Mass spectrometer

Abstract

The present invention relates to the technical field of mass spectrometers, and provides a mass spectrometer, comprising: a first vacuum chamber, having an atmospheric pressure interface connected to an external atmospheric pressure environment, and connected to a first vacuum pump, wherein the working pressure P1 of the first vacuum chamber is in the range of P1>30 mbar; a second vacuum chamber, connected to the first vacuum chamber by a vacuum interface to receive an analyte from the first vacuum chamber, the second vacuum chamber is connected to a second vacuum pump, and the working pressure P2 of the second vacuum chamber is in the range of 0.5 mbar≤P2≤30 mbar; and a third vacuum chamber, connected to the second vacuum chamber by a vacuum interface to receive an analyte from the second vacuum chamber, the third vacuum chamber is connected to a third vacuum pump, the first vacuum pump or the second vacuum pump is used as a pre-pump of the third vacuum pump, and through a multi-stage vacuum chamber design combined with the working pressure design of each stage of the vacuum chamber, the sensitivity of the mass spectrometer is ensured while the miniaturization design of the mass spectrometer is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of mass spectrometers, and in particular to a mass spectrometer capable of achieving both instrument performance and miniaturization. Background Art

[0002] A mass spectrometer with an atmospheric pressure ionization (API) ion source utilizes an inlet connected to the ion source to allow ions generated at atmospheric pressure (AP) to enter the mass analyzer. Conventional mass analyzers are generally not able to operate at atmospheric pressure or near atmospheric pressure, and most commercial mass analyzers operate at pressures P in the range of P ≤ 0.001 mbar.

[0003] The sensitivity of a mass spectrometer is one of the key performance indicators, which is closely related to the gas flow rate entering the system. On the one hand, if the ions are transferred directly from the atmospheric pressure environment to the vacuum chamber containing the mass analyzer, the injection port needs to be made very small, which will result in a very small number of ions transmitted to the vacuum chamber, thereby limiting the sensitivity of the instrument. On the other hand, because the vacuum chamber containing the mass analyzer needs to be maintained at a relatively low gas pressure, according to Q=SP (where Q is the gas flow rate, S is the pumping speed of the pump, and P is the gas pressure), a pump with a relatively high pumping speed is required to achieve both a relatively low gas pressure and a relatively high flow rate. However, a vacuum pump with a relatively high pumping speed is also relatively large in size, which is not conducive to the miniaturization of the mass spectrometer.

[0004] Microsaic disclosed a mass spectrometer with a three-stage vacuum structure in its British patent GB2483314B. The latter two stages require two 4800L / min molecular pumps to pump two cavities respectively, and a diaphragm pump is required as a molecular pre-pump and another diaphragm pump to pump the first stage. The cost and volume of the pump system are relatively high.

[0005] In its British patent GB2520785B, WATERS disclosed a compact mass spectrometer with a three-stage vacuum structure, in which the air pressure in the first-stage vacuum chamber is less than 10 mbar, and a radio frequency ion guide device is provided in the first-stage vacuum chamber. Since the first vacuum chamber is connected to the external environment, this air pressure range will place high requirements on the pumping speed of the pump connected to the first-stage vacuum chamber, hindering the miniaturization of the pump system.

[0006] Therefore, in the miniaturized design of mass spectrometers based on the existing technology, a part of the sensitivity will be sacrificed, or methods such as discontinuous sampling will be used to adapt to the decrease in pumping speed. There is a lack of technical solutions that can solve these problems at the same time. Summary of the invention

[0007] The present invention is proposed to solve the above technical problems, and aims to provide a mass spectrometer that reduces the pumping speed requirement while maintaining the system air intake flow rate, thereby ensuring sensitivity.

[0008] The mass spectrometer provided by the present invention includes: a first vacuum chamber, having an atmospheric pressure interface connected to an external atmospheric pressure environment and connected to a first vacuum pump, the working pressure P1 of the first vacuum chamber being in the range of P1>30mbar; a second vacuum chamber, connected to the first vacuum chamber by a vacuum interface to receive an analyte from the first vacuum chamber, the second vacuum chamber being connected to a second vacuum pump, the working pressure P2 of the second vacuum chamber being in the range of 0.5mbar≤P2≤30mbar; and a third vacuum chamber, connected to the second vacuum chamber by a vacuum interface to receive an analyte from the second vacuum chamber, the third vacuum chamber being connected to a third vacuum pump, and the first vacuum pump or the second vacuum pump being used as a pre-pump of the third vacuum pump.

[0009] Because the third vacuum chamber is not directly connected to the atmospheric pressure environment, but uses the first vacuum chamber and the second vacuum chamber as a transition to be indirectly connected to the atmospheric environment, the air pressure in the third vacuum chamber used to provide a relatively high vacuum environment will not or will rarely restrict the flux of gas inflow, and at the same time can improve the operating stability of some devices with higher vacuum requirements, such as mass analyzers.

