A composite plasma normal pressure excitation source and its use

Abstract

The present invention provides a composite plasma atmospheric pressure excitation source and its use. The excitation source is composed of a four-tube coaxial inner needle, a quartz tube, a middle tube, an outer tube, a coaxial cable connector, a tuning piston, a side gas introduction end, a lower gas introduction end, a lower gas introduction end interface, an inner needle gas interface, a microwave introduction ring, and an APCI source. On the premise of having a similar tube torch to ICP, the excitation source of the present invention uses microwave energy with a frequency of 2.45 GHz as an energy source, adopts a four-tube coaxial structure, uses radio frequency plasma to ignite microwave plasma, and combines with a DC corona atmosphere to generate Ar plasma with high excitation ability, which can be used for mass spectrometry and spectral analysis, and can determine organic matter in a sample and almost all elements in the periodic table. Compared with MWP, the sample interacts with the plasma through the central channel in the plasma, which has the effect of not being easily quenched. The present invention has a reasonable design, good analytical performance, compact structure, and flexible tuning.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical measurement, and relates to a composite plasma normal-pressure excitation source, which is a device for exciting plasma at normal pressure by using microwave energy and radio frequency energy. Background Art

[0002] Direct ionization technology represented by atmospheric pressure desorption ionization source is a breakthrough development in the field of mass spectrometry in recent years, and its importance to work and scientific research is immeasurable. However, the existing atmospheric pressure desorption ionization source has defects such as insufficient ionization ability, narrow ionization range, and limited sample morphology, which are not enough to meet people's requirements. In addition, the sample needs to be pretreated before analysis, the sample analysis time is too long, and the introduced pretreatment reagents will interfere with and affect the subsequent analysis. Therefore, widening the detection range and direct sample analysis without pretreatment is an inevitable trend in the future development of atmospheric pressure desorption ionization source. Summary of the invention

[0003] In order to overcome the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a composite plasma atmospheric pressure excitation source, which is an atmospheric pressure Ar (or He, air) plasma excitation source using microwaves, direct current and radio frequency as energy sources.

[0004] The technical solution adopted by the present invention is: a composite plasma atmospheric pressure excitation source, which is composed of an atmospheric pressure corona source (APCI), a dielectric barrier discharge source (DBDI) and a microwave plasma, and has multiple working modes of soft ionization and hard ionization, which can realize efficient ionization of inorganic elements and organic matter in samples and conduct comprehensive analysis of samples. Turn on the APCI source and microwave plasma, and the sample is injected through the inner needle and passes through the plasma working area. The ion source works in the hard ionization mode, and the sample can be broken up to obtain rich sample element information. The sample is injected through the front end, and the organic matter in the sample is fragmented and ionized by the microwave plasma and APCI source to obtain the main signal peaks and fragment peaks of the organic matter in the sample. Turn on APCI and DBDI plasma, and the ion source works in the soft ionization mode, which can ionize the sample without loss. At the same time, APCI can further enhance the DBDI ionization effect and obtain complete organic information in the sample. Through the above steps, the organic matter information and inorganic element information in the sample are finally obtained, and the sample composition is analyzed more comprehensively.

[0005] The composite plasma atmospheric pressure excitation source provided by the present invention is a plasma atmospheric pressure excitation source using microwave, direct current and radio frequency as energy sources, and is composed of a four-tube coaxial inner needle, a quartz tube, a middle tube, an outer tube, a coaxial cable connector, a tuning piston, a side gas introduction end and a lower gas introduction end, a lower gas introduction end interface, an inner needle gas interface, a microwave introduction ring, and an APCI source. The inner needle, quartz tube, middle tube and outer tube are concentric tubes, and the four concentric tubes of the inner needle, quartz tube, middle tube and outer tube are all cylindrical through holes.

