CN114068289B - Electrospray ionization source and application - Google Patents
Electrospray ionization source and application Download PDFInfo
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- CN114068289B CN114068289B CN202111402695.2A CN202111402695A CN114068289B CN 114068289 B CN114068289 B CN 114068289B CN 202111402695 A CN202111402695 A CN 202111402695A CN 114068289 B CN114068289 B CN 114068289B
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- 238000000132 electrospray ionisation Methods 0.000 title claims abstract description 42
- 239000007921 spray Substances 0.000 claims abstract description 105
- 238000001871 ion mobility spectroscopy Methods 0.000 claims abstract description 39
- 230000010287 polarization Effects 0.000 claims abstract description 32
- 230000005684 electric field Effects 0.000 claims abstract description 20
- 238000004811 liquid chromatography Methods 0.000 claims abstract description 18
- 150000002500 ions Chemical class 0.000 claims description 70
- 239000007788 liquid Substances 0.000 claims description 15
- 238000009413 insulation Methods 0.000 claims description 12
- 239000002184 metal Substances 0.000 claims description 7
- 238000010926 purge Methods 0.000 claims description 5
- 238000007789 sealing Methods 0.000 claims description 3
- 239000012212 insulator Substances 0.000 claims description 2
- 230000002093 peripheral effect Effects 0.000 claims 1
- 239000011148 porous material Substances 0.000 abstract description 6
- 238000005516 engineering process Methods 0.000 abstract description 5
- 238000001704 evaporation Methods 0.000 abstract description 4
- 230000008020 evaporation Effects 0.000 abstract description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 21
- 238000013508 migration Methods 0.000 description 13
- 230000005012 migration Effects 0.000 description 13
- 239000000243 solution Substances 0.000 description 11
- 238000001228 spectrum Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 7
- 239000000523 sample Substances 0.000 description 7
- 238000001514 detection method Methods 0.000 description 5
- 238000005507 spraying Methods 0.000 description 5
- 230000004323 axial length Effects 0.000 description 4
- HQABUPZFAYXKJW-UHFFFAOYSA-N butan-1-amine Chemical compound CCCCN HQABUPZFAYXKJW-UHFFFAOYSA-N 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 4
- ZPUCINDJVBIVPJ-LJISPDSOSA-N cocaine Chemical compound O([C@H]1C[C@@H]2CC[C@@H](N2C)[C@H]1C(=O)OC)C(=O)C1=CC=CC=C1 ZPUCINDJVBIVPJ-LJISPDSOSA-N 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- XTAZYLNFDRKIHJ-UHFFFAOYSA-N n,n-dioctyloctan-1-amine Chemical compound CCCCCCCCN(CCCCCCCC)CCCCCCCC XTAZYLNFDRKIHJ-UHFFFAOYSA-N 0.000 description 4
- OEQRFVAXHJVQAJ-UHFFFAOYSA-N n,n-dioctyloctan-1-amine;methanol Chemical compound OC.CCCCCCCCN(CCCCCCCC)CCCCCCCC OEQRFVAXHJVQAJ-UHFFFAOYSA-N 0.000 description 4
- 230000035945 sensitivity Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 3
- 239000012488 sample solution Substances 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 239000003643 water by type Substances 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000004061 bleaching Methods 0.000 description 2
- 229960003920 cocaine Drugs 0.000 description 2
- HPNMFZURTQLUMO-UHFFFAOYSA-N diethylamine Chemical compound CCNCC HPNMFZURTQLUMO-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000007667 floating Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- MYWUZJCMWCOHBA-VIFPVBQESA-N methamphetamine Chemical compound CN[C@@H](C)CC1=CC=CC=C1 MYWUZJCMWCOHBA-VIFPVBQESA-N 0.000 description 2
- 229960001252 methamphetamine Drugs 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- BNRNXUUZRGQAQC-UHFFFAOYSA-N sildenafil Chemical compound CCCC1=NN(C)C(C(N2)=O)=C1N=C2C(C(=CC=1)OCC)=CC=1S(=O)(=O)N1CCN(C)CC1 BNRNXUUZRGQAQC-UHFFFAOYSA-N 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- IMFACGCPASFAPR-UHFFFAOYSA-N tributylamine Chemical compound CCCCN(CCCC)CCCC IMFACGCPASFAPR-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 229960001399 clenbuterol hydrochloride Drugs 0.000 description 1
