An ammonia detection device and method based on corona discharge ion mobility spectrometry technology

Abstract

The application discloses an ammonia detection device and method based on a corona discharge ion mobility spectrometry technology. The application is based on a corona discharge ionization technology and an ion mobility spectrometry technology, and provides a corona discharge ion mobility spectrometer (CD-IMS). The CD-IMS adopts a corona discharge ionization source, in a positive ion mode, introduces a water vapor alone, generates reaction reagent ions (H2O)nH + , the reaction ions can react with ammonia to generate product ions (H2O)nNH4 + , and high-sensitivity qualitative and quantitative detection of the ammonia is realized. The method has an extremely fast analysis speed, a response time is less than 1s, can realize continuous monitoring of the ammonia, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to an ammonia detection device and method based on corona discharge ion mobility spectrometry, which can achieve highly selective detection of ammonia in complex backgrounds and belongs to the field of environmental monitoring instruments. Background Technology

[0002] With the acceleration of industrialization and the rapid development of agriculture, the emission of ammonia, an important chemical raw material, is increasing year by year. Ammonia is a colorless, toxic, and strongly pungent odorous harmful gas that is the primary emission limit under the national standard for odor pollutant emissions (GB14554-93). It is widely present in industrial production, agriculture, and household environments. Long-term exposure to high concentrations of ammonia can irritate the respiratory tract, eyes, and skin, leading to discomfort such as coughing, difficulty breathing, and eye pain, and even damaging lung function. In industrial production processes, many industries use or emit substances containing large amounts of amino compounds. For example, urea is widely used as fertilizer in agriculture, and large amounts of volatile organic compounds (VOCs) are released from animal manure in livestock farms, including a certain proportion of ammonia. These emissions easily transform into free ammonia in the natural environment and spread to surrounding areas with the wind. As an important alkaline gas in the atmosphere, ammonia can undergo homogeneous neutralization reactions with nitric acid or sulfuric acid to form secondary aerosols of nitrates and sulfates, promoting the formation of PM2.5. Because ammonia is highly alkaline and has an extremely low recovery rate, large-scale release into the environment will cause acid mist formation, directly poisoning soil enzyme activity and accelerating soil acidification. Therefore, accurate and timely ammonia monitoring is crucial for protecting the environment and safeguarding human health and safety.

[0003] Currently, methods for detecting ammonia mainly include chromatography, mass spectrometry, spectroscopy, and electrochemical sensors. Chromatography is suitable for offline detection in laboratories. However, gas sample pretreatment is complex and cumbersome, sample separation time is long, and chromatographic columns are prone to aging after long-term use, making it unsuitable for long-term continuous online measurement of gas samples. Mass spectrometry has been increasingly applied to the monitoring of trace gases in the atmospheric environment in recent years. For example, soft ionization mass spectrometry (SIMS) and chemical ionization mass spectrometry (CIMS) can quickly and sensitively monitor gases such as ammonia in ambient air with low detection limits, but the instruments are large and expensive. Spectroscopic methods, such as Fourier transform infrared spectroscopy (FTIR), tunable diode laser (TDL), quantum cascade tunable infrared laser differential absorption spectrometry (QC-TILDAS), and differential optical absorption spectroscopy (DOAS), have advantages such as fast response speed, high sensitivity, and high time resolution. However, they also have some disadvantages, such as susceptibility to interference from water vapor and CO2, complex signal acquisition systems, large equipment size, and high cost. Electrochemical sensors are mainly suitable for small-scale gas detection. Their storage conditions are greatly affected by ambient temperature, humidity, and air pressure, resulting in a short actual service life and low sensitivity, typically in the ppm range. Summary of the Invention

[0004] To address the problems of existing technologies, this invention provides an ammonia detection device and method based on corona discharge ionization technology and ion mobility spectrometry (CD-IMS). Using a corona discharge ionization source in positive ion mode, a separate channel of water vapor is introduced to generate a reaction reagent ion (H₂O)nH₂ with a certain intensity. + The reacting ion can react with ammonia gas to produce the product ion (H2O)nNH4. + This enables highly sensitive qualitative and quantitative detection of ammonia.

