Quadrupole collision pool ion cleaning method based on axial potential difference

Abstract

The invention discloses a quadrupole collision pool ion cleaning method based on an axial potential difference, which comprises the following steps: establishing a constant axial potential difference in a quadrupole collision pool to form a continuous potential gradient from an inlet to an outlet; after a sample is subjected to ionization and mass selection, primary ions with a specific mass-to-charge ratio enter a collision pool and collide with collision gas to induce dissociation to generate product ions, and the product ions move towards an outlet under the action of axial potential difference; the system monitors the ion signal intensity in real time, and stops inputting the primary ions to enter a cleaning stage after a preset threshold value is reached; and keeping the axial potential difference constant during cleaning, and judging that the cleaning is completed when the ion abundance is reduced to be below background noise. The continuous active driving force is provided through the axial potential difference, the defects that traditional passive cleaning is low in efficiency and incomplete are overcome, the cleaning time is remarkably shortened, interference of residual ions is eliminated, the analysis accuracy and efficiency are improved, and the method is particularly suitable for high-throughput tandem mass spectrometry.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of quadrupole mass spectrometer, in particular to a quadrupole collision cell ion cleaning method based on axial potential difference. BACKGROUND

[0002] As one of the core technologies of modern analytical chemistry, quadrupole mass spectrometer plays an irreplaceable role in the fields of chemical analysis, biomedical, environmental monitoring, food safety, etc. Especially, the development of quadrupole collision cell technology makes tandem mass spectrometry (MS / MS) analysis possible, greatly improving the selectivity and accuracy of complex sample analysis. Quadrupole collision cell system can fragment the precursor ions into characteristic product ions through collision-induced dissociation (CID) technology, providing rich information for the structural identification and quantitative analysis of compounds. This technology has important application value in high-precision analysis fields such as pesticide residue detection, drug metabolism research, proteomics analysis, and metabolomics research, and has become an important direction of the development of modern mass spectrometry technology.

[0003] The existing quadrupole collision cell ion cleaning technology mainly relies on vacuum pumping and natural diffusion to remove residual ions in the collision cell. In the traditional method, after the completion of the collision reaction, the residual precursor ions and product ions are gradually removed from the collision cell by stopping ion input and relying on the pumping action of the vacuum pump. This process usually takes tens of milliseconds or even longer. Some improved technical solutions attempt to improve the cleaning effect by prolonging the pumping time, adjusting the radio frequency voltage, or changing the collision gas flow, but these passive cleaning methods still essentially rely on the natural diffusion and vacuum pumping of ions. Some advanced systems use pulsed gas cleaning technology to periodically introduce cleaning gas into the collision cell to assist ion removal, but this method also lacks active driving of ions and requires a complex gas control system.

[0004] In summary, the above existing technologies have two key technical defects. The first problem is low cleaning efficiency. Since the existing methods lack effective active driving mechanisms, they only rely on passive vacuum pumping and natural diffusion, resulting in a cleaning time of tens of milliseconds, which seriously affects the analysis efficiency, especially in high-throughput applications that require continuous analysis of multiple precursor ions. This inefficient cleaning process becomes a bottleneck in the entire analysis process. The second problem is serious color interference (cross-contamination). Due to incomplete cleaning, residual precursor ions and product ions will interfere with subsequent analysis, causing false peaks in the product ion mass spectrum, which seriously affects the accuracy of qualitative and quantitative analysis. This phenomenon is particularly evident in continuous multi-target analysis, which can lead to false analysis results and misjudgments.

[0005] These two technical defects have become important obstacles restricting the further development and popularization of quadrupole MS / MS technology, and it is urgent to develop new active driving cleaning technology to solve the shortcomings of the existing technology. SUMMARY

[0006] The purpose of the present application is to provide a quadrupole collision cell ion cleaning method based on axial potential difference, which can quickly and completely remove residual ions, effectively eliminate color interference, and significantly improve analysis efficiency and accuracy.

