阅读说明：本技术 一种用于离子迁移谱仪的离子门控制方法 (Ion gate control method for ion mobility spectrometer ) 是由 倪凯 陈海 余泉 钱翔 王晓浩 于 2019-08-13 设计创作，主要内容包括：一种用于离子迁移谱仪的离子门控制方法,包括通过第一栅网电极和第二栅网电极的电压,以控制所述离子门的一个完整工作周期经历开门阶段、剪切阶段、推斥阶段、关门阶段。其中,剪切阶段实现对离子团后沿的快速切断,减小离子团在剪切过程中的轴向拉伸；推斥阶段实现对离子团在沿迁移方向上的整体推移,利用推斥电场的非均匀性实现离子团轴向压缩。本方法一方面可以实现对离子团切割和分离过程的分别独立控制,另一方面可以减小离子门切割离子团造成的后沿拖尾,有利于提高离子迁移谱仪的分辨能力。(An ion gate control method for an ion mobility spectrometer includes controlling a complete duty cycle of the ion gate through a gate opening phase, a shearing phase, a repulsion phase, and a gate closing phase by voltages of a first grid electrode and a second grid electrode. In the shearing stage, the back edge of the ion cluster is quickly cut off, and the axial stretching of the ion cluster in the shearing process is reduced; the repulsion stage realizes the integral pushing of the ion cluster along the migration direction, and the axial compression of the ion cluster is realized by utilizing the heterogeneity of the repulsion electric field. The method can realize the independent control of the ion cluster cutting and separating processes, and can reduce the trailing edge tailing caused by the ion cluster cutting of the ion gate, thereby being beneficial to improving the resolution capability of the ion mobility spectrometer.)

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:

And (3) door opening stage: maintaining the voltage of the first grid electrode at V_{1 on}Maintaining the voltage of the second grid electrode at V_2-openingIn which V is_{1 on}And V_2-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;

And (3) a shearing stage: maintaining the voltage of the first grid electrode at V_{1 scissor}Maintaining the voltage of the second grid electrode at V_{2 scissor}In which V is_{1 scissor}And V_{2 scissor}The selection of (1) satisfies the following conditions: i V_{1 scissor}-V_{2 scissor}|＞|V_{1 on}-V_2-openingI, and V_{1 scissor}+V_{2 scissor}＜V_{1 on}+V_2-opening；

A repulsion stage: maintaining the voltage of the first grid electrode at V_{1 push away}Maintaining the voltage of the second grid electrode at V_{2 push away}In which V is_{1 push away}And V_{2 push away}The selection of (1) satisfies the following conditions: v_{1 push away}-V_{2 push away}And V_{1 scissor}-V_{2 scissor}Is of opposite sign, or V_{1 push away}+V_{2 push away}＞V_{1 on}+V_2-opening；

A door closing stage, in which the voltage of the first grid electrode is kept at V_{1 off}Maintaining the voltage of the second grid electrode at V_{2 off}In which V is_{1 off}And V_{2 off}The 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.

2. The ion gate control method of claim 1, wherein 0 ≦ V during the gate open phase_{1 on}-V_2-opening≤d×|E_dWhere d is the spacing between the first and second grid electrodes, E_dIs the migration zone electric field strength.

3. The ion gate control method of claim 1 or 2, wherein in the shearing phase, 50 ≦ V_{1 scissor}-V_{2 scissor}1000 or less, preferably 200 or less V_{1 scissor}-V_{2 scissor}≤600。

4. The ion gate control method of any one of claims 1 to 3, wherein-1000. ltoreq. V in the repulsion stage_{1 push away}-V_{2 push away}V is not less than-50, preferably not less than-600_{1 push away}-V_{2 push away}≤-200。

5. The ion gate control method of any of claims 1 to 4, wherein-1000 ≦ V during the gate-closing phase_{1 off}-V_{2 off}V is not less than-50, preferably not less than-400_{1 off}-V_{2 off}≤-80。

6. An ion gate control method as claimed in any one of claims 1 to 5, wherein one or more of the following conditions are met in said duty cycle:

V_{1 scissor}＝V_{1 on}；

V_{1 push away}＝V_{1 on}；

V_{1 off}＝V_{1 on}；

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}；

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}＝V_2-opening；

V_{1 push away}＝V_{1 off}；

V_{2 push away}＝V_{2 off}。

7. 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:

And (3) door opening stage: maintaining the voltage of the first grid electrode at V_{1 on}Maintaining the voltage of the second grid electrode at V_2-openingIn which V is_{1 on}And V_2-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;

