Photoionization ion mobility tube with adjustable reagent ions

Abstract

This invention discloses a photoionization ion migration tube with tunable reactant ions. The ion migration tube contains a first ionization region, a second ionization region, and a third ionization region placed adjacent to each other from left to right. The first ionization region is for initial electron generation and ultraviolet light transmission path control; the second ionization region is for reactant ion generation; and the third ionization region is for the ionization of the sample to be tested. By rapidly switching the concentration of the dopant reagent in the first ionization region, different reactant ions can be rapidly switched and generated with high purity in the second ionization region. Utilizing the differences in the reaction selectivity of different reactant ions, highly selective detection of the sample to be tested can be achieved. Alternatively, by utilizing the differences in the product ions formed by different reactant ions and the sample to be tested, more one-dimensional information can be provided for the qualitative and quantitative analysis of the sample to be tested.

Description

Technical Field

[0001] This invention relates to the ion migration tube, a core component of ion mobility spectrometers, and more specifically, to a photoionization ion migration tube with real-time controllable reaction reagent ions. Background Technology

[0002] Photoionization is the most widely used ionization technique in the field of ion mobility spectrometry. In 1982, Lubman et al. successfully introduced photoionization technology into the field of ion mobility spectrometry using a laser as a light source (Anal. Chem. 1982, 54:1546). Subsequently, Hill and Eiceman et al. used small-volume commercially available vacuum ultraviolet lamps as photoionization sources for ion mobility spectrometry to detect volatile organic compounds (Anal. Chem. 1983, 55:1761; Anal. Chem. 1986, 58:2142). In 1997, Hans-Rudiger et al. (US5968837) disclosed a reagent-doped photoionization ion mobility spectrometry technique, realizing the detection of positive and negative polarity targets. In 2013, Cheng Shasha et al. discovered that reagent-doped photoionization ion mobility spectrometry, in negative ion mode, simultaneously contains CO3. - With O2 - These two reagent ions (Anal. Chem. 2013, 85:319). In 2014, Cheng Shasha et al. achieved, by switching the direction of the gas flow within the photoionization ion migration spectrum of the reagent-doped ions, the reagent ions in CO3 under negative ion mode. - With O2 - Rapid switching between different reagents is possible, but the purity of individual reagent ions is not high (Anal. Chem. 2014, 86:2687). In 2018, Jiang Dandan et al. designed a reagent-doped photoionization ion mobility spectrometry with a vertical lamp head structure to achieve rapid switching between different reagent ions, but the purity of individual reagent ions is not high (Anal. Chem. 2014, 86:2687). - The purity was increased to ~80%, achieving highly selective detection of sevoflurane and propofol in exhaled breath. However, the vertical lamp head structure does not utilize reagent ion extraction, resulting in insufficient reagent ion intensity. In 2019, Wang Weiguo et al. (CN112837989B) combined radio frequency discharge with an ultraviolet photoionization source to design an ionization source with switchable reagent ions. In 2020, Wang Xin et al. (CN114624326A) further introduced isopropanol into the reagent-doped photoionization ion migration spectrum, conveniently suppressing CO32-. - The generation of ions yielded O2 that met the experimental requirements. - Ion purity.

[0003] However, in the above-mentioned control methods, the generation of initial electrons in the photoionization source and the generation of reagent ions occur simultaneously in the same space, without separation in time and space. This is the main reason for the low purity of reagent ions and slow switching speed. Summary of the Invention

[0004] This invention discloses a photoionization ion migration tube with tunable reactant ions. By sequentially arranging a first ionization region, a second ionization region, and a third ionization region from left to right within the ion migration tube, the generation of initial electrons, the formation of reactant ions, and the ionization of the sample to be tested are completed sequentially in independent spaces. The first ionization region can rapidly and efficiently change the optical path of ultraviolet light transmission, thereby controlling the generation of high-purity single reactant ions in the second ionization region. By utilizing the reaction selectivity differences of different reactant ions, highly selective detection of the sample to be tested can be achieved, or the differences in product ions formed by different reactant ions and the sample to be tested can be utilized to provide more one-dimensional information support for the qualitative and quantitative analysis of the sample to be tested.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A photoionization ion migration tube with tunable reaction reagent ions is provided. The ion migration tube consists of an ion source, a first ionization region, a second ionization region, a third ionization region, an ion gate, a migration region, and an ion receiving electrode arranged coaxially from left to right. The first ionization region, the second ionization region, the third ionization region, and the migration region are all cylindrical bodies formed by alternating coaxial stacking of annular electrodes and annular insulators from left to right.

