A discharge ionization source for ion mobility spectroscopy and its application

Abstract

This invention discloses a discharge ionization source for ion mobility spectrometry, designed based on the principle of low-temperature plasma discharge. The radio frequency electrode of the discharge ionization source is a rod-shaped metal electrode placed inside a single-ended open quartz glass tube. The DC electrodes of the discharge ionization source are arranged in an array with equal spacing on the outer wall of the discharge glass tube. The potential of each DC electrode can be independently adjusted, facilitating the control of the DC electric field direction within the ionization source, thereby controlling the migration direction of ions. Furthermore, multiple gas interfaces are provided on the quartz glass tube, allowing for the control of the airflow direction and the composition of the discharge gas. Based on the array-type DC discharge electrode and multi-gas interface structure, the discharge ionization source uses air as the discharge gas, enabling switching between positive and negative ion modes, reagent ion components, and sample ionization methods. It features a simple structure, portable operation, and is suitable for ion mobility spectrometry.

Description

Technical Field

[0001] This invention relates to ionization sources for ion mobility spectrometry, specifically, a low-temperature plasma discharge ionization source with controllable ionization pathway and reactant ions. Background Technology

[0002] Ion mobility spectrometry (IMS) is a mainstream technology for detecting trace targets such as explosives, drugs, chemical warfare agents, and industrial hazardous chemicals. As a crucial component of an IMS spectrometer, the ion source primarily determines whether a target can be detected and the sensitivity of direct detection. Discharge ionization sources are favored by IMS technology developers due to their simple structure and ability to provide high-abundance reactive reagent ions. Examples include the dielectric barrier discharge ionization source developed by Professor Jiang Jie of Harbin Institute of Technology (CN103776893), the corona discharge ionization source developed by Professor Ni Kai of Tsinghua University (CN110289203), and the multi-needle corona discharge ionization source developed by Zheng Haidong et al. of the First Research Institute of the Ministry of Public Security (CN110189978), among others.

[0003] Discharge ionization sources typically require expensive inert gases (such as helium or argon) to obtain single-component reagent ions, which is unsuitable for the portable, on-site applications required by ion mobility spectrometers (IMS). When air is used as the discharge gas, the discharge ionization source often involves processes such as ozone and nitrogen oxide generation, leading to uncontrollable reagent ion composition and complications in the ionization process caused by excited-state neutral particles. Therefore, developing discharge ionization sources with controllable reagent ions and controllable ionization processes using air as the discharge gas has always been a focus of research and development for IMS technology. Summary of the Invention

[0004] This invention provides a discharge ionization source based on the principle of low-temperature plasma discharge. It utilizes an array of DC discharge electrodes and a multi-gas interface design, using air as the discharge gas, to achieve functions such as switching between positive and negative ion modes, switching between ion components of reaction reagents, and switching between sample ionization methods.

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

[0006] A discharge ionization source for ion mobility spectroscopy includes a radio frequency discharge needle, a quartz glass tube, and a DC electrode.

[0007] The quartz glass tube is a cylindrical tube that is closed at the left end and open at the right end. Along the direction from the right end to the left end of the quartz glass tube, a first annular DC electrode, a second annular DC electrode, ..., are sequentially and equally spaced on the outer wall of the quartz glass tube. N -1 Ring-shaped DC electrode and the first N Ring-shaped DC electrode,N The value is a positive integer greater than or equal to 4, wherein the first annular DC electrode is located near the right end of the quartz glass tube, and the second... N The annular DC electrode is located near the left end of the quartz glass tube;

[0008] The radio frequency discharge needle is a round rod-shaped metal electrode. The bottom left side of the quartz glass tube is a hemispherical surface protruding to the left. The center of the hemispherical surface is located on the axis of the tube. A through hole is opened on the bottom hemispherical surface along the axis. One end of the radio frequency discharge needle passes through the through hole and extends into the tube, while the other end is outside the tube. The outer wall of the radio frequency discharge needle is sealed to the inner wall of the through hole. The radio frequency discharge needle is coaxial with the quartz glass tube. The end plane of the radio frequency discharge needle at the end inside the tube extends along the axis of the quartz glass tube to the midpoint of the line connecting the left end face of the third annular DC electrode and the right end face of the fourth annular DC electrode with the axis of the quartz glass tube.

