GC-IMS (Gas Chromatography-IP Multimedia Subsystem) combined interface device for separating dopant from sample

Abstract

The invention relates to a GC-IMS (Gas Chromatography-IP Multimedia Subsystem) coupling interface device for separating dopant from a sample. The GC-IMS coupling interface device mainly comprises a gas chromatograph, a chromatographic column joint, an ion migration tube, a three-way valve, a dopant device and the like. The chromatographic column connector is vertically connected to the ion migration tube, an inclined air hole and a transverse air hole in the chromatographic column connector and a connector center air hole are all formed in the ion migration tube, a connector dot inlet is connected with the three-way valve, and the capillary tube penetrates through the chromatographic column connector and can be connected into a reaction area of the ion migration tube. According to the invention, ion migration tube dopant addition and sample introduction can be separated, so that dilution of dopant carrier gas to a sample is reduced, and effective separation of reaction ion generation and ionization is realized; whether dopant is added or not is controlled, and the photoionization mode of the migration tube with the VUV lamp as an ionization source is changed; the sample injection efficiency can be adjusted by adjusting the insertion depth of the capillary tube.

Description

Technical Field

[0001] The invention relates to the technical field of GC-IMS coupling, and in particular to a GC-IMS coupling interface device for separating dopant from a sample. Background Art

[0002] Ion mobility spectrometry (IMS) was originally developed to detect chemical warfare agents and illegal drugs in the military field, but it was soon realized that IMS was also suitable for a variety of civilian applications, mainly health assessment, safety testing, food quality and spoilage, product identification and authenticity assessment, etc. Ion mobility spectrometry is used in conjunction with chromatography to combine the high accuracy, wide dynamic concentration range and high selectivity of GC with the high sensitivity, portability and fast detection speed of IMS. GC-IMS can accurately distinguish volatile substances based on size, weight and molecular shape.

[0003] The process of GC-IMS measurement is as follows: the sample is pre-separated according to its ability to adsorb and desorb to the inner surface of the chromatographic column. After pre-separation, the analyte will enter the IMS, be ionized through proton transfer reactions, etc., and be separated and detected under the action of the electric field. The most difficult part of GC-IMS coupling is the matching of the GC injection volume and the migration spectrum flow rate, which is mainly related to the design of the GC-IMS coupling interface.

[0004] Regarding the GC-IMS coupling interface, the existing technical situation is as follows: In the technical solution disclosed in patent CN202311714070.9, the chromatographic column is vertically connected to the ion migration tube through the interface to realize the switching between the barrel-shaped and sheet-shaped ionization sources, but the chromatographic effluent is seriously affected by the floating gas and has low sensitivity; Patents CN202121343049.9 and CN202110669990.8 disclose the interface connection between the needle-shaped injection cannula and the ion mobility spectrometer. The connection between the capillary and the injection cannula of this structure has a non-zero dead volume, which will cause The deformation of the chromatogram; in the technical solution disclosed in patent CN202222372181.3, the sample gas flowing out of the chromatographic column first passes through the sample gas passage to enter the coupling interface and then enters the ion source, and the gas in the sample gas passage will dilute the sample gas, thereby reducing the detection sensitivity; in the technical solution disclosed in patent CN201920282908.4, the interface adopts a Z-shaped flow path, and the light source irradiates the gas flow path. Although the contact time between the light source and the sample is prolonged, the chromatographic resolution will be seriously reduced, and the separated substances will be mixed again in the Z-shaped gas path. In the technical solution disclosed in patent CN201310741366.X, the chromatographic effluent is divided into two migration tube reaction zones, which will reduce the detection sensitivity; in the technical solution disclosed in patent CN202111589494.8, the electromagnetic valve switching interface is used to realize the single and dual mode switching injection of GC-IMS and MS, which will cause a large dead volume in the interface part, affecting the peak shape.

