CN118039446A - Ion gate control method for simultaneously screening and compressing multiple ions - Google Patents
Ion gate control method for simultaneously screening and compressing multiple ions Download PDFInfo
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- 150000002500 ions Chemical class 0.000 title claims abstract description 357
- 238000000034 method Methods 0.000 title claims description 19
- 238000012216 screening Methods 0.000 title claims description 10
- 239000002184 metal Substances 0.000 claims description 99
- 238000013508 migration Methods 0.000 claims description 44
- 230000005012 migration Effects 0.000 claims description 44
- 239000007789 gas Substances 0.000 claims description 26
- 238000001871 ion mobility spectroscopy Methods 0.000 claims description 12
- 238000012546 transfer Methods 0.000 claims description 5
- 230000000737 periodic effect Effects 0.000 claims description 3
- 239000012159 carrier gas Substances 0.000 claims description 2
- 239000012212 insulator Substances 0.000 claims description 2
- -1 polytetrafluoroethylene Polymers 0.000 claims description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 2
- 125000004122 cyclic group Chemical group 0.000 claims 1
- 230000037230 mobility Effects 0.000 abstract description 38
- 239000003153 chemical reaction reagent Substances 0.000 abstract description 9
- 230000007246 mechanism Effects 0.000 abstract description 6
- 238000004458 analytical method Methods 0.000 abstract description 2
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 230000005684 electric field Effects 0.000 description 6
- OSWPMRLSEDHDFF-UHFFFAOYSA-N methyl salicylate Chemical compound COC(=O)C1=CC=CC=C1O OSWPMRLSEDHDFF-UHFFFAOYSA-N 0.000 description 6
- 238000001228 spectrum Methods 0.000 description 6
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
- 238000004061 bleaching Methods 0.000 description 3
- 229960001047 methyl salicylate Drugs 0.000 description 3
- 230000004323 axial length Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- 238000004949 mass spectrometry Methods 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
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Abstract
The invention discloses a pulse voltage waveform applied to a TP-type ion gate, which periodically controls the ion gate to go through eight stages of voltage waveforms, and can screen and compress ions with multiple mobilities in an ionization region at the same time. In one cycle, reagent ions with corresponding mobility can be screened to enter a second ionization region by opening a second ion gate of the ion-molecule reaction selective control measuring device within a specific delay time; through the multiple switch of the second ion gate, a plurality of reagent ions with mobility corresponding to the reagent ions can be screened to enter the ionization region to generate the next ion-molecule reaction, which is more beneficial to the realization of the analysis of ion-molecule reaction mechanism in the ionization source under the atmospheric pressure and the sub-atmospheric pressure.
Description
Technical Field
The invention relates to a control method for an ion gate in an ion mobility spectrometry, in particular to an ion gate control method for simultaneously screening and compressing a plurality of ions in an ionization region.
Background
In recent years, an atmospheric pressure ionization source is one of research hotspots in the mass spectrometry field, and more than hundred atmospheric pressure ionization sources of different ionization mechanisms have been developed. However, the ionization mechanism and its influencing factors of these new ionization sources are not fully known by the existing research capabilities, and ion mobility spectrometry can help solve this problem.
The main mode of screening ions is selective ion flow tube mass spectrometry (SIFT-MS), which screens target ions generated in an ionization source by mass-to-charge ratio, and the screened ions enter an ion-molecule reaction tube for researching the reaction capability. However, the working air pressure of the SIFT-MS is in the mbar magnitude, the target ions are exposed core ions under the air pressure condition, and the state difference of cluster ions in the ionization source under the normal pressure condition is large, so that the experimental result is difficult to reflect the ion characteristics under the conditions of different air pressures, temperatures and concentrations in the ionization source.
