Ion trapping cavity system and method based on adaptive regulation of damping air pressure

Abstract

The present application relates to the technical field of mass spectrometer, and more particularly to an ion trapping cavity system and method based on adaptive regulation of damping gas pressure. The ion trapping cavity system comprises a first-stage vacuum cavity, a second-stage vacuum cavity, a third-stage vacuum cavity and a dynamic gas supplementing unit connected in sequence; the second-stage vacuum cavity is internally provided with a collision reaction cell, and the collision reaction cell is internally provided with a multipole rod or a linear ion trap; the dynamic gas supplementing unit is connected with the second-stage vacuum cavity, and the dynamic gas supplementing unit introduces buffer gas into the second-stage vacuum cavity, so that the working gas pressure in the cavity is maintained within a target damping gas pressure window of 5x10 ‑ ³ Torr-5x10 ‑ ² Torr. The present application solves the problems of unsatisfactory ion trapping efficiency and limited dynamic range in the existing mass spectrometer vacuum system due to the inability to adjust the working gas pressure in real time according to the actual ion trapping state, and improves the comprehensive performance of mass spectrometric analysis.

Description

Technical Field

[0001] This invention relates to the field of mass spectrometry technology, and in particular to an ion trapping chamber system and method based on adaptive control of damping gas pressure. Background Technology

[0002] A mass spectrometer is an analytical instrument that performs qualitative and quantitative analysis of substances by measuring the mass-to-charge ratio of ions. It is widely used in fields such as chemistry, biology, medicine, and environmental monitoring. A mass spectrometer typically consists of an ion source, a mass analyzer, an ion detector, and a vacuum system. The vacuum system provides sufficient mean free path for the ions to reduce signal loss or mass resolution degradation caused by collisions with background gas molecules during ion flight or motion. To accommodate the different vacuum requirements of various functional modules, tandem mass spectrometers often employ a multi-stage vacuum chamber structure. Differential gas extraction is achieved through connecting holes and independent pump sets between stages, resulting in a stepped pressure distribution in the ion source region, ion guiding region, and mass analysis region.

[0003] A prior art device for ion generation, transport, and mass spectrometry coupling in a low-vacuum system is disclosed. This device employs a four-stage vacuum differential structure, establishing pressure differences between different functional chambers to maintain each chamber at its required working pressure. The device includes a vacuum pump assembly and connecting holes between each chamber. The pressure gradient is achieved through the pumping action of the pump assembly and the flow conduction limitation of the connecting holes. Specifically, the chamber containing the ion trap or collision reaction cell introduces buffer gas through trace amounts of gas leaking from the upstream chamber or through pulsed gas injection, used for collision cooling of the incoming ions. In this scheme, the pressure of each chamber is set to a fixed value during instrument initialization or operation, and the vacuum system maintains a substantially constant chamber pressure according to preset parameters.

[0004] The buffer gas required in the collision reaction cell or ion trap not only cools the ion kinetic energy but also directly affects the ion trapping efficiency, spatial distribution volume, and the strength of the space charge effect. These ion trapping parameters depend not only on the chamber pressure but also on the type and mass range of ions entering the ion trap, the ion beam density, and the real-time injection volume. A fixed-pressure control method cannot sense the actual motion and distribution of ions within the trap, and therefore cannot actively adjust the pressure to maintain optimal ion trapping when ion type or injection conditions change. For example, in the analysis of high-concentration samples, increased ion cloud density leads to a stronger space charge effect. In this case, a constant buffer gas pressure is insufficient to effectively compress the ion cloud volume, causing mass shift in the mass spectrometry peak and a decrease in resolution, limiting the instrument's dynamic range. Furthermore, for ions with different mass-to-charge ratios, their collision cooling cross-sections differ, and a fixed pressure results in uneven cooling of ions of different masses, leading to a mass discrimination effect. Furthermore, if constant pressure control is achieved solely through feedback from a pressure sensor, the goal is essentially to maintain stable gas pressure within the chamber, without addressing the issue of how the actual cooling state of ions within the trap changes under analytical conditions. Consequently, it becomes difficult to obtain optimal analytical sensitivity and resolution under various sample matrices and analytical conditions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide an ion trapping chamber system based on adaptive damping pressure control. This system actively maintains an optimal damping pressure window in the collision reaction cell / ion trap region and adaptively adjusts the pressure in real time according to the actual ion trapping state, thereby achieving an optimal balance between ion collision cooling and ion transport efficiency in a limited volume chamber, significantly improving the sensitivity and dynamic range of trace / ultra-trace mass spectrometry analysis.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions: In a first aspect, embodiments of the present invention provide an ion trapping cavity system based on damped gas pressure adaptive control, comprising a first-stage vacuum cavity, a second-stage vacuum cavity, a third-stage vacuum cavity, and a dynamic gas replenishment unit connected in sequence; a collision reaction cell is disposed inside the second-stage vacuum cavity, and a multipole or linear ion trap is disposed inside the collision reaction cell; the dynamic gas replenishment unit is connected to the second-stage vacuum cavity, and the dynamic gas replenishment unit introduces buffer gas into the second-stage vacuum cavity to maintain the working gas pressure inside the cavity at 5×10 - ³ Torr-5×10 - Within the target damping pressure window of ² Torr.

[0007] Secondly, embodiments of the present invention also provide a mass spectrometry analysis method for the ion trapping cavity system based on adaptive damping pressure control, comprising the following steps: The vacuum pump unit is started to evacuate each stage of the vacuum chamber, so that the first stage vacuum chamber reaches 1×10⁻⁶. -4 Torr-5×10 -4 The operating pressure of Torr is 1×10⁻⁶ in the third-stage vacuum chamber. -6 Torr-5×10 -5 Torr's operating air pressure; Buffer gas is introduced into the second-stage vacuum chamber through a dynamic gas replenishment unit, so that the working pressure of the second-stage vacuum chamber reaches the target damping pressure window, which is 5×10⁻⁶. - ³ Torr-5×10 - ² Torr; Ion trapping status signals are acquired in real time through the ion trapping status monitoring unit; The adaptive control unit determines whether the current working gas pressure is at the optimal damping point based on the ion trapping status signal. If the current working gas pressure deviates from the optimal damping point, the adaptive control unit adjusts the gas replenishment parameters of the dynamic gas replenishment unit to bring the working gas pressure of the second-stage vacuum chamber back to the optimal damping point. Ion collision cooling, ion trapping, and mass spectrometry analysis were performed at the optimal damping point.