[0007] The ion source is any light source capable of generating ultraviolet light of any wavelength from 50 to 124 nm, and the light source outputs ultraviolet light along the direction from the ion source to the ion receiving electrode.

[0008] The first ionization region is the initial electron generation and ultraviolet light transmission optical path control region. It is filled with a control gas carrying doped reagents. On the one hand, the doped reagents can absorb the ultraviolet light output from the ion source, undergo photoionization, and generate electrons. On the other hand, by changing the concentration of the doped reagents, the distance that the ultraviolet light output from the ion source can be transmitted along the axial direction of the ion migration tube can be controlled. The control gas neither captures electrons nor interacts with ultraviolet light to generate ions.

[0009] The second ionization region is the region where reactant ions are generated. It is filled with reactant gas. When there is no ultraviolet light irradiation, the gaseous components of the reactant gas can directly capture electrons generated in the first ionization region to form reactant ions. When irradiated with ultraviolet light, the gaseous components of the reactant gas can absorb ultraviolet light and undergo photochemical reactions to generate new gaseous components. These new gaseous components can capture electrons generated in the first ionization region to form new reactant ions.

[0010] The third ionization region is the ionization region of the sample to be tested. It is filled with sample gas carrying the sample to be tested. The sample to be tested in the sample gas reacts with the reagent ions generated in the second ionization region to generate product ions.

[0011] The control gas is nitrogen, and the dopant is acetone, the concentration of which can be continuously adjusted between 0.1 and 10000 ppm. The reaction gas is purified air filtered through one or more of 13X molecular sieve, silica gel and activated carbon. The sample gas is purified air carrying the sample to be tested.

[0012] When the acetone concentration in the first ionization region exceeds 6000 ppm, the distance the ultraviolet light output from the ion source travels along the axial direction of the ion migration tube is less than the axial length of the first ionization region. Therefore, the ultraviolet light cannot enter the second ionization region. Electrons generated in the first ionization region, driven by the migration electric field, enter the second ionization region and are captured by oxygen molecules (O2) to generate O2. - Ions, O2 - Ions enter the third ionization region under the drive of the migration electric field, and undergo ion-molecule reaction with the molecules of the sample to generate product ions of the sample.

[0013] When the acetone concentration in the first ionization region is less than 3000 ppm, the distance that the ultraviolet light output from the ion source travels along the axial direction of the ion migration tube is greater than the axial length of the first ionization region. Electrons generated in the first ionization region, driven by the migration electric field, enter the second ionization region along with the ultraviolet light. In the second ionization region, oxygen molecules (O2) absorb ultraviolet light and undergo a photochemical reaction to generate ozone molecules (O3). O3 captures electrons to generate ozone. - Ions, O3 - The ions further react with carbon dioxide (CO2) in the purified air to produce CO3. - Ions, CO3 - Ions enter the third ionization region under the drive of the migration electric field, and undergo ion-molecule reaction with the molecules of the sample to generate product ions of the sample.

[0014] The inner diameters of the first, second, and third ionization regions increase sequentially. A first air inlet is provided on the side wall of the first ionization region near the ion source. A second air inlet is provided on the side wall of the second ionization region near the first ionization region. A third air inlet is provided on the side wall of the third ionization region near the second ionization region. An air outlet is provided on the side wall near the ion gate. A fourth air inlet is provided on the side wall of the migration region near the ion receiving electrode.

[0015] When the ion migration tube is working, one drift gas enters the migration region through the fourth inlet and then flows into the third ionization region through the ion gate; one modulation gas enters through the first inlet and fills the first ionization region, then flows into the second ionization region; one reaction gas enters through the second inlet into the second ionization region, mixes with the modulation gas flowing in from the first ionization region, and then flows into the third ionization region; one sample gas enters through the third inlet into the third ionization region, mixes with the gas flowing in from the second ionization region and the ion gate, and then flows out of the ion migration tube through the outlet; ions in the third ionization region are pulsedly injected into the migration region under the action of the periodically opening ion gate. Ions with different ion mobilities K are separated from each other under the action of the migration electric field and reach the ion receiving electrode one after another to form a spectrum of signal intensity corresponding to migration time;

[0016] The air purifier purifies the air;

[0017] Furthermore, by rapidly switching the acetone concentration in the modulating gas between greater than 6000 ppm and less than 3000 ppm, and utilizing the difference in reaction selectivity of different reagent ions, highly selective detection of the sample can be achieved. Alternatively, by utilizing the difference in product ions formed by different reagent ions and the sample, more one-dimensional information can be provided for the qualitative and quantitative analysis of the sample.