In recent years, ion mobility spectrometry (IonMobilitySpectrometry, IMS) has been widely used. The IMS technology mainly characterizes various chemical substances through the mobility of gas-phase ions so as to achieve the aim of analyzing and detecting various substances. The main body part of the ion mobility spectrometer established according to the IMS technology, namely a mobility tube, mainly comprises an ionization region, an ion gate, a drift region (or a mobility region) and an ion receiving and detecting region. As the sample gas enters the ionization region, it is ionized into ions by the ionization source. The obtained sample ions enter the drift region through the periodically opened ion gate to be separated, and finally enter the ion receiving and detecting region to be received and detected. Thus, the ion gate is a major component of the ion mobility spectrometer, which primarily serves to control the flight path of the sample ions. Currently there are two major types of ion gates internationally, namely the Tyndall-Powell (TP) ion gate and the Bradbury-Nielsen (BN) ion gate. The former uses two grids arranged in parallel back and forth and applies a blocking electric field opposite to the original electric field to realize ion control, and the latter uses two groups of parallel wires which are alternately arranged at equal intervals to form a coplanar or parallel plane, and an electric field is applied between the two parallel wires to control the flight path of ions.
Under normal pressure, ion mobility spectrometry can screen cluster ions with specific mobility by controlling the delay time of ion gating, so that the reactivity and the reaction capacity of the ions can be measured in a real environment, the characteristics of the ions in electric field transmission are recognized, and atmospheric ions can be more comprehensively represented.
Patent CN114047245A provides an ion-molecule reaction control device based on ion mobility spectrometry, that is, target cluster ions with different mobility times can be screened to enter a second mobility region by controlling the delay time of a second ion gate. The reaction capability of target cluster ions and specific compounds under different experimental conditions can be studied in the second migration zone, so that the reaction mechanism of reagent ions in the normal-pressure ionization source is known, and important data and technical support are provided for analyzing the ion-molecule reaction mechanism in the atmospheric pressure and sub-atmospheric pressure ionization source.
However, the ion gating mode of the device only allows setting a delay time in one migration period, only target cluster ions with one migration rate can be selected, if a plurality of cluster ions with different migration rates generated in an ionization region need to be screened, screening can be performed only in different periods, or the delay time is increased, so that two adjacent ions with smaller migration rate difference can be screened at one time. However, this method results in low resolution of the peaks of the two ion spectra to be screened, and when the mobility of the two ions is greatly different and there are other ions between the two ions, the two ions cannot be screened individually in one period in this way.
Disclosure of Invention
Considering the defect that only single mobility ions can be screened by delaying the ion gating time in the above patent, the patent proposes a new ion gating mode based on the device of patent CN 114047245A. By setting the delay time for the second ion gate twice or more in one period, the target cluster ions with various required mobilities can be screened in one period, and the resolution of each ion spectrum peak can be improved. The method is based on a Tyndall-Powell type ion gate, can be realized only by controlling the voltage waveform of the ion gate, does not need to change the structure of the ion migration tube, and is simple.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
An ion gate control method for screening ions with multiple mobilities in one migration period is applicable to a TP ion gate in an ion-molecule reaction selective measurement device based on ion mobility spectrometry. The TP ion gate comprises two mutually parallel metal grids, the two grids are separated by an insulating material, and the thickness of the insulating material is 0.5mm. The control method of the ion gate is to apply four metal grids of the first and second ion gates and periodically control the working state of the ion gate to pass through the following eight stages.