And (3) a shearing stage: maintaining the voltage of the first grid electrode at V_{1 scissor}Maintaining the voltage of the second grid electrode at V_{2 scissor}In which V is_{1 scissor}And V_{2 scissor}the selection of (1) satisfies the following conditions: i V_{1 scissor}-V_{2 scissor}|＞|V_{1 on}-V_2-openingI, and V_{1 scissor}+V_{2 scissor}＞V_{1 on}+V_2-opening；

A repulsion stage: maintaining the voltage of the first grid electrode at V_{1 push away}Maintaining the voltage of the second grid electrode at V_{2 push away}In which V is_{1 push away}And V_{2 push away}The selection of (1) satisfies the following conditions: v_{1 push away}-V_{2 push away}And V_{1 scissor}-V_{2 scissor}Is of opposite sign, or V_{1 push away}+V_{2 push away}＜V_{1 on}+V_2-opening；

A door closing stage, in which the voltage of the first grid electrode is kept at V_{1 off}Maintaining the voltage of the second grid electrode at V_{2 off}In which V is_{1 off}And V_{2 off}The selection of (1) satisfies the following conditions: the generated voltage difference prevents ions in the ionization region from passing through the ion gateAnd entering a migration area.

8. An ion gate control method as claimed in claim 7, characterized in that during said door opening phase, - (d × | E)_d|)≤V_{1 on}-V_2-openingNot more than 0, wherein d is the distance between the first grid electrode and the second grid electrode, E_dIs the migration zone electric field strength.

9. An ion gate control method according to claim 7 or 8, wherein-1000 ≦ V in the clipping stage_{1 scissor}-V_{2 scissor}V is not less than-50, preferably not less than-600_{1 scissor}-V_{2 scissor}≤-200。

10. The ion gate control method of any one of claims 7 to 9, wherein in the repulsion stage, V is 50 ≤ V_{1 push away}-V_{2 push away}1000 or less, preferably 200 or less V_{1 push away}-V_{2 push away}≤600。

11. An ion gate control method as claimed in any one of claims 7 to 10, wherein in the gate-closing phase, 50 ≤ V_{1 off}-V_{2 off}1000 or less, preferably 80 or less V_{1 off}-V_{2 off}≤400。

12. An ion gate control method as claimed in any one of claims 7 to 11, wherein one or more of the following conditions are met in said duty cycle:

V_{1 scissor}＝V_{1 on}；

V_{1 push away}＝V_{1 on}；

V_{1 off}＝V_{1 on}；

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}；

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}＝V_2-opening；

V_{1 push away}＝V_{1 off}；

V_{2 push away}＝V_{2 off}。

Technical Field

The invention relates to the field of ion mobility spectrometry, in particular to an ion gate control method for an ion mobility spectrometer.

Background

Ion Mobility Spectrometry (IMS) is a trace substance fast detection technology, and has the advantages of simple structure, high sensitivity, fast detection speed and normal-pressure operation. The ion mobility spectrometer controls charged particles to enter a drift region in a specific mode by opening and closing an ion gate, and the charged particles are detected by a detector after being separated.

The switching of the ion gate on-off gate state is typically achieved by varying the voltages of the first grid electrode G1 and the second grid electrode G2: when the voltage difference between the first grid electrode G1 and the second grid electrode G2 is small, the ion gate is opened, and ions pass through; when the voltage difference between the first grid electrode G1 and the second grid electrode G2 is large, the ion gate is closed, ions near the ion gate are hit to the ion gate with low voltage, and the ions cannot pass through, so that the closing is realized. A large number of ions are collected near the low voltage ion gate, and a blank space is formed near the high voltage ion gate due to lack of ions, resulting in non-flatness of the ion packet back edge.

The traditional ion gate timing control mode is to apply a pulse signal with fixed width and amplitude on an ion gate grid, and the main problem of the control mode is that the cutting shape of the back edge of an ion cluster is not ideal.

The above background disclosure is only for the purpose of assisting in understanding the inventive concepts and technical solutions of the present application and does not necessarily belong to the prior art of the present patent application, and is not used to assess novelty and inventiveness of the present application without explicit evidence to suggest that the above content has been disclosed before the filing date of the present patent application.

