Ion detection device and detection method based on ion mobility spectrometry

Abstract

The invention relates to an ion detection device and method based on ion mobility spectrometry. The ion detection device comprises an ion migration tube and an ion fragmentation module, the ion migration tube internally comprises an ionization reaction region, a drift region and a collection region which are arranged in sequence; the device further comprises a first ion gate and a second ion gate, the first ion gate is located between the reaction region and the drift region, and the second ion gate is located in the drift region and divides the drift region into a first drift region and a second drift region in the arrangement direction. The ion fragmentation module is located on one side, deviating from the first drift region, of the second ion gate in the arrangement direction, and is used for fragmenting target ions to obtain secondary fragment ions; the two-stage mobility spectrometry is connected in series, the high-temperature ion fragmentation module is introduced, fragmentation of specific target ions in a normal-pressure environment is achieved, secondary characteristic fragments are obtained for detection, the mobility spectrometry detection qualitative capacity is greatly improved, the use environment requirement is lower, and maintenance is easy.

Description

Technical Field

[0001] The present invention relates to the technical field of ion mobility spectrometry, and in particular to an ion detection device and a detection method based on ion mobility spectrometry. Background Art

[0002] Ions of different substances have different mobilities, so the time required to fly the same distance in the same uniform electric field is different. The ion mobility spectrometry detects and determines the type of substance based on the characteristic information of the ion flight time. However, for substances with the same or similar mobilities, conventional ion mobility spectrometry cannot accurately distinguish them. To address this, ions with similar mobilities in the migration spectrum can be fragmented, and the substances can be further distinguished based on the migration spectrum information of the secondary fragment ions. However, the fragmentation method and detection technology are relatively complicated, and the fragmentation must be performed in a vacuum environment. Summary of the invention

[0003] To this end, the technical problem to be solved by the present invention is to overcome the technical difficulty in the prior art that ion mobility spectrometry is difficult to accurately distinguish substances with similar mobilities, provide an ion detection device and detection method based on ion mobility spectrometry, and introduce a high-temperature ion fragmentation module to improve the detection accuracy of ion mobility spectrometry.

[0004] In a first aspect, in order to solve the above technical problems, the present invention provides an ion detection device based on ion mobility spectrometry, which comprises:

[0005] An ion transfer tube, wherein the ion transfer tube includes an ionization reaction zone, a drift zone and a collection zone arranged in sequence; and further includes a first ion gate and a second ion gate, wherein the first ion gate is located between the reaction zone and the drift zone, the second ion gate is located in the drift zone and separates the drift zone into a first drift zone and a second drift zone along an arrangement direction, the first drift zone is located between the first ion gate and the second ion gate, and the second drift zone is located between the second ion gate and the collection zone;

[0006] An ion fragmentation module is located on a side of the second ion gate that is away from the first drift region in an arrangement direction; the ion fragmentation module is used to fragment target ions to obtain secondary fragment ions.

[0007] In one embodiment of the present invention, the ion fragmentation module includes a main body and a conductive wire. The main body is configured as an annular structure, and its interior is hollow to provide an avoidance space for the target ions. The conductive wire is located in the avoidance space, and the operating temperature of the conductive wire is 200°C to 500°C.

[0008] In one embodiment of the present invention, the material of the main body is set to ceramic, and the main body is provided with mounting holes on both sides of the avoidance space in the radial direction, and the conductive wire is sequentially passed through the mounting holes on both sides and fixed.

[0009] In one embodiment of the present invention, the conductive threads extend in the radial direction in the avoidance space and are arranged in parallel and spaced apart, and the spacing between the conductive threads is 1 mm to 2 mm.

[0010] In one embodiment of the present invention, the conductive wire is externally connected to a power source, and the conductive wire is configured as a nickel-chromium wire.

[0011] In one embodiment of the present invention, the first ion gate includes a first grid and a second grid arranged in sequence along the arrangement direction; the second ion gate includes a third grid and a fourth grid arranged in sequence along the arrangement direction; the first grid, the second grid, the third grid and the fourth grid are all configured so that the potential can be adjusted or fixed.

