Ion mobility spectrometry coupled to time-of-flight mass spectrometry and its coupled interface structure

Abstract

The present invention relates to an ion migration spectrometer and time-of-flight mass spectrometer and its combined interface structure, wherein the drainage electrode sheet can separate the electric field from the electrode behind. Since the inner diameter of the second through hole in the focusing electrode sheet gradually decreases, ions are transmitted under the guidance of the airflow, and have a large effective ion receiving area. Moreover, due to the convergence effect on the airflow, the transmission efficiency of the ions can be effectively improved. Since there is no electric field in the second through hole, the divergent field formed by the gradual decrease in the inner diameter will not cause ion loss. The ions coming out of the second through hole enter the ion channel of the cooling focusing electrode and are quickly cooled down. Under the action of the electric field of the quadrupole structure and the collision process with the background gas molecules, the radial energy is reduced and the spatial divergence is reduced, thereby forming a fine ion pump, which enters the time-of-flight mass spectrometer, which is conducive to improving the sensitivity of detection, reducing the detection limit, and improving the detection accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of chromatography and mass spectrometry detection, and in particular to an ion mobility spectrometer and time-of-flight mass spectrometer and a combined interface structure thereof. Background Art

[0002] The mass spectrometer represented by time-of-flight is a technology that separates and analyzes based on the mass-to-charge ratio of ions. It has the advantages of high resolution, high sensitivity, high mass accuracy and rapid analysis, and is an important means of qualitative analysis of the chemical composition of substances. However, time-of-flight mass spectrometry cannot analyze the spatial conformation of isomers and complex organic matter. Ion mobility spectrometry is a technology that separates and analyzes based on the molecular mass, charge and collision cross section (i.e., size and shape) of the analyte, and can perform preliminary separation of isomers and molecules of different conformations. If the advantages of these two analytical techniques are combined, the mobility (or collision cross section) of the analyte is separated by ion mobility spectrometry, and then the analyte is qualitatively characterized by mass spectrometry using time-of-flight mass spectrometry, separation in two different dimensions is achieved, and the peak capacity of the instrument is improved, which can meet the analysis of multi-component samples such as bio-organic molecules and complex matrices.

[0003] When the ion mobility spectrometer is used in conjunction with the time-of-flight mass spectrometer, the ions enter the time-of-flight mass spectrometer through the ion mobility spectrometer, which has many problems such as low ion transmission efficiency and air pressure changes. Only by connecting a suitable coupling interface can the above problems be solved. Directly connecting the injection port of the atmospheric pressure ion source time-of-flight mass spectrometer to the ion mobility spectrometer detection area is a feasible solution. The commonly used atmospheric pressure mass spectrometer interface is a metal capillary interface, which has the advantages of simple structure and convenient heating. However, since the ions are separated in a "group" manner in the ion mobility spectrometer, there is not only a certain spatial dispersion in the axial direction of ion transmission, but also a large divergence in the radial direction. The amount of ions that can enter the metal capillary is greatly reduced, and a large number of gaseous ions are lost in the transmission of the tube, resulting in insufficient sensitivity and the inability to give full play to the detection limit advantage of the mass spectrometer. If a small hole is directly used as an interface, there will be problems such as low ion amount, supersonic expansion of ions after passing through the small hole, and increased spatial divergence. Summary of the invention

[0004] Based on this, it is necessary to provide an ion mobility spectrometer and time-of-flight mass spectrometer with high sensitivity and detection accuracy and its combined interface structure.

