阅读说明：本技术 一种施加在bn型离子门上的脉冲电压波形 (Pulse voltage waveform applied to BN type ion gate ) 是由 仓怀文 王卫国 黄卫 李京华 张远智 李海洋 于 2021-07-01 设计创作，主要内容包括：本发明公开了一种施加在BN型离子门上的脉冲电压波形,是施加在BN型离子门上第一组金属电极和第二组金属电极上,周期性控制离子门的工作状态经过六个阶段的电压波形。与传统的电压波形相比,离子门在已处于关闭状态后再次将离子门两组金属电极电压的切换,通过改变离子门关门电场,实现打破离子门旧三区建立新三区的效果,可以进一步减少清空区引起的离子损失,压缩扩散区和压缩区中离子,离子团后沿浓度分布变密,提升离子迁移谱灵敏度和分辨率,消弱BN型离子门的迁移率歧视。(The invention discloses a pulse voltage waveform applied to a BN type ion gate, which is a voltage waveform applied to a first group of metal electrodes and a second group of metal electrodes on the BN type ion gate and periodically controlling the working state of the ion gate to pass through six stages. Compared with the traditional voltage waveform, the ion gate switches the two groups of metal electrode voltages of the ion gate again after being in a closed state, and the effect of breaking the old three regions of the ion gate and establishing a new three regions is realized by changing the gate-closing electric field of the ion gate, so that the ion loss caused by the emptying region can be further reduced, ions in the diffusion region and the compression region are compressed, the concentration distribution of the ions at the back edge becomes dense, the sensitivity and the resolution of an ion mobility spectrum are improved, and the mobility discrimination of the BN type ion gate is weakened.)

1. A pulsed voltage waveform applied to a BN-type ion gate, said BN-type ion gate comprising two sets of parallel, insulated first and second sets of metal electrodes sequentially spaced apart in a plane, wherein: the pulse voltage waveform is respectively applied to the first group of metal electrodes and the second group of metal electrodes, and the working state of the ion gate is periodically controlled to pass through the following six stages:

applying a first high voltage to the first group of metal electrodes and a second high voltage to the second group of metal electrodes within a first preset time interval, wherein t is less than t1, the second high voltage is higher than the first high voltage, the ion gate is in a closed state, and the ion gate is in a preparation state before being in a door opening state;

in a second preset time interval, namely t1 < t2, applying a constant voltage to the first group of metal electrodes, applying a first high voltage to the second group of metal electrodes, applying the same voltage to the first group of metal electrodes and the second group of metal electrodes, and enabling the ion gate to be in a door-opening state;

in a third preset time interval, namely t2 < t3, applying a constant voltage to the first group of metal electrodes, applying a second high voltage to the second group of metal electrodes, wherein the voltage applied to the second group of metal electrodes is higher than that applied to the first group of metal electrodes, and the ion gate is in a gate-closed state;

during a fourth preset time interval, namely t3 < t4, applying a second high voltage on the first group of metal electrodes, applying a first high voltage on the second group of metal electrodes, wherein the voltage applied on the first group of metal electrodes is higher than that applied on the second group of metal electrodes, and the ion gate is also in a gate-closing state;

in a fifth preset time interval, namely t4 < t5, applying a first high voltage to the first group of metal electrodes, applying a constant voltage to the second group of metal electrodes, applying the same voltage to the first group of metal electrodes and the second group of metal electrodes, and enabling the ion gate to be in a door-opening state again;

and in a sixth preset time interval, namely t5 < t6, applying a second high voltage to the first group of metal electrodes, applying a voltage to the second group of metal electrodes unchanged, applying a higher voltage to the first group of metal electrodes than to the second group of metal electrodes, and enabling the ion gate to be in a door-closing state again.

2. The pulsed voltage waveform of claim 1, wherein: the sum of the times of the second preset time interval, the third preset time interval and the fourth preset time interval is a primary switching period of the ion mobility spectrometry.

3. The pulsed voltage waveform of claim 1, wherein: and the third preset time interval is the same as the sixth preset time interval, and is switching delay time after the ion door is closed.

