An ion funnel device for a mass spectrometer vacuum interface

Abstract

The present invention relates to an ion funnel device for a mass spectrometer vacuum interface, comprising: a sampling capillary, an ion funnel chamber, an ion funnel, a conical baffle, ion guiding rods, and a vacuum chamber. The sampling capillary is installed on the ion funnel chamber, the ion funnel is placed inside the ion funnel chamber, the ion funnel chamber communicates with the vacuum chamber, the ion guiding rods are placed inside the vacuum chamber, the sampling capillary is opposite to the ion channel inlet of the ion funnel, the ion guiding rods are opposite to the ion channel outlet of the ion funnel, the conical baffle is installed inside the ion funnel, and the conical baffle faces the ion channel inlet of the ion funnel. In the present invention, a conical baffle is fixed inside the funnel. Compared with the traditional jet baffle, while blocking neutral particles from entering the mass analyzer, the present invention can also reduce the loss of sample ions, improve the ion transmission efficiency, and thus enhance the sensitivity of the mass spectrometer.

Description

Technical Field

[0001] The present invention relates to the technical field of mass spectrometry analysis, and particularly relates to an ion funnel device for a vacuum interface of a mass spectrometer. Background Art

[0002] Mass spectrometry analysis is an analytical method that ionizes sample molecules and then separates and detects them based on the different trajectories of ions with different mass-to-charge ratios in an electromagnetic field. Currently, it is widely used in many fields such as pharmaceuticals, clinical, environmental monitoring, geology, and biotechnology. The electrospray ionization technique (ESI) has developed rapidly in recent years and has gradually become a frontier direction in the field of mass spectrometry. It ionizes sample molecules in an atmospheric pressure environment, and the ions enter the mass analyzer through the three-stage vacuum of the mass spectrometer. The vacuum interface part serves as the primary vacuum region (vacuum degree is 1 - 10 torr). After the ions enter this region from the atmospheric pressure, jet expansion occurs, and they continuously collide with gas molecules in the environment, causing a large number of ions to undergo random diffusion motion and unable to enter the mass analyzer, resulting in transmission loss and reducing the sensitivity of the instrument.

[0003] As an ion guiding device that has developed rapidly in recent years, the ion funnel consists of a series of annular electrodes with gradually decreasing inner diameters. A DC electric field is applied to all the pole pieces, and an equal-value and opposite-phase RF electric field is applied to adjacent pole pieces, which can achieve efficient focusing and transmission of ions at a vacuum degree of 1 - 10 torr. However, at the same time, neutral particles will also be doped in the sample ions, resulting in an increase in the vacuum degree of the subsequent stage and an increase in the signal noise. In the existing structures, a jet baffle can be added in the middle of the funnel to block the neutral particles, but some ions doped in the neutral particle flow will also be lost, reducing the ion transmission efficiency. Summary of the Invention

[0004] In order to achieve the above-mentioned objects and other advantages of the present invention, the object of the present invention is to provide an ion funnel device for a vacuum interface of a mass spectrometer, including: a sampling capillary, an ion funnel chamber, an ion funnel, a conical baffle, an ion guiding rod, and a vacuum chamber. The sampling capillary is installed on the ion funnel chamber, the ion funnel is placed in the ion funnel chamber, the ion funnel chamber is communicated with the vacuum chamber, the ion guiding rod is placed in the vacuum chamber, the sampling capillary is opposite to the ion channel entrance of the ion funnel, the ion guiding rod is opposite to the ion channel exit of the ion funnel, the conical baffle is installed in the ion funnel, and the conical baffle faces the ion channel entrance of the ion funnel.

[0005] Further, the ion funnel includes a plurality of metal pole pieces, a plurality of insulating sheets, insulating spacers, a base, and a circuit board. The insulating sheets are disposed between adjacent metal pole pieces. The metal pole pieces are provided with holes serving as ion channels. The metal pole pieces and the insulating sheets are fixed on the base. The insulating spacers are disposed between the metal pole pieces and the base. The metal pole pieces are electrically connected to the circuit board. The base is fixed on the ion funnel chamber.