[0010] Since the first vacuum chamber is directly connected to the atmospheric pressure environment. Compared with the prior art, the air pressure of the first vacuum chamber is configured in a higher air pressure environment of P1>30mbar. Under this air pressure environment, the atmospheric pressure interface can complete the introduction of samples or ions with a higher flow rate using a rough vacuum pump with a low pumping speed. The volume of a rough vacuum pump with a low pumping speed can be very small and does not occupy too much volume. If it is necessary to increase the volume of the fore-stage vacuum pump of the secondary vacuum system, in order to achieve the same effect of increasing the system air intake, the required increase in the volume of the fore-stage vacuum pump is much greater than the volume of the additional rough vacuum pump with a low pumping speed. Therefore, the mass spectrometer provided by the present invention can obtain a larger increase in the system air intake through a smaller increase in the pump volume, making it possible to take into account both miniaturization and high sensitivity.

[0011] The working pressure P2 of the second vacuum chamber is in the range of 0.5mbar≤P2≤30mbar. First, the working pressure greater than or equal to 0.5mbar can be achieved by a rough vacuum pump, so there is no need to equip the second vacuum chamber with a turbomolecular pump separately, which facilitates the miniaturization of the second vacuum pump and reduces the cost of the device. Secondly, the air pressure range of less than or equal to 30mbar can provide air pressure conditions for the arrangement and stable operation of some ion focusing devices, such as radio frequency focusing devices, in the second vacuum chamber, so that even if there is a high air pressure difference between the second vacuum chamber and the first vacuum chamber, the ion beam can still maintain focus and be transmitted to the third vacuum chamber, and is not easy to expand and lose due to the existence of the air pressure difference. The ions are controlled by the ion focusing device to be transported to the lower vacuum chamber, reducing the influence of airflow interference on the transport process, so that the injection of the lower vacuum chamber is not restricted or less restricted by the flux size of the airflow inflow, which facilitates the miniaturization of the vacuum pump of the lower vacuum chamber.

[0012] In the above manner, the range of the working pressure P1 of the first vacuum chamber is set so that the pumping speed of the first vacuum pump and the aperture range of the atmospheric pressure interface can obtain a suitable matching relationship. On the one hand, the first vacuum pump is allowed to select a rough vacuum pump with a lower pumping speed and smaller volume to reduce the volume of the first vacuum pump. On the other hand, it can allow the use of an atmospheric pressure interface with a larger flow rate to improve the sensitivity of the mass spectrometer. At the same time, the working pressure of the second vacuum chamber can also be achieved by using a rough vacuum pump, thereby reducing the use of a turbomolecular pump, simplifying the design of the pump system as a whole, and facilitating the miniaturization of the mass spectrometer.

[0013] In a preferred technical solution of the present invention, both the first vacuum pump and the second vacuum pump are rough vacuum pumps. The use of rough vacuum pumps can effectively reduce the volumes of the first vacuum pump and the second vacuum pump.

[0014] In a preferred technical solution of the present invention, the range of the pumping speed S1 of the first vacuum pump is one of the following ranges: S1≤1L / min or S1≤2L / min or S1≤3L / min or S1≤4L / min or S1≤5L / min. It should be noted that, in this article, the pumping speeds S1 and S2 refer to the maximum pumping speeds that the corresponding vacuum pump products can reach, for example, the nominal pumping speed of the vacuum pump, which is related to the volume of the vacuum pump.

[0015] In this technical solution, because the working gas pressure of the first vacuum chamber is relatively high, even if the gas flow rate is relatively large, a rough vacuum pump with a low pumping speed can be used to meet the vacuum requirement. Since the pumping speed S1 of the first vacuum pump is relatively low, a rough vacuum pump with a relatively small volume can be selected to pump the first vacuum chamber, thereby miniaturizing the pump system of the mass spectrometer.

[0016] In a preferred technical solution of the present invention, the pumping speed S2 of the second vacuum pump is in one of the following ranges: S2≤10L / min or S2≤20L / min or S2≤30L / min or S2≤40L / min or S2≤50L / min.

[0017] In this technical solution, the working gas pressure of the second vacuum chamber is relatively high. Therefore, accordingly, the second vacuum pump can also use a smaller rough vacuum pump. Compared with the high-pumping-speed turbomolecular pump selected for the second vacuum chamber of the mass spectrometer with a multi-stage vacuum chamber in the prior art, it has the advantages of a simple pump system and low cost.

[0018] In a preferred technical solution of the present invention, an electrostatic focusing unit or an aerodynamic focusing unit is provided in the first vacuum chamber for focusing ions in the airflow entering the first vacuum chamber from the atmospheric pressure interface onto a path for transmission to the second vacuum chamber.

[0019] Because an electrostatic focusing unit or an aerodynamic focusing unit is provided in the first vacuum chamber, the ions are focused during the transmission process in the first vacuum chamber. Therefore, even if the airflow expands due to the change in air pressure, the ion beam can still be focused and transmitted in the axial direction. Therefore, a vacuum interface with a smaller aperture can be selected to reduce the gas flow entering the second vacuum chamber, and the loss of ions caused by the reduction in aperture can be compensated to a certain extent by focusing. Therefore, under the premise that the flux of the required gas inflow is reduced, even if the air pressure of P2 is smaller than that of P1, a rough vacuum pump with a lower pumping speed can still be used to meet the vacuum degree and flux requirements of the second vacuum chamber, thereby facilitating the miniaturization of the pump system and the mass spectrometer. In addition, by using a rough vacuum pump to evacuate, the air pressure range of the first vacuum chamber can provide a suitable air pressure environment for the electrostatic focusing unit or the aerodynamic focusing unit, ensuring that the electrostatic focusing unit or the aerodynamic focusing unit can operate stably.

