Ion funnel trap control method

Abstract

The invention discloses a brand-new ion funnel trap control method, which comprises the following steps: in an injection enrichment stage, applying a low-intensity direct-current electric field in a storage region, uniformly distributing ions entering the storage region along the axis of the storage region, hovering and enriching, and improving the ion injection capacity; in the shaping storage stage, a medium-intensity direct-current electric field is applied to the storage area, ions are compressed to the position near an outlet end grid mesh, and the ion number density is improved; in the pulse release stage, a high-strength direct-current electric field is applied to the storage area, and the ions rapidly leave the storage area and enter the ion mobility spectrometry or the mass spectrometry for separation and detection. The control of the internal electric field of the ion funnel trap can be realized through two potential modulation modes: 1, periodically changing potentials are applied to grid meshes at two axial ends of a storage region of the ion funnel trap, so that the electric field in the storage region is periodically changed; the direct-current electric field intensity of the storage area is directly changed by periodically changing the potential difference between the two ends of the resistance chain corresponding to the annular electrode of the storage area.

Description

Technical Field

[0001] The present invention relates to a control method for an ion funnel trap, and more particularly to a method for improving the signal intensity of a mobility spectrum by changing the electric field in the storage area of the ion funnel trap. Background Art

[0002] An ion funnel trap (IFT) is an hourglass-shaped electrokinetic ion funnel operating at a pressure of hundreds of pascals. It is usually located between the ion source and the migration region or mass analyzer of a low-pressure ion mobility spectrometer or mass spectrometer, and plays the roles of ion transmission, storage, and pulsed injection. The storage area with a relatively large inner diameter of the IFT can effectively accumulate ions between pulses. By means of ion gating injection technology, a pulsed ion packet is formed and then enters the migration region for mobility separation under the action of an electric field and a support gas, or enters the mass analyzer for detection. The release efficiency of the IFT directly determines the signal intensity and detection sensitivity.

[0003] The IFT was proposed in 2007 and is currently mainly used in the mobility mass spectrometers of Agilent Technologies. The IFT is composed of metal electrodes with different inner diameters and insulating gaskets stacked alternately. Each electrode is divided by a series resistance chain, and different voltage differences are applied in different regions to achieve the optimal ion transmission efficiency. 180° out-of-phase radio frequency potentials are alternately applied to each electrode, and the formed radio frequency electric field can confine ions radially and reduce diffusion loss. The middle region of the IFT is the ion storage area. There is a grid G1 in front of the storage area, and grids G2 and G3 are arranged in sequence behind the storage area.

[0004] In the conventional working mode of the IFT, in one working cycle, during the injection stage, the corresponding position voltage is applied to G1, and higher voltages than the corresponding position voltage are applied to G2 and G3. Ions move to the storage area and accumulate under the action of the DC electric field; during the storage stage, higher voltages than the corresponding position voltage are applied to G1, G2, and G3. Ions transmitted from the previous stage are blocked by the reverse electric field formed by the high potential of G1, and the ions in the storage area will be confined in this area under the action of the radio frequency electric field; during the release stage, the voltage of G1 is the same as that in the storage stage, and the corresponding position voltage is applied to G2 and G3. Ions leave the storage area under the drive of the electric field.

[0005] The ion release efficiency of IFT is directly related to the distribution of ion clusters in the storage area before release and the electric field in the storage area during the release stage. To accumulate more ions in the storage area of IFT, the electric field strength in this area is usually low. Therefore, during the release stage, if only the DC electric field in the storage area itself is relied on to drive the ions, fewer ions can be released, and ions with a smaller mobility have a lower release efficiency due to their slow movement speed, resulting in serious mobility discrimination. Ibrahim et al. (Anal. Chem., 2007, 79: 7845-7852) applied a potential higher than the position potential to G1 during the release stage to drive the release of ions. This ion gate control method has limited signal enhancement effect for signals with a narrow release time (<40 μs), and the release efficiency of ions with a small mobility is also poor. To improve the release efficiency of IFT for ions with a small mobility, Ibrahim et al. (Anal. Chem, 2014, 86: 5295-5299) used helium instead of nitrogen as the drift gas, which increased the signal intensity by 10 times. The essential reason is that the mobility of ions in helium is greater, so ions can be released faster and more efficiently. Gabelica et al. (J. Am. Soc. Mass Spectrom., 2018, 29: 2189-2198) reported exploring better conditions for performing collision-induced experiments on 10 kDa complexes by increasing the electric field strength in the storage area of the ion funnel trap, adjusting the ion gate closing voltage, and optimizing the RF amplitude to reduce ion fragmentation.

