CN110534395B - Ion gate control method for ion mobility spectrometer - Google Patents
Ion gate control method for ion mobility spectrometer Download PDFInfo
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- CN110534395B CN110534395B CN201910797555.6A CN201910797555A CN110534395B CN 110534395 B CN110534395 B CN 110534395B CN 201910797555 A CN201910797555 A CN 201910797555A CN 110534395 B CN110534395 B CN 110534395B
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Abstract
An ion gate control method for an ion mobility spectrometer includes controlling a full duty cycle of the ion gate through a gate-closing phase, a gate-opening phase, and a repulsion phase by voltages of a first grid electrode and a second grid electrode. In the door closing stage, the front edge of the ion cluster is cut smoothly, and the discrimination of the front edge of the ion cluster is reduced; the repulsion stage realizes the integral pushing of the ion group along the migration direction, and the tailing effect of the BN door is weakened. The method can realize the independent control of the front edge and the back edge of the ion cluster on one hand, and can reduce the tailing caused by the ion cluster cut by the ion gate on the other hand, thereby improving the resolution of the ion mobility spectrometer while reducing the discrimination of the ion gate.
Description
Technical Field
The present invention relates to ion mobility spectrometers, and more particularly, to a method for controlling an ion gate of an ion mobility spectrometer.
Background
The analysis process of the SA-IMS comprises two steps of ionization and migration. Firstly, different sample molecules are ionized, then ions are injected into a migration region at the same time through an ion gate, and different ions arrive at the end point in the migration region in sequence according to respective corresponding migration rates, so that the separation of samples is realized. The ion gate is a key device for carrying two processes, and is originally designed to be used as an ion controller in an in-flight mass spectrum, and the ion gate can prevent the ion from participating in a normal flight time analysis process by changing the advancing direction of the ion; since ions in the atmospheric environment collide with neutral gas molecules in the environment at any time, the movement of the ions can be regarded as uniform movement without inertia, and an ion gate used in the IMS can directly control the on-off of the ions. In the sample introduction process of the SA-IMS, the width and the number of ion clusters injected through an ion gate directly influence the half-peak width and the signal intensity of a spectrogram obtained.
The Bradbury-Nielsen ion gate (BNG) is the ion gate configuration commonly employed in current commercial IMS instruments. While BNGs allow ions to pass through, the two sets of wires apply the same potential difference across them. Since the metal diameters of the ion gates are all substantially less than 0.1mm, the overall width of the ion gate in the direction of ion travel can be neglected for a migration process with a motion of more than about 100mm in length. During the process that the ion gate blocks the passing of ions, the two groups of metal wires on the ion gate apply different electric potentials. Since the space electric field formed by the potential difference cannot be controlled in the plane of the ion gate, but radiates a space range to the periphery, the ion gate does not cut off the ion current smoothly when the gate is closed.
This phenomenon was first reported by Puton in 1989, and the larger the applied gate-closing voltage during the closing of the ion gate means that the more the electric field penetrates in front of the ion gate, and the more "pulling" of the ion packet becomes evident. Therefore, it is necessary to select a proper gate-closing voltage, which is also called critical gate-closing voltage, so that the ion gate can just lock the ion current at the gate-closing voltage. At this time, the electric field has the least influence on the ion current. On the basis of the report, a plurality of groups of research teams also discuss the problem in more detail, and as of 2011, the doctor of Durengzhai of the ocean team of Li, a great junctional article in China discloses another theoretical model of an ion gate, namely a three-region theory. The theoretical model divides the area near the ion gate metal wire into three parts, namely an emptying area, a dispersing area and a compressing area according to the size of an electric field, wherein ions in the emptying area disappear on the low-voltage metal wire of the ion gate after the door is closed; ions on the compression zone will move along the direction of the migration tube at a faster speed; the ions in the intermediate diverging region move forward at a relatively slow speed, resulting in broadening of the ion packet. How to obtain a good spectrogram effect and improve the resolution of an ion mobility spectrometer is a problem in the prior art.