[0006] Further, the metal pole pieces include a plurality of pole pieces with equal diameters and a plurality of pole pieces with equally spaced reduced inner diameters. A plurality of the pole pieces with equal diameters are located at the entrance of the ion channel. A plurality of the pole pieces with equally spaced reduced inner diameters are located at the exit of the ion channel.

[0007] Further, the metal pole pieces are arranged at equal intervals.

[0008] Further, the conical stopper is mounted on the fixing frame of the metal pole piece.

[0009] Further, the metal pole pieces are provided with feed pins, and the circuit board is provided with feed holes. The feed pins on the metal pole pieces are electrically connected to the feed holes at corresponding positions on the circuit board.

[0010] Further, the metal pole pieces and the insulating sheets are provided with mounting holes. The metal pole pieces and the insulating sheets are fixed by the mounting holes and support columns.

[0011] Further, the feed pins on adjacent pole pieces are placed opposite to each other, and the feed pins on the pole pieces are adapted to the feed holes at corresponding positions on the circuit board.

[0012] Further, the circuit board applies radio frequency voltages with equal voltage amplitudes and opposite phases to the feed pins placed opposite to each other.

[0013] Further, a first DC voltage is applied to the entrance pole piece of the ion funnel, a second DC voltage is applied to the exit pole piece of the ion funnel, a third DC voltage is applied to the metal pole piece connected to the conical stopper in the ion funnel, and the intermediate metal pole pieces in the ion funnel apply a DC voltage that decreases arithmetically according to the first DC voltage and the second DC voltage. The intermediate metal pole pieces are the metal pole pieces located between the entrance pole piece and the exit pole piece and not connected to the conical stopper.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] The present invention provides an ion funnel device for a mass spectrometer vacuum interface. A conical baffle is fixed inside the funnel. Compared with the traditional jet baffle, while blocking neutral particles from entering the mass analyzer, the present invention can also reduce the loss of sample ions, improve the ion transmission efficiency, and thus enhance the sensitivity of the mass spectrometer.

[0016] Neutral particles are blocked by the conical baffle and are pumped out in the ion funnel chamber without entering the mass analyzer, which will not affect the vacuum degree of the subsequent area and reduces the requirement of the vacuum system for the pumping speed of the molecular pump.

[0017] The present invention can determine the number of pole pieces and the shape of the baffle according to the actual application scenario, and can be self-assembled into a component to replace the entire vacuum interface part of the mass spectrometer. It is convenient to install and easy to maintain. For the mass spectrometer, the cost increases slightly, but the sensitivity can be greatly improved.

[0018] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and to be implemented in accordance with the content of the specification, the following will be described in detail with reference to the preferred embodiments of the present invention and the accompanying drawings. The specific implementation manners of the present invention are given in detail by the following embodiments and their accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present invention and form a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 Schematic diagram of an ion funnel device for a mass spectrometer vacuum interface in Embodiment 1;

[0021] Figure 2 Schematic diagram of a partial structure of the ion funnel device;

[0022] Figure 3 Schematic diagram of the metal pole piece structure;

[0023] Figure 4 Schematic diagram of the conical baffle pole piece structure;

[0024] Figure 5 Schematic diagram of the ion funnel device circuit;

[0025] Figure 6 Schematic diagram of the conical baffle shape;

[0026] Figure 7 Schematic diagram of the ion funnel device simulation result.