[0007] To achieve the above purpose, the present application provides the following technical solution: a quadrupole collision cell ion cleaning method based on axial potential difference, comprising the following steps: Step 1: ionizing the sample to be analyzed in the ion source to generate ions, selecting the primary ions of a specific mass-to-charge ratio through a quadrupole mass analyzer; Step 2: establishing a constant axial potential difference in the collision cell of the quadrupole, so that the collision cell forms a continuous potential gradient from the inlet end to the outlet end; Step 3: the primary ions enter the collision cell and collide with the collision gas to induce dissociation reaction, producing product ions, which move towards the outlet under the action of the axial potential difference; Step 4: real-time monitoring of the ion signal intensity in the collision cell, when the signal intensity reaches the preset threshold, stop inputting the primary ions, and enter the cleaning preparation stage; Step 5: keeping the axial potential difference in the collision cell constant, driving the residual ions to the outlet by the potential driving effect to realize cleaning; Step 6: monitoring the change of ion abundance, when the ion abundance decreases below the background noise, judging that the cleaning process is completed; Step 7: after the system confirms that the cleaning is completed, automatically preparing to enter the next analysis cycle or continuing the analysis process of the current sample.

[0008] Preferably, in step 2, the establishment of the axial potential difference is realized by superimposing a direct current bias voltage on each rod electrode of the quadrupole, or by applying different voltages to the lens system at the inlet and outlet of the collision cell, so that a constant potential difference of 5V is formed between the inlet and outlet of the collision cell, and the axial potential difference remains stable and unchanged during the entire collision reaction and cleaning process.

[0009] Preferably, in step 3, after the primary ions enter the collision cell, the pressure of the collision gas in the collision cell is controlled to be 0.5 to 5 mTorr, so that the primary ions collide with the collision gas molecules multiple times, and the collision energy is controlled in the range of 10 to 100 eV, and the generated product ions continuously migrate towards the outlet of the collision cell under the action of the axial potential difference.

[0010] Preferably, in step 4, the ion signal intensity is collected in real time by the ion detector arranged at the outlet end of the collision cell, and the collected signal is compared with a preset threshold value, when the signal intensity exceeds the threshold value for N consecutive measurements, the input of the primary ions is stopped, N is an integer between 2 and 5, and the preset threshold value is 80%-120% of the theoretical intensity of the target product ion.

[0011] Preferably, in step 5, the cleaning process is started within 0.1-1 ms after the primary ions are stopped, the amplitude of the quadrupole radio frequency voltage is kept unchanged at 100-1000 V and the frequency is kept unchanged at 0.5-3 MHz during the cleaning process, and the axial potential difference between the inlet and the outlet of the collision cell is kept constant, and the cleaning duration T is 5-50 ms.

[0012] Preferably, in step 6, the ion detector arranged at the outlet end of the collision cell is used to continuously monitor the ion abundance at a sampling frequency of 1-10 kHz, and the moving average of the ion abundance is calculated once at a time interval of 0.1-1 ms; when M consecutive moving averages are all lower than 110% of the initial background noise level obtained by blank measurement before cleaning, it is determined that the cleaning process is completed, wherein M is an integer between 5 and 10.

[0013] Preferably, in step 7, after confirming that the cleaning process is completed, the system performs the following preparation operations: reset the counter of the ion detector to zero; reset the preset threshold value for product ion collection; restore the primary ion transmission channel to standby state; and determine whether the next target ion needs to be analyzed according to the preset analysis sequence, if a new target ion needs to be analyzed, the working parameters of the quadrupole mass analyzer are adjusted to the set value corresponding to the mass-to-charge ratio of the new target ion, and after the parameter adjustment is completed, a ready signal is sent to allow the next batch of primary ions to enter the collision cell.

[0014] Compared with the prior art, the method has the advantages that: by establishing a constant axial potential difference in the collision cell, a continuous potential gradient is formed to provide a sustained directional driving force for the ions, which fundamentally changes the limitations of the traditional passive cleaning method which only relies on vacuum extraction and natural diffusion. In the collision-induced dissociation process, the axial potential difference plays a dual role, accelerating the migration of product ions to the outlet and reducing the residence time of ions in the collision cell, and continuing to provide driving force in the subsequent cleaning stage to ensure that the residual ions can be quickly and completely removed.

