CN118837176A - Online nanoscale particulate matter thermal desorption sample inlet system combined with orbitrap mass spectrum - Google Patents

Abstract

The invention belongs to the technical field of environmental monitoring, and particularly relates to an online nanoscale particulate matter thermal desorption sample feeding system combined with an orbitrap mass spectrum. The invention comprises a filtering device, a particle size screening device, a suspension thermal desorption device, a reaction chamber, an ion source and a numerical control center which are connected in series; the filtering device is used for removing gaseous species in the atmospheric sample; the particle size screening device comprises a cutting disc with micron-sized small holes and a guide disc, and can control the screening particle size; the suspension thermal desorption device consists of a thermal desorption column and a heating system; the reaction chamber is provided with an ion source and a reaction cavity, and the reaction time is controlled by adjusting the distance between the ion source and a mass spectrum sample inlet; the numerical control center is used for cooperatively controlling the particle size screening device, the suspension thermal desorption device, the reaction chamber and the ion source. The invention can perform nano particle screening and thermal desorption on line, and realize the on-line measurement of chemical components of nano particles by combining with orbitrap mass spectrometry. The system has wide application prospect in the field of air pollution control.

Description

An online nanoparticle thermal desorption injection system coupled to an orbitrap mass spectrometer

Technical Field

The invention belongs to the technical field of environmental monitoring, and in particular relates to an online nano-scale particle thermal desorption sampling system coupled with an orbital trap mass spectrometer.

Background Art

Atmospheric particulate matter (PM) is solid particles or droplets suspended in the air, and its sources include industrial emissions, traffic exhaust, natural dust and biological emissions. These particles are divided into coarse particles (PM ₁₀ , less than 10 microns in diameter), fine particles (PM _2.5 , less than 2.5 microns in diameter) and ultrafine particles (nanoscale, less than 0.1 microns in diameter) according to their equivalent diameter. Fine particles and nanoparticles can penetrate deep into the respiratory tract and lungs, enter the blood circulation system, and cause and aggravate diseases such as asthma, bronchitis, cardiovascular disease, and lung cancer, with significant negative environmental health effects. Nanoparticles have a larger specific surface area and activity due to their extremely small size, and can penetrate biological membranes, causing cell and tissue damage. Fine particles and nanoparticles can also serve as condensation nuclei for cloud droplets and ice crystals, affecting local and global climate. Research on atmospheric particulate matter, especially nanoparticles, is of great significance for pollution source identification and control, health risk assessment, and climate change research.

In the field of atmospheric environment, effective screening of nanoparticles of different sizes is crucial for assessing air quality and studying pollution sources. The main screening methods currently include online and offline technologies. Online methods provide instant data through real-time monitoring. Commonly used equipment includes optical particle size analyzer (OPC), electric mobility particle size spectrometer (SMPS) and quartz crystal microbalance (QCM). These instruments are based on the principles of light scattering, electric mobility and mass detection, and can continuously monitor nanoparticles in the atmosphere and respond to environmental changes and pollution events in a timely manner. However, these devices are usually expensive and complex, and cannot achieve simultaneous measurement of the chemical components of nanoparticles, which limits their wide application. Offline screening methods perform detailed analysis after sampling. Commonly used equipment includes nanoporous membrane filters and electrodeposition equipment. Offline methods are suitable for detailed chemical analysis and particle composition research, which helps to understand the pollution sources and environmental behavior of particles. However, these methods are usually time-consuming, cannot provide real-time data, and may be contaminated or lost during sample processing, affecting the accuracy of the results. The main drawbacks at present are the high operating cost and maintenance complexity of online methods, the inability to achieve simultaneous measurement of the chemical components of nanoparticles, and the time delay and sample integrity problems of offline methods. In addition, although existing screening devices have made significant progress in precision and efficiency, for particles smaller than 50 nanometers, the screening precision and accuracy may be affected by particle aggregation and adhesion.

