An integrated sample injection ion mobility spectrometer

Abstract

The present invention discloses an integrated sample-injection ion mobility spectrometer, and specifically relates to an integrated structure of sample-injection and detector of an ion mobility spectrometer. The technical scheme is based on the photoionization ion mobility spectrometer technology. Usually, the ion mobility spectrometer includes an external sample-injection device, an ion migration tube detector, a chemical dopant device, a signal receiving and conversion device, a high-voltage module, a control system device, and a gas circulation system. The ion migration spectrometer in the present invention is an ion migration spectrometer device that integrates a sample-injection device and an ion migration tube detector into one module. The device can realize the direct introduction of target sample molecules into the central ionization region of the ion migration tube photoionization source, and efficiently and quickly ionize to produce corresponding product ions; the product ions are accelerated by the electric field and decelerated after collision with neutral atmospheric molecules to obtain a constant average speed; different product ions have different average speeds due to their different charge-to-mass ratios, spatial structures and collision cross sections, so they are separated after passing through a section of the electric field and arrive at the collecting electrode one after another, thereby completing the entire detection process.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analyzer devices, in particular to an ion migration spectrum analyzer with an ion migration tube detector and no external sample injection device. Background Art

[0002] Ion Mobility Spectrometry (IMS) is a separation and detection technology that appeared in the 1970s. Compared with traditional mass spectrometry and chromatography instruments, it has the characteristics of simple structure, high sensitivity, fast analysis speed and reliable results. Ion mobility spectrometry is mainly composed of an injector, an ion migration tube detector and a PC control system. Usually, the injector vaporizes the sample and transmits it to the detector, where the sample gas is ionized to produce molecules and ions. Driven by the electric field, the ions enter the drift region through the periodically opened ion gate. In the process of continuous collision with the countercurrent neutral drift gas molecules, the different ions are separated due to the different migration rates of these ions in the electric field, and arrive at the collecting electrode one after another for detection. Therefore, the presence of the target substance can be determined by the migration time, and the concentration of the corresponding substance can be determined by the peak area or peak height. It is worth noting that due to the differences in chemical properties such as ionization energy, proton affinity, and electronegativity of different compounds, the efficiency and selectivity of producing positive and negative polarity ions when they are ionized in the atmospheric pressure ionization source are different.

[0003] In order to reduce traditional 63 The Ni ionization source poses a risk of radioactive contamination during application. Currently, the design of the ionization source in most detection systems uses a non-radioactive photoionization source. In the design of the atmospheric pressure photoionization source, the ionization efficiency and selectivity are improved by adding a dopant to the ionization source. The photons emitted by the photoionization source ionize high-concentration Dopant (such as acetone, butanone) molecules, generating a large number of photoelectrons and Dopant positive ions. In the atmospheric environment, these photoelectrons and dopant positive ions can produce reagent ions of different positive and negative polarities through a series of ion-molecule reactions. Subsequently, these reagent ions are effectively ionized with the sample molecules to be tested through chemical ionization reactions, generating characteristic ions of different polarities, and finally separated and detected according to the different mobilities through a dual-mode ion migration tube.

[0004] The injector is an essential component used in the multifunctional ion mobility spectrometer rapid detector. Its performance directly determines the injection efficiency and the overall performance of the ion mobility spectrometer. The existing ion mobility spectrometer thermal desorption injectors have two modes: motor drive and electromagnetic drive. The heating is mostly heated by the temperature control of the heating rod. The heating temperature belongs to the constant temperature control mode. The heating time depends on the power of the heating rod. The current use time range is 10-30min. The heating is relatively slow, and the energy consumption is relatively high for the instrument. At present, there are authorized patents 201220459129.5, a combined multifunctional injector for ion mobility spectrometry; 201210563261.5, a halogen lamp injector for thermal desorption injection; 201721139511.7, a gradient thermal desorption injector, etc.; because the injector has heat loss and transmission efficiency problems, it has always restricted the sensitivity of sample analysis and detection.

[0005] PerkinElmer Health Sciences Co., Ltd. and others invented an automatic sample injector, an automatic loader, and a system and device using the same (patent number ZL 201690000959.8). The automatic sample injector may include a support member, and the automatic sample injector may also include: a motor. The automatic sample injector is used in conjunction with a chromatographic device, involving multiple groups of functional modules, and the structure is very complex.

