Method for widening injection mass range of linear ion trap / time-of-flight mass spectrometry

Abstract

The invention discloses a method for widening the injection mass range of a linear ion trap / time-of-flight mass spectrometry, and the method comprises the steps: firstly, a linear ion trap / time-of-flight mass spectrometer is disclosed, and the external ion injection mass range of the linear ion trap / time-of-flight mass spectrometry is widened through a segmented multistage rod, bias voltage and step trapping voltage strategy; when external ions are injected, due to the movement speed difference of light and heavy ions, only ions in a certain mass range can reach a mass spectrum detector, the analysis performance of a linear ion trap / time-of-flight mass spectrum is seriously limited by the limited mass range, and the mass spectrum can be accurately detected through a segmented multistage rod, bias voltage and step trapping voltage strategy. And the mass range of the external ion implantation linear ion trap / time-of-flight mass spectrum can be widened.

Description

Technical Field

[0001] The invention belongs to a mass spectrometry instrument, and in particular relates to a method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer. Background Art

[0002] Ion storage technology refers to storing ions outside the mass analyzer and then injecting ions immediately after the previous data acquisition / processing cycle is completed. In theory, the duty cycle of the continuous ion source can be increased to 100%. Among them, the ion trap with ion storage function is the first choice for the pre-stage storage device of time-of-flight mass spectrometry (TOFMS). Therefore, the ion trap time-of-flight tandem mass spectrometry (QIT / TOFMS) has been greatly developed. Compared with the point distribution state of the three-dimensional ion trap, the two-dimensional linear ion trap (LIT) has higher injection efficiency and higher ion storage capacity, and LIT / TOFMS has been greatly developed. However, when external ions are injected, due to the difference in migration speed of light and heavy ions, only ions within a certain mass range can reach the TOF pulse repulsion zone. The mass window problem of LIT / TOF seriously limits its application prospects.

[0003] According to the serial mode, LIT / TOF can be divided into two categories. One type of LIT is only used as a pre-stage storage device, which cuts off the original continuous ion flow, modulates the ion flow into an ion group synchronized with TOFMS, and extracts it to the TOFMS acceleration area to complete mass analysis, which is called "orthogonal coupling LIT / TOFMS"; the other type uses LIT as the delayed acceleration area of ​​TOFMS, which is called "axial coupling LIT / TOFMS". Axially coupled LIT / TOFMS uses ion traps as the repulsion acceleration area of ​​TOFMS, which has many advantages over radial coupling. However, in axially coupled LIT / TOFMS, LIT acts as an ion injection trap and pulse delay area, which not only affects the external ion injection mass range, but also affects the TOFMS resolution. In order to achieve high resolution, the LIT length must be short enough to ensure high extraction electric field strength and uniformity, but it will limit the ion injection mass range. It is crucial to improve the injection mass window of axially coupled LIT / TOFMS without affecting the resolution. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention discloses a method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer, wherein the linear ion trap / time-of-flight mass spectrometer comprises an external ion source, a segmented multipole rod, a linear ion trap, and a time-of-flight mass spectrometer coaxially arranged in sequence, wherein the segmented multipole rod comprises an entrance electrode, a segmented radio frequency electrode, an exit electrode, and a grid, wherein the segmented radio frequency electrode comprises a plurality of sub-electrode groups arranged in sequence, wherein a first group of electrodes of the segmented radio frequency electrode and a secondary end electrode group are divided by a resistor chain to form a uniform axial direct current electric field, the linear ion trap comprises a front cover electrode, a radio frequency electrode, and a rear cover electrode, wherein the radio frequency electrode applies a radio frequency voltage and a direct current bias voltage, and the front cover electrode and the rear cover electrode apply a direct current voltage, and the voltages of the exit electrode, the front cover electrode, the radio frequency electrode, and the rear cover electrode are sequentially controlled to regulate the pre-enrichment, injection, capture, cooling, and extraction processes of ions within a wide mass range, specifically including the following methods:

[0005] Pre-enrichment period: ions generated by the external ion source enter the segmented multi-pole rod under the action of the axial DC electric field. The DC voltage of the last group of segmented RF electrodes is set to zero potential, and the exit electrode is set to a high level to block ions, so that the ions are pre-enriched at the end of the segmented multi-pole rod. The ion injection path is shortened by tuning the electrode length and the exit electrode voltage to improve the quality window.

