor module includes a vertical motor module and a horizontal motor module. The vertical motor module includes a vertical motor and a vertical slide rail. The vertical motor is connected to the inverted protruding heating element and the cutting head, respectively. The cutting head is located above the horizontal position of the inverted protruding heating element. The vertical motor can move up and down along the vertical slide rail, thereby causing the protruding heating element or the cutting head to move up and down. The horizontal motor module includes a horizontal motor and a horizontal slide rail. The horizontal motor is connected to the sample collection tray. The horizontal motor can move horizontally back and forth along the horizontal slide rail, thereby moving the sample collection tray horizontally. Both the vertical and horizontal motor modules use stepper motors and are connected to the control software.

[0013] In some other embodiments, the cutting head has an existing structure and can be an impactor particulate sampler or a cyclone cutter, which uses gas dynamics to directly separate the desired particulate matter. The particulate matter falls directly onto the filter membrane with the airflow, without the need for external force to drive it to be crushed. Connecting pipes are provided on both sides of the cutting head to achieve PM2.5 particle sieving.

[0014] The total depth of the cylindrical cavity and the conical cavity is 10-100 mm, the inner diameter of the cylindrical cavity is 100-500 mm, the bottom outlet diameter of the conical cavity is 1-10 mm, and the cone angle is 20-60°. The diameter of the polytetrafluoroethylene sealing ring is 9-90 mm, the height is 10-100 mm, and the wall thickness is 1-10 mm. The sieve has a diameter of 100-500 mm, a mesh size of 50-500, and a thickness of 0.1-1 cm. The sieve is made of aluminum alloy or stainless steel and is equipped with a filter membrane.

[0015] In some other embodiments, the raised heating element has a raised height of 1-20 mm, a bottom diameter of 10-50 mm, is made of brass, silicon carbide or aluminum alloy, has an operating temperature of 100-600 ℃, a heating rate of 10-50 ℃ / min, and a temperature control accuracy of ±2 ℃. A thermocouple is also installed at the top of the end of the thermal insulation tube near the passivated metal sample inlet tube. Specifically, the thermocouple is a type K thermocouple with a high-precision proportional-integral-differential controller to ensure temperature stability of ±2℃ and temperature uniformity of ±5℃. The thermal insulation tube is made of ceramic or corundum.

[0016] In some other embodiments, a chemical ionization time-of-flight mass spectrometer is also included, wherein a passivated metal sample inlet tube is connected to the sample inlet of the chemical ionization time-of-flight mass spectrometer; The injection port in the chemical ionization time-of-flight mass spectrometer can also be connected to the gas phase sample injection port. This invention's chemical ionization time-of-flight mass spectrometer can not only quantitatively analyze semi-volatile and low-volatile organic compounds, but also quantitatively analyze gas phase samples and their contained volatile components.

[0017] It also includes an intelligent controller, which controls the fully automated particulate matter collection and thermal desorption unit and the chemical ionization time-of-flight mass spectrometer to automatically complete sample introduction and quantitative analysis. The intelligent controller has functions such as automatic calibration, multi-point programming, trajectory visualization and temperature monitoring, and supports manual / automatic mode switching.

[0018] On the other hand, the present invention provides a method of using a fully automated particulate matter collection and thermal desorption integrated device, comprising the following steps: First, close the valves on the preheating gas flow line and the thermal desorption sample inlet line, then open the valve on the gas discharge line; then, the horizontal motor drives the sample collection tray to move horizontally to below the cutting head line; next, the vertical motor drives the cutting head and its connected line to move downward and press down into the sample collection tray to make close contact with the filter membrane on the screen, ensuring that the sample gas in the cutting head and its connected line passes through the filter membrane to sample particulate matter; After particulate matter sampling is completed, the valve on the gas emission pipeline is closed first, and the raised heating element and the preheating gas flow pipeline are preheated to the set temperature. The horizontal motor drives the sample collection tray to move horizontally to below the raised heating element. Then, the vertical motor drives the raised part of the raised heating element to move downward and press it into the sample collection tray. Then, the valves on the preheating gas flow pipeline and the thermal desorption injection pipeline are opened to perform thermal desorption injection. Thermal desorption analysis is performed by chemical ionization time-of-flight mass spectrometry. After thermal desorption analysis, increase the purging flow rate of the gas in the cutting head to purge the sample in the sample collection tray until there is no obvious background interference residue. Finally, the vertical motor drives the raised heating element to move upward and lift it from the sample collection tray. After the sample collection tray cools down, the robotic arm replaces the sample collection tray with a new one for the next sample injection analysis.

