CN102903598B - Method for improving traditional ion transference tube sensitivity - Google Patents

Abstract

The invention discloses a method for improving the sensitivity of a traditional ion transfer tube. Firstly, the voltage V1 of the ionization region, the voltage V2 of the first ion gate and the voltage V3 of the second ion gate of the ion transfer tube when the ion gate is closed Satisfy the following formula: V1=V3>V2>>0, at the moment of opening the gate, a pulse with the same polarity as the original voltage and an amplitude of ΔV1 is applied to the voltage V1 in the ionization region, and a pulse is also applied to the voltage V2 of the first ion gate The pulse with the same polarity as the original voltage and the amplitude of ΔV makes: (V1+ΔV1)>>(V2+ΔV)>V3>>0, so when the door is closed, the ions accumulated in the ionization region, under the force of the electric field Under the action, it instantly enters the migration area for migration. Using this method, the ion utilization rate of the ion transfer tube with the traditional structure can be increased by more than 5 times, and the limit detection sensitivity of common samples can be increased by 5 to 10 times, which greatly improves the sensitivity performance index of the instrument.

Description

A Method for Improving the Sensitivity of Conventional Ion Transfer Tubes

technical field

The invention relates to an ion transfer tube, in particular to a method for improving the sensitivity of the ion transfer tube

Background technique

Ion mobility spectrometry (IMS) appeared in the late 1960s, and after decades of development, it has become a relatively mature on-site trace detection technology based on the molecular level. The core component of the ion mobility spectrometer is the ion transfer tube. In the ion transfer tube, the sample molecules can generate corresponding product ions under the action of the ionization source. When these product ions are placed in a constant electric field in the atmospheric environment, they are accelerated by the electric field and decelerated by the collision of neutral atmospheric molecules, and they appear to obtain a constant average velocity macroscopically. Since different product ions have different charge-to-mass ratios, spatial geometric configurations, and collision cross-sections, the average velocities obtained are also different. Therefore, they are separated after passing through an electric field, and arrive at the detector successively to complete the detection process.

The structure of a traditional ion transfer tube is shown in Figure 1: it is mainly composed of an ionization region 1, a migration region 2, and a detector 3. The ionization zone 1 is set at the beginning of the migration zone 2 , and an ion gate 4 is set between them; the detector 3 is set at the end of the migration zone 2 .

As shown in FIG. 1 and FIG. 2 , the ion gate 4 in the ion transfer tube generally consists of two metal gates 41 that are close to each other, and the two metal gates are insulated from each other.

The working mode of the traditional ion transfer tube is described as follows: the particles of the sample to be tested enter the ionization region, and under the action of the ionization source (usually ⁶³ Ni), a relatively stable product ions. The product ions are controlled by the ion gate and enter the migration area in batches for migration at the same time. After a period of electric field, they are separated and arrive at the collector successively to form weak pulse electric signals, thus completing the process of being detected.

In Figure 1, Vi is the ionization region voltage, Vg is the voltage of the first ion gate, Vd is the voltage of the second ion gate, and the second ion gate voltage is the initial terminal voltage of the migration region ( That is, the highest voltage in the migration area), and at the same time, the voltage of each electrode on the migration area is obtained by dividing the voltage of the resistor, and the shell of the tube body and the collector are at zero potential. When the ion gate is closed, the electrode voltages are respectively |Vi|=V1, |Vg|=V2, |Vd|=V3, and the relationship between them is as follows:

V1>>V3>V2>>0

At the moment of opening the door, Vg will be applied with a pulse with the same polarity as the original voltage, and the amplitude is ΔV. At this time, the relationship is as follows:

V1>>(V2+ΔV)>V3>>0

Obviously, when the ion gate is closed, there is an electric field opposite to the direction of the electric field in the migration region between the two grids of the ion gate, and ions cannot pass through. At the moment of door opening, the reverse electric field is corrected and ions are allowed to pass through.

The above is the working method of the traditional ion transfer tube. The disadvantage is that the potential of Vi is much higher than that of Vg and Vd. Therefore, the ions generated in the ionization region also have a clear direction of movement, and the direction is from the ionization region to the ion gate. Direction movement, when the ion gate is closed, because the ions cannot cross the reverse electric field between the gate grids, most of the ions will hit the metal wire of the first gate grid and discharge, and the loss will become neutral ions, resulting in ion utilization efficiency The low, thus affecting the sensitivity index of the instrument.

