Photoionization ion mobility spectrometry for rapid switching of combined reagent ions and applications

Abstract

The present application relates to a kind of photoionization ion mobility spectrometry of fast switching combination reagent ion, including photoionization ion mobility spectrometry, reagent ion generation device, reagent molecule carrier gas is introduced to reagent molecule into the reaction zone of ion mobility spectrometry, different types of reagent ions can be obtained by switching different gas paths and reagent molecules in positive ion mode, and the reagent ions in conventional gas flow mode are mainly (C3H6O)2H + , after switching combination gas path device, new hydrate cluster reagent ion H3O (H2O) n + Is generated by the regulation of acetone and water reagent molecule, and the reactivity is higher, the sensitivity of target detection is higher, so that by switching different gas paths, the high sensitivity and high selectivity detection of target compound can be realized, such as the detection of exhaled air ammonia and atmospheric ammonia in complex matrix background, and any sample pretreatment process is not needed.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry instruments, specifically relating to a photoionization ion mobility spectrometry that rapidly switches between combined reagent ions. By combining different reagent molecules under different gas flow modes, different reagent ions can be obtained, thereby enabling highly selective detection of substances with different proton affinity potentials in complex matrices and improving the selectivity and sensitivity of photoionization ion mobility spectrometry detection. Background Technology

[0002] Currently, the ionization sources for ion mobility spectrometry are mainly non-radioactive photoionization sources. Most direct photoionization methods have relatively low ionization efficiency, and some substances cannot be detected by direct photoionization. To address this issue, reagent-assisted photoionization (DA-APPI) can be introduced to improve the sensitivity and selectivity of sample detection. In DA-APPI, reagent molecules first generate sufficient reagent ions through direct photoionization, and then the sample molecules are ionized through a molecular-ion reaction between the reagent ions and the sample molecules. This converts photoionization into chemical ionization, thereby improving the ionization efficiency of sample molecules by 2-3 orders of magnitude. Since different reagent ions have different reaction characteristics, the required reagent ions for detecting different samples also vary.

[0003] To improve the yield of reagent ions, Cheng et al. developed a reagent molecule-assisted negative ion photoionization IMS (DANP-IMS) capable of rapidly switching reagent ions. By changing the airflow pattern inside the IMS, an O2 ion yield of 89% was obtained under unidirectional airflow. - A method and its application were studied to improve the selectivity of photoionization ion mobility spectra, achieving an ion yield of 88% under bidirectional gas flow. This was achieved through O2. - With CO3 - Switching between different wavelengths can improve the sensitivity of analytes and provide more information for the detection of sample molecules. Jiang et al. designed a side-mounted photoionization source in which the UV lamp is placed perpendicular to the migration tube, and all gases are discharged outside the migration tube through the outlet located at the front of the ionization source. This design not only reduces the ozone generation area but also increases the rate at which ozone is blown out of the ionization region, thereby limiting CO3 emissions. - This improves the yield and avoids the influence of exhaled CO2 on propofol detection. Currently, in order to detect substances with different electronegativity, the reagent ions used in positive ion mode are relatively limited, and different reagent ions have different selectivity and sensitivity to sample molecules. By switching between different reagent ions, high sensitivity and high selectivity detection of different substances can be achieved in positive ion mode. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a photoionization ion mobility spectrometry (PMI) with rapidly switching combined reagent ions and its applications. In positive ion mode, this PMI utilizes a photoionization reagent ion rapid switching device to switch different gas flow modes and combine different reagent molecules to obtain reagent ions (C3H6O2)H with different reaction characteristics. + and (H2O) n + Because different reagent ions have different reaction characteristics, they can react with analytes with different reaction characteristics, thereby achieving highly sensitive and selective detection of different target substances in complex matrices (such as ammonia, hazardous chemical hydrazine, and phthalic acid esters leaks in the atmosphere), and improving the sensitivity and selectivity of actual sample detection.