[0019] In some other embodiments, the particulate matter is brown carbon particulate matter in air pollution, which contains one or more of organophosphates, polycyclic aromatic hydrocarbons, and nitro aromatic hydrocarbons; specifically, the brown carbon particulate matter contains one or more of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate.

[0020] The particulate matter sampling time is 5-60 min, the preheating temperature of the raised heating element and the preheated gas flow pipeline is 300-400 ℃, the thermal desorption injection time is 2-5 min, the zero gas purge flow rate is 200-300 mL / min, the sample gas flow rate is 50-120 mL / min, and the purge flow rate after thermal desorption analysis is 1000-2000 mL / min.

[0021] The beneficial effects of this invention are: (1) The hot airflow-assisted vertical heating technology used in this invention achieves efficient and rapid heating and control. The heating element achieves rapid linear temperature rise from room temperature to 350 ℃ within 120 s, and the airflow preheating unit can reach 110 ℃ in only 28 s, with a heating rate far exceeding that of traditional devices. The integrated high-precision K-type thermocouple and PID (proportional-integral-derivative) controller ensure that the temperature stability of the working area is better than ±2 ℃ and the temperature uniformity reaches ±5 ℃, providing a reliable thermal field environment for the graded thermal desorption of different volatile components.

[0022] (2) The present invention adopts a double sealing structure combining a PTFE annular sealing ring and an O-ring, which forms a tight contact with the filter membrane under the action of the driving mechanism, completely eliminating bypass airflow and ensuring that 100% of the aerosol sample passes through the filter membrane, thus achieving complete capture of particulate matter. Through the funnel-shaped screen bottom design, the flow resistance is effectively reduced while ensuring sealing, ensuring smooth airflow and efficient collection under high flow rate sampling.

[0023] (3) This invention, through an integrated program-controlled automated robotic arm, can achieve seamless automatic switching between multiple working modes such as collection, analysis, and sample introduction, completely eliminating manual intervention. The robotic arm has a positioning accuracy of up to ±0.05 mm and adopts a damping design to ensure smooth operation, supporting continuous uninterrupted operation for more than 24 hours, meeting the needs of long-term online monitoring. The supporting control software has functions such as automatic calibration, multi-point programming, real-time trajectory visualization, and temperature monitoring, supports manual / automatic dual modes, is easy to operate, and has high reliability. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 This is a schematic diagram of the overall structure of the fully automated particulate matter collection and thermal desorption integrated device coupled with the photochemical ionization time-of-flight mass spectrometry system in Example 1; Figure 2 This is a top view of the sample collection tray in the fully automated particulate matter collection and thermal desorption integrated device of Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the thermal desorption sample introduction unit in the fully automated particulate matter collection and thermal desorption integrated device of Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the operation process of the fully automated particulate matter collection and thermal desorption integrated device of the present invention. Figure 5 This is a linear fitting graph of the standard samples of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate detected by the fully automated particulate matter collection and thermal desorption integrated device in Embodiment 2 of the present invention. Figure 6 This is a mass spectrometry spectrum of organic phosphate esters in environmental particulate matter detected by the fully automated device integrating particulate matter collection and thermal desorption in Embodiment 3 of the present invention. Figure 7 This is a bar chart comparing the collection efficiency and characteristic peak intensity of the present invention with those of commercial instruments; The components include: a cutting head 1, a sample collection tray 2, a polytetrafluoroethylene sealing ring 3, a sieve 4, a gas emission pipeline 5, a preheated gas flow pipeline 6, a thermal desorption sample injection pipeline 7, a raised heating element 8, a gas flow preheating device 9, a heating tube 10, a heat insulation tube 11, a passivated metal sample injection tube 12, a thermocouple 13, a robotic arm 14, and a motor module 15. Furthermore, the spacing or dimensions between parts have been exaggerated to show their positions; the diagram is for illustrative purposes only. Detailed Implementation

[0026] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components whose manufacturers are not specified are all commercially available conventional products.