[0006] Currently, there is still a problem with the ion funnel trap that the ion release rate is low under a narrow release time, especially the release rate of ions with a small mobility is low, resulting in a low signal intensity. Summary of the Invention

[0007] To solve the problem that the release efficiency of the ion funnel trap is low under a narrow opening time, resulting in a low signal intensity, the present invention discloses a control method for an ion funnel trap. By periodically changing the grid voltage of the ion funnel trap or periodically changing the potential difference between the two ends of the resistor chain corresponding to the ring electrode in the storage area, the electric field in the storage area of the ion funnel trap changes periodically, so as to realize the injection enrichment, storage shaping, and pulsed release of ions.

[0008] The technical solution adopted by the present invention to achieve the above object is:

[0009] An ion funnel trap control method, wherein the ion funnel trap is composed of ninety-six annular metal electrodes with an inner diameter varying in a hourglass shape, stacked coaxially and at equal intervals; along the axial direction from left to right, an ion introduction region is formed between the first electrode and the sixty-third electrode of the ion funnel trap, an ion storage region is formed between the sixty-fourth electrode and the seventy-fifth electrode, and an ion extraction region is formed between the seventy-sixth electrode and the ninety-sixth electrode; wherein, metal grids permeable to ions are provided inside the sixty-fourth electrode, the seventy-fifth electrode, and the seventy-sixth electrode. Except for the sixty-fourth electrode, the seventy-fifth electrode, and the seventy-sixth electrode, the first electrode to the ninety-sixth electrode of the ion funnel trap are electrically connected to a power supply through a voltage dividing resistor chain, and direct current electric fields in the same direction as the ion migration direction are respectively formed in the ion introduction region, the ion storage region, and the ion extraction region of the ion funnel trap;

[0010] During the working cycle of the ion funnel trap, the electric field strengths in the ion introduction region and the ion extraction region are respectively maintained at E 1 and E 3 unchanged, and the electric potential at the corresponding resistor chain positions of the sixty-fourth electrode, the seventy-fifth electrode, and the seventy-sixth electrode are respectively V G1 、V G2 and V G3 , wherein, V G1 >V G2 >V G3 ;

[0011] During the working cycle of the ion funnel trap, control the electric field strength in the ion storage region to increase with time. At the timing moment t 0 ≤t<t 1 , due to the relatively low electric field strength in the ion storage region, ions pass through the sixty-fourth electrode from the ion introduction region and enter the ion storage region, and hover and enrich along the axis of the ion funnel trap. This stage is regarded as the injection and enrichment stage;

[0012] At the timing moment t 1 ≤t<t 2 , due to the medium electric field strength in the ion storage region, the electric field drives the ions to move towards the seventy-fifth electrode, and the ion number density in front of the seventy-fifth electrode increases. This stage is regarded as the storage and shaping stage;

[0013] At the timing moment t 2 ≤t<t 3 , due to the relatively high electric field strength in the ion storage region, the ions are accelerated by the high electric field in the ion storage region, pass through the seventy-fifth electrode and the seventy-sixth electrode, and enter the ion extraction region, and are further transmitted to a migration spectrum or a mass spectrum for separation and detection. This stage is regarded as the pulse release stage.