[0006] Injection period: reduce the exit electrode voltage, front cover electrode voltage and RF electrode bias voltage to form an axial injection electric field, while raising the rear cover electrode to block ions, and improve the mass window by tuning the RF electrode bias voltage;

[0007] Capture period: After the injection period, the ions reach a certain position in the linear ion trap, the RF electrode bias voltage is reduced to zero, and the front cover electrode voltage and the rear cover electrode voltage are increased to the same high trapping potential, increasing the axial potential barrier to axially trap the ions, and improving the mass window by tuning the trapping potential;

[0008] Cooling period: After the capture period, the voltage of the front cover electrode and the rear cover electrode are immediately reduced to a low trapping potential to reduce the electric field penetration effect and ensure radial capture stability;

[0009] Extraction phase: After the ions are sufficiently cooled in the linear ion trap, the driving RF voltage of the RF electrode is turned off, and a double pulse voltage is applied to the front cover electrode voltage and the rear cover electrode at the same time to extract the ions from the linear ion trap to the time-of-flight mass analyzer.

[0010] Furthermore, the segmented multi-stage rod is used for pre-enrichment of ions.

[0011] Furthermore, the linear ion trap serves as a cooling device and a time-of-flight mass spectrometer delay zone.

[0012] Furthermore, the gas pressure in the ion trap ranges from 0.1 to 100 Pa.

[0013] Furthermore, the pre-enrichment period has a time range of 0.5-20 ms, the injection period has a time range of 0.5-100 μs, the capture period has a time range of 0-50 μs, the cooling period has a time range of 0.5-20 ms, and the extraction period has a time range of 5-50 μs.

[0014] Furthermore, the length of the linear ion trap is in the range of 2-10 mm, the length of the last group of segmented electrodes of the segmented multipolar rod is in the range of 2-10 mm, and the distance between the segmented multipolar rod and the linear ion trap is in the range of 0.5-10 mm.

[0015] Furthermore, during the pre-enrichment period, the potential of the outlet electrode is higher than the zero potential, with an amplitude range of 1-100V; during the injection period, the bias potentials of the outlet electrode, the front cover electrode and the RF electrode are lower than the zero potential, forming an axial potential gradient in sequence, with an amplitude range of 0-100V, and the potential of the rear cover electrode is higher than the zero potential, with an amplitude range of 0-100V; during the capture period, the high trapping potentials of the front cover and the rear cover electrodes are higher than the zero potential, with an amplitude range of 1-200V; during the cooling period, the low trapping potentials of the front cover and the rear cover electrodes are higher than the zero potential, with an amplitude range of 1-100V.

[0016] Furthermore, the grid is closely attached to the outlet electrode to shield the electric field of the front end cover electrode.

[0017] Furthermore, the external ion source includes various types of ion sources at normal pressure and negative pressure.

[0018] Furthermore, the linear ion trap ion extraction method is axial extraction.

[0019] Due to the adoption of the above technical scheme, the present invention provides a method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer. First, an axially coupled linear ion trap / time-of-flight mass spectrometer is provided. The external ion injection mass range of the linear ion trap / time-of-flight mass spectrometer is broadened by means of a segmented multi-pole rod, a bias voltage and a step-trapping voltage strategy. When external ions are injected, due to the difference in movement speeds of light and heavy ions, only ions within a certain mass range can reach the mass spectrometer detector. The limited mass range severely limits the analytical performance of the linear ion trap / time-of-flight mass spectrometer. The mass range of the external ion injection linear ion trap / time-of-flight mass spectrometer can be broadened by means of a segmented multi-pole rod, a bias voltage and a step-trapping voltage strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 Schematic diagram of the axially coupled LIT / TOFMS structure.