[0027] As described in the background section, the existing FIGAERO technology still has three main drawbacks: nitrogen gas thermal desorption injection has low desorption efficiency for semi-volatile and low-volatile organic compounds, making it difficult to achieve quantitative analysis of non-volatile organic compounds such as organophosphates; the three-interface platform used for sample transfer has insufficient airtightness, limiting the application of FIGAERO in the quantitative analysis of particulate matter components; in addition, it lacks automated operation capabilities, requiring manual intervention for sample replacement and system maintenance, which cannot meet the needs of long-term continuous monitoring.

[0028] This invention addresses these issues by developing a novel thermal desorption technology to improve the desorption efficiency of non-volatile organic compounds (NVCs). It also improves the interface platform design to optimize the sealing structure and enhance airtightness, develops a composite sample introduction system to combine the advantages of multiple desorption technologies, and achieves all-weather unattended monitoring through an integrated program-controlled automated robotic arm system. This resulted in the successful development of a novel fully automated device integrating particulate matter collection and thermal desorption, along with its quantitative analysis method. This device overcomes the limitations of traditional thermal desorption technology, enabling rapid desorption and quantitative monitoring of non-volatile components in particulate matter.

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments: Example 1 This embodiment provides a system for coupling a fully automated particulate matter collection and thermal desorption device with photochemical ionization time-of-flight mass spectrometry, the specific components of which are as follows: Figure 1 As shown, the system includes an integrated fully automated particulate matter collection and thermal desorption device and a photochemical ionization time-of-flight mass spectrometer. The integrated fully automated particulate matter collection and thermal desorption device comprises a particulate matter collection unit, a thermal desorption sample introduction unit, and an automated control unit.

[0030] like Figure 2 As shown, the particulate matter collection unit includes a cutting head 1 and a sample collection tray 2. The cutting head 1 is an existing device, which can be a PM2.5 cutting head. The cutting head 1 has an existing structure and can be either an impactor-type particulate sampler or a cyclone cutter. It utilizes gas dynamics to directly separate the desired particulate matter, which falls directly into the sample collection tray 2 with the airflow, without the need for external force to crush it, thus achieving the collection of samples of a specific particle size. The sample collection tray 2 has a funnel-shaped cavity structure, specifically including a cylindrical cavity and a conical cavity at its bottom. The total depth of the cylindrical and conical cavities is 10-100 mm, the inner diameter of the cylindrical cavity is 100-500 mm, the bottom outlet diameter of the conical cavity is 1-10 mm, and the cone angle is 20-60°.

[0031] The cylindrical cavity has a groove at its top, within which a polytetrafluoroethylene (PTFE) sealing ring 3 is installed. The PTFE sealing ring 3 has a diameter of 9-90 mm, a height of 10-100 mm, and a wall thickness of 1-10 mm. The PTFE sealing ring 3 seals the sample collection tray to ensure airtightness and prevent sample leakage and cross-contamination. The bottom of the cylindrical cavity has a sieve 4, with O-rings integrated on its top and sides. The sieve 4 has a diameter of 100-500 mm, a mesh size of 50-500 mesh, and a thickness of 0.1-1 cm. A filter membrane is also installed on the sieve 4. Both the sieve 4 and sieve 7 are made of aluminum alloy or stainless steel. The bottom of the conical cavity has a gas exhaust pipe 5, equipped with a valve, used to discharge waste gas that has passed through the filter membrane. At both ends of the outer wall of the cylindrical cavity, a preheated gas flow pipe 6 and a thermal desorption sample inlet pipe 7 are horizontally installed. A valve is installed on the preheating airflow pipeline 6, which is used to introduce preheated air into the sample collection tray 2 to facilitate sample heating. A valve is installed on the thermal desorption injection pipeline 7, which is used to transport the thermally desorbed sample to the thermal desorption injection unit.

