KR102334036B1 - Ion Mobility Spectrometer - Google Patents

Abstract

The present invention relates to an IMS movement conduit for an ion mobility spectroscope, and more specifically, to a voltage supply circuit which supplies a voltage to a movement conduit for moving an ion material for analyzing ionized materials. To this end, the ion mobility spectroscope according to the present invention comprises: a sampling part which inducts sample gas through an air intake part formed on a front surface; an ionization part connected to a rear end of the sampling part and ionizing the sample gas using corona discharge; a movement conduit connected to a rear end of the ionization part and generating an electric field to provide a movement path of the ionized sample gas; a gate grid and a shut grid installed inside a tip of the movement conduit to control the inflow of the ionized materials; and a collector installed at a rear end of the movement conduit and detecting a current generated according to the amount of charge when sample ions arrive, wherein the movement conduit is connected to the voltage supply circuit that receives a voltage. According to the present invention, the sample ions can be quickly discharged to the outside.

Description

IMS Mobility Spectrometer of Ion Mobility Spectrometer

The present invention relates to an IMS mobility conduit of an ion mobility spectrometer, and more particularly, to a voltage supply circuit for supplying a voltage to a mobility conduit for moving an ionized material in order to analyze the ionized material.

In general, Ion Mobility Spectrometer (IMS) detects the presence of harmful substances in the air, and is used for identification of narcotics, explosives, and hazardous chemicals.

In order to utilize ion mobility spectroscopy, a device or equipment for ionization of a substance is essential as a prerequisite for analysis in order to specify the chemical entity of a substance in a gas phase under electric field conditions. When a radioactive isotope is used, it is easy to form ions by continuously emitting high energy of about 20 keV, which is used for ionization of materials, without external power supply. It is a method of ionizing the sample gas by

1 is a cross-sectional structure of a conventional ion mobility spectrometer, including a sampling unit, an ionization unit, a mobility conduit, and a collecting unit. Referring to FIG. 1 described above, the sample gas sucked into the sampling unit 100 is ionized by the ionization source emitted from the radioactive isotope such as Ni-63 in the ionization unit 200 .

And the ionized sample is introduced into the inside of the mobile conduit 300 having an electric field formed therein in the longitudinal direction. In this case, the amount of ions introduced into the mobile conduit 300 is controlled by adjusting the opening time of the shutter grid 500 . As a result, the ions introduced into the movement conduit 300 move in the direction of the collection unit 400 with different movement speeds.

When the sample ions reach the collection unit 400, a minute current is generated according to the amount of charge of the sample ions, so the minute current generated by the importer 400 is amplified into a voltage form that can be checked through the amplifier, and the amplified analog signal is converted to ADC to check the reaction of the sample ions. Then, the detection current according to the movement time of the ions is spectralized, and the reduced mobility is calculated according to the conditions inside the equipment to detect and identify the analyte sample.

However, when using radioactive isotopes, considering the half-life, it can be used semi-permanently for 100 years and has the advantage of minimizing the equipment as it does not require a separate external power source. And there is a disadvantage that separate personnel and costs are required for management. In addition, about half of the high energy generated by the radioactive isotope is emitted toward the support and is not used for ionization, and only about 10% of the total high energy is used for ionization, so the ionization efficiency is extremely low. Due to these shortcomings, the development of measuring equipment for designing ionizers with radioactive isotopes is on the decline, and the design of ionizers through corona discharge is the main focus.

Korean Patent Registration No. 10-0971031 (Title of Invention: Ion Mobility Spectrometer) Korean Patent Registration No. 10-1578091 (Title of the invention: Noxious gas detection device using ion mobility sensor for generating negative ions)

The problem to be solved by the present invention is to propose a method of ionizing analysis using corona discharge.

Another problem to be solved by the present invention is to propose a method for accurately determining a component of an analysis gas.

Another problem to be solved by the present invention is to propose a configuration of a moving conduit for moving the ionized analyte gas.

Another problem to be solved by the present invention is to propose a distribution of a voltage supplied to a moving conduit to efficiently move an ionized analyte gas.

To this end, the ion mobility spectrometer of the present invention includes a sampling unit for sucking a sample gas through an air intake unit formed on the front surface; an ionizer connected to the rear end of the sampling unit to ionize the sample gas using corona discharge; a movement conduit connected to the rear end of the ionization unit and providing a movement path of the ionized sample gas by generating an electric field; a gate grid and a shutter grid installed inside the front end of the ion conduit to control the inflow of ionic substances; and a collector installed at the rear end of the mobile conduit to detect a current generated according to an amount of charge upon arrival of sample ions, wherein the mobile conduit is connected to a voltage supply circuit receiving a voltage.