[0022] Figure 2 (a) is the working timing diagram of LIT / TOFMS; (b) is the axial potential distribution diagram of the pre-enrichment, injection, capture and cooling stages.

[0023] Figure 3 SIMION simulation model diagram of the first-level well: (a) is a 16.8mm end segmented short rod; (b) is a 4mm end segmented short rod; (c) is the central axis potential diagram in the cooling stage.

[0024] Figure 4 In the inter-well extraction stage, under the bias voltage setting of 0V and -10V, (a) the potential distribution diagram of the central axis; (b) the axial motion trajectory diagram of the same m / z200 ion.

[0025] Figure 5 (a) The injection efficiency of m / z 50, 75, and 100 ions when the injection time is 4μs and the bias voltage is 0V and -10V; (b) The injection efficiency of m / z 150, 175, and 200 ions when the injection time is 9μs and the bias voltage is 0V and -10V.

[0026] Figure 6 During the inter-trap extraction and cooling stages, under bias voltages of 0 V and -10 V, (a) the axial motion trajectory of m / z 1000 ions with different kinetic energies under the non-step trapping potential; (b) the potential distribution of the central axis under trapping potentials of 15 V and 30 V; (c) the axial motion trajectory of high kinetic energy m / z 1000 ions under the step trapping potential strategy.

[0027] Figure 7 (a) is the injection efficiency of m / z 250, 300, and 350 ions with an injection time of 4 μs and with / without step trapping potential; (b) is the injection efficiency of m / z 1200, 1300, 1400, and 1500 ions with an injection time of 9 μs and with / without step trapping potential.

[0028] Figure 8The ion injection efficiency changes with m / z under the conditions of segmented multi-stage rod, bias voltage and step trapping voltage strategy: (a) is the injection time of 4μs, and (b) is the injection time of 9μs.

[0029] Fig. 9 (a) is the variation of ion intensities of m / z 78, 106, 166 and 260 with extraction time between double wells under the conditions of with / without segmented multi-stage rod, bias voltage and step trapping voltage strategy; (b) is the mass spectrum when the relative intensity of m / z 106 is 1. DETAILED DESCRIPTION

[0030] In order to make the technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention:

[0031] The present invention discloses a method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer. The external ion injection mass range affects the analytical performance of the linear ion trap / time-of-flight mass spectrometer. The external ion injection mass range of the linear ion trap / time-of-flight mass spectrometer can be broadened by using a segmented multipolar rod, a bias voltage and a step-trapping voltage strategy.

[0032] like Figure 1 As shown, in the example, the segmented multipole (LIT-1) is a segmented linear quadrupole structure, the injection ion trap (LIT-2) is a quadrupole structure, and the mass analyzer is a reflection time-of-flight mass analyzer (TOFMS), and the three are placed coaxially. The segmented multipole is used for ion pre-enrichment and consists of an entrance electrode, a segmented electrode, and an exit electrode (IG1). The segmented electrodes are respectively composed of four parallel electrode arrays (E1-E12); each electrode array is composed of concentric cylindrical electrodes evenly spaced. A DC voltage is applied to the entrance electrode and the exit electrode. Except for the last group of electrodes (E12), the concentric cylindrical electrodes of the segmented electrode are evenly divided by a voltage divider resistor to form an axial potential field to shorten the external ion injection path; each cylindrical electrode is connected to a 1nF capacitor for applying a periodic radio frequency voltage. The injection ion trap is used as a secondary storage trap and TOF pulse delay zone, and consists of a front cover electrode (IG2), a radio frequency electrode, and a rear cover electrode (IG3). A DC voltage is applied to the front cover electrode and the rear cover electrode. The RF electrode applies RF voltage and adds a DC bias voltage Q dc LIT-2 is not only a secondary storage well, but also a TOF pulse delay zone. In order to ensure the resolution of TOFMS, the length of LIT-2 cannot be too long to ensure the intensity and uniformity of the pulse extraction electric field and improve the TOFMS resolution. The length of LIT-2 is 8mm.

