An ion mobility spectrometry device using dual-window ultraviolet lamp ionization

Abstract

The present invention discloses an ion mobility spectrometry device using a dual-window ultraviolet lamp for ionization, which relates to the technical field of ion mobility spectrometry. The ionization source of the ion mobility spectrometry device is a dual-window ultraviolet lamp, and the dual-window ultraviolet lamp includes: a glass tube, a first ultraviolet window, a second ultraviolet window, and an excitation electrode. The first ultraviolet window and the second ultraviolet window are respectively arranged at both ends of the glass tube. The glass tube is filled with a working gas, and the excitation electrode is arranged on the outer wall of the glass tube. This solution realizes simultaneous photoionization of the analyte while only using one ultraviolet light source. The light intensities of the two ultraviolet windows can be synchronously kept consistent, improving the correlation of positive and negative ion mobility spectrometry, ensuring that the ionization efficiencies on both sides are close, and reducing the occupation of the lamp body on the volume of the ion mobility spectrometry device. And because only one lamp is driven, the energy consumption is reduced, and a set of drive circuits is reduced, reducing the necessary volume and weight of the device from the lamp and the circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of ion mobility spectrometry, and particularly to an ion mobility spectrometry device using a dual-window ultraviolet lamp for ionization. Background Art

[0002] Ion mobility spectrometry usually uses the rays of radioactive substances to ionize molecules such as water and oxygen in the air. These molecules continue to interact with gaseous molecules to be detected to form ion clusters. By collecting and detecting the weak electrical signals generated by the ion clusters, the composition of the gas to be detected can be qualitatively analyzed. Since the use of radioactive substances is dangerous, currently using ultraviolet light to ionize the gas to be detected has become a more ideal alternative.

[0003] However, currently, ion mobility spectrometry devices using ultraviolet photoionization methods usually have only one migration tube and need to frequently switch the electric field. A single electric field can only detect ions of one electrical property at the same time, and there is also a waiting time for ion rebalancing, resulting in a too long detection process and poor detection reliability. If a dual-migration-tube design is adopted, one migration tube can be constantly used for migrating positive ions, and the other migration tube can be constantly used for migrating negative ions. However, due to the fixed electric field, the ionization region electric field is also opposite. Therefore, two independent ionization regions are required to generate ions of different electrical properties. If traditional ultraviolet lamps are used for ionization, two independent ultraviolet lamps are needed to achieve this, which may lead to problems such as poor consistency and different aging speeds of the ultraviolet lamps, affecting the detection and judgment of ion mobility spectrometry devices. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an ion mobility spectrometry device using a dual-window ultraviolet lamp for ionization in view of the deficiencies of the prior art.

[0005] The technical solution for the present invention to solve the above technical problems is as follows:

[0006] An ion mobility spectrometry device using a dual-window ultraviolet lamp for ionization, wherein the ionization source of the ion mobility spectrometry device is a dual-window ultraviolet lamp. The dual-window ultraviolet lamp includes: a glass tube, a first ultraviolet window, a second ultraviolet window, and an excitation electrode. The first ultraviolet window and the second ultraviolet window are respectively arranged at both ends of the glass tube. The glass tube is filled with a working gas. The excitation electrode is arranged on the outer wall of the glass tube. The first ultraviolet window is used to ionize gas molecules to be detected to generate positive ions, and the second ultraviolet window is used to ionize gas molecules to be detected to generate negative ions.

[0007] The ion mobility spectrometry device using dual-window ultraviolet lamp ionization provided by this solution can realize simultaneous ionization of the analyte with only one ultraviolet light source by respectively arranging ultraviolet windows at both ends of a glass tube, with each ultraviolet window facing an ionization region, which can be respectively used for continuous positive ion ionization and negative ion ionization. The light intensities of the two ultraviolet windows can be synchronously kept consistent, improving the correlation of positive and negative ion mobility spectra, ensuring that the ionization efficiencies on both sides are close, and eliminating the need to switch the electric fields in the ionization region and the migration region, thus improving the detection speed and reliability. The structural features of the present invention reduce a set of light source drive circuits and electric field switching circuits, improve the reliability of the device, reduce the power consumption and volume of using multiple lamp bodies and electric field switching circuits, and reduce the necessary volume and weight of the device from the aspects of lamps and circuits.