[0005] The technical solution adopted in this invention is as follows:

[0006] This invention employs corona discharge ion mobility spectrometry. In positive ion mode, by adding a high concentration of water vapor, reactant ions (H₂O)nH are generated. + The reacting ions react with the highly selective molecular ions of ammonia to form the product ion (H₂O)nNH₄. + Because different ions migrate at different rates in the migration region, they arrive at the ion receiving electrode at different times, resulting in ion peaks with different migration times appearing in the spectrum, which can be separated and analyzed.

[0007] This invention provides an ammonia detection device based on corona discharge ion mobility spectrometry, comprising an ion migration tube, a signal amplifier, an A / D converter, and a computer data processing system. The ion migration tube comprises, in sequence, a corona discharge ionization source (composed of a discharge needle and a discharge electrode), a reaction zone, an ion gate, a migration zone, and an ion receiving electrode, all placed coaxially. The ionization source has a discharge gas inlet, a tail gas outlet on its outer wall near one end, a sample gas inlet on its outer wall near the ion gate, a water vapor inlet at the front end of the sample gas inlet, and a drift gas inlet on its outer wall near the ion receiving electrode. The signal amplifier is connected to the ion migration tube on one side and to the A / D converter on the other side. The A / D converter is connected to the computer data processing system.

[0008] Based on the above technical solution, further, the discharge gas inlet is connected to mass flow meter I, the water vapor inlet is connected to the water vapor generator, and the water vapor generator bottle is connected to mass flow meter II. The drift gas inlet is connected to mass flow meter III, and the sample gas inlet is connected to mass flow meter IV.

[0009] Based on the above technical solution, further, the water vapor generating device consists of a glass bottle containing pure water placed inside a constant-temperature heated shell, with small holes on the surface of the bottle mouth for evaporation; by purging with a carrier gas at a certain flow rate, the device can generate water vapor of a constant concentration and enter the ion migration tube.

[0010] This invention provides a method for detecting ammonia using the aforementioned device. Discharge gas enters the ionization source at a certain flow rate through the discharge gas inlet of mass flow meter I. Carrier gas, at a certain flow rate through mass flow meter II, passes through a water vapor generator to produce high-concentration water vapor (1000-25000 ppm), which enters the reaction zone of the ion migration tube through the water vapor inlet. Drift gas enters the migration zone of the ion migration tube at a certain flow rate through the drift gas inlet of mass flow meter III. Ammonia sample gas enters the reaction zone of the ion migration tube at a certain flow rate through the sample gas inlet of mass flow meter IV. In positive ion mode, ammonia is ionized by a corona discharge ionization source composed of a discharge needle and discharge electrodes. The resulting ion clusters are periodically controlled by ion gates in the reaction zone, enter the migration zone, and reach the ion receiving electrode for detection. The generated current signal is output through a signal amplifier and an A / D data converter, and recorded and stored in a computer data processing system.

[0011] Based on the above technical solutions, the drift gas, discharge gas, and carrier gas can be selected from one or more of air, nitrogen, helium, and hydrogen.

[0012] Based on the above technical solutions, further, the drift gas flow rate is 100-500 ml / min, the discharge gas flow rate is 10-300 ml / min, the water vapor flow rate is 10-200 ml / min, the sample gas flow rate is 10-300 ml / min, the ion migration tube temperature is 40-160℃, and the water vapor generator heating temperature is 40-60℃.

[0013] The advantages of this invention are as follows:

[0014] 1. The method of this invention introduces a high concentration of water vapor, which causes corona discharge ionization to generate a higher concentration of reactant ions (H2O)nH. + The reacting ions can undergo a highly selective molecular ion reaction with ammonia to produce the product ion (H₂O)nNH₄. + This enables highly sensitive qualitative and quantitative detection of ammonia.