[0005] A combined interface structure of an ion mobility spectrometer and a time-of-flight mass spectrometer comprises a drainage electrode sheet, a focusing electrode sheet and a cooling and focusing electrode, wherein the drainage electrode sheet, the focusing electrode sheet and the cooling and focusing electrode are arranged in sequence; wherein the drainage electrode sheet is provided with a first through hole; the focusing electrode sheet is provided with a second through hole, the inner diameter of the second through hole gradually decreases from one end close to the drainage electrode sheet to the end far from the drainage electrode sheet, and the inner diameter of the end with the larger inner diameter of the second through hole is consistent with the inner diameter of the outlet end of the first through hole; the cooling and focusing electrode is a quadrupole structure, the inlet end of the ion channel of the cooling and focusing electrode is flush with the end with the smaller inner diameter of the second through hole, and the size of the inlet end is larger than the inner diameter of the end with the smaller inner diameter of the second through hole; the first through hole, the second through hole and the ion channel are coaxially arranged.

[0006] In one embodiment, the inner diameters of the first through holes are consistent.

[0007] In one embodiment, the drainage electrode sheet has a main body and a drainage portion; the drainage portion is protruding from a side surface of the main body away from the current focusing electrode sheet, and the angle between the outer wall of the drainage portion and the side surface is not less than 90°; the first through hole passes through the drainage portion and the main body in sequence.

[0008] In one embodiment, the inner diameter of the first through hole is 6-26 mm.

[0009] In one embodiment, the second through hole is a truncated cone-shaped hole with a uniformly changing inner diameter.

[0010] In one embodiment, the current focusing electrode sheet has a connecting portion and a current focusing portion; the connecting portion is arranged close to the drainage electrode sheet, and the current focusing portion is protruding on a side surface of the connecting portion away from the drainage electrode sheet; the second through hole passes through the connecting portion and the current focusing portion in sequence.

[0011] In one embodiment, the inner diameter of the second through hole at the end with a larger inner diameter is 6-26 mm, the inner diameter of the end with a smaller inner diameter is 0.1-0.3 mm, and the distance from the end with a larger inner diameter to the end with a smaller inner diameter is 2-5 mm.

[0012] In one of the embodiments, the diameter of each electrode rod of the cooling and focusing electrode is 4-6 mm, the length is 27-50 mm, and the size of the entrance end of the ion channel of the cooling and focusing electrode is 3.5-6 mm.

[0013] An ion mobility spectrometer and time-of-flight mass spectrometer comprises an ion mobility spectrometer, a time-of-flight mass spectrometer and a coupling interface structure of the ion mobility spectrometer and the time-of-flight mass spectrometer as described in any of the above embodiments, wherein the ion mobility spectrometer and the time-of-flight mass spectrometer are connected via the coupling interface structure.

[0014] In one embodiment, the inner diameter of the drift tube of the ion mobility spectrometer is larger than the inner diameter of the first through hole, the drift tube and the first through hole are coaxially arranged, and there is a gap between the end of the drift tube and the end of the first through hole.

[0015] The above-mentioned ion migration spectrometer and time-of-flight mass spectrometer and its combined interface structure, compared with the traditional interface structures such as capillaries or pinholes, can solve the problems of low transmission efficiency of tubular interfaces and increased spatial divergence of ions behind the pinhole interface hole. Specifically, the drainage electrode sheet can separate the electric field from the electrode behind; the second through hole in the focusing electrode sheet has a large effective ion receiving area due to the gradual decrease in the inner diameter, and the ions are transmitted under the guidance of the airflow, and the airflow converges, which can effectively improve the transmission efficiency of the ions. During operation, the focusing electrode sheet is contacted with the drainage electrode sheet or the same voltage is applied to form an equipotential structure, so there is no electric field in the second through hole, and the divergent field formed by the gradual decrease in the inner diameter will not cause ion loss; the ions coming out of the second through hole enter the ion channel of the cooling focusing electrode and cool down rapidly. Under the action of the electric field of the quadrupole structure and the collision process with the background gas molecules, the radial energy is reduced and the spatial divergence is reduced, thereby forming a small ion pump, which enters the time-of-flight mass spectrometer, which is conducive to improving the sensitivity of detection, reducing the detection limit, and improving the detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The schematic diagram of the module structure of an ion mobility spectrometer and time-of-flight mass spectrometer according to one embodiment;