The IMS mobility conduit of the ion mobility spectrometer according to the present invention is energized so that the ionized analyte gas moves to the intrinsic mass value of the material within the mobility conduit.

In addition, the resistance value of the resistor constituting the unit circuit that supplies the voltage to the mobile conduit located at the end is set high to minimize the field of the magnetic field in the flight distance of the sample ion, so that the ions that are incorrectly formed in the ionization process of the sample ion are excluded for analysis. Only the required sample ions reach the collector.

In addition, the region in which the collecting grid is located quickly discharges the sample ions to the outside in order to prevent the sample ions that collided with the collector from colliding with the collector again.

1 shows a cross-sectional structure of a conventional ion mobility spectrometer.
2 is an exploded perspective view illustrating an ion mobility spectrometer according to an embodiment of the present invention.
3 is a cross-sectional view of an ion mobility spectrometer according to an embodiment of the present invention.
Figure 4 shows the magnitude of the voltage supplied to the mobility conduit constituting the ion mobility spectrometer according to an embodiment of the present invention.
5 illustrates a circuit for supplying a voltage to a moving conduit constituting a mobile mobility spectrometer according to an embodiment of the present invention.

The foregoing and further aspects of the present invention will become more apparent through preferred embodiments described with reference to the accompanying drawings. Hereinafter, it will be described in detail so that those skilled in the art can easily understand and reproduce through these embodiments of the present invention.

Figure 2 is an exploded perspective view showing an ion mobility spectrometer according to an embodiment of the present invention, Figure 3 is a cross-sectional view of the ion mobility spectrometer according to an embodiment of the present invention.

2 to 3 , the ion mobility spectrometer includes a sampling unit, an ionization unit, a mobility conduit, a collector, and a purification unit. Of course, other configurations other than the above-described configuration may be included in the ion mobility spectrometer proposed in the present invention.

The sampling unit 1 is disposed at the frontmost end to suck the sample gas in the atmosphere, and the air suction unit 11 is formed on the front side, and is composed of a suction case 10 with an open rear side.

A main body housing 20 with an open front is connected to the rear surface of the suction case 10 , and an ionization unit 2 is formed at the inner tip of the main body housing 20 . At this time, the gas guide pipe 12 for guiding the sample gas sucked into the suction case 10 is connected to the ionization unit 2 .

The ionizer 2 has a plurality of electrode tips 21 spaced apart from each other and having a needle shape by corona discharge to ionize the sample gas flowing in through the gas guide tube 12 .

The detailed configuration of the ionization unit proposed in the present invention will be described later. At this time, each electrode tip 21 should maintain an interval that is optimized for the discharge voltage. According to this configuration, the ionizer 2 applies a voltage to the plurality of electrode tips 21 to corona-discharge the incoming sample gas to ionize it.

At this time, a suction fan 13 is installed inside the suction case 10 to smoothly suction the sample.

The ion conduit 3 provides a movement path for the ionized sample gas, and is installed behind the ionization unit 2 inside the body housing 20 . A carrier gas inlet 311 and a carrier gas outlet 312 are formed at the distal end of the moving conduit 3 . That is, in order to detect ion mobility, only the ionized sample gas should be introduced into the movement conduit 3, and the non-ionized sample gas should be discharged to the outside. Accordingly, the carrier gas is introduced into the carrier gas inlet 311 from the front end of the mobile conduit, and the non-ionized sample gas is discharged to the carrier gas exhaust port 312 together with the carrier gas.

At the rear end of the carrier gas inlet 311 of the moving conduit 3 , a gate grid 34 , a shutter grid 35 , and an aperture grid 36 are sequentially disposed, respectively. The gate grid 34 and the shutter grid 35 control ions flowing into the mobile conduit by using the applied voltage difference. That is, when the same voltage is applied to the gate grid 34 and the shutter grid 35 , or when the voltage applied to the gate grid 34 is higher than the voltage applied to the shutter grid 35 , the inflow of ions into the mobile conduit is is done On the other hand, when the voltage applied to the gate grid 34 is lower than the voltage applied to the shutter grid 35 , ions are not introduced into the mobile conduit. Accordingly, by making the voltages applied to the gate grid 34 and the shutter grid 35 different from each other, the inflow of ions into the mobile conduit 3 can be controlled.

