A device and method for online rapid measurement of atmospheric HNO3

Abstract

The present invention relates to a device and method for online rapid measurement of atmospheric HNO3, belonging to the field of ion mobility spectrometry analysis and sample pretreatment. The device comprises: a gas sampling filter, a sampling ring, a semiconductor refrigeration plate, a sampling pump, and an ion mobility spectrometry system. By combining time-dynamic separation, selective ionization, and the separation capability of IMS, the interference of atmospheric background is overcome, enabling accurate IMS identification of atmospheric HNO3. Time-dynamic separation and ion mobility spectrometry are utilized to achieve highly sensitive quantitative measurement of atmospheric HNO3 concentration levels. Ultimately, a new method for measuring atmospheric HNO3 concentration levels is developed with a measurement cycle of less than 5 minutes and a detection limit of up to the ppt level. This method and equipment are provided for in-depth understanding of atmospheric chemical reactions and research on countermeasures to improve my country's air quality.

Description

Technical Field

[0001] The invention relates to a device and method for online rapid measurement of atmospheric HNO3, belonging to the field of ion mobility spectrometry analysis and sample pretreatment. Background Art

[0002] HNO3 in the atmospheric environment is a crucial intermediate product in atmospheric chemical reactions. It not only affects the generation of atmospheric free radicals and O3, but also has an important impact on the nucleation reaction of newly formed atmospheric particles. The generation of HNO3 by NO2 and OH· free radicals is one of the most important reactions to terminate atmospheric OH· free radicals, and has a significant impact on atmospheric oxidizability and the transformation of pollutants. In the transformation of HNO3, HNO3 can react with NH3, the most abundant alkaline gas in the atmosphere, to generate NH4NO3, which can provide condensation nuclei for the generation of atmospheric particulate matter, increase the nucleation rate of new particles, and worsen air quality. Nitrate has surpassed sulfate to become the main source of PM2.5 in the Beijing-Tianjin-Hebei region. 2.5 HNO3 is the most important secondary inorganic component in nitrogen. Through wet and dry deposition, HNO3 and its resulting salts enter aquatic and terrestrial ecosystems, altering their nutrient structure and seriously threatening the balance of my country's ecological environment. Therefore, real-time and accurate measurement of HNO3 concentration levels in the atmosphere not only contributes to a deeper understanding of atmospheric chemical reactions but also has important implications for nucleation reactions and the nitrogen cycle.

[0003] Currently, methods such as ion chromatography, mass spectrometry, infrared spectroscopy, and chemiluminescence have all been reported for monitoring HNO₃ in the atmospheric environment, with ion chromatography and mass spectrometry being the most commonly used. Ion chromatography is often used in conjunction with a diffusion tube, where an alkaline adsorbent (such as Na₂CO₃ or K₂CO₃) coated inside the tube absorbs gaseous HNO₃. After extraction with a solution, the HNO₃ is detected, achieving a detection limit of ppt. Ion chromatography requires high levels of manpower and automation, and its response time is relatively slow, making it difficult to meet the demand for high-precision atmospheric HNO₃ measurements. Mass spectrometry is another common method for measuring HNO₃ in the atmosphere. It typically uses chemical ionization to ionize the HNO₃ in atmospheric samples, followed by separation and detection based on the difference in proton number / charge number. However, because mass spectrometry requires vacuum operation, it is bulky and heavy, and has high construction and operating costs. This makes it difficult to meet the requirements for mobile measurement and long-term, large-scale monitoring, limiting this technology to laboratory research applications.