[0017] Figure 2 for Figure 1 Schematic diagram of the structure of the interface for coupling ion mobility spectrometry with time-of-flight mass spectrometry, where the dotted line connector indicates the flow direction of the drift gas;

[0018] Figure 3 To adopt Figure 1 The mass spectrum of the reserpine sample with a concentration of 100 pg / μL was obtained by combining ion mobility spectrometry with time-of-flight mass spectrometry;

[0019] Figure 4 This is the mass spectrum of a 20 ng / μL reserpine sample using a traditional pinhole interface ion mobility spectrometer coupled with a time-of-flight mass spectrometer. DETAILED DESCRIPTION

[0020] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0021] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0023] like Figure 1 As shown, an ion mobility spectrometer and time-of-flight mass spectrometer according to an embodiment includes an ion mobility spectrometer 20, a time-of-flight mass spectrometer 30, and a coupling interface structure 10 for the ion mobility spectrometer and the time-of-flight mass spectrometer. The ion mobility spectrometer 20 and the time-of-flight mass spectrometer 30 are connected via the coupling interface structure 10.

[0024] Please combine Figure 2 The interface structure 10 for coupling ion mobility spectrometry and time-of-flight mass spectrometry of this embodiment includes a drain electrode sheet 100, a focusing electrode sheet 200 and a cooling and focusing electrode 300. The drain electrode sheet 100, the focusing electrode sheet 200 and the cooling and focusing electrode 300 are arranged in sequence.

[0025] The drain electrode sheet 100 is provided with a first through hole 102. In this embodiment, the inner diameter of the first through hole 102 is uniform. The inner diameter of the first through hole 102 is slightly smaller than the inner diameter of the drift tube 22 of the ion mobility spectrometer 20. Preferably, the inner diameter of the first through hole 102 is 6 to 26 mm; accordingly, the inner diameter of the drift tube 22 is preferably 8 to 30 mm. The first through hole 102 is coaxially arranged with the drift tube 22 (i.e., the central axis is colinear).

[0026] In this embodiment, the drainage electrode sheet 100 has a main body 110 and a drainage portion 120. The main body 110 is in the shape of a disc. The drainage portion 120 is convexly arranged on the side surface of the main body 110 away from the focusing electrode sheet 200. When installed, it is opposite to the drift tube 22, and there is a gap with the drift tube 22 in the axial direction, such as a gap of 1 to 2 mm. The first through hole 102 passes through the middle of the drainage portion 120 and the main body 110 in sequence. Preferably, the main body 110 and the drainage portion 120 are an integrally formed structure.

[0027] Further, in this embodiment, the angle between the outer wall of the guide portion 120 and the side surface is not less than 90°, preferably 120°. Since the inner diameters of the first through holes 102 are consistent, the thickness of the guide portion 120 gradually decreases from one end connected to the main body 110 to the other end. The guide portion 120 forms a guide structure to guide the drift gas to move toward the drift tube, such as Figure 2 Indicated by the dashed arrow.

[0028] The focusing electrode sheet 200 is provided with a second through hole 202. The inner diameter of the second through hole 202 gradually decreases from one end close to the drainage electrode sheet 100 to the end away from the drainage electrode sheet 100, and the inner diameter of the end with a larger inner diameter of the second through hole 202 is consistent with the inner diameter of the outlet end of the first through hole 102. Preferably, the second through hole 202 is a truncated cone-shaped hole with a uniformly varying inner diameter. The inner diameter of the end with a larger inner diameter of the second through hole 202 is 6 to 26 mm, the inner diameter of the end with a smaller inner diameter is 0.1 to 0.3 mm, and the distance from the end with a larger inner diameter to the end with a smaller inner diameter is 2 to 5 mm. Under the action of the small hole at the outlet end of the truncated cone-shaped second through hole 102, the gas pressure can be reduced from 760 Torr to 0.25 to 2 Torr.