4. The pulsed voltage waveform of claim 1, wherein: and the second preset time interval is the same as the fifth preset time interval, is the opening time of the ion gate, and operates the ion implantation.

5. The pulsed voltage waveform of claim 1, wherein: the second and fifth preset time intervals are the opening time of the ion gate, so that ions can smoothly pass through the ion gate and are usually set between 1 and 500 us; the third and sixth preset time intervals are the closing state of the ion gate or the delay time of voltage interchange of two groups of metal electrodes of the ion gate after the ion gate is closed, so that most of ions pass through a clearance zone behind the ion gate and are usually arranged between 1 and 100 us; the first and fourth preset time intervals are the voltage interchange time of two groups of metal electrodes of the ion gate after the gate is closed and are kept until the next gate opening period.

6. The pulsed voltage waveform of claim 1, wherein: the first high voltage is a reference voltage of a position of the ion gate.

7. The pulsed voltage waveform of claim 1, wherein: the second high voltage and the first high voltage are high and low of the absolute value of the voltage.

8. The pulsed voltage waveform of claim 1, wherein: the difference between the second high pressure value and the first high pressure value is generally 10v-600v by taking the first high pressure as a reference.

9. A BN-type ion gate controlled with a pulsed voltage waveform as claimed in any one of claims 1 to 8.

10. An ion mobility spectrometry employing an ion gate as claimed in claim 9.

Technical Field

The invention belongs to the field of ion mobility spectrometry, and particularly relates to a pulse voltage waveform of an ion mobility spectrometry applied to a BN type ion gate.

Background

An Ion Gate (Ion Gate or Ion shutter) is a device which relies on an electric field to generate a pulse Ion cluster, and is one of the key components of a migration time Ion mobility spectrum, and the thickness, density and shape of the chopped Ion cluster influence the resolution capability and sensitivity of the mobility spectrum to a great extent. The ion gate developed more mature at present is Bradbury-Nielsen type ion gate (BNG), Tyndall-Powell type ion gate (TPG) and the like. The BN type ion gate is composed of two groups of parallel and insulated metal electrodes, which are usually very thin metal wires, arranged on a plane at intervals in sequence. Its working state has two general: a door open state and a door closed state. In the door-open state, the two groups of electrodes have the same potential and do not prevent the movement of ions. In the door-closing state, a door-closing voltage is superposed on one group of metal electrodes, or opposite door-closing voltages are superposed on the two metal electrodes, so that a potential difference is generated between the two groups of metal electrodes, and a door-closing electric field perpendicular to the ion migration direction is formed between the adjacent electrodes, so that ions reaching the ion gate are all neutralized. Its advantages are high universality, no requirement to ionizing source, wide application to all migration tubes, low potential difference for closing door, simple control circuit and wide application to commercialized ion migration spectrum. BNG has the disadvantage of relatively complex structure, and also introduces a vertical door-closing electric field that distorts the electric field in the vicinity of the ion gate, and the higher the door-closing voltage, the more severe the field distortion. Electric field distortion can cause ion cluster deformation and mobility discrimination, and is not beneficial to improving the performance of ion mobility spectrometry.

In the development of the migration tube, the ion gate chopping ion flow behavior and the gate-closing electric field characteristics are deeply understood. Among them, studies by duyongzhai et al typically show that if a positive gate-closing voltage pulse is applied to a BNG in positive ion mode, the gate-closing voltage will enhance the electric field strength behind the BNG, thereby generating a time compression effect on the implanted ion packet, and increasing the intensity of the gate-closing voltage will enhance the compression effect, thereby improving the resolution of the ion mobility spectrometry. For this reason, in patents CN110310882A and CN110534395A, it is proposed to simultaneously raise the gate-closing voltages of two sets of electrodes on the ion gate when the ion gate is closed, so as to form a high electric field region behind the ion gate, and further compress the ions. Specifically, patent CN110310882A discloses that when the ion gate is closed, the potential of the two metal electrodes of the ion gate is increased under the condition that the voltage for closing the ion gate is not changed, so as to enhance the effect of ion compression when the ion gate is closed. After a period of time, the voltage of the two metal electrodes of the ion gate still needs to return to the normal voltage level, the potential of the ion gate electrode is improved, the distortion of a migration electric field is serious, and the ion mobility spectrometry performance is not facilitated. Patent CN110534395A is to reduce the discriminative effect of the ion gate, and the voltage waveform after the gate is closed is the same as that of patent CN110310882A, in which the voltage of the low voltage electrode is lowered before the opening of the ion gate to increase the ion injection amount. The voltage waveform has a complex time sequence, the potential of the ion gate electrode is continuously raised and lowered, the complexity of the ion gate control circuit is increased, and particularly, the control circuit is more complex under positive and negative working modes.