[0009] A first gas interface is provided on the circumferential sidewall of the quartz glass tube between the first and second annular DC electrodes, and a second gas interface is provided on the circumferential sidewall of the quartz glass tube between the second and third annular DC electrodes. The bottom surface of the left end of the quartz glass tube is connected to the first... N A third gas interface is provided on the circumferential sidewall of the tube between the annular DC electrodes;

[0010] The first gas interface, the second gas interface, and the third gas interface are used for the introduction and extraction of discharge gas and chemical doping reagent gas inside the quartz glass tube, and to regulate the direction of airflow inside the tube.

[0011] The radio frequency discharge needle applies a DC bias potential of V , frequency is f and peak value is V p-p The radio frequency voltage, the first annular DC electrode, the second annular DC electrode (, ..., the first N -1 Ring-shaped DC electrode and the first N The first DC potential is applied to the ring-shaped DC electrodes respectively. V 1. Second DC potential V 2.......,No. N -1 DC potential V N-1 and the N DC potential V N Discharge plasma is formed inside the quartz glass tube to regulate the DC potential. V , V 1. V 2, ... V N-1 and V NThe relative heights of these elements can control the migration direction of ions inside the quartz glass tube.

[0012] The DC bias potential V -10000 to 10000 V, frequency f The peak-to-peak frequency ranges from 1 to 3 MHz. V p-p 100 to 300 V;

[0013] In the reaction reagent ion switching mode, the discharge gas enters the quartz glass tube through the first gas interface, the chemical doping reagent gas enters the quartz glass tube through the second gas interface, and the third gas interface is connected to the vacuum pump pump port. The vacuum pump pumping speed is greater than the flow rate of the chemical doping reagent gas and less than the sum of the flow rates of the discharge gas and the chemical doping reagent gas.

[0014] electric potential V and V N Keeping the same, in positive ion mode, DC potential V 1 < V 2< V 3< V 4 < ... < V N-1 < V N At that time, the positively reacting reagent ions flow out from the right end of the quartz glass tube; in negative ion mode, the DC potential... V 1> V 2> V 3> V 4 > ... > V N-1 > V N The negative reaction reagent ions flow out from the right end of the quartz glass tube. Changing the composition of the chemical doping reagent gas can change the composition of the positive and negative reaction reagent ions.

[0015] In the sample ionization mode switching mode, the first gas interface is sealed, the discharge gas enters the quartz glass tube through the third gas interface, and the chemical doping reagent gas enters the quartz glass tube through the second gas interface.

[0016] electric potential V and V 4 Keeping the same, in positive ion mode, DC potential V 1> V 2> V 3> V 4 and V N > V N-1 >...> V4. Excited-state neutral molecules flow out from the right end of the quartz glass tube. In negative ion mode, the DC potential... V 1 < V 2< V 3< V 4 and V N < V N-1 <...< V 4. Excited-state neutral molecules flow out from the right end of the quartz glass tube. Changing the composition of the chemical dopant gas can change the composition of the excited-state neutral molecules.

[0017] The discharge ionization source serves as the ion source for the ion mobility spectrum. The first annular DC electrode serves as the first annular electrode in the ionization region of the ion mobility tube along the direction from the ion source to the ion receiver. Ions or excited-state neutral molecules flowing out from the right end of the quartz glass tube enter the ionization region of the ion mobility spectrum and react with the molecules of the sample to be tested, generating sample product ions. These ions then enter the migration region of the ion mobility spectrum through the periodically opening ion gates and are separated and detected.