[0006] A sampling device for a mass spectrometer invented by Li Xueli et al. (patent number ZL202020809474.1) includes a base, a fixing part and a dropper, wherein the upper end face of the base is connected to the bottom end of the mass spectrometer, a slot for installing a support plate is provided on the side of the base close to the mass spectrometer sampling port, a limit groove for installing a fixing part is provided on the upper end face of the support plate, one end of the support plate is movably inserted in the slot, and a groove for assembling a connector is provided on the end of the support plate away from the base, and two groups of grooves are provided in parallel, and an adjusting rod and a suction cup are also provided in the groove; the fixing part is connected to the top plate through a support rod, and a fixing plate for installing a screw rod is fixedly connected to one end of the upper end face of the top plate, and the screw rod passes through the fixing plate and is rotatably connected to the movable plate, and a push plate is fixedly connected to the side of the movable plate away from the screw rod, and the push plate is slidably connected to the top plate. The sampling device of the mass spectrometer is reasonably designed, easy to use, and has the advantage of being easy to sample. The structure in the present invention is not suitable for analyzing some samples that are corrosive to materials.

[0007] Yi Zengbao et al. invented a sampling device for a gas chromatography-mass spectrometry instrument (patent number ZL201922376717.7), including a gas chromatography-mass spectrometry instrument body, vertical columns on both sides of the top of the gas chromatography-mass spectrometry instrument body, an upper top plate welded to the top of the columns, a sliding mounting plate slidably connected to the columns, the sliding mounting plate is arranged parallel to the bottom of the upper top plate, and both sides of the sliding mounting plate are penetrated by the columns, and the beneficial effect is: a sliding mounting plate is provided in the utility model, a quantitative tube is fixed on the sliding mounting plate, and the volume of the quantitative tube is the same as that of the detection tube. When sampling, the quantitative tube first moves vertically upward to fill the inside of the quantitative tube, and then moves vertically downward to pour the internal solution into the detection tube, and so on. Compared with traditional technology, this device greatly improves the sampling efficiency of the detection liquid, and the quantitative filling is controlled by electric equipment throughout the process, without manual labor, which greatly reduces the labor intensity of the operator. The complex components in the present invention are prone to cause the memory effect of sample residue. Summary of the invention

[0008] The technical problem to be solved by the present invention is that conventional sample injectors have low sample transmission efficiency and large heat loss, which affects sample ionization efficiency and detection and analysis sensitivity.

[0009] Specific content includes:

[0010] An integrated sample injection ion mobility spectrometer is an ion mobility spectrometer based on VUV light ionization, including an integrated ion migration tube with integrated sample injection function, a chemical additive device, a signal receiving and conversion device, a high-voltage module, a control system device and a gas circulation system.

[0011] The sample analysis process is described as follows: the liquid sample is directly sent to the ionization zone of the ion migration tube through a micro-injector, the sample is directly thermally ionized in front of the VUV light window, and then carried by the circulating gas through the periodically opened ion gate into the migration zone for separation and analysis.

[0012] There are three through holes on the ionization zone of the ion transfer tube near the VUV light ionization source, which are the outlet port of the ion transfer tube connected to the vacuum pump; the port for connecting the chemical dopant; and the sample inlet of the ion transfer tube. These three through holes and the floating gas inlet together form the gas circulation system of the ion transfer tube; the outlet port of the ion transfer tube is connected to the vacuum pump as the gas outlet of the ion transfer tube, and the rest are gas inlets.

[0013] There is no need to connect the injector separately. Insert the reducing insulating inner sleeve into the sample injection port of the ion transfer tube. The outer diameter "r1" of the reducing insulating inner sleeve is less than or equal to the inner diameter "r2" of the sample injection port of the ion transfer tube, that is, r1≤r2 (r1 and r2 satisfy 4mm≤r2≤6mm, and the difference between r2 and r1 is less than 0.1mm). When r1<r2, the gap between the two can realize the function of pumping and replenishing air into the transfer tube, thereby reducing the sample airflow.