- OPXKTCUYRHXSBK-UHFFFAOYSA-N clenbuterol hydrochloride Chemical compound Cl.CC(C)(C)NCC(O)C1=CC(Cl)=C(N)C(Cl)=C1 OPXKTCUYRHXSBK-UHFFFAOYSA-N 0.000 description 1
- 238000010219 correlation analysis Methods 0.000 description 1
- 238000004807 desolvation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000013467 fragmentation Methods 0.000 description 1
- 238000006062 fragmentation reaction Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004949 mass spectrometry Methods 0.000 description 1
- GBMDVOWEEQVZKZ-UHFFFAOYSA-N methanol;hydrate Chemical compound O.OC GBMDVOWEEQVZKZ-UHFFFAOYSA-N 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229960003310 sildenafil Drugs 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000009941 weaving Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/10—Ion sources; Ion guns
- H01J49/16—Ion sources; Ion guns using surface ionisation, e.g. field-, thermionic- or photo-emission
- H01J49/165—Electrospray ionisation
-
- G—PHYSICS
- 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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/62—Detectors specially adapted therefor
- G01N30/72—Mass spectrometers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/10—Ion sources; Ion guns
- H01J49/16—Ion sources; Ion guns using surface ionisation, e.g. field-, thermionic- or photo-emission
- H01J49/165—Electrospray ionisation
- H01J49/167—Capillaries and nozzles specially adapted therefor
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- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Immunology (AREA)
- Engineering & Computer Science (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Pathology (AREA)
- Plasma & Fusion (AREA)
- Life Sciences & Earth Sciences (AREA)
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- Chemical Kinetics & Catalysis (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
- Electron Tubes For Measurement (AREA)
Abstract
The invention provides an electrospray ionization source. In the electrospray ionization source, a capillary spray needle is coaxially arranged in an airflow micro-pore channel with high-flow-rate gas introduced therein and is sealed and fixed, so that sheath flow gas auxiliary electrospray is constructed, and stable electrospray ion flow is generated; meanwhile, the high-flow-rate gas in the airflow micro-pore channel also cools the spray tip of the capillary spray needle, so that the phenomenon of stopping electrospray due to evaporation of spray solution in the capillary spray needle in high-temperature atmosphere is avoided; the charged atomized droplets generated by the capillary spray needle are further introduced into a high-intensity direct-current polarized electric field to carry out secondary polarized ionization, and the charged atomized droplets are broken into charged atomized tiny droplets with smaller size and more charged quantity, so that the charged atomized tiny droplets are easier to completely desolvate, and the ionization efficiency of a target sample is improved. The electrospray ionization source disclosed by the invention combines two technologies of sheath gas assisted electrospray and strong electric field polarization ionization, has the advantages of stable spray, high-temperature atmosphere resistance, high ionization efficiency and the like, and is suitable for the combination of liquid chromatography and ion mobility spectrometry.
Description
Technical Field
The invention relates to an ionization source of ion mobility spectrometry, in particular to an electrospray ionization source combining sheath flow gas auxiliary spraying and strong electric field polarization ionization.