[0012] In one embodiment of the present invention, it further comprises a drift gas inlet, a sample gas inlet and a gas path outlet; the drift gas inlet is connected to the collection area, and the sample gas inlet and the gas path outlet are connected to the reaction area and are arranged opposite to each other.

[0013] In a second aspect, the present invention further provides an ion detection method based on ion mobility spectrometry, which is implemented by the ion detection device based on ion mobility spectrometry in any of the above embodiments, and the ion detection method includes:

[0014] Step 1, closing the ion fragmentation module, and obtaining the flight time ΔT of the target ion in the first drift region by controlling the first ion gate and the second ion gate;

[0015] Step 2, controlling the opening time of the first ion gate to be T0, and controlling the opening time of the second ion gate to be T0+ΔT; the opening time of the first ion gate and the second ion gate are both t0, and the target ions are screened;

[0016] Step 3, turning on the ion fragmentation module, the target ions enter the ion fragmentation module through the second ion gate, and are fragmented to obtain secondary fragment ions and their migration spectrum characteristic information, thereby completing the detection of the target ions.

[0017] In one embodiment of the present invention, step 1 comprises:

[0018] The second ion gate is controlled to be normally open, and the first ion gate is opened at time T1; the time when the target ion reaches the collection area and is collected is T2, and the first migration time of the target ion is detected as,

[0019] t1 = T2 - T1;

[0020] The first ion gate is controlled to be normally open, and the second ion gate is opened at time T3; the time when the target ion reaches the collection area and is collected is T4, and the second migration time of the target ion is detected as,

[0021] t2 = T4 - T3;

[0022] Then there is,

[0023] ΔT=t1-t2.

[0024] In one embodiment of the present invention, the door opening time t0 is set to 250 μs to 500 μs.

[0025] The above technical solution of the present invention has the following beneficial effects compared with the prior art:

[0026] The ion detection device and detection method based on ion mobility spectrometry described in the present invention perform two-stage series connection on the traditional ion mobility spectrometry, connect the two-stage migration spectrometry in series and introduce a high-temperature ion fragmentation module to achieve fragmentation of specific target ions under normal pressure environment, and obtain secondary fragment ions for detection; compared with the traditional single ion gate structure, the present invention can further distinguish and screen target ions, avoid confusion caused by the same or similar mobility, greatly improve the qualitative ability of migration spectrum detection, and facilitate the identification of contraband; in addition, compared with the tandem mass spectrometry technology, the fragmentation ion structure of the present invention is simpler, the use environment requirements are lower, it is easy to maintain and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0028] Figure 1 Schematic diagram of the structure of an ion detection device based on ion mobility spectrometry in Embodiment 1 of the present invention;

[0029] Figure 2 Schematic diagram of the structure of the main body of the ion fragmentation module in the first embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the structure of the ion fragmentation module in the first embodiment of the present invention;

[0031] Figure 4 This is a timing diagram of two groups of ion gates screening target ions in the second embodiment of the present invention;

[0032] Figure 5 This is the migration spectrum of the first injection in Example 2 of the present invention;

[0033] Figure 6 This is the migration spectrum of the second injection in Example 2 of the present invention;

[0034] Figure 7 is the migration spectrum of the sample in the screening mode in Example 2 of the present invention;

[0035] Figure 8 This is the migration spectrum obtained by turning on the ion fragmentation module after screening in Example 2 of the present invention.

[0036] Explanation of the reference numerals in the specification: 1. ion fragmentation module; 11. main body; 1101. avoidance space; 1102. mounting hole; 12. conductive wire; 2. ionization reaction zone; 21. corona ion source; 22. sample gas inlet; 23. gas path outlet; 31. first ion gate; 32. second ion gate; 41. first drift zone; 42. second drift zone; 5. collection zone; 51. drift gas inlet; 6. Faraday disk; 7. collection amplifier end. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0038] Embodiment 1

[0039] Reference Figure 1 to Figure 3 The first embodiment of the present invention provides an ion detection device based on ion mobility spectrometry, wherein the ion detection device includes an ion migration tube and an ion fragmentation module 1 arranged in the ion migration tube; the ion migration tube realizes the screening of target ions by setting two groups of ion gates, and the ion fragmentation module 1 is used to fragment the target ions to obtain secondary fragment ions, and qualitatively confirm the characteristic information of the secondary fragment ions to improve the detection accuracy and detection precision of the target ions.

