An ion source device for tribo-ionization using DAPI

Abstract

The present invention discloses an ion source device that utilizes DAPI for friction ionization, and rapidly ionizes the gas passing through the silicone rubber tube or the substance on the silicone rubber surface through the static electricity generated by the opening and closing process of DAPI. The device mainly includes two pinch valves connected in series. The main principle is that the entry of the sample is controlled by the pinch valve close to the injection port; the other valve carries a charge on the inner wall through continuous opening and closing for friction, and ionizes the gas phase sample passing through. The device simplifies the additional ionization source required by other small instruments. Compared with other atmospheric pressure ionization sources, the structure is simpler and does not require redundant carrier gas or power supply. The structure meets the needs of rapid on-site detection, and at the same time provides a solution for some scenarios where exposed high-voltage devices cannot be used.

Description

Technical Field

[0001] The present invention relates to a mass spectrometry ionization source, specifically an ion source device that uses DAPI for friction ionization. It can be used to ionize a gaseous analyte in the absence of auxiliary gas or high voltage, and to achieve on-site rapid detection of gas. At the same time, a sample injection device and an ionization source are combined to simplify the overall structure of the instrument device. Background Art

[0002] The ion source is one of the most important components of a mass spectrometer. Common atmospheric pressure ionization sources for miniaturized instruments include LTP and APCI, which require additional gas assistance or high voltage for ionization during use. The friction ionization source combines the injection system and the ionization source, and can accumulate static charge on the inner surface of the tube wall through multiple squeezing and friction, which is used to ionize the gas phase compounds passing through. The friction ionization source is less reported. The existing friction ionization source is mainly that the liquid sample enters the injection tube, is ionized by friction with the tube wall surface during the evaporation process, and then enters the vacuum chamber for detection. This ionization method has a high sensitivity to proteins, and the amount of liquid required is at the μL level. It can be used in conjunction with liquid phase mass spectrometry to detect proteins in biological samples. McEwen et al. conducted an in-depth exploration of this technology. And the ionization efficiency was improved by increasing the temperature of the injection tube. However, the solution injection ionization method requires a continuous injection mode to reduce the residual time of the sample in the injection tube. Summary of the invention

[0003] The object of the present invention is to provide an ion source device for tribo-ionization using DAPI, and an ion source for tribo-ionization using DAPI is designed, which can be used to ionize gaseous test objects in the absence of auxiliary gas or high voltage, and realize on-site rapid detection of gas. At the same time, the sampling device and the ionization source are combined to simplify the overall structure of the instrument. By using two pinch valves in combination, the neutral gas sample injection is controlled by the opening and closing of the first pinch valve, and the charge accumulation on the inner wall of the silicone rubber tube is achieved by the continuous opening and closing of the second pinch valve, so that the neutral sample can be ionized after passing through the silicone rubber tube. The structure is simple, and the demand for on-site portable analytical instruments is met.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] An ion source device for tribo-ionization using DAPI comprises: a first pinch valve and a second pinch valve placed in parallel, two sections of a first silicone rubber tube and a second silicone rubber tube placed through the pinch valve core, an inter-valve capillary connecting the two sections of the silicone rubber tube, an injection capillary connected to the other end of the first pinch valve, and a vacuum capillary connected to the other end of the second pinch valve, wherein the pinch valves, silicone rubber tubes, and capillaries are coaxially placed;

[0006] The second pinch valve is controlled to continuously open and close so that the inner wall of the second silicone rubber tube repeatedly contacts the accumulated static charge, and the first pinch valve is opened and closed to inhale air, so that the sample entering the second silicone rubber tube is ionized to generate ions.

[0007] The injection capillary, inter-valve capillary and vacuum capillary are all metal capillaries.

[0008] The injection capillary is 4.00 cm long, 250 μm inner diameter, and 1 / 16 inch outer diameter, and is used for sampling from the normal pressure area; the intervalve capillary is 4.00 cm long, 250 μm inner diameter, and 1 / 16 inch outer diameter; the vacuum capillary is 4.00 cm long, 125 μm inner diameter, and 1 / 16 inch outer diameter.