Thermal desorption technology is used to extract low-volatile and ultra-low-volatile organic compounds from particulate matter for further analysis. Common thermal desorption methods and instruments include the following: 1) Thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS): The organic compounds in the particulate matter are released by heating using a thermal desorber, and then separated by gas chromatography and then enter the mass spectrometer for qualitative and quantitative analysis; 2) Thermogravimetric analysis (TGA): By controlling the increase in temperature, the mass change of the particulate matter is measured to analyze its thermal stability and composition; 3) Thermal desorption-secondary thermal desorption-gas chromatography-mass spectrometry (TD/TD-GC-MS): The volatile components are removed by primary thermal desorption, and then the residual non-volatile components are analyzed by secondary thermal desorption. TD-GC-MS has high sensitivity and a wide range of applications, but it is costly, has a long analysis time and is complex to operate, and cannot achieve high time resolution online measurement. TGA is easy to operate and suitable for thermal stability analysis, but it cannot provide detailed chemical structure information. Although TD/TD-GC-MS can comprehensively analyze different components, the process is complicated and the equipment is expensive, and it is also unable to achieve real-time high-time resolution online measurement. The existing particulate matter thermal desorption method still has great limitations in operation complexity, equipment cost and analysis time. By optimizing the analysis method, the chemical composition information of particulate matter can be obtained more accurately, which will help environmental monitoring and pollution control.

In mass spectrometry, the ionization of gaseous samples is one of the key steps. Different ionization methods and reaction chambers are suitable for different analysis requirements and sample types. Electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) are commonly used ionization methods for orbital trap mass spectrometry. The applicability of these methods to gaseous samples has the following problems: the ESI method is usually used for liquid samples. Liquid samples are sprayed into the electric field through a capillary to form charged droplets, and the droplets gradually release ions during the evaporation of the solvent. Gaseous samples cannot form droplets and cannot be effectively ionized in this way. The MALDI method is usually used for solid samples. The sample is mixed with the matrix and then coated on the target plate. Laser irradiation causes the sample and the matrix to sublimate and ionize together. Gaseous samples cannot form a stable mixture on the target plate, so they cannot be ionized by MALDI. Under the premise of not destroying the original molecular composition, the ionization reaction chambers suitable for gaseous samples mainly include chemical ionization (CI) and atmospheric pressure photoionization (APPI), each of which has different characteristics and scope of application. The mechanisms of various ionization methods are different in terms of the mixing effect of sample gas flow and reagent ions. CI requires precise control of reagent gas flow and electric field strength, while APPI optimizes ionization efficiency by controlling light source intensity and auxiliary reagent flow. How to apply ionization methods suitable for gas phase samples to the front end of the orbital trap mass spectrometer is one of the key issues that need to be solved. In addition, the existing ionization reaction chamber cannot arbitrarily adjust the distance between the ion source and the mass spectrometer inlet (that is, adjust the reaction time between the gas to be tested and the reagent ions in the reaction chamber to achieve the purpose of optimizing the sensitivity of the analyte).

At present, there is a great lack of equipment that uses online nanoparticle thermal desorption and high-resolution mass spectrometry to carry out molecular-level measurement of the chemical components of nanoparticles. In order to make up for this shortcoming, the present invention has developed an online nanoparticle thermal desorption sampling system coupled with orbital trap mass spectrometry to achieve online molecular-level measurement of the chemical components of nanoparticles. This not only improves the speed and accuracy of data acquisition, but also provides strong technical support for pollution source identification, health risk assessment and climate change research. This system has important application prospects in environmental monitoring and pollution control.

Summary of the invention

In view of the above-mentioned deficiencies in existing online thermal desorption and chemical composition detection of nanoparticles, the present invention provides an online nano-scale particle thermal desorption sampling system coupled with an orbital trap mass spectrometer.

The online nano-particle thermal desorption sampling system coupled with an orbital trap mass spectrometer provided by the present invention has a structure as shown in FIG1 : comprising a filtering device 1, a particle size screening device 2, a suspension thermal desorption device 3 and a reaction chamber 4, an ion source, and a numerical control center 5 connected in series in sequence, wherein the ion source is connected to the reaction chamber 4; the numerical control center 5 is respectively connected to the particle size screening device 2, the suspension thermal desorption device 3, the reaction chamber 4 and the ion source through a signal transmission control line; wherein:

The filtering device 1 is filled with honeycomb activated carbon and is used to filter and remove gaseous pollutants in the atmosphere to ensure that only particles to be tested enter the subsequent device;

The particle size screening device 2 comprises a cutting disc with micron-sized holes, a gasket and a guide disc stacked in sequence, and nanoparticles with a particle size that meets the required research requirements are screened out from the particles to be tested obtained by the filtering device 1 by adjusting the distance between the guide disc and the cutting disc;

The suspended thermal desorption device 3 is used to heat the nanoparticles screened by the particle size screening device 2 to release the volatile components in the particles;

The ion source is used to provide reaction reagent ions to the reaction chamber 4;

The reaction chamber 4 is a place where the sample flow from the suspension thermal desorption device 3 and the reagent ions from the ion source are fully mixed and reacted, and the product ions after the reaction are passed to the subsequent mass spectrometry detection instrument for detailed analysis; this design can improve the sensitivity of the species to be detected, and at the same time, the combination with the high-resolution orbital trap mass spectrometer also improves the accuracy of the identification of the species to be detected;

The numerical control center 5 is used for coordinating and controlling the particle size screening device 2, the suspension thermal desorption device 3, the reaction chamber 4 and the ion source.