In a first preset time interval (0 < t 1), wherein t1 represents a point in time when the high voltage on the second sheet metal grid (6-2) of the first ion gate changes from V9 to V7. In the time interval from the zero time point to t1 in the period, a high voltage V8 is applied to a first metal grid (6-1) of the first ion gate, and a high voltage V9 is applied to a second metal grid (6-2); the first metal grid (8-1) of the second ion gate is applied with high voltage V5, and the second metal grid (8-2) is applied with high voltage V6; a high voltage V2 is applied to a first metal grid (10-1) of the third ion gate, and a high voltage V3 is applied to a second metal grid (10-2); at this time, the three ion doors are in a closed state and are in a preparation state before the door opening state;
In a second preset time interval (t 1< t < t 2), wherein t2 represents the point in time when the high voltage on the second sheet metal grid (6-2) of the first ion gate changes from V7 to V9. In the time interval from t1 to t2 in the period, the voltage applied to the first metal grid mesh (6-1) of the first ion gate is unchanged, the high voltage V7 is applied to the second metal grid mesh (6-2), the first ion gate is in a door opening state, reagent ions generated in the ionization region (5) start to pass through a first migration region (7) with the length of L1 and the field intensity of E1, the voltage applied to the second ion gate and the third ion gate is kept unchanged, and the second ion gate and the third ion gate are kept in a door closing state;
In a third preset time interval (t 2< t < t 3), wherein t3 represents the point in time when the high voltage on the second sheet metal grid (8-2) of the second ion gate changes from V6 to V4. Applying a high voltage V6 to a second metal grid (6-2) of the first ion gate in a period from t2 to t 3; the voltages applied to the second ion gate and the third ion gate are kept unchanged, and at the moment, the three ion gates are all in a closed state;
In a fourth preset time interval (t 3< t < t 4), wherein t4 represents the point in time when the high voltage on the second sheet metal grid (8-2) of the second ion gate changes from V4 to V6. Applying a high voltage V4 to the first metal grid (8-1) of the second ion gate in a period from t3 to t4, wherein the second ion gate is in a door opening state, and a thin wafer-shaped reactant ion group with the mobility K1=L1/[ E1× (t 3-t 1) ] after passing through the first ion gate is selected and injected into the second ionization region (9); the voltages applied to the first ion gate and the third ion gate are kept unchanged, and the first ion gate and the third ion gate are kept in a closed state;
In a fifth preset time interval (t 4< t < t 5), wherein t5 represents the point in time when the high voltage on the second sheet metal grid (8-2) of the second ion gate changes from V6 to V4. Applying a high voltage V6 to the second metal grid (8-2) in a period from t4 to t5, wherein the voltage applied to the first metal grid (8-1) of the second ion gate is unchanged; the voltages applied to the first ion gate and the third ion gate are kept unchanged, and the three ion gates are in a closing state;
In a sixth preset time interval (t 5< t < t 6), wherein t6 represents a point in time when the high voltage on the second sheet metal grid (8-2) of the second ion gate changes from V4 to V6. Applying a high voltage V4 to a first metal grid (8-1) of the second ion gate in a period from t5 to t6, wherein the second ion gate is in a door opening state, and a thin wafer-shaped reactant ion group with the mobility K2=L1/[ E1× (t 5-t 1) ] after passing through the first ion gate is selected and injected into a second ionization region (9); the voltages applied to the first ion gate and the third ion gate are kept unchanged, and the first ion gate and the third ion gate are kept in a closed state;
In a seventh preset time interval (t 6< t < t 7), wherein t7 represents a point in time when the high voltage on the second sheet metal grid (10-2) of the third ion gate changes from V3 to V1. Applying a high voltage V6 to the second metal grid (8-2) in a period from t6 to t7 of the period, wherein the voltage applied to the first metal grid (8-1) of the second ion gate is unchanged; the voltages applied to the first ion gate and the third ion gate are kept unchanged, and the three ion gates are in a closing state. At the moment, the sample gas enters a second ionization region through a sample gas inlet (14) and reacts with the screened ions with two mobilities to obtain target product ions;
In an eighth preset time interval (t 7< t < t 8), wherein t8 represents a time point when the high voltage on the second sheet metal grid (10-2) of the third ion gate is changed from V1 to V3. In the time interval from t7 to t8 of the period, the voltage applied to the first metal grid (10-1) of the third ion gate is unchanged, the high voltage V1 is applied to the second metal grid (10-2), the third ion gate is kept in a door opening state, and product ions obtained in the second ionization region are implanted into a second migration region (11) with the length of L2 and the field intensity of E2; the voltages applied to the first and second ion gates remain unchanged, while the first and second ion gates remain closed.
The ion gate is then returned to the gating state for a first predetermined time interval, i.e., the closed state of the ion gate.
The sum of the first preset time interval and the eighth preset time interval is one switching period of the ion mobility spectrometry.
Correspondingly, the pulse voltage square waveform corresponding to the sixth preset time interval is repeated on the second ion gate, so that more than two kinds of ions with different mobilities can be screened in one period.
