Ion mobility spectrometry and applications thereof

Abstract

The application discloses an ion mobility spectrometry and application thereof. The ion mobility spectrometry adopts butanone / water dimolecule as reagent molecules, and converts the butanone / water into hydrated ions by using a vacuum ultraviolet lamp. The ion mobility spectrometry is non-radioactive, and uses the hydrated ions as reagent ions, which is helpful to improve the detection sensitivity of polar compounds. The structure of the ion mobility spectrometry comprises a vacuum ultraviolet lamp, an ion mobility spectrometry reaction zone, a reagent molecule generating device and the like.

Description

Technical Field

[0001] This invention belongs to the field of ion mobility spectrometry. The ion mobility spectrometry ionization source uses butanone / water bimolecules as reagent molecules, and utilizes a vacuum ultraviolet lamp to convert butanone / water into hydrated ions. This ion mobility spectrometry ionization source is non-radioactive, and using hydrated ions as reagent ions helps to improve the detection sensitivity of polar compounds. Technical Background

[0002] Hydrated ions are widely used reagent ions with a proton affinity of 696 kJ / mol and high selectivity, offering significant advantages for the detection of polar compounds, especially polar inorganic compounds. Currently, the main ionization sources capable of generating hydrated ions in mobility spectrometry are radioactive... 63 Ni ionization sources and corona discharge ionization sources. Huang Wei [CN201510890326.0] achieved online monitoring of ammonia using hydrated ions as reagent molecules through ion mobility spectrometry. However, the radioactivity of nickel ionization sources limits their widespread application in ion mobility spectrometry.

[0003] The vacuum ultraviolet photoionization source is a soft ionization source. The main photon energy of the krypton lamp is 10.0 eV, while the ionization energy of water is 12.6 eV. Therefore, water cannot be directly ionized by the krypton lamp, and thus cannot produce hydrated ion reagent ions. Summary of the Invention

[0004] The purpose of this invention is to provide a new ion mobility spectrum, in which the ionization source combines vacuum ultraviolet photoionization with chemical ionization to generate hydrated ion reagent ions, enabling the effective ionization and detection of polar compounds, especially polar inorganic compounds.

[0005] An ionization source for ion mobility spectrometry includes: an ion mobility spectrometry reaction region, a vacuum ultraviolet lamp, and a reagent molecule generating device.

[0006] The ion mobility spectrometer includes the ion mobility tube reaction region, the ion mobility tube migration region, and the ion mobility tube signal acquisition and reception region. The ion mobility tube reaction region and the ion mobility tube migration region are separated by a grid. A vacuum ultraviolet lamp serving as an ionization source is located at the left end of the ion mobility tube reaction region. A carrier gas inlet and a tail gas outlet are located on the outer wall surface near the left side of the ion mobility tube reaction region. A water vapor inlet is located on the outer wall surface near the middle of the ion mobility tube reaction region. A sample inlet is located on the outer wall surface near the right side of the ion mobility tube reaction region.

[0007] The carrier gas inlet is connected to the carrier gas source via a reagent molecule generator;

[0008] The water vapor inlet is connected to the carrier gas source via a water vapor generator;

[0009] The water vapor generator is a closed container filled with water. The carrier gas source extends into the container below the water surface through a pipeline, and the water vapor is carried out of the container through the water vapor inlet to the reaction zone by bubbling.

[0010] The reagent molecule generating device is a closed container with a gas inlet and a gas outlet. The carrier gas source is connected to the gas inlet, and the gas outlet is connected to the carrier gas inlet through a pipeline. A container with an open top filled with methyl ethyl ketone is placed inside the closed container. The volatilized reagent molecule methyl ethyl ketone is carried to the reaction zone by the carrier gas.

[0011] The reaction zone is composed of stacked stainless steel electrode rings and polytetrafluoroethylene (PTFE) insulating rings. The thickness of the stainless steel electrode rings is 0.35 cm. The thickness of the PTFE insulating rings is 1 cm. The vacuum ultraviolet lamp is placed axially perpendicular to the stainless steel electrode rings and PTFE insulating rings, with its center located on the axis of the stainless steel electrode rings and PTFE insulating rings.

[0012] A carrier gas inlet and a tail gas outlet are located opposite each other on the PTFE insulation near the vacuum UV lamp. A water vapor inlet is located on the PTFE insulation ring to the right of the tail gas outlet, and a sample inlet is located on the PTFE insulation ring to the right of the water vapor inlet. The carrier gas enters the ion mobility spectrometry reaction zone through the reagent molecule generator. Water vapor enters the ion mobility spectrometry reaction zone through the water vapor inlet. Sample gas enters the ion mobility spectrometry reaction zone through the sample inlet. The tail gas exits the ion mobility spectrometry reaction zone through the tail gas outlet.

