CN110491765B - Control method of ion gate in ion mobility spectrometry - Google Patents

Control method of ion gate in ion mobility spectrometry Download PDF

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CN110491765B
CN110491765B CN201811412006.4A CN201811412006A CN110491765B CN 110491765 B CN110491765 B CN 110491765B CN 201811412006 A CN201811412006 A CN 201811412006A CN 110491765 B CN110491765 B CN 110491765B
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陈创
李海洋
蒋丹丹
陈红
厉梅
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Dalian Institute of Chemical Physics of CAS
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/622—Ion mobility spectrometry
    • G01N27/624—Differential mobility spectrometry [DMS]; Field asymmetric-waveform ion mobility spectrometry [FAIMS]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
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    • H01J49/26—Mass spectrometers or separator tubes

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Abstract

The invention discloses a novel method for controlling a Bradbury-Nielsen type ion gate in ion mobility spectrometry. According to the method, by adjusting the electrode voltage of the ion gate, on one hand, the time-space compression is performed on the ion clusters in the IMS migration region by fully utilizing the non-uniform electric field, so that the resolution capability of the ion mobility spectrum is improved, on the other hand, the consumption of an ion clearance area formed by the ion gate closing voltage on the ion clusters in the ion mobility spectrum migration region can be effectively reduced, and the IMS detection sensitivity is improved. The method is simple, and hardware improvement on the ion transfer tube is not needed.