[0018] The discharge ionization source for ion mobility spectrometry provided by this invention is designed based on the principle of low-temperature plasma discharge. The radio frequency electrode of the discharge ionization source is a rod-shaped metal electrode placed inside a single-ended open quartz glass tube. The DC electrodes of the discharge ionization source are arranged in an array with equal spacing on the outer wall of the discharge glass tube. The potential of each DC electrode can be independently adjusted, facilitating the control of the DC electric field direction within the ionization source, thereby controlling ion migration. In addition, multiple gas interfaces are provided on the quartz glass tube, allowing for convenient control of the airflow direction and the composition of the discharge gas. Based on the structural design of the arrayed DC discharge electrode and multiple gas interfaces, the discharge ionization source uses air as the discharge gas, enabling switching between positive and negative ion modes, reagent ion components, and sample ionization methods. It features a simple structure, portable operation, and is suitable for ion mobility spectrometers.

[0019] The advantages of this invention are:

[0020] The discharge ionization source provided by this invention is designed based on the principle of low-temperature plasma discharge. It has a simple structure and can directly use air as the discharge gas. It can quickly switch between positive and negative ion modes, reaction reagent ion components and sample ionization methods. It is portable and very suitable for on-site detection of ion mobility spectrometers.

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

[0022] Figure 1A schematic diagram of the ion migration tube structure based on the discharge ionization source disclosed in this invention. Wherein: 1-RF discharge needle; 2-quartz glass tube; 3-1-first DC electrode; 3-2-second DC electrode; 3-3-third DC electrode; 3-4-fourth DC electrode; 3-5-fifth DC electrode; 3-6-sixth DC electrode; 4-first gas interface; 5-second gas interface; 6-third gas interface; 7-ionization region; 8-ion gate; 9-migration region; 10-ion receiving electrode; 11-drift gas inlet; 12-sample gas inlet; 13-outlet.

[0023] Figure 2 When purified air containing acetone, benzene, and toluene is used as the chemical dopant gas, the reaction reagent ions generated by the discharge ion source are as follows: (a) Ion mobility generated when purified air containing acetone is used as the chemical dopant gas. K 0 = 1.86 cm 2 V -1 s -1 (a) The reaction reagent ions; (b) Purified air containing benzene as a chemical dopant reagent gas, the resulting ion mobility K 0 = 2.22 cm 2 V -1 s -1 (c) Purified air containing toluene as a chemical dopant gas, resulting in ion mobility. K 0 = 2.07 cm 2 V -1 s -1 The reaction reagent ions.

[0024] Figure 3 Ion mobility spectrum response spectra of exhaled air containing 20 ppbv propofol and 50 ppbv sevoflurane when purified air containing toluene is used as the chemical dopant gas for discharge ionization. (a) Response spectrum of propofol, showing the observed response. K 0 = 1.5 cm 2 V -1 s -1 (a) Product ions; (b) Response spectrum of heptafluoroane, with virtually no response signal observed.

[0025] Figure 4 The diagram shows the structure of the discharge ionization source disclosed in this invention within an ion migration tube. Wherein: 1-RF discharge needle; 2-quartz glass tube; 3-1-first DC electrode; 3-2-second DC electrode; 3-3-third DC electrode; 3-4-fourth DC electrode; 3-5-fifth DC electrode; 3-6-sixth DC electrode; 4-first gas interface; 5-second gas interface; 6-third gas interface. Detailed Implementation Example 1

[0026] An ion migration tube device constructed based on the discharge ionization source disclosed in this invention, such as... Figure 1 As shown.

[0027] The quartz glass tube 2 is a cylindrical tube that is closed at the left end and open at the right end. Along the direction from the right end to the left end of the quartz glass tube 2, a first annular DC electrode 3-1, a second annular DC electrode 3-2, ..., and so on are sequentially and equally spaced on the outer wall surface of the quartz glass tube 2. six Among the annular DC electrodes 3-6, the first annular DC electrode 3-1 is located near the right end of the quartz glass tube 2, and the second... six The annular DC electrode 3-6 is located near the left end of the quartz glass tube 2;