The first, third, fifth and seventh preset time intervals are closing times of the ion door. The third preset time interval is the time of the ions passing through the first migration zone (7), and the value of the third preset time interval is set to be 5-10 ms; the fifth preset time interval is a migration time difference value of two ions, and the value of the fifth preset time interval is set to be 1-3 ms; the seventh preset time interval is the time required by the reaction of the ions with the sample gas in the second ionization region (9), and the value of the seventh preset time interval is set to be 5-10 ms; the second, fourth, sixth and eighth preset time intervals are ion gate opening time, and the value of the second, fourth, sixth and eighth preset time intervals is set between 1 and 300us in order to ensure that ions smoothly pass through the ion gate.
V8 is the reference voltage of the position of the first metal grid (6-1) of the first ion gate; v7 is the reference voltage of the position of the second metal grid (6-2) of the first ion gate; v9 is the voltage value obtained after the second metal grid (6-2) of the first ion gate is applied with the closing voltage, the absolute value difference of V9 relative to V8 is generally 100-300V, and the voltage value range of V8 and V7 is 1-3 kV. V5 is the reference voltage of the position of the first metal grid (8-1) of the second ion gate; v4 is the reference voltage of the second ion gate at the position of the second metal grid (8-2); v6 is the voltage value obtained after the second metal grid (8-2) of the second ion gate is applied with the closing voltage, the absolute value difference of V6 relative to V5 is generally 100-300V, and the voltage value range of V5 and V4 is 4-6 kV. V2 is the reference voltage of the position of the first metal grid (10-1) of the third ion gate; v1 is the reference voltage of the position of the second metal grid (10-2) of the third ion gate; v3 is the voltage value obtained after the second metal grid (10-2) of the third ion gate is applied with the closing voltage, the absolute value difference of V3 relative to V2 is generally 100-300V, and the voltage value range of V1 and V2 is 7-10 kV.
The invention periodically controls the voltage waveform of the ion gate to pass through eight stages, and can screen and compress ions with various mobilities in the ionization region simultaneously.
The invention has the advantages that
In one cycle, reagent ions with corresponding mobility can be screened to enter a second ionization region by opening a second ion gate of the ion-molecule reaction selective control measuring device within a specific delay time; through the multiple switch of the second ion gate, a plurality of reagent ions with mobility corresponding to the reagent ions can be screened to enter the ionization region to generate the next ion-molecule reaction, which is more beneficial to the realization of the analysis of ion-molecule reaction mechanism in the ionization source under the atmospheric pressure and the sub-atmospheric pressure. The invention is described in further detail below with reference to the accompanying drawings:
Drawings
FIG. 1 shows an ion-molecule reaction selection control device with a TP-type ion gate arranged inside. Wherein: 1. a first sample gas inlet; 2. an air outlet; 3. a floating gas inlet; 4. an ultraviolet light ionization source; 5. an ionization region; 6. a first ion gate; 7. a first migration zone; 8. a second ion gate; 9. a second ionization region; 10. a third ion gate; 11. a second migration zone; 12: an electrostatic grid; 13. an ion receiving electrode; 14. a second sample gas inlet.
FIG. 2 is a timing diagram of the voltage control for the Tyndall-Powell type ion gate of FIG. 1 disclosed herein.
Fig. 3. Ion mobility spectrometry for screening two mobility ions in one cycle by increasing the open time of the second ion gate (a fourth preset time interval is increased to screen mobility spectrometry for both CO 3 - and O 2 - mobility ions).
Fig. 4. Ion mobility spectra of the same two mobility ions were screened in one cycle using the voltage control sequence of the present invention (mobility spectra of two mobility ions CO 3 - and O 2 - were screened by the control sequence in fig. 2).
Detailed Description
Example 1
The following detailed description of embodiments of the invention is merely exemplary in nature and is not intended to limit the scope of the invention or the application of the invention.
An ion transfer tube employing the disclosed ion gate control method is shown in fig. 1.