[0040] Specifically, refer to Figure 1 As shown, the ion transfer tube includes an ionization reaction zone 2, a drift zone and a collection zone 5 arranged in sequence, and the sample migrates from the ionization reaction zone 2 to the collection zone 5 along the arrangement direction in the ion transfer tube. The collection zone 5 includes a Faraday disk 6, which is externally connected to a collection amplifier end 7 for signal collection and amplification. The ionization reaction zone 2 is used to ionize the sample, and includes a sample gas inlet 22 and a gas path outlet 23, and is also connected to a corona ion source 21; the sample gas inlet 22 is arranged opposite to the gas path outlet 23, and the sample reacts chemically with the ion reservoir of the reactant ion (RIP) to generate analyte ions, and the analyte ions include target ions and impurity ions.

[0041] It should be noted that in the existing ion mobility spectrometry detection device, an ion gate is set in the migration tube, and the ion type is determined according to the migration time of the ions passing through the ion gate to the collection area. However, if there are ions with the same or similar mobility as the target ions among the impurity ions, the specific sample type cannot be determined only by the migration time. Therefore, the inventors of this case set two ion gates in the ion migration tube, use the migration time to preliminarily screen the target ions, and then use the ion fragmentation module 1 to fragment the ions to further determine the substance type.

[0042] Specifically, refer to Figure 1 As shown, in the first embodiment of the present invention, two groups of Tyndall and Power gates (TPG) are provided to separate the cascade mobility spectrometry detection device and control the passage of ions, and the two groups of ion gates include a first ion gate 31 and a second ion gate 32; the first ion gate 31 is located between the ionization reaction region 2 and the drift region, the second ion gate 32 is located in the drift region and separates it into a first drift region 41 and a second drift region 42 along the arrangement direction, the first drift region 41 is located between the first ion gate 31 and the second ion gate 32, and the second drift region 42 is located between the second ion gate 32 and the collection region 5. The ion fragmentation module 1 is located on the side of the second ion gate 32 away from the first drift region 41 in the arrangement direction.

[0043] Furthermore, the first ion gate 31 includes a first grid G11 and a second grid G12 arranged in sequence along the arrangement direction; the second ion gate 32 includes a third grid G21 and a fourth grid G22 arranged in sequence along the arrangement direction; the first grid G11, the second grid G12, the third grid G21 and the fourth grid G22 are all configured so that the potential can be adjusted or fixed.

[0044] Next, in the positive mode, the first ion gate 31 and the second ion gate 32 are used to control the passage of positive ions; the potential of the second grid G12 is fixed, the potential of the first grid G11 is adjusted so that the voltage of the first grid G11 is higher than that of the second grid G12, the first ion gate 31 is opened, and ions can enter the first drift region 41 through the first ion gate 31 within the opening time of the first ion gate 31. If the potential of the first grid G11 is adjusted so that the voltage of the first grid G11 is lower than that of the second grid G12, the first ion gate 31 is closed and ions cannot pass through. In the positive mode, the potential of the fourth grid G22 is fixed, and the potential of the third grid G21 is adjusted to control the opening or closing of the second ion gate 32. In the negative mode, the ion gate is used to control the passage of negative ions. The first ion gate 31 fixes the potential of the first grid G11, and adjusts the potential of the second grid G12 to control opening and closing; the second ion gate 32 fixes the potential of the third grid G21, and adjusts the potential of the fourth grid G22 to control opening and closing; the two groups of ion gates are controlled by two pulse signals respectively, and both work in the positive mode, or, both work in the negative mode, which will not be repeated here.