[0033] Working sequence Figure 2As shown in a, after the analyte is ionized by an external ionization source, a continuous or pulsed ion flow is obtained, which is carried to LIT-1 by the carrier gas. There is a uniform axial electric field between E1 and E11. The voltage of the last segmented electrode (E12) is set to 0V, and the voltage of IG1 is raised to a high potential to trap ions in LIT-1, so as to achieve pre-cooling and pre-enrichment of the ion beam and regulate the ion injection path at the same time. Subsequently, the voltages of IG1 and IG2 are lowered and the voltage of IG3 is raised to complete the ion injection from LIT-1 to LIT-2. The voltages of IG1, IG2 and IG3 are raised to restore LIT-1 to the pre-enrichment state, and LIT-2 enters the capture and cooling stage. After the ion beam is fully cooled in LIT-2, positive and negative double pulse high voltages are applied to IG1 and IG2, respectively, to extract ions from LIT-2 to TOFMS. Figure 2 As shown in b, in the pre-enrichment stage, the LIT-1 ion enrichment site is z 0 ; When going from the pre-enrichment stage to the injection stage, the ions change from z 0 It starts to move and reaches a certain position z in LIT-2. The extraction distance is divided into two parts s1 and s2 by Gate2. The ion m / ze first accelerates to move in a straight line, and the movement path is s1, and then decelerates to move in a straight line, and the movement path is s2. Regardless of the initial kinetic energy of the ion, the farthest axial position of the ion is z 0 Isopotential point z max , the maximum displacement is s2 max The injection phase is set to time T set For the widest mass window, the smallest mass-to-charge ratio ion (m / ze) min Return to IG2, ion with the highest mass-to-charge ratio (m / ze) max Just reached IG2, ratio (m / ze) max / (m / ze) min As shown below, by shortening path s1 and lengthening path s2, (m / ze) can be increased. max / (m / ze) min Among them, s1 and s2 depend on the structural design and voltage tuning strategy.

[0034]

[0035] Segmented multistage rods shorten the ion injection path: ion pre-enrichment site z in LIT 0 The position of z depends on the length of the LIT-1 end segment rod (E12), the voltage of the second end segment rod (E11) and the ion gate (IG1) voltage. By shortening the length of E12, the z 0 Close to the end of the first-stage ion trap. Figure 2 As shown, Figure 2 In a, the length of E12 is 16.8 mm, and when the voltage of the secondary terminal electrode is 20 V, the path s1 is 9.4 mm. Figure 2 In b, the length of E12 is 4 mm, and the voltage of the secondary end electrode is set to 20 V, which can effectively move the cooling point z 0 , shorten the extraction path s1 to 3mm.

[0036] Bias voltage expands the low m / z range: Low mass ions are easily affected by the electric field. During the injection phase, when the DC component of the RF voltage on the RF electrode is 0V, the injection depth s2 is insufficient due to the reverse electric field obstruction, and the transmission efficiency of low m / z ions is limited. Figure 3 As shown in a, during the injection phase, a bias voltage Q is applied to the LIT-2 RF electrode. dc = -10V, the axial injection depth s2 of the ions increases, which is beneficial to the expansion of the low-mass range. Figure 3 As shown in Figure b, the motion trajectory of an ion with m / z 200 is simulated and recorded under the bias potential of 0V and -10V. dc = -10V, ion injection path s2 max The increase of ~3.4 mm enables efficient extraction of ions with m / z 200. Using SIMION simulation, the injection efficiency of ions in the low and high m / z ranges was investigated under injection times of 4 μs and 9 μs, respectively. Figure 4 As shown in the figure, when the bias voltage is set to -10 V during inter-trap ion transmission, the injection efficiency of m / z 50, 75 and 100 in the low mass range increases from 3.5%, 28% and 58.5% to 11.5%, 64.5% and 78%, respectively. In the high mass range, the injection efficiency of m / z 150, 175 and 200 increases from 9.5%, 16.5% and 18% to 26%, 81.5% and 91.5%, respectively.