The main part of the whole system is made of metal materials (such as stainless steel, aluminum, etc.). The inner walls of all devices need to be electropolished to minimize the wall damage. The flange gaskets and O-rings used to connect the components are made of silicone or fluororubber, which have good heat resistance. In addition, silicone has good waterproof properties, and fluororubber has good oil resistance and is wear-resistant and corrosion-resistant.

Further:

The filter device 1 includes: a filter device inlet 1 201, a spring washer 202, a flange nut 203, a flange joint 204, a flange gasket 205, a honeycomb activated carbon 206, a filter device outlet 207, and a filter device inlet 208; see FIG. 2 .

The main part of the filter device 1 is 7 to 10 inches in length, of which the filtering area of the cylindrical cavity is 5 to 8 inches in length, 1.5 to 3 inches in diameter, and the wall thickness can be 0.1 inches. The area is filled with honeycomb activated carbon to adsorb the original gaseous species in the air. The honeycomb activated carbon has high porosity, large surface area, and strong adsorption. Its unique structure can better fix the material and extend the service life. The flange joint at the inlet end is convenient for disassembly and replacement of activated carbon. After special design, the inlet 1 201 of the filter device is a conical gradually expanding mouth, and the angle between the wall and the central axis is about 15°; the outlet 207 of the filter device is a conical gradually shrinking mouth, and the angle between the wall and the central axis is about 30°; the inlet 2 and the inlet 1 provided at the conical gradually shrinking mouth are not opened at the same time.

The particle size screening device 2 includes: a particle size screening device inlet 301, a flange gasket 302, a flange nut 303, a spring washer 304, a cutting disc 305, a gasket 306, a flange joint 307, a guide disc 308, and a particle size screening device outlet 309; see FIG3 .

The main body of the particle size screening device 2 is 2 to 3 inches in length, wherein the cylindrical impact chamber for placing the cutting disc, gasket and guide disc is 0.25 to 0.5 inches in length, 1 to 2 inches in diameter, and 0.1 inches in wall thickness. The length of the impact chamber is much shorter than that of other particle size screening instruments, so as to reduce the residence time and diffusion loss of particles in the particle size screening device. After special design, the inlet 301 of the particle size screening device is a conical gradually expanding opening, and the angle between the wall and the central axis is 15°; the outlet 309 of the particle size screening device is a conical gradually contracting opening, and the angle between the wall and the central axis is 30°. A circle is made on the cutting disk 305 with the midpoint as the center and a radius of 1 to 2 cm, and evenly distributed micropores are engraved within this range. The size of the micropores determines the particle size of the particles that pass through the cutting disk by impact. There are a total of 10 to 20 gaskets 306. Adjusting the number of gaskets between the cutting disk 305 and the guide disk 308 can affect the performance of the screening device. The flange joint is easy to disassemble, so it is convenient to adjust the position of the cutting disk and gasket in time according to specific experimental needs and experimental conditions.

The suspended thermal desorption device 3 includes: a suspended thermal desorption device inlet 1 401, a spring washer 402, a flange joint 403, a suspended thermal desorption device inlet 2 404, a flange nut 405, an insulation layer 406, a heating layer 407, a flange gasket 408, and a suspended thermal desorption device outlet 409; see FIG. 4 .

The main part of the suspended thermal desorption device 3 is 12 to 15 inches in length, of which the cylindrical thermal desorption column is 8 to 12 inches in length, 0.75 to 1 inch in diameter, and 0.1 inch in wall thickness. There are 7 to 10 holes with a diameter of 0.2 inches evenly arranged in the middle. The porous structure can greatly improve the heat conduction efficiency of the thermal desorption column; the two ends of the perforated thermal desorption column are arc surfaces to reduce the loss of particulate matter; flanges are provided on both sides of the main body, which can effectively reduce the processing difficulty of the heating hole column while ensuring the sealing. The heating layer 407 will be heated by an external heater to ensure the uniformity and stability of the heating; the insulation layer 406 uses a thicker insulation pipe to reduce the temperature loss; the inlet 2 and the inlet 1 provided at the front end of the thermal desorption are not opened at the same time.

