CN201561956U - Ion Mobility Spectrometer - Google Patents

Abstract

The utility model discloses an ion mobility spectrometer, which comprises a sample introduction system and an ionization region. The sample molecules enter the ionization region of the drift tube through the sample introduction system and are carried by the carrier gas to ionize to form sample ions. The feature is that the The sampling system is a hyperbolic paraboloid structure with the plane where the sampling test paper is located as the axis of symmetry. The carrier gas flows in the side of the sampling test paper carrying the sample molecules along the two ends close to the ionization zone, forming a double paraboloid and a single leaf-shaped airflow. , sweep and carry the sample molecules on the sampling test paper to the ionization area. The ion mobility spectrometer also includes a sampling system, which is located on the side of the sampling test paper without sample molecules. The sampling system is in the shape of a truncated cone, and there is a gas baffle inside which makes the air flow form a tornado cyclone. The sample injection and sampling system of the ion mobility spectrometer of the utility model can greatly improve the detection sensitivity of the ion mobility spectrometer.

Description

Ion Mobility Spectrometer

technical field

The utility model relates to an ion mobility spectrometer for trace detection, in particular to an ion mobility spectrometer capable of improving the detection sensitivity of the ion mobility spectrometer.

Background technique

The ion mobility method (IMS for short) is one of the mainstream trace detection methods in the world at present. The ion mobility spectrometer is an instrument for detecting and identifying substances based on the principle of the ion mobility method. It can quickly detect drugs, explosives, poisonous gases and biochemical gases online. It is widely used in many fields such as military (chemical defense, monitoring), civil (anti-terrorism, anti-drug, etc.), and plays an important role in maintaining national security, maintaining social stability, strengthening national defense forces, and maintaining national economy and people's livelihood.

The gas circuit structure of ion mobility spectrometry is shown in Figure 1. With the semi-permeable membrane as the boundary, the gas circuit of the ion mobility spectrometer is divided into two relatively independent parts: the sampling system and the sampling system. The sampling system includes a sampling head, a sampling heating device (inside the sampling head) and a sampling air pump. The main function is to suck the molecules of the substance to be detected to the vicinity of the semi-permeable membrane through the sampling air pump. Through osmosis, diffusion, etc., the molecules of the substance to be detected can pass through the semi-permeable membrane and enter the sampling system. The air flow rate of the sampling system is usually relatively large, usually up to liters per minute, so that even a very small amount of suspected molecules may be drawn into the ion mobility spectrometer for detection. The semi-permeable membrane can block the contamination of the drift tube cavity of the ion mobility spectrometer by dust, etc., but the existence of the semi-permeable membrane will reduce the detection sensitivity of the instrument. The sampling system includes an air pump, a desiccant cavity, a dopant cavity, a sampling head, etc. The sample molecules passing through the semi-permeable membrane are carried by the carrier gas into the ionization region and ionized to form sample ions. Under the action of the electric field in the drift tube and the drift gas, the sample ions with different masses and collision cross sections are separated in the drift tube cavity. Under the condition of weak electric field, the speed of ion migration v=k(T)*E, where k(T) is the mobility of ions, which is related to factors such as the mass and collision cross section of ions, and E is the electric field strength. Ions with different speeds hit the collecting electrodes to form charge signals containing different time information, and different sample ions (molecules) can be distinguished based on this information. The sampling system is an essential part of the traditional ion mobility spectrometer. The sampling system is usually a detachable part. When the ion mobility spectrometer directly measures gas or solid powder, the upper sampling system can be installed.

The method of detecting samples by ion mobility spectrometer is divided into swab sampling method and direct sampling method. The traditional ion mobility spectrometer wipes the sample, as shown in Figure 2. Usually, the multi-fold sampling paper with a certain degree of flexibility is used to wipe the object to be detected, and then the sampling test paper is placed in the sampling test paper card slot of the sampling head, as shown in Figure 1, the sampling port The heating plate heats and analyzes the material particles attached to the sampling test paper, and at the same time, a carrier gas flow along the sampling paper—the ionization zone direction penetrates the sampling paper, carrying the analyzed sample molecules into the ionization zone for ionization. The advantages of this sampling system are (1) easy processing; (2) low requirements for related electronic control and easy implementation. However, the sampling efficiency is low: only when the carrier gas penetrates the sampling paper can the particles to be detected attached to the sampling paper and thermally desorbed be brought into the ionization zone. Excessive carrier gas flow will easily affect the gas balance in the ionization zone, while The carrier gas of the small gas flow has poor penetrating power, and can only carry part of the sample molecules into the ionization region, resulting in a decrease in the sensitivity detection performance of ion mobility spectrometry.