Disclosure of Invention
The invention mainly aims to overcome the defects of the prior art and provide an ion gate control method for an ion mobility spectrometer so as to obtain a better spectrogram effect and improve the resolution of the ion mobility spectrometer.
In order to achieve the purpose, the invention adopts the following technical scheme:
an ion gate control method for an ion mobility spectrometer, the ion gate comprising a first grid electrode and a second grid electrode which are insulated from each other and arranged in an ion migration direction inside an ion mobility tube, the first grid electrode and the second grid electrode being arranged in parallel and staggered with equal spacing on the same plane perpendicular to an axial direction of the ion mobility tube, the ion mobility tube being divided into an ionization region and a migration region by the ion gate, the ion gate operating in a positive ion mode, wherein the method comprises periodically controlling a state of the ion gate through the following three stages:
a door closing stage, in which the voltage of the first grid electrode is kept at V1 offMaintaining the voltage of the second grid electrode at V2 offIn which V is1 offAnd V2 offThe selection of (1) satisfies the following conditions: the resulting voltage difference prevents ions in the ionization region from passing through the ion gate into the mobility region.
And (3) door opening stage: maintaining the voltage of the first grid electrode at V1 onMaintaining the voltage of the second grid electrode at V2-openingIn which V is1 onAnd V2-openingThe selection of (1) satisfies the following conditions: the resulting voltage difference allows ions in the ionization region to pass through the ion gate into the mobility region;
a repulsion stage: maintaining the voltage of the first grid electrode at V1 push awayMaintaining the voltage of the second grid electrode at V2 push awayIn which V is1 push awayAnd V2 push awayThe selection of (1) satisfies the following conditions: v1 push away-V2 push awayAnd V1 off-V2 offThe same sign, and | V1 push away-V2 push away|≤|V1 off-V2 offI, and V1 push away＞V1 on，V2 push away＞V2-opening。
Further:
the door closing stage is long enough to enable ion distribution to reach dynamic stability, the door opening stage is long enough to be required door opening time, and the delay stage is long enough to enable ion clusters to be separated from the ion gate voltage change influence range.
The V is2 offAnd said V1 offVoltage difference of and the V2 push awayAnd said V1 push awayIs equal to or slightly greater than the critical door-closing voltage difference at which ions cannot pass through at all, said V2-openingAnd said V1 onIs equal to or close to the voltage difference that gives the ions maximum transmittance.
In the repulsion stage, the voltage gradient behind the ion gate is 1-10 times of the voltage gradient of the migration area in the door opening stage.
The V is1 onThe voltage of the position of the ion gate when the uniform electric field exists in the migration tube is maintained, namely the reference voltage of the position.
In the door opening stage, the V1 on＝V2-opening＝V1 on。
The first grid electrode and the second grid electrode are both composed of metal wires which are identical in shape, parallel to each other and equal in wire spacing.
An ion gate control method for an ion mobility spectrometer, the ion gate comprising a first grid electrode and a second grid electrode which are insulated from each other and arranged in an ion migration direction inside an ion mobility tube, the first grid electrode and the second grid electrode being arranged in parallel and staggered at equal intervals on the same plane perpendicular to an axial direction of the ion mobility tube, the ion mobility tube being divided into an ionization region and a migration region by the ion gate, the ion gate operating in a negative ion mode, wherein the method comprises periodically controlling a state of the ion gate through the following three stages:
a door closing stage, in which the voltage of the first grid electrode is kept at V1 offMaintaining the voltage of the second grid electrode at V2 offIn which V is1 offAnd V2 offThe selection of (1) satisfies the following conditions: the resulting voltage difference prevents ions in the ionization region from passing through the ion gate into the mobility region.