[0006] The lower end of the inner needle is fixed on the lower gas introduction end, the coaxial cable connector is fixed on the upper part of the outer tube by screws, the inner wire of the coaxial cable connector passes through the outer tube and is fixed on the microwave introduction ring, the inner hole of the tuning piston and the middle tube are hole-axis matched, the inner hole of the tuning piston and the middle tube are hole-axis matched, the microwave introduction ring is fixed on the outside of the middle tube by tight fitting, the quartz tube is located between the inner needle and the middle tube, and is fixed on the lower gas introduction end, and internal threads are machined at the upper and lower end faces of the outer tube, which are the lower internal threads of the outer tube and the upper internal threads of the outer tube respectively, the outer tube is connected to the middle tube through the lower internal threads of the outer tube, the height of the lower internal threads of the outer tube is about half of the length of the outer tube, and it is connected with the upper external threads of the middle tube by the lower internal threads of the outer tube. The tuning piston is located between the middle tube and the outer tube. The outer side of the tuning piston has an external thread that cooperates with the internal thread on the outer tube of the outer tube to be fixed in the outer tube. The APCI source is placed 5-20mm from the upper end face of the outer tube and can be arranged at an angle of 10-90° with the upper section of the outer tube. The side gas introduction end has the same interface structure as the lower gas introduction end, and is fixed to the lower opening of the middle tube through an external thread. The lower gas introduction end is fixed to the protrusion at the lower end of the middle tube through a thread. The lower gas introduction end interface and the inner needle gas interface are fixed to the lower gas introduction end through threads. The inner needle gas interface is tightly fitted with the inner needle through a hole-axis fit, and is used for the introduction of working gases into the quartz tube and the inner needle, respectively.

[0007] RF plasma is formed between the inner needle and the quartz tube, and microwave plasma is formed between the quartz tube and the middle tube. The height is about 20 mm. The height and intensity of the plasma flame can be adjusted by adjusting the gas flow rate and the microwave and RF power. RF plasma is used to ignite microwave plasma and ion source for soft ionization of substances, and microwave plasma is used for hard ionization of substances by ion source. After applying a certain high voltage, the APCI source ionizes the carrier gas and air to form corona plasma, further improving the ionization effect of the composite ion source. He (or Ar) is introduced from between the inner needle and the quartz tube and between the quartz tube and the middle tube, and is excited into He (or Ar) plasma by microwaves.

[0008] The inner needle is made of stainless steel, and can be passed with helium (or argon), a mixture of helium (or argon) and a gaseous sample, a mixture of helium (or argon) and volatile gas in the headspace of a liquid sample, and the like.

[0009] The quartz tube is made of insulating materials such as quartz glass or ceramics and is located between the inner needle and the middle tube. A metal film is plated on the top of the outer wall of the quartz tube, and the film height is 10 mm, which is used to apply high-frequency voltage to excite radio frequency plasma. Helium (or argon) is introduced between the middle tube and the quartz tube, and the outer side of the middle tube is connected with a microwave introduction ring to facilitate microwave feeding.

[0010] The middle tube is made of red copper and is fixed to the lower inner thread of the outer tube through an outer thread.

[0011] The outer tube is made of copper and is located outside the middle tube. The ratio of the inner diameter of the outer tube to the outer diameter of the middle tube is 2.3, so that its impedance is 50Ω. Oxygen or atmosphere can be introduced between the outer tube and the middle tube. The outer tube has an upper internal thread near the upper end surface, which is used to cooperate with the external thread at the tuning piston to adjust the distance between the end surface of the tuning piston and the open end surface. The upper end surface of the tuning piston is located between the middle tube and the outer tube. The distance between this end surface and the top of the outer tube is an odd multiple of 1 / 4 of the working microwave wavelength, and the distance is adjustable.

[0012] The coaxial cable connector has an impedance of 50Ω and passes through the outer tube to be connected with the microwave introduction ring for transmitting microwaves.

[0013] The tuning piston is made of red copper and is located between the middle tube and the outer tube. It has an external thread on the outside, which works together with the upper internal thread of the outer tube and can move up and down by relying on the thread. By adjusting the distance between it and the open end face, the electric field on the open end face is the strongest during operation.

[0014] The side gas introduction end is fixed in the lower end opening of the middle tube by means of external threads and is used for introducing gas into the middle tube.

[0015] The lower gas introduction end is made of insulating materials such as PPEK, and is fixed to the lower end of the middle tube through the upper internal thread, and is mainly used for fixing the quartz tube and the inner tube.