[0013] The reagent molecule generator has an electric heating device on its inner wall, that is, an electric heating belt or electric heating wire is provided on the inner wall surface of the reagent molecule generator, and a thermocouple temperature measuring element is provided on the side wall of the reagent molecule generator. The temperature measuring thermocouple is connected to the temperature controller signal through a wire, and the electric heating device is connected to the external circuit through the temperature controller.

[0014] The reagent molecules are butanone and water. The relative humidity is 100%.

[0015] The carrier gas flow rate is 50-100 ml / min, the water vapor flow rate is 100-200 ml / min, the sample gas injection rate is 100-300 ml / min, and the drift gas flow rate is 400-600 ml / min.

[0016] The carrier gas used and the gas that generates water vapor are both purified clean air;

[0017] The temperature range of the ion migration tube is between 90-150℃.

[0018] The advantages of this invention are:

[0019] This invention proposes an ion mobility spectrometry method. The ionization source is non-radioactive and can generate hydrated reagent ions with higher signal intensity than the nickel ionization source, thereby improving the ionization efficiency and detection sensitivity of the target compound. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of ion mobility spectrometry. Where: 1 is the reaction zone, 2 is the migration zone, 3 is the stainless steel grid, 4 is the signal acquisition and receiving zone, 5 is the carrier gas, 6 is the reagent molecule generator, 7 is the vacuum UV lamp, 8 is the tail gas outlet, 9 is the water vapor inlet, 10 is the sample gas inlet, 11 is the drift gas inlet, 12 is the Faraday disk, 13 is the amplifier, 14 is the acquisition card and computer, 15 is the stainless steel electrode, and 16 and 17 are polytetrafluoroethylene insulating rings.

[0021] Figure 2 A comparison of the signal intensity of hydrated ions generated by the nickel source and the new ionization source;

[0022] Figure 3 The migration spectrum of 20 ppb ammonia gas obtained using a new ionization source. Detailed Implementation Plan

[0023] The following examples illustrate the use of the present invention, but do not limit the scope of application.

[0024] An ion mobility spectrometer includes an ion mobility tube reaction region, an ion mobility tube migration region, and an ion mobility tube signal acquisition and reception region. The ion mobility tube reaction region and the ion mobility tube migration region are separated by a grid. A vacuum ultraviolet lamp serving as an ionization source is provided at the left end of the ion mobility tube reaction region. A carrier gas inlet and a tail gas outlet are provided on the outer wall surface near the left side of the ion mobility tube reaction region. A water vapor inlet is provided on the outer wall surface near the middle of the ion mobility tube reaction region. A sample inlet is provided on the outer wall surface near the right side of the ion mobility tube reaction region.

[0025] The carrier gas inlet is connected to the carrier gas source via a reagent molecule generator;

[0026] The water vapor inlet is connected to the carrier gas source via a water vapor generator;

[0027] The water vapor generator is a closed container filled with water. The carrier gas source extends into the container below the water surface through a pipeline, and the water vapor is carried out of the container through the water vapor inlet to the reaction zone by bubbling.

[0028] The reagent molecule generating device is a closed container with a gas inlet and a gas outlet. The carrier gas source is connected to the gas inlet, and the gas outlet is connected to the carrier gas inlet through a pipeline. A container with an open top filled with methyl ethyl ketone is placed inside the closed container. The volatilized reagent molecule methyl ethyl ketone is carried to the reaction zone by the carrier gas.

[0029] Example 1

[0030] The performance of the ionization source described in this invention was investigated. A 10.0 eV krypton lamp was used as the vacuum ultraviolet lamp, and the ionization source was applied to ion mobility spectrometry. The carrier gas flow rate was 50 ml / min, the water vapor flow rate was 260 ml / min, and the reaction zone temperature was 150 °C. Figure 2 As shown, the signal intensity of the reagent ions obtained by the new ionization source is approximately 4000 mV, which is four times that of the nickel ionization source. Therefore, the sensitivity of this ionization source is higher than that of the nickel ionization source.

[0031] Nickel source ionization source uses radioactivity 63 Ni, as an ionization source, is commonly used in ion mobility spectrometry with a cylindrical geometry. Nickel ionization sources can generate energies of approximately 17 keV. In positive ion mode, the reagent ions produced by nickel ionization sources are hydrated ions. Example 2

[0032] The performance of the ion mobility spectrometry described in this invention was investigated. This ion mobility spectrometry was applied to ion mobility spectrometry by introducing 20 ppb ammonia gas through the sample inlet. The resulting ion mobility spectrum of the ammonia gas is shown below. Figure 3 As shown. This ionization source has high sensitivity for ammonia detection, with a detection limit (LOD) of 0.22 ppb. Furthermore, this ionization source was generated under conditions of 100% relative humidity, therefore the influence of humidity on ammonia detection can be disregarded, which is of great significance for practical applications.