[0029] In the present embodiment, the focusing electrode sheet 200 has a connecting portion 210 and a focusing portion 220. The connecting portion 210 is arranged close to the drainage electrode sheet 100. The connecting portion 210 is in the shape of a disc. The focusing portion 220 is convexly arranged on the surface of the connecting portion 210 on one side away from the drainage electrode sheet 100. The second through hole 202 passes through the middle of the connecting portion 210 and the focusing portion 220 in sequence. Further, in the present embodiment, the thickness of the focusing portion 220 gradually decreases from one end connected to the connecting portion 210 to the other end, forming a giving way structure, which is convenient for docking with the cooling and focusing electrode 300 behind. Preferably, the connecting portion 210 and the focusing portion 220 are an integrally formed structure.

[0030] The connecting portion 210 of the current focusing electrode sheet 200 can be in direct contact with the main body 110 of the current draining electrode sheet 100, so that the current focusing electrode sheet 200 and the current draining electrode sheet 100 are at the same potential; or there is a gap between the connecting portion 210 and the main body 110. When in use, the same voltage is applied to the current focusing electrode sheet 200 and the current draining electrode sheet 100 respectively to form an equipotential structure, so that the electric field is separated from the current focusing electrode sheet 200 located behind it by the current draining electrode sheet 100, and no electric field is formed in the second through hole 202.

[0031] The cooling and focusing electrode 300 is a quadrupole structure, having four cylindrical electrode rods, and an ion channel 302 is formed between the four electrode rods. The entrance end of the ion channel 302 of the cooling and focusing electrode 300 is flush with the end with a smaller inner diameter of the second through hole 202, and the size of the entrance end (the distance between the two electrode rods at the diagonal position) is larger than the inner diameter of the end with a smaller inner diameter of the second through hole 202. The first through hole 102, the second through hole 202 and the ion channel 302 are coaxially arranged (i.e., the central axis of the first through hole 102, the central axis of the second through hole 202 and the central axis of the ion channel 302 are colinear).

[0032] In this embodiment, the diameter of each electrode rod of the cooling and focusing electrode 300 is 4-6 mm, and the length is 27-50 mm. The size of the inlet end of the ion channel 302 of the cooling and focusing electrode 300 is 3.5-6 mm.

[0033] The mass spectrum observed by the ion mobility spectrometer and time-of-flight mass spectrometer of this embodiment is as follows: Figure 3 shown. Figure 3 The signal intensity of the 100pg / μL reserpine sample is 2812, while the spectrum observed using a common pinhole electrode is as follows Figure 4 As shown in FIG. 1 , the signal intensity corresponding to the 20 ng / μL reserpine sample is only 1020, and no signal is observed in the coupling instrument using the capillary interface because the gas phase ions are almost completely lost in the capillary. From the above experimental results, it can be seen that the coupling interface structure of this embodiment can greatly improve the ion transmission efficiency.

[0034] The above-mentioned ion mobility spectrometer and time-of-flight mass spectrometer and its combined interface structure 10, compared with the traditional interface structures such as capillaries or pinholes, can solve the problems of low transmission efficiency of tubular interfaces and increased spatial divergence of ions behind the pinhole interface hole. Specifically, the drainage electrode sheet 100 can separate the electric field from the electrode behind, and can guide the drift gas into the drift tube 22. Since the inner diameter of the second through hole 202 in the focusing electrode sheet 200 is gradually reduced, ions are transmitted under the guidance of the airflow, and have a large effective ion receiving area. In addition, due to the convergence effect on the airflow, the transmission efficiency of ions can be effectively improved. During operation, the focusing electrode sheet 200 is contacted with the drainage electrode sheet 100 or the same voltage is applied to form an equipotential structure, so there is no electric field in the second through hole 202, and the divergence field formed by the gradual reduction of the inner diameter will not cause ion loss. The ions coming out of the second through hole 202 enter the ion channel 302 of the cooling and focusing electrode 300 and are quickly cooled down. Under the action of the electric field of the quadrupole structure and the collision with the background gas molecules, the radial energy is reduced and the spatial divergence is reduced, thereby forming a tiny ion pump and entering the time-of-flight mass spectrometer 30, which is beneficial to improve the detection sensitivity, reduce the detection limit, and improve the detection accuracy.