[0008] Advantages of additional aspects of the present invention will be partly given in the following description, partly become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 FIG. is a schematic structural diagram provided for an embodiment of the dual-window ultraviolet lamp of the present invention;

[0010] Figure 2 FIG. is a schematic structural framework diagram provided for an embodiment of the ion mobility spectrometry device using dual-window ultraviolet lamp ionization of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0011] The principles and features of the present invention will be described below with reference to the accompanying drawings. The illustrated embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0012] Traditional ion mobility spectrometry devices use radioactive metal isotopes (such as 63 Ni, 241 Am) to ionize water and oxygen molecules in the air and further combine with the analyte to generate ions. However, these materials often require strict management, and the devices may pose hazards to personnel and environmental pollution after maintenance or damage. Ultraviolet light is non-radioactive, the photoionization process is stable, less affected by factors such as environmental humidity and pollution, and has advantages such as a small volume of the drive circuit, so it has been widely studied.

[0013] Due to the different tendencies of the analyte to gain or lose electrons, different analytes can be ionized by ultraviolet light to form positive ions and electrons, or the photoelectric effect can be generated by ultraviolet light exciting a metal coating. These low-energy electrons combine with oxygen molecules to form O2 -Ions with negative electronegativity, such as, combine with the detected gas molecules to form negative ions, completing the ionization process. These positive and negative product ions enter the migration region through the ion gate controlled by a periodic voltage under the action of electric fields in different directions. To prevent the generated analyte ions from recombining with other ions of opposite electric charge into neutral molecules, there is an electric field in the ionization region to move the gas to be detected to the front of the ion gate and keep the ions of other electric charges away from the ion gate. When the ion gate is opened, in the migration region, on the one hand, the ions obtain energy from the electric field for directional drift, and on the other hand, they continuously collide with the neutral migration gas molecules flowing in the reverse direction and lose energy. Since the masses, charges, collision cross-sections, and spatial configurations of these product ions are different, their migration rates in the electric field are different, so different ions reach the detector at different times, resulting in separation. To detect gases that may generate positive and negative ions, some ion mobility spectrometry devices use a dual ionization region and migration region design, so at least two photoionization sources are required.

[0014] Therefore, electric fields need to be set in both the ionization region and the migration region, and the electric field directions for positive and negative ions are opposite. The electric field needs to be switched frequently. Since a single electric field can only detect ions of one electric charge at the same time and there is also a waiting time for ion rebalancing, the detection process takes too long and the detection reliability is poor. And because the electric field intensity used in ion mobility spectrometry is relatively large, generally 3 kV to 5 kV, the circuit part supporting high-voltage switching is large in volume and weight. Therefore, for scenarios with high sensitivity or the need to detect positive and negative ions simultaneously, a dual migration tube design is often used, that is, one migration tube is constantly used for migrating positive ions and the other migration tube is constantly used for migrating negative ions.

[0015] In the above dual-tube design, since it is for positive and negative ions, the electric fields in the internal ionization region and migration region are fixed and opposite, so two independent ionization regions are required to generate ions of different electric charges. To ensure the comparability and relevance of the data on both sides, such as whether the analyte is mainly positive ions or negative ions, the ionization efficiencies of the two ionization regions are required to be the same or similar and have a consistent change trend. When using multiple traditional single-window photoionization methods, there are uncontrollable production differences in various aspects such as the gas concentration, purity, and window cleanliness of different ultraviolet lamps. During use, the attenuation rates of air leakage and other factors of different ultraviolet lamp bodies are also different. Therefore, there are many initial matching problems and calibration problems during use, resulting in poor consistency between the positive and negative ion regions and possible additional maintenance problems in the later stage.