The reaction chamber 4 includes: a flange nut 501, a flange joint 502, a flange sealing O-ring 503, a sliding cylinder 504, a reagent ion inlet 505, an ion source 506, a slide groove 507, a reaction chamber inlet 508, a top screw 509, a mass spectrometer injection port docking hole 510, a mass spectrometer adapter front seat 511, a rotating shaft 512, a positioning pin 513, a reaction chamber outlet 514, a mass spectrometer adapter rear seat 515, and an adapter sealing O-ring 516; see FIG5 .

The main body of the reaction chamber 4 is 12 to 16 inches in length, wherein the cylindrical reaction chamber is 10 to 14 inches in length, 0.75 to 1 inch in diameter, and the wall thickness can be 0.1 inch; a slide groove 507 with a length of 1 to 2 inches and a width of 0.1 inch is opened on the left side of the reaction chamber, and a sliding cylinder 504 with a thickness of 0.25 to 0.5 inches is sleeved on the outside of the corresponding part, and both ends are sealed with double-layer O-rings to ensure the airtightness of the slide groove; by moving the sliding cylinder 504 left and right, the time for the reaction gas to reach the mass spectrometer injection port can be adjusted to ensure that the gas to be tested entering the mass spectrometer is evenly mixed; an elliptical mass spectrometer injection port docking hole 51 that fits the mass spectrometer injection port is opened on the right side of the reaction chamber 0, use the mass spectrometer adapter front seat 511 and the mass spectrometer adapter rear seat 515 in conjunction with the adapter sealing O-ring 516 to ensure the airtightness of the mass spectrometer injection port docking part; a reagent ion inlet 505 is opened in the middle of the sliding cylinder 504, and the inlet is a conical reducing hole with an outer diameter of 0.25 to 0.375 inches and an inner diameter of 0.0625 to 0.125 inches, which can allow the reagent ions generated in the ion source 506 to quickly mix with the sample flow after entering the reaction chamber 4, and can reach a laminar flow state in a very short time; the reacted gas will enter the mass spectrometer through the mass spectrometer injection port docking hole 510 for subsequent component analysis, and the remaining gas will be discharged through the reaction chamber outlet 514.

The numerical control center 5 includes: a centralized control and display system of three mass flow controllers and a heater. The three flow controllers respectively control the flow rate of the particle size screening device (2), the flow rate of the reagent ion flow in the reaction chamber (4), and the flow rate of the discharged excess air flow; the heater controls the temperature of the thermal desorption column of the suspended thermal desorption device (3), and the heater can achieve gradient heating or maintain a constant temperature.

The control process of the online nanoparticle thermal desorption sampling system is as follows:

Step 1: Connect a flow controller to the rear end of the reaction chamber outlet and set the pumping gas flow rate to 5-20 L/min;

Step 2: Use a mass flow controller to control the introduction of 0.001-1 L/min of reagent ion vapor, which is mixed and diluted with 1-15 L/min of zero air or nitrogen and then introduced into the ion source. At this time, the flow rate of the sample to be measured = the flow rate of the pumping gas - the flow rate of the dilution gas - the flow rate of the reagent ions; the introduced ion vapor is a 57% HNO ₃ solution or a 99.5% CH ₃ I solution;

Step 3: The sample flow to be tested passes through the filtering device and the particle size screening device and enters the suspended thermal desorption device. The thermal desorption device is heated by an external heater, and the temperature is controlled at 20-300°C, and the gradient temperature rise program is 1-30°C/min; or a fixed temperature gradient is used, such as 50, 100, 150, 200, 300°C, each maintained for 2-10 minutes;

Step 4: Use a vacuum ultraviolet lamp (applied voltage 1500-1800V) or X-ray to photoionize HNO ₃ molecules or CH ₃ I molecules to produce reagent ions NO ₃ ^- or I ^- , which then react with the sample flow to be tested;

Step 5: Adjust the distance between the reagent ion inlet and the mass spectrometer injection port docking hole to optimize the sensitivity (ng/m ³ ) and the total ion concentration signal value to at least 1E6;

Step 6: Except for the reaction gas flow entering the mass spectrometer, the remaining gas flows out as a bypass gas;

Step 7: Obtain high-resolution chemical composition information of nano-scale particles by analyzing mass spectrometry results;

