A segmented cylindrical high-field asymmetric waveform ion mobility tube

Abstract

The application discloses a segmented cylinder structure high-field asymmetric waveform ion mobility tube, which comprises a left and right open cylinder-shaped insulating outer cylinder and a cylindrical insulating inner column located in the insulating outer cylinder, an ionization source is arranged near the left end port of the insulating outer cylinder, and an ion receiving electrode is arranged near the right end port in the insulating outer cylinder; two pairs and more than two pairs of segmented separation electrode pairs (including the first, second,..., and Nth electrode pairs) are arranged between the ionization source left end port and the ion receiving electrode; the electrodes located in the inner side of the insulating outer cylinder in the first, second,..., and Nth electrode pairs are applied with different direct current voltages and the same high-field asymmetric radio frequency voltage, and the electrodes corresponding to the outer surface of the insulating inner column are applied with direct current voltage, and the working gas pressure range is 10 pascal to 1 atmosphere; the ion movement speed in the X-axis direction can be reduced, and the resolution is improved; the insulating outer cylinder, the insulating inner column and the two electrodes in the segmented separation electrode pair are coaxially arranged.

Description

TECHNICAL FIELD

[0001] The application is a segmented cylinder structure high-field asymmetric waveform ion mobility tube, characterized by a segmented structure design, which uses a damping electric field opposite to the direction of the carrier gas to reduce the movement speed of ions in the X-axis direction, increase the residence time, and thus improve the resolution. BACKGROUND

[0002] Ion mobility spectrometry is widely used for detecting chemical toxicants, stimulants, narcotics, and explosives due to its high sensitivity, fast analysis speed, and portability. Different ions have different flight times in a uniform field at atmospheric pressure, which enables the separation and analysis of different substances. Resolution and sensitivity are two core indicators of ion mobility spectrometry. Most work focuses on improving these two core indicators. The sensitivity of ion mobility spectrometry is improved by developing efficient ionization sources, increasing ion injection, and compressing the axis. During the flight process, ions diffuse and lose in the axial and radial directions due to the effects of concentration gradient and Coulomb repulsion. Some work has been done on axial compression. For example, Du Yongzai et al. invented a spatial focusing ion gate assembly and a spatial focusing ion mobility tube (201110226912.7). The compression of ion groups (beams) is achieved by applying a voltage to the metal ring of the ion gate or the migration zone, thereby improving the resolution and sensitivity of the ion mobility tube. It achieves spatial compression in the axial direction, but not in the radial direction. Chen Chuang et al. invented a pulsed field enrichment ion mobility tube (CN201510397889.6). By applying a high-voltage pulse to the pulse electrode between the ion source and the ion gate, the ion movement speed is greatly increased during the ion gate opening period, allowing more ions to pass through the ion gate. At the same time, the difference in electric field strength on both sides of the ion gate caused by the high-voltage pulse is used to spatially focus the ion groups that have passed through the ion gate, maintaining the original resolution of the ion mobility tube. However, the patent also does not avoid the radial divergence of ions.

[0003] If the radial compression of ions can be achieved, the sensitivity of ion mobility spectrometry can be further improved. The present application achieves radial compression of ions by designing a compression electrode with a symmetric structure, thereby improving the efficiency and sensitivity of ion detection. Ion mobility spectrometry is widely used for detecting chemical toxicants, stimulants, narcotics, and explosives due to its high sensitivity, fast analysis speed, and portability. Among various types of ion mobility spectrometry, high-field asymmetric waveform ion mobility spectrometry technology has the advantages of high detection sensitivity, simple equipment, small size, portability, and low detection cost, and is increasingly valued by people.

[0004] High-field asymmetric waveform ion mobility spectrometry is a material analysis and detection technology based on the continuous development of traditional ion mobility spectrometry technology. It was first reported in 1993 by Buryakov et al. It is based on the change of ion mobility in high field (E / N > 40Td, 1Td = 10-17Vcm2) and low field (E / N < 2Td) to realize the detection of different substances. The principle of asymmetric field ion mobility spectrometry is as follows: the carrier gas makes the substance ions pass through the drift region perpendicular to the direction of the electric field, and the drift region is applied with an asymmetric field with positive and negative switching of radio frequency. The time average of the voltage is zero throughout the radio frequency cycle. In this way, in the high and low field sections, the ions have a vertical displacement along the electric field with a mobility K, but if the mobility in the high field and the low field is different, the ions will overall leave the original position in the vertical direction in a cycle, resulting in a net displacement. After a certain accumulation time, the displacement of the ions will make them hit the plate and be neutralized. In order to make the ions pass through the detection area smoothly, a direct current electric field can be superimposed on the original electric field. When the direct current electric field is appropriate, the net displacement of the ions in the vertical direction is zero, and then they can pass through the detection channel and be detected. By scanning the above direct current electric field, different ions can be detected.