[0020] In a preferred technical solution of the present invention, a radio frequency ion guide device is provided in the second vacuum chamber. The air pressure condition in the second vacuum chamber can ensure the normal operation of the radio frequency ion guide device, and the radio frequency ion guide device can constrain ions along the ion transmission path to reduce the loss of ions during the transmission process.

[0021] In the preferred technical solution of the present invention, the atmospheric pressure interface is a capillary, a cylindrical hole or a conical hole. The capillary, cylindrical hole or conical hole as the atmospheric pressure interface can continuously introduce sample gas carrying ions from the external atmospheric pressure environment, and limit the gas flow rate to a reasonable range by using the aperture size.

[0022] In the preferred technical solution of the present invention, the vacuum interface is a cylindrical hole, a conical hole or a combination thereof. Using a cylindrical hole or a conical hole as a vacuum interface can, on the one hand, maintain the relative independence of the vacuum environment of each chamber and limit the gas flow entering the next vacuum chamber; on the other hand, the hole can allow ions to pass through and maintain the stable delivery of the ion beam.

[0023] In a preferred technical solution of the present invention, the third vacuum pump is a turbomolecular pump, and a mass analyzer is arranged in the third vacuum chamber. The turbomolecular pump has a compact structure, is usually air-cooled, can be installed in any direction, and can obtain a high vacuum degree. A small or medium-sized turbomolecular pump can allow a high pre-pumping pressure, so a rough vacuum pump can be used as a pre-pumping pump of the turbomolecular pump, as a combination, to provide a stable high vacuum environment for the third vacuum chamber where the mass analyzer is located.

[0024] In a preferred technical solution of the present invention, the mass analyzer is a quadrupole mass analyzer or an ion trap mass analyzer. The quadrupole mass analyzer or the ion trap mass analyzer is small in size and can work normally in a relatively low vacuum environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a partial structural schematic diagram of a mass spectrometer in Embodiment 1 of the present invention;

[0026] Figure 2 is a schematic structural diagram of a mass spectrometer in a second embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the vacuum system structure of a large mass spectrometer in the prior art;

[0028] Figure 4 It is a schematic diagram of the vacuum system structure of a small mass spectrometer in the prior art;

[0029] Figure 5 It is a schematic diagram of the vacuum system structure of a mass spectrometer in one embodiment of the present invention.

[0030] Description of reference numerals:

[0031] 1-first vacuum chamber, 11-atmospheric pressure interface, 12-ion focusing unit; 2-second vacuum chamber, 21-vacuum interface, 22-radio frequency ion guide device; 3-third vacuum chamber, 31-vacuum interface, 32-mass analyzer; 4-first vacuum pump; 5-second vacuum pump; 6-third vacuum pump; 7-ion detector; 8-ion source. DETAILED DESCRIPTION

[0032] Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, but includes various changes, substitutions, and modifications within the technical scope of the present disclosure.

[0033] Implementation Method 1

[0034] The sensitivity of the mass spectrometer is closely related to the gas flow rate entering the system, and the gas flow rate is determined by the working gas pressure of the vacuum chamber and the pumping speed of the vacuum pump. Taking the first vacuum chamber 1 as an example, when the pumping speed of the first vacuum pump 4 is relatively high, it is allowed to set the aperture of the atmospheric pressure interface 11 to be relatively large, so that the amount of ions passing through the aperture is relatively large, thereby improving the sensitivity of the mass spectrometer. On the other hand, the pumping speed of the vacuum pump is closely related to the volume of the vacuum pump. When the pumping speed of the vacuum pump is relatively high, its volume also increases accordingly, which will be detrimental to the miniaturization of the mass spectrometer. Therefore, the present embodiment aims to provide a mass spectrometer that can take into account both instrument sensitivity and miniaturization.

[0035] like Figure 1 As shown, the mass spectrometer provided in this embodiment includes: a first vacuum chamber 1, having an atmospheric pressure interface 11 connected to an external atmospheric pressure environment, and connected to a first vacuum pump 4, the working pressure P1 of the first vacuum chamber 1 is in the range of P1>30mbar; a second vacuum chamber 2, connected to the first vacuum chamber 1 by a vacuum interface 21 to receive the analyte from the first vacuum chamber 1, the second vacuum chamber 2 is connected to a second vacuum pump 5, the working pressure P2 of the second vacuum chamber 2 is in the range of 0.5mbar≤P2≤30mbar; and a third vacuum chamber 3, connected to the second vacuum chamber 2 by a vacuum interface 31 to receive the analyte from the second vacuum chamber 2, the third vacuum chamber 3 is connected to a third vacuum pump 6, and the first vacuum pump 4 or the second vacuum pump 5 is used as a pre-pump for the third vacuum pump 6.