The beneficial effects of the present invention mainly include:

(1) High-efficiency filtration: The honeycomb activated carbon can effectively filter gaseous pollutants in the atmosphere and prevent gaseous substances from interfering with the subsequent thermal desorption of particulate matter;

(2) Precision screening: By adjusting the distance between the cutting disk with micron-sized holes and the guide disk, particles with a particle size that meets the research requirements (e.g., ≤50 nanometers) can be accurately screened out;

(3) High thermal desorption efficiency: The suspended thermal desorption device uses porous metal materials to improve the heat conduction efficiency, allowing the volatile components in the particles to be released quickly. In addition, the particles are thermally desorbed during the suspension process, with a large heating area and low molecular thermal fragmentation.

(4) High sensitivity and selective measurement: The reaction chamber is ingeniously designed. The sample gas flow and the reaction time of the reagent ions are adjusted through the slide and the sliding cylinder to ensure that the molecules to be tested fully react with the reagent ions before entering the mass spectrometer for analysis. In addition, the ion source can switch between different reagent ions to achieve selective measurement of characteristic compounds.

(5) Durable and convenient: The main body of the system is made of metal material, the inner wall is electropolished to reduce wall damage, and the accessories are easy to disassemble, which reduces the production and maintenance costs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram showing the working principle of an online nanoparticle thermal desorption injection system coupled to an orbital trap mass spectrometer.

FIG. 2 is a schematic diagram of the structure of the filtering device.

FIG. 3 is a schematic diagram of the structure of a particle size screening device.

FIG4 is a schematic diagram of the structure of a suspended thermal desorption device.

FIG5 is a schematic diagram of the reaction chamber structure.

Figure 6 shows the high-resolution chemical composition information of nano-sized particles.

Numbers in the figure: 1-filter device; 2-particle size screening device; 3-suspension thermal desorption device; 4-reaction chamber; 5-CNC center; 201-filter device inlet one; 202-spring washer; 203-flange nut; 204-flange joint; 205-flange gasket; 206-honeycomb activated carbon; 207-filter device outlet; 208-filter device inlet two; 301-particle size screening device inlet; 302-flange gasket; 303-flange nut; 304-spring washer; 305-cutting disc; 306-gasket; 307-flange joint; 308-guide disc; 309-particle size screening device outlet; 401-suspension thermal desorption device inlet one; 402-spring washer; 403-flange joint; 404-inlet 2 of suspension thermal desorption device; 405-flange nut; 406-insulation layer; 407-heating layer; 408-flange gasket; 409-outlet of suspension thermal desorption device; 501-flange nut; 502-flange joint; 503-flange sealing O-ring; 504-sliding cylinder; 505-reagent ion inlet; 506-ion source; 507-slide; 508-reaction chamber inlet; 509-top screw; 510-mass spectrometer injection port docking hole: 511-mass spectrometer adapter front seat; 512-rotating shaft; 513-locating pin; 514-reaction chamber outlet; 515-mass spectrometer adapter rear seat; 516-adapter sealing O-ring.

DETAILED DESCRIPTION

An embodiment of the present invention discloses an online nano-particle thermal desorption sampling system coupled to an orbital trap mass spectrometer, as shown in FIG1 , comprising a filtering device 1, a particle size screening device 2, a suspended thermal desorption device 3, a reaction chamber 4, and a numerical control center 5 connected in sequence.

The filter device 1 is used to filter gaseous pollutants in the ambient air sample, and includes a filter device inlet 1 201, a spring washer 202, a flange nut 203, a flange joint 204, a flange gasket 205, a honeycomb activated carbon 206, a filter device outlet 207, and a filter device inlet 208. The sample flow to be tested can be an ambient air sample or a standard sample generated by an aerosol generator in a laboratory. The sample flow to be tested enters the filter device from the filter device inlet 1 201, passes through the filled honeycomb activated carbon 206, and is introduced into the particle size screening device 2 from the filter device outlet 207. The honeycomb activated carbon has high porosity, large surface area, and strong adsorption. At the same time, due to its low resistance, it can allow the airflow to pass quickly and reduce the loss of particulate matter.