[0008] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages: The ion trapping chamber system actively maintains the working gas pressure of the collision reaction cell or linear ion trap at 5 × 10⁻⁶ by setting a dynamic gas replenishment unit in the second-stage vacuum chamber. - ³ Torr-5×10 - Within the target damping pressure window of the Torr, a moderate pressure environment conducive to collisional cooling is established in the ion trapping region. This pressure range is approximately two orders of magnitude higher than traditional high vacuum conditions, significantly increasing the collision frequency between ions and buffer gas molecules. Ions can be rapidly cooled and effectively focused in the central region of the trap, solving the problems of low ion trapping efficiency and divergent ion cloud distribution caused by insufficient buffer gas supply in traditional technologies. Simultaneously, the upper limit of this pressure window is also reasonably set to avoid excessive collisions and ion scattering losses caused by excessively high pressure. By actively replenishing gas rather than relying on leaked gas, the system can independently control the pressure of the second-stage vacuum chamber without being affected by pressure fluctuations in the upstream chamber. Therefore, this invention solves the problem of unsatisfactory ion trapping efficiency and limited dynamic range in existing mass spectrometer vacuum systems due to the inability to adjust the working pressure in real time according to the actual ion trapping state, thus improving the overall performance of mass spectrometry analysis.

[0009] Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In addition, the dimensions or spacing between the components are exaggerated to show the position of each component, and the schematic diagrams are for illustrative purposes only.

[0011] Figure 1 This is a schematic diagram of the overall structure of the ion trapping cavity system based on damping pressure adaptive control of the present invention; Figure 2 This is a block diagram illustrating the damping pressure adaptive control principle of the second-stage vacuum cavity in this invention. Figure 3 This is a schematic diagram illustrating the working principle of the ion trapping state monitoring unit of the present invention; Figure 4 This is a schematic diagram of the electrically controlled aperture adjustment mechanism at the connecting hole of the present invention; Figure 5 A comparison diagram of the radial spatial distribution of ion clouds under different damping pressures; Figure 6 The graph shows the relationship between damping pressure and ion trapping efficiency. Figure 7 This is a comparison chart of the ion trapping efficiency of the method of the present invention and the existing constant voltage control method; Figure 8 This is a schematic diagram of the gas pressure distribution in the three-stage vacuum cavity of the present invention.

[0012] In the diagram: 100, Ion trapping chamber system; 101, First-stage vacuum chamber; 102, Second-stage vacuum chamber; 103, Third-stage vacuum chamber; 104, ESI source; 105, Spray needle; 106, Three-dimensional adjustable exhaust gas channel; 109, Primary vacuum pump; 110, First connecting hole; 111, Collision reaction cell; 112, Linear ion trap; 113, Secondary vacuum pump; 114, Dynamic gas replenishment unit; 115, Buffer gas cylinder; 116, Mass flow controller; 117, Pulse solenoid valve; 118, Gas pressure sensing unit; 119, Second connecting hole; 120, Quadrupole mass analyzer; 121, Ion detector; 122, Third-stage vacuum pump; 123, Ion trapping status monitoring unit; 124, Adaptive control unit; 125, Ion cloud imaging module; 126, Ion signal analysis module. Detailed Implementation

[0013] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the linguistic context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0014] Generally speaking, the terms "comprising" and "including" only indicate that the steps and elements are explicitly identified, and these steps and elements do not constitute an exclusive list. The method or apparatus may also include other steps or elements.

[0015] Existing technologies propose a differential pressure dual ion trap scheme, which uses a high-pressure trap (operating gas pressure approximately 5 × 10⁻⁶) to... - ³~1×10 - ²Torr) and low-pressure trap (working pressure approximately 1×10 -4 ~3×10 -4 The ion traps (Tor) are placed adjacent to each other, with collision cooling and fragmentation functions performed in the high-pressure trap and high-resolution analysis scanning performed in the low-pressure trap. However, this technical solution still has the following shortcomings: (1) It requires two physically separate ion traps, which increases the complexity and volume of the system; (2) The pressure difference between the high-pressure trap and the low-pressure trap needs to be maintained by a precision pump, which increases the design difficulty of the vacuum system; (3) There are additional losses in ion transport between the two ion traps; (4) It is impossible to realize the function of real-time adaptive adjustment of gas pressure according to the actual ion trapping state.

[0016] Chinese invention patent CN 111477533 B discloses a device for ion generation, transport, and mass spectrometry coupling in a low-vacuum system. This device employs a four-stage vacuum differential structure, allowing for vacuum control based on the requirements of each component. However, this technical solution primarily focuses on establishing pressure differences between different functional chambers and does not address the technical concept of adaptively adjusting the working pressure of the collision cell / ion trap based on the ion trapping state. Furthermore, it does not disclose specific technical means for actively maintaining a specific damping pressure window in the ion trap region to achieve optimal collision cooling.

[0017] Chinese invention patent CN 105895476 B discloses a gas pressure control system for an ion trap mass spectrometer. This system monitors the gas pressure inside the ion trap in real time using a gas pressure sensor and adjusts the opening of the inlet valve according to a set value to maintain a constant gas pressure. US patent US 9870876 B2 discloses an ion trap with variable buffer gas pressure, which maintains a constant pressure of the buffer gas inside the ion trap using a pressure sensor and a flow controller. However, both of these patents rely solely on feedback from gas pressure sensors for constant pressure control and cannot dynamically adjust the gas pressure according to the actual trapping state of the ions, thus failing to address the differentiated cooling requirements of ions with different masses, concentrations, and kinetic energies.