[0005] To achieve the above objectives, the present invention provides a photoionization ion mobility spectrum for rapidly switching combined reagent ions, comprising an ion migration tube, a reagent molecule headspace purge device 7 and a second reagent molecule headspace purge device 10, a two-position three-way solenoid valve 5, a water reagent molecule headspace purge generator 13, a vacuum sampling pump 20 and a three-way connector 24; the ion migration tube includes a photoionization source 21 and a Faraday disk receiving device 23 respectively arranged opposite to each other at the left and right ends, and an ion gate 22 located between the photoionization source 21 and the Faraday disk receiving device 23, the region between the photoionization source 21 and the ion gate 22 being the reaction region, and the region between the ion gate 22 and the Faraday disk receiving device 23 being the migration region;

[0006] An ion migration tube outlet 18 is located on the lower wall of the ion migration tube reaction region, near the photoionization source 21. The ion migration tube outlet 18 is connected to a sixth mass flow meter 19 and a vacuum sampling pump 20 via pipelines, and then vented (open to the atmosphere). A sample inlet 17 is located on the lower wall of the ion migration spectrum reaction region, near the ion gate 22. The sample inlet 17 is connected to the sampling port 15 via a sampling tube and a fourth mass flow meter 16 installed on the sampling tube. A first reagent molecule inlet 8 is located between the ion migration tube outlet 18 and the sample inlet 17.

[0007] A second reagent molecule inlet 11 is provided on the upper wall of the reaction zone of the ion migration tube near the photoionization source; a drift gas inlet 3 is provided above the Faraday disk receiving device 23 at the right end of the ion migration tube; one end of an air inlet pipe is connected to the drift gas inlet 3, and the other end is connected to the clean compressed air source 1 through the first mass flow meter 2.

[0008] One end of a clean compressed air pipeline 4 is connected to a clean compressed air source 1, and the other end is connected to the first port of a two-position three-way solenoid valve 5; the second port of the two-position three-way solenoid valve 5 is connected to the first port of a three-way connector 24 through a pipeline.

[0009] The reagent molecule headspace purge device 7 and the second reagent molecule headspace purge device 10 have the same structure, including a reagent bottle with an open top and a sealed container. The reagent bottle is filled with reagent molecules and placed inside the sealed container. An air inlet pipe and a reagent molecule outlet pipe are respectively arranged in the sealed container on two opposite sides of the reagent bottle. One end of the air inlet pipe of the reagent molecule headspace purge device 7 is located inside the sealed container, and the other end is connected to the third interface of the two-position three-way solenoid valve 5 through the fifth mass flow meter 6. One end of the reagent molecule outlet pipe is located inside the sealed container, and the other end is connected to the first reagent molecule inlet 8. One end of the air inlet pipe of the second reagent molecule headspace purge device 10 is located inside the sealed container, and the other end is connected to the second interface of the three-way connector 24 through the second mass flow meter 9. One end of the reagent molecule outlet pipe is located inside the sealed container, and the other end is connected to the second reagent molecule inlet 11.

[0010] The water reagent molecule headspace purge generator 13 is a water container, which is placed inside an electric heating wire heating device 14. One end of an air inlet pipe extends below the water surface in the water container, and the other end is connected to the third interface of the three-way connector 24 via a third mass flow meter 12. One end of an water reagent molecule pipe extends above the water surface in the water container, and the other end is connected to the first reagent molecule air inlet 8 of the ion migration tube.

[0011] Furthermore, the ion mobility spectrum is a photoionization ion mobility spectrum; the photoionization source 21 is a vacuum ultraviolet lamp.

[0012] Furthermore, the reagent molecules in the reagent molecule headspace purge device 7 and the second reagent molecule headspace purge device 10 are organic reagent molecules and / or inorganic reagent molecules, wherein the organic reagent molecules are either acetone or butanone, and the inorganic reagent molecules are water molecules. The reagent molecules are heated by the electric heating wire heating device 14, which causes the organic reagent molecule solvent and / or inorganic reagent molecule solvent in the headspace purge bottle to evaporate rapidly into gaseous form of reagent molecules.

[0013] Furthermore, the clean compressed air is air that has passed through a 13X molecular sieve and activated carbon filter in sequence.

[0014] An application of the above-mentioned rapid switching combination of reagent ions photoionization ion mobility spectrometry is achieved by changing the airflow pattern of reagent molecules by switching the interface of the two-position three-way solenoid valve 5, blowing different reagent molecules into the ion molecular reaction region of the ion mobility spectrometry, obtaining different reagent ions, thereby realizing high selectivity and high sensitivity detection of substances with high proton affinity in complex matrices.