[0016] The side gas introduction end is located on the lower gas introduction end, is fixed on the lower gas introduction end through an external thread, and is used for introducing working gas into the quartz tube.

[0017] The gas introduction port is fixed on the inner needle and is used for introducing working gas and samples into the inner needle.

[0018] The microwave introduction ring is made of red copper, is coaxially matched and fixed with the middle tube, and plays the role of positioning the coaxial inner conductor in the coaxial cable, and is used to introduce microwave energy into the ion source.

[0019] The APCI source material is stainless steel, and the outer diameter of the tip is in the micrometer range to increase the discharge effect. It is placed at the front end of the outer tube and forms a corona plasma by applying a certain high voltage direct current to enhance the ionization effect of the ion source.

[0020] Another object of the present invention is to utilize the composite plasma atmospheric pressure excitation source in mass spectrometry, spectral analysis, and the determination of organic matter in samples and almost all elements in the periodic table. Under the premise of having a similar tube torch to ICP, the excitation source of the present invention uses microwave energy with a frequency of 2.45GHz as an energy source, adopts a four-tube coaxial structure, uses radio frequency plasma to ignite microwave plasma, and combines with a DC corona atmosphere to produce Ar plasma with high excitation ability, which can be used for mass spectrometry, spectral analysis, and can determine organic matter in samples and almost all elements in the periodic table. At the same time, compared with MWP, the sample interacts with the plasma through the central channel in the plasma, which has the effect of not being easily quenched. The plasma excitation source has the characteristics of good analytical performance, compact structure, flexible tuning, etc.

[0021] Compared with the prior art, the beneficial effects of the present invention are: it has a four-tube coaxial structure, has the ability to ignite radio frequency plasma, microwave plasma and corona plasma at the same time, and forms a plasma with a central channel, which can work stably in a microwave state and can also be excited and used in a radio frequency state. It has multiple working modes such as soft ionization and hard ionization, and can achieve efficient ionization of inorganic elements and organic matter in the sample in one ion source to obtain richer sample information. Organic matter can be partially fragmented and losslessly ionized, and complete information of organic matter can be obtained through lossless ionization, thereby realizing rapid qualitative analysis of organic matter. Combined with the fragmented molecules of partially fragmented organic matter, the structural information of organic matter can be derived, and the accuracy of qualitative analysis of organic matter in the sample can be enhanced. It can contact with the sample well without being quenched easily, making it have strong sample tolerance; based on microwave energy and radio frequency energy, a stable He plasma is obtained at normal pressure, which has a strong excitation ability, so that it can determine almost all elements in the periodic table, including halogens, with a wide measurement range; introducing oxygen between the outer tube and the middle tube can reduce background emission and interference; it can directly analyze the sample without pretreatment, and the operation is simple. Diversified ionization modes: by switching between microwave plasma and radio frequency plasma, soft ionization and hard ionization of the sample can be achieved, taking into account the capabilities of soft and hard ionization. When used as an ion source for a mass spectrometer, it can form a multi-mode component analysis including direct real-time analysis, electrospray macromolecular analysis, and simultaneous detection of organic matter and elements. It can be conveniently used as an excitation source for instruments such as mass spectrometers and spectrometers. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The sectional view of the overall structure of the present invention: the left picture is the main view, and the right picture is the side view. Inner needle 1, quartz tube 2, middle tube 3, outer tube 4, coaxial cable connector 5, tuning piston 6, side gas introduction end 7 and lower gas introduction end 8 and lower gas introduction end interface 9, inner needle gas interface 10, microwave introduction ring 11, APCI source 12.

[0023] Figure 2 Schematic diagram of the structure of the inner needle 1, the upper figure is the main view, the lower figure is the top view, and 13 is the outer thread end face of the inner needle. Figure 3 Schematic diagram of the structure of the quartz tube 2, the upper figure is the main view, the lower figure is the top view, 14 is the metal film, 15 is the external thread end face of the quartz tube.