[0018] Furthermore, while existing technologies employ PID closed-loop control to regulate vacuum chamber pressure, these methods primarily aim to maintain a constant target pressure. The control parameter is typically the deviation between the measured and set pressure values. This control approach fails to reflect the actual trapping state of ions within the ion trap. Even under the same pressure conditions, ion clouds with different masses, kinetic energies, and densities can exhibit significant differences in collision cooling effects and trapping efficiency. Therefore, existing constant-pressure control methods cannot achieve true on-demand damping and struggle to achieve optimal ion trapping effects under various analytical conditions.

[0019] Therefore, existing mass spectrometer vacuum chamber systems present the following technical contradictions: on the one hand, the mass analyzer and detector require high vacuum to ensure ion transport efficiency; on the other hand, the collision reaction cell / ion trap requires an appropriate amount of buffer gas to achieve sufficient collision cooling. How to reconcile this contradiction within a limited-volume chamber system and achieve precise, adaptive control of the damping pressure in the collision cell region is a pressing technical problem to be solved in this field.

[0020] The technical concept of this invention is based on the following discovery: In ion trap operation, there exists an optimal damping pressure window within which the collision frequency between ions and buffer gas molecules is sufficient for collision cooling without causing ion scattering loss due to excessive collisions. For a typical linear ion trap (RF frequency 0.5~3 MHz, trap radius r0 = 2~5 mm), this optimal damping pressure window corresponds to 5 × 10⁻⁶ mm. - ³ Torr to 5×10 - The range of Torr is much lower than the operating pressure of traditional high-vacuum ion traps (10). -5 ~10 -4 (Torr), but significantly higher than atmospheric pressure. Within this pressure window, the collision cooling time constant of ions can reach the sub-millisecond level, much faster than the millisecond to tens of millisecond levels under high vacuum conditions, thus greatly improving ion trapping efficiency and mass spectrometry analysis speed.

[0021] More importantly, this invention discovers that the optimal damping point within the optimal damping pressure window is not a fixed value, but rather dynamically changes with parameters such as ion mass, kinetic energy, and density. For example, high-mass ions (m / z > 1000) require higher damping pressure to achieve sufficient collision cooling; high-density ion clouds require appropriate pressure adjustment to reduce the space charge effect; and high-kinetic-energy ions, such as those entering directly from the ion source, require instantaneous pressure increase for rapid cooling. Therefore, this invention proposes an adaptive damping control technology that dynamically adjusts the damping pressure by real-time monitoring of the ion trapping state signal, achieving on-demand damping rather than simple constant pressure control.

[0022] The ion trapping chamber system comprises a first-stage vacuum chamber, a second-stage vacuum chamber, and a third-stage vacuum chamber connected in sequence. In practical applications, the first-stage vacuum chamber receives ions from an atmospheric pressure ion source and introduces them into the vacuum system. The second-stage vacuum chamber serves as the core region for ion collision cooling and trapping. The third-stage vacuum chamber is used for mass analysis and ion detection. Gas flow and differential pumping are achieved between the various vacuum chambers via connecting holes, allowing ions to be sequentially transported along the chambers. The second-stage vacuum chamber contains a collision reaction cell, which houses a multipole or linear ion trap. The multipole can be a quadrupole, hexapole, or octapole, used to confine ions near the central axis of the collision reaction cell. The linear ion trap achieves three-dimensional ion confinement through a radial radio frequency electric field.

[0023] The system is equipped with a dynamic gas supply unit connected to the second-stage vacuum chamber. This dynamic gas supply unit actively introduces buffer gas into the second-stage vacuum chamber to maintain the working gas pressure within the chamber at 5 × 10⁻⁶. - ³ Torr-5×10 - The target damping pressure window for the ² Torr is within this range. This pressure range is significantly higher than the high vacuum environment of the collision cell or ion trap in a conventional mass spectrometer. Its purpose is to provide a sufficiently dense buffer gas molecule environment, allowing ions entering the second-stage vacuum chamber to undergo multiple collisions with the buffer gas molecules during their flight. This rapidly dissipates the high initial kinetic energy of the ions into thermal energy, thereby focusing the ions in the central region of the trap or cell. However, this pressure range is not necessarily better the higher it is; 5 × 10⁻⁶ is acceptable. - ³ Torr-5×10 - The window range of ²Torr is an experimentally verified suitable range that can achieve effective collision cooling without causing excessive scattering loss.

[0024] The ion trapping chamber system also includes vacuum pump units connected to each vacuum chamber, and pressure sensing units connected to each vacuum chamber. In a specific embodiment, the first-stage vacuum chamber is connected to the primary vacuum pump, the second-stage vacuum chamber to the secondary vacuum pump, and the third-stage vacuum chamber to the tertiary vacuum pump. Each vacuum pump operates independently, and the difference in pumping speed, combined with the flow conduction limitation of the connecting orifice, allows each chamber to maintain a different working pressure. The pressure sensing unit can be a capacitive thin-film vacuum gauge, which measures the real-time pressure value of each chamber and feeds the signal back to the control system. The inclusion of this pressure sensing unit enables the system to obtain the real-time pressure status of each chamber, providing a data basis for subsequent pressure regulation.

[0025] Furthermore, an ion trapping state monitoring unit and an adaptive control unit were added. The adaptive control unit is connected to both the ion trapping state monitoring unit and the dynamic gas replenishment unit. The ion trapping state monitoring unit monitors the actual motion and spatial distribution of ions within the second-stage vacuum chamber, not just the chamber's pressure. The adaptive control unit receives the ion trapping state signal from the monitoring unit and adjusts the gas replenishment parameters of the dynamic gas replenishment unit accordingly, maintaining the working pressure of the second-stage vacuum chamber at the optimal damping point within the target damping pressure window. This optimal damping point is not a fixed pressure value, but a dynamically optimal value that varies depending on the type, mass, and density of the ions entering the chamber. The control system no longer aims to maintain a constant pressure, but rather to optimize the ion trapping state. In other words, when the optimal damping point shifts towards the high-pressure or low-pressure side of the window under certain analytical conditions, the adaptive control unit can actively adjust the pressure to near that optimal value. This feedback adjustment method based on the actual ion trapping state solves the problem that fixed pressure control cannot adapt to changes in analytical conditions.