With further understanding of the ion gate regulation technology, the invention provides a new ion gate regulation mode, which is called as single switching pulse waveform, and can reduce ion loss caused by a clearance area, compress ions in a diffusion area and a compression area, and make concentration distribution of ion clusters back edge become dense, so that sensitivity and resolution are improved.

Disclosure of Invention

The main objective of the present invention is to overcome the deficiencies of the prior art and to provide a voltage waveform applied to a BN gate to improve the ion mobility spectrometry performance, so as to improve the sensitivity and resolution and reduce the resolution discrimination effect.

The technical scheme of the invention is as follows:

in one aspect, the present invention provides a pulse voltage waveform applied to a BN type ion gate, where the BN type ion gate includes two groups of parallel and insulated first and second groups of metal electrodes arranged on a plane at intervals in sequence, and the pulse voltage waveform can be applied to the first and second groups of metal electrodes, respectively, and periodically controls the operating state of the ion gate through the following six stages.

And applying a first high voltage (HV1) to the first group of metal electrodes and applying a second high voltage (HV2) to the second group of metal electrodes within a first preset time interval (t < t1), wherein the second high voltage is higher than the first high voltage, the ion gate is in a closed state, and the ion gate is in a preparation state before a door opening state.

And in a second preset time interval (t1 < t2), the voltage is applied to the first group of metal electrodes unchanged, the first high voltage is applied to the second group of metal electrodes, the same voltage is applied to the first group of metal electrodes and the second group of metal electrodes, and the ion gate is in a door-opening state.

And in a third preset time interval (t2 < t3), the voltages are applied to the first group of metal electrodes unchanged, the second group of metal electrodes are applied with a second high voltage, the voltages applied to the second group of metal electrodes are higher than the voltages applied to the first group of metal electrodes, and the ion gate is in a gate-closed state.

And in a fourth preset time interval (t3 < t4), applying a second high voltage to the first group of metal electrodes, applying a first high voltage to the second group of metal electrodes, wherein the voltage applied to the first group of metal electrodes is higher than that applied to the second group of metal electrodes, and the ion gate is also in a door-closing state.

And in a fifth preset time interval (t4 < t5), a first high voltage is applied to the first group of metal electrodes, a voltage is applied to the second group of metal electrodes unchanged, the same voltage is applied to the first group of metal electrodes and the second group of metal electrodes, and the ion gate is in a door-opening state again.

And in a sixth preset time interval (t5 < t6), applying a second high voltage to the first group of metal electrodes, applying a constant voltage to the second group of metal electrodes, applying a higher voltage to the first group of metal electrodes than to the second group of metal electrodes, and enabling the ion gate to be in a door-closing state again.

The sum of the times of the second preset time interval, the third preset time interval and the fourth preset time interval is a primary switching period of the ion mobility spectrometry.

And the third preset time interval is the same as the sixth preset time interval, and is switching delay time after the ion door is closed.

And the second preset time interval is the same as the fifth preset time interval, is the opening time of the ion gate, and operates the ion implantation.

The second and fifth preset time intervals are the opening time of the ion gate, so that ions can smoothly pass through the ion gate and are usually set between 1 and 500 us; the third and sixth preset time intervals are the closing state of the ion gate or the delay time of voltage interchange of two groups of metal electrodes of the ion gate after the ion gate is closed, so that most of ions pass through a clearance zone behind the ion gate and are usually arranged between 1 and 100 us; the first and fourth preset time intervals are the voltage interchange time of two groups of metal electrodes of the ion gate after the gate is closed and are kept until the next gate opening period.

The first high voltage is a reference voltage of a position of the ion gate.