Disclosure of Invention

The main purpose of the present invention is to overcome the defects of the prior art and to provide an improved ion gate control method for an ion mobility spectrometer, so as to improve the flatness of the back edge shape of an ion cluster, thereby improving the resolution of an 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 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 positive polarity mode, the control method comprising controlling a full duty cycle of the ion gate to undergo the following phases:

And (3) door opening stage: maintaining the voltage of the first grid electrode at V_{1 on}Maintaining the voltage of the second grid electrode at V_2-openingIn which V is_{1 on}And V_2-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;

And (3) a shearing stage: maintaining the voltage of the first grid electrode at V_{1 scissor}Maintaining the voltage of the second grid electrode at V_{2 scissor}In which V is_{1 scissor}And V_{2 scissor}The selection of (1) satisfies the following conditions: i V_{1 scissor}-V_{2 scissor}|＞|V_{1 on}-V_2-openingI, and V_{1 scissor}+V_{2 scissor}＜V_{1 on}+V_2-opening；

A repulsion stage: maintaining the voltage of the first grid electrode at V_{1 push away}Maintaining the voltage of the second grid electrode at V_{2 push away}In which V is_{1 push away}And V_{2 push away}The selection of (1) satisfies the following conditions: v_{1 push away}-V_{2 push away}And V_{1 scissor}-V_{2 scissor}Is of opposite sign, or V_{1 push away}+V_{2 push away}＞V_{1 on}+V_2-opening；

A door closing stage, in which the voltage of the first grid electrode is kept at V_{1 off}Maintaining the voltage of the second grid electrode at V_{2 off}In which V is_{1 off}And V_{2 off}The 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.

Further:

In the door opening stage, V is more than or equal to 0_{1 on}-V_2-opening≤d×|E_dWhere d is the spacing between the first and second grid electrodes, E_dIs the migration zone electric field strength.

In the shearing stage, V is more than or equal to 50_{1 scissor}-V_{2 scissor}1000 or less, preferably 200 or less V_{1 scissor}-V_{2 scissor}≤600。

V is more than or equal to-1000 in the repulsion stage_{1 push away}-V_{2 push away}V is not less than-50, preferably not less than-600_{1 push away}-V_{2 push away}≤-200。

In the door closing stage, V is more than or equal to-1000_{1 off}-V_{2 off}V is not less than-50, preferably not less than-400_{1 off}-V_{2 off}≤-80。

One or more of the following conditions are met in the duty cycle:

V_{1 scissor}＝V_{1 on}；

V_{1 push away}＝V_{1 on}；

V_{1 off}＝V_{1 on}；

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}；

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}＝V_2-opening；

V_{1 push away}＝V_{1 off}；

V_{2 push away}＝V_{2 off}。

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:

And (3) door opening stage: maintaining the voltage of the first grid electrode at V_{1 on}Maintaining the voltage of the second grid electrode at V_2-openingIn which V is_{1 on}And V_2-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;

And (3) a shearing stage: maintaining the voltage of the first grid electrode at V_{1 scissor}Maintaining the voltage of the second grid electrode at V_{2 scissor}In which V is_{1 scissor}And V_{2 scissor}the selection of (1) satisfies the following conditions: i V_{1 scissor}-V_{2 scissor}|＞|V_{1 on}-V_2-openingI, and V_{1 scissor}+V_{2 scissor}＞V_{1 on}+V_2-opening；

A repulsion stage: maintaining the voltage of the first grid electrode at V_{1 push away}Maintaining the voltage of the second grid electrode at V_{2 push away}In which V is_{1 push away}And V_{2 push away}The selection of (1) satisfies the following conditions: v_{1 push away}-V_{2 push away}And V_{1 scissor}-V_{2 scissor}Is of opposite sign, or V_{1 push away}+V_{2 push away}＜V_{1 on}+V_2-opening；

A door closing stage, in which the voltage of the first grid electrode is kept at V_{1 off}Maintaining the voltage of the second grid electrode at V_{2 off}In which V is_{1 off}And V_{2 off}The 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.

Further:

During the door opening stage, - (d × | E)_d|)≤V_{1 on}-V_2-openingNot more than 0, wherein d is the distance between the first grid electrode and the second grid electrode, E_dElectric field intensity for migration zone。

In the shearing stage, V is more than or equal to-1000_{1 scissor}-V_{2 scissor}V is not less than-50, preferably not less than-600_{1 scissor}-V_{2 scissor}≤-200。

In the repulsion stage, V is more than or equal to 50_{1 push away}-V_{2 push away}1000 or less, preferably 200 or less V_{1 push away}-V_{2 push away}≤600。

In the door closing stage, V is more than or equal to 50_{1 off}-V_{2 off}1000 or less, preferably 80 or less V_{1 off}-V_{2 off}≤400。

One or more of the following conditions are met in the duty cycle:

V_{1 scissor}＝V_{1 on}；

V_{1 push away}＝V_{1 on}；

V_{1 off}＝V_{1 on}；

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}；

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}＝V_2-opening。

V_{1 push away}＝V_{1 off}；

V_{2 push away}＝V_{2 off}。

The invention has the following beneficial effects:

The invention provides an improved ion gate control method, which is characterized in that a shearing stage and a repulsion stage are added between the door opening stage and the door closing stage of an ion gate through the voltages of a first grid electrode and a second grid electrode, and the space distribution and the time domain motion characteristic of ions are influenced by an electric field. Wherein, the shearing stage realizes cutting off fast of ion group back porch, and the stage of repelling realizes moving the ascending whole of direction to ion group, can realize the independent control to ion gate cutting ion group process on the one hand, and on the other hand can improve the tailing that ion gate cutting ion group back porch caused, is favorable to the improvement of ion mobility spectrometer resolving power. The ion gate control method can enable the shape of the back edge of the ion cluster to be smoother, thereby improving the resolution of an ion mobility spectrogram.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Other features and advantages of the present invention will be described below.

Drawings

FIG. 1a is a front view of a first and second grid electrode of an ion gate structure in an ion mobility spectrometer;

FIG. 1b is a side view of a first and second grid electrode of an ion gate structure in an ion mobility spectrometer;

FIG. 1c is a side view of a first and second grid electrode of another ion gate structure in an ion mobility spectrometer;

FIG. 2 is a voltage timing diagram of one embodiment of an ion gate control method according to the present invention;

Fig. 3 is a voltage timing diagram of another embodiment of an ion gate control method according to the present invention.

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.

The ion gate control method of the present invention is used for controlling an ion gate of an ion mobility spectrometer including an ion mobility tube (not shown), in which an ionization region, an ion gate region, and a mobility region are sequentially formed along an ion mobility direction inside the ion mobility tube. The ion gate is located in the ion gate region and comprises a first grid electrode G1 and a second grid electrode G2 arranged in an ion mobility tube in an insulated manner from each other, as shown in fig. 1 a. The first grid electrode G1 and the second grid electrode G2 are located in a plane perpendicular to the direction of ion migration. Optionally, the first grid electrode G1 is coplanar with the second grid electrode G2, as shown in fig. 1 b. Alternatively, the first grid electrode G1 is close to the ionization source (not shown) in the ion mobility spectrometer and the second grid electrode G2 is close to the detector (not shown) in the ion mobility spectrometer, as shown in fig. 1 c. The first grid electrode G1 and the second grid electrode G2 are ion-permeable electrodes; the spacing d between the first grid electrode G1 and the second grid electrode G2 generally satisfies 0 ≦ d ≦ 2mm, where d is 0 indicating that the first grid electrode G1 and the second grid electrode G2 are coplanar and form a BN (Bradbury-Nielson) ion gate structure.

The ion transfer tube operates in a positive polarity mode or a negative polarity mode. The ion gate control method comprises controlling the ion gate to undergo four phases for one full duty cycle: a door opening stage, a shearing stage, a repulsion stage and a door closing stage.

According to the ion gate control method, a shearing stage and a repulsion stage are added between the door opening stage and the door closing stage of the ion gate, namely the time sequence of one complete working cycle of the ion gate is as follows: a door opening stage, a shearing stage, a repulsion stage and a door closing stage. The shearing stage realizes the quick cutting of the back edge of the ion cluster, reduces the forward migration speed of the ion cluster, even temporarily stops the forward migration of the ion cluster, and reduces the axial stretching of the ion cluster in the shearing process; the repulsion stage realizes the integral pushing of the ion cluster along the migration direction, and the axial compression of the ion cluster is realized by utilizing the heterogeneity of the repulsion electric field. In particular, the voltages applied to the ion gate grids in the repulsion stage and the door closing stage can be the same, and the voltages need to simultaneously meet the constraint conditions of the repulsion stage and the door closing stage, so that the repulsion stage and the door closing stage can be combined into a whole, and the control sequence is further simplified. The method can realize the independent control of the ion cluster cutting and separating processes, and can reduce the trailing edge tailing caused by the ion cluster cutting of the ion gate, thereby being beneficial to improving the resolution capability of the ion mobility spectrometer.

In one embodiment, a method of ion gate control for an ion mobility spectrometer is provided in which the ion mobility tube operates in a positive polarity mode, i.e., the direction of the electric field lines in the mobility region are directed from the ionization source to the detector.