[0032] like Figure 3 As shown, the thermal desorption sample introduction unit includes a raised heating element 8 and a gas flow preheating device 9. The raised heating element 8 has a raised height of 1-20 mm and a bottom diameter of 10-50 mm. The raised heating element 8 is made of brass, silicon carbide, and aluminum alloy, which are good thermal conductive materials. The operating temperature range of the raised heating element 8 is 100-600 ℃, the heating rate is adjustable from 10-50 ℃ / min, and the temperature control accuracy is ±2 ℃. The desorption temperature and heating program can be optimized according to different sample characteristics to achieve complete desorption of medium / high boiling point compounds. The gas flow preheating device 9 is connected to the sample inlet of the photochemical ionization time-of-flight mass spectrometer. The airflow preheating device 9, arranged in the airflow direction, includes a heating tube 10, a heat-insulating tube 11, and a passivated metal sample inlet tube 12 connected in sequence. The heating tube 10 is connected to the thermal desorption sample inlet line 7 via a pneumatic connector. A thermocouple 13 is also installed at the top of the heat-insulating tube 11 near the passivated metal sample inlet tube 12. Specifically, the thermocouple 13 is a type K thermocouple with a high-precision proportional-integral-differential controller to ensure temperature stability of ±2℃ and temperature uniformity of ±5℃. The heat-insulating tube 11 is made of heat-resistant materials such as ceramic or corundum.

[0033] The automation control unit includes a robotic arm 14, a motor module 15, and supporting control software. The robotic arm 17 can utilize an existing structure. The robotic arm 14 possesses precise sample tube gripping, high-precision three-dimensional spatial positioning, and intelligent path planning capabilities, with a repeatability better than ±0.05 mm. A damping design ensures smooth and undisturbed movement, and it can operate continuously and stably for over 24 hours. The motor module 15 includes a vertical motor module and a horizontal motor module. The single-axis travel range of the motor module 18 is 0-200 mm, with a positioning accuracy of ±0.1 mm and an adjustable movement speed range of 10-200 mm / s, enabling free switching between sample collection and thermal desorption modes.

[0034] Specifically, the vertical motor module includes a vertical motor and a vertical slide rail. The vertical motor is connected to the inverted raised heating element 8 and the cutting head 1, with the cutting head 1 located on top of the inverted raised heating element 8. The vertical motor can move up and down along the vertical slide rail, thereby moving the raised heating element 8 or the cutting head 1 up and down. The horizontal motor module includes a horizontal motor and a horizontal slide rail. The horizontal motor is connected to the sample collection tray 2. The horizontal motor can move horizontally back and forth along the horizontal slide rail, thereby moving the sample collection tray 2 horizontally. Both the vertical and horizontal motor modules use stepper motors and are connected to the control software. The control software has functions such as automatic position calibration, multi-point program storage, motion trajectory visualization, abnormal alarm, and temperature control. It supports manual / automatic dual-mode switching, enabling the movement and positioning of the sample tray and ensuring high repeatability and stability of the sample injection process.

[0035] The photochemical ionization time-of-flight mass spectrometer (CIFMS) can utilize existing structures, and its inlet can be connected to a gas phase sample inlet. Therefore, this CIFMS can not only quantitatively analyze semi-volatile and low-volatile organic compounds, but also quantitatively analyze gas phase samples and their volatile components. Furthermore, to achieve intelligent control, both the integrated fully automated particulate matter collection and thermal desorption device and the CIFMS are connected to an intelligent controller (such as a computer), enabling programmed control of temperature, airflow, and motor speed. Simultaneously, through preset desorption programs, operators can select optimal desorption conditions based on different sample characteristics, improving analytical efficiency and accuracy. This makes the entire system suitable for particulate matter sample collection and the quantitative detection and analysis of its non-volatile components.