And (3) door opening stage: maintaining the voltage of the first grid electrode at V1 onMaintaining the voltage of the second grid electrode at V2-openingIn which V is1 onAnd V2-openingThe selection of (1) satisfies the following conditions: the resulting voltage difference allows ions in the ionization region to pass through the ion gate into the mobility region;
repulsion stage: maintaining the voltage of the first grid electrode at V1 push awayMaintaining the voltage of the second grid electrode at V2 push awayIn which V is1 push awayAnd V2 push awayThe selection of (1) satisfies the following conditions: v1 push away-V2 push awayAnd V1 off-V2 offThe same sign, and | V1 push away-V2 push away|≤|V1 off-V2 offI, and V1 push away＜V1 on，V2 push away＜V2-opening。
Further:
the door closing stage is long enough to enable ion distribution to reach dynamic stability, the door opening stage is long enough to be required door opening time, and the delay stage is long enough to enable ion clusters to be separated from the ion gate voltage change influence range.
The V is2 offAnd said V1 offVoltage difference of and the V2 push awayAnd said V1 push awayIs equal to or slightly greater than the critical door-closing voltage difference at which ions cannot pass through at all, said V2-openingAnd said V1 onIs equal to or close to the voltage difference that gives the ions maximum transmittance.
An ion gate controlled by the ion gate control method.
An ion mobility spectrometer using the ion gate.
The invention has the following beneficial effects:
the ion gate control method changes the voltage of the first grid electrode and the second grid electrode of the ion gate through periodic three-state control of the ion gate, regulates and controls the electric field distribution behind the ion gate, changes the three-area distribution of the clear area, the divergent area and the compression area, simultaneously raises the voltage of the two groups of electrodes of the ion gate in a positive mode after the gate is opened, and simultaneously lowers the voltage of the two groups of electrodes in a negative mode, so that a high electric field area can be formed behind the ion gate, ion clusters are rapidly pushed away from the ion gate area, and the compression of the divergent area is realized while the clear area is minimized. By the control method, on one hand, discrimination caused by irregular chopping of the BN door can be reduced by using smaller voltage difference of the two groups of electrodes (preferably, the minimum critical door-closing voltage difference which just enables ions to completely not pass is adopted), and on the other hand, the problem that ion clusters entering a migration zone are easy to produce serious tailing when the door-closing voltage is too small is effectively solved, namely, tailing can not be produced when the door-closing voltage of the BN door is very small, ion clusters are compressed, and ion cluster broadening is reduced. Therefore, the ion mass compression method can eliminate discrimination of the ion gate on ions with slower migration speed, improve discrimination effect of the BN gate in the ion mobility spectrometry, and simultaneously can realize ion mass compression, reduce ion mass tailing and shorten ion mass broadening. Since the high field intensity region after the ion gate finally enters the low field intensity region in the migration tube, the ion cluster broadening is reduced, and the resolution of the ion mobility spectrometer is improved.
In a word, the method utilizes the influence of the change of an electric field on the movement of ions, and controls the voltages of two groups of electrodes of the BN gate to periodically change along with time under the three states, so that the area of a divergent zone is reduced, a compression zone is enlarged, fewer ions are expanded, more ion clusters are compressed, the discrimination of an ion mobility spectrometer is improved while the discrimination of the ion gate is reduced, and a better spectrogram effect can be obtained.
Drawings
Fig. 1 is a schematic view of an ion mobility tube structure using a BN gate, in which 1 is an ion gate, 2 is an ionization region, and 3 is a mobility region.
Fig. 2 is a timing diagram of voltage control in the positive ion mode of the ion gate control method according to an embodiment of the invention. Wherein the voltage of the electrode assembly 1 is at V1 off、V1 on、V1 push awayAt a voltage of V of the electrode assembly 22 off、V2-opening、V2 push awayTo change between.
Fig. 3 is a timing diagram of voltage control in the negative ion mode of an ion gate control method according to another embodiment of the present invention. Wherein the voltage of the electrode assembly 1 is at V1 off、V1 on、V1 push awayAt a voltage of V of the electrode assembly 22 off、V2-opening、V2 push awayTo change between.
Fig. 4 to 6 are ion mobility diagrams obtained by measuring the mixed sample by using different gate-closing timings according to two comparative examples and the example of the present invention, respectively.
Detailed Description
The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.