The ion gate control method comprises controlling a full duty cycle of the ion gate to undergo the following four phases:

And (3) door opening stage: the voltage of the first grid electrode G1 is kept at V_{1 on}Second grid electrode G2The voltage is kept at V_2-openingRecord Δ V_{Opening device}＝V_{1 on}-V_2-opening(ii) a In the door opening stage, V_{1 on}And V_2-openingThe selection of (1) satisfies the following conditions: ions in the ionization region can pass through the ion gate to enter the migration region, and if the ions are kept in the door opening stage all the time, after a sufficient period of time (more than 1 second), the ions passing through the ion gate from the ionization region to enter the migration region impact on the absolute value | I of the current generated on the detector_{Opening device}| ≧ 10 pA. In general, | Δ V_{Opening device}|≤50。

And (3) a shearing stage: the voltage of the first grid electrode G1 is kept at V_{1 scissor}The voltage of the second grid electrode G2 is kept at V_{2 scissor}Record Δ V_Scissors＝V_{1 scissor}-V_{2 scissor}(ii) a In the shearing stage, V_{1 scissor}And V_{2 scissor}The selection of (1) satisfies the following conditions: | Δ V_Scissors|＞|ΔV_{Opening device}I, and V_{1 scissor}+V_{2 scissor}＜V_{1 on}+V_2-opening；|ΔV_Scissors|＞|ΔV_{Opening device}And | ensuring that the pressure difference between the first grid electrode G1 and the second grid electrode G2 can not enable ions to normally pass through, thereby achieving the purpose of cutting off ion clusters. V_{1 scissor}+V_{2 scissor}＜V_{1 on}+V_2-openingThe average potential of the ion gate area in the shearing stage is lower than that of the ion gate area in the door opening stage, the ion cluster on one side of the migration area is subjected to the acting force opposite to the migration electric field to decelerate, the movement is stopped, even the reverse movement is carried out, and the stretching of the ion cluster in the shearing stage in the migration direction is reduced. Therefore, the shearing stage realizes the rapid cutting-off of the back edge of the ion cluster, ions at the tail part of the ion cluster are annihilated on an ion gate with lower voltage, the forward migration speed of the ion cluster is reduced, the forward migration of the ion cluster is even temporarily stopped, even the ion cluster moves reversely, and the axial stretching of the ion cluster in the shearing process is reduced.

A repulsion stage: the voltage of the first grid electrode G1 is kept at V_{1 push away}The voltage of the second grid electrode G2 is kept at V_{2 push away}Record Δ V_{Push away}＝V_{1 push away}-V_{2 push away}(ii) a In the repulsion stage, V_{1 push away}And V_{2 push away}The selection of (1) satisfies the following conditions: Δ V_{Push away}And Δ V_ScissorsOf opposite sign, or V_{1 push away}+V_{2 push away}＞V_{1 on}+V_2-opening(ii) a During the shearing phase, when the voltage of the first grid electrode G1 is less than the potential of the second grid electrode G2, the positive ions will be collected and annihilated at the first grid electrode G1, and Δ V_{Push away}And Δ V_ScissorsThe opposite sign means that the potential of the first grid electrode G1 is greater than the potential of the second grid electrode G2, so that the ions originally collected near the first grid electrode G1 are pushed to the second grid electrode G2, thereby repelling the ion clusters. And V_{1 push away}+V_{2 push away}＞V_{1 on}+V_2-openingIt means that the average potential of the ion gate area in the repulsion stage is higher than that of the ion gate area in the door opening stage, and the ion packet is pushed forward along the direction of the electric field lines in the repulsion stage, so as to repel the ion packet. Therefore, in the repulsion stage, a positive thrust in the ion migration direction is applied to the whole ion cluster, and the whole ion cluster leaves the ion gate area and enters the migration area; the repulsion stage realizes the integral pushing of the ion cluster along the migration direction, and the axial compression of the ion cluster is realized by utilizing the heterogeneity of the repulsion electric field.

A door closing stage: the voltage of the first grid electrode G1 is kept at V_{1 off}The voltage of the second grid electrode G2 is kept at V_{2 off}Record Δ V_{Closing device}＝V_{1 off}-V_{2 off}. In the door closing phase, V_{1 off}and V_{2 off}The selection of (1) satisfies the following conditions: ions in the ionization region can be prevented from passing through the ion gate to enter the migration region, and if the ions are kept in the gate-closing stage all the time, after a sufficient period of time (more than 1 second), the ions passing through the ion gate from the ionization region to enter the migration region impact on the absolute value | I of the current generated on the detector_{Closing device}|≤0.9*|I_{Opening device}L. In general, | Δ V_{Closing device}and | is > 50. In the door closing stage, a voltage gradient in a direction different from the migration direction of the ions is formed, and the ions in the ion gate region are prevented from entering the migration region.