[0036] Depending on the operating mode of the motor module 15 in the automated control unit, the integrated fully automatic particulate matter collection and thermal desorption device has two working modes: particulate matter collection mode and thermal desorption mode. Figure 4 As shown, the details are as follows: In particle collection mode: First, close the valves on the preheated gas flow line 6 and the thermal desorption sample inlet line 7 in the sample collection tray 2. Then, open the valve on the gas discharge line 5 at the bottom of the sample collection tray 2. Next, the horizontal motor drives the sample collection tray 2 to move horizontally below the cutting head line. Then, the vertical motor drives the cutting head 1 and its connected lines to move downwards and press down into the sample collection tray 5, so that the PTFE annular sealing ring 3 makes tight contact with the filter membrane on the sieve 4, completely eliminating bypass airflow and ensuring that the sample gas in the cutting head 1 and its connected lines passes through the filter membrane to sample particulate matter. The conical space designed at the bottom of the sieve 4 ensures smooth airflow and achieves efficient particulate matter sampling.

[0037] In thermal desorption mode: First, close the valve on the gas exhaust pipe 8 at the bottom of the sample collection tray 2, preheat the raised heating element 8 and the preheating gas flow pipe 6 to the set temperature, and drive the horizontal motor to move the sample collection tray 2 horizontally below the raised heating element 8; then, drive the vertical motor to move the raised part of the raised heating element 8 downward and press it into the sample collection tray 2, and then open the valves on the preheating gas flow pipe 6 and the thermal desorption injection pipe 7 in the sample collection tray 2, and then perform thermal desorption injection. Perform thermal desorption analysis by chemical ionization time-of-flight mass spectrometry, continuously monitor the intensity of characteristic peaks, and save the real-time monitoring data and corresponding mass spectrometry.

[0038] After thermal desorption analysis, increase the purge flow rate to purge the sample in sample collection tray 2 until there is no obvious background interference residue.

[0039] Finally, the vertical motor in the motor module 15 drives the raised heating element 8 to move upward and lift it from the sample collection tray 2. The sample collection tray 2 is cooled down, and after cooling, the robotic arm 14 replaces the sample collection tray 2 according to the predetermined program.

[0040] Example 2 This embodiment provides a method for quantitative analysis of standard samples using the fully automated particulate matter collection and thermal desorption integrated device coupled with a photochemical ionization time-of-flight mass spectrometry system described in Embodiment 1. This method eliminates the need to collect particulate matter from the environment and includes the following steps: First, the motor module assists in switching to thermal desorption mode, where the raised heating element and the purge gas in the preheated gas flow line are preheated to a preset temperature of 350℃. After adding 10 μL of standard sample solution to the center of the sample collection tray, the vertical motor drives the raised portion of the raised heating element to move downwards and press it into the sample collection tray. The valves on both the thermal desorption injection line and the preheated gas flow line are opened, while the valve on the gas exhaust line is closed. Then, thermal desorption injection is performed for 2 min, with a zero-gas purge flow rate of 240 mL / min and a standard sample solution flow rate of 60 mL / min. Characteristic peak intensities are continuously monitored, and real-time monitoring data and corresponding mass spectra are saved. After thermal desorption analysis, the purge flow rate is increased to 1000 mL / min and purges continue until the sample collection tray is clean and free of significant background interference. Finally, the vertical motor drives the raised heating element to rise, and the sample collection tray cools to room temperature.

[0041] Figure 5 Linear fitting plots were generated for the measurements of 0.1-20 ng standard samples of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate, respectively, following the above procedure. (See attached image.) Figure 5 It can be seen that the standard samples of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate all have good linear fitting properties, R0 2 All values ​​are greater than 0.99, indicating that this application can achieve rapid analysis and quantitative monitoring of non-volatile components in particulate matter.