[0015] This method employs real-time monitoring and intelligent control, dynamically determining the optimal cleaning timing by monitoring ion signal intensity. This avoids the efficiency losses or inadequate cleaning that may result from fixed-time cleaning. The entire cleaning process maintains a constant potential difference, eliminating the need for complex parameter adjustments or additional hardware configurations, significantly simplifying system design and operation. Continuous monitoring of ion abundance until it decreases to the background noise level ensures thorough cleaning, effectively eliminating spectral interference caused by residual ions. This significantly improves the accuracy and reproducibility of subsequent analyses, making this method particularly suitable for high-throughput, multi-target continuous analysis applications. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Fig. 1 This is a schematic diagram of the process of the present invention; Fig. 2 This is a schematic diagram of the collision pool system in this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Example 1: As Figs. 1-2 As shown, a quadrupole collision cell ion cleaning method based on axial potential difference includes the following steps: Step 1: Ionize the sample to be analyzed in the ion source to generate ions, which are then selected by a quadrupole mass analyzer to obtain primary ions with a specific mass-to-charge ratio. Step 2: Establish a constant axial potential difference in the collision cell of the quadrupole, so that a continuous potential gradient is formed from the inlet end to the outlet end of the collision cell; Step 3: Primary ions enter the collision cell and undergo a collision-induced dissociation reaction with the collision gas to produce product ions. The product ions move towards the outlet direction under the action of the axial potential difference. Step 4: Monitor the ion signal intensity in the collision cell in real time. When the signal intensity reaches the preset threshold, stop inputting primary ions and enter the cleaning preparation stage. Step 5: Maintain a constant axial potential difference within the collision cell, and actively drive the residual ions to the outlet for discharge through potential-driven action to achieve cleaning; Step 6: Monitor changes in ion abundance. When the ion abundance drops below the background noise level, the cleaning process is considered complete. Step 7: After the system confirms that the cleaning is complete, it will automatically prepare to enter the next analysis cycle or continue the analysis process of the current sample.

[0020] Example 2: Figs. 1-2 As shown, unlike Example 1, in step 2, the axial potential difference is established by superimposing a DC bias voltage on each electrode of the quadrupole, or by applying different voltages to the lens system at the inlet and outlet of the collision pool, so that a constant potential difference of 5V is formed between the inlet and outlet of the collision pool, and this axial potential difference remains stable throughout the entire collision reaction and cleaning process.

[0021] In step 2, the establishment of the axial potential difference adopts two optional implementation methods. The first method is to superimpose a DC bias voltage on each electrode of the quadrupole. Specifically, on the basis of the original radio frequency voltage, a DC bias decreasing along the axial direction is applied to the four electrodes, so that the electrode at the inlet end of the collision cell has a higher DC potential and the electrode at the outlet end has a lower DC potential, thereby forming an axial electric field inside the collision cell. This method makes full use of the existing quadrupole electrode structure, without the need to add additional electrode components, achieving low cost and high system integration.

[0022] The second method is to establish a potential difference through the lens system at both ends of the collision pool. A higher voltage is applied to the inlet lens and a lower voltage is applied to the outlet lens. The 5V voltage difference between the two generates a uniformly distributed axial electric field inside the collision pool. The advantage of this method is that it does not affect the radio frequency confinement performance of the quadrupole itself, and the electric field distribution is more uniform and controllable.

[0023] Both of the above methods can maintain a constant 5V potential difference. This constant driving electric field continues to act throughout the analysis and cleaning process, without interfering with the collision-induced dissociation process, and can provide a stable axial driving force for the ions.

[0024] In step 3, after the primary ions enter the collision cell, the pressure of the collision gas in the collision cell is controlled at 0.5 to 5 mTorr, so that the primary ions collide with the collision gas molecules multiple times. The collision energy is controlled in the range of 10 to 100 eV. The product ions produced continue to migrate towards the outlet of the collision cell under the action of the axial potential difference.

[0025] The collision gas pressure is controlled in the range of 0.5-5 mTorr, which is optimized to ensure sufficient collision frequency for sufficient fragmentation of primary ions and avoid ion scattering and reduced transmission efficiency caused by excessive pressure. Under this pressure condition, the average free path of primary ions in the collision cell is moderate, which can effectively collide with collision gas molecules multiple times to achieve ideal fragmentation effect.

[0026] The collision energy is set in the range of 10-100 eV, covering the complete energy interval from soft collision to hard collision, so that the method can adapt to the analysis needs of different types of compounds. Lower collision energy is suitable for retaining more complete molecular structure information, while higher collision energy can produce more fragment ions for structure identification. During the entire collision process, the axial potential difference continuously plays a role, so that the newly generated product ions immediately obtain the driving force towards the outlet direction, avoiding the accumulation and secondary collision of product ions in the collision cell, which not only improves the transmission efficiency of product ions, but also ensures the clarity and resolution of mass spectrum.