The second high voltage and the first high voltage are high and low of the absolute value of the voltage. The second high pressure value is greater than or equal to the second high pressure value in the traditional mode, and preferably the second high pressure value is greater than the second high pressure value in the traditional mode; the difference between the second high pressure value and the first high pressure value is generally 10v-600v when the first high pressure is taken as a reference.

In another aspect, the present invention protects a BN-type ion gate controlled with the pulsed voltage waveform described above.

In yet another aspect, the invention protects ion mobility spectrometry employing the ion gate described above.

Advantageous effects

According to the pulse voltage waveform applied to the BN type ion gate, after the switching delay time of the closing state of the ion gate, the voltage of the first metal electrode is switched to the voltage of the second metal electrode, and meanwhile, the voltage of the second metal electrode is switched to the voltage of the first metal electrode, so that three regions (a clearance region, a diffusion region and a compression region) of the ion gate formed immediately after the ion gate is closed are reestablished to be new three regions, the loss of ion clusters behind the ion gate can be reduced to a certain extent, ions are compressed, and the ion density is improved. After the voltages of the two metal electrodes of the ion gate are switched, a new change is generated in the gate closing electric field of the ion gate, and a part of ion clusters originally flying to the low-voltage metal electrode, namely ion clusters in the clearance area, can be repulsed and compressed into the migration area again, so that the secondary compression of the ion clusters is realized, the injection efficiency and the resolution of the ion gate are improved, and the mobility discrimination effect of the BN type ion gate is weakened.

The ion gate regulation and control method provided by the invention realizes the change of the electric field of the ion gate by utilizing the switching pulse waveform, achieves the purpose of influencing the ion motion of the back edge of the ion cluster after the door is closed, and reduces the ion loss, compresses ions for the second time, trims the concentration distribution of the back edge of the ion cluster and improves the ion mobility spectrometry performance by controlling the electrode voltage of the BN type ion gate to periodically change along with the time in six stages.

The voltage waveform adopted by the invention is not changed in the total vertical electric field intensity of the ion gate after the voltage of the electrode of the ion gate is exchanged, the torsion degree of a migration electric field is not increased, and the ion mobility spectrometry performance is facilitated.

Drawings

Fig. 1 is a timing diagram of a conventional voltage waveform applied to a BN-type ion gate.

Fig. 2 is a timing diagram of waveforms of the pulse voltage applied to the BN type ion gate of the present invention.

Fig. 3 shows an ion mobility spectrum of a sample measured using a conventional voltage waveform.

FIG. 4 shows an ion mobility spectrum of a sample measured using the voltage waveform of 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.

Fig. 1 shows the operation of a conventional BN-type ion gate, which generally includes two parts: a door open state and a door closed state. In the door-open state (t1 < t2), the two groups of metal electrodes of the ion gate have the same potential and do not prevent the movement of ions. In the door-closed state (t2 < t3), a door-closing voltage is superposed on one group of metal electrodes, or opposite door-closing voltages are superposed on the two metal electrodes, so that a potential difference is generated between the two groups of metal electrodes, a door-closing electric field perpendicular to the ion migration direction is formed between the adjacent electrodes, ions reaching the ion gate are neutralized, and the ions cannot pass through the ion gate.

As shown in fig. 2, a pulse voltage waveform applied to a BN type ion gate, said BN type ion gate is a general type ion gate, and includes two groups of parallel and insulated first group metal electrodes grid1 and second group metal electrodes grid2, which are sequentially arranged on a plane at intervals, said pulse voltage waveform can be applied to the first group metal electrodes grid1 and the second group metal electrodes grid2, respectively, and the working state of the ion gate is periodically controlled through the following six time stages:

within a first preset time interval (t < t1), a first high voltage HV1 is applied to the first group of metal electrodes grid1, a second high voltage HV2 is applied to the second group of metal electrodes grid2, the second high voltage HV2 is higher than the first high voltage HV1, the ion gate is in a closed state, and ions cannot pass through the ion gate. The voltage interchange states of the first group of metal electrodes grid1 and the second group of metal electrodes grid1 in the time interval are switching pulse processes.