[0009] It also includes a waveform generator electrically connected to the two pinch valves, and a host computer connected to the waveform generator; the waveform generator is used to output a waveform signal for controlling the opening or closing of the two pinch valves according to the instructions output by the host computer.

[0010] The host computer is a computer or an intelligent terminal device.

[0011] The host computer stores the following program modules, and when the host computer loads the following program modules, it controls the opening and closing of the two pinch valves to realize the generation of ion sources by friction ionization using DAPI;

[0012] The static charge accumulation program module is used to control the second pinch valve to continuously open and close according to the preset on-off time, so that the inner wall of the second silicone rubber tube where the valve core is placed is continuously in contact and separated, thereby generating static electricity on the inner wall of the tube;

[0013] The sample suction program module is used to control the opening of the first pinch valve according to the preset sampling time, so that the air pressure rises and the neutral gas sample passes through each metal capillary and the silicone tube in sequence; so that it is ionized into ions in the silicone tube of the second pinch valve core and enters the vacuum chamber of the ion trap mass spectrometer; it is also used to control the closing of the first pinch valve, and the air pressure drops accordingly, and controls the pressure to drop to a pressure suitable for the operation of the ion trap.

[0014] The sample inhalation sampling time is 12 ms.

[0015] The present invention has the following beneficial effects and advantages:

[0016] The invention can ionize the gas sample by the static electricity accumulated inside the pinch valve without the need for additional gas or high voltage assistance. The structure is simple and meets the needs of on-site portable analytical instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a cross-sectional diagram of the structure of a two-dimensional EI ionization source device;

[0018] Figure 2 A gas sample of 300 ppm toluene, 300 ppm m-dichlorobenzene, 300 ppm methyl tert-butyl ether and 200 ppm anisole mixture detected using a tribo-ionization ion source;

[0019] Among them, 1 is the first pinch valve, 2 is the second pinch valve, 3 is the first silicone rubber tube, 4 is the second silicone rubber tube, 5 is the injection capillary, 6 is the inter-valve capillary, 7 is the vacuum capillary, 8 is the waveform generator, 9 is the host computer, 10 is the electron multiplier, and 11 is the ion trap mass spectrometer. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the technical scheme of the present invention is further described below with reference to examples. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the invention, so the present invention is not limited by the specific implementation disclosed below.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0022] A common portable mass spectrometer includes an ionization source, a vacuum interface, a detector, an electronic control system, and a vacuum system. DAPI is a vacuum interface commonly used in small portable instruments. A small amount of neutral and ionized samples are sucked into the vacuum chamber by briefly opening. The use of DAPI reduces the burden on the vacuum pump and makes it possible for the development of small mass spectrometers. Common gas-phase atmospheric pressure ionization sources of small instruments, such as APCI and LTP, require additional carrier gas or high electric fields for ionization. In actual on-site detection, a large amount of gas and additional electricity are consumed. The present invention combines an ionization source with a vacuum interface, and utilizes the static electricity generated by the compression of the inner wall of the tube by the DAPI valve during the opening and closing process to ionize the gas-phase analyte.

[0023] The present invention relates to a mass spectrometry ionization source, which can be used to ionize a gaseous test object in the absence of auxiliary gas or high voltage, and realize on-site rapid detection of gas. At the same time, the sampling device and the ionization source are combined to simplify the overall structure of the instrument. The main principle of the device is to generate static electricity by squeezing and rubbing the inner wall of the silicone rubber tube through the pinch valve during the opening and closing process, and the neutral gaseous compound is ionized when entering the silicone rubber tube. Two connected pinch valves are respectively used to control the entry of neutral samples and to generate electric charges by continuously rubbing the inner wall of the tube to ionize the neutral sample. Compared with other common atmospheric pressure ionization methods, this ionization method has a simple structure, does not require additional auxiliary gas or high voltage, and meets the needs of miniaturized instruments on site.