Description

Control method of ion gate in ion mobility spectrometry
Technical Field
The invention relates to a voltage control method of an ion gate of an important component of an ion mobility spectrum, in particular to a method for improving the resolution capability and the detection sensitivity of the ion mobility spectrum by controlling the electrode voltage of the ion gate.
Background
Ion Mobility Spectrometry (IMS) requires an Ion gate which is periodically opened to inject Ion packets into an Ion Mobility region to realize the separation and detection of target ions. The time width of the ion gate injected ion packet and the total amount of ions determine the Resolving Power (R) and detection sensitivity of the ion mobility spectrometry.
For IMS with fixed migration zone length L, R is the time w for opening the door by the ion gateinjAnd peak broadening due to cluster migration (16 k)BTln2/eUd)1/2(L2/KUd) The decision is as shown in equation 1. When the instrument parameters are fixed, the peak broadening caused by ion cluster migration is fixed, and the opening time w of the ion gate is fixedinjBecomes the only determinant of R: w is ainjThe smaller the R, the higher the R.
Figure GDA0002459361050000011
Wherein L is the length of the ion mobility region, and K is the ion mobility (K)＝K0(T/273.5) (760/P), T is temperature and P is pressure), UdIs the total voltage of the transition region, tdIs the ion peak migration time, w0.5Is the half-peak width of the ion peak, winj16k for ion door opening timeBTln2/eUdResulting in a peak broadening coefficient for ion diffusion.
The Bradbury-Nielsen type ion gate (BNG) is the ion gate configuration commonly employed in current commercial IMS instruments. The BNG realizes the chopping of ion clusters by using a radial electric field which is formed by two groups of metal wires which are arranged in a coplanar manner and is vertical to the migration direction of ions. Since BNG mechanical structures are almost negligible in thickness (equal to the filament diameter of BNG, typically ≦ 0.1mm), it is generally considered the best ion chopping tool: the ion plate can be realized in the time domain (w)inj) By reducing winjA high IMS resolution is obtained.
However, in 2012, professor lie oceanographic, to the university of ligate, discovered when studying the effect of BNG gate-closing voltage on IMS resolution: when the BNG is closed, the electric field for closing the door permeates toward the ion migration region and the ion reaction region which are adjacent to the BNG. Penetration of the gate-closing electric field into the transition region, causing a transient enhancement of the electric field in the transition region in the immediate vicinity of the ion gate region, in time domain w, to ion packets passing through the BNGinjThe compression is carried out, so that the half-peak width of the ion peak actually detected by the IMS is narrowed, and the resolution capability of the IMS is improved[11](ii) a In addition, the penetration of the door-closing electric field simultaneously causes significant ion clearance zones on both sides of the BNG, the axial depth of which is much greater than the filament diameter of the BNG and is comparable to the filament spacing (typically, when the filament spacing is 1mm, the average depth of the ion clearance zones reaches 1.1 mm). On the one hand, the time w for opening the door at BNGinjOnly ions passing through the ion clearance area can enter the ion migration area to be separated and detected, so that the actual time width of ion clusters injected into the IMS migration area by BNG is far shorter than the door opening time of BNG, and the IMS detection sensitivity is reduced; on the other hand, after the BNG door opening time is over, the BNG door closing electric field can pull a part of ions entering the IMS migration area back to the electrode of BNG to be consumed in an ion clearance area formed on one side of the BNG close to the IMS migration area, and the IMS detection is further reducedThe sensitivity of the assay.
The invention discloses a new method for controlling BNG gate electrode voltage, which fully utilizes a non-uniform electric field to perform space-time compression on ion clusters in an IMS migration region so as to improve the resolution capability of the IMS, simultaneously reduces the consumption of an ion clearance region formed by BNG gate electrode voltage on the ion clusters in the IMS migration region, and improves the IMS detection sensitivity.
Disclosure of Invention
The invention aims to provide a novel method for controlling the BNG gate electrode voltage, which fully utilizes a non-uniform electric field to perform space-time compression on ion clusters in an IMS migration region so as to improve the resolution capability of the IMS, simultaneously reduces the consumption of an ion clearance region formed by the BNG gate-closing voltage on the ion clusters in the IMS migration region, and improves the IMS detection sensitivity.
In order to achieve the purpose, the invention adopts the technical scheme that:
a control method of an ion gate in an ion mobility spectrometry comprises an ion mobility tube, wherein the ion mobility tube is composed of an ion source, an ionization region, the ion gate, a migration region and an ion receiving electrode which are sequentially arranged from left to right.
The ion gate is located between the ionization region on the left side and the mobility region on the right side.
The ion gate is formed by arranging more than 4 strip-shaped electrodes in parallel at intervals from top to bottom, wherein odd strip-shaped electrodes serve as first gate electrodes from top to bottom, and even strip-shaped electrodes serve as second gate electrodes.
Or the annular electrodes with the same geometric center are arranged at intervals from inside to outside; from the inside to the outside, the odd-numbered ring electrodes serve as first gate electrodes, and the even-numbered ring electrodes serve as second gate electrodes.
The first gate electrode and the second gate electrode are respectively connected with two pulse direct-current high-voltage power supplies.
And sequentially applying voltages to the first gate electrode and the second gate electrode according to the time interval length of the first preset time period, the time interval length of the second preset time period and the time interval length of the third preset time period.
And in the time interval length of the first preset time period, a first voltage is simultaneously applied to the first gate electrode and the second gate electrode, a direct current electric field pointing to the direction of the ion receiving electrode along the ion source is formed in the ion migration tube, and ions in the ionization region enter the migration region through the ion gate.
And in the time interval length of a second preset time period, a second voltage higher than the first voltage is simultaneously applied to the first gate electrode and the second gate electrode, a direct current electric field pointing to the direction of an ion source along the ion gate is formed in an ionization region of the ion migration tube, ions in the ionization region move towards the direction of the ion source, a gradually weakened direct current electric field pointing to the direction of an ion receiving pole along the ion gate is formed in the migration region of the ion migration tube, and the ions entering the migration region move towards the ion receiving pole.