Background
Electrospray ionization sources are an ion source technology of paramount importance in the field of ion mobility spectrometry. Its advent has made it possible to analyze liquid samples directly by ion mobility spectrometry, and has further driven the advent and development of techniques for liquid chromatography and ion mobility spectrometry. Hill et al used electrospray ionization source ion mobility spectrometry for the first time in 1994 as a detector for liquid chromatography (J. Microcol. Sep.,1994, 6:515). In electrospray ionization source ion mobility spectrometry, to desolvate the spotted atomized droplets produced by the electrospray ionization source efficiently, ion mobility spectrometry needs to operate above 150 ℃, and electrospray ionization sources need special structural designs to keep the capillary spray needles cool, such as the cross-flow structures proposed by Hill et al (j. Microcol. Sep.,1994, 6:515) and KHAYAMIAN et al (anal. Chem.,2007, 79:3199). These designs have solved to some extent that electrospray stopping occurs due to evaporation of the spray solution in the capillary spray needle in a high temperature atmosphere, but the stability of the electrospray ion flow is poor. In addition, because the flow rate of the spray solution is usually in the order of mu L/min, the size of the atomized droplets with points is large, and the ionization efficiency of the target object is low.
To increase the ionization efficiency of electrospray ionization sources, wilm and Mann developed nanoliter electrospray techniques (anal. Chem.,1996, 68:1). On the basis, liu Wenjie et al use a multi-nozzle array nano-liter electrospray ionization source in an ion mobility spectrometry technology, so that the detection sensitivity of medicines such as sildenafil, clenbuterol hydrochloride and the like is effectively improved (Chinese J.Anal.chem.,2015, 43:788). However, the multi-nozzle array nano-liter electrospray ionization source has a complex structure and is inconvenient to be matched with an ion migration tube. In addition, the nanoliter electrospray needle tip opening is usually 20 μm or less, clogging is extremely likely to occur, and the practicability for a long-term correlation analysis system is poor.
Beauchamp et al developed a field-induced droplet ionization technique in 2003 and successfully applied it to mass spectrometry (J.Phys.chem., 2003, 107:14161). If the technology is combined with electrospray, the charged atomized droplets generated by electrospray are expected to be subjected to deep polarization ionization, so that the ionization efficiency of a target sample is improved.
Disclosure of Invention
The present invention provides an electrospray ionization source for ion mobility spectrometry. In an electrospray ionization source, a capillary spray needle is coaxially arranged in an airflow micro-pore channel with high-flow-rate gas introduced therein and is sealed and fixed at one end, so that sheath flow gas auxiliary electrospray is constructed, and stable electrospray ion flow is generated; meanwhile, the high-flow-rate gas in the airflow micro-pore channel also cools the spray tip of the capillary spray needle, so that the phenomenon of stopping electrospray due to evaporation of spray solution in the capillary spray needle in high-temperature atmosphere is avoided; the charged atomized droplets generated by the capillary spray needle are further introduced into a high-intensity direct-current polarized electric field to carry out secondary polarized ionization, and the charged atomized droplets are broken into charged atomized tiny droplets with smaller size and more charged quantity, so that the charged atomized tiny droplets are easier to completely desolvate, and the ionization efficiency of a target sample is improved.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
an electrospray ionization source comprises a capillary spray needle, an ion focusing electrode, a spray counter electrode and a field polarization electrode;
The capillary spray needle is a capillary tube with an axial through hole, the ion focusing electrode is a cylindrical barrel with a closed left end and an open right end, the left side bottom surface in the barrel is hemispherical, the hemispherical bottom surface is coaxial with the barrel, a through hole A is formed in the hemispherical bottom surface along the axial direction, one end of the capillary spray needle penetrates through the through hole and extends into the barrel, the other end of the capillary spray needle is positioned outside the barrel, the open end of the capillary spray needle in the barrel is coaxial with the ion focusing electrode, an air inlet for introducing sheath gas is formed in the cylindrical side wall at the left end of the ion focusing electrode, the air inlet is communicated with the axial through hole A of the ion focusing electrode, and a through hole serving as an air outlet is formed in the hemispherical bottom surface at the left side in the barrel;