Referring to fig. 1 and 2, in an embodiment, an ion gate control method for an ion mobility spectrometer, the ion gate 1 includes a first grid electrode 1a and a second grid electrode 1b which are insulated from each other and arranged in an ion migration direction inside an ion mobility tube, the first grid electrode 1a and the second grid electrode 1b are arranged in parallel and staggered with equal intervals on a same plane perpendicular to an axial direction of the ion mobility tube, and the ion mobility tube is divided into an ionization region 2 and a migration region 3 by the ion gate 1. The two groups of electrodes are positioned on the same plane, which means that the two groups of electrodes are positioned on the same plane or two planes with negligible distance in the axial direction of the migration tube. Optionally, the first grid electrode is closer to an ionization region of the ion gate than the second grid electrode.
The ion gate operates in a positive ion mode, the ion gate control method comprising periodically controlling the state of the ion gate through three time interval phases:
a door closing stage, in which the voltage of the first grid electrode is kept at V1 offMaintaining the voltage of the second grid electrode at V2 offIn which V is1 offAnd V2 offThe selection of (1) satisfies the following conditions: the resulting voltage difference prevents ions in the ionization region from passing through the ion gate into the mobility region. Preferably, the voltage difference is a critical voltage difference just enough to prevent all ions from passing through the ion gate;
and (3) door opening stage: maintaining the voltage of the first grid electrode at V1 onMaintaining the voltage of the second grid electrode at V2-openingIn which V is1 onAnd V2-openingThe selection of (1) satisfies the following conditions: the resulting voltage difference allows ions in the ionization region to pass through the ion gate into the mobility region. Preferably, the voltage difference is such that both ions have the maximum transmittance。
A repulsion stage: maintaining the voltage of the first grid electrode at V1 push awayMaintaining the voltage of the second grid electrode at V2 push awayIn which V is1 push awayAnd V2 push awayThe selection of (1) satisfies the following conditions: v1 push away-V2 push awayAnd V1 off-V2 offThe same sign, and | V1 push away-V2 push away|≤|V1 off-V2 offI, and V1 push away＞V1 on，V2 push away＞V2-opening. Preferably, the voltage difference is a critical voltage difference just short of all ions passing through the ion gate.
The discrimination of the BN door is caused by the unevenness of chopping, the unevenness degree is determined by the magnitude of the door closing voltage, and therefore the weakest discrimination is the occasion that the door closing voltage of the BN door can just close the door. However, the problem with too small a gate-closing voltage is that ion packets entering the mobility zone can produce very severe tailing (as the three-zone theory mentioned in the background). In the method, the voltages of the two groups of electrodes of the BN gate are periodically changed along with time under the three states, and the voltages of the two groups of electrodes of the BN gate are simultaneously raised after the opening of the BN gate is finished, so that a high electric field area is formed behind the ion gate, ion clusters are rapidly pushed away from an ion gate area, and the phenomenon that tailing is not generated when the closing voltage of the BN gate is very small is realized. The method utilizes the influence of the change of the electric field on the movement of ions, and can improve the resolution of the ion mobility spectrometer while reducing the discrimination of an ion gate.
In a preferred embodiment, the time length of the door closing phase is sufficient to enable the ion distribution to achieve dynamic stability, the time length of the door opening phase is the required door opening time, and the time length of the door closing phase is sufficient to enable the ion packet to be separated from the ion gate voltage variation influence range.
According to the method, when the voltages of the two groups of electrodes are raised in the repulsion stage, the field intensity change after the ion gate is triggered, the ion clusters are compressed and pushed away from the ion gate area, the ion clusters at the edge are pushed to the tube wall to be annihilated, and the annihilation amount is related to the field intensity change after the ion gate, namely, the field intensity change after the ion gate is related to the voltage change amount, the length of the migration tube, the size of the migration tube and the like.
In a preferred embodiment, in the repulsion phase, the voltage gradient after the ion gate is 1-10 times of the voltage gradient in the door opening phase.