[0026] The parameters monitored by the ion trapping state monitoring unit include at least one of the following: the full width at half maximum (FWHM) of the ion cloud radial spatial distribution, the ion oscillation damping decay time constant, the ion cloud density space charge effect index, and the ion trapping potential well depth. The FWHM reflects the degree of ion cloud aggregation in the radial direction within the trap; a smaller value indicates more thorough collisional cooling and tighter ion compression. The ion oscillation damping decay time constant reflects the rate of kinetic energy dissipation after ion oscillation; a smaller constant indicates a faster collisional cooling rate. The ion cloud density space charge effect index can be expressed as mass spectrum peak mass shift, peak broadening, or ion signal saturation; these indices reflect the degree of interference caused by the Coulomb repulsion between ions on mass analysis when the ion cloud density is too high. The ion trapping potential well depth reflects the degree of ion confinement within the trap. These parameters describe the actual trapping quality of ions within the trap from different perspectives. The adaptive control unit adjusts the gas supply rate of the dynamic gas supply unit based on the deviation between the ion trapping state signal and the preset target value using a PID control algorithm or a fuzzy control algorithm. The preset target value can be the target value of the half-width at half-maximum (WHM) of the radial spatial distribution of the ion cloud, or it can be the target value of the ion oscillation damping decay time constant or the comprehensive error index. When the measured value deviates from the target value, the control unit calculates the required adjustment amount and outputs it to the dynamic gas replenishment unit. The PID algorithm is suitable for adjustment processes with good linearity, while the fuzzy control algorithm is suitable for complex adjustment processes where it is difficult to establish an accurate mathematical model. By using the ion trapping state parameters as controlled variables, direct optimization of the ion trapping quality is achieved.

[0027] For example, when the half-width at half-maximum (WHM) of the radial spatial distribution of the ion cloud is detected to be greater than the target value, it indicates that the collision cooling is insufficient and the ion cloud is too dispersed. At this time, the adaptive control unit increases the supplementary flow rate to increase the damping pressure and enhance the collision cooling effect. Conversely, when the damping time constant of the ion oscillation is detected to be too short, it indicates that the pressure is too high and causes excessive damping. At this time, the supplementary flow rate is reduced to lower the pressure.

[0028] The working pressure of the first-stage vacuum chamber is 1×10⁻⁶. -4 Torr-5×10 -4 Torr, this pressure range adapts to the transition requirements between atmospheric pressure ion sources and high vacuum mass analyzers, ensuring effective ion transport from atmospheric pressure without placing an excessive pumping burden on the subsequent vacuum stage. The operating pressure of the third-stage vacuum chamber is 1×10⁻⁶. -6 Torr-5×10 - 5 Torr, this high vacuum environment ensures a sufficiently large mean free path for ions in the mass analyzer, preventing damage to mass resolution from collisions between ions and residual gas molecules. The optimal damping point of the second-stage vacuum chamber is at 1×10⁻⁶. - ² Torr-2×10 -Within the range of 2 Torr. In specific experimental verification, when the damping air pressure is 5 × 10⁻⁶... - ³ Torr-5×10 - ² The ion trapping efficiency is above 85% within the Torr range, while it is above 1×10 - ² Torr-2×10 - The trapping efficiency reaches over 90% within the Torr range, therefore this range is determined to be the optimal damping point range.

[0029] The specific type of atmospheric pressure ion source installed in the first-stage vacuum chamber can be one or more of the following: ESI (electrospray ionization), APCI (atmospheric pressure chemical ionization), or ICP (inductively coupled plasma) sources. These ion sources all operate under atmospheric pressure, and the generated ions need to enter the first-stage vacuum chamber through an atmospheric pressure interface. Different types of ion sources are suitable for the analysis of different types of samples; for example, ESI sources are suitable for polar compounds, APCI sources are suitable for moderately polar and non-polar compounds, and ICP sources are suitable for elemental analysis. Selecting the appropriate ion source configuration based on actual analytical needs expands the applicability of this ion trapping chamber system.

[0030] The dynamic gas replenishment unit includes a mass flow controller and a pulse solenoid valve. The mass flow controller precisely sets and regulates the gas flow rate entering the second-stage vacuum chamber, offering a wide flow adjustment range and high accuracy, enabling fine control of the replenishment volume. The pulse solenoid valve provides rapid on / off control based on the mass flow controller; when a sudden increase or decrease in the replenishment volume is needed, a rapid response can be achieved by adjusting the opening pulse width of the pulse solenoid valve. The pressure sensing unit uses a capacitive thin-film vacuum gauge, which offers advantages such as high measurement accuracy, fast response speed, and insensitivity to gas type, making it suitable for applications involving 10... - ³ Torr-10 - ² Precise measurement of the Torr pressure range.

[0031] The vacuum chambers at each stage are connected by connecting holes with a diameter of 0.5mm-3mm. These connecting holes serve as channels for gas flow and ion transport between adjacent chambers, and their diameter directly affects the flow conductance and pressure difference between the two stages. If the diameter is too small, ion transport efficiency will be affected; if the diameter is too large, the vacuum level of the lower-stage chamber will be difficult to maintain. Selecting a diameter within the 0.5mm-3mm range balances the requirements of ion transport and differential pumping. At least one connecting hole is equipped with an electrically controlled aperture adjustment mechanism, which can be a stepper motor-driven variable aperture or a piezoelectric ceramic-driven micro-orifice adjuster. The adaptive control unit controls this electrically controlled aperture adjustment mechanism to coordinate the effective aperture of the connecting hole and the pumping speed of the vacuum pump assembly. In addition to adjusting the inlet gas flow rate through the dynamic gas supply unit, the system can also influence the working pressure of the second-stage vacuum chamber by changing the flow conductance of the connecting hole and adjusting the pumping speed. This three-way coordinated control allows for faster and more precise establishment of the target pressure, overcoming the lag in response when relying solely on adjusting the gas supply flow rate. By controlling the interconnecting aperture, inlet gas flow rate, and molecular pump pumping speed in a coordinated manner, rather than simply increasing the pumping speed, the system achieves precise maintenance of multi-stage differential vacuum, thereby reducing power consumption and cost.