Preferably, 0. ltoreq. DELTA.V_{Opening device}≤d×|E_dWhere d is the spacing between the first grid electrode G1 and the second grid electrode G2, E_dIs the migration zone electric field strength.

Preferably, 50 ≦ Δ V_Scissors1000 or less, more preferably 200 or less ΔV_Scissors≤600。

Preferably-1000. ltoreq. DELTA.V_{Push away}Minus 50, more preferably minus 600. ltoreq. DELTA.V_{Push away}≤-200。

preferably-1000. ltoreq. DELTA.V_{Closing device}Minus 50 or less, more preferably minus 400 or less Δ V_{closing device}≤-80。

Alternatively, V_{1 scissor}＝V_{1 on}。

Alternatively, V_{1 push away}＝V_{1 on}。

Alternatively, V_{1 off}＝V_{1 on}。

Alternatively, V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}。

Alternatively, V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}＝V_2-opening。

Optionally, the voltage of the first grid electrode G1 is the same in the repulsion phase and the door-closing phase, V_{1 push away}＝V_{1 off}。V_{1 push away}、V_{1 off}Should be selected to satisfy the voltage selection condition in the repulsion stage and the door-closing stage. This can combine the repulsion stage and the door closing stage of the first grid electrode into one and further simplify the control sequence.

Optionally, the voltage of the second grid electrode G2 is the same in the repulsion phase and the door-closing phase, V_{2 push away}＝V_{2 off}。V_{2 push away}、V_{2 off}Should be selected to satisfy the voltage selection condition in the repulsion stage and the door-closing stage. This can combine the repulsion stage and the door closing stage of the second grid electrode into one and further simplify the control sequence.

In a preferred embodiment, the repulsion phase and the door-closing phase are at the same voltage, i.e. V_{1 push away}＝V_{1 off}And V is_{2 push away}＝V_{2 off}；V_{1 push away}、V_{2 push away}、V_{1 off}、V_{2 off}The voltage selection conditions of the repulsion stage and the door closing stage are simultaneously met; v_{1 on}＝V_{1 scissor}＝V_{1 off}＝V_2-openingAnd Δ V is not less than 50_Scissors1000 or less, more preferably 200 or less,. DELTA.V_ScissorsLess than or equal to 600, and-1000<ΔV_{Closing device}Δ V of ≦ 50, more preferably-400 ≦ Δ V_{Closing device}≤-80。

In another embodiment, a method of ion gate control for an ion mobility spectrometer is provided in which the ion mobility tube operates in a negative polarity mode, i.e., the direction of the electric field lines in the mobility region are directed from the detector to the ionization source. The negative polarity mode is different from the positive polarity mode in that positive ions are moved in the positive polarity mode and negative ions are moved in the negative polarity mode.

The ion gate control method comprises controlling a full duty cycle of the ion gate to undergo the following four phases:

And (3) door opening stage: the first grid electrode G1 is held at a voltage V_{1 on}The voltage of the second grid electrode G2 is kept at V_2-openingRecord Δ V_{Opening device}＝V_{1 on}-V_2-opening(ii) a In the door opening stage, V_{1 on}And V_2-openingThe selection of (1) satisfies the following conditions: ions in the ionization region can pass through the ion gate to enter the migration region, and if the ions are kept in the door opening stage all the time, after a sufficient period of time (more than 1 second), the ions passing through the ion gate from the ionization region to enter the migration region impact on the absolute value | I of the current generated on the detector_{Opening device}| ≧ 10 pA. In general, | Δ V_{Opening device}|≤50。

And (3) a shearing stage: the first grid electrode G1 is held at a voltage V_{1 scissor}The voltage of the second grid electrode G2 is kept at V_{2 scissor}Record Δ V_Scissors＝V_{1 scissor}-V_{2 scissor}(ii) a In the shearing stage, V_{1 scissor}And V_{2 scissor}The selection of (1) satisfies the following conditions: | Δ V_Scissors|＞|ΔV_{Opening device}I, and V_{1 scissor}+V_{2 scissor}＞V_{1 on}+V_2-opening。|ΔV_Scissors|＞|ΔV_{Opening device}And | ensuring that the pressure difference between the first grid electrode G1 and the second grid electrode G2 can not enable ions to normally pass through, thereby achieving the purpose of cutting off ion clusters. V_{1 scissor}+V_{2 scissor}＞V_{1 on}+V_2-openingThe average potential of the ion gate area in the shearing stage is higher than that in the door opening stage, the ion group on one side of the migration area is decelerated by the action force opposite to the migration electric field, and stops or even moves reversely, so that the shearing stage is reducedStretching of the ion cluster in the direction of migration. Therefore, the shearing stage realizes the rapid cutting-off of the back edge of the ion cluster, ions at the tail part of the ion cluster are annihilated on an ion gate with lower voltage, the forward migration speed of the ion cluster is reduced, the forward migration of the ion cluster is even temporarily stopped, even the ion cluster moves reversely, and the axial stretching of the ion cluster in the shearing process is reduced.