In a preferred embodiment, said V1 onThe voltage of the position of the ion gate when the uniform electric field exists in the migration tube is maintained, namely the reference voltage of the position.
In a preferred embodiment, the voltage applied to the first grid electrode 1a and the second grid electrode 1b during the door-open phase is equal to V1 off。
In another embodiment, the ion gate operates in a negative ion mode, the ion gate control method comprising periodically controlling the state of the ion gate through three phases:
a door closing stage, in which the voltage of the first grid electrode is kept at V1 offMaintaining the voltage of the second grid electrode at V2 offIn which V is1 offAnd V2 offThe selection of (1) satisfies the following conditions: the resulting voltage difference prevents ions in the ionization region from passing through the ion gate into the mobility region. Preferably, the voltage difference is a critical voltage difference just enough to prevent all ions from passing through the ion gate;
and (3) door opening stage: maintaining the voltage of the first grid electrode at V1 onMaintaining the voltage of the second grid electrode at V2-openingIn which V is1 onAnd V2-openingThe selection of (1) satisfies the following conditions: the resulting voltage difference allows ions in the ionization region to pass through the ion gate into the mobility region. Preferably, the voltage difference is such that both ions have the maximum transmittance.
A repulsion stage: maintaining the voltage of the first grid electrode at V1 push awayMaintaining the voltage of the second grid electrode at V2 push awayIn which V is1 push awayAnd V2 push awayThe selection of (1) satisfies the following conditions: v1 push away-V2 push awayAnd V1 off-V2 offThe same sign, and | V1 push away-V2 push away|≤|V1 off-V2 offI, and V1 push away＜V1 on，V2 push away＜V2-opening. Preferably, the voltage difference is such thatThe ions are all unable to pass through the critical voltage difference of the ion gate.
In another embodiment, an ion gate is controlled using the ion gate control method of any of the preceding embodiments.
In yet another embodiment, an ion mobility spectrometer employs an ion gate as described in any of the previous embodiments.
The features and operation of exemplary embodiments are further described below in conjunction with the following figures.
An ion transport tube system is shown in detail in figure 1. In a typical embodiment, the two sets of electrodes 1a, 1b of the ion gate are each formed from wires of the same shape, parallel to each other and at equal wire spacings, the two sets of electrodes 1a, 1b being in the same plane or planes at negligible axial distances. The ion transfer tube is divided into an ionization region 2 and a transfer region 3 by an ion gate 1. The ion gate 1 may be controlled in voltage to pass ions.
In an exemplary embodiment, as shown in fig. 2, an ion gate control method for improving the discrimination effect of a BN gate in an ion mobility spectrometry, the ion gate operating in a positive ion mode, controls the state of the ion gate 1 to repeatedly cycle between a closed-gate state, an open-gate state, and a repulsion state.
An ion cluster has a leading edge and a trailing edge, the more uneven the leading edge, the more discriminatory. Poor discrimination requires a small difference in the closing voltage. The tailing of the ion cluster is determined by the divergent zone, and the tailing can be reduced by reducing the area of the divergent zone, so that the broadening is shortened. The door closing state in the invention determines the front clearance zone, but is irrelevant to the broadening of the compressed ion cluster. The repulsion state determines the back edge clearance zone. The invention optimizes the front edge of the ion cluster by using the door closing state and optimizes the back edge of the ion cluster by using the repulsion state.
According to the control method of the invention, wherein the door-closed state is maintained in the door-closed phase, the control unit controls the application of V on the first grid electrode 1a1 offApplying V to the second grid electrode 1b2 off(ii) a Wherein V1 offIs the voltage at that position without an ion gate, V2 offHigher than V1 offAnd just so that the ions cannot pass through them all. In the shape of a door closingIn this state, the ion gate of the ionization region reaches the ion gate continuously and annihilates on the ion gate, and since the voltage difference of the two sets of metal electrodes of the ion gate at this stage is small, the critical gate-closing voltage difference which just makes the ions not pass through completely is preferred, so that the ion front is as flat as possible. In addition, the necessity of introducing the door-closed state is that the door-closing voltage of the two sets of electrodes in the repulsion state can be very high, even exceeding the voltage of the metal ring in the ionization region, which results in that the ions generated in the ionization region in the door-closed state are likely to be pushed back by the ion gate, and no ions exist in front of the ion gate.