The aperture grid 36 guides the purified air to the front end of the moving conduit 3 . That is, when there is no aperture grid 36 , a non-ionized sample penetrates into the movement conduit 3 to affect the analysis. Accordingly, by inducing the gas flow to the aperture grid 36 , the purified drift gas flows toward the front end of the moving conduit 3 , thereby preventing the inflow of non-ionized samples.

In addition, a printed circuit board (P) having a plurality of heater resistances for increasing the temperature inside the moving conduit may be attached to the outer circumferential surface of the moving conduit 3 .

On the other hand, the collector 4 is installed at the rear end of the moving conduit 3, and generates a unique current according to the amount of ion charge when the sample ions arrive. Although not shown in the drawing because the current generated at this time is weak, the generated current can be amplified using an amplifier and an ADC.

The purification unit 5 moves the purified air from the rear end to the front end of the moving conduit opposite to the movement direction of the ions. That is, by allowing purified air, whose purity is guaranteed by the injection body, to flow in the opposite direction of ion movement, it acts as a drift gas to collide with ionized molecules and assist separation.

Here, the purification unit 5 includes a purified air inlet 51 , a purified air exhaust port 52 , a circulation pump 53 , and a filtration unit 54 .

The purified air inlet 51 is formed so that the front end of the collector 4 passes through the ion source ring wall. And a first humidity sensor 55 is installed on the side of the purified air inlet 51 .

The purified air exhaust port 52 is formed so as to penetrate the front end of the moving conduit 3 , that is, the wall surface of the ion source ring disposed between the shutter grid 35 and the aperture grid 36 . And a second humidity sensor 56 is installed on the purified air exhaust port 52 side.

The circulation pump 53 supplies purified air to the purified air inlet 51 and discharges the purified air inside the moving conduit to the purified air exhaust port, so that a gas flow path is formed from the rear end to the front end of the moving conduit.

The filter unit 54 contains molecular sieve, and removes moisture contained in the drift gas exhausted through the purified air exhaust port. At this time, the molecular sieve preferably has a humidity of 0.5%RH or less in order to ensure that the relative humidity of the purified air is 15%RH or less. In addition, the purification unit 5 controls the supply of molecular sieves according to the detection results of the first humidity sensor 55 and the second humidity sensor 56 .

Hereinafter, the operation of the ion mobility spectrometer will be described.

First, an analysis sample in a vapor state is sucked into the air suction unit, and the sucked sample gas is ionized by corona discharge generated from the electrode tip.

Then, ions are introduced into the movement conduit by the voltage applied to the gate grid and the shutter grid. Here, in order to allow ions to flow into the mobile conduit, the same voltage is applied to the gate grid and the shutter grid, or a voltage higher than the voltage applied to the shutter grid is applied to the gate grid. Conversely, when blocking the flow of ions into the mobile conduit, a voltage lower than the voltage applied to the shutter grid is applied to the gate grid.

Here, the sample gas that is not ionized at the same time as the ions are introduced is discharged to the carrier gas outlet together with the carrier gas introduced into the carrier gas inlet.

The ions introduced into the mobile conduit move toward the collector by the magnetic field formed inside the mobile conduit. At this time, after forming a drift gas flow therein, it is discharged to the purification gas outlet. Accordingly, the inside of the moving conduit is low in humidity and impurities are removed.

Thereafter, the current generated by the ions arriving at the collector is amplified at a certain rate by the amplifier and ADC. Then, the detection current is spectralized according to the movement time of the ions, and the sample is analyzed by calculating according to the reduced mobility according to the conditions inside the equipment.

A measuring device using ion mobility spectroscopy (IMS) is a device that analyzes a sample according to the intrinsic mass of the material in a drift-region according to the electronic polarity of the material ionized in a magnetic field. To this end, a certain amount of material is collected through an arrangement according to the polarity of the ionized sample, and the signal strength is analyzed through separation according to the mass of the material in the drift tube to analyze and detect the name of the material.

As such, in order to analyze an ionized material in ion mobility spectroscopy, an ion gate for moving the material in the drift tube is an important factor. The ion gate is an important part of ion mobility spectroscopy (IMS), which allows ions to flock into the drift tube region. Currently, the most widely used method in ion mobility spectroscopy uses a Bradbury-Nielson type ion gate. The characteristic of the Bradbury-Nielson type ion gate is that it is constructed in a single planar shape and is designed to allow ions to pass through this planar structure. Structurally, it is a structure in which a small wire structure is produced in a plane on a single grid, and positive and negative voltages are applied to each wire to generate an orthogonal gate field.