[0015] Switch the two-position three-way solenoid valve 5 to the third interface. At this time, it is in the conventional reagent ion mode. In this mode, the airflow pattern for introducing reagent molecules is as follows: the compressed air in the clean compressed air source 1 is divided into two paths to enter the ion migration tube. The first path passes through the third interface of the two-position three-way solenoid valve 5, the fifth mass flow meter 6, and the reagent molecule headspace generator 7, and finally enters the reaction zone of the ion migration tube through the first reagent molecule inlet 8. The second path passes through the first mass flow meter 2 and then through the drift gas inlet 3 to be introduced into the migration zone of the ion migration tube in the form of drift gas. At the same time, the sampling pump 20 is started. Under the control of the sixth mass flow meter 19 and the fourth mass flow meter 16, the sample is sampled through the pipeline through the sample inlet 17 and sent to the reaction zone of the migration tube for detection.

[0016] Switching the two-position three-way solenoid valve 5 to the second interface activates the combined reagent ion mode. In this mode, the airflow pattern for introducing reagent molecules is as follows: Compressed air from the clean compressed air source 1 is divided into three paths entering the ion migration tube. The first path, after passing through the first mass flow meter 2, is introduced into the migration zone of the ion migration tube in the form of drift gas through the drift gas inlet 3. The second path passes through the second interface of the two-position three-way solenoid valve 5, the three-way connector 24, the second mass flow meter 9, the second reagent molecule headspace generator 10, and then enters the ion migration spectrum reaction zone through the second reagent molecule inlet 11. The third path passes through the second interface of the two-position three-way solenoid valve 5, the three-way connector 24, the third mass flow meter 12, the water reagent molecule headspace purge generator 13, and then enters the ion migration tube reaction zone through the first reagent molecule inlet 8. Simultaneously, the vacuum sampling pump 20 is started. Under the control of the sixth mass flow meter 19 and the fourth mass flow meter 16, the sample is sampled through the pipeline through the inlet 17 and sent to the migration tube reaction zone for detection.

[0017] Furthermore, the flow rate of the first mass flow meter 2 is 200-500 mL / min, the flow rate of the second mass flow meter 9 is 50-200 mL / min, and the flow rate of the third mass flow meter 12 is 100-300 mL / min.

[0018] The flow rate of the fourth mass flow meter 16 is 50-200 mL / min, the flow rate of the fifth mass flow meter 6 is 50-200 mL / min, the flow rate of the sixth mass flow meter 19 is 300-1100 mL / min, and the sampling flow rate is 50-200 mL / min.

[0019] Furthermore, in the conventional reagent ion mode, by introducing organic reagent molecules into the reaction region of the ion mobility spectrum, the molecular ion peak M of the organic reagent molecule can be obtained. + or MH + By switching to the combined reagent ion mode, and simultaneously introducing organic and inorganic reagent molecules into the ion molecule reaction region, the reagent ions can be rapidly switched to H2O. + This can improve the detection sensitivity of substances with high proton affinity and reduce the interference from low proton affinity matrices. The substances with high proton affinity include one or more of the following: ammonia, hydrazine (a hazardous chemical), and phthalates (plasticizers).

[0020] Furthermore, the photoionization ion mobility spectrometry provided by this invention, which allows for rapid switching of combined reagent ions, can not only be used for the detection of substances with high proton affinity in exhaled breath (such as ammonia), but also for the highly selective and sensitive detection of high proton affinity VOCs in indoor and ambient air (such as ammonia, hazardous chemical hydrazine, and phthalic acid ester leaks), thereby improving the selectivity and sensitivity of ion mobility spectrometry in complex matrix environments.