The particle size screening device 2 is used to screen out nanoparticles that meet the particle size requirements, including a particle size screening device inlet 301, a flange gasket 302, a flange nut 303, a spring washer 304, a cutting disc 305, a gasket 306, a flange joint 307, a guide disc 308, and a particle size screening device outlet 309. After the sample flow to be tested enters the screening device, it will selectively pass through the cutting disc, and only particles that meet the particle size range conditions can flow out from the particle size screening device outlet 309 with the sample flow and enter the suspended thermal desorption device 3. The size of the micropores on the cutting disc 305, the spacing between the cutting disc and the guide disc 308, the sampling flow rate, etc. will affect the performance of the screener (the cutting point, sharpness and transmittance of the particle size), and can be adjusted according to the purpose of the experiment.

The suspended thermal desorption device 3 is used to heat the particles to release the volatile substances therein, especially the low-volatile components, and includes a suspended thermal desorption device inlet 1 401, a spring washer 402, a flange joint 403, a suspended thermal desorption device inlet 2 404, a flange nut 405, an insulation layer 406, a heating layer 407, a flange gasket 408, and a suspended thermal desorption device outlet 409. The particles entering the device are rapidly vaporized at high temperatures, and the porous structure increases the efficiency of thermal desorption. The uniformly wrapped heating layer 407 and the thermal insulation layer 406 can ensure that the temperature of the thermal desorption is in a relatively stable state, and the external heater can adjust the temperature within the range of 20 to 300°C.

The reaction chamber 4 provides space for the full reaction of the sample flow and the reagent ions, and includes a flange nut 501, a flange joint 502, a flange sealing O-ring 503, a sliding cylinder 504, a reagent ion inlet 505, an ion source 506, a slide 507, a reaction chamber inlet 508, a top screw 509, a mass spectrometer injection port docking hole 510, a mass spectrometer adapter front seat 511, a rotating shaft 512, a positioning pin 513, a reaction chamber outlet 514, a mass spectrometer adapter rear seat 515, and an adapter sealing O-ring 516. The sample flow flowing out of the suspension thermal desorption device outlet 409 enters the reaction chamber 4 from the reaction chamber inlet 508; the ion source 506 can be any type of ion source, and the generated reagent ions enter the reaction chamber 4 from the reagent ion inlet 505, and react quickly with the sample flow. The reacted gas will enter the mass spectrometer through the mass spectrometer injection port docking hole 510 for subsequent component analysis, and the remaining gas will be discharged through the reaction chamber outlet 514. By controlling the ratio of sample flow and reagent ion flow, reaction time, type of ion source (such as X-ray, vacuum ultraviolet VUV lamp, etc.), type of reagent ion (such as nitrate, iodine ion, etc.), the sensitivity of the sample to be tested entering the mass spectrometer can meet the requirements, thereby obtaining chemical composition information of nano-scale particles with high time resolution.

The numerical control center 5 realizes real-time flow and temperature control and recording. The three flow controllers respectively control the sampling flow rate of the particle size screening device 2, the excess air flow rate discharged from the reaction chamber 4, and the flow rate of the reagent ion flow; the heater controls the temperature of the thermal desorption column of the suspended thermal desorption device 3, and the heater can realize gradient heating or maintain a constant temperature.

In addition to the conventional use method, the following can also be achieved: 1) The second filter inlet 208 can be opened or closed, and this inlet is not opened at the same time as the first filter inlet 201 and the second suspension thermal desorption device inlet 404. When the second filter inlet 208 is opened, the component information of the mixture containing the original gaseous pollutants and the screened nano-sized particles in the sample flow is finally measured; 2) The second suspension thermal desorption device inlet 404 can be opened or closed, and this inlet is not opened at the same time as the first filter inlet 201 and the second filter inlet 208. When the second suspension thermal desorption device inlet 404 is opened, the component information of the unfiltered and unscreened sample flow to be measured is finally measured.

Take the above conventional injection system workflow as an example, where the cutting disk screens atmospheric particles below 50 nanometers, the ion source uses a vacuum ultraviolet VUV lamp, and the reagent ions use iodine ions:

Step 1: Connect a flow controller to the rear end of the reaction chamber outlet and set the flow rate to 6 L/min.

Step 2: Use a mass flow controller to control the flow of 1 L/min of CH ₃ I vapor, which is mixed and diluted with 2 L/min of nitrogen and then introduced into the ion source. At this time, the sample flow to be measured is 3 L/min.