Wherein the door-open state is maintained in the door-open stage, the control unit controls the V applied on the first grid electrode 1a and the second grid electrode 1b1 onAnd V2-openingIs equal to V1 offAt this time, the ions can normally pass through the ion gate.
Wherein the repulsion state is maintained in the repulsion stage, the control unit controls the application of V on the first grid electrode 1a1 push awayApplying V to the second grid electrode 1b2 push away(ii) a Wherein V1 push awayHigher than V1 on，V2 push awayHigher than V2-openingAnd just so that the ions cannot pass through them all. In the repulsion state, because the voltage difference of the two groups of metal electrodes of the ion gate at this stage is the critical gate-closing voltage which just can not make all the ions pass, the clearance zone is as small as possible, and the ions passing through the ion gate are less rewound to the ion gate. Meanwhile, the voltages of the two groups of metal electrodes are higher than the voltages of the two groups of metal electrodes in a door closing state, so that the ion diffusion area compression caused by the change of the electric field behind the ion door is realized.
Therefore, the ion gate control method controls the ion gate voltage to influence the electric field near the ion gate by periodically changing the voltages of the two groups of electrodes of the BN gate along with time under the tri-state condition, and improves the resolution of the ion mobility spectrometer while reducing the discrimination of the ion gate (ions with different mobility K can almost pass through the BN gate without discrimination by adopting the minimum critical gate-closing voltage difference).
Preferably, the duration of the door-closing state is sufficient to enable the ion distribution to achieve dynamic stability, the duration of the door-opening state is the required door-opening time, and the duration of the repulsion state is sufficient to enable the ion packet to be separated from the ion gate voltage change influence range.
Preferably, the voltage gradient after the ion gate in the repulsion state is 1 to 10 times of the voltage gradient in the door closing state.
The method of controlling an ion gate of one embodiment, said ion gate operating in positive ion mode, comprises the steps of: firstly, in a door closing state, controlling the voltage of a first grid electrode 1a of the BN door to be a reference voltage U0 at the position in the migration tube, and controlling a second grid electrode 1b to be U0+ UGVD, wherein the UGVD is a critical door closing voltage difference; then, the voltage of the two groups of metal wire electrodes 1a and 1b is controlled to be U0 in the door opening state, and finally, the voltage of the first grid electrode 1a is controlled to be U0+ Ur and the voltage of the second grid electrode 1b is controlled to be U0+ UGVD + Ur in the repulsion state.
In one embodiment, the ion gate operates in positive ion mode, as shown in fig. 2, during a time interval t corresponding to a closed state1The voltage of the first grid electrode 1a is kept at V1 offThe voltage of the second grid electrode 1b is kept at V2 off(ii) a Wherein V2 off>V1 offJust so that the ions cannot pass through all. The ion gate of the ionization region continuously reaches the ion gate and is annihilated on the ion gate 1, and the voltage difference of two groups of metal electrodes of the ion gate is critical gate-closing voltage, so that the front edge of ion clusters in the ionization region 2-1 is as flat as possible.
Time interval t corresponding to door opening state2In the first grid electrode 1a and the second grid electrode 1b, V is applied1 onAnd V2-openingAnd V is1 on＝V2-openingAt this time, the ions can normally pass through the ion gate.
At intervals t corresponding to repulsion conditions3In the first grid electrode 1a, V is applied1 push away Second grid electrode 1b applying V2 push away；V1 push away>V1 on，V2 push away>V2-openingAnd V is2 push away>V1 push awayJust so that the ions cannot pass through all. The voltage difference between the two groups of metal electrodes is critical door-closing voltage, so that the clearance area is as small as possible, and less ions passing through the ion gate are poured back to the ion gate. Two groups of metal electrodes simultaneouslyThe voltage of the pole is greater than t1The voltage of the two groups of metal electrodes realizes the compression of the ion diffusion area generated by the change of the electric field in the migration area 2-2.