[0021] Compared with existing technologies, the advantages of this invention are as follows: By combining organic and inorganic solvents, not only can reagent ion peaks of organic solvents be obtained in the conventional organic solvent mode, enabling highly selective and wide-range quantitative detection of substances with high proton affinity, such as ammonia in the environment; furthermore, by switching the combined reagent mode, reagent ions of non-ionizing inorganic solvents, such as water, can be obtained, and highly sensitive quantitative detection of ammonia with high proton affinity can be achieved, increasing the detection limit by an order of magnitude. For different environmental monitoring application scenarios, by simply switching the combined reagent mode, highly sensitive early warning monitoring of leaks of extremely low concentrations of ammonia or hazardous chemicals such as hydrazine and phthalates can be achieved, as well as accurate quantitative detection of high concentrations of ammonia in the environment over a wide range. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a photoionization combined reagent molecule rapid switching reagent ion device of the present invention;

[0023] Among them, 1 is a clean compressed air source, 2 is the first mass flow meter, 3 is the drift gas inlet, 4 is the clean compressed air pipeline, 5 is a two-position three-way solenoid valve, 6 is the fifth mass flow meter, 7 is the reagent molecule headspace purge device, 8 is the first reagent molecule air inlet, 9 is the second mass flow meter, 10 is the second reagent molecule headspace purge device, 11 is the second reagent molecule air inlet, 12 is the third mass flow meter, 13 is the water reagent molecule headspace purge generator, 14 is the electric heating wire heating device, 15 is the sampling port, 16 is the fourth mass flow meter, 17 is the sample air inlet, 18 is the air outlet, 19 is the sixth mass flow meter, 20 is the vacuum sampling pump, 21 is the photoionization source, 22 is the ion gate, 23 is the Faraday disk receiving device, and 24 is the three-way connector.

[0024] Figure 2 Ion migration spectra of ammonia in indoor air were detected under conventional reagent ion mode and switched combined reagent ion mode.

[0025] Figure 3 Quantitative curves of ammonia under conventional reagent ion mode and under switched combined reagent ion mode. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 As shown, the present invention provides a photoionization ion mobility spectrum for rapidly switching combined reagent ions, including an ion migration tube, a reagent molecule headspace purge device 7 and a second reagent molecule headspace purge device 10, a two-position three-way solenoid valve 5, a water reagent molecule headspace purge generator 13, a vacuum sampling pump 20 and a three-way connector 24; the ion migration tube includes a photoionization source 21 and a Faraday disk receiving device 23 respectively arranged opposite to each other at the left and right ends, and an ion gate 22 located between the photoionization source 21 and the Faraday disk receiving device 23. The region between the photoionization source 21 and the ion gate 22 is the reaction region, and the region between the ion gate 22 and the Faraday disk receiving device 23 is the migration region;

[0028] An ion migration tube outlet 18 is located on the lower wall of the ion migration tube reaction region, near the photoionization source 21. The ion migration tube outlet 18 is connected to a sixth mass flow meter 19 and a vacuum sampling pump 20 via pipelines, and then vented (open to the atmosphere). A sample inlet 17 is located on the lower wall of the ion migration spectrum reaction region, near the ion gate 22. The sample inlet 17 is connected to the sampling port 15 via a sampling tube and a fourth mass flow meter 16 installed on the sampling tube. A first reagent molecule inlet 8 is located between the ion migration tube outlet 18 and the sample inlet 17.

[0029] A second reagent molecule inlet 11 is provided on the upper wall of the reaction zone of the ion migration tube near the photoionization source; a drift gas inlet 3 is provided above the Faraday disk receiving device 23 at the right end of the ion migration tube; one end of an air inlet pipe is connected to the drift gas inlet 3, and the other end is connected to the clean compressed air source 1 through the first mass flow meter 2.

[0030] One end of a clean compressed air pipeline 4 is connected to a clean compressed air source 1, and the other end is connected to the first port of a two-position three-way solenoid valve 5; the second port of the two-position three-way solenoid valve 5 is connected to the first port of a three-way connector 24 through a pipeline.