Traditional ion mobility spectrometers measure gases or directly sample them, and usually use a gas pump to directly extract the gas path structure of the sample molecules, as shown in Figure 3. The advantages of this direct sampling are (1) simple principle; (2) convenient processing; (3) easy replacement and cleaning of the sampling head; (4) no sampling test paper is required. However, the outstanding disadvantage is that the sampling efficiency is low, which directly affects the detection sensitivity during gas measurement, and the impact of this defect is fatal to a high-sensitivity detection instrument such as ion migration.

Utility model content

The purpose of the utility model is to provide an ion mobility spectrometer whose sampling and sample feeding system can improve the detection sensitivity of the spectrometer. Spectrometers with high sensitivity performance are of great significance for expanding the detection application range of ion mobility spectrometers.

In order to achieve the above object, the technical scheme of the utility model is as follows:

An ion mobility spectrometer, comprising a drift tube with a sampling system and an ionization zone, the sampling system is located in front of the ionization zone, and the sample molecules enter the ionization of the drift tube under the carrying effect of the carrier gas through the sampling system Zone ionization forms sample ions. The sampling system is a hyperbolic paraboloid structure with the plane where the sampling test paper is located as the axis of symmetry. A single-leaf airflow with double paraboloids sweeps and carries the sample molecules on the sampling test paper to the ionization area.

The ion mobility spectrometer also includes a sampling system located on the side of the sampling test paper without sample molecules. The sampling system includes an inner lining cylinder and an outer lining cylinder. The helical stainless steel gas separator of the tornado cyclone.

The sampling system is a conical structure.

There is an infrared heating device inside the conical structure of the sampling system.

The hyperbolic parabolic surface sampling system of the utility model has the following advantages: (1) overcomes the influence that the large carrier gas flow rate may have on the gas balance in the ionization zone, and reduces the spectral peak drift caused by the unstable air flow in the ionization zone; (2) can Efficiently carry the samples on the sampling test paper into the ionization area, effectively improving the sensitivity of ion detection; (3) At the same time, the sample molecules entering the ionization area are spatially compressed, so that they are concentrated in the middle area of the ionization area, thereby improving the resolution of the ion mobility spectrum Rate.

The advantages of the sampling system using the circular table-shaped tornado are: (1) the sampling of the tornado cyclone structure has higher particle extraction efficiency than the traditional direct sampling; (2) the air flow of the tornado sampling system has little influence on the air flow inside the drift tube; (3) The inner surface of the sampling head is not easily contaminated by the measured object due to the cyclone; (4) The principle is more complicated, but the process is easier to realize; (5) The built-in infrared heating device can more effectively vaporize the refractory substances, Can reduce the detection limit of difficult volatile substances.

Description of drawings

Figure 1 is a schematic diagram of the gas circuit of the ion mobility spectrometer;

Figure 2 is a schematic diagram of traditional ion mobility spectrometry wipe sampling detection detection;

Fig. 3 is a principle diagram of direct sample injection for traditional ion mobility spectrometry detection;

Fig. 4 is the structural diagram of the double parabolic inlet of the ion mobility spectrometer of the present invention;

Fig. 5 is an effect diagram of the principle effect diagram of the hyperbolic paraboloid structure of the ion mobility spectrum;

Figure 6 is an effect diagram of the principle of ion mobility spectrometry double parabolic structure tornado sampling;

Fig. 7 is a mechanical structure diagram of the tornado sampling system, in which (a) the assembly structure of the inner liner and the cylindrical helicoid; (b) the overall assembly structure of the tornado.

Detailed ways

Below, according to Fig. 4 to Fig. 7, a preferred embodiment of the utility model is given and described in detail, so that the functions and characteristics of the utility model can be better understood.

As shown in Figure 4, one embodiment of the present utility model is that the test paper wipes the sampling method to carry out substance detection, and the drift tube of an ion mobility spectrometer has a sampling system 1 and an ionization region, and the sampling system 1 adopts a hyperbolic paraboloid Structure, taking the plane where the sampling test paper 2 is located as the axis of symmetry, the carrier gas 3 is blown through the sampling test paper on the same side where the sampling test paper 2 carries the sampling particles 2 and then carry the sample molecules 5 attached to the sampling test paper and desorbed into the ionization region, and the carrier gas 3 of the hyperbolic paraboloid sampling system does not need to penetrate the sampling test paper 2 . The carrier gas 3 flows in the hyperbolic paraboloid structure, forming a double paraboloid and a single lobe-shaped airflow effect, which can effectively sweep and carry the sample molecules 5 on the sampling paper 2 into the ionization region.