two flat-plate spray counter electrodes and field polarization electrodes which are arranged in parallel and are spaced from each other and provided with through holes in the middle are arranged in the cylindrical ion focusing electrode, the surfaces of the spray counter electrodes and the field polarization electrode plates are perpendicular to the axis of the cylinder, the spray counter electrodes are positioned between the capillary spray needles and the field polarization electrodes, sheet metal grid meshes capable of passing ions are arranged at the through holes in the middle of the spray counter electrodes and the field polarization electrodes, and the through holes in the middle of the spray counter electrodes and the field polarization electrodes are coaxial with the capillary spray needles; the axis of the through hole is vertical to the surface of the flaky grid;
The periphery edges of the plate bodies of the spray counter electrode and the field polarized electrode are respectively connected with the inner wall surface of the ion focusing electrode in a sealing way through annular insulators;
The method comprises the steps of applying direct-current voltages with the same polarity and sequentially increased voltage values to a field polarization electrode, a spray counter electrode, an ion focusing electrode and a capillary spray needle, forming a direct-current polarization electric field with the field intensity higher than 1000V/cm between the field polarization electrode and the spray counter electrode, and carrying out fragmentation and secondary polarization ionization on charged atomized liquid drops generated by the capillary spray needle;
the spray tip of the capillary spray needle passes through the axial through hole of the cylindrical ion focusing electrode and extends to the middle part in the cylinder body after passing through the hemispherical bottom surface;
The left end of the cylindrical ion focusing electrode is provided with a heat insulation block body, the heat insulation block body is in airtight connection with the outer wall surface of the left end of the ion focusing electrode, meanwhile, the heat insulation block body seals a through hole on the hemispherical bottom surface through which a capillary spray needle passes, and the capillary spray needle passes through the heat insulation block body and then extends into the cylinder body;
The air outlets are uniformly distributed along the same radial section of the hemispherical bottom surface, and the number of the air outlets is more than 2;
The electrospray ionization source is used as an ion source of an ion mobility spectrometry, and the field polarization electrode is used as a first electrode of an ion mobility spectrometry ionization region along the direction from the ionization source to an ion receiving electrode; one end of a capillary spray needle through hole positioned outside the ion focusing electrode is connected with a mobile phase outlet of the liquid chromatography column, and the liquid chromatography is combined with the ion mobility spectrometry;
When the liquid chromatography and ion mobility spectrometry combined device works, the flow rate of the liquid chromatography mobile phase is adjustable between 0.1 and 500 mu L/min;
One path of sheath flow gas in the ion mobility spectrometry enters an axial through hole at the left end of an ion focusing electrode through an air inlet, a sheath layer with the section flow velocity higher than 30m/s is formed between the outer wall surface of a capillary spray needle and the inner wall surface of the axial through hole, the spray tip of the capillary spray needle is cooled, the spray tip of the capillary spray needle is assisted to form stable electrospray, and high-temperature drift gas in the ion mobility spectrometry is used as a purge gas to flow out of the ion mobility spectrometry through a field polarized electrode and a grid mesh at the middle part of a spray counter electrode.
The invention has the advantages that:
in the electrospray ionization source disclosed by the invention, the problems of poor stability and poor high-temperature atmosphere resistance of a conventional electrospray ion source in an ion mobility spectrometry are effectively solved by adopting a sheath flow gas auxiliary electrospray mode; through introducing a strong direct-current polarized electric field, the charged atomized droplets are cracked and proliferated in charge quantity, so that complete desolvation of the charged atomized droplets is easier to realize, and the ionization efficiency of a target sample is improved. The electrospray ionization source disclosed by the invention provides an effective technical path for the combination of liquid chromatography and ion mobility spectrometry.
Drawings
The invention is described in further detail below with reference to the accompanying drawings:
FIG. 1 shows a liquid chromatography and ion mobility spectrometry combined device constructed based on the electrospray ionization source disclosed by the invention. Wherein: (1) a capillary spray needle; (2) an ion focusing electrode; (3) spraying a counter electrode; (4) a field polarized electrode; (5) ceramic insulation blocks; (6) a sheath flow gas inlet; (7) an air outlet; (8) bleaching gas; (9) an ionization region; (10) a Bradbury-Nielsen type ion gate; (11) a migration zone; (12) an ion receiving electrode; (13) liquid chromatograph.