[0015] 2. The method of the present invention has an extremely fast analysis speed, with a response time of less than 1 second, and can realize continuous monitoring of ammonia gas, and has broad application prospects. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the corona discharge ion migration spectrum in this invention. In the diagram, 1 is the discharge needle, 2 is the discharge electrode, 3 is the discharge gas inlet, 4 is the tail gas outlet, 5 is the sample gas inlet, 6 is the water vapor inlet, 7 is the drift gas inlet, 8 is mass flow meter I, 9 is mass flow meter II, 10 is the water vapor generator, 11 is the mass flow meter III, 12 is the mass flow meter IV, 13 is the reaction zone, 14 is the ion gate, 15 is the migration zone, 16 is the ion receiving electrode, 17 is the ion migration tube, 18 is the signal amplifier, 19 is the A / D data converter, and 20 is the computer data processing system.

[0017] Figure 2 To adopt Figure 1 The reaction reagent ions (H2O)nH measured by the structural device + Ion migration spectra.

[0018] Figure 3 To adopt Figure 1 The ion migration spectrum of 500 ppb ammonia gas was measured using the structural device. Detailed Implementation

[0019] The following examples illustrate the use of the present invention, but do not limit the scope of application.

[0020] Example 1

[0021] like Figure 1As shown, an ammonia detection device based on corona discharge ion mobility spectrometry technology includes an ion migration tube 17, a signal amplifier 18, an A / D data converter 19, and a computer data processing system 20. The ion migration tube 17 includes a corona discharge ionization source composed of a discharge needle 1 and a discharge electrode 2, a reaction zone 13, an ion gate 14, a migration zone 15, and an ion receiving electrode 16, all placed coaxially in sequence. The ionization source has a discharge gas inlet 3, a tail gas outlet 4 on its outer wall near one end, a sample gas inlet 5 on its outer wall near the ion gate 14, a water vapor inlet 6 at the front end of the sample gas inlet 5, and a drift gas inlet 7 on its outer wall near the ion receiving electrode 16. The discharge gas inlet 3 is connected to a mass flow meter I 8, the water vapor inlet 6 is connected to a water vapor generator 10, and the water vapor generator 10 is connected to a mass flow meter II 9. The drift gas inlet 7 is connected to a mass flow meter III 11, and the sample gas inlet 5 is connected to a mass flow meter IV 12. The signal amplifier 18 is connected to the ion migration tube 17 on one side and to the A / D data converter 19 on the other side. The A / D data converter 19 is connected to the computer data processing system 20.

[0022] Using the above-mentioned device to detect ammonia, the discharge gas enters the ionization source at a certain flow rate through the discharge gas inlet 3 via the mass flow meter I8. The carrier gas at a certain flow rate through the mass flow meter II9 passes through the water vapor generator 9 to generate high-concentration water vapor, which enters the reaction zone 13 of the ion migration tube 17 through the water vapor inlet (6). The drift gas enters the migration zone 15 of the ion migration tube at a certain flow rate through the drift gas inlet 7 via the mass flow meter III11. The ammonia sample gas enters the reaction zone 13 of the ion migration tube 17 at a certain flow rate through the sample gas inlet 5 via the mass flow meter IV12. In positive ion mode, the ammonia sample gas is ionized by the corona discharge ionization source composed of the discharge needle 1 and the discharge electrode 2. The ion clusters obtained by ionization enter the migration zone 15 through the periodic control of the ion gate 14 in the reaction zone 13, and reach the ion receiving electrode 16 for detection. The generated current signal is output through the signal amplifier 18 and the A / D data converter 19, and is recorded and stored in the computer data processing system 20.

[0023] Example 2

[0024] Ammonia gas was detected using the ammonia gas detection device based on corona discharge ion mobility spectrometry technology of the present invention. Clean air was used as the discharge gas, purging gas, and carrier gas. The discharge gas flow rate was 100 ml / min, the carrier gas flow rate for purging water vapor was 100 ml / min, the purging gas flow rate was 400 ml / min, the ion mobility tube temperature was 150°C, the water vapor generator heating temperature was 40°C, and the door opening time was 50 μs. The resulting reagent ion (H2O)nH was obtained. + Corona discharge ion migration spectrum. (Example:) Figure 2As shown, a strong (H2O)nH was generated. + The peak signal strength is 2605mV.