[0004] Based on ion mobility spectrometry technology, this invention breaks through the difficulties of accurate identification and high-sensitivity detection of low-concentration HNO3 in complex atmospheric backgrounds, and develops a new method for rapid, accurate and reliable monitoring of HNO3 in the atmospheric environment, which can provide new technical means for my country's environmental supervision and research on countermeasures to improve air quality. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides, on the one hand, a device for online rapid measurement of atmospheric HNO3, which includes: a gas sampling filter, a sampling ring, a semiconductor refrigeration plate, a sampling pump, and an ion mobility spectrometry system; the inlet of the gas sampling filter is connected to the atmospheric environment, and the air outlet of the gas sampling filter is connected to the B port of a first three-way valve; the C port of the first three-way valve is connected to the inlet of the ion mobility spectrometry system via a first heating pipeline, the A port of the first three-way valve is connected to the air inlet of the sampling ring, a semiconductor refrigeration plate is provided in the sampling ring, and the air outlet of the sampling ring is connected to the A port of a second three-way valve; the B port of the second three-way valve is connected to the air inlet of the sampling pump, and the C port of the second three-way valve is connected to the C port of a third three-way valve via a second heating pipeline; the B port of the third three-way valve is connected to the inlet of the ion mobility spectrometry system, and the A port of the third three-way valve is connected to clean air.

[0006] Furthermore, the device also includes a cooling fan for assisting the semiconductor refrigeration plate in the sampling ring in dissipating heat.

[0007] Furthermore, the first three-way valve, the second three-way valve, and the third three-way valve are all gas-specific three-way valves.

[0008] Furthermore, the power of the semiconductor refrigeration chip is 100-200w, which can reduce the temperature in the sampling ring to 0-5°C within 1-5s.

[0009] Furthermore, the sampling loop is a polyfluoroethylene tube with a length of 0.5-2m.

[0010] Furthermore, the second heating pipeline has a length of 1-5 m and can heat the carrier gas to a temperature of 60-100° C.

[0011] Another aspect of the present invention provides a method for online rapid measurement of atmospheric HNO3 by the device, the method comprising: collecting HNO3 in the atmospheric environment by time-resolved enrichment, then entering the HNO3 into an ion mobility spectrometry system by backflushing and sweeping, and detecting the HNO3 in the atmospheric environment based on the time of ion migration.

[0012] Furthermore, the ionization source of the ion mobility spectrometry system is 63 Ni ionization source, working mode is negative ion mode, drift gas flow rate is 200-600 ml / min, injection flow rate is 50-200 ml / min.

[0013] Furthermore, the method comprises the following specific steps:

[0014] 1) During sampling, the first three-way valve, the second three-way valve, the third three-way valve, the semiconductor refrigeration plate, and the sampling pump are powered on and turned on. When the first three-way valve, the second three-way valve, and the third three-way valve are powered on, the A and B gas ports are connected; the sample in the atmospheric environment is discharged by the sampling pump through the gas sampling filter, the A and B ports of the first three-way valve, the sampling loop, and the A and B ports of the second three-way valve. HNO3 in the atmosphere is collected in the sampling loop. At the same time, clean air enters the air inlet of the ion mobility spectrometry system through the A and B ports of the third three-way valve to clean the gas path;

[0015] 2) During sampling, the first three-way valve, the second three-way valve, the third three-way valve, the semiconductor refrigeration plate, and the sampling pump are powered off, and the A and C ports of the first three-way valve, the second three-way valve, and the third three-way valve are connected. Clean air passes through the A and C ports of the third three-way valve, is heated by the second heating pipeline, and then passes through the A and C ports of the second three-way valve to purge the sample retained in the sampling loop and enter the ion mobility spectrometry system through the A and C ports of the first three-way valve for analysis.

[0016] Furthermore, HNO3 is qualitatively identified based on its peak position in the ion mobility spectrum, and its content level is determined based on the intensity of the peak height.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention measures atmospheric HNO3 for the first time based on ion mobility spectrometry technology, with a measurement period of less than 5 minutes and a detection limit of up to ppt level. It has high sensitivity, fast detection speed, high cost performance and simple operation.

[0019] The present invention can quickly detect HNO3 in the atmospheric environment in real time online; the instrument has low operating cost, light weight, small size, and is suitable for on-site detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a schematic diagram of the structure of a device for online rapid measurement of atmospheric HNO3 according to the present invention.