[0042] Example 3 This embodiment provides a novel fully automated device for integrated particulate matter collection and thermal desorption, as described in Embodiment 1, coupled with photochemical ionization time-of-flight mass spectrometry, for direct sampling and real-time analysis of environmental particulate matter samples, including the following steps: The experiment was conducted at the Shandong University (Qingdao Campus) Express Delivery Center. The sampling module of the integrated thermal desorption device was used for 1 hour of sampling per run (the sample collection process was the same as in Example 1). The motor-assisted switching to thermal desorption mode was performed, where the raised heating element and the purge gas in the preheated gas flow line were preheated to a preset temperature of 400℃. Valves in the thermal desorption injection line and the preheated gas flow line were opened, while the valve in the gas exhaust line was closed. Thermal desorption injection was then performed for 3 minutes, with a zero-gas purge flow rate of 300 mL / min and a reagent gas flow rate of 100 mL / min. Characteristic peak intensities were continuously monitored, and real-time monitoring data and corresponding mass spectrometry spectra were saved. After thermal desorption analysis, the purge flow rate was increased to 2000 mL / min and purged until the sample collection tray was clean and no significant background interference remained.

[0043] Figure 6 The image shown is an actual sample spectrum. Figure 6It is known that rapid analysis and quantitative monitoring of non-volatile components such as triethyl phosphate and tributyl phosphate in particulate samples in the environment can be achieved.

[0044] Comparative Example 1 In a laboratory setting, a comparative experiment was conducted with the commercially available FIGAERO instrument. Data was collected for 1 hour at a pumping rate of 20 L / min under conditions of 25℃ and 50% relative humidity. Subsequently, the thermal desorption temperature was set to 300℃, the purge flow rate to 300 mL / min, and mass spectrometry was connected for analysis. Finally, the particulate matter collection rate was calculated.

[0045] Figure 7 This is a bar chart comparing the collection efficiency and characteristic peak intensity of the present invention with those of commercially available instruments. Figure 7 It can be seen that the system of the present invention exceeds FIGAERO 22.25%, and the characteristic peak signal intensity exceeds FIGAERO 75.44%.

[0046] In summary, the system and quantitative analysis method of this invention can be used for direct sampling and real-time analysis of environmental particulate matter samples without cumbersome pretreatment, providing strong scientific support for particulate matter source apportionment and pollution control.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An integrated device for particulate matter collection and thermal desorption, characterized in that, The device includes a particulate matter collection unit and a thermal desorption sample introduction unit. The particulate matter collection unit includes a sample collection tray, which comprises a cylindrical cavity and a conical cavity at its bottom. The top of the cylindrical cavity has a groove with a polytetrafluoroethylene (PTFE) sealing ring inside. The bottom of the cylindrical cavity has a sieve with a filter membrane on it, and sealing rings are provided on the top and sides of the sieve. A preheating gas flow line and a thermal desorption sample introduction line are horizontally arranged at both ends of the outer wall of the cylindrical cavity, respectively. The bottom of the conical cavity has a gas exhaust line. The thermal desorption injection unit includes a raised heating element, wherein the raised portion of the raised heating element can be sealed to the cylindrical cavity in the sample collection tray.

2. The integrated particulate matter collection and thermal desorption device according to claim 1, characterized in that, The thermal desorption injection unit also includes a gas flow preheating device, which, in the direction of gas flow, includes a heating tube, a heat-insulating tube, and a passivated metal injection tube connected in sequence; wherein, the heating tube is connected to the thermal desorption injection pipeline.

3. The integrated particulate matter collection and thermal desorption device according to claim 1, characterized in that, It also includes an automation unit, which can control the particulate matter collection unit and the thermal desorption injection unit to automatically complete the collection and thermal desorption of particulate matter.

4. The integrated particulate matter collection and thermal desorption device according to claim 3, characterized in that, The automation unit includes a robotic arm, a motor module, and supporting control software; the robotic arm has the capabilities of precise grasping, high-precision three-dimensional spatial positioning, and intelligent path planning. The single-axis travel range of the motor module is 0-200 mm, the positioning accuracy is ±0.1 mm, and the moving speed is 10-200 mm / s.