Application example
The structural model of the ion migration tube is shown in figure 1, the electric field intensity of an ionization region is 50V/mm, the electric field intensity of a migration region is 50V/mm, the length of the migration region is 10mm, the position of an ion gate is the center of a uniform electric field and is composed of metal wires with the energy section of 0.1mm, and the wire spacing is 1 mm. In this example, the ion gate operates in positive ion mode.
In order to demonstrate the effect of the ion gate device, three different gate-closing timings were used for two samples containing the relative molecular masses M58 and 598, and fig. 4, 5, and 6 are ion mobility spectrograms obtained by measuring the mixed samples using the three gate-closing timings, respectively. The first gate-closing sequence is to cycle the ion gate between a gate-closed state and a gate-opened state, the duration of t3 is 0, and the ion mobility spectrum is optimized at the leading edge as shown in fig. 4. The second gate-closing sequence is to cycle the ion gate between the repulsion state and the gate-opening state, the duration of t1 is 0, and the ion mobility spectrum is optimized at the trailing edge as shown in fig. 5. Third door-closing timing according to the control method of the present invention, t1 and t3 are not 0, and are optimized in the transition state, and the ion mobility spectrum is shown in fig. 6. As shown in fig. 4, although two sample peaks can be seen only in the closed-door state, the peak shape is very poor, only one sample peak can be seen only in the repulsive state in fig. 5, the discrimination is severe, and fig. 6 shows that both sample peaks exist and the peak shape is good when the ion gate voltage timing sequence used in the present invention is used.
The foregoing is a more detailed description of the invention in connection with specific/preferred embodiments and is not intended to limit the practice of the invention to those descriptions. It will be apparent to those skilled in the art that various substitutions and modifications can be made to the described embodiments without departing from the spirit of the invention, and these substitutions and modifications should be considered to fall within the scope of the invention.
Claims (14)
1. An ion gate control method for an ion mobility spectrometer, the ion gate comprising a first grid electrode and a second grid electrode arranged in an ion mobility tube in an insulated manner from each other, the first grid electrode and the second grid electrode being in a plane perpendicular to the direction of ion mobility, wherein the first grid electrode is coplanar with the second grid electrode or the first grid electrode is closer to an ionization region of the ion gate than the second grid electrode, the ion mobility tube operating in a positive polarity mode, the control method comprising controlling a complete duty cycle of the ion gate to undergo the following phases:
a door closing stage: maintaining the voltage of the first grid electrode at V1 offMaintaining the voltage of the second grid electrode at V2 offIn which V is1 offAnd V2 offThe selection of (1) satisfies the following conditions: the generated voltage difference prevents ions in the ionization region from passing through the ion gate into the mobility region;
and (3) door opening stage: maintaining the voltage of the first grid electrode at V1 onMaintaining the voltage of the second grid electrode at V2-openingIn which V is1 onAnd V2-openingThe selection of (1) satisfies the following conditions: the resulting voltage difference allows ions in the ionization region to pass through the ion gate into the mobility region;
a repulsion stage: maintaining the voltage of the first grid electrode at V1 push awayMaintaining the voltage of the second grid electrode at V2 push awayIn which V is1 push awayAnd V2 push awayThe selection of (1) satisfies the following conditions: v1 push away-V2 push awayAnd V1 off-V2 offThe same sign, and | V1 push away-V2 push away|≤|V1 off-V2 offI, and V1 push away＞V1 on，V2 push away＞V2-opening。
2. The ion gate control method of claim 1, wherein-1000 ≦ V in the gate-closing phase1 off-V2 off≤-50。
3. The ion gate control method of claim 2, whichCharacterized in that V is more than or equal to 400 at the door closing stage1 off-V2 off≤-80。
4. An ion gate control method as claimed in claim 1, 2 or 3, characterized in that in the gate-open phase, 0 ≦ V1 on-V2-opening≤d×|EdWhere d is the spacing between the first and second grid electrodes, EdIs the migration zone electric field strength.