[0016] To solve the above problems, this patent proposes an ion mobility spectrometry device using dual-window ultraviolet lamp ionization. The ultraviolet lamp with a single lamp body and dual ultraviolet windows is used as the ionization source. Each ultraviolet window faces an ionization region, enabling the simultaneous ionization of the analyte with only one light source. For the specific design structure of the ultraviolet lamp with a single lamp body and dual ultraviolet windows, reference can be made to Figure 1 。

[0017] As Figure 1 shown, it is a schematic structural diagram provided for an embodiment of the dual-window ultraviolet lamp of the present invention. The dual-window ultraviolet lamp includes: a glass tube 4, a first ultraviolet window 2, a second ultraviolet window 7, and an excitation electrode 5. The first ultraviolet window 2 and the second ultraviolet window 7 are respectively arranged at both ends of the glass tube 4. The glass tube 4 is filled with a working gas. The excitation electrode 5 is arranged on the outer wall of the glass tube 4. The first ultraviolet window 2 is used to ionize the gas molecules to be measured, generating positive ions, and the second ultraviolet window 7 is used to ionize the gas molecules to be measured, generating negative ions.

[0018] Next, the working principle of the dual-window ultraviolet lamp will be described.

[0019] After the excitation electrode 5 on the outer wall of the glass tube 4 is energized, it can excite the ultraviolet lamp filled with the working gas to emit ultraviolet light of a certain intensity. This ultraviolet light can ionize some organic and inorganic gas molecules near the light source, generating ions. Specifically, the gas molecules to be measured in the positive ionization region are ionized through the first ultraviolet window 2, and the gas molecules to be measured in the negative ionization region are ionized through the second ultraviolet window 7. Since the light source is the same, the light intensity of the two ultraviolet windows is synchronously kept consistent, improving the correlation of the positive and negative ion mobility spectra and ensuring that the ionization efficiencies on both sides are close.

[0020] Then, these ions can be collected through the Faraday disk at the end of the migration region through the electric field selection and migration effects in the ionization region and the migration region, generating a weak current. This current is amplified by an amplifier circuit and finally produces an analog output of a low-resistance voltage signal. According to the mobility of the ions in the migration region, the detection and qualitative analysis of specific substances can be achieved. In addition, the gas molecule ions generated by ultraviolet light excitation are approximately proportional to the concentration of gas molecules. Therefore, when the gas type is known, the concentration of gas molecules can be determined.

[0021] It should be understood that since the outside of the second ultraviolet window 7 is the negative ionization region, a metal structure needs to exist on the outer surface of the second ultraviolet window 7. For example, it can be a metal mesh or a thin film. In this way, low-energy electrons are generated under the action of ultraviolet light excitation and further generate reactive ions such as O2 - etc.

[0022] Optionally, the ultraviolet window can be made of vacuum ultraviolet light transmissive materials such as LiF, MgF2, or CaF2. The excitation electrode 5 can be made of metal coatings such as Cu or Au. The working gas can be noble gases such as Kr or Xe.

[0023] The ion mobility spectrometry device provided in this embodiment has ultraviolet windows respectively arranged at both ends of the glass tube. Each ultraviolet window faces an ionization region and can be respectively used for continuous positive ion ionization and negative ion ionization, realizing simultaneous ionization of the analyte with only one ultraviolet light source. The light intensities of the two ultraviolet windows can be synchronously kept consistent, improving the correlation of positive and negative ion mobility spectra, ensuring that the ionization efficiencies on both sides are close, and eliminating the need to switch the electric fields in the ionization region and the migration region, thereby improving the detection speed and reliability. The structural features of the present invention reduce a set of light source drive circuits and electric field switching circuits, improve the reliability of the device, reduce the power consumption and volume of using multiple lamp bodies and electric field switching circuits, and reduce the necessary volume and weight of the device in terms of the lamps and circuits.