[0014] 1-2 grooves are provided on the outer wall surface of the tube from the bottom edge (7-1) of the cone of the variable diameter insulating inner sleeve to the first-step table top, and the radial cross-sectional area of ​​the grooves gradually decreases from the lower bottom edge to the upper bottom edge of the cone, the width is less than 0.2mm, and the depth is less than 0.2mm; when the vacuum pump is working, the grooves can also realize the air replenishment function.

[0015] The reducing insulating inner sleeve is a stepped reducing structure; the uppermost layer is a truncated cone ferrule structure (hollow) viewed longitudinally, which can fix the sleeve to the migration tube and support the micro-injector; the stepped reducing structure below the truncated cone can be 1-2 steps, and the inner diameter of the bottom is 0.5-1.0mm; any step table is a circular table, and the size difference between the large semicircle and the small semicircle of the circular ring is between 0.25-1.0mm; the sleeve material is made of non-metallic insulating materials such as PG, polytetrafluoroethylene or high-temperature resistant rubber.

[0016] The length of the variable-diameter insulating inner sleeve is 4-6 cm, one end of which is the port of the sample inlet (a truncated cone ferrule structure), and the other end is inserted just at the center point of the irradiation area of ​​the VUV light ionization window cross section;

[0017] The center point high efficiency ionization injection range refers to the ionization zone set in the ion transfer tube. The axial distance between the lamp window and the ion gate is set to "L". The injection is within the range of 1 / 2-5 / 6L from one side of the lamp window and above the central axis of the lamp window. The height is less than the radius "R" of the circular lamp window.

[0018] The solid or liquid sample is diluted with an organic solvent and the purified liquid phase is placed in a micro-injector. The front end of the micro-injector is inserted into a reducing insulating inner sleeve and the sample is pushed out. The sample is then enriched at the bottom of the reducing sleeve and continuously vaporized under the action of the hot carrier gas in the ionization zone to produce efficient thermal ionization.

[0019] A truncated cone-shaped sleeve is provided at the connection between the micro-injector needle and the micro-injector cylinder. The depth of inserting different micro-injectors into the ion migration tube can be adjusted by the height of the truncated cone-shaped sleeve.

[0020] After the solid or liquid sample is diluted with an organic solvent, it must be filtered through different types of filter membranes for sample pretreatment. The pore size of the microporous filter membrane is 0.22μm, and the sample volume injected by the microinjector is between 1-5μl.

[0021] This device can directly introduce the target sample molecules into the central ionization zone of the ion transfer tube photoionization source, and efficiently and quickly ionize them to produce corresponding product ions; the product ions are accelerated by the electric field and decelerated after collision with neutral atmospheric molecules to obtain a constant average speed; different product ions have different average speeds due to their different charge-to-mass ratios, spatial structures and collision cross-sections, so they are separated after passing through a period of electric field and arrive at the collecting electrode one after another, thus completing the entire detection process.

[0022] Advantages of the invention

[0023] 1. In conventional ion mobility spectrometers, the sample is vaporized and then transferred to the central ionization zone of the ion migration tube. The low transfer efficiency affects the sensitivity of the analyzer. The ion mobility spectrometer injector of the present invention is integrated with the ion migration tube to avoid the influence of the sample transfer efficiency.

[0024] 2. The sample thermal analysis process of the present invention utilizes part of the heat of the ion transfer tube, which can save energy. The sample is enriched at the bottom of the reducer (in the ionization zone of the transfer tube), and under the action of the hot carrier gas in the ionization zone, it is continuously vaporized to produce efficient thermal ionization. This avoids the sample being completely vaporized and causing a sample residual memory effect on the transfer tube.

[0025] 3. The insulating inner sleeve in the present invention adopts a step-change diameter technology, which can change the airflow in the circulating field of the detector, which is beneficial to reduce the dilution gas, increase the sample injection concentration, and improve the sensitivity of sample detection and analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 a is a schematic diagram of an integrated sample injection ion mobility spectrometer.

[0027] Figure 1 In a, 1 is a VUV light ionization source; 2 is an ion transfer tube ionization region; 3 is an ion transfer tube migration region; 4 is an ion transfer tube outlet interface connected to a vacuum pump; 5 is an interface connected to a chemical dopant; 6 is an ion transfer tube sample inlet tube; 7 is a variable diameter insulating inner sleeve; 8 is a floating gas inlet; 9 is a micro-injector; 10 is an amplifier; 11 is an A / D converter; 12 is a data processing system; and 13 is an ion gate.