[0037] Stepped trapping voltage increases the high m / z range: When the injection period ends, the ion reaches a certain position z in LIT-2, and when the potential difference between its position z and IG3 is greater than its kinetic energy E k , can achieve capture, otherwise the ion overshoots IG3 and is lost. And the higher the m / z, the greater the inertia, the easier it is to overshoot and lose. In order to improve the injection efficiency of high kinetic energy ions, it is necessary to increase the voltage of IG2 and IG3 during the capture period to increase the axial potential well depth and improve the ion capture efficiency. Take two m / z 1000 ions with different energies as an example. At the end of the injection period, the two ions reach z = 56.9 mm, where the axial potential barrier is 5.74 eV and the ion kinetic energy E k are 4.1eV and 7.2eV respectively. Figure 5As shown in a, low energy ions 4.1eV < 5.74eV are captured; high energy ions 7.2eV > 5.74eV are lost due to ion overshoot. If high energy m / z 1000 ions are to be captured, a high axial potential well depth is required, i.e., increasing the voltages of IG2 and IG3. Figure 5 As shown in Figure b, by increasing the IG2 and IG3 voltages to 30V, the axial potential barrier increases to 11.5eV, which is higher than the kinetic energy 7.2eV, and can effectively prevent ion overshoot and achieve ion axial capture. However, when the IG2 and IG3 voltages are high, the electric field penetration effect will change the quadrupole field, and radial stable capture cannot be achieved. Therefore, after achieving axial capture at a high voltage of 30V, it is necessary to immediately reduce the IG2 and IG3 voltages to 15V to ensure radial stable trapping. Figure 5 As shown, 7.2eV high-energy ions were successfully implanted into LIT-2 through a step-trapping voltage strategy.

[0038] Using SIMION simulation, the transmission efficiency of ions in the low and high m / z ranges was investigated under injection times of 4μs and 9μs, respectively. Figure 6 As shown in the figure, by using the step-trapping voltage strategy, in the low m / z range, the transmission efficiency of m / z 250, 300 and 350 increased from 36%, 9% and 0.5% to 93%, 65.5% and 25.5%, respectively. In the high mass range, the transmission efficiency of m / z 1200, 1300, 1400 and 1500 increased from 56.5%, 28%, 7.5% and 7.5% to 99.5%, 94.5%, 91% and 72%, respectively.

[0039] Mass range simulation results: Three strategies, namely, pre-stage segmented injection well, bias voltage and step-trapping voltage, are used to investigate the mass window of the cascade structure. Figure 7 As shown, in the high m / z range, an injection efficiency of ∼100% was achieved in the range of m / z 200 to 1400. In the low m / z range, an injection efficiency of >60% was achieved in the range of m / z 75 to 300.

[0040] Mass range experimental results: The injection mass range was investigated using 10ppbv acetone, benzene, p-xylene, tetrachloroethylene and 1,3-hexachlorobutadiene / nitrogen standard gases. With / without the pre-stage segmented injection well, bias voltage and step-priority voltage conditions, such as Figure 8 and Fig. 9 As shown, when the relative intensity of the m / z 106 ion signal is 100%, the old system cannot detect the m / z 260 ion. Under the new system, the relative signal intensity of m / z 260 reaches 0.25, and the relative signal intensity of m / z 166 is enhanced to 1.0.