[0018] This invention discloses a photoionization ion migration tube with tunable reactant ions. The ion migration tube contains a first ionization region, a second ionization region, and a third ionization region placed adjacent to each other from left to right. The first ionization region is for initial electron generation and ultraviolet light transmission path control. Initial electrons are generated by the photoionization mechanism of the doped reagent absorbing ultraviolet light, and the transmission path of ultraviolet light along the axial direction of the ion migration tube is controlled to determine whether the ultraviolet light enters the second ionization region. The second ionization region is for reactant ion generation. When no ultraviolet light enters, the reactant gas directly captures electrons to generate reactant ions. When ultraviolet light enters, the reactant gas absorbs ultraviolet light and undergoes a photochemical reaction to generate new gas components, which then capture electrons to generate new reactant ions. The third ionization region is for the ionization of the sample to be tested. The sample to be tested undergoes an ion-molecule reaction with the reactant ions from the second ionization region to generate product ions. By rapidly switching the concentration of dopant reagents in the first ionization region, different reagent ions can be quickly switched and generated with high purity in the second ionization region. By utilizing the difference in reaction selectivity of different reagent ions, highly selective detection of the sample can be achieved. Alternatively, by utilizing the difference in product ions formed by different reagent ions and the sample, more one-dimensional information can be provided for the qualitative and quantitative analysis of the sample.

[0019] The advantages of this invention are:

[0020] The photoionization ion migration tube with tunable reaction reagent ions disclosed in this invention separates the generation of initial electrons, the generation of reaction reagent ions, and the ionization of the sample to be tested in time and space. By utilizing the mechanism of photoionization caused by the absorption of ultraviolet light by the doped reagent, it can achieve rapid switching and high-purity generation of different reaction reagent ions. By utilizing the reaction selectivity differences of different reaction reagent ions, it can achieve high-selectivity detection of the sample to be tested. Alternatively, by utilizing the differences in product ions formed by different reaction reagent ions and the sample to be tested, it can provide more one-dimensional information support for the qualitative and quantitative analysis of the sample to be tested.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings: Attached Figure Description

[0022] Figure 1 This is a structural diagram of the photoionization ion migration tube with tunable reactive reagent ions disclosed in this invention.

[0023] Wherein: 1. Ion source; 2. First ionization region; 3. Second ionization region; 4. Third ionization region; 5. Ion gate; 6. Migration region; 7. Ion receiving electrode; 8. First gas inlet (drift gas inlet); 9. Third gas inlet (sample gas inlet); 10. Second gas inlet (reaction gas inlet); 11. First gas inlet (modulation gas inlet); 12. Gas outlet;

[0024] Figure 2 The ion migration spectra related to the ions of the reaction reagents were obtained when the acetone concentration in the modulating gas was 500 ppm and 7000 ppm, and the sample gas was only purified air.

[0025] Figure 3 Ion migration spectra for detecting 200 μg / mL lactic acid headspace vapor using different reaction reagents. Detailed Implementation

[0026] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way. The invention will now be described in further detail with reference to the accompanying drawings.