[0027] Example Three: as shown in Figs. 1-2 different from Example Two, in step 4, the ion signal intensity is collected in real time by the ion detector arranged at the outlet end of the collision cell, and the collected signal is compared with the preset threshold value. When the signal intensity exceeds the threshold value for N consecutive measurements, the control system stops inputting primary ions. N is an integer between 2 and 5, and the preset threshold value is 80%-120% of the theoretical intensity of the target product ion.

[0028] By setting the ion detector at the outlet end of the collision cell for real-time monitoring, the system can directly obtain the actual generation of product ions. This control method based on actual signal feedback is more scientific and reasonable than fixed time control. By setting the judgment condition of exceeding the threshold value for N consecutive measurements, the misjudgment caused by signal fluctuation or accidental noise is effectively avoided. N is set to an integer between 2 and 5, which ensures the reliability of the judgment and does not prolong the analysis time due to excessive verification.

[0029] Theoretical intensity refers to the peak height value of the product ion measured using a standard sample of known concentration under the same ion source conditions, collision energy, and detector settings. Peak height rather than peak area is selected as the determination standard because peak height can more quickly reflect changes in ion signals in real-time monitoring. The preset threshold range is set to 80-120% of the theoretical intensity of the target product ion. This range is selected by fully considering various factors in actual analysis: the lower limit of 80% ensures sufficient product ion generation to guarantee the accuracy of subsequent quantitative analysis; and the upper limit of 120% prevents ion saturation or detector overload that may be caused by excessive reaction. This threshold setting method based on relative intensity can automatically adapt to different concentrations of samples and different ionization efficiencies of compounds, without the need to adjust parameters for each sample individually. When the system detects that the product ion signal reaches the preset condition, it immediately stops the primary ion input, which not only ensures sufficient collision reaction but also avoids unnecessary ion accumulation, creating ideal conditions for subsequent efficient cleaning.

[0030] In step 5, the cleaning process is started within 0.1-1 ms after stopping the primary ion input. During the cleaning process, the amplitude of the quadrupole radio frequency voltage is maintained at 100-1000 V, the frequency is maintained at 0.5-3 MHz, the axial potential difference between the collision cell inlet and outlet is maintained constant, and the cleaning duration T is 5-50 ms.

[0031] The quadrupole electrodes are divided into multiple axial segments, the front segment is mainly used for ion confinement with RF, and the rear segment is superimposed with a DC gradient for axial driving. The segments are isolated by insulating rings to reduce the interference of RF on the DC electric field.

[0032] The cleaning process is started within 0.1-1 ms after stopping the primary ion input. This millisecond-level fast response avoids the diffusion and redistribution of residual ions in the collision cell, ensuring the cleaning efficiency.

[0033] The quadrupole radio frequency voltage parameters are kept stable during the cleaning process, with an amplitude of 100-1000 V and a frequency of 0.5-3 MHz, which covers the working parameters of conventional quadrupole mass spectrometers. This parameter stability is of great significance: the stability of the radio frequency voltage ensures the continuity of the radial confinement electric field, so that the residual ions are always confined near the central axis of the quadrupole, preventing the diffusion of ions to the electrode surface and causing pollution or loss. At the same time, maintaining the axial potential difference constant ensures the continuous action of the cleaning driving force, so that the residual ions move quickly along the established path under the dual action of radial confinement and axial driving.

[0034] The cleaning duration is set to 5-50 ms, which fully embodies the advantages of the axial potential difference active driving. Under the continuous action of 5 V potential difference, the ions obtain directional acceleration, and the cleaning efficiency is improved by an order of magnitude compared with the traditional passive method. The entire cleaning process does not require any parameter adjustment or switching, simplifying the control logic and improving the system stability. At the same time, it significantly shortens the dead time between two analyses, greatly improves the overall analysis efficiency, and is particularly suitable for high-throughput analysis applications.

[0035] In step 6, the ion detector set at the outlet end of the collision cell continuously monitors the ion abundance at a sampling frequency of 1-10 kHz, and calculates the moving average of the ion abundance at a time interval of 0.1-1 ms; when the continuous M moving average values are all lower than 110% of the initial background noise level obtained by blank measurement before cleaning, the cleaning process is determined to be completed, wherein M is an integer between 5 and 10.