[0031] The reagent molecule headspace purge device 7 and the second reagent molecule headspace purge device 10 have the same structural configuration, including a reagent bottle with an open top and a sealed container. Reagent molecules are filled in the reagent bottle, which is placed inside the sealed container. An air inlet pipe and a reagent molecule outlet pipe are respectively installed in the sealed container on two opposite sides of the reagent bottle. One end of the air inlet pipe of the reagent molecule headspace purge device 7 is located inside the sealed container, and the other end is connected to the third interface of the two-position three-way solenoid valve 5 via a fifth mass flow meter 6. One end of the reagent molecule outlet pipe is located inside the sealed container, and the other end is connected to the first reagent molecule inlet 8. The air inlet pipe of the second reagent molecule headspace purge device 10... One end of the gas inlet pipe is located inside a sealed container, and the other end is connected to the second interface of the three-way connector 24 via the second mass flow meter 9; one end of the reagent molecule outlet pipe is located inside a sealed container, and the other end is connected to the second reagent molecule inlet 11; the water reagent molecule headspace purge generator 13 is a water container, which is placed inside an electric heating wire heating device 14; one end of an air inlet pipe extends below the water surface in the water container, and the other end is connected to the third interface of the three-way connector 24 via the third mass flow meter 12; one end of an water reagent molecule pipe extends above the water surface in the water container, and the other end is connected to the first reagent molecule inlet 8 of the ion migration tube.

[0032] The ion mobility spectrum is a photoionization ion mobility spectrum; the photoionization source 21 is a vacuum ultraviolet lamp; the reagent molecules in the reagent molecule headspace purge device 7 and the second reagent molecule headspace purge device 10 are acetone reagents; and the clean compressed air is air that has been filtered through a 13X molecular sieve and activated carbon in sequence.

[0033] The photoionization ion mobility spectrometry of rapidly switching combined reagent ions provided by the present invention was used to detect indoor air under conventional reagent ion mode (see Example 1) and switched combined reagent ion mode (see Example 2).

[0034] Example 1

[0035] Switching the two-position three-way solenoid valve (5) to the third interface, the ion mobility spectrum enters the conventional reagent ion mode. The compressed air in the clean compressed air source 1 is divided into two paths. The first path passes through the third interface of the two-position three-way solenoid valve 5, the fifth mass flow meter 6, and the reagent molecule headspace generator 7, and finally enters the ion mobility spectrum reaction zone through the first reagent molecule inlet 8 of the migration zone. The reagent molecule in 7 is acetone with a concentration of 20 ppm. The second path passes through the first mass flow meter 2 and then through the drift gas inlet 3. The air is introduced into the migration zone of the ion migration tube in the form of drift gas. Simultaneously, the sampling pump 20 is activated. Under the control of the sixth mass flow meter 19 and the fourth mass flow meter 16, air from the test chamber is sampled through the sample inlet 17 and transported to the migration spectrum reaction zone. The flow rate of the fifth mass flow meter 6 is 100 mL / min, the first mass flow meter 2 is 300 mL / min, the sixth mass flow meter 19 is 450 mL / min, the fourth mass flow meter 16 is 50 mL / min, and the sampling flow rate is 50 mL / min. Using conventional IMS mode, the photoionization reagent ions are obtained as M. + / MH + The ion migration spectrum was detected, such as Figure 2 As shown, the reagent ion Ac2H is obtained by hydrogenation of the acetone dimer corresponding to the acetone reagent molecule. + That is, (C3H6O)2H + The migration time was 4.52 ms, and the reduced mobility was 1.88 cm. 2 V -1 s -1 The signal strength was 2800mV. Further analysis of the ambient air revealed that the ammonia product ions were protonated clusters of ammonia and acetone, with a migration time of 4.22ms and K0 = 2.01 cm⁻¹. 2 V -1 s -1 Although the proton affinity of ammonia is 853.6 kJ / mol, which is higher than that of acetone reagent ions (PA = 812 kJ / mol), the signal intensity is only 100 mV, and no other obvious product ion peaks were detected.

[0036] Example 2

[0037] Switching the two-position three-way solenoid valve (5) to the second interface, the ion mobility spectrum enters the switching combination reagent ion mode. The compressed air in the clean compressed air source 1 is mainly divided into 3 paths. The first path is introduced into the migration area of ​​the ion mobility spectrum in the form of drift gas through the drift gas inlet 3 after passing through the first mass flow meter 2. The second path passes through the second interface of the two-position three-way solenoid valve 5, the three-way connector 24, the second mass flow meter 9, and the second reagent molecule headspace purge device 10, and then enters the ion mobility spectrum reaction area through the air inlet 11. The reagent molecule in the second reagent molecule headspace purge device 10 is acetone, and the acetone concentration is 20ppm. The third path passes through the second interface of the two-position three-way solenoid valve 5, the three-way connector 24, and the third mass flow meter 10. 2. Water reagent molecules enter the migration tube reaction zone through the first reagent molecule inlet 8 after being generated by the headspace purge device 13. Simultaneously, the vacuum sampling pump 20 is started. Under the control of the sixth mass flow meter 19 and the fourth mass flow meter 16, the ambient air to be tested is sampled into the migration tube reaction zone through the sample inlet 17 via the pipeline. The flow rate of the first mass flow meter 2 is 300 mL / min, the flow rate of the second mass flow meter 9 is 100 mL / min, the flow rate of the third mass flow meter 12 is 100 mL / min, the flow rate of the sixth mass flow meter 19 is 550 mL / min, the flow rate of the fourth mass flow meter 16 is 50 mL / min, and the sampling flow rate is 50 mL / min.