FIG. 2 shows the effective effect of DC polarized electric field in electrospray ionization source on improving target detection sensitivity. Wherein: curve (a) is the product ion spectrum formed by 0.5ng/mL trioctylamine methanol solution in a liquid chromatography and ion mobility spectrometry combined device when the direct current electric field between the spray counter electrode 3 and the field polarized electrode 4 is 2000V/cm; curve (b) is the product ion spectrum of 0.5ng/mL trioctylamine methanol solution formed in a liquid chromatography and ion mobility spectrometry combined device when the dc electric field intensity between the spray counter electrode 3 and the field polarized electrode 4 was 250V/cm. The liquid chromatography sample injection amount was 10. Mu.L, the mobile phase was 4:1 methanol water, and the mobile phase flow rate was set to 10. Mu.L/min.
FIG. 3, using trioctylamine, cocaine, tributylamine, methamphetamine, butylamine, diethylamine to prepare a mixed sample solution with a concentration of 1ng/mL, the solvent being methanol; and taking 10 mu L of mixed sample solution for sample injection, and forming a two-dimensional response spectrogram in a liquid chromatography and ion mobility spectrometry combined device.
FIG. 4 is a schematic diagram of the structure of the electrospray ionization source in a liquid chromatography-ion mobility spectrometry combined device. Wherein: (1) a capillary spray needle; (2) an ion focusing electrode; (3) spraying a counter electrode; (4) a field polarized electrode; (5) ceramic insulation blocks; (6) a sheath flow gas inlet; (7) an air outlet; (8) bleaching gas.
Detailed Description
Example 1
A liquid chromatography-ion mobility spectrometry combined device constructed based on the electrospray ionization source disclosed by the invention is shown in figure 1.
The electrospray ionization source consists of a capillary spray needle 1, an ion focusing electrode 2, a spray counter electrode 3, a field polarization electrode 4 and a ceramic thermal insulation block 5.
The capillary spray needle 1 is a quartz capillary with an outer diameter of 360 mu m and an inner diameter of 150 mu m; the ion focusing electrode 2 is a metal cylindrical electrode with the outer diameter of 30mm and the axial length of 50 mm; the left end and the right end of the ion focusing electrode 2 are sealed, the diameter of the hemispherical inner bottom surface of the sealed end is 18mm, the sealed end is provided with an axial through hole with the diameter of 750 mu m, the capillary spray needle 1 is coaxially matched with the axial through hole in a sealing way through a ceramic heat insulation block 5, the axial through hole is communicated with a sheath gas inlet 6 with the diameter of 3mm, which is arranged at the left end of the ion focusing electrode 2, on the hemispherical inner bottom surface of the sealed end of the ion focusing electrode 2, 4 through holes with the diameter of 3mm, namely gas outlets 7, are uniformly distributed on the radial section of the position of 1/2 of the spherical radius and serve as outlets of reverse purge gas in an electrospray ionization source.
The spray counter electrode 3 and the field polarized electrode 4 are annular conductive electrodes with the outer diameter of 30mm, the inner diameter of 18mm and the axial length of 2mm, square hole metal grid meshes with the thickness of 0.5mm are welded in the electrodes, the side length of each square hole is 1mm, and the diameter of each grid wire is 0.5mm. The ion focusing electrode 2, the spray counter electrode 3 and the field polarization electrode 4 are sequentially and coaxially sealed and matched through a tetrafluoro insulating ring with the outer diameter of 30mm, the inner diameter of 18mm and the thickness of 5mm. The axial distance between the spray tip of the capillary spray needle 1 and the spray counter electrode 3 is 5mm, and a 4000V voltage difference is kept between the two; the axial distance between the spray counter electrode 3 and the field polarization electrode 4 is 5mm, and a direct-current polarization electric field of 2000V/cm is arranged between the spray counter electrode and the field polarization electrode.