[0036] In the present embodiment, because the third vacuum chamber 3 is not directly connected to the atmospheric pressure environment, but indirectly connected to the atmospheric environment by using the first vacuum chamber 1 and the second vacuum chamber 2 as transitions, the air pressure of the third vacuum chamber 3 for providing a relatively high vacuum environment will not or will rarely restrict the flux of gas inflow, and can also improve the operating stability of some devices with high vacuum requirements, such as mass analyzers.

[0037] The gas pressure of the first vacuum chamber 1 is configured in a relatively high gas pressure environment of P1>30mbar. Under this gas pressure environment, the atmospheric pressure interface 11 can complete the introduction of samples or ions at a relatively high flow rate by using a rough vacuum pump with a low pumping speed, thereby making it possible to achieve both miniaturization and high sensitivity.

[0038] The working pressure P2 of the second vacuum chamber 2 is in the range of 0.5 mbar≤P2≤30 mbar. First, the working pressure greater than or equal to 0.5 mbar can be achieved by a rough vacuum pump, so there is no need to equip the second vacuum chamber with a turbomolecular pump separately, which facilitates the miniaturization of the second vacuum pump 5 and reduces the cost of the device. Secondly, the air pressure range less than or equal to 30 mbar can provide air pressure conditions for the arrangement and stable operation of some ion focusing devices, such as radio frequency focusing devices, in the second vacuum chamber 2, so that even if there is a high air pressure difference between the second vacuum chamber 2 and the first vacuum chamber 1, the ion beam can still maintain focus and be transmitted to the third vacuum chamber 3, and is not easy to expand and lose due to the existence of the air pressure difference. The ions are controlled by the ion focusing device to be transported to the lower vacuum chamber, reducing the influence of airflow interference on the transport process, so that the injection of the lower vacuum chamber is not restricted or less restricted by the flux size of the airflow inflow, which facilitates the miniaturization of the vacuum pump of the lower vacuum chamber.

[0039] In the above manner, the range of the working pressure P1 of the first vacuum chamber 1 is set so that the pumping speed of the first vacuum pump 4 and the aperture range of the atmospheric pressure interface 11 can obtain a suitable matching relationship. On the one hand, the first vacuum pump 4 is allowed to select a rough vacuum pump with a lower pumping speed and a smaller volume to reduce the volume of the first vacuum pump 4. On the other hand, it can allow the use of an atmospheric pressure interface 11 with a larger flow rate to improve the sensitivity of the mass spectrometer. At the same time, the working pressure of the second vacuum chamber 2 can also be achieved by using a rough vacuum pump, thereby reducing the use of a turbomolecular pump, simplifying the design of the pump system as a whole, and facilitating the miniaturization of the mass spectrometer.

[0040] In some embodiments, the working pressure of the first vacuum chamber 1 is further preferably 50mbar≤P1≤70mbar, and the working pressure of the second vacuum chamber 2 is further preferably 3.0mbar≤P2≤6.0mbar. By further configuring the first vacuum chamber 1 and the second vacuum chamber 2 within the above-mentioned air pressure range, the system air intake and the air pressure condition requirements of each chamber can be effectively balanced, thereby obtaining a higher system sensitivity. It should be noted that Figure 1 Only the necessary structure of the mass spectrometer that can achieve the technical effects of this preferred embodiment is shown, and other structures are not limited.

[0041] Implementation Method 2

[0042] like Figure 2 As shown, this embodiment provides a mass spectrometer. Unless otherwise specified, the various structures and figure marks are the same as those of the first embodiment and will not be repeated here.

[0043] The atmospheric pressure interface 11 of the mass spectrometer can be an injection interface or a capillary, and the injection interface can be a cylindrical hole or a conical hole. Figure 2In the description, the atmospheric pressure interface 11 is taken as a capillary as an example.

[0044] The vacuum interface 21 and the vacuum interface 31 may be a conical hole, a cylindrical hole or a combination thereof.

[0045] Among them, the range of the working pressure P1 of the first vacuum chamber 1 is selected as P1>30mbar, and the range of the pumping speed S1 of the first vacuum pump 4 is S1≤2L / min. Because the working gas pressure of the first vacuum chamber 1 is relatively high, even if the gas flow rate is relatively large, a rough vacuum pump with a low pumping speed can be used to meet the vacuum degree requirements. Since the pumping speed S1 of the first vacuum pump 4 is relatively low, a rough vacuum pump with a relatively small volume can be selected to achieve the pumping of the first vacuum chamber 1, thereby realizing the miniaturization of the pump system of the mass spectrometer. For example, a miniature floating vortex vacuum pump with a weight of less than 0.3kg and a power of less than 10W can be selected. It has a relatively small volume and weight, and consumes less power, and accordingly, the noise generated is also relatively low.

[0046] Preferably, the mass spectrometer may also be provided with a chromatographic separation device (not shown) upstream of the ion source, wherein the chromatographic separation device is a liquid chromatography or a gas chromatography separation device. Specifically, the separation device may include: a capillary electrophoresis (CE) separation device; a capillary electron chromatography (CEC) separation device; a ceramic-based multilayer microfluidic substrate separation device; or a supercritical fluid chromatography separation device.