The amount of ionization of the material to be measured is important for high-sensitivity analysis in material analysis, but the area where the loss of inhaled ionized material is minimized and delivered is also a very important part. A certain amount of material is collected through the gate grid, and through the adjustment of the voltage pulse of the gate grid and the ion shutter, the material moves to its own mass value in the drift tube, Analysis of the inhaled material in time will be performed.

4 shows the magnitude of the voltage supplied to the mobility conduit constituting the ion mobility spectrometer according to an embodiment of the present invention. Hereinafter, the magnitude of the voltage supplied to the mobility conduit constituting the ion mobility spectrometer according to an embodiment of the present invention will be described with reference to FIG. 4 . The movement of ions in the IMS conduit ionizes the material through the ionization source and causes the material to move to the intrinsic mass value of the material through the IMS conduit through which electricity flows.

According to FIG. 4 , the number of mobile conduits constituting the ion mobility spectrometer is 12, and the number of mobile conduits may be greater than or less than 12 depending on the size of the mobile conduit or the design intention of a designer.

The voltage supplied to the moving conduit shown in FIG. 4 is -1.8kV, -1.8kV, -1.34kV, -960V, -780V, -650V, -540V, -450V, -370V, -280V, - 190V and -110V. As shown in FIG. 4 , the magnitude of the absolute value of the voltage supplied to the moving conduit decreases from the front end to the rear end. The voltage shown in FIG. 4 is a measured voltage measured in the circuit shown in FIG. 5 and is different from the actual supply voltage. That is, there is a difference between the measured voltage measured by the measuring device and the actual supply voltage due to factors such as the internal resistance of the voltage measuring device.

5 shows a circuit for supplying a voltage to a moving conduit constituting a mobile mobility spectrometer according to an embodiment of the present invention. Hereinafter, a circuit for supplying a voltage to a mobile conduit constituting a mobility spectrometer according to an embodiment of the present invention will be described with reference to FIG. 5 .

The voltage supply circuit proposed in the present invention receives a high voltage of -1800V and applies an RC filter to supply a high voltage to each moving conduit. The RC parallel circuit structure reduces the high voltage at a certain rate, uses a high resistance to drop the voltage, and distributes the load applied to each element by applying a capacitor in parallel to reduce the current.

As described above, the circuit for supplying a voltage to the mobility conduit constituting the ion mobility spectrometer is connected in series with the parallel RC circuits.

That is, hereinafter, for convenience of description, RC circuits configured in parallel are referred to as unit circuits. That is, in the voltage supply circuit for supplying voltage to the moving conduit proposed in the present invention, a plurality of unit circuits are connected in series.

As shown in FIG. 5, the magnitude of the voltage supplied to the two moving conduits located at the front end is equal to -1.8 kV. Looking at this in detail, the two mobile conduits located in the front stage are regions in which the gate grid and the shutter grid exist, and the region in which the gate grid and the shutter grid exist serves to collect sample ions, and the voltage is generated by the shutter grid. When this is opened, the sample ions are transmitted through the mobile conduit, and the signal is transmitted through the signal detection area. Therefore, it is desirable to design the voltage supplied to the moving conduit constituting the region in which the gate grid and the shutter grid exist to have the same magnitude.

Hereinafter, the unit circuit will be described.

Unit Circuit A capacitor and a resistor, which are capacitors in parallel, are connected in series, and in particular, four unit circuits are connected in series.

Capacitors and resistors constituting the unit circuit have the same size. For example, the size of the capacitor constituting the unit circuit is 0.1F, and the resistance is 2.7 MΩ. In this way, the voltage supplied to each mobile conduit is reduced at a certain rate, so that the sample ions move at a constant speed in the mobile conduit.

However, the resistance value of the resistor constituting the unit circuit that supplies voltage to the moving conduit located at the front end of the moving conduit where the aperture grid is located shall be 3.6 MΩ, not 2.7 MΩ. That is, the resistance value of the resistor constituting the unit circuit for supplying voltage to the moving conduit located at the front end among the moving conduits in which the aperture grid is located is the resistance value of the resistor constituting the unit circuit for supplying the voltage to the moving conduit located at the rear end. Place a resistor with a higher resistance value.

The reason for setting the high resistance value of the resistor constituting the unit circuit that supplies the voltage to the moving conduit located at the front end is to reduce the voltage to a relatively low level in order to minimize the area of the magnetic field on the flight distance of the sample ion. to do That is, it is a process for excluding ions that are incorrectly formed in the ionization process of sample ions.