[0014] The periodic change of the electric field in the ion storage region is achieved by modulating the electric potential of the sixty-fourth electrode. Specifically:

[0015] At timing moment t 0 ≤t < t 1 , the electric field strength formed by the potential difference across the corresponding resistor chain in the ion storage region is E 2 , the 64th electrode applies the corresponding position potential V G1 , the 75th electrode and the 76th electrode respectively apply potentials V G2 and V G3 higher than the corresponding position potential V 2 and V 3 , V 3 > V 2 > V G2 > V G3 ;

[0016] At timing moment t 1 ≤t < t 2 , the electric field strength formed by the potential difference across the corresponding resistor chain in the ion storage region is E 2 , the 64th electrode applies a potential V higher than the corresponding position potential 11 , V 11 > V G1 , the 75th electrode and the 76th electrode respectively apply potentials V 2 and V 3 ;

[0017] At timing moment t 2 ≤t < t 3 , the electric field strength E formed by the potential difference across the corresponding resistor chain in the ion storage region 2 , the 64th electrode applies a higher voltage V 12 , V 12 > V 11 , the 75th electrode and the 76th electrode respectively apply the corresponding position potentials V G2 and V G3 .

[0018] The periodic change of the electric field in the ion storage region is achieved by modulating the electric field strength formed by the potential difference across the corresponding resistor chain in the ion storage region, specifically:

[0019] At timing moment t 0 ≤t < t 1 , the electric field strength formed by the potential difference across the corresponding resistor chain in the ion storage region is E 2 , the 64th electrode applies the corresponding position potential V G1 , the 75th electrode and the 76th electrode respectively apply potentials V G2 and V G3 higher than the corresponding position potentials V 2 and V 3, V 3 > V 2 > V G2 > V G3 ;

[0020] At timing moment t 1 ≤ t < t 2 , the electric field strength formed by the potential difference across the corresponding resistor chain in the ion storage region is E 2 , the sixty - fourth electrode applies a potential V higher than the potential at the corresponding position 11 , V 11 > V G1 , the seventy - fifth electrode and the seventy - sixth electrode respectively apply potentials V 2 and V 3 ;

[0021] At timing moment t 2 ≤ t < t 3 , the electric field strength formed by the potential difference across the corresponding resistor chain in the ion storage region is E 2 ', E 2 '> E 2 , the sixty - fourth electrode applies potential V 11 , the seventy - fifth electrode and the seventy - sixth electrode respectively apply the corresponding position potentials V G2 and V G3 .

[0022] Timing moment t 3 and t 0 The difference is the ion gate working period T, which is 30 - 100 ms. The difference between timing moment t 1 and t 0 is defined as the injection time. The difference between timing moment t 2 and t 1 is defined as the storage time, which is 0 - 1000 μs. The difference between timing moment t 3 and t 2 is defined as the release time, which is 10 - 100 μs.

[0023] When the ion funnel trap works, the potentials applied by the sixty - fourth electrode, the seventy - fifth electrode and the seventy - sixth electrode or the electric field strength formed by the potential difference across the corresponding resistor chain in the ion storage region are cyclically adjusted periodically according to the time sequence.

[0024] The present invention has the following beneficial effects and advantages:

[0025] 1. The present invention realizes the injection enrichment, storage shaping and efficient release of ions by periodically changing the electric field in the storage area. During the injection stage, the electric field strength in the storage area is relatively low, which is conducive to the enrichment of ions. During the storage stage, the electric field in the storage area is increased by raising the grid potential at the inlet end of the storage area, and the ion cluster is compressed towards the grid at the outlet end. During the release stage, the electric field in the storage area is further increased by raising the grid potential at the inlet end or increasing the DC electric field strength in the storage area, accelerating the ion movement speed, thereby improving the ion release efficiency of the ion funnel trap.

[0026] 2. The present invention improves the ion number density in front of the grid at the outlet end before release and the electric field strength in the storage area during release, thereby increasing the percentage of ions entering the subsequent stage from the storage area during the release stage, and improving the release effect of ions with different mobilities, thus enhancing the signal intensity and detection sensitivity of the ion mobility spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the ion funnel trap structure adopting the control method disclosed in the present invention.

[0028] Figure 2 Schematic diagram of the voltages of each electrode of the ion funnel trap at different stages in the conventional working mode.

[0029] Figure 3 Schematic diagram of the voltages of each electrode of the ion funnel trap at different stages in the working mode of periodically changing the electric field in the storage area by modulating the grid potential disclosed in the present invention.

[0030] Figure 4 Schematic diagram of the voltages of each electrode of the ion funnel trap at different stages in the working mode of periodically changing the electric field in the storage area by modulating the potential difference across the corresponding resistor chain in the storage area disclosed in the present invention.