In a second preset time interval (t1 < t2), the voltage is applied to the first group of metal electrodes grid1 unchanged, the first high voltage HV1 is applied to the second group of metal electrodes grid2, the same voltage is applied to the first group of metal electrodes grid1 and the second group of metal electrodes grid2, the ion gate is in a door-open state, ions can smoothly pass through the ion gate, and ion injection is achieved.

In a third preset time interval (t2 < t3), the voltage is applied to the first group of metal electrodes grid1 unchanged, the second group of metal electrodes grid2 is applied with a second high voltage HV2, the voltage applied to the second group of metal electrodes grid2 is higher than the voltage applied to the first group of metal electrodes grid1, and the ion gate is in a gate-closed state. And after the ion injection is finished, closing the ion gate, wherein the period of time is the switching delay time after the ion gate is closed.

In a fourth preset time interval (t3 < t4), a second high voltage HV2 is applied to the first group of metal electrodes grid1, a first high voltage HV1 is applied to the second group of metal electrodes grid2, the voltage applied to the first group of metal electrodes grid1 is higher than the voltage applied to the second group of metal electrodes grid2, the voltages of the two groups of electrodes on the ion gate are exchanged, the process of breaking the old three regions and establishing new three regions is achieved, and the pulse switching process is achieved. Although the voltage is switched, the ion gate is always closed during this time.

The second preset time interval, the third preset time interval and the fourth preset time interval are collectively called a primary switching period of the ion mobility spectrometry if the opening state of the ion gate is taken as a starting point.

In a fifth preset time interval (t4 < t5), a first high voltage HV1 is applied to the first group of metal electrodes grid1, a voltage is applied to the second group of metal electrodes grid2 unchanged, the same voltage is applied to the first group of metal electrodes grid and the second group of metal electrodes grid1, and the ion gate is in a door-open state again. The ions can pass through the ion gate again, and the next switching period of the ion mobility spectrometry is started.

In a sixth preset time interval (t5 < t6), a second high voltage HV2 is applied to the first group of metal electrodes grid1, a voltage is applied to the second group of metal electrodes grid2 unchanged, a voltage applied to the first group of metal electrodes grid1 is higher than a voltage applied to the second group of metal electrodes grid1, and the ion gate is in a door-closing state again.

The fifth preset time interval, the sixth preset time interval and the first preset time interval are the next switching period of the ion mobility spectrometry.

The switching pulse waveform time sequence periodically passes through six time stages, and an ion gate of the ion mobility spectrometry is controlled to pass through a switching period once, so that the periodic injection of ion clusters is realized. The voltage levels of the first high voltage HV1 and the second high voltage HV2 are absolute values. The pulse voltage waveform is suitable for a positive high-voltage mode and a negative high-voltage mode of the ion mobility spectrometry.

The first high voltage HV1 is a reference voltage for the location of the ion gate, preferably some suitable potential between the mobility and reaction regions on the mobility tube.

When the BN type ion gate applies the ion cluster chopped by the traditional voltage waveform. The ion gate chopped ion concentration distribution is not rectangular. When the door is closed, the ion packet front penetrating the ion gate is not flush but exhibits a peak-like protrusion due to the compression and repulsion of the high voltage metal electrode. Under the influence of the low-voltage metal electrode emptying area and the diffusion area, the back edge of the ion cluster drags a long tail in a wave-shaped distribution, and the distribution shape of the ion cluster is not beneficial to the performance of the ion mobility spectrometry. The distribution shape of the ion cluster chopped by applying the pulse voltage waveform of the invention on the BN type ion gate is obviously improved. Particularly, when the door is closed, after a certain delay time (a third preset time interval and a sixth preset time interval), the potentials of two adjacent electrodes of the ion gate are rapidly switched, a new change is generated in the door closing electric field of the ion gate, a part of ions originally positioned in the clear area are rapidly away from the electrodes under the action of the new potential, more ions are pushed into the migration area, and after the ion clusters are compressed twice, the ion cluster concentration is further enhanced, so that the resolution and the ion utilization rate are improved, and the mobility discrimination effect of the BN type ion gate is weakened.