The unit circuit for supplying voltage to the moving conduit located at the rear end of the moving conduit where the aperture grid is located is composed of the same resistor and capacitor. That is, the unit circuit for supplying voltage to the moving conduit in which the aperture grid is located and the unit circuit for supplying voltage to the moving conduit for inducing free movement of the ionized material are composed of the same resistor and capacitor.

In the circuit for supplying voltage to the 11th moving conduit, two unit small circuits composed of a resistor having a resistance value of 1.0 MΩ and two unit small circuits composed of a resistance having a resistance value of 2.7 MΩ are connected in series. As such, a circuit for supplying a voltage to the 11th moving conduit is proposed as a circuit composed of resistors having two resistance values.

In particular, the unit circuit for supplying a voltage to the moving conduit (the 12th moving conduit) located at the rear end is a section in which the voltage is further lowered to collect the sample ions to the center and reach them. The area where the 12th movement conduit is located is the collect grid area.

In addition, in order to check whether the final voltage is 3.3V by dividing the initial applied voltage -1.8kV, the final unit circuit is configured with a resistor having a resistance value of 2.7MΩ. In the region where the collection grid is located, the sample ions that have collided with the collector must be rapidly discharged to the outside in order to prevent the sample ions from colliding with the collector again. To this end, the area where the collector grid is located uses a resistance of 2.7㏁ to drop the voltage supplied to the moving conduit, and in addition, the sample ions fall to the bottom using the flow rate (wind flow). , a hole is formed at the lower end of the front end of the collector to allow sample ions to fall.

As such, the present invention proposes a voltage supply circuit in order to vary the distribution of the voltage supplied to the moving conduit in order to efficiently move the ionized analyte gas.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible therefrom. .

1: sampling unit 10: suction case
11: air intake part 2: ionization part
12: gas guide 20: body case
21: electrode tip 3: ion conduit
13: suction fan 34: gate grid
35: shutter grid 36: aperture grid
4: collector 41: ion collection ring
42: guide member 43: ion collecting member
44: fastening member 45: PCB
46: metal thin film

Claims (6)

a sampling unit for sucking the sample gas through the air intake unit formed on the front side;
an ionization unit connected to the rear end of the sampling unit and ionizing the sample gas using corona discharge;
a movement conduit connected to the rear end of the ionization unit and providing a movement path of the ionized sample gas by generating an electric field;
a gate grid and a shutter grid installed inside the front end of the mobile conduit to control the inflow of ionic substances; and
It is installed at the rear end of the mobile conduit and includes a collector for detecting the current generated according to the amount of charge when the sample ion arrives,
The mobile conduit is connected to a voltage supply circuit receiving a voltage,
The area in which the moving conduit is located is
an area in which the gate grid and the shutter grid are located;
an area where the aperture grid is located;
a region in which sample ions move freely; and
contains an area where the collect grid is located;
A plurality of unit circuits are connected in series to the circuit for supplying a voltage to the mobile conduit included in the region where the aperture grid is located or the mobile conduit included in the region in which the sample ions freely move,
In the unit circuit, four unit small circuits are connected in series, and in the unit small circuit, a resistor and a capacitor are connected in parallel,
The unit circuit includes a unit circuit composed of a resistor having the same resistance value and a capacitor having the same capacitance and a unit circuit composed of a capacitor having the same capacitance as a resistor having a different resistance value,
In order to minimize the magnetic field region on the flight distance of the sample ion, the unit circuit for supplying voltage to the moving conduit located at the relatively front end among the moving conduits included in the area where the aperture grid is located is the moving conduit located at the relatively rear end. It consists of a resistor with a higher resistance value than the unit circuit that supplies voltage to
The unit circuit that supplies the voltage to the area where the collector grid is located drops the voltage so that the sample ions are gathered in the center.
It includes a unit circuit that checks whether the final voltage is 3.3V by the divided voltage,
In the region where the collection grid is located, the voltage supplied to the moving conduit is lowered to prevent re-collision of sample ions that collided with the collector, and the sample ions fall to the bottom using the flow of wind. Ion Mobility Spectroscopy
delete The ion mobility spectrometer according to claim 1, wherein the absolute value of the voltage supplied to the mobile conduit having a relatively long distance from the ionization unit decreases.
delete delete The method of claim 1,
Ion mobility spectrometer, characterized in that the unit circuit for supplying a voltage to the mobile conduit included in the region in which the sample ions freely move is composed of resistors having the same resistance value.

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