[0031] Figure 5 Schematic diagram of the ion distribution in the storage area after storing (a) 0 μs, (b) 100 μs, (c) 200 μs when the closing voltage of the 64th electrode is 15 V during the storage stage in the SIMION simulation.

[0032] Figure 6 Schematic diagram of the relationship between the number of released ions and the storage time when the closing voltage of the 64th electrode is 15 V during the storage stage in the SIMION simulation.

[0033] Figure 7 Schematic diagram of the relationship between the number of released ions and the electric field strength in the storage area during the release stage in the SIMION simulation.

[0034] Figure 8 Ion mobility spectrum diagram when acetone-assisted photoionization of triethyl phosphate is carried out, the release time is 30 μs, and the storage time ranges from 0 to 400 μs.

[0035] Figure 9 Migration spectrum of acetone-assisted photoionization of triethyl phosphate with a release time of 50 μs and a storage time ranging from 0 to 400 μs. Detailed implementation mode

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] A control method for an ion funnel trap. The ion funnel trap is formed by alternately stacking 96 circular metal electrodes with different inner diameters and ceramic gaskets. The electrode thickness is 0.5 mm and the electrode spacing is 0.5 mm. The ion funnel trap is divided into three regions: an ion introduction region is formed between the first to sixty-third circular electrodes, with the inner diameter gradually decreasing from 24 mm to 3 mm and then increasing to 20 mm; an ion storage region is formed between the sixty-fourth to seventy-fifth circular electrodes, with an inner diameter of 20 mm; an ion extraction region is formed between the seventy-sixth to ninety-sixth circular electrodes, with the inner diameter gradually decreasing from 20 mm to 3 mm. Metal grids permeable to ions are sequentially arranged inside the sixty-fourth electrode, the seventy-fifth electrode, and the seventy-sixth electrode.

[0038] Except for the electrodes where the grids are located, the remaining circular electrodes are electrically connected to the power supply through a voltage-dividing resistor chain, and a DC electric field in the same direction as the ion migration direction is formed in the ion introduction region, the ion storage region, and the ion extraction region of the ion funnel trap respectively. Among them, the corresponding position electric potentials of the sixty-fourth electrode, the seventy-fifth electrode, and the seventy-sixth electrode are V G1 , V G2 , and V G3 , V G1 >V G2 >V G3 . During the working cycle of the ion funnel trap, the DC electric field intensities in the ion introduction region and the ion extraction region of the ion funnel trap are maintained at E 1 and E 3 respectively, and the electric field in the ion storage region changes periodically by modulating the grid electric potential or the potential difference across the corresponding resistor chain in the storage region.

[0039] At the timing moment t 0 ≤t<t 1 , that is, during the injection and enrichment stage, the DC electric field intensity formed by the potential difference across the corresponding resistor chain in the storage region is E 2 , the corresponding position electric potential V G1 is applied to the sixty-fourth electrode, and higher electric potentials V G2 and V G3 are applied to the seventy-fifth electrode and the seventy-sixth electrode respectively than the corresponding position electric potentials V 2 and V 3 (V 3 >V2 >V G2 >V G3 ) The ion current transported from the ion introduction region fills the ion storage region.

[0040] At timing moment t 1 ≤t < t 2 , that is, the storage shaping stage. The DC electric field strength formed by the potential difference across the corresponding resistor chain in the storage region is E 2 , the sixty - fourth electrode applies a potential V higher than the potential at the corresponding position 11 (V 11 >V G1 ). The seventy - fifth electrode and the seventy - sixth electrode respectively apply potentials V 2 and V 3 . The ion current transported from the ion introduction region will be blocked by the reverse electric field formed by the high potential of the sixty - fourth electrode, while the ions that have entered the storage region will move towards the seventy - fifth electrode under the action of the forward electric field formed by the high potential of the sixty - fourth electrode. At the same time, due to the reverse electric field formed by the high voltages of the seventy - fifth electrode and the seventy - sixth electrode, they will not annihilate on the grid.