[0024] Figure 4 Schematic diagram of the structure of the middle tube 3, the left figure is the main view, the right figure is a sectional view, 16 is the external thread on the middle tube, 17 is the internal thread hole in the middle tube, 18 is the external thread on the middle tube, and 19 is the air hole in the middle tube.

[0025] Figure 5 Schematic diagram of the structure of the outer tube 4, the left figure is the main view, the right figure is a cross-sectional view, 20 is a through hole, 21 is the lower inner thread of the outer tube, 22 is the SMA fixing hole, and 23 is the upper inner thread of the outer tube.

[0026] Figure 6 Schematic diagram of the structure of microwave introduction ring 11: the upper figure is a sectional view, the lower figure is a main view, and 24 is an inner needle fixing hole.

[0027] Figure 7 Schematic diagram of the structure of the coaxial cable connector 5: the upper figure is the main view, the lower figure is the top view, 25 is the coaxial cable SMA connector fixing hole, 26 is the coaxial inner conductor.

[0028] Figure 8 27 is a cross-sectional view of the tuning piston 6; 27 is a tuning piston adjustment thread.

[0029] Fig. 9 It is a schematic diagram of the gas introduction end 8: the left picture is the main view, the right picture is the cross-sectional view, 28 is the first internal threaded hole, 29 is the second internal threaded hole, 30 is the air vent, 31 is the third internal threaded hole, and 32 is the fourth internal threaded hole.

[0030] Fig.10 7 is a cross-sectional view of the side gas introduction end: 33 is the external thread of the gas introduction end.

[0031] Fig.11 34 is the external thread of the gas introduction end interface.

[0032] Fig.12 It is a cross-sectional view of the inner needle gas interface 10: 35 is the gas path vent.

[0033] Fig.13 FIG. 1 is a cross-sectional view of an APCI source 12 . DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0035] Example 1

[0036] See also Figure 1-13 , a normal pressure microwave plasma excitation source, comprising an inner needle 1, a quartz tube 2, a middle tube 3, an outer tube 4, a coaxial cable connector 5, a tuning piston 6, a side gas introduction end 7 and a lower gas introduction end 8 and a lower gas introduction end interface 9, an inner needle gas interface 10, a microwave introduction ring 11, and an APCI source 12. The inner needle 1, the quartz tube 2, the middle tube 3, and the outer tube 4 are concentric pipes, all of which are cylindrical through holes.

[0037] The inner needle 1 is connected to the fourth internal thread hole 32 of the gas introduction end 8 through the inner needle external thread end face 13 and is fixed on the gas introduction end 8. The inner needle gas interface 10 is tightly fixed to the outer diameter of the inner needle 1 through the gas path vent hole 35, and is used for the gas to flow into the inner needle 1. Helium (or argon), a mixture of helium (or argon) and a gaseous sample, a mixture of helium (or argon) and a liquid sample headspace volatile gas, etc. are introduced into the inner needle gas interface 10 to generate and maintain plasma and ionize the sample in the gas at the same time. The quartz tube 2 is connected to the third internal thread hole 31 of the gas introduction end 8 through the quartz tube external thread end face 15 and is fixed on the gas introduction end 8. The lower end gas introduction end interface 9 is connected to the first internal thread hole 28 of the gas introduction port 8 through the gas introduction end interface external thread 34, and is fixed on the gas introduction port 8, which is used for the lower end gas introduction, and the gas flows through the vent hole 30 and enters the quartz tube 2. The middle tube 3 is connected to the inner thread 21 of the outer tube through the outer thread 16 on the middle tube and fixed on the outer tube 4. The side gas introduction end 7 is connected to the inner thread hole 17 of the middle tube through the outer thread 33 of the gas introduction end interface and fixed on the middle tube 3 for the side gas to flow in, and the gas enters the air hole 19 of the middle tube. The middle tube 3 is connected to the second inner thread hole 29 of the gas introduction end 8 through the outer thread 18 at the bottom of the middle tube, and is fixed on the lower gas introduction end 8, and helium (or argon) is introduced through the gas introduction port 8. The tuning piston 6 is connected to the inner thread 23 on the outer tube through the tuning piston adjustment thread 27 and fixed in the outer tube 4. The purpose of adjusting the electric field is achieved by adjusting the distance between the tuning piston 6 and the open end surface. The impedance of the coaxial cable SMA connector 5 is 50Ω. In this embodiment, the microwave energy frequency can be 2.45GHz, 5.8Ghz and other frequencies, and the power is adjustable from 0 to 50W. The structure of this embodiment can also withstand high-power microwave energy, and the microwave enters the plasma excitation source through the coaxial cable SMA connector 5. The coaxial cable SMA connector 5 is loosely fixed through the through hole 20 on the outer tube 4. The coaxial cable SMA connector 5 is fixed to the SMA fixing hole 22 of the outer tube 4 through the coaxial cable SMA connector fixing hole 25 with an M2.5 screw.