The ion mobility spectrometry used by the control method comprises an ion mobility tube formed by sequentially alternately and coaxially overlapping annular electrodes and annular insulators, wherein an ion source 4 and an ion receiving electrode 13 are respectively arranged at two ends of the ion mobility tube; a first ion gate 6, a second ion gate 8 and a third ion gate 10 are sequentially arranged in the ion migration tube along the ion migration direction, and the ion migration tube is divided into four areas by the three ion gates, wherein a first ionization area 5 is arranged between the ion source 4 and the first ion gate 6; between the first ion gate 6 and the second ion gate 8 is a first migration zone 7; between the second ion gate 8 and the third ion gate 10 is a second ionization region 9; between the third ion gate 10 and the ion receiving electrode 13 is a second migration zone 11; a carrier gas inlet 1 and a tail gas outlet 2 are arranged on the side wall surface of the area of the first ionization area 5, which is close to the ion source 4, a sample gas inlet 14 is arranged on the side wall surface of the area of the second ionization area 9, which is close to the second ion gate 8, and a drift gas inlet 3 is arranged on the side wall surface of the area of the second migration area 11, which is close to the ion receiving electrode 13; the ion gates used in the migration tube are Tyndall-Powell type ion gates, each TP type ion gate consists of two metal grids which are parallel to each other, the two metal grids are separated by an annular insulating ring (polytetrafluoroethylene insulating ring), the thickness of the insulating ring is 0.1-1 mm, the right side of a first ionization region is a first grid 6-1 of a first ion gate, the left side of the first migration region is a second grid 6-2 of the first ion gate, the right side of the first migration region is a first grid 8-1 of a second ion gate, the left side of the second ionization region is a second grid 8-2 of a second ion gate, the right side of the second ionization region is a first grid 10-1 of a third ion gate, and the left side of the second migration region is a second grid 10-2 of a third ion gate; the ion source 4 of the ion transfer tube is a VUV photoionization source of 10.6eV, the ion receiving electrode 13 is a Faraday disc with the diameter of 6mm, and the ion receiving electrode is fixed on a metal shielding cylinder with the outer diameter of 30 mm; the first ionization region 5, the first migration region 7, the second ionization region 9 and the second migration region 11 are formed by coaxially and alternately overlapping annular conductive pole pieces with the axial length of 5mm and the external diameter of 30mm and annular insulating pole pieces with the axial length of 5mm and the external diameter of 30 mm. The length of the first ionization region 5 is 30mm, the length of the first migration region 7 is 90mm, the length of the second ionization region 9 is 50mm, and the length of the second migration region 11 is 60mm; the diameter of the inner cavity of the first ionization region is 22mm, the diameter of the inner cavity of the first migration region is 20mm, the diameter of the inner cavity of the second ionization region is 18mm, and the diameter of the inner cavity of the second migration region is 16mm; the first ion gate 6, the second ion gate 8 and the third ion gate 10 are all Tyndall-Powell type ion gates, and two parallel metal grids are respectively connected with two pulse high-voltage power supplies.
The first path of bleaching gas (air) with the flow rate of 400mL/min is introduced through the bleaching gas inlet 3, the gas (air) containing 1ppmv acetone with the flow rate of 400mL/min is introduced through the first sample gas inlet 1 and enters the ionization region 5, the temperature of the ion transfer tube is 80 ℃, and the sample gas and the bleaching gas finally flow out of the ion transfer tube through the tail gas outlet 2.
The ion gate control method is a periodic pulse voltage square waveform which is respectively applied to three groups of metal grid meshes of the first, second and third ion gates, and periodically controls the ion gates to sequentially pass through the following eight working states in each period:
As shown in fig. 2, a first metal grid (6-1) of the first ion gate applies a high voltage v8=7500V and a second metal grid (6-2) applies a high voltage v9=7750V within a first preset time interval (0 < t <7 ms); the high voltage v5=4500v is applied to the first metal grid (8-1) on the second ion gate, and the high voltage v6=4750v is applied to the second metal grid (8-2); the first metal grid (10-1) of the third ion gate is applied with high voltage v2=1500v, and the second metal grid (10-2) is applied with high voltage v3=1750v. The first, second and third ion gates are in a closed state, wherein the acetone gas is ionized in the first ionization region to generate CO 3 - and O 2 - ions, and the CO 3 - and O 2 - ions stay in the first ionization region.
And a high voltage v7=7400V is applied to the second metal grid (6-2) of the first ion gate in a second preset time interval (7 ms < t <7.2 ms), and at the moment, the first ion gate is opened, and the CO 3 - and O 2 - ions are injected into the first migration region 7 by an electric field. The high voltage applied to the second and third ion gates remains unchanged while the second and third ion gates remain closed.