[0028] Figure 1 b is a schematic diagram of the stepped structure of the variable diameter inner casing.

[0029] Figure 1 In b, the left and right figures are the first-order and second-order stepped reducing insulating inner sleeves respectively; 7-1 is the upper frustum structure of the inner sleeve; 7-2 is the first-order table top; 7-3 is the second-order table top.

[0030] Figure 2The invention discloses an integrated sample injection ion mobility spectrometer which utilizes a variable diameter insulating inner sleeve to enhance the ion mobility spectrum of RIP.

[0031] Figure 3 An integrated sample injection ion mobility spectrometer detects the propofol ion mobility spectrum.

[0032] Figure 4 Schematic diagram of a dopant cartridge device, in which: 51 is a dopant cartridge (such as Figure 4 Left, Figure C), 52 is the dopant gas air source inlet, 53 is the dopant gas outlet, 54 is a PTFE tube, 55 is a sample bottle (such as Figure 4 Left, D), 56 is the chemical doping agent acetone. DETAILED DESCRIPTION

[0033] The ion migration spectrometer used in the following embodiments of the present invention has the following structure: the ion migration tube is a VUV light ionization source, the cross-sectional radius of the circular lamp window is 6 mm, and it includes a coaxial cylindrical ionization zone and a cylindrical migration zone, the length of the ionization zone is 25 mm, and the inner diameter is 20 mm; the length of the migration zone is 90 mm, and the inner diameter is 25 mm. An ion gate is provided between the ionization zone and the migration zone, and a photoionization source is provided on the side of the ionization zone away from the ion gate; an ion migration tube sample inlet 6 is provided on the outer wall of the ion migration tube in the ionization zone;

[0034] A variable diameter insulating inner sleeve 7 is inserted into the sample injection port 6 of the ion transfer tube, one end of the variable diameter insulating inner sleeve 7 is located in the ionization zone of the ion transfer tube, and the other end is located outside the ion transfer tube;

[0035] The variable-diameter insulating inner sleeve 7 is a hollow structure with a stepped inner diameter; the inner diameter of the other end located outside the ion transfer tube is larger than the inner diameter of the end located in the ionization zone.

[0036] The number of steps or steps of the inner diameter stepped diameter-changing structure is 1, and the hollow tube with two open ends is formed by sealingly connecting one open end of one hollow tube in two hollow tubes with two open ends of different inner diameters with the end face of one open end of the other hollow tube, the two hollow tubes are coaxial, and the annular surface formed at the connection of the two hollow tubes in the hollow tube is the stepped table surface, and the stepped table surface is perpendicular to the axis of the hollow tube; the hollow tube with a large inner diameter is arranged at the other end outside the ion transfer tube, and the hollow tube with a small inner diameter is arranged at one end of the ionization zone;

[0037] The inner diameter of the variable-diameter insulating inner sleeve 7 at one end in the ionization zone is 0.8 mm, the radial width of the stepped terrace is 0.35 mm, and the inner diameter of the other end outside the ion transfer tube is 1.5 mm.

[0038] The ionization region and the migration region are both coaxial cylindrical, with their axial center lines placed parallel to the horizontal plane, and the injection port 6 is located in the upper middle part of the ion migration tube;

[0039] Insert a variable diameter insulating inner sleeve 7 into the sample injection port 6 of the ion transfer tube. The stepped reduced diameter step table in the variable diameter insulating inner sleeve can be used as a storage table for all or part of the liquid injection sample. When the ion transfer tube liquid injection sample is injected, the liquid injection sample can be dripped onto the stepped table, and then the injection port 6 is connected to the carrier gas source, and the injection port 6 does not need to be connected to an injector separately.