[0038] The coaxial inner conductor 26 of the coaxial cable SMA connector 5 enters between the outer tube 4 and the middle tube 3 through the small hole on the outer tube 4 and is welded to the middle tube 3. The coaxial inner conductor 26 of the coaxial cable SMA connector 5 is positioned via the inner needle fixing hole 24 at the microwave introduction ring 11. The inner side of the microwave introduction ring 11 is tightly connected to the outer side of the middle tube 3. Microwaves are transmitted between the outer tube 4 and the middle tube 3. The ratio of the inner diameter of the outer tube 4 to the outer diameter of the middle tube 3 is about 2.3, and the impedance is 50Ω to reduce the microwave reflection power. The microwave is reflected at the end face of the tuning piston 6, and a standing wave is formed between the middle tube 3 and the outer tube 4. The electric field is strongest at odd multiples of 1 / 4 wavelength, and the magnetic field is strongest at even multiples of 1 / 2 wavelength. The tuning piston 6 is adjusted to make the electric field at the device port the strongest, and at the same time reduce the reflected power to zero.

[0039] By adjusting the gas flow in the inner needle 1 and the middle tube 3, and providing a certain amount of primary electrons at the device port, microwave plasma can be easily excited. Microwave plasma is formed between the inner needle 1 and the middle tube 3, with a height of about 20 mm. By adjusting the gas flow and microwave power, the height and intensity of the plasma flame can be adjusted. The metal film 14 at the quartz tube 2 is used to apply a high-frequency voltage to excite the radio frequency plasma. The APCI source 12 is placed at the front end of the outer tube 4 and applies a DC high voltage to ionize the air to form a corona plasma. By adjusting the working order of microwave plasma, radio frequency plasma and corona plasma, efficient ionization of different substances in the sample can be achieved.

[0040] Example 2 Working process 1 of the present invention

[0041] Ionization of elements in the sample (inner tube sampling): Turn on the gas flowmeter, control the gas flow in the middle tube 3 and the quartz tube 2, and select the appropriate helium (or argon) flow. Turn on the microwave source to generate 2.45GHz or 5.8Ghz microwave energy, and connect the microwave source output port to the coaxial cable SMA connector 5 through a 50Ω coaxial line. The microwave energy enters between the outer tube 4 and the middle tube 3 through the coaxial cable SMA connector 5, and is reflected at the end face of the tuning piston 6 to form a standing wave. Adjust the position of the tuning piston 6 to make the device port distance appropriate, and the end face of the tuning piston 6 is about 1 / 4 wavelength. Fine-tune the tuning piston 6 to make the electric field at the device port the strongest, and reduce the reflected power to zero. By applying a certain frequency of radio frequency electricity to the metal film 14 on the quartz tube 2, radio frequency plasma is generated, thereby initiating a microwave plasma flame, and then the radio frequency electricity is turned off, leaving only the microwave plasma working. Adjust the gas flow in the middle tube 3 and the inner needle 1 and the microwave source power to improve the plasma flame shape and performance characteristics. The APCI source 12 is turned on to supply high voltage electricity, and corona plasma is formed by ionizing the air, which cooperates with the microwave plasma to improve the ionization efficiency of the ion source. The sample is mixed with the working gas in the inner tube 1, enters the plasma with the airflow, and passes through the microwave plasma flame under the airflow. Under the action of high-energy electrons and high-energy metastable atoms in the microwave plasma, the elements in the sample are ionized to obtain the element composition information in the sample.