[0038] IMS employing switching reagent ions utilizes a combination of reagent molecules. Although water has a relatively high ionization energy and is not easily ionized, acetone, with an ionization energy of 9.70 eV, can be significantly photoionized, increasing photoionization efficiency and generating more reagent ions. High humidity water vapor then converts the proton-exchanged acetone dimer ions into hydrated H+ ions. + (H2O) n Water has a proton affinity of PA = 692 kJ / mol, which allows it to react with more substances with low proton affinity, thus enabling highly sensitive detection of more substances. Moreover, since both water and ammonia are polar inorganic compounds and have similar structures, the conversion efficiency of ammonia in the reaction with water and ions is higher, making the detection of ammonia more sensitive.

[0039] The reagent ion is H3O + ∙(H2O) n At that time, its ion migration spectrum was obtained, such as Figure 2 As shown, the reagent ions were successfully converted from (C3H6O)2H + Switch to H3O + ∙(H2O) n The migration time was 3.24 ms, and the reduced mobility was 2.33 cm. 2 V -1 s -1After switching modes, the product ions of ammonia are protonated clusters of ammonia and water, with a reduced mobility of K0 = 2.90 cm⁻¹. 2 V -1 s -1 With a migration time of 2.64 ms and a signal strength of 582 mV, it achieves highly sensitive detection of low concentrations of ppb ammonia in the environment.

[0040] Ammonia was quantified in both standard and switching modes. In standard mode, standard ammonia samples of different concentrations were detected at concentrations of 99 ppbv, 196 ppb, 291 ppb, 385 ppb, 476 ppb, 600 ppb, 700 ppb, 800 ppb, and 900 ppb, with signal intensities of 256.8 mV, 361.3 mV, 456.7 mV, 566.5 mV, 669.1 mV, 789.8 mV, 894.2 mV, 982.3 mV, and 1011.2 mV, respectively. A quantitative curve for ammonia in standard mode was obtained through linear fitting, as shown below. Figure 3 As shown by the dashed line, y = 1.1x + 158.1, R 2 =0.99, where x is the concentration of the standard ammonia sample, y is the detection signal intensity, and R 2 This indicates the goodness of fit of the quantitative curve, with a linear range of 30-800 ppbv, a minimum detection limit (LOD) of 6.2 ppbv, and a sensitivity of 1.3 mV / ppbv.

[0041] In the switching mode, different low-concentration standard ammonia samples were tested. The concentrations of the standard ammonia samples were 2.78 ppbv, 6.02 ppbv, 9.03 ppbv, 12.04 ppbv, 15.05 ppbv, 21.07 ppbv, 27.09 ppbv, and 48.16 ppbv, with signal intensities of 51.62 mV, 198.24 mV, 366.22 mV, 545.98 mV, 677.18 mV, 914.88 mV, 1143.19 mV, and 1788.19 mV, respectively. Figure 3 (Solid line) The quantitative curve of ammonia is y = 45.3x - 46.5, R 2 =0.99, where x is the concentration of the standard ammonia sample, y is the detection signal intensity, and R 2 This indicates the goodness of fit of the quantitative curve, with a linear range of 2-28 ppbv, a minimum detection limit (LOD) of 0.9 ppbv, and a sensitivity of 45.4 mV / ppbv, approximately 35 times that of the conventional mode. The detection limit is improved by an order of magnitude. The reagent ion (C3H6O)2H... + With reagent ion H +(H2O) n The rapid switching enables the detection of ammonia in both high-selectivity and high-sensitivity modes, achieving online monitoring of ammonia in the atmosphere.