[0036] The ion detector continuously monitors at a high sampling frequency of 1-10 kHz, which can capture the rapid changes in ion abundance and accurately reflect the dynamic characteristics of the cleaning process. The strategy of calculating the moving average at a time interval of 0.1-1 ms has double advantages: on the one hand, it effectively filters out random noise and transient fluctuations, improving the stability of the determination; on the other hand, it maintains sufficient time resolution to respond to the actual trend of ion abundance changes in a timely manner.

[0037] The initial background noise level refers to the baseline signal intensity detected by the detector when only collision gas (argon or nitrogen) is introduced into the collision cell without introducing any ions before the analysis begins. This value reflects the inherent noise level of the system, including electronic noise, background signal of collision gas, and dark current of the detector, etc. The determination criterion is set to be 110% of the initial background noise level, which is the root mean square value of the background signal. Specifically, 1000 data points are continuously collected without introducing any ions, and the standard deviation is calculated as the initial background noise. The root mean square value is selected instead of the peak-to-peak value because the root mean square value can more stably represent the statistical characteristics of noise and is less affected by accidental extreme values. This determination method based on relative threshold fully considers the differences in background noise under different instrument states and environmental conditions, and obtains the reference value through blank measurement before cleaning, ensuring the adaptability of the determination criterion. The threshold of 110% ensures the thoroughness of cleaning, and avoids unnecessary extension of cleaning time due to too strict standards. The M value is set to 5-10 consecutive points, which provides sufficient statistical reliability and effectively prevents false judgments caused by accidental factors.

[0038] Therefore, the multiple verification mechanism ensures that the cleaning is completed only when the ion abundance is stably reduced to near the background level, providing a clean measurement environment for subsequent analysis and fundamentally eliminating the chromatographic interference problem caused by residual ions.

[0039] In step 7, after confirming that the cleaning process is complete, the system performs the following preparation operations: Clear the counter of the ion detector; Reset the preset threshold for product ion collection; Restore the primary ion transmission channel to standby state; And according to the preset analysis sequence, determine whether the next target ion needs to be analyzed, if the new target ion needs to be analyzed, adjust the working parameters of the quadrupole mass analyzer to the set value corresponding to the mass-to-charge ratio of the new target ion, and after completing the parameter adjustment, send a ready signal to allow the next batch of primary ions to enter the collision cell.

[0040] The operation of clearing the counter of the ion detector eliminates the residual data of the previous analysis, ensuring that the new analysis starts from zero baseline, avoiding errors caused by data superposition. Resetting the preset threshold for product ion collection reflects the adaptive ability of the system, which can adjust the collection parameters according to the characteristics of different target compounds to optimize the sensitivity and dynamic range of each analysis. Restoring the primary ion transmission channel to standby state ensures that the ion optical system is in the best working condition, ready to receive new ion flow at any time. The system automatically determines the subsequent task according to the preset analysis sequence, and this intelligent sequence control greatly simplifies the operation process, especially suitable for batch analysis of multi-component samples. When switching to a new target ion, the system automatically adjusts the working parameters of the quadrupole mass analyzer to match the new mass-to-charge ratio, and this automatic parameter switching avoids manual intervention, improving the analysis efficiency and consistency.

[0041] Example 4: Use the method of example 3 to perform the following test experiment.

[0042] 1. Comparison of cleaning effects under different axial potential differences Experimental conditions: Test sample: reserpine standard (m / z 609→195) Collision gas: argon, pressure 2 mTorr Collision energy: 35 eV Initial ion intensity: 1.0 x 10 6 cps Experimental results:

[0043] 2. Cross-contamination test for continuous multi-component analysis Test sample group: Caffeine (m / z 195→ 138); Reserpine (m / z 609→ 195); Diazepam (m / z 285→ 154); Chloramphenicol (m / z 321→ 152); Experimental protocol: 30 seconds analysis per sample, switch to next sample after analysis, residual signal of previous sample is monitored.

[0044] Results comparison:

[0045] 3. Cleaning performance in different matrix samples Sample type: Plasma extract; Urine extract; Environmental water sample; Target analyte: Atropine (m / z 290→ 124) Cleaning effect comparison:

[0046] 4. Long time running stability test Test conditions: Continuous running for 8 hours; 60 samples analyzed per hour; Axial potential difference: 5V; Stability data:

[0047] Conclusion: The experimental data show that the cleaning method using 5V axial potential difference, compared with the traditional method, the cleaning time is shortened by 85-90%, the residual ion is reduced by more than 99%, and the analysis efficiency and accuracy are significantly improved.