[0021] Among them: 1. Gas sampling filter; 2. First three-way valve; 3. Sampling loop; 4. Semiconductor refrigeration plate; 5. Cooling fan; 6. Second three-way valve; 7. Third three-way valve; 8. Second heating pipeline; 9. Sampling pump; 10. Ion mobility spectrometry system. DETAILED DESCRIPTION

[0022] The following examples illustrate the use of the present invention but do not limit the scope of application described.

[0023] A device for online rapid measurement of atmospheric HNO3 comprises: a gas sampling filter 1, a sampling ring 3, a semiconductor cooling plate 4, a sampling pump 9, and an ion mobility spectrometer system 10; the inlet of the gas sampling filter 1 is connected to the atmospheric environment, and the air outlet of the gas sampling filter 1 is connected to the B port of a first three-way valve 2; the C port of the first three-way valve 2 is connected to the inlet of the ion mobility spectrometer system 10 via a first heating pipeline, the A port of the first three-way valve 2 is connected to the air inlet of the sampling ring 3, the semiconductor cooling plate 4 is arranged in the sampling ring 3, and the air outlet of the sampling ring 3 is connected to the A port of a second three-way valve 6; a cooling fan 5 is arranged near the sampling ring 3 for assisting the semiconductor cooling plate 4 in the sampling ring 3 in heat dissipation; the B port of the second three-way valve 6 is connected to the air inlet of the sampling pump 9, and the C port of the second three-way valve 6 is connected to the C port of a third three-way valve 7 via a second heating pipeline 8; the B port of the third three-way valve 7 is connected to the inlet of the ion mobility spectrometer system 10, and the A port of the third three-way valve 7 is connected to clean air.

[0024] When the first three-way valve 2, the second three-way valve 6, and the third three-way valve 7 are energized, the A and B gas ports are connected; when the power is off, the A and C ports are connected.

[0025] Example 1

[0026] When a device for online rapid measurement of atmospheric HNO3 is working, the ionization source of the ion mobility spectrometry system adopts 63 Ni ionization source, working mode is negative ion mode, drift gas flow rate is 400ml / min, tail gas flow rate is 600ml / min, injection flow rate is 200ml / min, clean air flow rate through the third three-way valve is 250ml / min, sampling time is 2min, injection time is 2min, and measurement time is 4min.

[0027] The specific steps are:

[0028] 1) When sampling, the first three-way valve 2, the second three-way valve 6, the third three-way valve 7, the semiconductor refrigeration plate 4, and the sampling pump 9 are powered on and turned on; the sample in the atmospheric environment is discharged by the sampling pump through the gas sampling filter 1, the A and B ports of the first three-way valve (2), the sampling ring 3, and the A and B ports of the second three-way valve 6, and the HNO3 in the atmosphere is collected in the sampling ring 3. At the same time, clean air enters the air inlet of the ion mobility spectrometry system 10 through the A and B ports of the third three-way valve 7 to clean the gas path and ensure the long-term stable operation of the ion mobility spectrometry system 10;

[0029] 2) When injecting a sample, the first three-way valve 2, the second three-way valve 6, the third three-way valve 7, the semiconductor refrigeration plate 4, and the sampling pump 9 are powered off. Clean air passes through the third three-way valve 7A and C ports, is heated by the second heating pipeline 8, and then passes through the second three-way valve 6A and C ports to purge the sample retained in the sampling loop 3. The air then enters the ion mobility spectrometry system 10 through the first three-way valve 2A and C ports for analysis.

[0030] The ion mobility spectrometry system 10 measures the concentration of HNO 3 in the atmospheric environment based on the peak position and peak intensity of HNO 3 in the spectrum.

[0031] Example 2

[0032] The ion mobility spectrometry system 10 uses the relevant parameters in Example 1. When the HNO3 concentration in the detection environment is high, the sampling time is shortened to 1 minute, or even shorter, so that less HNO3 remains in the sampling loop 3, reducing the impact of the residual response of the device, and reducing the injection time, making the single analysis time shorter.