[0032] The collision reaction cell contains a linear ion trap, which consists of radially bound electrodes used to generate two-dimensional radial and axial bound electric fields. The multipole is a quadrupole, hexapole, or octapole; different numbers of poles result in different ion-binding characteristics, allowing selection based on specific needs. The dynamic gas supply unit introduces a buffer gas, a mixture of one or more of helium, nitrogen, or argon. Different types of buffer gases have different collision cross-sections and molecular weights, resulting in varying cooling effects on ions. For example, helium, with its small molecular weight, provides gentler collision cooling, while nitrogen and argon, with their larger molecular weights, offer higher collision cooling efficiency. The appropriate buffer gas type can be selected based on the mass range of the analyte.

[0033] This invention also provides a mass spectrometry analysis method based on the aforementioned ion trapping chamber system. This method first starts the vacuum pump assembly to evacuate each stage of the vacuum chamber, bringing the first-stage vacuum chamber to a level of 1×10⁻⁶. -4 Torr-5×10 -4 The operating pressure of Torr is 1×10⁻⁶ in the third-stage vacuum chamber. -6 Torr-5×10 -5 The working pressure of Torr is then adjusted. Buffer gas is then introduced into the second-stage vacuum chamber through a dynamic gas supply unit to bring the working pressure of the second-stage vacuum chamber to 5 × 10⁻⁶. - ³ Torr-5×10 -The target damping pressure window for ² Torr. After the initial pressure is established, the ion trapping state signal is acquired in real time through the ion trapping state monitoring unit. The adaptive control unit determines whether the current working pressure is at the optimal damping point based on this signal. If the current working pressure deviates from the optimal damping point, the adaptive control unit adjusts the gas supply parameters of the dynamic gas supply unit to bring the working pressure of the second-stage vacuum chamber back to the optimal damping point. After the optimal damping point stabilizes, ion collision cooling, ion trapping, and mass spectrometry analysis are performed under this pressure condition. The essence of this method is to change the pressure regulation from a preset fixed value to a dynamic regulation method based on ion trapping state feedback. Specifically, when the ion trapping state signal includes the ion cloud density signal and the ion oscillation damping time constant, when the ion cloud density signal exceeds the preset threshold, it means that the ion cloud is too dense and the space charge effect is enhanced. At this time, the adaptive control unit increases the gas supply velocity to raise the working pressure, enhances the collision cooling effect to compress the ion cloud volume, and thus weakens the space charge effect. When the ion oscillation damping time constant exceeds a preset threshold, it indicates that the ion cooling rate is too slow. Therefore, increasing the feed gas rate raises the working gas pressure, accelerating the ion kinetic energy damping. This analytical method allows the mass spectrometer to automatically maintain the optimal ion trapping state under various analytical conditions.

[0034] On the other hand, the present invention also provides the application of the ion trapping chamber system based on damping pressure adaptive control in the preparation of portable tandem mass spectrometers, on-site trace detection mass spectrometers, or synthetic biology online monitoring mass spectrometers.

[0035] The core innovation of this invention lies in the fact that the system further includes an ion trapping state monitoring unit and an adaptive control unit. The adaptive control unit is configured to receive an ion trapping state signal from the ion trapping state monitoring unit and adjust the gas supply parameters of the dynamic gas supply unit in real time according to the ion trapping state signal, so that the working gas pressure of the second-stage vacuum chamber is adaptively maintained at the optimal damping point within the target damping pressure window, and has the following advantages: (1) This invention proposes the concepts of damping pressure window and optimal damping point, breaking through the technical bias of traditional mass spectrometers pursuing high vacuum. By actively maintaining a medium pressure in the collision cell / ion trap region, sufficient collision cooling is achieved, which improves the ion trapping efficiency by more than 30% and the mass spectrometry resolution by more than 20%.

[0036] (2) The adaptive damping control technology of the present invention can adjust the damping pressure in real time according to the actual trapping state of ions, realizing on-demand damping. Compared with the constant pressure control of the prior art, it can achieve the best trapping effect under various analytical conditions, and the dynamic range is expanded by more than 2 times.

[0037] The interconnected control strategy of the present invention, which links the aperture of the connecting hole, the inlet gas flow rate, and the pumping speed of the molecular pump, achieves precise maintenance of multi-stage differential vacuum, increases the vacuum extraction speed by more than 100%, and reduces the power consumption and cost of the molecular pump.

[0038] The integrated precision milled cavity of the present invention reduces the weight by more than 50% while ensuring structural strength and vacuum sealing, making it suitable for the development of portable / on-site mass spectrometers.

[0039] Example 1: Ion trapping chamber system based on damping pressure adaptive control.

[0040] like Figure 1 , Figure 8 As shown, this embodiment provides an ion trapping cavity system 100 based on damped gas pressure adaptive control, including a first-stage vacuum cavity 101, a second-stage vacuum cavity 102 and a third-stage vacuum cavity 103 connected in sequence.

[0041] The first-stage vacuum chamber 101 is a roughly cylindrical cavity with an atmospheric piezoelectric spray ionization source (ESI source 104) at its front end. The ESI source 104 includes a spray needle 105 and a three-dimensional adjustable exhaust gas channel 106. The spray needle 105 forms an angle of 60°±2° with the horizontal plane. The first-stage vacuum chamber 101 is connected to a primary vacuum pump 109 via a connecting pipe. The primary vacuum pump 109 is a rotary oil-sealed pump with a pumping speed of 2 L / s and a working pressure maintained at 2×10⁻⁶. -4 Torr.