[0041] At timing moment t 2 ≤t < t 3 , that is, the pulse release stage. In the control method of periodically changing the electric field in the storage region by modulating the grid potential, the DC electric field strength formed by the potential difference across the corresponding resistor chain in the storage region is still E 2 , the sixty - fourth electrode applies an even higher potential V 12 (V 12 >V 11 ). The seventy - fifth electrode and the seventy - sixth electrode respectively apply the corresponding position potentials V G2 and V G3 . The ion group in the storage region will accelerate and move into the ion extraction region under the action of the forward electric field formed by the high potential of the sixty - fourth electrode; in the control method of periodically changing the electric field in the storage region by modulating the potential difference across the corresponding resistor chain in the storage region, the DC electric field strength formed by the potential difference across the corresponding resistor chain in the storage region is E 2 '(E 2 '>E 2 ). The potential of the sixty - fourth electrode is still V 11 , the seventy - fifth electrode and the seventy - sixth electrode respectively apply the corresponding position potentials V G2 and V G3 . The ion group in the storage region will accelerate and move into the ion extraction region under the action of the higher DC electric field.

[0042] Timing moment t 3 and t 0The difference is the working period T of the ion funnel trap, which is 30 to 100 ms, and the timing moment t 1 and t 0 The difference is defined as the injection time, and the timing moment t 2 and t 1 The difference is defined as the storage time, which is 0 to 1000 μs, and the timing moment t 3 and t 2 The difference is defined as the release time, which is 10 to 100 μs, and the timing moment t 3 and t 2 The difference is defined as the injection time.

[0043] When the ion funnel trap works, the electric potential applied to the grid and the DC electric field intensity formed by the potential difference across the corresponding resistor chain in the storage area are periodically and cyclically adjusted according to the said timing sequence.

[0044] The ion funnel trap adopting the working mode disclosed by the present invention is composed of Figure 1 as shown, and is formed by alternately stacking annular metal electrodes and ceramic gaskets with different inner diameters, where: 1 - 96, annular metal electrodes; 97, ion introduction area; 98, ion storage area; 99, ion extraction area, the electrode thickness is 0.5 mm, and the electrode spacing is 0.5 mm. The ion funnel trap is divided into three areas: from the first electrode to the sixty-third electrode is the ion introduction area, the area between the sixty-fourth electrode and the seventy-fifth electrode constitutes the ion storage area, and the seventy-sixth electrode to the ninety-sixth electrode is the ion extraction area. Metal grids are arranged inside the sixty-fourth electrode, the seventy-fifth electrode, and the seventy-sixth electrode.

[0045] Figure 2 shows the voltages of each electrode at different stages in the conventional working mode. During the entire working cycle, the DC electric field intensities of the ion introduction area, the ion storage area, and the ion extraction area of the ion funnel trap are respectively maintained at E 1 、E 2 and E 3 unchanged. The sixty-fourth electrode applies the corresponding position voltage during the injection stage and the same magnitude of closing voltage during the storage and release stages; the seventy-fifth electrode and the seventy-sixth electrode apply the corresponding closing voltages during the injection and storage stages and the corresponding position voltage during the release stage.

[0046] Figure 3 shows the voltages of each electrode at different stages in the working mode disclosed by the present invention, which changes the electric field in the storage area by changing the grid voltage. During the entire working cycle, the DC electric field intensities of the ion introduction area, the ion storage area, and the ion extraction area of the ion funnel trap are respectively maintained at E 1 、E 2 and E 3Remain unchanged. The sixty-fourth electrode applies the corresponding position voltage during the injection stage, and applies two different closing voltages, one low and one high, during the storage and release stages respectively. The seventy-fifth electrode and the seventy-sixth electrode apply the corresponding closing voltages during the injection and storage stages, and apply the corresponding position voltage during the release stage.

[0047] Figure 4 It shows the voltages of each electrode at different stages in the working mode of changing the electric field in the storage area by changing the DC electric field intensity in the storage area disclosed by the present invention. During the entire working cycle, the DC electric field intensities in the ion introduction area and the ion extraction area of the ion funnel trap are maintained at E 1 and E 3 remain unchanged. The DC electric field intensity in the ion storage area is maintained at E 2 during the injection and storage stages, and is increased to E 2 '(E 2 '>E 2 ) during the release stage. The sixty-fourth electrode applies the corresponding position voltage during the injection stage, and applies the same closing voltage during the storage and release stages. The seventy-fifth electrode and the seventy-sixth electrode apply the corresponding closing voltages during the injection and storage stages, and apply the corresponding position voltage during the release stage.