[0040] The injection port 6 is a circular through hole, and the variable-diameter insulating inner sleeve 7 is a circular tube. The outer diameter "r1" of the variable-diameter insulating inner sleeve 7 is less than or equal to the inner diameter "r2" of the ion migration tube sample injection port 6, that is, r1≤r2, r1 and r2 satisfy r2=5mm, and the difference between r2 and r1 is 0.05mm; the gap between the two can realize the function of pumping and replenishing air into the migration tube, reducing the sample airflow. A hollow annular inverted frustum-shaped protrusion is provided in the radial direction on the outer wall surface of the other end of the variable-diameter insulating inner sleeve 7 located outside the ion migration tube. The cross-section of the protrusion along the axial direction of the variable-diameter insulating inner sleeve is two symmetrical right-angled triangles with the axis of the variable-diameter insulating inner sleeve as the symmetry axis. One radial right-angled side A of the triangle is located on the side away from the ion migration tube, and the vertex A corresponding to the right-angled side A is located on the side close to the ion migration tube. The other right-angled side of the triangle is parallel to the axis of the variable-diameter insulating inner sleeve; the length of the right-angled side A is greater than the difference between r2 and r1;

[0041] A groove is provided on the outer wall surface of the annular inverted frustum-shaped protrusion along the axial direction (from the lower base of the frustum to the upper base), and the radial cross-sectional area of ​​the groove gradually decreases from the right-angled side A to the vertex A (i.e. from the lower base of the frustum to the upper base), the width of the groove on the radial cross-section is 0.15mm, and the depth of the groove is 0.10mm; when the vacuum pump is working, the groove can also realize the air replenishing function.

[0042] The ion transfer tube includes a photoionization source (such as a VUV light ionization source) and a Faraday disk, which are arranged opposite to each other at the left and right ends, and an ion gate located between the photoionization source and the Faraday disk. The area between the photoionization source and the ion gate is the ionization area, and the area between the ion gate and the Faraday disk is the transfer area.

[0043] Three through holes are arranged in sequence on the outer wall of the ion transfer tube from the side of the ionization zone near the photoionization source to the side of the ion gate, which are respectively an ion transfer tube outlet interface 4 for connecting to a vacuum pump, an interface 5 for connecting to a chemical dopant, and an ion transfer tube sample inlet 6; these three through holes and a floating gas inlet 8 arranged on the outer wall of the ion transfer tube in the migration zone near the ion detector together constitute the external interface of the gas circulation system of the ion transfer tube; the ion transfer tube outlet interface 4 is connected to the vacuum pump inlet as the ion transfer tube gas outlet, and the rest are gas inlets.

[0044] The material of the variable-diameter insulating inner sleeve 7 is polytetrafluoroethylene.

[0045] The length of the variable diameter insulating inner sleeve 7 is 6 cm, one end of which is located outside the ion migration tube and serves as a port for the sample injection port, and the insertion position of the other end of the port in the ionization zone is just located in the area between the cylindrical light path (light irradiation area) emitted by the circular light window of the photoionization source, close to one side of the variable diameter insulating inner sleeve and the central axis; the radius of the cylindrical light path is equal to the radius of the circular light window of the photoionization source (such as: VUV lamp), and the radius of the cylindrical ionization zone is 1.5 times the radius of the light window.

[0046] The axial distance between the photoionization source lamp window and the ion gate is set to "L", and the axial position of the other end of the variable diameter insulating inner sleeve 7 in the ionization zone in the ion transfer tube is 18 / 25L away from the photoionization source lamp window, and the radial position is at the central axis of the light path emitted by the lamp window. In the embodiment, the axial distance "L" between the lamp window and the ion gate is 25mm, and the center point injection position is at the 18mm point.

[0047] A liquid sample, or a liquid phase extracted after a solid sample is diluted with an organic solvent, or a liquid phase extracted after a liquid sample is dissolved with an organic solvent is used as a liquid injection sample. The liquid injection sample is loaded into a syringe barrel with a syringe needle. The injection needle outlet is inserted into a variable-diameter insulating inner sleeve and the sample in the syringe barrel is pushed out. The sample is then enriched on the step surface in the variable-diameter insulating inner sleeve and, under the action of the carrier gas, continuously vaporized in the ionization zone to generate efficient thermal ionization.

[0048] Before loading the liquid sample into the micro-injector, it must be filtered through a filter membrane for pre-treatment. The pore size of the micro-filter membrane is 0.22 μm. The amount of sample injected into the variable-diameter insulating inner sleeve by the micro-injector is 3 μl.