5. The integrated particulate matter collection and thermal desorption device according to claim 4, characterized in that, The motor module includes a vertical motor module and a horizontal motor module. The vertical motor module includes a vertical motor and a vertical slide rail. The vertical motor is connected to the inverted raised heating element and the cutting head, respectively. The cutting head is located above the inverted raised heating element at a parallel position. The vertical motor can move up and down along the vertical slide rail, thereby causing the raised heating element or the cutting head to move up and down. The horizontal motor module includes a horizontal motor and a horizontal slide rail. The horizontal motor is connected to the sample collection tray. The horizontal motor can move horizontally back and forth along the horizontal slide rail, thereby moving the sample collection tray horizontally. Both the vertical and horizontal motor modules use stepper motors and are connected to the control software.

6. The integrated particulate matter collection and thermal desorption device according to claim 1, characterized in that, The total depth of the cylindrical cavity and the conical cavity is 10-100 mm, the inner diameter of the cylindrical cavity is 100-500 mm, the bottom outlet diameter of the conical cavity is 1-10 mm, and the cone angle is 20-60°. The polytetrafluoroethylene sealing ring has a diameter of 9-90 mm, a height of 10-100 mm, and a wall thickness of 1-10 mm. The screen has a diameter of 100-500 mm, a mesh count of 50-500, and a thickness of 0.1-1 cm; the screen is made of aluminum alloy or stainless steel.

7. The integrated particulate matter collection and thermal desorption device according to claim 2, characterized in that, The raised heating element has a raised height of 1-20 mm, a bottom diameter of 10-50 mm, and is made of brass, silicon carbide, or aluminum alloy. Its working temperature is 100-600 ℃, its heating rate is 10-50 ℃ / min, and its temperature control accuracy is ±2 ℃. A thermocouple is also provided at the top of the end of the heat-insulating tube near the passivated metal sample tube. The heat-insulating tube is made of ceramic or corundum.

8. The integrated particulate matter collection and thermal desorption device according to claim 2, characterized in that, It also includes chemical ionization time-of-flight mass spectrometry, with a passivated metal sample inlet tube connected to the sample inlet of the chemical ionization time-of-flight mass spectrometer; It also includes an intelligent controller, which controls the integrated particulate matter collection and thermal desorption device and the chemical ionization time-of-flight mass spectrometer to automatically complete sample introduction and quantitative analysis.

9. A method of using the integrated particulate matter collection and thermal desorption device according to any one of claims 1-8, characterized in that, Includes the following steps: First, close the valves on the preheating gas flow line and the thermal desorption sample inlet line, then open the valve on the gas discharge line; then, the horizontal motor drives the sample collection tray to move horizontally to below the cutting head; next, the vertical motor drives the cutting head and its connected pipeline to move downward and press down into the sample collection tray to make close contact with the filter membrane on the sieve, ensuring that the sample gas in the cutting head and its connected pipeline passes through the filter membrane to sample particulate matter; After particulate matter sampling is completed, the valve on the gas emission pipeline is closed first, and the raised heating element and the preheating gas flow pipeline are preheated to the set temperature. The horizontal motor drives the sample collection tray to move horizontally to below the raised heating element. Then, the vertical motor drives the raised part of the raised heating element to move downward and press it into the sample collection tray. Then, the valves on the preheating gas flow pipeline and the thermal desorption injection pipeline are opened to perform thermal desorption injection. Thermal desorption analysis is performed by chemical ionization time-of-flight mass spectrometry. After thermal desorption analysis, increase the gas flow rate to purge the sample in the sample collection tray until there is no obvious background interference residue. Finally, the vertical motor drives the raised heating element to move upward and lift it from the sample collection tray. After the sample collection tray cools down, the robotic arm replaces the sample collection tray with a new one for the next sample injection analysis.

10. The method of using the integrated particulate matter collection and thermal desorption device according to claim 9, characterized in that, The particulate matter is brown carbon particulate matter in air pollution, which contains one or more of the following: organic phosphate esters, polycyclic aromatic hydrocarbons, and nitro aromatic hydrocarbons. The particulate matter sampling time is 5-60 min, the preheating temperature of the raised heating element and the preheated gas flow pipeline is 300-400℃, the thermal desorption injection time is 2-5 min, the zero gas purge flow rate is 200-300 mL / min, the sample gas flow rate is 50-120 mL / min, and the purge flow rate of the gas after thermal desorption analysis is 1000-2000 mL / min.

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