Step 3: The sample flow to be tested passes through the filtering device and the particle size screening device and enters the suspended thermal desorption device. The thermal desorption device is heated by an external heater. The setting of the temperature gradient needs to ensure that the species to be tested can be thermally desorbed and will not decompose. Therefore, the temperature is controlled at 25-200°C, and the heating program is as follows: 0-5min maintains the temperature at 25.0°C; 6-7min heats up to 60°C at 17.5°C/min, and maintains at 60°C for 8-15min; 16-17min heats up to 100°C at 20°C/min, and maintains at 100°C for 18-25min; 26-27min heats up to 140°C at 20°C/min, and maintains at 140°C for 28-35min; 36-37min heats up to 180°C at 20°C/min, and maintains at 180°C for 38-45min; 46-47min heats up to 200°C at 10°C/min, and maintains at 200°C for 48-60min.

Step 4: Synchronously with step 3, apply a voltage of 1700 V to the vacuum ultraviolet lamp to allow it to photoionize CH ₃ I molecules to generate reagent ions I ⁻ to react with the sample flow to be tested.

Step 5: Adjust the distance between the reagent ion inlet and the mass spectrometer injection port docking hole to 10.6 cm, optimize the sensitivity, and make the total ion concentration signal value between 1E6 and 2E6.

Step 6: In addition to the reaction gas flow entering the orbitrap mass spectrometer, the excess gas flows out as the bypass gas.

Step 7: Analyze the orbital trap mass spectrometry measurement results. The high-resolution chemical composition information of the nano-scale particles is shown in Figure 6 ((b) is the enlarged view of the Y-axis 0-200 segment in (a)); the abscissa is the mass-to-charge ratio, and the ordinate is the signal value of the mass spectrum.

The present invention is not limited by the above embodiments. The above embodiments and the description in the specification are only the basic principles, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the corresponding changes and improvements of the present invention shall fall within the scope of protection required.

Claims (7)

1. An online nano-scale particulate matter thermal desorption sample feeding system combined with an orbitrap mass spectrum is characterized by comprising a filtering device, a particle size screening device, a suspension thermal desorption device and a reaction chamber which are sequentially connected in series, and an ion source is connected with the reaction chamber; the numerical control center is respectively connected with the particle size screening device, the suspension heat desorption device, the reaction chamber and the ion source through signal transmission control lines; wherein:

the filtering device is filled with honeycomb-type activated carbon and is used for filtering and removing gaseous pollutants in the atmosphere, so that only particles to be detected can enter the subsequent device;

the particle size screening device comprises a cutting disc, a gasket and a flow guide disc which are sequentially stacked and provided with micro-scale small holes, and nano-particles meeting the particle size required by research are screened out from the particles to be detected obtained by the filtering device by adjusting the distance between the flow guide disc and the cutting disc;

the suspension thermal desorption device is used for heating the nano-particles screened by the particle size screening device so as to release volatile components in the particles;

the ion source is used for providing reactant ions to the reaction chamber;

The reaction chamber is a place where sample flow from the suspension thermal desorption device and reagent ions from the ion source are fully mixed and reacted, and the reacted product ions are introduced into a subsequent mass spectrum detection instrument for detailed analysis; the design can improve the sensitivity of the species to be detected, and simultaneously, the accuracy of the species to be detected identification is improved by being combined with a high-resolution orbitrap mass spectrum;

The numerical control center is used for cooperatively controlling the particle size screening device, the suspension heat desorption device, the reaction chamber and the ion source.

2. The on-line nano-scale particulate matter thermal desorption sample feeding system for use with an orbitrap mass spectrometer of claim 1, wherein the main body of said filter device is a cylindrical cavity, 5-8 inches long and 1.5-3 inches in diameter, and as a filtering area, honeycomb-type activated carbon is arranged in the filtering area; the first inlet of the filtering device is a conical divergent opening, and the outlet is a conical convergent opening; a second inlet is also provided at the conical mouth of the conical shape, which is not simultaneously open with the first inlet.

3. The on-line nano-scale particulate matter thermal desorption sample loading system for use with an orbitrap mass spectrometer of claim 1, wherein said particle size screen comprises a cylindrical impingement chamber of 0.25 to 0.5 inches in length and 1 to 2 inches in diameter in which are placed a cutting disk, a spacer and a deflector; the inlet of the particle size screening device is a conical divergent opening, and the outlet of the particle size screening device is a conical convergent opening; the cutting disc is circular, micropores are uniformly distributed in the central part of the cutting disc, and the size of the micropores determines the particle size of particles passing through the cutting disc through impact; the gasket has many, adjusts this gasket quantity, can influence screening plant's performance.