[0024] Embodiment 1:

[0025] like Figure 1 As shown, DAPI (discontinuous atmospheric pressure interface) refers to a discontinuous atmospheric pressure injection interface. The friction ionization source of the present invention includes a metal capillary, a silicone rubber tube, and a pinch valve. The pinch valve is divided into a first pinch valve 1 and a second pinch valve 2. The silicone rubber tube is divided into a first silicone rubber tube 3 and a second silicone rubber tube 4. The metal capillary is divided into an injection capillary 5, an intervalve capillary 6, and a vacuum capillary 7.

[0026] The pinch valve core is equipped with a silicone rubber tube, and metal capillaries are inserted at both ends of the silicone rubber tube. Two pinch valves in series are connected by a metal capillary between the valves. The three sections of metal capillaries, namely the injection capillary 5, the capillary 6 connected between the pinch valves, and the vacuum injection capillary 7, are all coaxial and perpendicular to the plane where the front electrode of the ion trap mass spectrometer is located. When the pinch valve is in use, the first pinch 1 valve far away from the vacuum chamber is opened and closed to control the entry of the sample; while the second pinch valve 2 close to the vacuum chamber is continuously opened and closed, so that the inner wall of the second silicone rubber tube where the valve core is placed is continuously contacted and separated, generating static electricity on the inner wall of the tube for ionizing the sample.

[0027] The neutral gas sample enters from the injection capillary 5, passes through the intervalve capillary 6 between the series pinch valves when the first pinch valve far from the vacuum chamber is open, and finally passes through the second pinch valve 2 which is opened and closed continuously, and is ionized by the accumulated charge in its silicone rubber tube. Then, it enters the ion trap in the vacuum chamber from the vacuum capillary 7 to be detected.

[0028] The length and inner diameter of the capillary have an impact on the ionization efficiency, so the metal capillary (4.00 cm long, 250 μm inner diameter, 1 / 16 inch outer diameter) connected to one end of the pinch valve far from the mass spectrometer is used for sampling from the normal pressure region, and the other end is connected to another pinch valve through a metal capillary (4.00 cm long, 250 μm inner diameter, 1 / 16 inch outer diameter). The other end of the pinch valve at the rear end is connected to the vacuum chamber through a capillary (4.00 cm long, 125 μm inner diameter, 1 / 16 inch outer diameter).

[0029] Working principle: Neutral particles are sucked into the device through the pressure difference between the external atmospheric pressure and the low pressure in the vacuum chamber. When the neutral particles pass through the pinch valve close to the vacuum chamber, they are ionized by the static charge on the inner wall of the silicone rubber tube, and then enter the ion detector in the vacuum chamber for detection. First, the second pinch valve 2 is controlled to continuously open and close, so that the inner wall of the second silicone rubber tube where the valve core is placed is continuously in contact and separated, generating static electricity on the inner wall of the tube. Secondly, the first pinch valve 3 is controlled to open for about 12ms to pass the neutral sample through each metal capillary in turn, and is ionized into ions in the last metal capillary and enters the vacuum chamber of the ion trap mass spectrometer. The increase in air pressure helps the ion trap 11 to better capture ions. As the first pinch valve is closed, the air pressure drops accordingly. After it drops to a pressure suitable for the operation of the ion trap, the mass analysis process is carried out.

[0030] Embodiment 2:

[0031] Based on the above embodiment 1, it also includes a waveform generator 8 electrically connected to the two pinch valves, and a host computer 9 connected to the waveform generator; the waveform generator 8 is used to output a waveform signal for controlling the opening or closing of the two pinch valves according to the instruction output by the host computer 9; the host computer 9 is a computer or an intelligent terminal device; the host computer 9 stores the following program modules, and when the host computer loads the following program modules, the opening and closing of the two pinch valves are controlled to realize the use of DAPI for friction ionization to generate an ion source;

[0032] The static charge accumulation program module is used to control the second pinch valve 2 to continuously open and close according to the preset on-off time, so that the inner wall of the second silicone rubber tube 4 where the valve core is placed is continuously in contact and separated, generating static electricity on the inner wall of the tube;

[0033] The sample suction program module is used to control the opening of the first pinch valve 1 according to the preset sampling time, so that the air pressure rises and the neutral gas sample passes through each metal capillary and the silicone tube in turn; so that it is ionized into ions in the last metal capillary and enters the vacuum chamber of the ion trap mass spectrometer; it is also used to control the closing of the first pinch valve, and the air pressure drops accordingly, and is controlled to drop to a pressure suitable for the operation of the ion trap.