[0042] Example 3 Working process 2 of the present invention

[0043] Ionization of organic matter in the sample (front-end sampling): Turn on the gas flowmeter, control the gas flow in the middle tube 3 and the quartz tube 2, and select the appropriate helium (or argon) flow. Turn on the microwave source to generate 2.45GHz or 5.8Ghz microwave energy, and connect the microwave source output port to the coaxial cable SMA connector 5 through a 50Ω coaxial line. The microwave energy enters between the outer tube 4 and the middle tube 3 through the coaxial cable SMA connector 5, and is reflected at the end face of the tuning piston 6 to form a standing wave. Adjust the position of the tuning piston 6 to make the device port distance appropriate, and the end face of the tuning piston 6 is about 1 / 4 wavelength. Fine-tune the tuning piston 6 to make the electric field at the device port the strongest, and reduce the reflected power to zero. By applying a certain frequency of radio frequency electricity to the metal film 14 on the quartz tube 2, radio frequency plasma is generated, thereby initiating a microwave plasma flame, and then the radio frequency electricity is turned off, leaving only the microwave plasma working. Adjust the gas flow in the middle tube 3 and the inner needle 1 and the microwave source power to improve the plasma flame shape and performance characteristics. The APCI source 12 is turned on to supply high voltage electricity, and corona plasma is formed by ionizing the air, which cooperates with the microwave plasma to improve the ionization efficiency of the ion source. The sample is placed between the end face of the outer tube 4 and the APCI source, and a certain distance is maintained from the microwave plasma. While ensuring that the plasma acts on the sample, the contact between the plasma and the sample is reduced to prevent the complete fragmentation of the organic matter in the sample. Under the action of high-energy electrons and high-energy metastable atoms in the microwave plasma and the APCI source 12 power supply, the organic matter will be partially fragmented, while retaining a certain amount of complete information of the organic matter, and finally the complete information of the organic matter and partial fragment information are obtained.

[0044] Example 4 Working process 3 of the present invention

[0045] Ionization of organic matter in the sample (front-end injection): Turn on the gas flowmeter, control the gas flow in the middle tube 3 and the quartz tube 2, and select the appropriate helium (or argon) flow. Apply radio frequency electricity of a certain frequency to the metal film 14 on the quartz tube 2 to generate radio frequency plasma, and adjust the gas flow in the middle tube 3 and the inner needle 1 to improve the flame shape and performance characteristics of the radio frequency plasma. Turn on the APCI source 12 to supply high voltage electricity to form a corona plasma by ionizing the air. The sample is placed between the end face of the outer tube 4 and the APCI source, keeping a certain distance from the radio frequency plasma. While ensuring that the plasma acts on the sample, the introduction of the plasma and the sample is reduced to prevent the organic matter in the sample from breaking into fragments. Under the action of high-energy electrons and high-energy metastable atoms in the radio frequency plasma and the APCI source 12 power supply, fragment-free ionization of organic matter is achieved.

[0046] The above-mentioned embodiments should not be understood as limiting the scope of protection of the present invention. The key to the present invention is that a group of plasma generators integrates a variety of plasma excitation methods such as microwave excitation, radio frequency excitation, dielectric barrier discharge excitation, and corona discharge excitation. This composite plasma excitation device can be used to adjust the physical properties of charged particles in the plasma generated by the working gas, so as to adjust and change the ionization method, mechanism and state of the sample after ionization (maintaining molecular ions, or generating fragment ions, and the degree of fragmentation, etc.) when ionizing the sample, thereby adjusting the selectivity in the sample ionization process and improving the ionization effect. Without departing from the spirit of the present invention, any form of change made to the present invention should fall within the scope of protection of the present invention.