[0005] In summary, the solutions for GC-IMS coupling interface in the prior art all have certain defects and shortcomings, and there is still room for further improvement and perfection. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a GC-IMS coupling interface device for separating dopant from sample, which can separate the addition of dopant to the ion migration tube from the sample injection to reduce the dilution of the sample by the dopant carrier gas, thereby achieving an effective separation of reaction ion generation and ionization; and control the presence or absence of dopant addition to achieve a change in the photoionization mode of the migration tube with a VUV lamp as the ionization source, thereby effectively solving the problem of sample dilution caused by dopant addition.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The invention provides a GC-IMS interface device for separating dopant from sample, comprising a chromatographic column oven, a chromatographic column connector, a capillary, an ion gate, an ion transfer tube, an ion source, a three-way valve and a dopant device; the ion source is arranged at the front end of the ion transfer tube; the ion gate is arranged at the rear side of the ion transfer tube; a central air hole is arranged inside the chromatographic column connector; an oblique air hole is arranged on the left side of the head of the chromatographic column connector, and a transverse air hole is arranged on the right side, and both the oblique air hole and the transverse air hole are connected to the central air hole; the chromatographic column connector is vertically connected to the ion transfer tube. The capillary is arranged in the middle of the side wall, and its head is located inside the ion migration tube, and its tail is located outside the ion migration tube; the capillary is correspondingly arranged in the central air hole of the chromatographic column joint, and its outlet is connected with the inside of the ion migration tube, and the inlet is connected with the chromatographic column oven through the chromatographic column joint; a dopant inlet connected with the oblique air hole is arranged on one side of the tail of the chromatographic column joint; one port of the three-way valve is used for emptying, and the other two ports are respectively connected to the dopant device and the dopant inlet; an air outlet is arranged on the side wall of the ion migration tube close to the ionization source, and an air inlet is arranged on the side wall close to the ion gate.

[0009] Furthermore, the chromatographic column connector is always in a heat-insulating state, thereby reducing sample residue.

[0010] Furthermore, the three-way valve is electrically regulated or manually regulated.

[0011] Furthermore, the capillary is a gas phase capillary, which is composed of a capillary column, an MCC column and a preparative column.

[0012] Furthermore, the ion gate is a BN type ion gate or a TP type ion gate or a field switching ion gate.

[0013] Furthermore, the chromatographic column connector is a hollow T-shaped structure.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention can separate the dopant addition of the ion migration tube from the sample injection to reduce the dilution of the sample by the dopant carrier gas, realize the effective separation of the generation of reactive ions and the reaction ionization with the reagent ions, improve the ionization efficiency, utilize the interface ionization source to first ionize the dopant to generate the reactant ions, and then the reactant ions are ionized with the sample reagent to realize efficient ionization and improve the sensitivity. Adjusting the depth of the capillary insertion can adjust whether the chromatographic effluent converges with the dopant carrier gas in advance, thereby changing the ionization efficiency and the reaction mode. Under the action of the three-way valve, the device enables the migration tube with a VUV lamp as the ionization source to realize the addition of dopant, realize the change of the photoionization mode, or other ionization sources to realize the addition of dopant, realize the material masking, enhancement or conversion of plasma chemical detection. And the device has the advantages of simple structure, practicality and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0017] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0018] Figure 3 This is a schematic diagram of the structure of Embodiment 3 of the present invention;

[0019] Figure 4 This is a schematic diagram of the structure of Example 4 of the present invention.

[0020] Among them, the figure markings are: 1-chromatographic column oven; 2-chromatographic column connector; 3-capillary; 4-lateral pore; 5-ion gate; 6-ion migration tube; 7-capillary outlet; 8-central pore; 9-oblique pore; 10-ionization source; 11-migration tube outlet; 12-migration tube inlet; 13-dopant inlet; 14-three-way valve; 15-dopant device. DETAILED DESCRIPTION

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] It should be noted that, in the description of the present invention, the terms "up", "down", "top", "bottom", "one side", "the other side", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device or element must have a specific orientation, be constructed and operated in a specific orientation.

[0023] The GC-IMS interface device for separating dopant from sample proposed in the present invention comprises a gas chromatograph, a chromatographic column oven 1, a chromatographic column connector 2, a capillary 3, an ion gate 5, an ion migration tube 6, an ion source 10, a three-way valve 14 and a dopant device 15. The gas chromatograph comprises a chromatographic column oven 1 and a capillary 3.

[0024] The ion source 10 is coaxially arranged at the front end of the ion transfer tube 6, and the ion gate 5 is correspondingly arranged at the inner rear side of the ion transfer tube 6. The ion gate 5 is a BN type ion gate, a TP type ion gate or a field switching ion gate.

[0025] The chromatographic column connector 2 is a hollow T-shaped structure, and a through central air hole 8 is arranged inside it; an oblique air hole 9 is arranged on the left side of the head of the chromatographic column connector 2, and a transverse air hole 4 is arranged on the right side of the head of the chromatographic column connector 2, and the inner sides of the oblique air hole 9 and the transverse air hole 4 are both connected to the central air hole 8 and intersect at the central air hole 8; the chromatographic column connector 2 is vertically connected to the middle of the side wall of the ion migration tube 6, and the head of the chromatographic column connector 2 is located inside the ion migration tube 6, that is, the outlet ends of the oblique air hole 9, the transverse air hole 4 of the connector and the central air hole 8 of the connector are all located inside the ion migration tube 6; the tail of the chromatographic column connector 2 is located outside the side wall of the ion migration tube 6. Among them, the chromatographic column connector 2 is always in a heat preservation state to reduce sample residue.