[0027] In the figure: 1. Sampling capillary; 2. Ion funnel chamber; 3. Ion funnel; 31. Inlet pole piece; 311. Hole; 312. Mounting hole; 313. Feed pin; 32. Insulating sheet; 33. The (N1 + 1)-th pole piece; 34. Outlet pole piece; 35. Support column; 36. Insulating spacer; 37. Base; 38. Circuit board; 39. Top fixing screw; 310. Bottom fixing screw; 314. Conical stop pole piece; 3141. Pole piece body; 3142. Fixing bracket; 4. Conical stop; 5. Ion guiding rod; 6. Mechanical pump; 7. Molecular pump; 8. Vacuum chamber. Detailed implementation manners

[0028] Next, in combination with the accompanying drawings and specific implementation manners, the present invention will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined to form new embodiments.

[0029] In subsequent descriptions, suffixes such as "module", "component", or "unit" used to represent elements are only for the convenience of describing the present invention, and they have no specific meaning in themselves. Therefore, "module", "component", or "unit" can be used interchangeably.

[0030] Embodiment 1

[0031] An ion funnel 3 device for a mass spectrometer vacuum interface, as Figure 1 shown, includes: a sampling capillary 1, an ion funnel chamber 2, an ion funnel 3, a conical stop 4, an ion guiding rod 5, and a vacuum chamber 8. The sampling capillary 1 is installed on the ion funnel chamber 2, the ion funnel 3 is placed inside the ion funnel chamber 2, the ion funnel chamber 2 is communicated with the vacuum chamber 8, the ion guiding rod 5 is placed inside the vacuum chamber 8, the sampling capillary 1 is opposite to the ion channel inlet of the ion funnel 3, the ion guiding rod 5 is opposite to the ion channel outlet of the ion funnel 3, the conical stop 4 is installed inside the ion funnel 3, and the conical stop 4 faces the ion channel inlet of the ion funnel 3.

[0032] As Figure 2 、 Figure 3 shown, the ion funnel 3 includes a plurality of metal pole pieces, a plurality of insulating sheets 32, an insulating spacer 36, a base 37, and a circuit board 38. The insulating sheets 32 are placed between adjacent metal pole pieces. The metal pole pieces include a plurality of pole pieces with equal diameters and a plurality of pole pieces with equally spaced decreasing inner diameters. The plurality of pole pieces with equal diameters are located at the ion channel inlet, and the plurality of pole pieces with equally spaced decreasing inner diameters are located at the ion channel outlet. In this embodiment, N stainless steel pole pieces are placed at equal intervals. The first N1 pole pieces starting from the inlet pole piece 31 are pole pieces with equal diameters, with a diameter of d1 and a thickness of T1. From the (N1 + 1)-th piece 33 to the N-th pole piece (i.e., the outlet pole piece 34), the inner diameter decreases at equal intervals. The inner diameter of the N-th pole piece is d2. In the group of pole pieces with equal diameters, the Ns The sheet is a conical baffle plate 314, N s <N1 + 1.

[0033] The shape of the plate is like Figure 3 shown. The pin at the lower left corner is used for power feeding, that is, the power feeding pin 313. Mounting holes 312 for fixing are left at the four corners, and the central circular hole 311 serves as an ion channel. After the overall assembly is completed, as Figure 2 shown. N plates are sleeved on four peek (polyether ether ketone) support columns 35 through the mounting holes 312 at the four corners. A peek insulating sheet 32 with a thickness of T2 is assembled between the plates of each support column 35. The top of the support column 35 is fixed with a top fixing screw 39 to prevent the plate from falling off. The support column 35 passes through the bottom of the insulating spacer 36 and is fixed to the base 37 of the ion funnel 3 with a bottom fixing screw 310. The base 37 of the ion funnel 3 is fixed to the ion funnel chamber 2 with screws.

[0034] As Figure 4 shown, the conical baffle plate 314 includes a plate body 3141 and a fixing frame 3142. The conical baffle 4 is fixed to the plate body 3141 through the fixing frame 3142. In this embodiment, the plate body 3141 and the fixing frame 3142 are of an integral structure. The fixing frame 3142 is a cross-shaped fixing frame, that is, it crosses inside the circular hole of the central ion channel. The conical baffle 4 is fixed in the central area of the cross intersection, as Figure 6 shown. The bottom diameter of the baffle is d and the height is h. The shape of the baffle is not limited to a conical shape and can also be eccentric with respect to the cross intersection center.