4. The on-line nano-scale particulate matter thermal desorption sample feeding system for use with an orbitrap mass spectrometer of claim 1, wherein the main body part of the suspension thermal desorption device comprises a thermal desorption column with the length of 8-12 inches and the diameter of 0.7-1 inch, 7-10 holes with the diameter of 0.2 inch are uniformly distributed in the middle, and the porous structure can greatly improve the heat conduction efficiency of the thermal desorption column; the two ends of the perforated thermal desorption column are cambered surfaces so as to reduce the loss of particulate matters; flanges are arranged on two sides of the main body, so that the processing difficulty of the heating hole column is reduced under the condition of ensuring the tightness; the heating layer and the heat preservation layer are arranged on the outer side of the heating layer, and the heating layer is heated by an external heater, so that the heating uniformity and the heating stability are ensured; the heat insulating layer is made of heat insulating pipe to reduce temperature loss.

5. The on-line nanoscale particulate matter thermal desorption sample loading system for use with an orbitrap mass spectrometer of claim 1, wherein said reaction chamber is a cylindrical reaction chamber having a length of 10 to 14 inches and a diameter of 0.75 to 1 inch; a sliding groove with the length of 1-2 inches and the width of 0.1 inch is arranged on the left side of the reaction cavity, a sliding cylinder with the thickness of 0.25-0.5 inch is sleeved outside the corresponding part, and two ends of the sliding cylinder are sealed by double-layer O-shaped rings, so that the air tightness of the sliding groove part is ensured; by moving the sliding cylinder left and right, the time for the reaction gas to reach the mass spectrum sample inlet can be adjusted, and the mixture uniformity of the gas to be detected entering the mass spectrum is ensured; the reagent ion inlet is formed in the middle of the sliding cylinder, and is a conical reducing hole, so that reagent ions generated in the ion source can be quickly mixed with sample flow after entering the reaction chamber, and a laminar flow state can be achieved in a very short time; an elliptic mass spectrum sample inlet butt joint hole which is matched with the orbitrap mass spectrum sample inlet is formed on the right side of the reaction cavity, and the gas tightness of the butt joint part of the mass spectrum sample inlet is ensured by using a mass spectrum adapter front seat and a mass spectrum adapter rear seat to be matched with an adapter to seal an O-shaped ring.

6. The on-line nanoscale particulate matter thermal desorption sampling system for use with an orbitrap mass spectrometer of claim 1, wherein the numerically controlled center can control flow rate and temperature parameters comprising: the passing flow rate of the particle size screening device, the flow rate of the reagent ion flow of the reaction chamber and the flow rate of the discharged superfluous gas flow; temperature of the thermal desorption column.

7. The on-line nanoscale particulate matter thermal desorption sample loading system for use with an orbitrap mass spectrometer of any one of claims 1-6, wherein the control flow of the system is:

(1) The rear end of the outlet of the reaction chamber is connected with a flow controller, and the pumping flow rate is set to be 5-20L/min;

(2) Controlling the flow rate of the sample to be measured to be the flow rate of the air exhaust flow rate, the flow rate of the dilution gas and the flow rate of the reagent ions by using a mass flow controller to control the flow rate of the reagent ions to be 0.001-1L/min, mixing the reagent ions with 1-15L/min of zero air or nitrogen for dilution, and then introducing the mixture into an ion source; the introduced ion vapor is a solution with the concentration of 57 percent HNO ₃ or a solution with the concentration of 99.5 percent CH ₃ I;

(3) The sample flow to be measured enters a suspension thermal desorption device through a filtering device and a particle size screening device, an external heater is used for heating the thermal desorption device, the temperature is controlled to be 20-300 ℃, and the gradient heating program is 1-30 ℃/min; or adopting a fixed temperature gradient, namely, maintaining at 50, 100, 150, 200 and 300 ℃ for 2-10 min respectively;

(4) Applying 1500-1800V voltage by using a vacuum ultraviolet VUV lamp or using X-ray to make the vacuum ultraviolet VUV lamp photoionization HNO ₃ molecules or CH ₃ I molecules produce reagent ions NO ₃ ^- or I ^- so as to react with a sample flow to be detected;

(5) Adjusting the distance between the reagent ion inlet and the butt joint hole of the mass spectrum sample inlet, and optimizing the sensitivity and the total ion concentration signal value;

(6) The rest of the gas flows out as bypass gas except the reaction gas flow entering the mass spectrum;

(7) And (3) obtaining the chemical component information of the high-resolution nano-scale particles by analyzing the mass spectrum measurement result.