Claims

1. A composite plasma atmospheric pressure excitation source, It is characterized in that The invention comprises an inner needle (1), a quartz tube (2), a middle tube (3), an outer tube (4), a coaxial cable connector (5), a tuning piston (6), a side gas introduction end (7), a lower gas introduction end (8), a lower gas introduction end interface (9), an inner needle gas interface (10), a microwave introduction ring (11), and an APCI source (12). The inner needle (1), the quartz tube (2), the middle tube (3), and the outer tube (4) are concentric cylindrical tubes. The lower end of the inner needle (1) is fixed to the lower gas introduction end (8). The coaxial cable connector (5) is fixed to the upper part of the outer tube (4) by screws. The inner wire of the coaxial cable connector (5) passes through the outer tube (4) and is fixed to the microwave introduction ring (11). The inner hole of the tuning piston (6) and the middle tube (3) are hole-axis matched. The microwave introduction ring (11) is fixed to the outer side of the middle tube (3) by tight fit. The quartz tube (2) is located between the inner needle (1) and the middle tube (3) and is fixed at the lower On the side gas introduction end (8), internal threads are formed at the upper and lower end faces of the outer tube (4), namely, the lower internal thread (21) of the outer tube and the upper internal thread (23) of the outer tube, and the tuning piston (6) is connected to the middle tube (3) by means of the internal threads. The tuning piston (6) is located between the middle tube (3) and the outer tube (4). The outer side of the tuning piston (6) has external threads that cooperate with the upper internal thread (23) of the outer tube of the outer tube to be fixed in the outer tube (4). The APCI source (12) is placed on the upper end face of the outer tube (4). The side gas introduction end (7) has the same structure as the lower gas introduction end interface (9), and is fixed to the lower end opening of the middle tube (3) by external threads. The lower gas introduction end (8) is fixed to the lower end of the middle tube (3) by threads. The lower gas introduction end interface (9) and the inner needle gas interface (10) are fixed to the lower gas introduction end (8) by threads, and are used for introducing working gas into the quartz tube (2) and the inner needle (1), respectively.

2. A composite plasma atmospheric pressure excitation source according to claim 1, It is characterized in that The lower end of the outer tube (4) is provided with an outer tube lower internal thread (21), the height of which is approximately half the length of the outer tube (4), and the outer tube lower internal thread (21) is connected to the outer thread (26) on the middle tube (3) by means of the outer tube lower internal thread (21).

3. A composite plasma atmospheric pressure excitation source according to claim 1, It is characterized in that The APCI source (12) is placed 5-20 mm from the upper end surface of the outer tube (4) and forms an angle of 10-90° with the upper section of the outer tube (4) for implementing corona discharge ionization, and further for adjusting and enhancing the ionization effect of microwave plasma, radio frequency plasma, and corona discharge plasma on the sample.

4. A composite plasma atmospheric pressure excitation source according to claim 1, It is characterized in that The sample is injected through the inner needle (1) and passes through the microwave plasma, and the elements in the sample are ionized by the microwave plasma between the middle tube (3) and the outer tube (4).

5. The composite plasma atmospheric pressure excitation source according to claim 1 is used in mass spectrometry, spectrum analysis, and determination of organic matter and elements in the periodic table in samples.

6. The use according to claim 5, It is characterized in that A certain radio frequency electricity is applied to the metal film (14) on the quartz tube (2) to excite the working gas to generate radio frequency plasma, thereby exciting the microwave plasma between the middle tube (3) and the outer tube (4).

7. The use according to claim 5, It is characterized in that The sample is placed between the APCI source (12) and the outer tube (4) for injection, and the sample does not come into contact with the microwave plasma. The organic matter in the sample is ionized by the microwave plasma between the middle tube (3) and the outer tube (4).

8. The use according to claim 5, It is characterized in that The sample is placed at the rear end of the APCI source (12) for injection. The sample does not contact the plasma torch, and only utilizes the surrounding discrete ions and / or ions enhanced by corona discharge to perform secondary ionization on the components to be measured in the sample.

9. The use according to claim 5, It is characterized in that Corona plasma is generated by an APCI source (12), radio frequency plasma is generated by applying a certain radio frequency electricity to a metal film (14) on a quartz tube (2), microwave plasma is generated by a middle tube (3) and an outer tube (4), and the combination of corona plasma, microwave plasma and radio frequency plasma is adjusted to perform ionization analysis on elements and organic matter in the same sample.

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