The ion gate 10 is a Bradbury-Nielsen type ion gate, which is formed by weaving metal wires with the diameter of 0.05mm on a tetrafluoroPCB polar plate, the wire spacing is 0.3mm, the metal wires on the ion gate are divided into two groups which are mutually insulated and are respectively connected with two pulse high-voltage power supplies, and the opening time of the ion gate is set to be 150 mu s; the ion receiving electrode 12 is a faraday disk having a diameter of 6mm and is fixed to a metal shield having an outer diameter of 30 mm.
The ionization region 9 and the migration region 11 are formed by alternately overlapping annular conductive pole pieces with the axial length of 5mm, the inner diameter of 18mm and the outer diameter of 30mm and annular insulating pole pieces with the axial length of 5mm, the inner diameter of 18mm and the outer diameter of 30mm, the length of the ionization region 2 is 30mm, the length of the migration region 11 is 75mm, and an axial uniform direct current electric field of 250V/cm is arranged in the ionization region 9 and the migration region 11.
The temperature of the ion migration tube is 150 ℃, zero air with a path of floating gas of 500mL/min enters the ion migration tube through a floating gas inlet 8, sequentially purges a migration zone 11 and an ionization zone 9, then enters an electrospray ionization source 1 through a field polarization electrode 4 and a circular grid mesh in the middle of a spray counter electrode 3, purges the electrospray ionization source 1, and finally flows out of an ion migration spectrum through an air outlet 7 together with 2000mL/min sheath gas introduced through a sheath gas inlet 6.
The liquid chromatograph 13 is any commercially available liquid chromatograph. The mobile phase flowing out of the chromatographic column of the liquid chromatograph 13 enters the capillary spray needle 1, charged atomized droplets are generated at the spray tip of the capillary spray needle 1, the charged atomized droplets are broken into charged atomized micro droplets with smaller size and more charge under the action of a direct-current polarized electric field between the spray counter electrode 3 and the field polarized electrode 4, and then the charged atomized micro droplets enter an ion mobility spectrometry for separation and detection, so that a high-sensitivity ion mobility spectrometry with the ion intensity corresponding to the migration time is formed.
Example 2
In the combined apparatus disclosed in example 1, the liquid chromatograph 13 was adapted to a Waters C18 column (5 μm,4.6x100 mm,XTerra TM) using PU-1580 from Jasco company, and the mobile phase was a 4:1 aqueous methanol solution at a flow rate of 10. Mu.L/min. The operating temperature of the ion transfer tube was 150 ℃.
In order to demonstrate the capability of the design of sheath flow auxiliary spraying in improving the high-temperature atmosphere resistance of the electrospray ionization source in the electrospray ionization source disclosed by the invention, the stability of an ion mobility spectrum formed by a 4:1 methanol aqueous solution mobile phase in a liquid chromatography-ion mobility spectrum combined device is firstly obtained when the flow rate of the sheath flow gas is 2000mL/min in the experimental process. The results showed that no electrospray stopping phenomenon occurred within 2 hours, and the relative standard deviation RSD of the peak intensities in the ion mobility spectrogram formed by the mobile phase was-0.5%.
In the experimental process, the stability of the ion mobility spectrometry formed by the 4:1 methanol aqueous solution mobile phase in the liquid chromatography-ion mobility spectrometry combined device is also obtained when the sheath flow gas flow rate is 0 mL/min. The results show that the electrospray stop-spray phenomenon occurs for 20 times within 2 hours, and the relative standard deviation RSD of the spectrum peak intensity reaches 70% in an ion mobility spectrogram formed by the mobile phase.
Obviously, in the electrospray ionization source disclosed by the invention, the design of sheath flow auxiliary spraying can effectively improve the capability of the electrospray ionization source to resist the high-temperature atmosphere inside the ion migration tube.
Example 3
In the combined apparatus disclosed in example 1, the liquid chromatograph 13 was adapted to a Waters C18 column (5 μm,4.6x100 mm,XTerra TM) using PU-1580 from Jasco company, and the mobile phase was a 4:1 aqueous methanol solution at a flow rate of 10. Mu.L/min. The operating temperature of the ion transfer tube was 150 ℃.