[0035] A power feeding pin 313 is provided on the metal plate. A power feeding hole is provided on the circuit board 38. The power feeding pin 313 on the metal plate is electrically connected to the power feeding hole at the corresponding position on the circuit board 38. The power feeding pins 313 on adjacent plates are placed opposite to each other, and the power feeding pin 313 on the plate is adapted to the power feeding hole at the corresponding position on the circuit board 38. In this embodiment, during assembly, the power feeding pins 313 of odd-numbered plates face left, and the power feeding pins 313 of even-numbered plates face right. After all the plates are assembled, the pins are inserted into the corresponding power feeding holes on the circuit board 38 for power feeding.

[0036] In one embodiment, it is set that the ion funnel 3 has a total of 100 stainless steel plates. The first 60 plates have an equal diameter d1 = 50 mm and a thickness T1 = 1 mm. From the 61st plate to the 100th plate, the inner diameter is reduced at equal intervals. The inner diameter of the 100th plate is d2 = 2 mm. Among them, the 34th plate is a conical baffle plate 314 with a bottom diameter d = 2 mm and a height h = 10 mm. The thickness of the insulating gasket between the plates is T2 = 1 mm.

[0037] As Figure 5As shown in the figure, three DC voltages and two RF voltages are applied to the ion funnel 3. When assembling the electrodes of the ion funnel 3, the feeding pins 313 of the odd-numbered electrodes face left, and the feeding pins 313 of the even-numbered electrodes face right. A first RF voltage RF1 is applied to all the feeding pins of the odd-numbered electrodes through the capacitor array of the PCB board, and a second RF voltage RF2 is applied to all the feeding pins of the even-numbered electrodes. The amplitudes of the two RF voltages are equal, and the phases are opposite. The RF peak-to-peak value ranges from 0 to 400V, and the frequency is 1.7 - 1.8MHz. Two DC voltages DC1 are applied to the inlet electrode 31 of the funnel, and DC2 is applied to the outlet electrode 34 of the funnel. The output ranges are both -200V to +200V. In actual applications, to ensure that ions can pass through the funnel area, it is required that DC1 > DC2. The DC voltage is applied to the remaining electrodes (except the conical baffle electrode 314) in an arithmetic progression reduction through resistor voltage division. For example, for the nth electrode, the DC voltage applied to it is V DCn = DC1 - (n - 1)*(DC1 - DC2) / (N - 1). From this, for the odd-numbered electrodes, the applied voltage is V n + RF1, and the voltage applied to the even-numbered electrodes is V n + RF2; for the conical baffle electrode 314, the DC voltage is applied separately through the third DC voltage DC3, and the output range is -200V to +200V. The amplitude set during the actual working process should be slightly higher than the V n calculated at the position of the baffle electrode, which helps the ions to bypass when gradually approaching the baffle and reduces the loss.

[0038] During the actual working process, the sample to be tested enters the ion source to generate charged ions. The ions enter the ion funnel chamber 22 through the sampling capillary 11. Here, a primary vacuum is provided by the mechanical pump 6, and the vacuum degree is approximately 1 - 10 torr. The RF electric field applied to the electrodes confines the ions in the funnel. As the inner diameter of the electrodes gradually decreases, the ions are continuously focused. The DC electric field provides the ions with the energy to move forward axially. The voltage on the baffle is higher than the voltage of the surrounding electrodes. During the axial movement of the ions, as they approach the baffle, they will deflect under the action of the electric field and bypass the conical baffle 4. The simulation results are as shown in Figure 7 the figure. The neutral particles that enter the chamber together with the ions will hit the conical baffle 4, disperse to both sides, and are finally pumped out by the mechanical pump 6. They will not enter the subsequent mass analyzer and will not affect the vacuum degree of the subsequent area, reducing the requirement for the pumping speed of the molecular pump 7 by the vacuum system. The charged ions are continuously focused after bypassing the conical baffle 4 under the action of the electric field and finally flow out of the funnel and enter the ion guide rod 5, and then enter the mass analyzer. Compared with the traditional baffle, the present invention can reduce ion loss while blocking neutral particles, improve the ion transmission efficiency, and thus improve the sensitivity of the mass spectrometer.