A repulsion stage: the first grid electrode G1 is held at a voltage V_{1 push away}The voltage of the second grid electrode G2 is kept at V_{2 push away}Record Δ V_{Push away}＝V_{1 push away}-V_{2 push away}(ii) a In the repulsion stage, V_{1 push away}And V_{2 push away}The selection of (1) satisfies the following conditions: Δ V_{Push away}And Δ V_ScissorsOf opposite sign, or V_{1 push away}+V_{2 push away}＜V_{1 on}+V_2-opening(ii) a In the shearing stage, when the potential of the first grid electrode G1 is greater than the potential of the second grid electrode G2, the negative ions will be collected and annihilated at the first grid electrode G1, and Δ V_{Push away}And Δ V_ScissorsThe opposite sign means that the first grid electrode G1 is at a lower potential than the second grid electrode G2, and therefore the ions originally collected near the first grid electrode G1 will be pushed towards the second grid electrode G2, so as to repel the ion clusters. And V_{1 push away}+V_{2 push away}＜V_{1 on}+V_2-openingIt means that the average potential of the ion gate area in the repulsion stage is smaller than the average potential of the ion gate area in the door opening stage, and the ion cluster is pushed forward along the migration direction in the repulsion stage, so as to achieve the purpose of repelling the ion cluster. Therefore, in the repulsion stage, a positive thrust in the ion migration direction is applied to the whole ion cluster, and the whole ion cluster leaves the ion gate area and enters the migration area; the repulsion stage realizes the integral pushing of the ion cluster along the migration direction, and the axial compression of the ion cluster is realized by utilizing the heterogeneity of the repulsion electric field.

A door closing stage: the first grid electrode G1 is held at a voltage V_{1 off}The voltage of the second grid electrode G2 is kept at V_{2 off}Record Δ V_{Closing device}＝V_{1 off}-V_{2 off}. In the door closing phase, V_{1 off}And V_{2 off}The selection of (1) satisfies the following conditions: ions in the ionization region can be prevented from passing through the ion gate into the mobility region,If the ion ionization region is kept in the door-closing stage, after a sufficient time (more than 1 second), the ions passing through the ion gate from the ionization region into the migration region impact the absolute value | I of the current generated on the detector_{Closing device}|≤0.9*|I_{Opening device}L. In general, | Δ V_{Closing device}I > 50; in the door closing stage, a voltage gradient in a direction different from the migration direction of the ions is formed, and the ions in the ion gate region are prevented from entering the migration region.

Preferably, - (d × | E)_d|)≤ΔV_{opening device}Less than or equal to 0, wherein d is the distance between the first grid electrode G1 and the second grid electrode G2, E_dIs the migration electric field intensity;

Preferably-1000. ltoreq. DELTA.V_ScissorsMinus 50, more preferably minus 600. ltoreq. DELTA.V_Scissors≤-200。

Preferably, 50 ≦ Δ V_{Push away}1000 or less, more preferably 200 or less Δ V_{Push away}≤600。

Preferably, 50 ≦ Δ V_{Closing device}1000 or less, more preferably 80 or less Δ V_{Closing device}≤400。

Alternatively, V_{1 scissor}＝V_{1 on}。

Alternatively, V_{1 push away}＝V_{1 on}。

Alternatively, V_{1 off}＝V_{1 on}。

Alternatively, V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}。

Alternatively, V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}＝V_2-opening。

Optionally, the voltage of the first grid electrode G1 is the same in the repulsion phase and the door-closing phase, V_{1 push away}＝V_{1 off}。V_{1 push away}、V_{1 off}Should be selected to satisfy the voltage selection condition in the repulsion stage and the door-closing stage. This can combine the repulsion stage and the door closing stage of the first grid electrode into one and further simplify the control sequence.

Optionally, the voltage of the second grid electrode G2 is the same in the repulsion phase and the door-closing phase, V_{2 push away}＝V_{2 off}。V_{2 push away}、V_{2 off}Should be selected to satisfy the voltage selection condition in the repulsion stage and the door-closing stage. This can combine the repulsion stage and the door closing stage of the second grid electrode into one and further simplify the control sequence.