[0047] In this embodiment, the mass spectrometer further includes an ion source 8. Taking the API ion source as an example, the diameter range of the atmospheric pressure interface 11 is 0.1 mm ≤ d ≤ 0.4 mm, and the range of the gas flow rate Q of the atmospheric pressure interface is Q> 150 mL / min. Compared with the gas flow range of the prior art that allows gas to enter the vacuum chamber from the API ion source, under the same other conditions, the mass spectrometer provided in this embodiment has a higher sensitivity because the gas flow rate of the atmospheric pressure interface 11 is larger.

[0048] Preferably, the ion source 8 may also include one or more of electrospray ionization (ESI), microspray ionization, nanospray ionization, chemical ionization (CI), matrix-assisted laser desorption ionization (MALDI), atmospheric pressure photoionization (APPI), and glow discharge ionization.

[0049] In this embodiment, the working pressure P2 of the second vacuum chamber 2 is designed to be in the range of 0.5 mbar≤P2≤30 mbar, and the pumping speed S2 of the second vacuum pump 5 is set in the range of S2≤20 L / min.

[0050] Compared with the prior art, for example, the mass spectrometer provided by patent GB2520785 and the present embodiment are similarly provided with at least three-stage vacuum chambers, and the pressure range of the second vacuum chamber is 0.001-0.1mbar, and a turbomolecular pump with a pumping speed S≤4200L / min is selected for pumping. Since the working pressure P2 range of the second vacuum chamber 2 in the present embodiment can be achieved with the help of a rough vacuum pump, the pumping speed S2 of the second vacuum pump 5 is in the range of S2≤20L / min. Specifically, the second vacuum pump 5 can be a miniature floating vortex vacuum pump weighing about 2kg and with a power of less than 80W. Compared with the turbomolecular pump, the pump system configuration is simpler and the cost is lower.

[0051] In this embodiment, the range of the working pressure P3 of the third vacuum chamber 1 is not significantly different from that in the prior art, and the pressure range is usually set to P3≤0.001 mbar, and the third vacuum pump 6 is a turbomolecular pump.

[0052] Since the turbomolecular pump (high vacuum pump) cannot be discharged directly to atmospheric pressure, it is necessary to provide pre-pumping pressure for it through a pre-pumping pump. Preferably, in this embodiment, the first vacuum pump 4 or the second vacuum pump 5 is selected as the pre-pumping pump of the third vacuum pump 6. In this way, the pre-pumping pressure is provided for the third vacuum pump 6 through the existing vacuum pump, and there is no need to set up a pre-pumping pump for the third vacuum pump 6. The existing pump system is effectively utilized, and the overall volume of the pump system is miniaturized. In addition, although Figure 2 Only the example of the second vacuum pump 5 being used as a pre-pump for the third vacuum pump 6 is given, but since the first vacuum pump 4 and the second vacuum pump 5 are both rough vacuum pumps in this embodiment, it is easy for those skilled in the art to think that both the first vacuum pump 4 and the second vacuum pump 5 can provide pre-pumping pressure for the third vacuum pump 6. Preferably, the second vacuum pump 5 is connected to the third vacuum pump 6. With such an arrangement, since the second vacuum pump 5 has a higher pumping speed, the pre-pumping pressure provided is also greater, making it easier for the third vacuum chamber 3 to reach the working pressure.

[0053] It should be noted that, in addition to the floating scroll vacuum pump, the first vacuum pump 4 and the second vacuum pump 5 may also be other vacuum pumps capable of achieving the working pressure required by the vacuum chamber, such as diaphragm pumps.

[0054] In this embodiment, through the working pressure design of the first vacuum chamber 1, a balance is achieved between the selection of the vacuum pump and the aperture of the atmospheric pressure interface, so that the working pressure can be achieved by a miniature vacuum pump, and the aperture of the atmospheric pressure interface 11 is relatively large. Compared with traditional commercial mass spectrometers, such as Shimadzu LCMS-2020, the reduction in system intake air flow is less than one order of magnitude, thereby ensuring the sensitivity of the instrument.

[0055] Through the working pressure design of the second vacuum chamber 2 and the selection of the second vacuum pump 5, the miniaturization of the second vacuum pump 5 is achieved compared with the prior art.

[0056] By using the first vacuum pump 4 or the second vacuum pump 5 as a pre-pump for the third vacuum pump 6, reasonable and full utilization of the pump system is achieved.

[0057] In summary, the mass spectrometer provided in this embodiment realizes the miniaturization design of the mass spectrometer while ensuring the sensitivity of the mass spectrometer through a multi-stage vacuum chamber design combined with the working pressure design of each stage of the vacuum chamber and the selection and matching of the vacuum pump.

[0058] Preferably, an ion focusing unit 12 is provided in the first vacuum chamber 1 to limit the running trajectory of the ions so that the ions can smoothly enter the next vacuum chamber. Specifically, the ion focusing unit 12 is an electrostatic focusing unit or an aerodynamic focusing unit. Since the vacuum degree of the first vacuum chamber 1 is relatively low, and the radio frequency ion guide device cannot work under vacuum conditions with a working pressure range of P>30mbar, the first vacuum chamber 1 uses an electrostatic focusing unit or an aerodynamic focusing unit to limit the running trajectory of the ions.