Claims

1. A photoionization ion mobility spectrometry method for rapidly switching combined reagent ions, characterized in that, It includes an ion migration tube, a reagent molecule headspace purge device (7), a second reagent molecule headspace purge device (10), a two-position three-way solenoid valve (5), a water reagent molecule headspace purge generator (13), a vacuum sampling pump (20), and a three-way connector (24). The ion migration tube includes a photoionization source (21) and a Faraday disk receiving device (23) respectively arranged opposite to each other at the left and right ends, and an ion gate (22) located between the photoionization source (21) and the Faraday disk receiving device (23). The area between the photoionization source (21) and the ion gate (22) is the reaction area, and the area between the ion gate (22) and the Faraday disk receiving device (23) is the migration area. An ion migration tube outlet (18) is provided on the lower wall of the ion migration tube reaction zone near the photoionization source (21). The ion migration tube outlet (18) is connected to the sixth mass flow meter (19) and the sampling pump (20) in sequence through pipelines and is connected to the atmosphere. A sample inlet (17) is provided on the lower wall of the ion migration spectrum reaction zone near the ion gate (22). The sample inlet (17) is connected to the sampling port (15) through the sampling tube and the fourth mass flow meter (16) set on the sampling tube. A first reagent molecule inlet (8) is provided between the ion migration tube outlet (18) and the sample inlet (17). A second reagent molecule inlet (11) is provided on the upper wall of the reaction zone of the ion migration tube near the photoionization source. A drift gas inlet (3) is provided above the Faraday disk receiving device (23) on the right side of the ion migration tube. One end of an air inlet pipe is connected to the drift gas inlet (3), and the other end is connected to a clean compressed air source (1) through a first mass flow meter (2). One end of a clean compressed air pipeline (4) is connected to a clean compressed air source (1), and the other end is connected to the first port of a two-position three-way solenoid valve (5); the second port of the two-position three-way solenoid valve (5) is connected to the first port of a three-way connector (24) through a pipeline. The headspace purge device (7) for reagent molecules and the headspace purge device (10) for reagent molecules have the same structure. They include a reagent bottle with an open top and a sealed container. The reagent bottle is filled with reagent molecules and placed in the sealed container. An air inlet pipe and a reagent molecule outlet pipe are respectively provided in the sealed containers on two opposite sides of the reagent bottle. One end of the air inlet pipe of the reagent molecule headspace purge device (7) is located inside the sealed container, and the other end is connected to the third interface of the two-position three-way solenoid valve (5) through the fifth mass flow meter (6); one end of the reagent molecule outlet pipe is located inside the sealed container, and the other end is connected to the first reagent molecule inlet (8). One end of the air inlet pipe of the second reagent molecule headspace purge device (10) is located inside the sealed container, and the other end is connected to the second interface of the three-way connector (24) through the second mass flow meter (9); one end of the reagent molecule outlet pipe is located inside the sealed container, and the other end is connected to the second reagent molecule inlet (11). The water reagent molecule headspace purge generator (13) is a water container. The water container is placed in an electric heating wire heating device (14). One end of an air inlet pipe extends below the water surface in the water container, and the other end is connected to the third interface of the three-way connector (24) via the third mass flow meter (12). One end of a water reagent molecule pipe extends above the water surface in the water container, and the other end is connected to the first reagent molecule air inlet (8) of the ion migration tube. The airflow pattern of reagent molecules introduced into the ion migration tube is changed by switching the interface of the two-position three-way solenoid valve (5).

2. The photoionization ion mobility spectrometry of rapidly switching combined reagent ions according to claim 1, characterized in that: The ion mobility spectrum is a photoionization ion mobility spectrum; the photoionization source (21) is a vacuum ultraviolet lamp.

3. The photoionization ion mobility spectrometry of rapidly switching combined reagent ions according to claim 1, characterized in that: The reagent molecules in the headspace purge device (7) and the second headspace purge device (10) include organic solvents and / or inorganic solvents, wherein the organic solvent is one of acetone or butanone, and the inorganic solvent is water molecules. The reagent molecules are heated so that the organic and inorganic reagent molecules in the headspace purge bottle evaporate rapidly into gaseous form.