[0028] The radio frequency discharge needle 1 is a round rod-shaped metal electrode. The bottom left side of the quartz glass tube 2 is a hemispherical surface protruding to the left. The center of the hemispherical surface is located on the axis of the tube. A through hole is opened on the bottom hemispherical surface along the axis. One end of the radio frequency discharge needle 1 passes through the through hole and extends into the tube. The other end is outside the tube. The outer wall of the radio frequency discharge needle 1 is sealed to the inner wall of the through hole. The radio frequency discharge needle 1 is coaxial with the quartz glass tube 2. The end plane of the radio frequency discharge needle 1 at the end inside the tube extends along the axis of the quartz glass tube 2 to the midpoint of the line connecting the left end face of the third annular DC electrode 3-3 and the right end face of the fourth annular DC electrode 3-4 with the axis of the quartz glass tube 2.

[0029] A first gas interface 4 is provided on the circumferential sidewall of the quartz glass tube 2 between the first annular DC electrode 3-1 and the second annular DC electrode 3-2. A second gas interface 5 is provided on the circumferential sidewall of the quartz glass tube 2 between the second annular DC electrode 3-2 and the third annular DC electrode 3-3. The bottom surface of the left end of the quartz glass tube is connected to the first annular DC electrode 3-1. six Circular DC electrode 3- 6 A third gas interface 6 is provided on the circumferential side wall of the tube between them.

[0030] The discharge ionization source consists of a radio frequency discharge needle 1, a quartz glass tube 2, and an array of DC electrodes 3-1 to 3-6. The DC electrode 3-1 is also the first annular electrode of the ionization region of the ion migration tube. The radio frequency discharge needle 1 is a tungsten metal rod with a diameter of 1 mm and a length of 50 mm. The quartz glass tube has a wall thickness of 1 mm, an inner diameter of 6 mm, and a length of 60 mm. One end of the radio frequency discharge needle 1 is inserted into the quartz glass tube 2 along the axis and is sealed at the left end face of the quartz glass tube 2. The length of the radio frequency discharge needle 1 inside the quartz glass tube 2 is 30 mm. The DC electrodes 3-1 to 3-6 are all annular stainless steel electrodes with an inner diameter of 8 mm and an axial length of 3 mm, which are equally spaced on the outer wall of the quartz glass tube 2. The first gas interface 4, the second gas interface 5, and the third gas interface 6 on the quartz glass tube 2 are used for the introduction and export of discharge gas and chemical dopant gas, and for controlling the airflow direction inside the quartz glass tube 2.

[0031] The radio frequency discharge needle 1 applies a DC bias potential of V , frequency is f and peak value is V p-p The radio frequency voltage is applied to the first DC electrode 3-1, the second DC electrode 3-2, the third DC electrode 3-3, the fourth DC electrode 3-4, the fifth DC electrode 3-5, and the sixth DC electrode 3-6 respectively, with a first DC potential applied. V 1. Second DC potential V 2. Third DC potential V 3. Fourth DC potential V 4. Fifth DC potential V 5 and the sixth DC potential V 6 Discharge plasma is formed inside the quartz glass tube to regulate the DC potential. V , V 1. V 2. V 3. V 4. V 5 and V 6 The relative heights of these two elements can control the migration direction of ions inside the quartz glass tube.

[0032] Both the ionization region 7 and the migration region 9 are composed of alternating stacked annular conductive electrode plates with an axial length of 5 mm, an inner diameter of 18 mm, and an outer diameter of 30 mm, and annular insulating electrode plates with an axial length of 5 mm, an inner diameter of 18 mm, and an outer diameter of 30 mm. The length of the ionization region 2 is 30 mm, and the length of the migration region 11 is 75 mm. A uniform axial DC electric field of 500 V / cm is set in the ionization region 7 and the migration region 9. The ion gate 8 of the ion migration tube adopts the Bradbury-Neilsen type ion gate, which is made of 0.05 mm diameter metal wires braided on a PTFE PCB electrode plate with a wire spacing of 0.3 mm. The metal wires on the ion gate are divided into two mutually insulated groups. A 200 V potential difference is applied to achieve closure. The ion gate opening time is set to 150 μs. The ion receiving electrode 10 is a Faraday disk with a diameter of 6 mm, which is fixed on a metal shielding cylinder with an outer diameter of 30 mm.