[0059] Because an electrostatic focusing unit or an aerodynamic focusing unit is provided in the first vacuum chamber 1, the ions are focused during the transmission process in the first vacuum chamber 1. Therefore, even if the airflow expands due to the change in air pressure, the ion beam can still be focused and transmitted in the axial direction. Therefore, a vacuum interface with a smaller aperture can be selected to reduce the gas flow entering the second vacuum chamber, and the loss of ions caused by the reduction in aperture can be compensated to a certain extent by focusing. Therefore, under the premise that the flux of the required gas inflow is reduced, even if the air pressure of P2 is smaller than that of P1, a rough vacuum pump with a lower pumping speed can still be used to meet the vacuum degree and flux requirements of the second vacuum chamber 2, thereby facilitating the miniaturization of the pump system and the mass spectrometer. In addition, by using a rough vacuum pump to evacuate, the air pressure range of the first vacuum chamber can provide a suitable air pressure environment for the electrostatic focusing unit or the aerodynamic focusing unit, ensuring that the electrostatic focusing unit or the aerodynamic focusing unit can operate stably.

[0060] Preferably, a radio frequency ion guide device 22 is provided in the second vacuum chamber 2 to guide ions to the next vacuum chamber. The gas pressure condition in the second vacuum chamber 2 can ensure the normal operation of the radio frequency ion guide device 22, and the radio frequency ion guide device 22 can constrain ions along the ion transmission path to reduce the loss of ions during the transmission process.

[0061] Preferably, the mass spectrometer may also be provided with a chromatographic separation device upstream of the ion source, wherein the chromatographic separation device is a liquid chromatography or gas chromatography separation device. Specifically, the separation device may include: a capillary electrophoresis (CE) separation device; a capillary electron chromatography (CEC) separation device; a ceramic-based multilayer microfluidic substrate separation device; or a supercritical fluid chromatography separation device.

[0062] Preferably, the atmospheric pressure interface 11 is a capillary, a cylindrical hole or a tapered hole.

[0063] The capillary, cylindrical hole or conical hole serving as the atmospheric pressure interface 11 can continuously introduce sample gas carrying ions from the external atmospheric pressure environment and limit the gas flow rate within a reasonable range by utilizing the aperture size.

[0064] Preferably, the vacuum interface is a cylindrical hole, a conical hole or a combination thereof. Further preferably, the diameter range of the vacuum interface 21 is, and the diameter range of the vacuum interface 31 is 0.2 mm≤d≤0.6 mm.

[0065] Using cylindrical holes and conical holes as vacuum interfaces can, on the one hand, maintain the relative independence of the vacuum environment of each chamber and limit the gas flow entering the next vacuum chamber; on the other hand, the holes can allow ions to pass through and maintain stable delivery of ion beams.

[0066] Preferably, a mass analyzer 32 is provided in the third vacuum chamber 3 for screening ion samples according to the mass-to-charge ratio. Specifically, the mass analyzer 32 is a quadrupole mass analyzer or an ion trap mass analyzer.

[0067] The turbomolecular pump is compact and usually air-cooled, can be installed in any direction, and can achieve a high vacuum degree. Small or medium turbomolecular pumps can allow a higher pre-pumping pressure, and a rough vacuum pump can be used as a pre-pump for the turbomolecular pump. As a combination, it provides a stable high vacuum environment for the third vacuum chamber 3 where the mass analyzer is located.

[0068] The quadrupole mass analyzer or ion trap mass analyzer is small in size and can work normally in a relatively low vacuum environment.

[0069] Preferably, the mass spectrometer further comprises an ion detector 7 corresponding to the ion outlet of the mass analyzer 32 .

[0070] Preferably, the length range of the ion focusing unit 12 is L≤10 mm;

[0071] Preferably, the length range of the radio frequency ion guide device 22 is L≤50 mm;

[0072] As a preferred embodiment, taking the mass analyzer 32 as a quadrupole mass analyzer, the internal volume of the first vacuum chamber 1 is V≤100cm 3 ;

[0073] The internal volume of the second vacuum chamber 2 is V≤200cm 3 ;

[0074] The internal volume of the third vacuum chamber 3 is V≤700cm 3 .

[0075] The total internal volume of the first, second and third vacuum chambers is preferably V≤1000cm 3 According to a particularly preferred embodiment, the combined internal volume of the first, second and third vacuum chambers is approximately 770 cm 3 Compared to the usual 4000cm 2 The total internal volume of the vacuum chamber of a full-size quadrupole mass spectrometer with a total internal volume of is smaller than that of a full-size quadrupole mass spectrometer, and the total internal volume of the vacuum chamber of the mass spectrometer provided by this embodiment is smaller, thereby further realizing the miniaturization of the mass spectrometer.