[0041] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer, characterized in that: The linear ion trap / time-of-flight mass spectrometer comprises an external ion source, a segmented multipole, a linear ion trap, and a time-of-flight mass spectrometer which are coaxially arranged in sequence, wherein the segmented multipole comprises an entrance electrode (1), a segmented radio frequency electrode (2), an exit electrode (4), and a grid (5), wherein the segmented radio frequency electrode (2) comprises a plurality of sub-electrode groups arranged in sequence, wherein a first group of electrodes and a secondary end electrode group of the segmented radio frequency electrode (2) are divided by a resistor chain to form a uniform axial direct current electric field, and the linear ion trap comprises a front cover electrode (6), a radio frequency electrode (7), and a rear cover electrode (8), wherein the radio frequency electrode (7) applies a radio frequency voltage and a direct current bias voltage, and the front cover electrode (6) and the rear cover electrode (8) apply a direct current voltage, and the voltages of the exit electrode (4), the front cover electrode (6), the radio frequency electrode (7), and the rear cover electrode (8) are sequentially controlled to regulate the pre-enrichment, injection, capture, cooling, and extraction processes of ions within a wide mass range, specifically including the following methods: Pre-enrichment period: ions generated by the external ion source enter the segmented multi-pole rod under the action of the axial DC electric field, the DC voltage of the last group of segmented electrodes (3) of the segmented radio frequency electrode (2) is set to zero potential, and the exit electrode (4) is set to a high level to block ions, so that the ions are pre-enriched at the end of the segmented multi-pole rod. By tuning the length of the electrode (3) and the voltage of the exit electrode (4), the ion injection path is shortened and the mass window is improved; Injection period: lower the voltage of the outlet electrode (4), the voltage of the front cover electrode (6) and the bias voltage of the radio frequency electrode (7) to form an axial injection electric field, and at the same time raise the rear cover electrode (8) to block ions, and improve the mass window by tuning the bias voltage of the radio frequency electrode (7); Capture period: After the injection period, the ions reach a certain position in the linear ion trap, the bias voltage of the radio frequency electrode (7) is reduced to zero, and at the same time, the voltage of the front cover electrode (6) and the rear cover electrode (8) are increased to the same high trapping potential, increasing the axial potential barrier to axially trap the ions, and improving the mass window by tuning the trapping potential; Cooling period: After the capture period, the voltage of the front cover electrode (6) and the rear cover electrode (8) are immediately reduced to a low trapping potential to reduce the electric field penetration effect and ensure radial capture stability; Extraction phase: After the ions are sufficiently cooled in the linear ion trap, the driving RF voltage of the RF electrode (7) is turned off, and a double pulse voltage is applied to the front cover electrode (6) and the rear cover electrode (8) at the same time, to extract the ions from the linear ion trap to the time-of-flight mass analyzer.

2. A method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer according to claim 1, characterized in that: The segmented multi-stage rod is used for pre-enrichment of ions.

3. The method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer according to claim 1, characterized in that: The linear ion trap serves as a cooling device and a time-of-flight mass spectrometer delay zone.

4. The method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer according to claim 1, characterized in that: The gas pressure in the ion trap ranges from 0.1 to 100 Pa.

5. The method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer according to claim 1, characterized in that: The pre-enrichment period has a time range of 0.5-20 ms, the injection period has a time range of 0.5-100 μs, the capture period has a time range of 0-50 μs, the cooling period has a time range of 0.5-20 ms, and the extraction period has a time range of 5-50 μs.

6. The method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer according to claim 1, characterized in that: The length of the linear ion trap is in the range of 2-10 mm, the length of the last group of segmented electrodes of the segmented multipolar rod is in the range of 2-10 mm, and the distance between the segmented multipolar rod and the linear ion trap is in the range of 0.5-10 mm.

7. The method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer according to claim 1, characterized in that: During the pre-enrichment period, the potential of the outlet electrode is higher than the zero potential, with an amplitude range of 1-100V; during the injection period, the bias potentials of the outlet electrode, the front cover electrode and the RF electrode are lower than the zero potential, forming an axial potential gradient in turn, with an amplitude range of 0-100V, and the rear cover electrode potential is higher than the zero potential, with an amplitude range of 0-100V; during the capture period, the high trapped potentials of the front cover and rear cover electrodes are higher than the zero potential, with an amplitude range of 1-200V; During the cooling period, the low trapped potential of the front and rear cap electrodes is higher than the zero potential, with an amplitude ranging from 1 to 100V.

8. The method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer according to claim 1, characterized in that: The grid is close to the exit electrode and is used to shield the electric field of the front cover electrode.

9. The method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer according to claim 1, characterized in that: External ion sources include various types of ion sources at normal pressure and negative pressure.

10. The method for broadening the injection mass range of a linear ion trap / time-of-flight mass spectrometer according to claim 1, characterized in that: The ion extraction method of the linear ion trap is axial extraction.

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