[0039] The above is only for the embodiments of this specification and is not intended to limit one or more embodiments of this specification. For those skilled in the art, one or more embodiments of this specification may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of one or more embodiments of this specification shall be included within the scope of the claims of one or more embodiments of this specification. One or more embodiments of this specification, one or more embodiments of this specification, one or more embodiments of this specification, one or more embodiments of this specification.

Claims

1. An ion funnel device for a mass spectrometer vacuum interface, characterized in that, Comprising: An injection capillary, an ion funnel chamber, an ion funnel, a conical baffle, an ion guiding rod, and a vacuum chamber. The injection capillary is installed on the ion funnel chamber, the ion funnel is placed inside the ion funnel chamber, the ion funnel chamber communicates with the vacuum chamber, the ion guiding rod is placed inside the vacuum chamber, the injection capillary is opposite to the ion channel inlet of the ion funnel, the ion guiding rod is opposite to the ion channel outlet of the ion funnel, the conical baffle is installed inside the ion funnel, and the conical baffle faces the ion channel inlet of the ion funnel; The ion funnel includes a plurality of metal pole pieces, a plurality of insulating sheets, insulating spacers, a base, and a circuit board. The insulating sheets are placed between adjacent metal pole pieces. The metal pole pieces are provided with holes serving as ion channels. The metal pole pieces and the insulating sheets are fixed on the base. The insulating spacers are placed between the metal pole pieces and the base. The metal pole pieces are electrically connected to the circuit board. The base is fixed on the ion funnel chamber; The conical baffle is installed on the fixing frame of the metal pole piece; The metal pole pieces are provided with feeding pins, and the circuit board is provided with feeding holes. The feeding pins on the metal pole pieces are electrically connected to the feeding holes at corresponding positions on the circuit board; The feeding pins on adjacent pole pieces are placed opposite to each other, and the feeding pins on the pole pieces are adapted to the feeding holes at corresponding positions on the circuit board; The circuit board applies radio frequency voltages with equal voltage amplitudes and opposite phases to the feeding pins placed opposite to each other; A first DC voltage is applied to the inlet pole piece of the ion funnel, a second DC voltage is applied to the outlet pole piece of the ion funnel, a third DC voltage is applied to the metal pole piece connected to the conical baffle in the ion funnel, and the intermediate metal pole pieces of the ion funnel apply DC voltages that decrease arithmetically according to the first DC voltage and the second DC voltage. The intermediate metal pole pieces are the metal pole pieces located between the inlet pole piece and the outlet pole piece and not connected to the conical baffle.

2. The ion funnel device for a mass spectrometer vacuum interface according to claim 1, wherein: The metal pole pieces include a plurality of pole pieces with equal diameters and a plurality of pole pieces with equally spaced decreasing inner diameters. A plurality of the pole pieces with equal diameters are located at the ion channel inlet, and a plurality of the pole pieces with equally spaced decreasing inner diameters are located at the ion channel outlet.

3. An ion funnel device for a mass spectrometer vacuum interface according to claim 1, characterized in that: The metal pole pieces are placed at equal intervals.

4. An ion funnel device for a mass spectrometer vacuum interface according to claim 1, characterized in that: The metal pole pieces and the insulating sheets are provided with mounting holes, and the metal pole pieces and the insulating sheets are fixed through the mounting holes and support columns.

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