[0042] The second-stage vacuum chamber 102 is located downstream of the first-stage vacuum chamber 101 and is connected to the first-stage vacuum chamber 101 through a first connecting hole 110. The first connecting hole 110 is equipped with an electrically controlled aperture adjustment mechanism (such as...). Figure 4 As shown, for example, a variable aperture driven by a stepper motor can be electrically adjusted within the range of 0.5 mm to 2 mm. A collision reaction cell 111 is provided inside the second-stage vacuum chamber 102, and a linear ion trap 112 is provided within the collision reaction cell 111. The linear ion trap 112 consists of four hyperboloid electrode rods, each 100 mm long with an inscribed circle radius r0 = 4 mm. An radio frequency voltage of 1.0 MHz and an amplitude of 0~500 Vpp is applied to the surface of the electrode rods. The second-stage vacuum chamber 102 is connected to a secondary vacuum pump 113 via a connecting pipe. The secondary vacuum pump 113 is a turbomolecular pump with a pumping speed of 55 L / s and is connected to a dynamic gas supply unit 114 via a gas supply pipe.

[0043] The dynamic gas replenishment unit 114 includes a buffer gas cylinder 115, a mass flow controller 116 (MFC), and a pulse solenoid valve 117. The buffer gas cylinder 115 is filled with high-purity helium at a pressure of 0.2 MPa. The mass flow controller 116 has a flow rate adjustment range of 0.1 sccm to 10 sccm and an accuracy of ±0.5% FS. The pulse solenoid valve 117 has a response time of 1 ms and a minimum opening pulse width of 0.5 ms.

[0044] The second-stage vacuum chamber 102 is also equipped with a pressure sensing unit 118, which is a capacitive thin-film vacuum gauge that measures the working pressure of the second-stage vacuum chamber 102 in real time.

[0045] The third-stage vacuum chamber 103 is located downstream of the second-stage vacuum chamber 102 and is connected to the second-stage vacuum chamber 102 through a second connecting hole 119. The diameter of the second connecting hole 119 is 1 mm. A quadrupole mass analyzer 120 and an ion detector 121, such as an electron multiplier, are installed inside the third-stage vacuum chamber 103. The third-stage vacuum chamber 103 is connected to a third-stage vacuum pump 122 via a connecting pipe. The third-stage vacuum pump 122 is a turbomolecular pump with a pumping speed of 55 L / s and a working pressure maintained at 5 × 10⁻⁶ L / s. -6 Torr.

[0046] like Figure 2 , Figure 3 As shown, the system 100 further includes an ion trapping state monitoring unit 123 and an adaptive control unit 124. The ion trapping state monitoring unit 123 includes an ion cloud imaging module 125 and an ion signal analysis module 126. The ion cloud imaging module 125 is based on a charge-coupled device (CCD) ion fluorescence imaging system and is used to measure the full width at half maximum (FWHM) of the radial spatial distribution of the ion cloud. The ion signal analysis module 126 is used to measure the ion oscillation damping decay time constant τ. damp .

[0047] The adaptive control unit 124 is an embedded controller, such as an STM32F4 series microprocessor, whose input terminal receives ion trapping state signals (FWHM, τ) from the ion trapping state monitoring unit 123. damp ) and the measured air pressure value P from the air pressure sensing unit 118 meas The ion trapping state signals include FWHM and τdamp, and their output controls the flow setpoint Q of the mass flow controller 116. set The opening pulse width T of the pulse solenoid valve 117 pulse .

[0048] The adaptive control unit 124 executes the following control strategy: (1) Initialization phase: Set the target damping pressure window to 5×10 - ³ Torr to 5×10 - ² Torr, Full width at half maximum (FWHM) of the radial spatial distribution of the target ion cloud target =0.5 mm, target ion oscillation damping decay time constant τ damp , target =0.2 ms.

[0049] (2) Coarse adjustment stage: Read the measured air pressure value P of the air pressure sensing unit 118. meas If P meas Below the lower limit of the target damping pressure window (5×10) - ³ Torr), increase the MFC flow setting Q set If P meas Higher than the upper limit of the target damping pressure window (5×10) - ² Torr), reduce Q set The purpose of this stage is to quickly establish the target pressure range, with a control cycle of 50 ms.

[0050] (3) Fine-tuning stage: After the coarse-tuning stage is completed, fine-tuning based on the ion trapping state is performed. The measured FWHM and τ of the ion trapping state monitoring unit 123 are read. damp Calculate the comprehensive error index: E=α·(FWHM-FWHM target ) / FWHM target + β·(τ damp -τ damp , target ) / τ damp , target ; Where α=0.6 and β=0.4 are weighting coefficients. If E>0.1, increase Q. set Increase air pressure; if E < -0.1, decrease Q. set To reduce air pressure; if |E|≤0.1, maintain the current Q. set This stage aims to optimize the ion trapping state, with a control period of 20ms.

[0051] (4) Dynamic tracking stage: During the mass spectrometry analysis, the ion cloud parameters change with the scanning process. The adaptive control unit 124 continuously updates the ion trapping state signal at a frequency of 100 Hz and adjusts Q in real time. set and T pulse This ensures that the overall error index E remains within ±0.1.

[0052] The measurement method for the ion trapping state parameters is as follows: (e.g.) Figure 5As shown, the full width at half maximum (FWHM) of the radial spatial distribution of the ion cloud was measured using a CCD-based ion fluorescence imaging system with an imaging resolution of 10 μm. The damping decay time constant of the ion oscillation was measured by applying a 10 μs pulse excitation voltage to the linear ion trap to induce radial oscillations in the ions. The decay process of the oscillation signal was then recorded by an ion detector, and the damping time constant was obtained by exponential fitting.

[0053] Example 2: Mass spectrometry analysis method.

[0054] Mass spectrometry analysis was performed using the ion trapping chamber system 100 described in Example 1, and the specific steps are as follows: Step S1: After system startup, first turn on the primary vacuum pump 109, secondary vacuum pump 113, and tertiary vacuum pump 122 to evacuate each vacuum chamber. After approximately 30 minutes, the first-stage vacuum chamber 101 reaches a vacuum level of 2 × 10⁻⁶. -4 Torr, the third-stage vacuum chamber 103 reaches 5×10 -6 Torr.

[0055] Step S2: Activate the dynamic gas supply unit 114 to introduce helium buffer gas into the second-stage vacuum chamber 102, and adjust the MFC flow rate to achieve a gas pressure of 1×10⁻⁶ in the second-stage vacuum chamber 102. - ² Torr, target damping pressure window 5×10 - ³~5×10 - Within the range of ² Torr.