Claims

1. An ion mobility spectrum, characterized in that: The ion mobility spectrometer includes an ion mobility tube reaction region, an ion mobility tube migration region, and an ion mobility tube signal acquisition and receiving region. The ion mobility tube reaction region and the ion mobility tube migration region are separated by a grid. A vacuum ultraviolet lamp serving as an ionization source is provided at the left end of the ion mobility tube reaction region. A carrier gas inlet and a tail gas outlet are provided on the outer wall surface near the left side of the ion mobility tube reaction region. A water vapor inlet is provided on the outer wall surface near the middle of the ion mobility tube reaction region. A sample inlet is provided on the outer wall surface near the right side of the ion mobility tube reaction region. The carrier gas inlet is connected to the carrier gas source via a reagent molecule generator; The water vapor inlet is connected to the carrier gas source via a water vapor generator; The water vapor generator is a closed container filled with water. The carrier gas source extends into the container below the water surface through a pipeline, and the water vapor is carried out of the container through the water vapor inlet to the reaction zone by bubbling. The reagent molecule generating device is a closed container with a gas inlet and a gas outlet. The carrier gas source is connected to the gas inlet, and the gas outlet is connected to the carrier gas inlet through a pipeline. A container filled with butanone with an open top is placed inside the closed container. The volatilized reagent molecule butanone is carried to the reaction zone by the carrier gas. The relative humidity of the gas entering through the water vapor inlet is 100%. The migration spectrum uses methyl ethyl ketone (MEK) / water bimolecules as reagent molecules, and uses a vacuum UV lamp to convert MEK / water into hydrated ions.

2. The ion mobility spectrometry according to claim 1, characterized in that: The reaction zone is formed by alternating stacks of stainless steel electrode rings and polytetrafluoroethylene (PTFE) insulating rings; the thickness of the stainless steel electrode rings is 0.35 cm, and the thickness of the PTFE insulating rings is 1 cm; the optical axis of the emitted light from the vacuum ultraviolet lamp is placed coaxially with the stainless steel electrode rings and the PTFE insulating rings, and its optical axis is located on the axis of the stainless steel electrode rings and the PTFE insulating rings. The migration zone is composed of alternating stacks of stainless steel electrode rings and polytetrafluoroethylene (PTFE) insulating rings; the thickness of the stainless steel electrode rings is 0.35 cm, and the thickness of the PTFE insulating rings is 0.15 cm. The migration zone and the reaction zone are separated by two stainless steel metal grids; The signal acquisition and reception area consists of a Faraday disk, amplifier, acquisition card, and computer.

3. The ion mobility spectrometry according to claim 1 or 2, characterized in that: A carrier gas inlet and a tail gas outlet are respectively provided at positions opposite to the polytetrafluoroethylene insulation near the vacuum ultraviolet lamp; A water vapor inlet is set on the polytetrafluoroethylene insulating ring to the right of the exhaust gas outlet, and a sample inlet is set on the polytetrafluoroethylene insulating ring to the right of the water vapor inlet; the carrier gas enters the ion mobility spectrometry reaction zone through the reagent molecule generator; the water vapor enters the ion mobility spectrometry reaction zone through the water vapor inlet; Sample gas enters the ion mobility spectrometry reaction zone through the sample inlet; tail gas exits the ion mobility spectrometry reaction zone through the tail gas outlet.

4. The ion mobility spectrometry according to claim 1, characterized in that: The reagent molecule generator has an electric heating device on its inner wall, that is, an electric heating belt and / or electric heating wire are provided on the inner wall surface of the reagent molecule generator, and a thermocouple temperature measuring element is provided on the side wall inside the reagent molecule generator. The temperature measuring thermocouple is connected to the temperature controller signal through a wire, and the electric heating device is connected to the external circuit through the temperature controller.

5. The ion mobility spectrometry according to claim 1, characterized in that: The carrier gas inlet flow rate is 50-100 mL / min, the water vapor inlet flow rate is 100-200 mL / min, and the sample gas injection rate is 100-300 mL / min.

6. The ion mobility spectrometry according to claim 1, characterized in that: The carrier gas used to carry the reagent molecule methyl ethyl ketone and the carrier gas that generates water vapor are both purified clean air.

7. The ion mobility spectrometry according to claim 1, characterized in that: The temperature range of the reaction zone is between 90-150℃.

8. An application of the ion mobility spectrometry described in any one of claims 1-7, characterized in that: It is used to detect one or more of the following polar compounds: ammonia, trimethylamine, and nitro compounds.

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