[0045] Furthermore, the ion fragmentation module 1 includes a main body 11 and a conductive wire 12, the main body 11 is configured as an annular structure, and is configured as a high-temperature resistant machinable ceramic; the interior of the annular structure is hollow, providing an avoidance space 1101 for the passage of the target ions; the conductive wire 12 is configured as a nickel-chromium wire with a diameter of 0.1mm to 0.3mm, and is at least partially located in the avoidance space 1101. When the conductive wire 12 is connected to an external power supply and current passes through it, a high temperature of 200°C to 500°C is generated in the avoidance space 1101 for fragmenting ions.

[0046] It should be noted that currently, fragmentation of ions is often achieved in a vacuum environment through tandem mass spectrometry technology, where ions are screened using mass spectrometry detection technology, and external voltage is applied to force the screened ions to fragment. The fragmentation process and detection process are relatively complex, and the system has certain requirements for the degree of vacuum. Accordingly, the ion detection device of the present invention is based on the principle that ions can obtain energy from a high-temperature environment and convert it into their own internal energy, and introduces a high-temperature ion fragmentation module 1, which can achieve ion fragmentation in a normal pressure environment, has lower environmental requirements, a simple structure and process, and does not require the introduction of a vacuum system.

[0047] Next, according to the following formula, the energy sources of ions in ion mobility spectrometry are mainly divided into three parts: thermal energy, electric field energy, and energy brought by neutral collisions;

[0048]

[0049] Where K represents the mobility of the ion, E ionrepresents the total energy of the ion; k B represents the Boltzmann constant, T represents the temperature, 3 / 2k B T represents the thermal energy content of the energy source; m ion represents the mass of the ion, v d Represents the drift velocity of ions in the drift electric field, 1 / 2m ion v d 2 Represents the electric field energy in the energy source; m b Represents the molar mass of the carrier gas (air), 1 / 2m b v d 2 Represents the neutral collision part of the energy source. In the first embodiment of the present invention, by setting the local high temperature of the ion fragmentation module 1, the target ions obtain enough energy through the high temperature, the internal chemical bonds are broken, and then the secondary fragment ions with specific characteristics are generated.

[0050] Further, refer to Figure 2 and Figure 3 As shown, the main body 11 is provided with mounting holes 1102 on both sides of the radial direction of the avoidance space 1101. Preferably, two rows of the mounting holes 1102 are respectively provided on both sides of the radial direction, and the two rows of mounting holes 1102 are staggered in the arrangement direction. The conductive wires 12 are sequentially passed through and wound in the mounting holes 1102 on both sides. The conductive wires 12 extend in the radial direction in the area within the avoidance space 1101 and are arranged in parallel and spaced apart. The spacing between the conductive wires 12 is 1 mm to 2 mm to ensure the normal passage of ions.

[0051] Specifically, refer to Figure 1 As shown, the ion detection device also includes a drift gas inlet 51, which is connected to the collection area 5 and allows pure air, after the moisture is filtered by the molecular sieve, to be introduced for backblowing to blow the impurity ions away from the collection area 5, and the drift gas is also discharged from the gas path outlet 23.

[0052] Embodiment 2

[0053] Embodiment 2 of the present invention provides an ion detection method based on ion mobility spectrometry, and is implemented by the ion detection device in embodiment 1. Specifically, the ion detection method includes:

[0054] Step 1, closing the ion fragmentation module 1, and obtaining the flight time ΔT of the target ion in the first drift region 41 by controlling the first ion gate 31 and the second ion gate 32;

[0055] Specifically, the step 1 includes:

[0056] In the negative mode, the second ion gate 32 is controlled to be normally open, the potential of the first grid G11 is fixed, and the voltage of the second grid G12 is controlled by a pulse signal to realize the opening and closing control of the first ion gate 31; the rising edge of the pulse signal that controls the second grid G12 is at time T1, the potential of the second grid G12 is higher than that of the first grid G11 at time T1, and the first ion gate 31 is opened at time T1; the time when the target ion reaches the collection area 5 and is collected is T2, so the first migration time of the target ion is t1=T2-T1, and the first migration time is the time when the target ion migrates from the first ion gate 31 to the collection area 5 and is collected, corresponding to the peak time of the first sample injection detection.