[0005] High-field asymmetric waveform ion mobility spectrometry can separate compounds with the same molecular weight but different structures, and can separate and analyze isomers in combination with mass spectrometry. In addition, in the field of protein analysis, high-field asymmetric waveform ion mobility spectrometry can be used as a pre-separation front stage of mass spectrometry to eliminate low-molecular-weight compounds entering the mass spectrometer, greatly reduce background noise, improve signal-to-noise ratio, and increase sensitivity by 3 orders of magnitude. When the traditional high-field asymmetric waveform ion mobility spectrometry is combined with mass spectrometry, only ions at a certain point can enter the mass spectrometer (Journal of the American Society for Mass Spectrometry 1999; 10: 492-501.), the ion utilization rate is low, and the sensitivity is poor. In order to improve the ion utilization rate, a dome structure is proposed (Analytical Chemistry 2005; 77: 6381-6388). In order to realize the change of mobility in high and low fields, a very high field strength is often required; this means that the voltage needs to be increased and the plate spacing needs to be reduced. In order to realize miniaturization, the voltage that can be increased is limited. Therefore, the plate spacing of the traditional high-field asymmetric waveform ion mobility spectrometry is often set to be less than 1mm. This means that the time in the separation zone needs to be reduced to avoid collision quenching between ions and plates, thereby ensuring detection sensitivity. However, this results in low resolution. SUMMARY

[0006] The purpose of the present application is to solve the problem of low resolution of high-field asymmetric waveform ion mobility spectrometry, and to improve the separation capacity of the instrument.

[0007] To achieve this purpose, the technical solution adopted by the present application is:

[0008] Based on the segmented cylindrical structure design, the damping electric field opposite to the ion motion direction formed between different segments is used to reduce the ion residence time in the high-field asymmetric waveform ion mobility tube, realize the sufficient change of ion mobility between high and low fields, realize the effective separation of different ions, and thus improve the resolution capacity.

[0009] A segmented cylindrical structure high-field asymmetric waveform ion mobility tube, comprising a left and right open cylindrical insulating outer cylinder and a cylindrical insulating inner column located in the insulating outer cylinder, with the left-to-right direction as the X-axis direction, the top-to-bottom direction as the Y-axis direction, and the direction perpendicular to the X-axis and Y-axis as the Z-axis direction.

[0010] An ionization source is provided near the left end of the insulating outer cylinder, and an ion receiving electrode is provided near the right end of the insulating outer cylinder, with the receiving surface of the ion receiving electrode parallel to the X-axis.

[0011] Two or more pairs of segmented separation electrode pairs (including first, second, …, Nth electrode pairs), isolation electrode pairs, and ion receiving electrodes are provided between the ionization source left end and the ion receiving electrode; the two electrodes in the segmented separation electrode pair are respectively fixed on the inner wall surface of the insulating outer cylinder and the outer wall surface of the insulating inner column, and they are oppositely arranged and are both cylindrical electrodes; the first, second, …, Nth electrode pairs, isolation electrode pairs, and ion receiving electrodes are sequentially arranged along the X-axis direction.

[0012] Different DC voltages and the same high-field asymmetric radio frequency voltage are applied to the electrodes inside the insulating outer cylinder in the first, second, …, Nth electrode pairs, and the corresponding electrodes on the outer surface of the insulating inner column are applied with DC voltage, and N is an integer greater than or equal to 2.

[0013] The direction of the carrier gas flow is along the X-axis direction, the axial direction electric field force experienced by the ion in the segmented high-field asymmetric waveform ion mobility tube is opposite to the direction of the carrier gas flow, and is smaller than the carrier force generated by the carrier gas; by changing DC1, DC2, …, DCN, U1, U2, …, UN applied to the first, second, …, Nth electrode pairs, the residence time of the ion in the segmented high-field asymmetric waveform ion mobility tube can be controlled; the voltage difference between DC1 and U1 is the same as the voltage difference between DC2 and U2 and the voltage difference between DCN and UN, and the amplitudes of U1, U2, …, UN monotonically increase (or decrease).

[0014] The segmented separation electrode pairs are at least two pairs (preferably three pairs, i.e. N=3, the first, second, …, Nth electrode pairs are the first, second, and third electrode pairs, and the distance between each pair of electrodes is 0.01 to 2 mm; the distance between the segmented separation electrode pairs is 0.1 to 5 mm.

[0015] The isolated electrode pair is connected to the ground.

[0016] A direct current voltage of 1-10V is applied to the ion receiving electrode.

[0017] The working pressure range is 10 Pa to 1 atm.

[0018] The ion movement speed in the X-axis direction is reduced, and the resolution is improved.