[0024] Optionally, in some possible implementation manners, a gas absorbent 14 is further arranged in the glass tube 4.

[0025] Optionally, the gas absorbent 14 can be made of an alloy material containing Zr, Al, and V.

[0026] Optionally, in some possible implementation manners, a metal mesh or film is arranged on the outer surface of the second ultraviolet window 7.

[0027] It should be understood that the ultraviolet window provided with a metal mesh or film generates low-energy electrons under the action of ultraviolet light excitation and further generates O2 - , so the ultraviolet window provided with a metal mesh or film corresponds to the negative ionization region.

[0028] Optionally, in some possible implementation manners, the first ultraviolet window 2 and the second ultraviolet window 7 are made of the same vacuum ultraviolet light transmissive material.

[0029] By using the same vacuum ultraviolet light transmissive material to prepare the ultraviolet window, the correlation of positive and negative ion mobility spectra can be further improved, making the ionization efficiencies on both sides closer.

[0030] As Figure 2 shown, a more detailed optional structural schematic diagram of the ion mobility spectrometry device using dual-window ultraviolet lamp ionization is provided. The following describes some optional structures of the ion mobility spectrometry device using dual-window ultraviolet lamp ionization in conjunction with Figure 2 this.

[0031] The ion mobility spectrometry device using dual-window ultraviolet lamp ionization further includes: a vaporization and splitting chamber 1, a positive ionization region 3, a negative ionization region 6, two ion gates 8, a positive ion migration region 9, a negative ion migration region 10, two shielding grid meshes 11, two Faraday disks 12, and an electrical signal amplification circuit 13, where:

[0032] The two ion gates 8 are respectively arranged at the connection between the positive ionization region 3 and the positive ion migration region 9, and at the connection between the negative ionization region 6 and the negative ion migration region 10. The two shielding grid meshes 11 are respectively arranged at the tails of the positive ion migration region 9 and the negative ion migration region 10. The two Faraday disks 12 are respectively arranged at the tails of the positive ion migration region 9 and the negative ion migration region 10;

[0033] The vaporization and splitting chamber 1 is provided with an air inlet for the gas to be measured;

[0034] The first ultraviolet window 2 of the dual-window ultraviolet lamp is arranged in the positive ionization region 3. The first air inlet of the positive ionization region 3 is communicated with the vaporization and splitting chamber 1. The migration gas flow can enter the positive ionization region 2 from the migration region through the ion gate 8. The positive ionization region 3 and the positive ion migration region 9 are communicated through the ion gate 8 controlled by a periodic voltage. An air outlet is also arranged on the side wall of the positive ionization region 3;

[0035] The second ultraviolet window 7 of the dual-window ultraviolet lamp is arranged in the negative ionization region 6. The first air inlet of the negative ionization region 6 is communicated with the vaporization and splitting chamber 1. The migration gas flow can enter the negative ionization region through the ion gate 8 from the migration region. The second air inlet of the negative ionization region 6 is arranged on the ion gate 8. The negative ionization region 6 and the negative ion migration region 10 are communicated through the ion gate 8 controlled by a periodic voltage. An air outlet is also arranged on the side wall of the negative ionization region 6;

[0036] The shielding grid mesh 11 and the Faraday disk 12 in the positive ion migration region 9 are arranged at one end of the positive ion migration region 9 far from the ion gate 8. The Faraday disk 12 is connected to the electrical signal amplification circuit 13. An air inlet is arranged on the side wall of the positive ion migration region 9 for inputting the migration gas;

[0037] The shielding grid mesh 11 and the Faraday disk 12 in the negative ion migration region 10 are arranged at one end of the negative ion migration region 10 far from the ion gate 8. The Faraday disk 12 is connected to the electrical signal amplification circuit 13. An air inlet is arranged on the side wall of the negative ion migration region 10 for inputting the migration gas.