In a third preset time interval (7.2 ms < t <13.2 ms), high voltage v9=7750V is applied to the second metal grid (6-2) of the first ion gate, the high voltage applied to the second and third ion gates is kept unchanged, and at the moment, the first, second and third ion gates are kept in a closed state, and at the moment, the CO 3 - and O 2 - ions are driven to migrate towards the second ion gate 10 by an electric field in the first migration zone.
In a fourth preset time interval (13.2 ms < t <13.4 ms), the high voltage applied to the first metal grid (8-1) of the second ion gate is kept unchanged, the high voltage v4=4400V is applied to the second metal grid (8-2), at this time, the CO 3 - ions with larger mobility enter the second ionization region 9, the high voltage applied to the first and third ion gates is kept unchanged, and the first and third ion gates are kept closed.
In a fifth preset time interval (13.4 ms < t <14.4 ms), the high voltage applied to the first metal grid (8-1) of the second ion gate is kept unchanged, the high voltage v6=4750v is applied to the second metal grid (8-2), the second ion gate is in a closed state, the high voltage applied to the first ion gate and the third ion gate is kept unchanged, and the first ion gate and the third ion gate are kept in a closed state.
In a sixth preset time interval (14.4 ms < t <14.6 ms), the high voltage applied to the first metal grid (8-1) of the second ion gate is kept unchanged, the high voltage v4=4400V is applied to the second metal grid (8-2), at this time, the O 2 - ions with smaller mobility enter the second ionization region 9, the high voltage applied to the first and third ion gates is kept unchanged, the first and third ion gates are kept in a closed state, and at this time, if no sample gas is introduced into the second sample gas inlet 14, the mobility spectrum of two reagent ions can be directly obtained, as shown in fig. 4.
In a seventh preset time interval (14.6 ms < t <20.6 ms), the high voltage applied to the first metal grid (8-1) of the second ion gate is kept unchanged, the high voltage v6=4750v is applied to the second metal grid (8-2), the second ion gate is in a closed state, the high voltage applied to the first and third ion gates is kept unchanged, and the first and third ion gates are kept in a closed state. 400mL/min of a gas (air) containing 1ppmv methyl salicylate was introduced into the second ionization zone 9 at the second sample gas inlet 14, and reacted with CO 3 - and O 2 - ions to obtain product ions of methyl salicylate.
In an eighth preset time interval (20.6 ms < t <20.8 ms), the high voltage applied to the first metal grid (10-1) of the third ion gate is kept unchanged, the high voltage v1=1400V is applied to the second metal grid (10-2), at the moment, the third ion gate is opened, product ions of methyl salicylate are injected into the second migration zone 11, the high voltage applied to the first and second ion gates is kept unchanged, and the first and second ion gates are kept closed.
The ion gate control method in the fourth preset time interval is repeated on the second ion gate twice (namely, the fourth preset time interval and the sixth preset time interval), so that the single screening of the ions with the two mobilities of CO 3 - and O 2 - in one period can be realized, and the like, the ion gate control method in the fourth preset time interval is repeated on the second ion gate three times, so that the single screening of the ions with the three mobilities in one period can be realized, and therefore, the number of times of the ion gate control method in the fourth preset time interval is the number of the kinds of the ion with the mobility which can be screened in one period.
The control procedure and conditions are the same as above, except that the ion gate control method in the sixth preset time interval is removed, and only the length of the fourth preset time interval is increased from 200us to 400us, so that the ions with both mobility of CO 3 - and O 2 - are screened at the same time, and the resolution of the obtained spectrum peak is greatly reduced due to the excessively long gate opening time, and the result is shown in fig. 3.