[0019] The insulating outer cylinder, the insulating inner column, and the two electrodes in the segmented separation electrode pair are coaxially arranged. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The application relates to a segmented cylinder structure high-field asymmetric waveform ion mobility tube.

[0021] Figure 2 The detection spectrum of DMMP. DETAILED DESCRIPTION

[0022] The application relates to a segmented cylinder structure high-field asymmetric waveform ion mobility tube.

[0023] The ionization source 1 is arranged near the left end of the insulating outer cylinder 2, and the ion receiving electrode 10, 10' is arranged near the right end of the insulating outer cylinder 2.

[0024] There are 5 pairs of segmented separation electrode pairs between the left port of ionization source 1 and ion receiving electrode 10, 10', including first, second, third, fourth, fifth segmented separation electrode pairs 4, 4', 5, 5', 6, 6', 7, 7', 8, 8'; there are isolation electrode pairs 9, 9' between the fifth segmented separation electrode and the ion receiving electrode 10, 10'; the two electrodes of the isolation electrode pair, the ion receiving electrode and the segmented separation electrode pair are fixed on the inner wall of the insulating outer cylinder 2 and the outer wall of the insulating inner column 3, respectively, which are oppositely arranged and are cylindrical electrodes; the first, second, third, fourth, fifth electrode pairs 4, 4', 5, 5', 6, 6', 7, 7', 8, 8', the isolation electrode pairs 9, 9', and the ion receiving electrode 10, 10 are sequentially arranged along the X-axis direction.

[0025] Different DC voltages (DC1, DC2, DC3, DC4, DC5) and the same high-field asymmetric radio frequency voltage are applied to the electrodes 4, 5, 6, 7, 8 inside the insulating outer cylinder 2 in the first, second, third, fourth, fifth electrode pairs 4, 4', 5, 5', 6, 6', 7, 7', 8, 8', and the corresponding electrodes 4', 5', …, 6' on the outer surface of the insulating inner column (3) are applied with DC voltages U1, U2, U3, U4, U5.

[0026] The direction of the carrier gas flow is along the X-axis direction, and the axial direction electric field force experienced by the ions in the segmented high-field asymmetric wave ion migration tube is opposite to the direction of the carrier gas flow and smaller than the carrier force generated by the carrier gas; by changing DC1, DC2, DC3, DC4, DC5, U1, U2, U3, U4, U5 applied to the first, second, third, fourth, fifth electrode pairs 4, 4', 5, 5', 6, 6', 7, 7', 8, 8', the residence time of ions in the segmented high-field asymmetric wave ion migration tube can be controlled; the voltage difference between DC1 and U1, the voltage difference between DC2 and U2, the voltage difference between DC3 and U3, the voltage difference between DC4 and U4, and the voltage difference between DC5 and U5 are the same, and the amplitudes of U1, U2, U3, U4, U5 monotonically increase (or decrease).

[0027] The distance between any two adjacent electrodes of the first, second, third, fourth, fifth electrode pairs 4, 4', 5, 5', 6, 6', 7, 7', 8, 8', the isolation electrode pairs 9, 9', and the ion receiving electrode 10, 10 is 0.5 millimeter.

[0028] The distance between any two adjacent electrodes of the first, second, third, fourth, fifth electrode pairs 4, 4', 5, 5', 6, 6', 7, 7', 8, 8', the isolation electrode pairs 9, 9', and the ion receiving electrode 10, 10 is 0.5 millimeter.

[0029] A 1V DC voltage is applied to the ion receiving electrode 10, 10'.

[0030] The working pressure range is 1 atmosphere.

[0031] It can reduce the ion movement speed in the X-axis direction and improve the resolution.

[0032] The insulating outer cylinder 2, the insulating inner column 3, the segmented separation electrode pair, the isolated ground electrode pair, and two electrodes in the ion receiving electrode are coaxially arranged.

[0033] Embodiment:

[0034] Ionization source (1), insulating outer cylinder (2), cylindrical insulating inner column (3), separation electrode pair (4, 4', 5, 5', 6, 6', 7, 7', 8, 8'), isolated ground electrode pair (9, 9'), ion receiving electrode (10, 10').

[0035] DMMP enters the separation zone formed by the separation electrode pair (4, 4', 5, 5', 6, 6', 7, 7', 8, 8') through the vacuum ultraviolet ionization source 1, and the mobility changes under the action of high and low fields in each separation electrode pair; because the DC voltage applied on different separation electrode pairs is different, the damping force in the axial direction is reduced, the flight speed of ions in the axial direction is reduced, and the residence time in the separation zone is increased, thereby improving the separation effect. Finally, the ions enter the detection zone formed by the ion receiving electrode (10, 10') through the region between the isolated electrode pair (9, 9'). The typical spectrum of dimethyl methylphosphonate with a three-segment electrode pair cylindrical structure high-field asymmetric waveform ion mobility spectrometry under different segment voltage differences is shown in Figure 2 The experimental conditions are: RF is 1.2MHz square wave asymmetric high voltage, high field is 1500V, low field is 500V, high field time and low field time ratio is 0.3 microsecond: 0.9 microsecond, voltage difference between DC and U is 4V. The distance between the plates is 0.5mm, and the distance between the segmented electrode pairs is 0.5mm. U1-U2, U2-U3, U3-U4, U4-U5 have the same δU. Figure 2 The results of δU of 0.1V, 0.12V, 0.13V, 0.14V, 0.15V from top to bottom are shown.