Claims

1. A method for rapid online measurement of atmospheric HNO3, characterized by: The method comprises the following steps: collecting HNO3 in the atmospheric environment by time-resolved enrichment, and then introducing the HNO3 into an ion mobility spectrometer system (10) by back-flushing and sweeping, so that the HNO3 in the atmospheric environment can be detected according to the time of ion migration; The device used in the method includes: a gas sampling filter (1), a sampling ring (3), a semiconductor refrigeration plate (4), a sampling pump (9), and an ion mobility spectrometry system (10); The inlet of the gas sampling filter (1) is connected to the atmospheric environment, and the outlet of the gas sampling filter (1) is connected to the B port of the first three-way valve (2); the C port of the first three-way valve (2) is connected to the inlet of the ion mobility spectrometer system (10) via the first heating pipeline, the A port of the first three-way valve (2) is connected to the inlet of the sampling ring (3), a semiconductor cooling plate (4) is provided in the sampling ring (3), and the outlet of the sampling ring (3) is connected to the A port of the second three-way valve (6); the B port of the second three-way valve (6) is connected to the inlet of the sampling pump (9), and the C port of the second three-way valve (6) is connected to the C port of the third three-way valve (7) via the second heating pipeline (8); the B port of the third three-way valve (7) is connected to the inlet of the ion mobility spectrometer system (10), and the A port of the third three-way valve (7) is connected to clean air.

2. The method according to claim 1, wherein: The device further comprises a cooling fan (5) for assisting the semiconductor cooling plate (4) in the sampling ring in cooling.

3. The method according to claim 1, wherein: The first three-way valve (2), the second three-way valve (6), and the third three-way valve (7) are all three-way valves dedicated to gas.

4. The method according to claim 1, wherein: The power of the semiconductor refrigeration chip (4) is 100-200W, and the temperature in the sampling ring (3) can be reduced to 0-5°C within 1-5 seconds.

5. The method according to claim 1, wherein: The sampling ring (3) is a polytetrafluoroethylene tube with a length of 0.5-2m.

6. The method according to claim 1, wherein: The second heating pipeline (8) has a length of 1-5 m and can heat the carrier gas to a temperature of 60-100°C.

7. The method according to claim 1, wherein: The ionization source of the ion mobility spectrometry system (10) is 63 Ni ionization source, working mode is negative ion mode, drift gas flow rate is 200-600 ml / min, injection flow rate is 50-200 ml / min.

8. The method according to claim 1, wherein: The specific steps of the method are: 1) During sampling, the first three-way valve (2), the second three-way valve (6), the third three-way valve (7), the semiconductor refrigeration plate (4), and the sampling pump (9) are energized and opened. When the first three-way valve (2), the second three-way valve (6), and the third three-way valve (7) are energized, the A and B gas ports are connected; the sample in the atmospheric environment is discharged by the sampling pump (9) through the gas sampling filter (1), the A and B ports of the first three-way valve (2), the sampling ring (3), and the A and B ports of the second three-way valve (6). HNO3 in the atmosphere is collected in the sampling ring (3). At the same time, clean air enters the air inlet of the ion mobility spectrometer system (10) through the A and B ports of the third three-way valve (7) to clean the gas path; 2) When injecting the sample, the first three-way valve (2), the second three-way valve (6), the third three-way valve (7), the semiconductor cooling plate (4), and the sampling pump (9) are powered off, and the A and C ports of the first three-way valve (2), the second three-way valve (6), and the third three-way valve (7) are connected. Clean air passes through the A and C ports of the third three-way valve (7), is heated by the second heating pipeline (8), and then passes through the A and C ports of the second three-way valve (6). The sample retained in the sampling loop (3) is purged and processed, and enters the ion mobility spectrometry system (10) through the A and C ports of the first three-way valve (2) for analysis.

9. The method according to claim 1, wherein: HNO3 can be qualitatively identified based on its peak position in the ion mobility spectrum, and its content level can be determined based on the intensity of the peak height.

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