Claims (4)
1. An ion gate control method for screening and compressing multiple ions simultaneously, wherein an ion mobility spectrometry used by the control method comprises an ion mobility tube formed by sequentially alternately and coaxially overlapping a circular electrode and a circular insulator, and an ion source (4) and an ion receiving electrode (13) are respectively arranged at two ends of the ion mobility tube; a first ion gate (6), a second ion gate (8) and a third ion gate (10) are sequentially arranged in the ion migration tube along the ion migration direction, the ion migration tube is divided into four areas by the three ion gates, and a first ionization area (5) is arranged between the ion source (4) and the first ion gate (6); a first migration zone (7) is arranged between the first ion gate (6) and the second ion gate (8); a second ionization region (9) is arranged between the second ion gate (8) and the third ion gate (10); a second migration zone (11) is arranged between the third ion gate (10) and the ion receiving electrode (13); a carrier gas inlet (1) and a tail gas outlet (2) are arranged on the side wall surface, close to the ion source (4), of the area where the first ionization area (5) is located, a sample gas inlet (14) is arranged on the side wall surface, close to the second ion gate (8), of the area where the second ionization area (9) is located, and a drift gas inlet (3) is arranged on the side wall surface, close to the ion receiving electrode (13), of the area where the second migration area (11) is located; the ion gates used in the migration tube are Tyndall-Powell type ion gates, each TP type ion gate consists of two mutually parallel metal grids, the two metal grids are separated by an annular insulating ring (polytetrafluoroethylene insulating ring), the thickness of the insulating ring is 0.1-1 mm, the right side of a first ionization region is a first grid (6-1) of a first ion gate, the left side of the first migration region is a second grid (6-2) of the first ion gate, the right side of the first migration region is a first grid (8-1) of a second ion gate, the left side of the second ionization region is a second grid (8-2) of a second ion gate, the right side of the second ionization region is a first grid (10-1) of a third ion gate, and the left side of the second migration region is a second grid (10-2) of the third ion gate; the ion gate control method is a periodic pulse voltage square waveform which is respectively applied to three groups of metal grid meshes of the first, second and third ion gates, and periodically controls the ion gates to sequentially pass through the following eight working states in each period:
In a first preset time interval t (0 < t 1), wherein t1 represents a time point when the high voltage on the second sheet metal grid (6-2) of the first ion gate is changed from V9 to V7; in the time interval from the zero time point to t1 in the period, a high voltage V8 is applied to a first metal grid (6-1) of the first ion gate, and a high voltage V9 is applied to a second metal grid (6-2); the first metal grid (8-1) of the second ion gate is applied with high voltage V5, and the second metal grid (8-2) is applied with high voltage V6; a high voltage V2 is applied to a first metal grid (10-1) of the third ion gate, and a high voltage V3 is applied to a second metal grid (10-2); at this time, all three ion doors are in a closed state;
Within a second preset time interval t (t 1< t < t 2), wherein t2 represents the point in time when the high voltage on the second sheet metal grid (6-2) of the first ion gate changes from V7 to V9; in the time interval from t1 to t2 in the period, the voltage applied to the first metal grid (6-1) of the first ion gate is unchanged, and the high voltage V7 is applied to the second metal grid (6-2), so that the first ion gate is in a door opening state; the voltages applied to the second ion gate and the third ion gate are kept unchanged, and the second ion gate and the third ion gate are kept in a closed state;
Within a third preset time interval t (t 2< t < t 3), wherein t3 represents the point in time when the high voltage on the second sheet metal grid (8-2) of the second ion gate changes from V6 to V4; applying a high voltage V6 to a second metal grid (6-2) of the first ion gate in a period from t2 to t 3; the voltages applied to the second ion gate and the third ion gate are kept unchanged, and at the moment, the three ion gates are all in a closed state;
In a fourth preset time interval t (t 3< t < t 4), wherein t4 represents the point in time when the high voltage on the second sheet metal grid (8-2) of the second ion gate changes from V4 to V6; in the time interval from t3 to t4 of the period, the voltage applied to the first metal grid (8-1) of the second ion gate is unchanged, and the high voltage V4 is applied to the second metal grid (8-2), so that the second ion gate is in a door opening state; the voltages applied to the first ion gate and the third ion gate are kept unchanged, and the first ion gate and the third ion gate are kept in a closed state;