In a preferred embodiment, the repulsion phase and the door-closing phase are at the same voltage, i.e. V_{1 push away}＝V_{1 off}And V is_{2 push away}＝V_{2 off}；V_{1 push away}、V_{2 push away}、V_{1 off}、V_{2 off}The voltage selection conditions of the repulsion stage and the door closing stage are simultaneously met; v_{1 on}＝V_{1 scissor}＝V_{1 off}＝V_2-openingAnd-1000. ltoreq. DELTA.V_ScissorsΔ V of ≦ 50, more preferably-600 ≦ Δ V_ScissorsLess than or equal to-200, and less than or equal to 50 delta V_{Closing device}1000 or less, more preferably 80 or less,. DELTA.V_{Closing device}≤400。

In a specific embodiment, the shape of the first grid electrode G1 and the second grid electrode G2 may be one or a combination of two or more of a mesh electrode, a concentric ring electrode, a grid electrode, and a spiral electrode.

Application example 1

Parameters and conditions of the ion mobility spectrometer: the length of the migration tube is 10.5cm, and the migration electric field intensity is 50V/mm; the detection sample is acetone with the concentration of 10 ppm; the flow rate of the carrier gas is 10ml/min, and the flow rate of the drift gas is 600 ml/min; the first grid electrode G1 and the second grid electrode G2 are respectively composed of a group of metal wire meshes which are parallel to each other and have equal distance, and the distance between every two adjacent metal wires is 2 mm; the wire diameters of the first grid electrode G1 and the second grid electrode G2 are both 0.1 mm; the first grid electrode G1 and the second grid electrode G2 are coplanar and the distance between adjacent wires is 1 mm. In this example, the ion mobility spectrometer operates in a positive polarity mode.

The method of the invention is adopted to carry out the back edge shaping of the ion cluster, the timing diagrams of the first grid electrode G1 and the second grid electrode G2 are shown in FIG. 2, and the specific parameters are as follows:

The voltages of the first grid electrode G1 and the second grid electrode G2 at each stage satisfy the following conditions, and the units are all volts (V):

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}＝V_2-opening；

V_{2 scissor}＝V_2-opening-400；

V_{2 push away}＝V_2-opening+300；

V_{2 off}＝V_2-opening+100；

Duration of shear phase τ_Scissors＝18μs；

Duration of repulsion phase_{push away}＝30μs。

Application example 2

Parameters and conditions of the ion mobility spectrometer: the length of the migration tube is 10.5cm, and the migration electric field intensity is 50V/mm; the detection sample is acetone with the concentration of 10 ppm; the flow rate of the carrier gas is 10ml/min, and the flow rate of the drift gas is 600 ml/min; the first grid electrode G1 and the second grid electrode G2 are respectively composed of a group of metal wire meshes which are parallel to each other and have equal distance, and the distance between every two adjacent metal wires is 2 mm; the wire diameters of the first grid electrode G1 and the second grid electrode G2 are both 0.1 mm; the first grid electrode G1 and the second grid electrode G2 are coplanar and the distance between adjacent wires is 1 mm. In this example, the ion mobility spectrometer operates in a positive polarity mode.

The method of the invention is adopted to carry out the back edge shaping of the ion cluster, the timing diagrams of the first grid electrode G1 and the second grid electrode G2 are shown in FIG. 3, and the specific parameters are as follows:

The voltages of the first grid electrode G1 and the second grid electrode G2 at each stage satisfy the following conditions, and the units are all volts (V):

V_{1 on}＝V_{1 scissor}＝V_{1 push away}＝V_{1 off}＝V_2-opening；

V_{2 scissor}＝V_2-opening-400；

V_{2 push away}＝V_{2 off}＝V_2-opening+100；

Duration of shear phase τ_Scissors＝18μs。

The experiment shows that before the shaping, the half-peak width of a spectrogram is 153.4 mu s, and the resolution is 64.5; after shaping, the half-width of the spectrum was 101.7. mu.s, with a resolution of 100. Therefore, the method can improve the deformation of the back edge of the ion cluster, inhibit the broadening of the ion cluster and further improve the resolution of a spectrogram.

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. In the description herein, references to the description of the term "one embodiment," "some embodiments," "preferred embodiments," "an example," "a specific example," or "some examples" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. One of ordinary skill in the art will readily appreciate that the above-disclosed, presently existing or later to be developed, processes, machines, manufacture, compositions of matter, means, methods, or steps, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.