[0027] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0028] Example 1

[0029] The photoionization ion migration tube with tunable reaction reagent ions disclosed in this invention, such as... Figure 1 As shown. Ion source 1 is a Kr VUV lamp with an output wavelength of 117nm (photon energy 10.6eV); the first ionization region 2 has an inner diameter of 12mm and an axial length of 30mm; the second ionization region 3 has an inner diameter of 16mm and an axial length of 20mm; the third ionization region 4 has an inner diameter of 22mm and an axial length of 20mm; the ion gate is a Bradbury-Nielsen type ion gate, consisting of two sets of coplanar metal grids with a wire diameter of 0.05mm and a wire spacing of 0.5mm; the migration region has an inner diameter of 22mm and an axial length of 70mm; the ion acceptor is a Faraday disk with a diameter of 7mm and a thickness of 0.5mm. During operation, a uniform electric field with an intensity of 450 V / cm is used inside the ion migration tube. One path of nitrogen gas carrying acetone is used as a modulation gas and enters the ion migration tube through modulation gas inlet 11 at a flow rate of 50 mL / min. The total acetone concentration in the modulation gas can be rapidly switched between 500 ppm and 7000 ppm with a switching time of less than 0.5 seconds. Another path of purified air, filtered through 13X molecular sieve, silica gel, and activated carbon, is used as a reaction gas and enters the ion migration tube through reaction gas inlet 10 at a flow rate of 100 mL / min. A third path of purified air is used as a sample gas and enters the ion migration tube through sample gas inlet 9 at a flow rate of 100 mL / min. Finally, a fourth path of purified air is used as a bleaching gas and enters the ion migration tube through bleaching gas inlet 8 at a flow rate of 200 mL / min.

[0030] Figure 2 The diagram shows ion mobility spectra related to the reactant ions obtained by varying the acetone concentration in the modulating gas when the sample gas is only purified air. When the acetone concentration in the modulating gas is 7000 ppm, only a single ion peak is observed in the ion mobility spectrum, its composition being O2. - Ions, as shown in spectrum a; when the acetone concentration in the modulating gas is 500 ppm, only a single ion peak is observed in the ion mobility spectrum, its composition being CO3. - The ions are shown in spectrum b. Experimental results show that the time required for switching between the two reagent ions is consistent with the time required for switching the acetone concentration in the modulating gas, which is less than 0.5 seconds.

[0031] Example 2

[0032] Based on the ion migration tube disclosed in Example 1, the response spectrum of a lactic acid sample was tested under the reaction reagent ion switching mode. During the experiment, 10 μL of an aqueous solution of 200 μg / mL lactic acid was dropped onto the thermal desorption sample introduction cloth and then fed into a thermal desorption sampler at 150°C. Purified air was introduced into the thermal desorption sampler, carrying lactic acid vapor which entered the ion migration tube through sample gas inlet 9 for sample detection.

[0033] When the acetone concentration in the modulated gas is 7000 ppm, only O2 is generated in the second ionization zone 3. - The ion reacts with lactic acid to produce two product ions with migration times of 3.50 ms and 4.51 ms, respectively, representing the monomeric and dimer ion peaks of lactic acid. Figure 3 As shown in spectrum a; when the acetone concentration in the modulating gas is 500 ppm, only CO3 is produced in the second ionization region 3. - The ion reacts with lactic acid to produce multiple product ions with migration times of 3.47 ms, 3.58 ms, 4.13 ms, and 4.43 ms, respectively. The spectrum is very complex, as shown in the figure. Figure 3 As shown in spectrum b; comparing spectrum a and spectrum b, it is clear that when the reagent ion is O2... - When ions are present, the product ion peaks of lactic acid are easier to identify and are more conducive to quantitative analysis.

Claims

1. A photoionization ion migration tube with tunable reaction reagent ions, wherein the ion migration tube comprises an ion source (1), a first ionization region (2), a second ionization region (3), a third ionization region (4), an ion gate (5), a migration region (6), and an ion receiving electrode (7) arranged coaxially from left to right, wherein the first ionization region (2), the second ionization region (3), the third ionization region (4), and the migration region (6) are all cylindrical bodies formed by alternating coaxial stacking of annular electrodes and annular insulators from left to right, characterized in that: The ion source (1) is any light source capable of generating ultraviolet light of any wavelength from 50 to 124 nm, and the light source outputs ultraviolet light along the direction from the ion source (1) to the ion receiving electrode (7); The first ionization region (2) is the initial electron generation and ultraviolet light transmission optical path control region. Its interior is filled with a control gas carrying doped reagents. On the one hand, the doped reagents can absorb the ultraviolet light output from the ion source (1) to generate photoionization and produce electrons. On the other hand, by changing the concentration of the doped reagents, the distance that the ultraviolet light output from the ion source (1) is transmitted along the axial direction of the ion migration tube can be controlled. The control gas neither captures electrons nor interacts with ultraviolet light to generate ions; The second ionization region (3) is the region for generating reactant ions. It is filled with reactant gas. When there is no ultraviolet light irradiation, the gaseous components of the reactant gas can directly capture electrons generated in the first ionization region (2) to form reactant ions. When irradiated with ultraviolet light, the gaseous components of the reactant gas can absorb ultraviolet light and undergo photochemical reaction to generate new gaseous components. These new gaseous components can capture electrons generated in the first ionization region (2) to form new reactant ions. The third ionization region (4) is the ionization region of the sample to be tested. Its interior is filled with sample gas carrying the sample to be tested. The sample to be tested in the sample gas undergoes an ion-molecule reaction with the reaction reagent ions generated in the second ionization region (3) to generate product ions.