[0048] The above only describes the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method of quadrupole rod collision cell ion cleaning based on axial potential difference, characterized by, The method comprises the following steps: Step 1: ionizing the sample to be analyzed in an ion source to generate ions, selecting ions of a specific mass-to-charge ratio through a quadrupole mass analyzer, and obtaining primary ions; Step 2: establishing a constant axial potential difference in the collision cell of the quadrupole, so that the collision cell forms a continuous potential gradient from the inlet end to the outlet end; Step 3: the primary ions enter the collision cell, collide with the collision gas to induce a collision-induced dissociation reaction, and product ions are generated and move towards the outlet under the action of the axial potential difference; Step 4: the ion signal intensity in the collision cell is monitored in real time, and when the signal intensity reaches a preset threshold, the input of the primary ions is stopped, and a cleaning preparation stage is entered; Step 5: the axial potential difference in the collision cell is kept constant, and the residual ions are actively driven to the outlet by the potential driving effect to realize cleaning; Step 6: the ion abundance is monitored, and when the ion abundance is reduced to below the background noise, it is judged that the cleaning process is completed; Step 7: after confirming that the cleaning process is completed, the system automatically prepares to enter the next analysis cycle or continues the analysis process of the current sample.

2. A method for quadrupole rod collision cell ion cleaning based on axial potential difference according to claim 1, characterized in that, In step 2, the establishment of the axial potential difference is achieved by superimposing a direct current bias voltage on each rod electrode of the quadrupole, or by applying different voltages to the lens system at the inlet and outlet of the collision cell, so that a constant potential difference of 5V is formed between the inlet and outlet of the collision cell, and the axial potential difference remains stable and unchanged during the entire collision reaction and cleaning process.

3. The method of claim 1, wherein the method is a quadrupole collision cell ion cleaning method based on axial potential difference. In step 3, after the primary ions enter the collision cell, the pressure of the collision gas in the collision cell is controlled to be 0.5-5mTorr, so that the primary ions collide with the collision gas molecules multiple times, the collision energy is controlled to be in the range of 10-100eV, and the generated product ions continuously migrate towards the outlet of the collision cell under the action of the axial potential difference.

4. The method of claim 1, wherein the method is a quadrupole collision cell ion cleaning method based on axial potential difference. In step 4, the ion signal intensity is collected in real time by an ion detector arranged at the outlet end of the collision cell, and the collected signal is compared with a preset threshold, when the signal intensity exceeds the threshold for N consecutive measurements, the input of the primary ions is stopped, N is an integer between 2 and 5, and the preset threshold is 80%-120% of the theoretical intensity of the target product ion.

5. The method of claim 1, wherein the method is a quadrupole collision cell ion cleaning method based on axial potential difference. In step 5, the cleaning process is started within 0.1-1ms after stopping the input of the primary ions, the amplitude of the quadrupole radio frequency voltage is kept unchanged at 100-1000V and the frequency is kept unchanged at 0.5-3MHz during the cleaning process, and the axial potential difference between the inlet and outlet of the collision cell is kept constant, and the cleaning duration T is 5-50ms.

6. The method of claim 1, wherein the method is performed in a quadrupole collision cell ion cleaning method based on axial potential difference. In step 6, the ion detector arranged at the outlet end of the collision cell is used to continuously monitor the ion abundance at a sampling frequency of 1-10kHz, and the moving average of the ion abundance is calculated once every 0.1-1ms; when M consecutive moving averages are all lower than 110% of the initial background noise level obtained by blank measurement before cleaning, it is determined that the cleaning process is completed, and M is an integer between 5 and 10.

7. The method of claim 1, wherein the method is performed in a quadrupole collision cell ion cleaning method based on axial potential difference. In step 7, after confirming that the cleaning process is completed, the system performs the following preparation operations: resetting the counter of the ion detector to zero; resetting the preset threshold for product ion collection; restoring the primary ion transmission channel to standby state; And according to the preset analysis sequence to determine whether the need to analyze the next target ion, if the need to analyze the new target ion, the quadrupole mass analyzer working parameters adjusted to the corresponding new target ion mass-to-charge ratio set value, complete the parameter adjustment after the ready signal, allowing the next batch of primary ions into the collision pool.

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