Contents of the invention

The invention aims at the problem that the ion utilization rate is low due to the working mode of the traditional ion transfer tube, thereby affecting the sensitivity of the instrument, and provides a method for improving the sensitivity of the traditional ion transfer tube. This method effectively solves the problem of low ion utilization caused by the traditional ion transfer tube working mode without changing the structural design of the traditional ion transfer tube, and reduces the loss of ions in the ionization region when the ion gate is closed, thereby improving the sensitivity of the instrument.

In order to achieve the above object, the present invention adopts following technical scheme:

A method for increasing the sensitivity of conventional ion transfer tubes, in which

First, the voltage V1 of the ionization region, the voltage V2 of the first ion gate, and the voltage V3 of the second ion gate of the ion transfer tube satisfy the following formula when the ion gate is closed:

V1=V3>V2>>0,

Wherein, the magnitude of the reverse electric field between the voltage V3 of the second ion gate and the voltage V2 of the first ion gate is 7V-30V, and the second ion gate and the ionization region maintain the same potential, so that the ions generated in the ionization region able to reach full saturation;

At the moment of opening the gate, a pulse with the same polarity as the original voltage and an amplitude of ΔV1 is applied to the voltage V1 in the ionization region, and a pulse with the same polarity as the original voltage and an amplitude of ΔV is applied to the voltage V2 of the first ion gate. makes:

(V1+ΔV1)>>(V2+ΔV)>V3>>0,

Therefore, when the door is closed, the ions accumulated in the ionization area will instantly enter the migration area for migration under the action of the electric field force.

After the invention is adopted, the ion utilization rate of the ion transfer tube with the traditional structure can be increased by more than 5 times, and the limit detection sensitivity of common samples can be increased by 5 to 10 times, and the sensitivity performance index of the instrument can be greatly improved.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the structural representation of traditional ion transfer tube;

Fig. 2 is the schematic diagram of the structure of the electronic gate in the traditional ion transfer tube;

Fig. 3 is the connection schematic diagram of the ion transfer tube based on the implementation of the present invention;

Fig. 4 is a schematic diagram of the voltage distribution of each electrode in the ion transfer tube when the ion gate is closed;

Fig. 5 is a schematic diagram of the voltage distribution of each electrode in the ion transfer tube when the ion gate is opened.

Detailed ways

In order to make the technical means, creative features, goals and effects achieved by the present invention easy to understand, the present invention will be further described below in conjunction with specific illustrations.

Referring to Fig. 3, it shows the connection schematic diagram of the ion transfer tube based on the implementation of the present invention, as can be seen from the figure, the present invention does not change the structure of the traditional ion transfer tube, which also includes the ionization region 100, the transfer region 200, the detector 300, wherein the ionization region 100 is arranged at the initial end of the migration region 200, an ion gate 400 is arranged between the two, and the detector 300 is arranged at the end of the migration region 200; the ion gate 400 in the ion transfer tube is formed by the first metal ion The gate grid 401 and the second metal ion gate grid 402 are composed, and the two ion gate grids are close to each other and are insulated from each other. The specific structure is shown in FIG. 2 .

During implementation, a high-voltage power supply 500 is externally connected to the transition area 200 to provide a constant electric field in the transition area, and at the same time, the voltages of the electrodes in the transition area are obtained by dividing voltages by corresponding resistors. The voltage of the ionization region 100 is Vi, the voltage of the first ion gate 401 is Vg, the voltage of the second ion gate 402 is Vd, and the voltage of the second ion gate 402 is the initial terminal voltage of the migration region, that is, the migration The highest voltage in the area, the tube shell and the collector are at zero potential.

When the ion gate is closed, the electrode voltages are respectively |Vi|=V1, |Vg|=V2, |Vd|=V3, and the relationship between them is as follows:

V1=V3>V2>>0,

It can be seen from the above formula that when the ion gate is closed, the voltage V1 of the ionization region 100 is suppressed by the highest voltage in the migration region, that is, it is consistent with the voltage V3 of the second ion gate grid 402, and the voltage V3 of the second ion gate grid is the same as that of the first ion gate grid. The magnitude of the reverse electric field between the voltage V2 of the gate is between 7V and 30V, specifically 10V or 20V, and there is no significant potential difference with the voltage of the ionization region, that is, the second ion gate and the ionization region remain equal Potential, so that the ions generated in the ionization region can be fully saturated.