[0026] The capillary 3 is correspondingly arranged in the central pore 8 of the chromatographic column connector 2, and the capillary outlet 7 is connected to the internal reaction zone of the ion migration tube 6. One end of the chromatographic column oven 1 is connected to the carrier gas, and the other end is inserted into the tail of the chromatographic column connector 2 and connected to the inlet of the capillary 3, which is used to heat the capillary 3. The capillary outlet 7 is located above or below the intersection of the oblique pore 9 and the transverse pore 4. Among them, the capillary 3 is a gas phase capillary, which is composed of a capillary column, an MCC column and a preparation column.

[0027] A dopant inlet 13 is arranged on the left side of the tail of the chromatographic column connector 2; one port of the three-way valve 14 is used for emptying, and the other two ports are respectively connected to the dopant device 15 and the dopant inlet 13; the three-way valve 14 is electrically regulated or manually regulated; a migration tube air outlet 11 is arranged on the side wall of the ion migration tube 6 close to the ionization source 10, and an air inlet 12 is arranged on the side wall close to the ion gate 5.

[0028] The dopant device 15 is a device for generating chemical doping substances, one port of which is connected to a dopant carrier gas, so that the volatilized dopant can be blown out of the device.

[0029] The capillary 3 in the chromatographic column connector 2 is in a heated state, and the analyte is gradually separated under the action of the carrier gas. By adjusting the position of the capillary outlet 7, different injection efficiencies are changed. If the capillary outlet 7 is located at or below the intersection of the oblique pores 9 and the transverse pores 4, the floating gas flow will first pass through the transverse pores 4, and then flow out from the oblique pores 9 and the central pores 8, so that the chromatographic eluate will first merge with the dopant carrier gas. If the capillary outlet 7 is located above the intersection of the oblique pores 9 and the transverse pores 4, it is directly connected to the ion transfer tube 6, and the chromatographic eluate cannot be merged with the dopant carrier gas in advance, so that the separation of dopant and sample is achieved, and there will be a reaction ion generation and separation effect of the reagent molecule ionization, thereby changing the ionization efficiency.

[0030] Under the action of the dopant carrier gas and the control of the three-way valve 14, the gas can be emptied or blown toward the ionization source 10 through the oblique air hole 9 of the chromatographic column connector 2. For the VUV lamp ionization source, SPI ionization is achieved when there is no dopant, and CI ionization is achieved when there is a dopant. For other types of ionization sources, it can be achieved with or without dopant addition to achieve material masking, enhancement or conversion plasma chemical detection.

[0031] The detection method of the present invention is further described below by means of specific embodiments:

[0032] Example 1

[0033] like Figure 1 As shown, in the GC-IMS interface device for separating dopant and sample proposed in this embodiment, the ionization source 10 and the ion transfer tube 6 are coaxially arranged.

[0034] For the VUV lamp ionization source, when the ionization energy of the sample molecule is lower than the photon energy, the three-way valve 14 is adjusted to select emptying, without dopants, and the direct photoionization (SPI) mode is adopted. The chromatographic column oven 1 is operated to make the capillary 3 in a heated state. The analytes are gradually separated under the action of the carrier gas. At this time, the capillary outlet 7 is located above the intersection of the oblique air hole 9 of the joint and the transverse air hole 4 of the joint, and is directly connected to the inside of the ion migration tube 6. By adjusting the position of the capillary outlet 7, different injection efficiencies are changed. After optimizing the insertion depth, the sample flowing out of the capillary outlet 7 flows out from the migration tube outlet 11 under the purge of the floating gas to complete the detection.

[0035] Example 2

[0036] like Figure 2As shown, in the GC-IMS interface device for separating dopant and sample proposed in this embodiment, the ionization source 10 and the ion transfer tube 6 are coaxially arranged.

[0037] For the VUV lamp ionization source, when the ionization energy of the sample molecule is lower than the photon energy, the three-way valve 14 is adjusted to select emptying, no dopant, and direct photoionization (SPI) mode is adopted. The chromatographic column oven 1 works to make the capillary 3 in a heated state. The analytes are gradually separated under the action of the carrier gas. At this time, the capillary outlet 7 is located at the intersection of the oblique pore 9 and the transverse pore 4 (or below). The drift gas flow will first pass through the transverse pore 4, and then flow out from the oblique pore 9 and the central pore 8. Finally, the sample flows out from the ion migration tube outlet 11 under the drift gas purge to complete the detection.