[0049] Photoionization ion mobility spectrometer, three through-hole tubes near the ionization zone of the VUV lamp are respectively connected to the outlet port 4 of the ion migration tube for the vacuum pump; the interface 5 for the chemical dopant; and the sample inlet port 6 of the ion migration tube. In the embodiment, the floating gas (air) flow rate of the ion migration tube is 600sccm, the vacuum pump vacuum flow rate is 850sccm, the dopant gas (with air as carrier gas) flow rate is 50sccm, and the sample carrier gas (air) is 200sccm. The temperature control of the ion migration tube is set at 100°C, and the ion gate opening time is set at 50μs.

[0050] The ion transfer tube is connected to a chemical dopant interface 5 through a pipeline with a dopant cartridge device (such as Figure 4 ) is connected, the dopant cartridge device comprises a cylindrical dopant cartridge (such as Figure 4Left, Figure C), the outer wall surface of the upper open end of the dopant cylinder 51 has an external thread, and a cylindrical sealing cover with an internal thread and an open lower end and a closed upper end is screwed on the upper open end of the dopant cylinder. The upper open end of the dopant cylinder is sealed by the sealing cover, and a lower through hole is provided on the lower side wall surface of the circular dopant cylinder as a dopant gas air source inlet 52 connected to the air source, and an upper through hole is provided on the upper side wall surface of the circular dopant cylinder as a dopant gas outlet 53 connected to the chemical dopant (dopant) interface 5 through a conduit, and a hollow and sealed sample bottle (such as Figure 4 Left, D), a chemical dopant acetone 56 is installed in the sample bottle, and a (outer diameter φ4) PTFE tube 54 is inserted at the top of the sample bottle 55. The upper open end of the PTFE tube 54 is in the dopant tube, and the lower open end is above the liquid level of the chemical dopant acetone in the sample bottle; the sample dopant gas (air) purge flow rate is 50sccm. Acetone evaporates through the PTFE tube through the hole on the upper cover of the sample bottle, and in the dopant tube device, the acetone volatile vapor is diluted by air and purged into the ion transfer tube.

[0051] Example 1

[0052] Using the ion mobility spectrometer in the embodiment of the present invention, the parameters are set according to the above specific embodiment; the following comparative test is performed under the above conditions:

[0053] (1) The first group of ion transfer tube sample injection port tubes 6 were not inserted with a variable diameter insulating inner sleeve (as a comparative example), that is, the sample carrier gas was directly introduced into the ion transfer tube sample injection port 6 (inner diameter r2 = 5 mm); the acetone reagent ion peak in the test air (such as Figure 2 , thick line curve A), the strongest peak of the signal is 1800mv.

[0054] (2) The sample inlet tube 6 of the second group of ion transfer tubes is inserted into the above-mentioned variable diameter insulating inner sleeve, that is, the first-order structure variable diameter insulating inner sleeve in the above-mentioned embodiment, and the sample carrier gas is introduced through the variable diameter insulating inner sleeve; when the amount of acetone released is the same, the signal when there is a variable diameter sleeve is 3800mv, (such as Figure 2 , thin line curve B), the signal is enhanced 2.1 times compared with the first group; the increased ion concentration of acetone reagent is conducive to the detection of target samples.

[0055] In the ion mobility spectrometer sampling method of this embodiment, the sample is directly sent to the ionization zone of the ion mobility tube without an external sample injector device, and the transmission efficiency is high. The sample transmission efficiency can reach 100%.

[0056] Example 2

[0057] The propofol methanol solution was prepared in sequence by the serial dilution method, and sample concentrations of 5, 0.5, and 0.1 ng / μl were used in this experiment.

[0058] Using the ion mobility spectrometer in the embodiment of the present invention, the parameters are set according to the above specific embodiment; the following comparative test is performed:

[0059] (1) The first group used the above-mentioned ion mobility spectrometer of the present invention, and placed a syringe in the variable diameter insulating inner sleeve to inject 3 μl of propofol in 5 ng / μl methanol. Figure 3 As shown, the propofol monomer peaks are at 5.040ms and 5.365ms, and the maximum signal intensity at 5.365ms is 250mv. According to the rule of recognizing 3 times the noise of the calculation instrument as a signal, the lowest actual measurable value is 0.1ng / μl.