[0025] Example 3

[0026] Using the corona discharge ion mobility spectrometer of this invention, clean air was used as the discharge gas, purging gas, and water vapor carrier gas. The discharge gas flow rate was 100 ml / min, the water vapor carrier gas flow rate was 100 ml / min, the purging gas flow rate was 400 ml / min, the ion mobility tube temperature was 150°C, the water vapor generator heating temperature was 40°C, and the door opening time was 50 μs. Ammonia gas with a concentration of 500 ppb was introduced at a flow rate of 200 ml / min from the sample gas inlet 5, resulting in a corona discharge ion mobility spectrum of 500 ppb ammonia. (For example...) Figure 3 As shown, the product ion signal intensity of the 500ppb ammonia standard gas was 2131mV.

Claims

1. An ammonia detection device based on corona discharge ion mobility spectrometry, comprising an ion migration tube (17), a signal amplifier (18), an A / D data converter (19), and a computer data processing system (20), characterized in that: The ion migration tube (17) includes a corona discharge ionization source composed of a discharge needle (1) and a discharge electrode (2) arranged coaxially in sequence, a reaction zone (13), an ion gate (14), a migration zone (15), and an ion receiving electrode (16); the ionization source is provided with a discharge gas inlet (3), a tail gas outlet (4) is provided on the outer wall near one end of the ionization source, a sample gas inlet (5) is provided on the outer wall near one end of the ion gate (14), a water vapor inlet (6) is provided at the front end of the sample gas inlet (5), and a drift gas inlet (7) is provided on the outer wall near one end of the ion receiving electrode (16); the signal amplifier (18) is connected to the ion migration tube on one side and to an A / D data converter (19) on the other side, and the A / D data converter is connected to a computer data processing system (20).

2. The apparatus according to claim 1, characterized in that: The discharge gas inlet (3) is connected to mass flow meter I (8), the water vapor inlet (6) is connected to water vapor generator (10), the water vapor generator (10) is connected to mass flow meter II (9), the drift gas inlet (7) is connected to mass flow meter III (11), and the sample gas inlet (5) is connected to mass flow meter IV (12).

3. The apparatus according to claim 2, characterized in that: The water vapor generator consists of a glass bottle containing pure water placed inside a constant-temperature heated shell, with holes on the bottle mouth surface for evaporation; water vapor of a constant concentration is generated by purging with a carrier gas at a certain flow rate and enters the ion migration tube (17).

4. A method for detecting ammonia using the apparatus described in claim 1, 2, or 3, characterized in that: The discharge gas enters the ionization source at a certain flow rate through the discharge gas inlet (3) via mass flow meter I (8). The carrier gas, which passes through mass flow meter II (9) at a certain flow rate, passes through the water vapor generated by the water vapor generator (10) and enters the reaction zone (13) of the ion migration tube (17) at the water vapor inlet (6). The drift gas enters the migration zone (15) of the ion migration tube (17) at a certain flow rate through mass flow meter III (11) via the drift gas inlet (7). The ammonia sample gas enters the sample gas inlet at a certain flow rate through mass flow meter IV (12). (5) Entering the reaction zone (13) of the ion migration tube (17); In positive ion mode, ammonia gas is ionized by a corona discharge ionization source composed of a discharge needle (1) and a discharge electrode (2). The ion cluster obtained by ionization enters the migration zone (15) through the periodic control of the ion gate (14) in the reaction zone (13), reaches the ion receiving electrode (16) for detection, and generates a current signal which is output by the signal amplifier (18) and the A / D data converter (19) and recorded and stored in the computer data processing system (20).

5. The method according to claim 4, characterized in that: The bleaching gas, discharge gas, and carrier gas are selected from one or more of the following: air, nitrogen, helium, and hydrogen.

6. The method according to claim 4 or 5, characterized in that: The drift gas flow rate is 100-500 ml / min, the discharge gas flow rate is 10-300 ml / min, the water vapor flow rate is 10-200 ml / min, the sample gas flow rate is 10-300 ml / min, the ion migration tube temperature is 40-160 ℃, the water vapor generator heating temperature is 40-60 ℃, and the water vapor concentration is 1000-25000 ppm.

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