[0056] Step S3: Start the ESI source 104 and atomize and ionize the sample solution at a flow rate of 5 μL / min through the spray needle 105. The sample solution can be a 1 ppb reserpine methanol solution. Ions are transported by ion guide (hexapole) in the first-stage vacuum chamber 101 and enter the collision reaction cell 111 of the second-stage vacuum chamber 102 through the first connecting hole 110. In the linear ion trap 112, ions are subjected to a damping pressure (1×10⁻⁶). - Under the influence of Torr, the kinetic energy decreases rapidly due to sufficient impact cooling, and the kinetic energy is effectively trapped in the central region of the trap.

[0057] Step S4: The ion trapping state monitoring unit 123 monitors the ion cloud parameters in real time, and the adaptive control unit 124 dynamically adjusts the MFC flow rate according to the monitoring signal to maintain the damping pressure at the optimal damping point, approximately 1.5 × 10⁻⁶. - ² Torr.

[0058] Step S5: MS / MS analysis in linear ion trap 112: First, the precursor ion is isolated by radio frequency voltage scanning with a mass-to-charge ratio of 609. The test substance is reserpine. Then, an auxiliary AC voltage is applied to excite the precursor ion to collide and dissociate with helium gas, generating fragment ions. Due to sufficient collision cooling under damped gas pressure, the fragment ions are efficiently captured.

[0059] Step S6: Scan the radio frequency voltage of the linear ion trap 112 to eject fragment ions in order of mass-to-charge ratio to the ion detector 121 for detection, and obtain a secondary mass spectrum.

[0060] Using the above method, 10 replicate analyses were performed on a 1 ppb reserpine standard solution. The average signal-to-noise ratio (S / N) was 285, and the relative standard deviation was 3.2%. Under the same conditions, the pressure in the second-stage chamber was fixed at 5 × 10⁻⁶ under conventional constant pressure control. -4 Compared to Torr's analysis results, the method of this invention improves the S / N ratio by approximately 35% and expands the dynamic range by 2.5 times.

[0061] Comparison of ion trapping efficiency under different damping pressures: To verify the effectiveness of the damping pressure window, while keeping other conditions constant, the working pressure of the second-stage vacuum chamber 102 was changed, and the ion trapping efficiency, i.e., the ratio of the emitted ion signal intensity to the incident ion signal intensity, was measured. The results are as follows: Figure 6 As shown in Table 1: Table 1 Ion trapping efficiency under different damping pressures

[0062] As can be seen from Table 1, when the damping pressure is 5×10 - ³ Torr to 5×10 - Within the 2 Torr range, the ion trapping efficiency is higher than 85%, significantly higher than under high vacuum conditions, 5×10 -4 Torr, imprisonment efficiency 45%. Optimal damping point occurs at 1×10. - ² Torr to 2×10 - Within the 2 Torr range, the imprisonment efficiency reaches over 90%. When the air pressure further increases to 1×10... - ¹ At Torr, the trapping efficiency drops to 68% due to increased ion scattering loss caused by excessive collisions.

[0063] The experimental results above demonstrate that the damping pressure window concept proposed in this invention has a clear physical basis and technical effect. By adaptively controlling the damping pressure to be maintained near the optimal damping point, it can significantly improve ion trapping efficiency and mass spectrometry analysis performance.

[0064] Furthermore, to verify the versatility of this invention for ions with a wide mass range, at the optimal damping point (1.5 × 10⁻⁶), - At a pressure of 2 Torr, the trapping efficiency of ions with different mass-to-charge ratios was tested. The results showed that the trapping efficiency of ions with m / z=100 was 89%, that of ions with m / z=500 was 92%, and that of ions with m / z=2000 was 87%. These data indicate that the damping pressure adaptive control technology of this invention has a good trapping effect on ions of different masses, with minimal mass discrimination effect.

[0065] The rapid extraction performance of the integrated chamber: This embodiment verifies the rapid extraction performance of the integrated cavity of the present invention. An integrated three-stage differential vacuum cavity is used, made of aerospace-grade 6061-T6 aluminum alloy, precision milled in one piece using five axes, with an inner wall surface roughness Ra of 1.2 μm. It is equipped with a single-port turbomolecular pump with a pumping speed of 55 L / s as the secondary and tertiary vacuum pumps, and a rotary oil-sealed pump with a pumping speed of 2 L / s as the primary vacuum pump.

[0066] Experimental results show that the working pressure of the third-stage vacuum chamber was 5 × 10⁻⁶ molten gas from atmospheric pressure. -6 The time required for Torr is 3.5 hours. In comparison, using a traditional segmented welded cavity and a vacuum pump assembly of the same specifications, the traditional segmented welded cavity consists of three independent cavities connected by flanges, with a total number of sealing surfaces three times that of the cavity of this invention, and takes 7-8 hours to achieve the same vacuum level. The integrated cavity design of this invention increases the vacuum extraction speed by approximately 120%.

[0067] Furthermore, by employing a coordinated control strategy involving the aperture of the connecting hole, the inlet gas flow rate, and the pumping speed of the molecular pump, this invention achieves precise maintenance of the working gas pressure in each stage of the cavity: the first-stage vacuum cavity has a pressure of 2×10⁻⁶. -4 Torr fluctuation range ±5%, second-stage vacuum chamber 1×10 - ² Torr fluctuation range ±8%, third-stage vacuum chamber 5×10 -6 Torr fluctuation range ±10%.

[0068] Performance comparison between adaptive control and constant voltage control: This embodiment compares the analytical performance of the adaptive damping control (ADR) of the present invention with that of the prior art constant pressure control (CP) under different sample concentration conditions. The test samples were reserpine standard solutions of different concentrations, such as 0.1 ppb, 1 ppb, 10 ppb, 100 ppb, and 1 ppm, and six replicate analyses were performed at each concentration.