[0076] It should be noted that although an example of setting up a three-stage vacuum chamber is given in this embodiment, this is not a limitation of the present invention. Based on this embodiment, those skilled in the art can conceive of setting up more levels of vacuum chambers, such as a four-stage vacuum chamber, and adjusting the working pressure range of each vacuum chamber accordingly to achieve the miniaturization of the mass spectrometer.

[0077] [Further explanation on technical effects]

[0078] As described in the background technology, Figure 3 It is a vacuum system used by a large mass spectrometer in the prior art. The vacuum system of the mass spectrometer adopts a two-stage structure, wherein an ion focusing device is arranged in the front-stage vacuum chamber, and a mass analyzer is arranged in the rear-stage vacuum chamber.

[0079] Some RF ion focusing devices can work stably at a pressure of a few mbar. Once the pressure rises to 10 mbar or even higher, the ion transmission rate of these ion focusing devices will be significantly reduced and they will not be able to work stably. In addition, the pressure increase in the front vacuum chamber will also cause the pressure in the back vacuum chamber to increase, affecting the normal operation of the mass analyzer.

[0080] Therefore, the vacuum condition setting of the multi-stage vacuum system and the selection of the corresponding vacuum equipment need to comprehensively consider the types of equipment placed in the vacuum chambers at each level, which is a systematic project.

[0081] Using a large-volume, high-speed vacuum pump to simultaneously ensure the system's air intake and vacuum requirements is feasible for large mass spectrometers that require a smaller pump volume. For example, an oil pump with a very high pumping speed (above 400L / min) can be used as the vacuum device of the fore-stage vacuum chamber, and a vacuum interface with a large diameter (for example, up to 0.5mm) can be used for air intake to ensure the size of the system's air intake. Some large mass spectrometers using this structural vacuum system can achieve an air intake of 1L / min when the air pressure in the fore-stage vacuum chamber is 2mbar.

[0082] However, if the system is to be miniaturized, the pump must be miniaturized first. Undoubtedly, the vacuum device of the fore vacuum chamber can no longer use a large oil pump. Figure 4 This is a schematic diagram of the vacuum system structure of a small mass spectrometer in the prior art. Figure 4 , even if a small vacuum pump with a better combination of pumping speed, ultimate vacuum and noise is used, and the pressure of the fore vacuum chamber is raised to 5mbar, according to the following calculation:

[0083] Gas flow rate Q2 in the back stage vacuum chamber = gas flow rate Q of the turbomolecular pump TMP =0.001mbar×4800L / min≈5mbar·L / min

[0084] Vortex pump gas flow Q SP =5mbar×10L / min=50mbar·L / min

[0085] Q0=Q2+Q SP =55mbar·L / min

[0086] System air intake Qv = Q0 / atm = 0.055L / min

[0087] It can be seen that the system gas intake is still only 55mL / min. This level of system gas intake will limit the sensitivity of the system. If the gas pressure of the fore-stage vacuum chamber is further increased, the types of devices that can be used in the fore-stage vacuum chamber will be reduced. For example, some radio frequency ion focusing devices will not be able to work normally under higher gas pressure.

[0088] Through the technical solution provided by the present invention, Figure 5 Taking the scheme shown as an example, by adding one or more vacuum chambers in front of the second vacuum chamber 2 where the ion focusing device (RF ion guide device 22) is located, the second vacuum chamber 22 where the ion focusing device (RF ion guide device 22) is located is not directly connected to the external environment. Figure 5The vacuum system in the embodiment of the present invention can increase the air intake of the system to a great extent (for example, by more than twice) while slightly increasing the volume of the pump (for example, only a small rough pump is added, and the volume increase of the pump system by the turbo pump 1 is almost negligible).

[0089] In addition, if an ion focusing device is also provided in the first vacuum chamber 1, the loss in the air flow transmission process will not or will be less reflected as the loss of ions, so that the increase in the system air intake volume can proportionally or significantly increase the amount of ions entering the mass analyzer 32, thereby effectively taking into account the miniaturization and sensitivity requirements of the mass spectrometer system.

[0090] The following is an introduction to the technical effects that can be achieved by the vacuum system of the mass spectrometer in some embodiments of the present invention, in combination with specific calculation results, such as the technical effect of significantly increasing the air intake volume of the mass spectrometer system in exchange for a slight increase in the volume of the pump system.

[0091] Further references Figure 5 The first vacuum chamber 1 is connected to the external atmospheric environment, and a capillary with a tube diameter of 0.25 mm is used as the atmospheric pressure interface 11 for sample injection. The working pressure of the first vacuum chamber 1 is 55 mbar; the second vacuum chamber 2 is connected to the first vacuum chamber 1 using a cylindrical hole or a conical hole as a vacuum interface 21, and the working pressure of the second vacuum chamber 2 is 5 mbar. A radio frequency ion guide device 22 is arranged inside the second vacuum chamber 2 for focusing the ions carried in the airflow and keeping them moving in the axial direction; a linear ion trap mass analyzer 32 is arranged inside the third vacuum chamber 3 for performing mass analysis.