Within a fifth preset time interval t (t 4< t < t 5), wherein t5 represents the point in time when the high voltage on the second sheet metal grid (8-2) of the second ion gate changes from V6 to V4; applying a high voltage V6 to the second metal grid (8-2) in a period from t4 to t5, wherein the voltage applied to the first metal grid (8-1) of the second ion gate is unchanged; the voltages applied to the first ion gate and the third ion gate are kept unchanged, and the three ion gates are in a closing state;
Within a sixth preset time interval t (t 5< t < t 6), wherein t6 represents the point in time when the high voltage on the second sheet metal grid (8-2) of the second ion gate changes from V4 to V6; in the time interval from t5 to t6 of the period, the voltage applied to the first metal grid (8-1) of the second ion gate is unchanged, and the second metal grid (8-2) is applied with high voltage V4, so that the second ion gate is in a door opening state; the voltages applied to the first ion gate and the third ion gate are kept unchanged, and the first ion gate and the third ion gate are kept in a closed state;
Within a seventh preset time interval t (t 6< t < t 7), wherein t7 represents the point in time when the high voltage on the second sheet metal grid (10-2) of the third ion gate changes from V3 to V1; applying a high voltage V6 to the second metal grid (8-2) in a period from t6 to t7 of the period, wherein the voltage applied to the first metal grid (8-1) of the second ion gate is unchanged; the voltages applied to the first ion gate and the third ion gate are kept unchanged, and the three ion gates are in a closing state;
Within an eighth preset time interval t (t 7< t < t 8), wherein t8 represents a point in time when the high voltage on the second sheet metal grid (10-2) of the third ion gate changes from V1 to V3; in the time interval from t7 to t8 of the period, the voltage applied to the first metal grid (10-1) of the third ion gate is unchanged, the high voltage V1 is applied to the second metal grid (10-2), and the third ion gate is kept in a door opening state; the voltages applied to the first and second ion gates remain unchanged, while the first and second ion gates remain closed.
2. The pulse voltage square waveform according to claim 1, wherein: the time from the first preset time interval to the eighth preset time interval and the primary switching period of the ion mobility spectrometry are respectively; when the ion transfer tube works, the three groups of metal grids of the first, second and third ion gates respectively carry out periodic cyclic adjustment according to the pulse voltage square wave waveform.
3. The pulse voltage square waveform of claim 1, wherein: the first, third, fifth and seventh preset time intervals are closing times of the ion door; the third preset time interval is the time of the ions passing through the first migration zone (7), and the value of the third preset time interval is set to be 5-10 ms; the fifth preset time interval is a migration time difference value of two ions, and the value of the fifth preset time interval is set to be 1-3 ms; the seventh preset time interval is the time required by the reaction of the ions with the sample gas in the second ionization region (9), and the value of the seventh preset time interval is set to be 5-10 ms; the second, fourth, sixth and eighth preset time intervals are ion gate opening time, and the value of the second, fourth, sixth and eighth preset time intervals is set between 1 and 300us in order to ensure that ions smoothly pass through the ion gate.
4. The pulse voltage waveform of claim 1, wherein:
V8 is the reference voltage of the position of the first metal grid (6-1) of the first ion gate; v7 is the reference voltage of the position of the second metal grid (6-2) of the first ion gate; v9 is the voltage value obtained after the second metal grid (6-2) of the first ion gate is applied with the closing voltage, the difference between the absolute value of V9 and the absolute value of V8 is generally 100-300V, and the voltage value range of V8 and V7 is 1-3 kV;
V5 is the reference voltage of the position of the first metal grid (8-1) of the second ion gate; v4 is the reference voltage of the second ion gate at the position of the second metal grid (8-2); v6 is the voltage value obtained after the second metal grid mesh (8-2) of the second ion gate applies the closing voltage, the absolute value difference of V6 relative to V5 is generally 100-300V, and the voltage value range of V5 and V4 is 4-6 kV;
V2 is the reference voltage of the position of the first metal grid (10-1) of the third ion gate; v1 is the reference voltage of the position of the second metal grid (10-2) of the third ion gate; v3 is the voltage value obtained after the second metal grid (10-2) of the third ion gate is applied with the closing voltage, the absolute value difference of V3 relative to V2 is generally 100-300V, and the voltage value range of V1 and V2 is 7-10 kV.
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