[0069] like Figure 7As shown, the results indicate that at low concentrations (0.1 ppb–1 ppb), the S / N values ​​of ADR and CP are similar because the ion cloud density is low and the space charge effect is not significant, allowing both control methods to achieve good trapping effects. At medium concentrations (10 ppb–100 ppb), the S / N value of ADR is 25%–40% higher than that of CP. This is because ADR automatically adjusts the damping pressure according to the increase in ion cloud density, effectively suppressing the space charge effect. At a high concentration (1 ppm), the S / N value of ADR is more than 55% higher than that of CP, and ADR does not exhibit mass shift in the mass spectrum peak, while the mass shift under CP conditions reaches 0.15 Da, demonstrating the significant advantage of adaptive control in the analysis of high-concentration samples.

[0070] In summary, this invention solves the technical problems of insufficient collision cooling, space charge effect limiting dynamic range, and large ion transport loss in existing mass spectrometer vacuum chamber systems by proposing a damped pressure window and adaptive damping control. Through an integrated chamber structure, an electrically controlled aperture adjustment mechanism, and a three-way linkage control strategy, an optimal balance between ion collision cooling and transport efficiency is achieved, significantly improving the sensitivity, dynamic range, and reliability of trace / ultra-trace mass spectrometry analysis.

[0071] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An ion trapping cavity system based on damped gas pressure adaptive control, characterized in that, It includes a first-stage vacuum chamber, a second-stage vacuum chamber, a third-stage vacuum chamber, and a dynamic gas replenishment unit connected in sequence; The second-stage vacuum chamber is equipped with a collision reaction cell, which contains a multipole or a linear ion trap. The dynamic gas supply unit is connected to the second-stage vacuum chamber. The dynamic gas supply unit introduces buffer gas into the second-stage vacuum chamber to maintain the working gas pressure in the chamber at 5×10⁻⁶. - ³ Torr-5×10 - Within the target damping pressure window of ² Torr.

2. The ion trapping cavity system based on damped gas pressure adaptive control as described in claim 1, characterized in that, The system also includes vacuum pump units connected to each vacuum chamber, and pressure sensing units connected to each vacuum chamber.

3. The ion trapping cavity system based on damped gas pressure adaptive control as described in claim 2, characterized in that, The system also includes an ion trapping state monitoring unit and an adaptive control unit. The adaptive control unit is connected to the ion trapping state monitoring unit and the dynamic gas replenishment unit, respectively. The adaptive control unit receives the ion trapping state signal from the ion trapping state monitoring unit and adjusts the gas replenishment parameters of the dynamic gas replenishment unit according to the ion trapping state signal, so that the working gas pressure of the second-stage vacuum chamber is maintained at the optimal damping point within the target damping pressure window.

4. The ion trapping cavity system based on damped gas pressure adaptive control as described in claim 3, characterized in that, The ion trapping state monitoring unit monitors at least one of the following parameters: radial spatial distribution half-width at half-maximum of ion cloud, ion oscillation damping decay time constant, ion cloud density space charge effect index, and ion trapping potential depth; the adaptive control unit adjusts the gas supply speed of the dynamic gas supply unit according to the deviation between the ion trapping state signal and the preset target value through a PID control algorithm or a fuzzy control algorithm.

5. The ion trapping cavity system based on damped gas pressure adaptive control as described in claim 1, characterized in that, The working pressure of the first-stage vacuum chamber is 1×10 -4 Torr-5×10 -4 Torr, the working pressure of the third-stage vacuum chamber is 1×10⁻⁶. -6 Torr-5×10 -5 Torr; The optimal damping point of the second-stage vacuum chamber is 1×10 - ² Torr-2×10 - ²Torr.

6. The ion trapping cavity system based on damped gas pressure adaptive control as described in claim 1, characterized in that, An atmospheric pressure ion source is provided in the first-stage vacuum chamber. The atmospheric pressure ion source is one or more of ESI source, APCI source or ICP source.

7. The ion trapping cavity system based on damped gas pressure adaptive control as described in claim 2, characterized in that, The dynamic air replenishment unit includes a mass flow controller and a pulse solenoid valve, and the air pressure sensing unit is a capacitive thin-film vacuum gauge.

8. The ion trapping cavity system based on damped gas pressure adaptive control as described in claim 3, characterized in that, The vacuum chambers at each level are connected by connecting holes with a diameter of 0.5mm-3mm, and at least one connecting hole is equipped with an electrically controlled aperture adjustment mechanism; the adaptive control unit also controls the electrically controlled aperture adjustment mechanism to coordinately adjust the effective aperture of the connecting hole and the pumping speed of the vacuum pump group.

9. The ion trapping cavity system based on damped gas pressure adaptive control as described in claim 1, characterized in that, The collision reaction pool is equipped with the linear ion trap; the multipole is a quadrupole, hexapole, or octapole; the buffer gas introduced by the dynamic gas replenishment unit is one or more of helium, nitrogen, or argon.

10. A mass spectrometry analysis method for an ion trapping chamber system based on adaptive damping pressure control as described in any one of claims 1-9, characterized in that, Includes the following steps: The vacuum pump unit is started to evacuate each stage of the vacuum chamber, so that the first stage vacuum chamber reaches a vacuum level of 1×10⁻⁶. -4 Torr-5×10 - 4 The operating pressure of Torr is 1×10⁻⁶ in the third-stage vacuum chamber. -6 Torr-5×10 -5 Torr's operating air pressure; Buffer gas is introduced into the second-stage vacuum chamber through a dynamic gas replenishment unit, so that the working pressure of the second-stage vacuum chamber reaches the target damping pressure window, which is 5×10⁻⁶. - ³ Torr-5×10 - ² Torr; Ion trapping status signals are acquired in real time through the ion trapping status monitoring unit; The adaptive control unit determines whether the current working gas pressure is at the optimal damping point based on the ion trapping state signal. If the current working gas pressure deviates from the optimal damping point, the adaptive control unit adjusts the gas replenishment parameters of the dynamic gas replenishment unit to bring the working gas pressure of the second-stage vacuum chamber back to the optimal damping point. Ion collision cooling, ion trapping, and mass spectrometry analysis were performed at the optimal damping point.

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