In order to demonstrate the effective effect of the direct-current polarized electric field on improving the detection sensitivity of the target in the electrospray ionization source disclosed by the invention, in the experimental process, firstly, a product ion spectrum formed by 0.5ng/mL trioctylamine methanol solution in a liquid chromatography-ion mobility spectrometry combined device when the direct-current electric field strength between the spray counter electrode 3 and the field polarized electrode 4 is 2000V/cm is obtained, as shown in fig. 2 a. Wherein, trioctylamine forms a product ion peak with current intensity of 150pA at the migration time of 30.2 ms.
During the experiment, the product ion spectrum formed by 0.5ng/mL trioctylamine methanol solution in the ion mobility spectrometry of the electrospray ionization source is also obtained when the direct current electric field intensity between the spray counter electrode 3 and the field polarization electrode 4 is 250V/cm (consistent with the electric fields in the ionization region 9 and the migration region 11), as shown in fig. 2 b. Wherein no product ion peak of trioctylamine was observed.
Obviously, in the electrospray ionization source disclosed by the invention, the application of the direct-current polarized electric field can effectively improve the detection sensitivity of the target.
Example 4
In the combined apparatus disclosed in example 1, the liquid chromatograph 13 was adapted to a Waters C18 column (5 μm,4.6x100 mm,XTerra TM) using PU-1580 from Jasco company, and the mobile phase was 4:1 aqueous methanol solution, and the flow rate was set at 10. Mu.L/min. The operating temperature of the ion transfer tube was 150 ℃.
The mixed sample with the concentration of 1ng/mL is prepared by using trioctylamine, cocaine, tributylamine, methyl amphetamine, butylamine and diethylamine, the solvent is methanol, and a two-dimensional response spectrum formed by 10 mu L of the mixed sample solution in a combined device is shown in FIG. 3.
In the electrospray ionization source, a capillary spray needle is coaxially arranged in an airflow micro-pore channel with high-flow-rate gas introduced into the interior and is sealed and fixed, so that sheath flow gas auxiliary electrospray is constructed, and stable electrospray ion flow is generated; meanwhile, the high-flow-rate gas in the airflow micro-pore channel also cools the spray tip of the capillary spray needle, so that the phenomenon of stopping electrospray due to evaporation of spray solution in the capillary spray needle in high-temperature atmosphere is avoided; the charged atomized droplets generated by the capillary spray needle are further introduced into a high-intensity direct-current polarized electric field to carry out secondary polarized ionization, and the charged atomized droplets are broken into charged atomized tiny droplets with smaller size and more charged quantity, so that the charged atomized tiny droplets are easier to completely desolvate, and the ionization efficiency of a target sample is improved. The electrospray ionization source disclosed by the invention combines two technologies of sheath gas assisted electrospray and strong electric field polarization ionization, has the advantages of stable spray, high-temperature atmosphere resistance, high ionization efficiency and the like, and is suitable for the combination of liquid chromatography and ion mobility spectrometry.