[0033] The reaction reagent ions or excited-state neutral molecules flowing out from the right end of the quartz glass tube 2 enter the ionization region 7 and react with the sample molecules to be tested that enter the ionization region 7 through the sample gas inlet 12 to generate sample product ions. Then, they enter the migration region 9 through the periodically opening ion gate 8, are separated, and are detected by the ion receiving electrode 10. The resulting current signal is amplified by a microcurrent amplifier and then sampled and recorded by an oscilloscope.

[0034] The temperature of the ion migration tube is 100℃. The purifying gas is compressed air filtered through silica gel, molecular sieves, and activated carbon at a flow rate of 500 mL / min. It enters the migration zone 9 of the ion migration tube through the purifying gas inlet 11, flows into the ionization zone 7 through the ion gate 8, and then mixes with the sample gas that enters the ionization zone 7 through the sample gas inlet 12. The sample gas then flows out of the ion migration tube through the outlet 13. The sample gas is purified air carrying molecules of the target analyte. Example 2

[0035] When the ion migration tube of the discharge ionization source disclosed in Example 1 is operating in positive ion mode, a DC electric field of 500 V / cm is applied in the ionization region 7 and migration region 9 of the ion migration tube; an electric field of 500 V / cm is applied to the first DC electrode 3-1. V 1 = 5250 V, applied to the second DC electrode 3-2 V 2 = 5300 V, applied to the third DC electrode 3-3 V 3 = 5350 V, applied to the fourth DC electrode 3-4 V 4 = 5400 V, applied to the fifth DC electrode 3-4 V 5 = 5450 V, applied to the sixth DC electrode 3-6 V 6 = 5500 V, the DC bias potential applied to the RF discharge needle 1 is V = 5500 V, frequency is f=1.5 MHz and peak-to-peak value is V p-p = 200 V radio frequency voltage; one discharge gas at 200 mL / min enters the quartz glass tube 2 through the first gas interface 4, one chemical doping reagent gas at 100 mL / min enters the quartz glass tube 2 through the second gas interface 5, the third gas interface 6 is connected to the suction port of the suction pump, and the suction gas flow rate is 200 mL / min; one sample gas at 200 mL / min enters the ionization region 7 through the sample gas inlet 12;

[0036] When the discharge gas is purified air filtered through molecular sieves and activated carbon, and purified air containing acetone, benzene, and toluene is used as the chemical dopant gas, different reactive reagent ions generated by the discharge ion source can be detected. Figure 2 a represents the ion mobility produced when purified air containing acetone is used as a chemical dopant gas. K 0 = 1.86 cm 2 V -1 s -1 The reaction reagent ions; Figure 2 b represents purified air containing benzene as a chemical dopant reagent gas, and the resulting ion mobility. K 0 = 2.22 cm 2 V -1 s -1 The reaction reagent ions; Figure 2 c represents purified air containing toluene as a chemical dopant gas, and the resulting ion mobility. K 0 = 2.07 cm 2 V -1 s -1 The reaction reagent ions;

[0037] By controlling the reaction reagent ions generated by the discharge ionization source, highly selective detection of target samples can be achieved. Figure 3 The ion migration spectra obtained using toluene as the discharge ionization source and exhaled gas containing 20 ppbv propofol and 50 ppbv sevoflurane as the sample gas are shown. Figure 3 As can be seen in a, propofol exhibits a distinct signal peak ( K 0 = 1.5 cm 2 V -1 s -1 ), Figure 3 As can be seen in b, heptafluoroane showed virtually no response signal. This means that the reaction reagent ions formed using toluene ( K 0 = 2.07 cm 2 V -1 s -1This method can achieve highly selective detection of trace amounts of propofol in the exhaled breath of patients anesthetized with a mixture of propofol and sevoflurane.