[0060] (2) The second group used a conventional thermal desorption injector ion mobility spectrometer (as a comparative example) and introduced 3 μl and 5 ng / μl propofol in methanol. The same injection method and calculation method as the first group were used, and the lowest actual detection value was 0.5 ng / μl. The comparison shows that the detection sensitivity of the injection device (first group) in the present invention can be increased by 5 times.

[0061] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. An ion transfer tube, comprising an ionization region and a transfer region, an ion gate being arranged between the ionization region and the transfer region, and a photoionization source being arranged on a side of the ionization region away from the ion gate; an ion transfer tube sample inlet (6) being arranged on an outer wall surface of the ion transfer tube in the ionization region; Features: A variable diameter insulating inner sleeve (7) is inserted into the sample injection port (6) of the ion transfer tube, one end of the variable diameter insulating inner sleeve (7) is located in the ionization region of the ion transfer tube, and the other end is located outside the ion transfer tube; The variable-diameter insulating inner sleeve (7) is hollow and has a stepped inner diameter variable structure; the inner diameter of the other end located outside the ion transfer tube is larger than the inner diameter of the end located in the ionization region; The inner diameter of the variable diameter insulating inner sleeve (7) at one end of the ionization zone is 0.5-1.0 mm, the radial width of the stepped table is 0.25-1.0 mm, and the stepped stepped table in the variable diameter insulating inner sleeve can be used as a storage table for all or part of the liquid injection sample.

2. The ion transfer tube according to claim 1, characterized in that: The number of steps of the inner diameter stepped diameter reducing structure is 1 or 2; When the number of steps is 1, the variable-diameter insulating inner sleeve (7) is a hollow tube with two open ends formed by sealingly connecting the open end of one of two open-ended hollow tubes with different inner diameters to the end face of the other open end, and the annular surface formed at the connection between the two hollow tubes in the hollow tube is the stepped table surface, and the stepped table surface is perpendicular to the axis of the hollow tube; the hollow tube with a larger inner diameter is arranged at the other end outside the ion transfer tube, and the hollow tube with a smaller inner diameter is arranged at one end of the ionization zone; When the number of steps is 2, the variable-diameter insulating inner sleeve (7) is a hollow tube with two ends open, which is formed by three hollow tubes with different inner diameters having two ends open and the end faces of the open ends are connected in order from large to small in inner diameter. The two annular surfaces formed at the connection between two adjacent hollow tubes of the three hollow tubes in the hollow tube are step terraces, and the step terraces are perpendicular to the axis of the hollow tube; the hollow tube with a large inner diameter is arranged at the other end outside the ion migration tube, and the hollow tube with a small inner diameter is arranged at one end of the ionization zone.

3. The ion transfer tube according to claim 1 or 2, characterized in that: The ionization region and the migration region are both coaxial cylindrical, with their axial center lines placed parallel to the horizontal plane, and the injection port (6) is located in the upper middle part of the ion migration tube; Insert a variable diameter insulating inner sleeve (7) into the sample injection port (6) of the ion transfer tube, and the stepped reduced diameter step table inside the variable diameter insulating inner sleeve serves as a storage table for all or part of the liquid injection sample. When injecting the liquid injection sample into the ion transfer tube, the liquid injection sample is dripped onto the stepped table, and then the injection port (6) is connected to the carrier gas source, and the injection port (6) does not need to be connected to an injector separately; The injection port (6) is a circular through hole, the variable diameter insulating inner sleeve (7) is a circular tube, the outer diameter "r1" of the variable diameter insulating inner sleeve (7) is less than or equal to the inner diameter "r2" of the ion migration tube sample injection port (6), that is, r1≤r2, r1 and r2 satisfy 4mm≤r2≤6mm, and the difference between r2 and r1 is less than 0.1mm; when r1<r2, the gap between the two can realize the function of pumping and replenishing air into the migration tube, thereby reducing the sample airflow.