5. The ion gate control method of any one of claims 1 to 3, wherein-500. ltoreq. V in the repulsion stage1 push away-V2 push away≤0。
6. The ion gate control method of claim 5, wherein-200. ltoreq. V in the repulsion stage1 push away-V2 push away≤-40。
7. A method of ion gate control as claimed in any one of claims 1 to 3, wherein one or more of the following conditions are met in the duty cycle:
V1 off＝V1 on；
V1 push away＝V1 on；
V1 on＝V1 push away＝V1 off；
V1 on＝V1 push away＝V1 off＝V2-opening；
V1 push away＞V1 off；
V2 push away＞V2 off。
8. An ion gate control method for an ion mobility spectrometer, the ion gate comprising a first grid electrode and a second grid electrode arranged in an ion mobility tube in an insulated manner, the first grid electrode and the second grid electrode being in a plane perpendicular to the direction of ion mobility, wherein the first grid electrode is coplanar with the second grid electrode or the first grid electrode is closer to an ionization region of the ion gate than the second grid electrode, the ion mobility tube operating in a negative polarity mode, the control method comprising controlling a complete duty cycle of the ion gate to undergo the following phases:
a door closing stage: maintaining the voltage of the first grid electrode at V1 offMaintaining the voltage of the second grid electrode at V2 offIn which V is1 offAnd V2 offThe selection of (1) satisfies the following conditions: the generated voltage difference prevents ions in the ionization region from passing through the ion gate into the mobility region;
and (3) door opening stage: maintaining the voltage of the first grid electrode at V1 onMaintaining the voltage of the second grid electrode at V2-openingIn which V is1 onAnd V2-openingThe selection of (1) satisfies the following conditions: the resulting voltage difference allows ions in the ionization region to pass through the ion gate into the mobility region;
a repulsion stage: maintaining the voltage of the first grid electrode at V1 push awayMaintaining the voltage of the second grid electrode at V2 push awayIn which V is1 push awayAnd V2 push awayThe selection of (1) satisfies the following conditions: v1 push away-V2 push awayAnd V1 off-V2 offThe same sign, and | V1 push away-V2 push away|≤|V1 off-V2 offI, and V1 push away＜V1 on，V2 push away＜V2-opening。
9. The ion gate control method of claim 8, wherein 50 ≦ V during the gate-closing phase1 off-V2 off≤100。
10. The ion gate control method of claim 9, wherein 80 ≦ V in the gate-closing phase1 off-V2 off≤400。
11. An ion gate control method as claimed in claim 8, 9 or 10, characterized in that during said door opening phase, - (d × | E)d|)≤V1 on-V2-opening≤0，Wherein d is the distance between the first and second grid electrodes, EdIs the migration zone electric field strength.
12. The ion gate control method of any one of claims 8 to 10, wherein in the repulsion stage, V is 0. ltoreq. V1 push away-V2 push away≤500。
13. The ion gate control method of claim 12, wherein in the repulsion stage, V is 40 ≤ V1 push away-V2 push away≤200。
14. An ion gate control method as claimed in any one of claims 8 to 10, wherein one or more of the following conditions are met in said duty cycle:
V1 off＝V1 on；
V1 push away＝V1 on；
V1 on＝V1 push away＝V1 off；
V1 on＝V1 push away＝V1 off＝V2-opening；
V1 push away＜V1 off；
V2 push away＜V2 off。
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| CN106098528A (en) * | 2016-06-14 | 2016-11-09 | 清华大学深圳研究生院 | A kind of apparatus and method reducing ionic migration spectrometer ion gate inductive kick |
| CN106783506A (en) * | 2016-12-08 | 2017-05-31 | 中国科学院合肥物质科学研究院 | The ionic migration spectrometer and detection method of the voltage-controlled ion gate processed of a kind of utilization dipulse, Asymmetric Electric |
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