[0038] When the ion mobility spectrum is operating in negative ion mode, an application is made to the first DC electrode 3-1 V 1 = -5250 V, applied to the second DC electrode 3-2 V 2 = -5300 V, applied to the third DC electrode 3-3 V 3 = -5350 V, applied to the fourth DC electrode 3-4 V 4 = -5400 V, applied to the fifth DC electrode 3-4 V 5 = -5450 V, applied to the sixth DC electrode 3-6 V 6 = -5500 V, the DC bias potential applied to the RF discharge needle 1 is V = -5500 V is sufficient to enable the discharge ionization source ion migration tube to work normally. Example 3

[0039] In Example 1, when the ion migration tube of the discharge ionization source is operating in positive ion mode, a DC electric field of 500 V / cm is applied to the ionization region 7 and migration region 9 of the ion migration tube; an electric field of 500 V / cm is applied to the first DC electrode 3-1. V 1 = 5400 V, applied to the second DC electrode 3-2 V 2 = 5350 V, applied to the third DC electrode 3-3 V 3 = 5300 V, applied to the fourth DC electrode 3-4 V 4 = 5250 V, applied to the fifth DC electrode 3-4 V 5 = 5300 V, applied to the sixth DC electrode 3-6 V 6 = 5350 V, the DC bias potential applied to the RF discharge needle 1 is V = 5250 V, frequency is f =1.5 MHz and peak-to-peak value is V p-p = 200 V radio frequency voltage; the first gas interface 4 is sealed, a discharge gas of 200 mL / min enters the quartz glass tube 2 through the third gas interface 6, a chemical doping reagent gas of 100 mL / min enters the quartz glass tube 2 through the second gas interface 5, and a sample gas of 200 mL / min enters the ionization region 7 through the sample gas inlet 12.

[0040] When the discharge gas is high-purity nitrogen and the sample gas is purified air filtered through molecular sieves and activated carbon, and helium and argon are used as chemical dopant gases respectively, the discharge ion source generates high-energy excited-state neutral particles. The neutral particles react with trace amounts of water in the sample gas to generate highly abundant hydrated hydrogen ions (H2O). n H + It can undergo molecular ion reactions with volatile organic compounds with high proton affinity to form product ions.

Claims

1. A discharge ionization source for ion mobility spectrometry, characterized in that: It includes a radio frequency discharge needle (1), a quartz glass tube (2), and a DC electrode (3); The quartz glass tube (2) is a cylindrical tube with a closed left end and an open right end. Along the direction from the right end to the left end of the quartz glass tube (2), a first annular DC electrode (3-1), a second annular DC electrode (3-2), ..., are sequentially and equally spaced on the outer wall surface of the quartz glass tube (2). N -1 Ring-shaped DC electrode (3- N -1) and the N Ring-shaped DC electrode (3- N ), N It is a positive integer greater than or equal to 4, wherein the first annular DC electrode (3-1) is close to the right end of the quartz glass tube (2), and the second... N Ring-shaped DC electrode (3- N ) Near the left end of the quartz glass tube (2); The radio frequency discharge needle (1) is a round rod-shaped metal electrode. The bottom left side of the quartz glass tube (2) is a hemispherical surface protruding to the left. The center of the hemispherical surface is located on the axis of the tube. A through hole is opened on the bottom side of the hemispherical surface along the axis. One end of the radio frequency discharge needle (1) passes through the through hole and extends into the tube. The other end is located outside the tube. The outer wall of the radio frequency discharge needle (1) is sealed to the inner wall of the through hole. The radio frequency discharge needle (1) is coaxial with the quartz glass tube (2). The end plane of the radio frequency discharge needle (1) at one end in the tube extends along the axis of the quartz glass tube (2) to the midpoint of the line connecting the left end face of the third annular DC electrode (3-3) and the right end face of the fourth annular DC electrode (3-4) with the axis of the quartz glass tube (2). A first gas interface (4) is provided on the circumferential sidewall of the quartz glass tube (2) between the first annular DC electrode (3-1) and the second annular DC electrode (3-2), and a second gas interface (5) is provided on the circumferential sidewall of the quartz glass tube (2) between the second annular DC electrode (3-2) and the third annular DC electrode (3-3). The bottom surface of the left end of the quartz glass tube (2) is connected to the first annular DC electrode (3-1) and the second annular DC electrode (3-2). N Ring-shaped DC electrode (3- N A third gas interface (6) is provided on the circumferential side wall of the pipe between the two pipes.