[0048] To illustrate the influence of the control method disclosed by the present invention on the distribution of ions in the storage area before release, an ion funnel trap model is established in the ion optical simulation software SIMION, and the periodic voltage is applied to each electrode according to Figure 3 the description. The basic parameters are the electric field intensity of 10 V / cm in the ion introduction area, the electric field intensity of 2 V / cm in the ion storage area, the electric field intensity of 20 V / cm in the ion storage area, the release voltage of the sixty-fourth electrode is 50 V, and the closing voltages of the seventy-fifth electrode and the seventy-sixth electrode are 2.5 V and 5 V respectively. Figure 5 It shows the ion distribution in the storage area of the ion funnel trap when the storage voltage of the sixty-fourth electrode is 15 V and the storage times are 0, 100, and 200 μs. As the storage time extends, the central position of the ion group gradually approaches the seventy-fifth electrode and the distribution gradually becomes narrower. Set the release time to 50 μs, and count the change of the release numbers of 1000 ions with different m / z values with the storage time ( Figure 6 ), and the release numbers of each m / z ion are all improved to a certain extent, and the improvement effect of the ion with m / z of 622 is the most significant.

[0049] Due to circuit limitations, the experiment of periodically changing the electric field in the storage area by modulating the potential difference across the corresponding resistor chain in the storage area was not carried out. However, simulations were performed in SIMION to explore the effect of increasing the DC electric field in the storage area during the release stage on the ion release efficiency. The storage time was set to 0 μs, the release time was set to 50 μs, and the electric field strength in the storage area during the injection and storage stages was 2 V / cm. The relationship between the number of ions released for each m / z and the electric field strength in the storage area during the release stage was obtained ( Figure 7 ). When the electric field strength in the storage area during the release stage was increased from 2 V / cm to 10 V / cm, the number of ions released with m / z of 80 and 322 increased by 159% and 95% respectively. The simulation results show that the control method of increasing the DC electric field in the storage area during the release stage proposed in the present invention has a theoretical and simulation basis. However, due to actual circuit condition limitations, the experiment was not carried out.

[0050] Embodiment

[0051] The voltage dividing resistor chain of the ion funnel trap is composed of the same number of voltage dividing resistors as the number of annular electrodes, which are connected in series from left to right in sequence. The two ends of the voltage dividing resistor chain and the connection points between adjacent resistors are electrical connection points. A DC isolation power supply is used to provide a potential difference of 50 V between the position of the resistor chain corresponding to the first electrode and the position of the resistor chain corresponding to the sixty-fourth electrode. A DC isolation power supply is used to provide a potential difference of 1.1 V between the position of the resistor chain corresponding to the sixty-fourth electrode and the position of the resistor chain corresponding to the seventy-fifth electrode. A DC isolation power supply is used to provide a potential difference of 50 V between the position of the resistor chain corresponding to the seventy-fifth electrode and the position of the resistor chain corresponding to the ninety-sixth electrode, forming a potential distribution that gradually decreases in the ion flow direction, so that the DC electric field strengths in the ion introduction area, ion storage area, and ion extraction area of the ion funnel trap are 7.8 V / cm, 1 V / cm, and 22.7 V / cm respectively. Taking the potential at the end of the series resistor chain of the ion funnel trap as the potential zero point, the voltage at the position corresponding to the sixty-fourth electrode is 51.1 V, the voltage at the position corresponding to the seventy-fifth electrode is 50 V, and the voltage at the position corresponding to the seventy-sixth electrode is 47.7 V.

[0052] According to Figure 3 as shown, the voltages are applied, and the specific parameters are as follows: the voltages of the sixty-fourth electrode during the injection, storage, and release stages are 51.1 V, 66.1 V, and 81.5 V respectively; the voltages of the seventy-fifth electrode during the injection, storage, and release stages are 51.6 V, 51.6 V, and 50 V respectively; the voltages of the seventy-sixth electrode during the injection, storage, and release stages are 52.5 V, 52.5 V, and 47.7 V respectively.