[0038] Example 3

[0039] like Figure 3 As shown, in the GC-IMS interface device for separating dopant and sample proposed in this embodiment, the ionization source 10 and the ion transfer tube 6 are coaxially arranged.

[0040] For the VUV lamp ionization source, when the ionization energy of the sample molecule is higher than the photon energy, the chemical ionization (CI) mode is used, and the dopant carrier gas is blown to the ionization source 10 through the oblique air hole 9 by adjusting the three-way valve 14, and the chromatographic eluate cannot be merged with the dopant carrier gas in advance, so as to achieve the separation of dopant and sample, and the reaction ion produces the effect of separation from the ionization of the reagent molecule, thereby changing the ionization efficiency. The chromatographic column oven 1 is working, so that the capillary 3 is in a heated state, and the analyte is gradually separated under the action of the carrier gas. At this time, the capillary outlet 7 is located above the intersection of the oblique air hole 9 and the transverse air hole 4, and is directly connected to the ion transfer tube 6. By adjusting the position of the capillary outlet 7, different injection efficiencies are changed. After optimizing the insertion depth, the chromatographic eluate will enter the ion transfer tube 6, and finally flow out from the transfer tube outlet 11 with the dopant carrier gas to complete the detection.

[0041] Example 4

[0042] like Figure 4 As shown, in the GC-IMS interface device for separating dopant and sample proposed in this embodiment, the ionization source 10 and the ion transfer tube 6 are coaxially arranged.

[0043] For the VUV lamp ionization source, when the ionization energy of the sample molecule is higher than the photon energy, the chemical ionization (CI) mode is used. The three-way valve 14 is adjusted to allow the dopant carrier gas to be blown toward the ionization source 10 through the oblique air holes of the chromatographic column joint. The chromatographic column oven 1 is operated to place the capillary 3 in a heated state. The analyte is gradually separated under the action of the carrier gas. At this time, the capillary outlet 7 is located at or below the intersection of the oblique air holes 9 and the transverse air holes 4. The floating gas flow will first pass through the transverse air holes 4, and then flow out from the oblique air holes 9 and the central air holes 8. In this way, the chromatographic eluate will first merge with the dopant carrier gas, and then enter the ion migration tube 6, and finally flow out from the migration tube outlet 11 with the dopant carrier gas to complete the detection.

[0044] Matters not covered in the present invention are all known technologies.

[0045] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A GC-IMS interface device for separation of dopant and sample, characterized in that: The device comprises a chromatographic column oven, a chromatographic column connector, a capillary, an ion gate, an ion transfer tube, an ion source, a three-way valve and a dopant device; the ion source is arranged at the front end of the ion transfer tube; the ion gate is arranged at the rear side of the ion transfer tube; a central air hole is arranged inside the chromatographic column connector; an oblique air hole is arranged on the left side of the head of the chromatographic column connector, and a transverse air hole is arranged on the right side, and the oblique air hole and the transverse air hole are both connected to the central air hole; the chromatographic column connector is vertically connected to the middle part of the side wall of the ion transfer tube, and its head is located at the ion transfer tube. The capillary is arranged in the central air hole of the chromatographic column joint, and its outlet is connected with the inside of the ion migration tube, and the inlet is connected with the chromatographic column oven through the chromatographic column joint; a dopant inlet connected with the oblique air hole is arranged on one side of the tail of the chromatographic column joint; one port of the three-way valve is used for emptying, and the other two ports are respectively connected with the dopant device and the dopant inlet; an air outlet is arranged on the side wall of the ion migration tube close to the ionization source, and an air inlet is arranged on the side wall close to the ion gate.

2. The GC-IMS interface device for separation of dopant and sample according to claim 1, characterized in that: The chromatographic column joint is always in a heat-insulating state, thereby reducing sample residue.

3. The GC-IMS interface device for separation of dopant and sample according to claim 1, characterized in that: The three-way valve is electrically regulated or manually regulated.

4. The GC-IMS interface device for separation of dopant and sample according to claim 1, characterized in that: The capillary is a gas phase capillary, which is composed of a capillary column, an MCC column and a preparation column.

5. The GC-IMS interface device for separation of dopant and sample according to claim 1, characterized in that: The ion gate is a BN type ion gate, a TP type ion gate or a field switching ion gate.

6. The GC-IMS interface device for separation of dopant and sample according to claim 1, characterized in that: The chromatographic column joint is a hollow T-shaped structure.

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