And in the time interval length of a third preset time period, a first voltage is applied to the first gate electrode, a third voltage higher than the first voltage is simultaneously applied to the second gate electrode, the third voltage is lower than the second voltage, a direct current electric field pointing to the direction of the ion gate along the ion source is formed in the ionization region of the ion migration tube, ions in the ionization region move towards the direction of the ion gate, an electric field perpendicular to the axial direction of the ion migration tube is formed between the first gate electrode and the second gate electrode, the ions in the ionization region are prevented from entering the migration region through the ion gate, a direct current electric field pointing to the direction of the ion receiving electrode along the ion gate is formed in the migration region of the ion migration tube, and the ions in the migration region sequentially reach the ion receiving electrode under the action of the direct current electric field to be detected.
The strip-shaped electrode is a metal wire or a spiral wire-shaped electrode wound on the cylinder or a metal sheet or a metal mesh sheet.
The annular electrode is a circular ring electrode or a square ring electrode.
The value of the first preset time interval is between 0.001ms and 0.2ms, the value of the second preset time interval is between 0.001ms and 1ms, and the value of the third preset time interval is between 0.2ms and 10 ms; the sum of the first, second and third preset time intervals constitutes one complete time period for the operation of the ion gate.
The sum of the first preset time interval, the second preset time interval and the third preset time interval forms a complete time period of the ion gate work
And when the ion migration tube works, the voltages applied to the first gate electrode and the second gate electrode of the ion gate are periodically and circularly adjusted according to the time period.
The invention has the advantages that
The invention can synchronously improve the resolution capability and the detection sensitivity of the ion mobility spectrometry, has simple method and does not need to improve the hardware of the ion mobility tube.
Drawings
Fig. 1, an ion transfer tube having a Bradbury-Nielsen type ion gate provided therein. Wherein: 1-an ion source; 2-ionization region; 3-Bradbury-Nielsen type ion gate; 3-1-a first gate electrode; 3-2-a second gate electrode; 4-migration zone; 5-an ion receiver electrode; 6-floating gas inlet; 7-sample gas inlet; and 8, an air outlet.
Fig. 2 is a timing diagram of the voltage control disclosed in the present invention for the Bradbury-Nielsen type ion gate of fig. 1. Wherein the voltage of the first gate electrode 3-1 is at V0And V2Is changed, the voltage of the second gate electrode 3-2 is at V0、V1And V2In which t is1＝0.04ms，t2＝0.2ms，t3＝10ms，V0＝ 5910V，V1＝6010V，V2＝6910V。
Fig. 3, 1 shows a timing diagram for voltage control conventionally used for Bradbury-Nielsen type ion gates. Wherein the voltage of the first gate electrode 3-1 is constant at V0The voltage of the second gate electrode 3-2 is at V0And V1In which t is1＝0.04ms，t2＝0.2ms，t3＝10ms，V0＝5910V，V1＝6010V。
FIG. 4, comparison of ion mobility spectra for 50ppb DMMP obtained at two different voltage control timings.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Example 1
An ion mobility tube using a Bradbury-Nielsen type ion gate is shown in fig. 1. Ion source 1 use of ion mobility tube63Ni, the length of an ionization region 2 is 20mm, the electric field intensity of the ionization region 2 is 60V/mm, the length of a migration region 4 is 96mm, and the electric field intensity of the migration region 4 is 60V/cm; the ion gate 3 is composed of two groups of wire electrodes which are mutually insulated, namely a first gate electrode 3-1 and a second gate electrode 3-2, the wire diameter is 0.1mm, and the wire spacing is 1 mm.
At a first predetermined time interval t1Within 0.04ms, the first gate electrode 3-1 and the second gate electrode 3-2 are simultaneously applied with the first voltage V05910V, a dc electric field is formed in the ion transfer tube in the direction of the ion source pointing to the ion receiving electrode, and ions in the ionization region enter the transfer region through the ion gate.
Within a second predetermined time interval t2The second voltage V is applied to the first gate electrode 3-1 and the second gate electrode 3-2 simultaneously for 0.2ms26910V, forming a DC electric field pointing to the direction of the ion source along the ion gate in the ionization region of the ion migration tube, the ions in the ionization region moving towards the direction of the ion source, forming a gradually weakened DC electric field pointing to the direction of the ion receiving pole along the ion gate in the migration region of the ion migration tube, and the ions entering the migration region moving towards the ion receiving pole.
Within a third predetermined time interval t3A first voltage V is applied to the first gate electrode 3-1 for 10ms05910V, and applying a third voltage V to 3-2 of the second gate electrode1Forming a direct current electric field pointing to an ion gate direction along an ion source in an ionization region of the ion migration tube, enabling ions in the ionization region to move towards the ion gate direction, forming an electric field perpendicular to the axial direction of the ion migration tube between the first gate electrode and the second gate electrode, preventing the ions in the ionization region from entering the migration region through the ion gate, forming a direct current electric field pointing to an ion receiving electrode direction along the ion gate in the migration region of the ion migration tube, and enabling the ions in the migration region to successively reach the ion receiving electrode under the action of the direct current electric field to be detected.
A first preset time t10.04ms, second predetermined time interval t20.2ms, third predetermined time interval t3Sum of 10ms and t of 10.24ms constitutes one complete time period for the ion gate to operate.
When the ion mobility tube is operated, voltages applied to the first gate electrode 3-1 and the second gate electrode 3-2 of the ion gate periodically change in a cycle of 10.24ms according to the voltage change timing shown in fig. 2.
Example 2
Fig. 4 is a spectrum (a) illustrating a spectrum of 50ppb DMMP obtained by the BNG ion gate in fig. 1 at the voltage control timing shown in fig. 2, wherein the resolving power of acetone dimer is 118 and the signal intensity is 450 pA; the resolution of DMMP was 108 and the signal intensity was 160 pA.
Example 3
To compare the advantages of the BNG ion gate voltage control timing sequence shown in fig. 2, the spectrum (b) of fig. 4 was also obtained for a BNG ion gate of 50ppb DMMP at the conventional gate voltage control timing sequence (shown in fig. 3), wherein the resolving power of the acetone dimer is 80 and the signal intensity is 140 pA; no significant DMMP ion signal was observed.