[0053] As an ion transport device for an ion mobility spectrometry platform, the ion funnel trap releases ion clusters. After entering the migration region, the ion clusters are separated by mobility under the action of an electric field and a support gas and then reach the electron multiplier. The weak current signal is converted into a voltage signal and amplified by a current amplifier. Then, an oscilloscope is used to collect waveform data, and after processing, an ion mobility spectrometry graph is obtained. The operating pressure of the ion funnel trap is 540 Pa, the operating temperature is 298 K, the frequency of the radio frequency voltage is 0.98 MHz, and the peak-to-peak voltage is 200 V. The operating cycle of the ion funnel trap is set to 50 ms, and the release time is 30 μs. When recording the storage time from 0 to 400 μs, the change of the migration spectrometry graph of acetone-assisted photoionization of triethyl phosphate with the storage time ( Figure 8 ), the results show that as the storage time increases from 0 to 400 μs, the reduced mobilities of 1.52, 1.42, and 1.23 cm 2 V -1 s -1 increase from 20 mV, 18 mV, and 112 mV to 124 mV, 136 mV, and 684 mV respectively, which are 6.2, 7.5, and 6.1 times the original values respectively. The operating cycle of the ion funnel trap is set to 50 ms, and the release time is 50 μs. When recording the storage time from 0 to 400 μs, the change of the migration spectrometry graph of acetone-assisted photoionization of triethyl phosphate with the storage time ( Figure 9 ), the results show that as the storage time increases from 0 to 400 μs, the reduced mobilities of 1.52, 1.42, and 1.23 cm 2 V -1 s -1 increase from 40 mV, 32 mV, and 284 mV to 168 mV, 168 mV, and 928 mV respectively, which are 4.2, 5.2, and 3.3 times the original values respectively. Obviously, using the control method disclosed in the present invention ( Figure 3 ), the signal intensity of ions with each mobility at a narrow release time (≤50 μs) can be significantly improved, and the smaller the release time, the higher the improvement multiple.

Claims

1. An ion funnel trap control method, wherein the ion funnel trap is composed of ninety-six annular metal electrodes with inner diameters changing in an hourglass shape and stacked in a coaxial and equidistant manner; along the axial direction from left to right, the ion funnel trap comprises an ion introduction region (97) between the first electrode (1) and the sixty-third electrode (63), an ion storage region (98) between the sixty-fourth electrode (64) and the seventy-fifth electrode (75), and an ion extraction region (99) between the seventy-sixth electrode (76) and the ninety-sixth electrode (96); wherein, The sixty-fourth electrode (64), the seventy-fifth electrode (75), and the seventy-sixth electrode (76) are all provided with metal grids that can penetrate ions. Except for the sixty-fourth electrode (64), the seventy-fifth electrode (75), and the seventy-sixth electrode (76), the first electrode (1) to the ninety-sixth electrode (96) of the ion funnel trap are electrically connected to the power supply through a voltage-dividing resistor chain, and a direct current electric field in the same direction as the ion migration direction is formed in the ion introduction area (97), the ion storage area (98), and the ion extraction area (99) of the ion funnel trap, respectively. The invention is characterized in that: During the working cycle of the ion funnel trap, the electric field strengths of the ion introduction region (97) and the ion extraction region (99) are maintained at E1 and E3 respectively, and the potentials of the resistor chain positions corresponding to the sixty-fourth electrode (64), the seventy-fifth electrode (75) and the seventy-sixth electrode (76) are V G1 、V G2 and V G3 , where V G1 >V G2 >V G3 ; During the working cycle of the ion funnel trap, the electric field strength of the ion storage area (98) is controlled to increase with time. At the timing time t0≤t<t1, since the electric field strength of the ion storage area (98) is relatively low, ions enter the ion storage area (98) from the ion introduction area (97) through the sixty-fourth electrode (64), and are suspended and enriched along the axis of the ion funnel trap. This stage is regarded as an injection enrichment stage. At the timing time t1≤t<t2, since the electric field strength of the ion storage area (98) is medium, the electric field drives the ions to move toward the seventy-fifth electrode (75), and the ion number density in front of the seventy-fifth electrode (75) increases, and this stage is regarded as the storage shaping stage; At the timing time t2≤t<t3, due to the high electric field strength of the ion storage area (98), the ions are accelerated under the action of the high electric field of the ion storage area (98) to pass through the seventy-fifth electrode (75) and the seventy-sixth electrode (76) to enter the ion extraction area (99), and are further transmitted to the migration spectrum or mass spectrometry for separation and detection. This stage is referred to as the pulse release stage.