Compared with the prior art, the sampling system 1 with double parabolic structure has different intake positions and shapes of the carrier gas flow formed by different structures, resulting in great differences in the carrying effect of the carrier gas flow. The airflow effect formed by the double parabolic structure sampling system is shown in Figure 5, the carrier gas flow 3 and the sample molecules 5 on the sampling paper 2 are on the same side of the sampling paper, while the carrier gas flow of the prior art, as shown in Figure 2, And the sample molecules 5 on the sampling paper 2 are on both sides of the sampling test paper, the carrier gas flow 3 must penetrate the sampling test paper 2 to effectively carry the sample molecules into the ionization region. The hyperbolic paraboloid sampling system has the following advantages: (1) It overcomes the possible influence of the large carrier gas flow rate on the gas balance in the ionization region, and reduces the peak drift caused by the unstable air flow in the ionization region; (2) It can carry samples efficiently The sample on the test paper enters the ionization area, which effectively improves the sensitivity of ion detection; (3) At the same time, the sample molecules entering the ionization area are compressed in space, so that they are concentrated in the middle area of the ionization area, thereby improving the resolution of the ion mobility spectrum.

Another embodiment of the present utility model adopts the measurement method of direct sample injection, and the ion mobility spectrometer also has a sampling system 6, as shown in Figure 7, the sampling system 6 includes three parts: inner lining tube 8, Spiral stainless steel gas separator 9, outer liner 10. The spiral stainless steel gas partition 9 is located between the inner and outer liners, and the airflow blown by the sampling fan flows in a spiral space formed by these three parts, and is regulated by the gas partition 9 inside the round table to form a whirling tornado airflow.

The "tornado" sampling system of the present utility model adopts a circular platform-shaped external structure, and an air pump (not shown) is arranged at one end close to the drift tube to send a certain flow of gas into the circular platform 7, and the gas is in the gas groove inside the circular platform 7 The flow forms a swirling tornado cyclone, and the weak negative air pressure in the center of the cyclone has a strong suction force, which can effectively pump particles into the ionization zone efficiently. The frustum-shaped structure has the following advantages: 1. The front end of the sampling system has a larger contact area, which can collect samples more effectively when collecting samples; 2. The frustum-shaped structure can provide a larger space for the entire sampling system. It is convenient to install the heating device inside; 3. The actual application effect, the efficiency of the sampling system with the circular platform structure is much higher than that of the cylindrical structure with the same inner diameter.

The frustum-shaped sampling structure also has an infrared heating device 11 inside, which can be heated during low-temperature detection or when the vaporization temperature of the detected object is relatively high, so that more substances can be sucked into the ion mobility spectrometer by the "tornado" for detection. The function of the infrared heating device is to increase the thermal desorption of more sample molecules during direct sample injection, and then be absorbed near the semi-permeable membrane, thereby improving the sensitivity of the instrument.

The advantages of the tornado sampling system (1) The principle is more complicated, but the process is relatively easy to process and realize; (2) The sampling of the cyclone structure has higher particle extraction efficiency than the traditional direct sampling; (3) The inner surface of the sampling head has a cyclone , not easily contaminated by the measured object; (4) The airflow of the tornado sampling system has little effect on the airflow inside the drift tube; (5) The built-in infrared heating device can more effectively vaporize the refractory substances and reduce the detection of refractory substances limit.

The tornado sampling system does not need to be installed when the substance detection is carried out by wiping with test paper. The measurement method of direct sampling needs to be used together with the tornado sampling system and the double parabolic sampling structure.

The ion mobility spectrometer of the utility model adopts the "hyperbolic parabolic surface sampling system and the tornado sampling system". poison.

The foregoing descriptions of the more detailed embodiments are provided to enable anyone skilled in the art to understand the present invention. To this embodiment, those skilled in the art can make various modifications or transformations without departing from the principle of the utility model. That is to say, all simple and equivalent changes and modifications made according to the claims of the utility model application and the contents of the description all fall within the protection scope of the claims of the utility model patent.

Claims (4)

1. An ion mobility spectrometer, comprising a drift tube with a sampling system and an ionization zone, the sampling system is positioned in front of the ionization zone, and the sample molecules enter the drift tube under the carrying effect of the carrier gas through the sampling system The ionization region ionizes to form sample ions, and it is characterized in that the sampling system is a hyperbolic paraboloid structure with the plane where the sampling test paper is located as the axis of symmetry. 2. ion mobility spectrometer according to claim 1, is characterized in that, also comprises a sampling system, is positioned at sampling test paper and does not have sample molecule side, and described sampling system comprises liner cylinder, outer liner cylinder, inside Between the liner and the outer liner, there is a spiral stainless steel gas baffle that makes the air flow form a tornado cyclone. 3. The ion mobility spectrometer according to claim 2, wherein the sampling system is a frustoconical structure. 4. The ion mobility spectrometer according to claim 3, wherein an infrared heating device is arranged inside the frustum-shaped structure of the sampling system.

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