[0057] In the negative mode, the first ion gate 31 is controlled to be normally open, the potential of the third grid G21 is fixed, and the voltage of the fourth grid G22 is controlled by a pulse signal to realize the opening and closing control of the second ion gate 32; the rising edge of the pulse signal for controlling the fourth grid G22 is at time T3, the potential of the third grid G21 is higher than that of the fourth grid G22 at time T3, and the second ion gate 32 is opened at time T3; the time when the target ion reaches the collection area 5 to be collected is T4, and the second migration time of the target ion is t2=T4-T3, and the second migration time is the time when the target ion migrates from the second ion gate 32 to the collection area 5 to be collected, corresponding to the peak time of the second sample injection detection.

[0058] Next, the flight time of the target ions in the first drift region 41 , that is, the migration time from the first ion gate 31 to the second ion gate 32 is ΔT=t1−t2.

[0059] Step 2: In the negative mode, two pulse signals are used to control the second grid G12 and the fourth grid G22 respectively, so as to realize the switch control of two groups of ion gates. Figure 4 As shown, the opening rising edge of the first ion gate 31 is at time T0, and the second ion gate 32 is controlled to open by a pulse signal at time T0+ΔT; sample screening is performed, and target ions are obtained in the screening mode described in step 2;

[0060] It should be noted that in a preferred embodiment of the present invention, the opening time t0 of the first ion gate 31 and the second ion gate 32 are both set to 250μs to 500μs; the ion gate needs to have a certain opening time to facilitate the passage of ions, but at the same time, the longer the opening time of the ion gate, the more ions pass through, the greater the tolerance for ion mobility, and the lower the detection accuracy.

[0061] Step 3, based on step 2, open the ion fragmentation module 1, allow current to flow through the conductive wire 12 to generate heat and produce local high temperature, and the target ions enter the ion fragmentation module 1 through the second ion gate 32, fragment to obtain secondary fragment ions and obtain their characteristic information, thereby completing the detection of the sample.

[0062] In one implementation of the second embodiment of the present invention, refer to Figures 5 to 8 As shown, the sample is taken as an example of the explosive TNT, which is a common test object in security inspection. A TNT standard solution with a concentration of 100ng / uL is selected and sent into the thermal desorption injector by wiping injection. The injection volume is 10uL each time. The target ion is TNT ion, and the impurity ions such as solvent ions that are easily confused exist in the test sample. The first injection is measured based on the first ion gate 31, and the following is obtained: Figure 5 The migration profile shown, Figure 5 There are three kinds of ion peaks, namely RIP, TNT and solvent ion; the peak time of TNT ion is t1=8.75ms.

[0063] Next, the second injection is measured with the second ion gate 32 as the reference, and the following is obtained: Figure 6 The migration profile shown, Figure 6 There are two ion peaks, namely RIP and TNT ions; the peak time of TNT ions is t2 = 4.82ms. According to the two injection measurements, the migration time of TNT ions between the two sets of ion gates is ΔT = t1-t2 = 8.75ms-4.82ms = 3.93ms. The delay time of the two sets of ion gates is set to 3.93ms, which can screen TNT ions and ions with the same mobility as TNT. In this embodiment, RIP and solvent can be filtered out. Figure 7 As shown, it is a single TNT ion peak screened out. Figure 7 The flight time of the TNT ion peak is 8.71 ms, which is close to the peak time t1 of the first injection measurement. The ion fragmentation module 1 is activated on the basis of the screening mode, and a local high temperature is applied on the flight path of the screened ions to obtain the following Figure 8 The measurement results shown are Figure 8 Two ion peaks of TNT parent ion and TNT secondary characteristic fragment ion appeared in the ion analysis, of which the parent ion peak time was 8.70ms and the secondary fragment ion peak time was 7.27ms. The migration spectrum characteristic information such as the peak time and peak intensity of the secondary fragment ion can assist in qualitatively confirming the material type of the target ion and reduce the error caused by similar mobility in single ion gate detection.

[0064] The present invention sets up a tandem secondary migration spectrum, wherein the first-stage migration spectrum realizes the screening of specific target ions, and the second-stage migration spectrum obtains the migration spectrum characteristic information of the secondary fragment ions after high-temperature fragmentation; the influence of similar parent ion mobility on the detection accuracy of the migration spectrum is avoided, and the detection precision and accuracy are improved; at the same time, the detection process of the present invention is simple and does not require a vacuum environment, and has broad application prospects in the fields of on-site detection, drug detection, and medicine inspection.