[0092] The first vacuum chamber 1 and the second vacuum chamber 2 are both equipped with a rough pump, such as a vortex pump, wherein the vortex pump SP1 connected to the first vacuum chamber 1 can meet the vacuum requirement of the first vacuum chamber 1 when operating at a pumping speed of 2L / min, so the maximum pumping speed required to be provided by the vortex pump is relatively small, and the volume of the pump does not need to be large. The vortex pump SP2 connected to the second vacuum chamber 2 can meet the vacuum requirement of the second vacuum chamber 2 when operating at a pumping speed of 10L / min, and the volume of the vortex pump SP2 that can achieve this pumping speed will not be too large. Overall, the pump system is less complex and smaller in size.

[0093] According to the above parameter settings, the system air intake data of the mass spectrometer can be calculated.

[0094] Q2=Q TMP =0.001mbar×4800L / min≈5mbar·L / min

[0095] Q SP2 =5mbar×10L / min=50mbar·L / min

[0096] Q1=Q2+Q SP2 =55mbar·L / min

[0097] Q SP1 =55mbar×2L / min=110mbar·L / min

[0098] Q0=Q1+Q SP1 =165mbar·L / min

[0099] System air intake Qv = Q0 / atm = 0.165L / min

[0100] According to the above calculations, the mass spectrometer can achieve a system gas intake of 165 mL / min through the above design, which is three times the system gas intake (55 mL / min) of a two-stage vacuum system using basically the same pump model. In addition, the diameter of the capillary used for injection is also larger, which not only reduces the loss of internal ion transmission, but also reduces the probability of clogging.

[0101] In some embodiments, an ion focusing device 11 may be further provided in the first vacuum chamber 1. For example, an electrostatic focusing unit or an aerodynamic unit may be provided. These ion focusing devices 11 or aerodynamic units may keep ions at the center of the airflow, so that even if the gas expands or deflects during the flow of gas along the axial direction, the ions may still be stably transmitted to the second vacuum chamber 2 and the third vacuum chamber 3, and mass analysis may be performed by the mass analyzer 32.

[0102] Even if the gas flow rate entering the second vacuum chamber 2 drops to a specified proportion of the system gas intake or even below, due to the focusing effect of the ion focusing device 22, the ion passing rate can still be greater than Figure 4 The passing rate of ions in the system is increased, thereby effectively improving the sensitivity of the system. Through the above methods, the sensitivity and miniaturization of the system can be effectively taken into account.

[0103] Those skilled in the art will appreciate that, in the above-mentioned embodiments, many technical details are provided in order to enable readers to better understand the present application. However, even without these technical details and various changes and modifications based on the above-mentioned embodiments, the technical solutions claimed for protection in the claims of the present application can be basically realized. Therefore, in practical applications, various changes can be made to the above-mentioned embodiments in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A mass spectrometer, characterized in that include: The first vacuum chamber has an atmospheric pressure interface connected to an external atmospheric pressure environment and is connected to a first vacuum pump, wherein the working pressure P1 of the first vacuum chamber is in the range of P1>30 mbar; A second vacuum chamber is connected to the first vacuum chamber via a vacuum interface to receive the analyte from the first vacuum chamber, the second vacuum chamber is connected to a second vacuum pump, and the working pressure P2 of the second vacuum chamber is in the range of 0.5 mbar≤P2≤30 mbar; as well as a third vacuum chamber connected to the second vacuum chamber via a vacuum interface to receive the analyte from the second vacuum chamber, the third vacuum chamber being connected to a third vacuum pump, the first vacuum pump or the second vacuum pump being used as a pre-pump of the third vacuum pump, The first vacuum pump and the second vacuum pump are both rough vacuum pumps, and the third vacuum pump is a turbomolecular pump. The range of the pumping speed S1 of the first vacuum pump is: S1≤5L / min, and the range of the diameter of the atmospheric pressure interface is 0.1mm≤d≤0.4mm.

2. The mass spectrometer according to claim 1, characterized in that The range of the pumping speed S1 of the first vacuum pump is: S1≤2L / min.

3. The mass spectrometer according to claim 1, characterized in that The range of the pumping speed S2 of the second vacuum pump is: S2≤50L / min.

4. The mass spectrometer according to claim 3, characterized in that The range of the pumping speed S2 of the second vacuum pump is: S2≤20L / min.

5. The mass spectrometer according to claim 1, characterized in that An electrostatic focusing unit or an aerodynamic focusing unit is disposed in the first vacuum chamber, for focusing ions in the airflow entering the first vacuum chamber from the atmospheric pressure interface onto a path for transmission to the second vacuum chamber.

6. The mass spectrometer according to claim 1, characterized in that The second vacuum chamber is provided with a radio frequency ion guiding device for guiding ions to pass through the second vacuum chamber and enter the third vacuum chamber.

7. The mass spectrometer according to claim 1, characterized in that The atmospheric pressure interface is a capillary, a cylindrical hole or a conical hole.

8. The mass spectrometer according to claim 1, characterized in that The vacuum interface is a cylindrical hole, a conical hole or a combination thereof.

9. The mass spectrometer according to claim 1, characterized in that A mass analyzer is arranged in the third vacuum chamber.

10. The mass spectrometer according to claim 9, characterized in that The mass analyzer is a quadrupole mass analyzer or an ion trap mass analyzer.

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