2. The discharge ionization source according to claim 1, characterized in that: The first gas interface (4), the second gas interface (5) and the third gas interface (6) are used to introduce and extract the discharge gas and chemical doping reagent gas inside the quartz glass tube (2) and to regulate the direction of the internal airflow.

3. The discharge ionization source according to claim 1, characterized in that: The radio frequency discharge needle (1) applies a DC bias potential of V , frequency is f and peak value is V p-p The radio frequency voltage, the first annular DC electrode (3-1), the second annular DC electrode (3-2), ..., the first N -1 Ring-shaped DC electrode (3- N -1) and the N Ring-shaped DC electrode (3- N Apply the first DC potential respectively V 1. Second DC potential V 2.......,No. N -1 DC potential V N-1 and the N DC potential V N Discharge plasma is formed inside the quartz glass tube (2) to adjust the DC potential. V , V 1. V 2, ... V N-1 and V N The relative heights of these two elements can control the migration direction of ions inside the quartz glass tube (2); The DC bias potential V -10000 to 10000 V, frequency f The peak-to-peak frequency ranges from 1 to 3 MHz. V p-p The voltage ranges from 100 to 300V.

4. The discharge ionization source according to any one of claims 1-3, characterized in that: In the reaction reagent ion switching mode, the discharge gas enters the quartz glass tube (2) through the first gas interface (4), the chemical doping reagent gas enters the quartz glass tube (2) through the second gas interface (5), and the third gas interface (6) is connected to the vacuum pump pumping port. The vacuum pump pumping speed is greater than the flow rate of the chemical doping reagent gas and less than the sum of the flow rates of the discharge gas and the chemical doping reagent gas. electric potential V and V N Keeping the same, in positive ion mode, DC potential V 1 < V 2< V 3< V 4 < ... < V N-1 < V N At that time, the positively reacting reagent ions flow out from the right end of the quartz glass tube (2), and in the negative ion mode, the DC potential is... V 1> V 2> V 3> V 4 > ... > V N-1 > V N The negative reaction reagent ions flow out from the right end of the quartz glass tube (2). Changing the composition of the chemical doping reagent gas can change the composition of the positive and negative reaction reagent ions.

5. The discharge ionization source according to any one of claims 1-3, characterized in that: In the sample ionization mode switching mode, the first gas interface (4) is sealed, the discharge gas enters the quartz glass tube (2) through the third gas interface (6), and the chemical doping reagent gas enters the quartz glass tube (2) through the second gas interface (5). electric potential V and V 4 Keeping the same, in positive ion mode, DC potential V 1> V 2> V 3> V 4 and V N > V N-1 >...> V 4. Excited-state neutral molecules flow out from the right end of the quartz glass tube (2). In negative ion mode, the DC potential is... V 1 < V 2< V 3< V 4 and V N < V N-1 <...< V 4. The excited-state neutral molecules flow out from the right end of the quartz glass tube (2). Changing the composition of the chemical doping reagent gas can change the composition of the excited-state neutral molecules.

6. An application of the discharge ionization source as described in any one of claims 1-5, characterized in that: The discharge ionization source serves as the ion source for the ion mobility spectrum. The first annular DC electrode (3-1) serves as the first annular electrode in the ionization region of the ion mobility tube along the direction from the ion source to the ion receiving electrode. Ions or excited-state neutral molecules flowing out from the right end of the quartz glass tube (2) enter the ionization region of the ion mobility spectrum and react with the molecules of the sample to be tested, generating sample product ions. Then, they enter the migration region of the ion mobility spectrum through the periodically opening ion gate of the ion mobility spectrum and are separated and detected.

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