[0035] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0036] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An ion mobility spectrometer combined with a time-of-flight mass spectrometer, characterized in that: It includes an ion mobility spectrometer, a time-of-flight mass spectrometer, and a coupling interface structure of the ion mobility spectrometer and the time-of-flight mass spectrometer, wherein the ion mobility spectrometer and the time-of-flight mass spectrometer are connected via the coupling interface structure; The combined interface structure includes a drainage electrode sheet, a current collecting electrode sheet and a cooling and focusing electrode, and the drainage electrode sheet, the current collecting electrode sheet and the cooling and focusing electrode are arranged in sequence; wherein the drainage electrode sheet is provided with a first through hole; the current collecting electrode sheet is provided with a second through hole, the inner diameter of the second through hole gradually decreases from one end close to the drainage electrode sheet to one end away from the drainage electrode sheet, and the inner diameter of the end with a larger inner diameter of the second through hole is consistent with the inner diameter of the outlet end of the first through hole; the cooling and focusing electrode is a quadrupole structure, the entrance end of the ion channel of the cooling and focusing electrode is flush with the end with a smaller inner diameter of the second through hole, and the size of the entrance end is larger than the inner diameter of the end with a smaller inner diameter of the second through hole; the first through hole, the second through hole and the ion channel are coaxially arranged; The inner diameter of the drift tube of the ion mobility spectrometer is larger than the inner diameter of the first through hole. The drift tube and the first through hole are coaxially arranged, and there is a gap between the end of the drift tube and the end of the first through hole.

2. The ion mobility spectrometer and time-of-flight mass spectrometer according to claim 1, characterized in that: It is characterized in that The inner diameters of the first through holes are consistent.

3. The ion mobility spectrometer and time-of-flight mass spectrometer according to claim 2, characterized in that: The drainage electrode sheet has a main body and a drainage portion; the drainage portion is protruding on a side surface of the main body away from the focusing electrode sheet, and the angle between the outer wall of the drainage portion and the side surface is not less than 90°; the first through hole passes through the drainage portion and the main body in sequence.

4. The ion mobility spectrometer and time-of-flight mass spectrometer according to claim 3, characterized in that: The inner diameter of the first through hole is 6-26 mm.

5. The ion mobility spectrometer and time-of-flight mass spectrometer according to any one of claims 1 to 4, characterized in that: The second through hole is a truncated cone-shaped hole with a uniformly changing inner diameter.

6. The ion mobility spectrometer and time-of-flight mass spectrometer according to claim 5, characterized in that: The current focusing electrode sheet has a connecting portion and a current focusing portion; the connecting portion is arranged close to the drain electrode sheet, and the current focusing portion is protruding on a side surface of the connecting portion away from the drain electrode sheet; the second through hole passes through the connecting portion and the current focusing portion in sequence.

7. The ion mobility spectrometer and time-of-flight mass spectrometer according to claim 6, characterized in that: The inner diameter of the second through hole at the end with a larger inner diameter is 6-26 mm, the inner diameter of the end with a smaller inner diameter is 0.1-0.3 mm, and the distance from the end with a larger inner diameter to the end with a smaller inner diameter is 2-5 mm.

8. The ion mobility spectrometer and time-of-flight mass spectrometer according to claim 7, characterized in that: The diameter of each electrode rod of the cooling and focusing electrode is 4-6 mm, and the length is 27-50 mm. The size of the entrance end of the ion channel of the cooling and focusing electrode is 3.5-6 mm.

9. The ion mobility spectrometer combined with time-of-flight mass spectrometry according to any one of claims 1 to 4, characterized in that: The distance between the drift tube and the first through hole is 1-2 mm.

10. The ion mobility spectrometer combined with time-of-flight mass spectrometry according to any one of claims 1 to 4, characterized in that: The inner diameter of the drift tube is 8 to 30 mm.

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