4. The ion transfer tube according to claim 3, characterized in that: A hollow annular inverted truncated cone-shaped protrusion is provided in the radial direction on the outer wall surface of the other end of the variable-diameter insulating inner sleeve (7) located outside the ion transfer tube, and the cross-section of the protrusion along the axial direction of the variable-diameter insulating inner sleeve is two symmetrical right-angled triangles with the axis of the variable-diameter insulating inner sleeve as the symmetry axis, a right-angled side A of the triangle in the radial direction is located on the side away from the ion transfer tube, and the vertex A corresponding to the right-angled side A is located on the side close to the ion transfer tube, and the other right-angled side of the triangle is parallel to the axis of the variable-diameter insulating inner sleeve; the length of the right-angled side A is greater than the difference between r2 and r1; One or two grooves are provided on the outer wall surface of the annular inverted frustum-shaped protrusion along the axial direction, that is, from the lower base of the frustum to the upper base. The radial cross-sectional area of ​​the groove gradually decreases from the right-angled side A to the vertex A, that is, from the lower base to the upper base of the frustum. The width of the groove on the radial cross-section is less than 0.2 mm, and the depth of the groove is less than 0.2 mm. When the vacuum pump is working, the groove can also realize the air replenishment function.

5. The ion transfer tube according to any one of claims 1 to 4, characterized in that: The ion transfer tube includes a photoionization source and a Faraday plate which are arranged opposite to each other at the left and right ends, and an ion gate located between the photoionization source and the Faraday plate. The area between the photoionization source and the ion gate is the ionization area, and the area between the ion gate and the Faraday plate is the transfer area. Three through holes are sequentially arranged on the outer wall of the ion transfer tube from the side of the ionization region close to the photoionization source to the side of the ion gate, which are respectively an ion transfer tube gas outlet interface (4) for connecting to a vacuum pump, an interface (5) for connecting to a chemical dopant, and an ion transfer tube sample inlet (6); these three through holes and a floating gas inlet (8) arranged on the outer wall of the ion transfer tube from the side of the migration region close to the ion detector together form an external interface of the gas circulation system of the ion transfer tube; the ion transfer tube gas outlet interface (4) is connected to the vacuum pump gas inlet as the ion transfer tube gas outlet, and the rest are gas inlets.

6. The ion transfer tube according to any one of claims 1 to 4, characterized in that: The material of the variable diameter insulating inner sleeve (7) is one or more non-metallic insulating materials such as PG, polytetrafluoroethylene or high temperature resistant rubber. The high temperature resistance specifically means that it can withstand a high temperature of 120-150°C or above without any change in physical and chemical properties.

7. The ion transfer tube according to any one of claims 1 to 4, characterized in that: The length of the variable diameter insulating inner sleeve (7) is 4-6 cm, one end of which is located outside the ion transfer tube and serves as a sample injection port, and the insertion position of the other end of the port located in the ionization zone is just located in the area between the cylindrical light path emitted by the circular light window of the photoionization source and the side surface of the variable diameter insulating inner sleeve and the central axis; the radius of the cylindrical light path is equal to the radius of the circular light window of the photoionization source, and the radius of the cylindrical ionization zone is between 1 and 2 times the radius of the light window.

8. The ion transfer tube according to claim 7, characterized in that: The axial distance between the photoionization source lamp window and the ion gate is set to "L", the axial position of the other end port of the variable diameter insulating inner sleeve (7) in the ionization zone in the ion transfer tube is within the range of 1 / 2-5 / 6L from the photoionization source lamp window, and the radial position is within the range of the central axis of the light path emitted by the lamp window to less than or equal to the radius "R" of the circular lamp window.

9. The ion transfer tube according to any one of claims 1 to 4, characterized in that: A liquid sample, or a liquid phase extracted after a solid sample is diluted with an organic solvent, or a liquid phase extracted after a liquid sample is dissolved with an organic solvent is used as a liquid injection sample. The liquid injection sample is loaded into a micro-injector, and a reducing insulating inner sleeve is inserted into the front outlet of the micro-injector to push out the sample in the micro-injector. Subsequently, the sample is enriched on the stepped surface in the reducing insulating inner sleeve, and under the action of the carrier gas, it is continuously gasified in the ionization zone to generate efficient thermal ionization; Before loading the liquid sample into the micro-injector, it must be filtered through a filter membrane for pre-treatment. The pore size of the micro-filter membrane is 0.22 μm. The amount of sample injected into the variable-diameter insulating inner sleeve by the micro-injector is between 1-5 μl.

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