2. The ion funnel trap control method according to claim 1, characterized in that: The periodic change of the electric field in the ion storage area (98) is achieved by modulating the electric potential of the sixty-fourth electrode (64), specifically: At the timing time t0≤t<t1, the electric field strength formed by the potential difference between the two ends of the resistor chain corresponding to the ion storage area (98) is E2, and the sixty-fourth electrode (64) applies the corresponding position potential V G1 The seventy-fifth electrode (75) and the seventy-sixth electrode (76) are respectively applied with a potential V G2 and V G3 Higher potentials V2 and V3, V3>V2>V G2 >V G3 ; At the timing time t1≤t<t2, the electric field strength formed by the potential difference between the two ends of the resistor chain corresponding to the ion storage area (98) is E2, and the sixty-fourth electrode (64) applies a potential V higher than the potential at the corresponding position. 11 , V 11 >V G1 , the seventy-fifth electrode (75) and the seventy-sixth electrode (76) are applied with potentials V2 and V3 respectively; At the timing time t2≤t<t3, the electric field strength E2 is formed by the potential difference between the two ends of the resistor chain corresponding to the ion storage area (98), and the sixty-fourth electrode (64) applies a higher voltage V 12 , V 12 >V 11 The seventy-fifth electrode (75) and the seventy-sixth electrode (76) apply corresponding position potentials V G2 and V G3 .

3. The ion funnel trap control method according to claim 1, characterized in that: The periodic change of the electric field in the ion storage area (98) is achieved by modulating the electric field intensity formed by the potential difference at both ends of the resistor chain corresponding to the ion storage area (98), specifically: At the timing time t0≤t<t1, the electric field strength formed by the potential difference between the two ends of the resistor chain corresponding to the ion storage area (98) is E2, and the sixty-fourth electrode (64) applies the corresponding position potential V G1 The seventy-fifth electrode (75) and the seventy-sixth electrode (76) are respectively applied with a potential V G2 and V G3 Higher potentials V2 and V3, V3>V2>V G2 >V G3 ; At the timing time t1≤t<t2, the electric field strength formed by the potential difference between the two ends of the resistor chain corresponding to the ion storage area (98) is E2, and the sixty-fourth electrode (64) applies a potential V higher than the potential at the corresponding position. 11 , V 11 >V G1 , the seventy-fifth electrode (75) and the seventy-sixth electrode (76) are applied with potentials V2 and V3 respectively; At the timing time t2≤t<t3, the electric field strength formed by the potential difference between the two ends of the resistor chain corresponding to the ion storage area (98) is E2', E2'>E2, and the sixty-fourth electrode (64) applies a potential V 11 The seventy-fifth electrode (75) and the seventy-sixth electrode (76) apply corresponding position potentials V G2 and V G3 .

4. An ion funnel trap control method according to any one of claims 1 to 3, characterized in that: The difference between timing time t3 and t0 is the ion gate working cycle T, which is 30 to 100 ms. The difference between timing time t1 and t0 is defined as injection time. The difference between timing time t2 and t1 is defined as storage time, which is 0 to 1000 μs. The difference between timing time t3 and t2 is defined as release time, which is 10 to 100 μs.

5. The ion funnel trap control method according to claim 1, characterized in that: When the ion funnel trap is working, the electric potential applied by the sixty-fourth electrode (64), the seventy-fifth electrode (75) and the seventy-sixth electrode (76) or the electric field strength formed by the potential difference at both ends of the resistor chain corresponding to the ion storage area (98) is periodically cyclically adjusted according to the time sequence.

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