4. The photoionization ion mobility spectrometry of rapidly switching combined reagent ions according to claim 1, characterized in that: The clean compressed air is air that has passed through a 13X molecular sieve and activated carbon filter in sequence.

5. An application of the ion mobility spectrometry described in any one of claims 1-4, characterized in that: By switching the interface of the two-position three-way solenoid valve to change the airflow pattern of reagent molecules, different reagent molecules are purged into the ion molecular reaction region of the ion mobility spectrum, and different reagent ions are obtained, thereby achieving high selectivity and high sensitivity detection of substances with high proton affinity in complex matrices.

6. The application according to claim 5, characterized in that: When the two-position three-way solenoid valve (5) is connected to the third interface, it is in the conventional reagent ion mode. In this mode, the airflow pattern of the reagent molecules is as follows: the compressed air in the clean compressed air source (1) is divided into two paths to enter the ion migration tube. The first path passes through the third interface of the two-position three-way solenoid valve (5), the fifth mass flow meter (6), and the reagent molecule headspace purge device (7) in sequence, and finally enters the reaction zone of the ion migration tube through the first reagent molecule inlet (8); the second path passes through the first mass flow meter (2) and then through the drift gas inlet (3) to be introduced into the migration zone of the ion migration tube in the form of drift gas. At the same time, the sampling pump (20) is started. Under the control of the sixth mass flow meter (19) and the fourth mass flow meter (16), the sample is sampled into the reaction zone of the migration tube through the sample inlet (17) via the pipeline. When the two-position three-way solenoid valve (5) is connected to the second interface, the combined reagent ion mode is switched. In this mode, the airflow mode introduced by the reagent molecules is as follows: the compressed air in the clean compressed air source (1) is divided into three paths to enter the ion migration tube. The first path is introduced into the migration area of ​​the ion migration tube in the form of drift gas through the first mass flow meter (2) and then through the drift gas inlet (3). The second path passes through the second interface of the two-position three-way solenoid valve (5), the three-way connector (24), the second mass flow meter (9), the second reagent molecule headspace purge device (10), and then enters the ion migration spectrum reaction zone through the second reagent molecule inlet (11); the third path passes through the second interface of the two-position three-way solenoid valve (5), the three-way connector (24), the third mass flow meter (12), the water reagent molecule headspace purge generator (13), and then enters the ion migration tube reaction zone through the first reagent molecule inlet (8); at the same time, the gas sampling pump (20) is started, and under the control of the sixth mass flow meter (19) and the fourth mass flow meter (16), the sample is sampled through the pipeline through the inlet (17) into the migration tube reaction zone.

7. The application according to any one of claims 5-6, characterized in that: The flow rate of the first mass flow meter (2) is 200-500 mL / min, the flow rate of the second mass flow meter (9) is 50-200 mL / min, the flow rate of the third mass flow meter (12) is 100-300 mL / min, the flow rate of the fourth mass flow meter (16) is 50-200 mL / min, the flow rate of the fifth mass flow meter (6) is 50-200 mL / min, the flow rate of the sixth mass flow meter (19) is 300-1100 mL / min, and the sampling flow rate is 50-200 mL / min.

8. The application according to any one of claims 5-6, characterized in that: In conventional reagent ion mode, by introducing organic reagent molecules into the reaction region of the ion mobility spectrum, the molecular ion peak M of the organic reagent molecule can be obtained. + or M2H + In the reagent ion switching mode, by simultaneously introducing organic and inorganic reagent molecules into the ion molecule reaction region, the reagent ions can be rapidly switched to H+. + (H2O) n This improves the detection sensitivity of substances with high proton affinity, wherein the substances with high proton affinity include one or more of ammonia, hydrazine (a hazardous chemical), and phthalates (plasticizers).

9. The application according to any one of claims 5-6, characterized in that: The aforementioned rapid switching combination reagent ion photoionization ion mobility spectrometry can not only be used for the detection of high proton affinity ammonia in exhaled breath, but also for the high selectivity and high sensitivity detection of high proton affinity VOCs in indoor and ambient air, thereby improving the selectivity and sensitivity of ion mobility spectrometry in complex matrix environments; high proton affinity VOCs include one or more of ammonia, hazardous chemical hydrazine, and plasticizer phthalic acid esters.

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