Claims (4)

1. A control method of an ion gate in an ion mobility spectrometry comprises an ion mobility tube, wherein the ion mobility tube is composed of an ion source, an ionization region, the ion gate, a migration region and an ion receiving electrode which are sequentially arranged from left to right, and is characterized in that:
the ion gate is positioned between the ionization region on the left side and the migration region on the right side;
the ion gate is formed by arranging more than 4 strip-shaped electrodes in parallel from top to bottom at intervals, wherein from top to bottom, odd strip-shaped electrodes serve as first gate electrodes, and even strip-shaped electrodes serve as second gate electrodes;
or the annular electrodes with the same geometric center are arranged at intervals from inside to outside; from inside to outside, the odd annular electrodes are used as first gate electrodes, and the even annular electrodes are used as second gate electrodes;
the first gate electrode and the second gate electrode are respectively connected with two pulse direct-current high-voltage power supplies;
applying voltages to the first gate electrode and the second gate electrode in sequence according to the time interval length of the first preset time period, the time interval length of the second preset time period and the time interval length of the third preset time period;
within the time interval length of a first preset time period, a first voltage is simultaneously applied to the first gate electrode and the second gate electrode, a direct current electric field pointing to the direction of the ion receiving electrode along the ion source is formed in the ion migration tube, and ions in the ionization region enter the migration region through the ion gate;
in the time interval length of a second preset time period, a second voltage higher than the first voltage is simultaneously applied to the first gate electrode and the second gate electrode, a direct current electric field pointing to the direction of an ion source along an ion gate is formed in an ionization region of the ion migration tube, ions in the ionization region move towards the direction of the ion source, a gradually weakened direct current electric field pointing to the direction of an ion receiving pole along the ion gate is formed in the migration region of the ion migration tube, and the ions entering the migration region move towards the ion receiving pole;
and in the time interval length of a third preset time period, a first voltage is applied to the first gate electrode, a third voltage higher than the first voltage is simultaneously applied to the second gate electrode, the third voltage is lower than the second voltage, a direct current electric field pointing to the direction of the ion gate along the ion source is formed in the ionization region of the ion migration tube, ions in the ionization region move towards the direction of the ion gate, an electric field perpendicular to the axial direction of the ion migration tube is formed between the first gate electrode and the second gate electrode, the ions in the ionization region are prevented from entering the migration region through the ion gate, a direct current electric field pointing to the direction of the ion receiving electrode along the ion gate is formed in the migration region of the ion migration tube, and the ions in the migration region sequentially reach the ion receiving electrode under the action of the direct current electric field to be detected.
2. The method of controlling an ion gate in an ion mobility spectrometry according to claim 1, wherein:
the strip-shaped electrode is a metal wire or a spiral linear electrode wound on the cylinder or a metal sheet or a metal mesh sheet;
the annular electrode is a circular ring electrode or a square ring electrode.
3. The control method according to claim 1, characterized in that:
the value of the first preset time interval is between 0.001ms and 0.2ms, the value of the second preset time interval is between 0.001ms and 1ms, and the value of the third preset time interval is between 0.2ms and 10 ms; the sum of the first, second and third preset time intervals constitutes one complete time period for the operation of the ion gate.
4. The control method according to claim 1 or 3, characterized in that: the sum of the first preset time interval, the second preset time interval and the third preset time interval forms a complete time period of the ion gate work
And when the ion migration tube works, the voltages applied to the first gate electrode and the second gate electrode of the ion gate are periodically and circularly adjusted according to the time period.
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CN112331550A (en) * 2020-11-17 2021-02-05 辽宁警察学院 Ion gate for ion mobility spectrometer and control method thereof
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CN106340436A (en) * 2015-07-08 2017-01-18 中国科学院大连化学物理研究所 Field-switching ion gate and field-switching ion gate ion migration tube
CN108091536A (en) * 2016-11-21 2018-05-29 中国科学院大连化学物理研究所 A kind of pulsed field transference tube
CN106783508A (en) * 2016-12-29 2017-05-31 同方威视技术股份有限公司 The method of transference tube and operation transference tube
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