2. The ion migration tube according to claim 1, characterized in that: The control gas is nitrogen, and the dopant is acetone, the concentration of which can be continuously adjusted between 0.1 and 10000 ppm. The reaction gas is purified air filtered through one or more of 13X molecular sieve, silica gel and activated carbon. The sample gas is purified air carrying the sample to be tested. When the acetone concentration in the first ionization region (2) is greater than 6000 ppm, the distance that the ultraviolet light output from the ion source (1) travels along the axial direction of the ion migration tube is less than the axial length of the first ionization region (2). The ultraviolet light cannot enter the second ionization region (3). Under the drive of the migration electric field, the electrons generated in the first ionization region (2) enter the second ionization region (3) and are captured by the oxygen molecules O2 in the second ionization region (3) to generate O2. - Ions, O2 - Ions enter the third ionization region (4) under the drive of the migration electric field, and react with the molecules of the sample to be tested to generate the product ions of the sample to be tested; When the acetone concentration in the first ionization region (2) is less than 3000 ppm, the distance that the ultraviolet light output from the ion source (1) travels along the axial direction of the ion migration tube is greater than the axial length of the first ionization region (2). Electrons generated in the first ionization region (2) enter the second ionization region (3) together with the ultraviolet light under the drive of the migration electric field. In the second ionization region (3), oxygen molecules O2 absorb ultraviolet light and undergo photochemical reactions to generate ozone molecules O3. O3 captures electrons to generate O3. - Ions, O3 - The ions further react with carbon dioxide (CO2) in the purified air to produce CO3. - Ions, CO3 - Ions enter the third ionization region (4) under the drive of the migration electric field, and react with the molecules of the sample to be tested to generate the product ions of the sample to be tested.

3. The ion migration tube according to claim 1 or 2, characterized in that: The inner diameters of the first ionization region (2), the second ionization region (3), and the third ionization region (4) increase sequentially; a first air inlet (11) is provided on the side wall of the first ionization region (2) near the ion source (1); a second air inlet (10) is provided on the side wall of the second ionization region (3) near the first ionization region (2); a third air inlet (9) is provided on the side wall of the third ionization region (4) near the second ionization region (3), and an air outlet (12) is provided on the side wall near the ion gate (5); a fourth air inlet (8) is provided on the side wall of the migration region (6) near the ion receiving electrode (7). When the ion migration tube is working, one drift gas enters the migration zone (6) through the fourth inlet (8), and then flows into the third ionization zone (4) through the ion gate (5); one modulation gas enters and fills the first ionization zone (2) through the first inlet (11), and then flows into the second ionization zone (3); one reaction gas enters the second ionization zone (3) through the second inlet (10), mixes with the modulation gas flowing in through the first ionization zone (2), and then flows into the third ionization zone (4); one sample gas... The gas enters the third ionization region (4) through the third inlet (9), mixes with the gas flowing in through the second ionization region (3) and the ion gate (5), and flows out of the ion migration tube through the outlet (12). The ions in the third ionization region (4) are pulsed into the migration region (6) under the action of the periodically opened ion gate (5). Ions with different ion mobility K are separated from each other under the action of the migration electric field and reach the ion receiving electrode (7) one after another to form a spectrum of signal intensity corresponding to migration time.

4. The ion migration tube according to claim 3, characterized in that: The air purifier purifies the air; Furthermore, by rapidly switching the acetone concentration in the modulating gas between greater than 6000 ppm and less than 3000 ppm, and utilizing the difference in reaction selectivity of different reagent ions, highly selective detection of the sample can be achieved. Alternatively, by utilizing the difference in product ions formed by different reagent ions and the sample, more one-dimensional information can be provided for the qualitative and quantitative analysis of the sample.

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