Example 1

The pulse voltage waveform of a specific embodiment is used for measuring a DMMP sample with a 10ppb concentration, and comprises the following steps of setting a migration electric field to be 400V/cm, setting the door opening time of an ion gate to be 100us, setting the switching period of the ion gate to be 20.1ms, setting a reference voltage at the ion gate to be 1600V, and setting the door closing voltage to be 250V, namely HV1 to 1600V and HV2 to 1850V:

the first step, t < t1 ═ 0us, the BN gate is in the door closing state, the transition tube is in the preparation state for ion implantation, the voltage of the first metal electrode grid1 is set as the reference voltage HV1 of the transition tube, and the voltage of the second metal electrode grid2 is set as HV 2;

secondly, t1 is 0us < t2 is 100us, the BN door is in a first door opening state, ion clusters are implanted, and the voltages of the first metal electrode grid1 and the second metal electrode grid2 are set to be HV 1;

thirdly, setting the voltage of the first metal electrode grid1 as the reference voltage HV1 of the migration tube, and setting the voltage of the second metal electrode grid2 as HV2, wherein t2 is 100us < t3 is 130us, the BN gate is in a first door closing state, and the ion clusters are cut off;

fourthly, t3 is 130us < t4 is 20100us, the BN door is still in a door closing state, but the voltage of an ion door electrode is switched to repel and compress ion clusters, the voltage of a first metal electrode grid1 is set as the reference voltage HV2 of the migration tube, and the voltage of a second metal electrode grid2 is set as HV 1;

fifthly, t4 is 20100us < t5 is 20200us, the BN gate is in a second time of opening the gate, next ion clusters are injected, the voltage of the first metal electrode grid1 is set as the reference voltage HV1 of the migration tube, and the voltage of the second metal electrode grid2 is set as HV 2;

sixthly, 20200us < t6 us 20230us for t5, the BN door is in a second door closing state, ion clusters are cut off, the voltage of the first metal electrode grid1 is set as the reference voltage HV2 of the migration tube, and the voltage of the second metal electrode grid2 is set as HV 1; and then returning to the first step preparation state, and switching the voltage of the ion gate electrode to repel and compress ion clusters.

Comparative example 1

Setting a migration electric field to be 400V/cm, setting the door opening time of an ion gate to be 100us, setting the switching period of the ion gate to be 20.1ms, setting a reference voltage at the ion gate to be 1600V, setting the door closing voltage to be 250V, namely HV 1-1600V, HV 2-1850V, and actually measuring a DMMP sample with 10ppb concentration by adopting a traditional voltage waveform, wherein the DMMP sample comprises the following steps:

the first step, t < t1 ═ 0us, the BN gate is in the door closing state, the transition tube is in the preparation state for ion implantation, the voltage of the first metal electrode grid1 is set as the reference voltage HV1 of the transition tube, and the voltage of the second metal electrode grid2 is set as HV 2;

secondly, t1 is 0us < t2 is 100us, the BN door is in a door-opening state, ion clusters are implanted, and the voltages of the first metal electrode grid1 and the second metal electrode grid2 are set to be HV 1;

thirdly, when the BN door is in a door closing state, the ion cluster is cut off, the voltage of a first metal electrode grid1 is set to be the reference voltage HV1 of the migration tube, and the voltage of a second metal electrode grid2 is set to be HV2, wherein t2 is 100us < t3 is 20100 us;

and continuously circulating the above three steps to realize the periodic ion implantation into the ion migration tube. However, the ion clusters chopped by the voltage waveform are influenced by the low-voltage metal electrode clearance area and the diffusion area and are distributed in a wave shape, so that the resolution and the sensitivity of ions are limited, and the ion mobility spectrometry performance is not facilitated.

To demonstrate the effect of applying a pulsed voltage waveform, a DMMP sample at a concentration of 10ppb was measured and an ion mobility spectrum was obtained, as shown in fig. 3 and 4, in comparison with a conventional voltage waveform. It can be seen that not only the DMMP signal strength is improved, but also the RIP signal strength is improved. The signal intensity of RIP, DMMP monomer and DMMP dimer is respectively improved by 56%, 66% and 100%, and the resolution of RIP peak and DMMP monomer is respectively improved by 11% and 10%.

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.