[0065] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. An ion detection device based on ion mobility spectrometry, characterized in that: include, An ion transfer tube, wherein the ion transfer tube includes an ionization reaction zone, a drift zone and a collection zone arranged in sequence; and further includes a first ion gate and a second ion gate, wherein the first ion gate is located between the reaction zone and the drift zone, the second ion gate is located in the drift zone and separates the drift zone into a first drift zone and a second drift zone along an arrangement direction, the first drift zone is located between the first ion gate and the second ion gate, and the second drift zone is located between the second ion gate and the collection zone; An ion fragmentation module is located on a side of the second ion gate that is away from the first drift region in an arrangement direction; the ion fragmentation module is used to fragment target ions to obtain secondary fragment ions.

2. The ion detection device based on ion mobility spectrometry according to claim 1, characterized in that: The ion fragmentation module includes a main body and a conductive wire. The main body is configured as a ring structure with a hollow interior to provide an escape space for the target ions. The conductive wire is located in the escape space and has an operating temperature of 200°C to 500°C.

3. The ion detection device based on ion mobility spectrometry according to claim 2, characterized in that: The material of the main body is set to ceramic, and the main body is provided with mounting holes on both sides of the avoidance space in the radial direction, and the conductive wires are successively passed through the mounting holes on both sides and fixed.

4. The ion detection device based on ion mobility spectrometry according to claim 2 or 3, characterized in that: The conductive threads extend in the avoidance space along the radial direction and are arranged in parallel and at intervals, and the spacing between the conductive threads is 1 mm to 2 mm.

5. The ion detection device based on ion mobility spectrometry according to claim 4, characterized in that: The conductive wire is externally connected to a power source, and the conductive wire is configured as a nickel-chromium wire.

6. The ion detection device based on ion mobility spectrometry according to claim 1, characterized in that: The first ion gate includes a first grid and a second grid arranged in sequence along the arrangement direction; the second ion gate includes a third grid and a fourth grid arranged in sequence along the arrangement direction; the first grid, the second grid, the third grid and the fourth grid are all configured so that the potential can be adjusted or fixed.

7. The ion detection device based on ion mobility spectrometry according to claim 1, characterized in that: It also includes a drift gas inlet, a sample gas inlet and a gas path outlet; the drift gas inlet is connected to the collection area, and the sample gas inlet and the gas path outlet are connected to the reaction area and are arranged opposite to each other.

8. An ion detection method based on ion mobility spectrometry, characterized in that: The ion detection method is realized by the ion detection device based on ion mobility spectrometry according to any one of claims 1 to 7, wherein the ion detection method comprises: Step 1, closing the ion fragmentation module, and obtaining the flight time ΔT of the target ion in the first drift region by controlling the first ion gate and the second ion gate; Step 2, controlling the opening time of the first ion gate to be T0, and controlling the opening time of the second ion gate to be T0+ΔT; the opening time of the first ion gate and the second ion gate are both t0, and the target ions are screened; Step 3, turning on the ion fragmentation module, the target ions enter the ion fragmentation module through the second ion gate, and are fragmented to obtain secondary fragment ions and their migration spectrum characteristic information, thereby completing the detection of the target ions.

9. The ion detection method based on ion mobility spectrometry according to claim 8, characterized in that: The step 1 comprises: Controlling the second ion gate to be normally open, and opening the first ion gate at time T1; The time when the target ion reaches the collection area and is collected is T2, and the first migration time of the target ion is detected as t1=T2-T1; The first ion gate is controlled to be normally open, and the second ion gate is opened at time T3; the time when the target ions reach the collection area and are collected is T4, and the second migration time of the target ions is detected to be t2=T4-T3; Then there is, ΔT=t1-t2.

10. The ion detection method based on ion mobility spectrometry according to claim 8, characterized in that: The door opening time t0 is set to 250 μs to 500 μs.

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