Claims

1. A segmented cylindrical structure high-field asymmetric waveform ion mobility tube, characterized in that: comprising a left and right open cylindrical insulating outer cylinder (2) and a cylindrical insulating inner column (3) located in the insulating outer cylinder (2), taking the direction from left to right as the X-axis direction, taking the direction from top to bottom as the Y-axis direction, and taking the direction perpendicular to the X-axis and Y-axis as the Z-axis direction; an ionization source (1) is provided near the left end of the insulating outer cylinder (2), and an ion receiving electrode (10, 10') is provided near the right end of the insulating outer cylinder (2) inside the insulating outer cylinder (2), the receiving surface of the ion receiving electrode (10, 10') is parallel to the X-axis; two or more pairs of segmented separation electrode pairs, isolated electrode pairs (9, 9'), are provided between the ionization source (1) left end and the ion receiving electrode (10, 10'), the ion receiving electrode is a detection electrode pair, the segmented separation electrode pairs include first, second, …, N segmented separation electrode pairs (4, 4', 5, 5', N, N'); the two electrodes in the segmented separation electrode pair are respectively fixed on the inner wall surface of the insulating outer cylinder (2) and the outer wall surface of the insulating inner column (3), they are oppositely arranged and are both cylindrical electrodes; the first, second, …, N electrode pairs (4, 4', 5, 5', N, N'), the isolated electrode pairs (9, 9'), and the ion receiving electrode (10, 10') are sequentially and spaced apart along the X-axis direction; different DC voltages DC1, DC2, …, DCN and the same high-field asymmetric radio frequency voltage are applied to the electrodes (4, 5, …, N) inside the insulating outer cylinder (2) in the first, second, …, N electrode pairs (4, 4', 5, 5', …, N, N'), and the corresponding electrodes (4', 5', …, N') on the outer surface of the insulating inner column (3) are applied with DC voltages U1, U2, …, UN, N is an integer greater than or equal to 2.

2. The segmented cylindrical structure high-field asymmetric waveform ion mobility tube according to claim 1, characterized in that: the direction of the carrier gas flow is along the X-axis direction, the axial direction electric field force experienced by the ions in the segmented high-field asymmetric waveform ion mobility tube is opposite to the direction of the carrier gas flow, and is smaller than the carrier force generated by the carrier gas; by changing DC1, DC2, …, DCN, U1, U2, …, UN applied to the first, second, …, N electrode pairs (4, 4', 5, 5', …, N, N'), the residence time of the ions in the segmented high-field asymmetric waveform ion mobility tube can be controlled; the DC voltage difference of the two electrodes in each pair of the segmented separation electrode pairs is the same, and the amplitudes of U1, U2, …, UN monotonically increase or decrease.

3. The segmented cylindrical structure high-field asymmetric waveform ion mobility tube according to claim 1 or 2, characterized in that: the segmented separation electrode pairs are 3 pairs, i.e. N = 3, the first, second, …, N electrode pairs (4, 4', 5, 5', …, 6, 6') are the first, second, and third electrode pairs (4, 4', 5, 5', 6, 6'), and the spacing between each pair of electrodes is 0.01 to 2 mm; the spacing between the segmented separation electrode pairs is 0.1 to 5 mm. ​ ​ ​ ​ ​ ​ ​ ​ 4. The segmented cylindrical structure high-field asymmetric waveform ion mobility tube according to claim 1, wherein: the isolated ground electrode pair (9, 9') is connected to the ground; and a direct current voltage of 1-10 V is applied to the ion receiving electrode (10, 10').

5. The segmented cylindrical structure high-field asymmetric waveform ion mobility tube according to claim 1, wherein: the working pressure range is 10 Pa to 1 atm; and the ion movement speed in the X-axis direction is reduced, and the resolution is improved.

7. The segmented cylindrical structure high-field asymmetric waveform ion mobility tube according to claim 1, wherein: the insulating outer cylinder (2), the insulating inner column (3), the corresponding two electrodes in the segmented separation electrode pair, the two electrodes in the isolated ground electrode pair, and the two electrodes in the ion receiving electrode are coaxially arranged. ​ ​ 6. The segmented cylindrical structure high field asymmetric waveform ion mobility tube of claim 1, wherein: ​ ​ ​

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