[0038] The electrical signal amplification circuit is used to amplify the electrical signals generated by the positive ionization structure and the negative ionization structure.

[0039] It should be understood that the positive ionization region, the first ion gate, the positive ion migration region, the first shielding grid and the first Faraday disk constitute the positive ionization structure. The positive ionization structure is only a functional expression and does not represent an actual device. The negative ionization region, the second ion gate, the negative ion migration region, the second shielding grid and the second Faraday disk constitute the negative ionization structure. The negative ionization structure is also only a functional expression and does not represent an actual device.

[0040] The working principle of an ion mobility spectrometry device using a dual-window ultraviolet lamp ionization is described below.

[0041] Apply high-voltage alternating current to the excitation electrode 5 of the dual-window ultraviolet lamp to excite the working gas in the glass tube 4 to emit light. Among them, the ultraviolet light enters the positive ionization region 3 and the negative ionization region 6 through the first ultraviolet window 2 and the second ultraviolet window 7 respectively;

[0042] The substance to be measured enters from the inlet of the vaporization and splitting chamber 1 for vaporization and splitting. The split gas enters the positive ionization region 3 from the first inlet of the positive ionization region 3 and enters the negative ionization region 6 from the first inlet of the negative ionization region 6 respectively;

[0043] The gas entering the positive ionization region 3 is ionized to generate positive ions under the action of the first ultraviolet window 2. The ion gate 8 is opened and closed through periodic voltage changes, enabling the positive ions to pass through the ion gate 8 and enter the positive ion migration region 9. The length range of the positive ion migration region 9 can be 5 - 30 cm, and there is an electric field of 100 V / cm - 300 V / cm, which can enable the positive ions to obtain energy and move the positive ions in the direction away from the first ion gate 8; There is also a migration gas in the positive ion migration region 9 in the direction opposite to the overall movement speed direction of the positive ions. The migration gas enters from the inlet arranged at the tail of the positive ion migration region 9. The ion gate 8 is a pair of parallel metal wires, which can help the migration gas enter the positive ionization region 3 from the ion gate 8. The migration gas, sample gas, etc. can be discharged through the air outlet on the side wall of the positive ionization region 3;

[0044] After the positive ions move to the Faraday disk 12, they contact the metal electrode on the surface of the Faraday disk 12 to generate a weak initial electrical signal, which is then amplified by the electrical signal amplification circuit 13 for the analysis of the gas composition;

[0045] The gas entering the negative ionization region 6 is ionized to generate negative ions under the action of the second ultraviolet window 7. The ion gate 8 is opened and closed through periodic voltage changes, enabling the negative ions to enter the negative ion migration region 10 through the ion gate 8. The length range of the negative ion migration region 10 can be 5 - 30 cm, with an electric field of 100 V / cm - 300 V / cm. The direction of the electric field is opposite to that of the positive ion migration region 9, which can enable the negative ions to obtain energy and move in a direction away from the ion gate 8. The negative ion migration region 10 also contains a migration gas moving in a direction opposite to the overall movement direction of the negative ions. The migration gas enters from the air inlet provided at the tail of the negative ion migration region 10. The ion gate 8 is a pair of parallel metal wires, which can help the migration gas enter the negative ionization region 6 from the ion gate 8. The migration gas, sample gas, etc. can be discharged through the air outlet on the side wall of the negative ionization region 6.

[0046] After the negative ions move to the Faraday disk 12, they come into contact with the metal electrode on the surface of the Faraday disk 12 to generate a weak initial electrical signal, which is then amplified by the electrical signal amplification circuit 13 for the analysis of the gas composition.

[0047] Among them, the shielding grid 11 provided in front of the Faraday disk 12 is used to shield the Faraday disk 12 to reduce interference during ion reception.

[0048] It can be understood that in some embodiments, it may include some or all of the above-described embodiments.