Claims (6)
1. An electrospray ionization source, characterized by: comprises a capillary spray needle (1), an ion focusing electrode (2), a spray counter electrode (3) and a field polarization electrode (4);
The capillary spray needle (1) is a capillary tube with an axial through hole, the ion focusing electrode (2) is a cylindrical barrel with a closed left end and an open right end, the left side bottom surface inside the barrel is a hemispherical surface, the hemispherical bottom surface is coaxial with the barrel, the hemispherical bottom surface is provided with a through hole A along the axial direction, one end of the capillary spray needle (1) penetrates through the through hole to extend into the barrel, the other end of the capillary spray needle is positioned outside the barrel, the open end of the capillary spray needle (1) in the barrel is coaxial with the ion focusing electrode (2), the cylindrical side wall at the left end of the ion focusing electrode (2) is provided with an air inlet (6) for introducing sheath gas, the air inlet (6) is communicated with the axial through hole A of the ion focusing electrode (2), and the left hemispherical bottom surface inside the barrel is provided with a through hole serving as an air outlet (7);
a flat plate-shaped spray counter electrode (3) and a field polarization electrode (4) which are mutually spaced and placed in parallel and are provided with through holes in the middle are arranged in the cylindrical ion focusing electrode (2), the surfaces of the plate bodies of the spray counter electrode (3) and the field polarization electrode (4) are perpendicular to the axis of the cylinder, the spray counter electrode (3) is positioned between the capillary spray needle (1) and the field polarization electrode (4), sheet-shaped metal grid meshes capable of passing ions are arranged at the through holes in the middle of the spray counter electrode (3) and the field polarization electrode (4), and the through holes in the middle of the spray counter electrode (3) and the field polarization electrode (4) are coaxial with the capillary spray needle (1); the axis of the through hole is vertical to the surface of the flaky grid;
The peripheral edges of the plate bodies of the spray counter electrode (3) and the field polarization electrode (4) are respectively connected with the inner wall surface of the ion focusing electrode (2) in a sealing way through annular insulators; the field polarization electrode (4), the spray counter electrode (3), the ion focusing electrode (2) and the capillary spray needle (1) are applied with direct current voltages with the same polarity and sequentially increased voltage values, a direct current polarization electric field with the field intensity higher than 1000V/cm is formed between the field polarization electrode (4) and the spray counter electrode (3), and charged atomized liquid drops generated by the capillary spray needle (1) are cracked and secondarily ionized; the spray tip of the capillary spray needle (1) passes through the axial through hole of the cylindrical ion focusing electrode (2) and extends to the middle part in the cylinder after passing through the hemispherical bottom surface.
2. An electrospray ionization source as recited in claim 1, wherein: the left end of the cylindrical ion focusing electrode (2) is provided with a heat insulation block body (5), the heat insulation block body (5) is in airtight connection with the outer wall surface of the left end of the ion focusing electrode (2), meanwhile, the heat insulation block body (5) seals a through hole on the hemispherical bottom surface through which the capillary spray needle (1) passes, and the capillary spray needle (1) passes through the heat insulation block body (5) and then stretches into the cylinder body.
3. An electrospray ionization source as recited in claim 1, wherein: the number of the air outlets (7) is more than 2, and the air outlets are uniformly distributed along the same radial cross section of the hemispherical bottom surface.
4. Use of an electrospray ionization source according to any one of claims 1 to 3, characterized in that:
An electrospray ionization source according to any one of claims 1 to 3 as an ion source for ion mobility spectrometry, a field polarized electrode (4) as a first electrode in the ionization region of the ion mobility spectrometry along the direction from the ionization source to the ion receiving electrode; one end of a through hole of a capillary spray needle (1) positioned outside the ion focusing electrode (2) is connected with a mobile phase outlet of a liquid chromatography column, so that the liquid chromatography is combined with an ion mobility spectrometry.
5. The use according to claim 4, characterized in that:
when the liquid chromatography and ion mobility spectrometry combined device works, the flow rate of the liquid chromatography mobile phase is adjustable between 0.1 and 500 mu L/min.
6. The use according to claim 4, characterized in that:
One path of sheath gas in the ion mobility spectrometry enters an axial through hole at the left end of an ion focusing electrode (2) through an air inlet (6), a sheath layer with the section flow rate higher than 30m/s is formed between the outer wall surface of a capillary spray needle (1) and the inner wall surface of the axial through hole, the spray tip of the capillary spray needle (1) is cooled, the spray tip of the capillary spray needle (1) is assisted to form stable electrospray, high-temperature drift gas in the ion mobility spectrometry is used as a purge gas (8) to flow out of the ion mobility spectrometry from an air outlet (7) after passing through a field polarized electrode (4) and a grid mesh in the middle of a spray counter electrode (3).
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