At the moment of opening the gate, the voltage Vi of the ionization region 100 will be applied with a pulse 600 with the same polarity as the original voltage (that is, the same polarity as the voltage Vi originally applied to the ionization region), with an amplitude of ΔV1, and the voltage of the first ion gate grid Vg will also be applied with a pulse 700 with the same polarity as the original voltage (that is, the same polarity as the voltage Vg of the first ion gate), with an amplitude of ΔV. At this time, the relationship between the voltages of the electrodes is as follows:

(V1+ΔV1)>>(V2+ΔV)>V3>>0,

The difference between (V1+ΔV1) and (V2+ΔV) is 200V-600V, the difference between (V2+ΔV) and V3 is 10V-30V, and V3 is 1300V-2500V.

At this time, the ions accumulated in the ionization region when the door is closed will instantly enter the migration region for migration under the action of the electric field force.

Compared with the gate-opening working mode of the above invention, in the traditional ion transfer tube working mode, when the ion gate is closed, the potential of V1 is much higher than that of V2 and V3 (the difference is 100V ~ 300V), so the ions generated in the ionization region also have obvious movement direction, and its direction is from the ionization region to the direction of the ion gate grid. At this time, because the ions cannot cross the reverse electric field between the gate grids, most of the ions will hit the metal wire of the first-level gate grid to discharge, and the loss becomes The loss rate of neutral ions is as high as more than 90%, resulting in low ion utilization efficiency, thereby affecting the sensitivity index of the instrument.

However, the present invention aims at this situation without changing the structural design of the traditional ion transfer tube, by changing the V1 potential when the ion gate is closed, so that the ions generated in the ionization region do not have a clear direction of movement at this time, reducing the loss of ions. This method can increase the ion utilization rate by more than 5 times, and the limit detection sensitivity of common samples can be increased by 5 to 10 times, and the sensitivity performance index of the instrument can be greatly improved.

Based on above-mentioned scheme, concrete implementation of the present invention is as follows:

Referring to FIG. 4 , a high-voltage power supply of 1500V is connected to the migration region 200 to provide a constant electric field in the migration region, and the voltage of each electrode is obtained by dividing voltage by resistors.

Wherein, the ionization region 100 remains consistent with the highest voltage in the migration region when the ion gate is closed, both being 1500V, the voltage of the first ion gate in the ionization region is 1490V, the voltage of the second ion gate is 1500V, and the detector is 0 potential. Thus, the ions generated in the ionization region can be fully saturated.

Referring to Fig. 5, when the gate is opened, a pulse of about 500V will be applied to the ionization region, and a pulse of about 15V will be applied to the first ion gate. At this time, the voltage of the ionization region is 2000V, the voltage of the first ion gate is 1505V, the voltage of the second ion gate is 1500V, and the detector is at 0 potential.

In this example, the door opening time is controlled between 200 and 400 microseconds, and then the door is closed. The ions accumulated in the ionization area when the door is closed, under the action of the electric field force, instantly enter the migration area for migration, greatly improving the utilization rate of ions , so that the limit detection sensitivity of common samples can be increased by 5 to 10 times, and the sensitivity performance index of the instrument can be greatly improved.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (1)

1. a method for improving the sensitivity of traditional ion transfer tubes, characterized in that, in the method First, the voltage V1 of the ionization region, the voltage V2 of the first ion gate, and the voltage V3 of the second ion gate of the ion transfer tube satisfy the following formula when the ion gate is closed: V1=V3>V2>>0, Wherein, the voltage V3 of the second ion gate is the initial terminal voltage of the migration region, that is, the highest voltage of the migration region, and the magnitude of the reverse electric field between it and the voltage V2 of the first ion gate is between 7V and 30V, And the second ion gate and the ionization region maintain the same potential, so that the ions generated in the ionization region can be fully saturated; At the moment of opening the gate, a pulse with the same polarity as the original voltage and an amplitude of ΔV1 is applied to the voltage V1 in the ionization region, and a pulse with the same polarity as the original voltage and an amplitude of ΔV is applied to the voltage V2 of the first ion gate. makes: (V1+ΔV1)>>(V2+ΔV)>V3>>0, Therefore, when the door is closed, the ions accumulated in the ionization area will instantly enter the migration area for migration under the action of the electric field force.