[0049] The reader should understand that in the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0050] In the several embodiments provided in this application, it should be understood that the disclosed device and method can be implemented in other ways. For example, the method embodiments described above are merely illustrative. For example, the division of steps is only a logical function division. In actual implementation, there may be other division methods. For example, multiple steps can be combined or integrated into another step, or some features can be ignored or not executed.

[0051] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An ion mobility spectrometry device using dual-window ultraviolet lamp ionization, characterized in that, The ionization source of the ion mobility spectrometry device is a dual-window ultraviolet lamp, and the dual-window ultraviolet lamp includes: a glass tube, a first ultraviolet window, a second ultraviolet window, and an excitation electrode. The first ultraviolet window and the second ultraviolet window are respectively arranged at two ends of the glass tube. The glass tube is filled with a working gas. The excitation electrode is arranged on the outer wall of the glass tube. The first ultraviolet window is used to ionize the gas molecules to be measured to generate positive ions, and the second ultraviolet window is used to ionize the gas molecules to be measured to generate negative ions; It further includes: a vaporization and splitting chamber, a positive ionization structure arranged outside the first ultraviolet window, and a negative ionization structure arranged outside the second ultraviolet window; Wherein, the vaporization and splitting chamber is provided with an air inlet for the gas to be measured, and is used to respectively transport the gas to be measured to the positive ionization structure and the negative ionization structure; the positive ionization structure is used to ionize the gas to be measured under the action of the first ultraviolet window to generate positive ions, and receive the positive ions to generate corresponding electrical signals; the negative ionization structure is used to ionize the gas to be measured under the action of the second ultraviolet window to generate negative ions, and receive the positive ions to generate corresponding electrical signals; The positive ionization structure includes: a positive ionization region, a first ion gate, a positive ion migration region, a first shielding grid, and a first Faraday disk. The first ultraviolet window of the dual-window ultraviolet lamp is arranged in the positive ionization region. The first air inlet of the positive ionization region is communicated with the vaporization and splitting chamber. The air outlet of the positive ionization region is arranged on the positive ionization region. The positive ionization region and the positive ion migration region are communicated through the periodically opened first ion gate. The ion gate is a pair of parallel metal wires, and the voltage across the metal wires controls the opening and closing of the ion gate for ions. The first shielding grid and the first Faraday disk are arranged at one end of the positive ion migration region far from the first ion gate. The second air inlet is arranged at the rear of the positive ion migration region. The second air inlet is introduced with purified migration gas during use, and flows out from the air outlet through the first ion gate; The negative ionization structure includes: a negative ionization region, a second ion gate, a negative ion migration region, a second shielding grid, and a second Faraday disk. The second ultraviolet window of the dual-window ultraviolet lamp is arranged in the negative ionization region. The first air inlet of the negative ionization region is communicated with the vaporization and splitting chamber. The air outlet of the negative ionization region is arranged on the negative ionization region. The negative ionization region and the negative ion migration region are communicated through the periodically opened second ion gate. The ion gate is a pair of parallel metal wires, and the voltage across the metal wires controls the opening and closing of the ion gate for ions. The second shielding grid and the second Faraday disk are arranged at one end of the negative ion migration region far from the second ion gate. The second air inlet is arranged at the rear of the positive ion migration region. The second air inlet is introduced with purified migration gas during use, and flows out from the air outlet through the second ion gate; Further included is: an electrical signal amplification circuit for amplifying the electrical signals generated by the positive ionization structure and the negative ionization structure.

2. The ion mobility spectrometry device using dual-window ultraviolet lamp ionization according to claim 1, wherein A gas absorbent is further provided inside the glass tube.

3. The ion mobility spectrometry device using dual-window ultraviolet lamp ionization according to claim 1, characterized in that, A metal wire mesh or a thin film is provided on the outer surface of the second ultraviolet window.

4. The ion mobility spectrometry device using dual-window ultraviolet lamp ionization according to claim 1, characterized in that, The first ultraviolet window and the second ultraviolet window are made of the same material that can be penetrated by vacuum ultraviolet light.

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