[0034] Figure 2 This is a gas sample of 300ppm toluene, 300ppm m-dichlorobenzene, 300ppm methyl tert-butyl ether and 200ppm anisole mixture detected using a friction ionization ion source. Among them, m-dichlorobenzene is a non-volatile, high ionization energy compound, and it is difficult to get a good ionization under other ionization sources. In this experiment, a Tedlar gas bag was used to dilute the gas bag with nitrogen, connected to the gas path of the metal capillary injection, and then entered the pinch valve to be ionized, and finally entered the mass spectrometer detector at the back end under the pressure difference.

[0035] The above-mentioned specific implementation methods are used to explain the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. An ion source device for tribo-ionization using DAPI, characterized in that: include: Two first pinch valves (1) and a second pinch valve (2) placed in parallel, two sections of a first silicone rubber tube (3) and a second silicone rubber tube (4) placed through the pinch valve core, and an inter-valve capillary (6) connecting the two sections of silicone rubber tube, an injection capillary (5) connected to the other end of the first pinch valve, and a vacuum capillary (7) connected to the other end of the second pinch valve, wherein the pinch valves, silicone rubber tubes, and capillaries are coaxially placed; By controlling the continuous opening and closing of the second pinch valve (2), the inner wall of the second silicone rubber tube (4) repeatedly contacts the accumulated static charge, and the first pinch valve (1) is opened and closed to inhale air, so that the sample entering the second silicone rubber tube (2) is ionized to generate ions.

2. The ion source device for tribo-ionization using DAPI according to claim 1, characterized in that: The injection capillary (5), the inter-valve capillary (6) and the vacuum capillary are all metal capillaries (7).

3. The ion source device for tribo-ionization using DAPI according to claim 1, characterized in that: The injection capillary (5) is 4.00 cm long, with an inner diameter of 250 μm and an outer diameter of 1 / 16 inch, and is used for sampling from the normal pressure area; the inter-valve capillary (6) is 4.00 cm long, with an inner diameter of 250 μm and an outer diameter of 1 / 16 inch; the vacuum capillary (7) is 4.00 cm long, with an inner diameter of 125 μm and an outer diameter of 1 / 16 inch.

4. An ion source device for tribo-ionization using DAPI according to any one of claims 1 to 3, characterized in that: It also includes a waveform generator (8) electrically connected to the two pinch valves, and a host computer (9) connected to the waveform generator; the waveform generator (8) is used to output a waveform signal for controlling the opening or closing of the two pinch valves according to the instruction output by the host computer (9).

5. The ion source device for tribo-ionization using DAPI according to claim 4, characterized in that: The host computer (9) is a computer or an intelligent terminal device.

6. The ion source device for tribo-ionization using DAPI according to claim 4, characterized in that: The host computer (9) stores the following program module, and when the host computer loads the following program module, it controls the opening and closing of the two pinch valves to realize the generation of an ion source by friction ionization using DAPI; The static charge accumulation program module is used to control the second pinch valve (2) to continuously open and close according to the preset on-off time, so that the inner wall of the second silicone rubber tube (4) where the valve core is placed is continuously in contact and separated, thereby generating static electricity on the inner wall of the tube; The sample inhalation program module is used to control the opening of the first pinch valve (1) according to a preset sampling time, so that the air pressure rises and the neutral gas sample passes through each metal capillary and the silicone tube in sequence; so that the sample is ionized into ions in the silicone tube of the second pinch valve core and enters the vacuum chamber of the ion trap mass spectrometer; and is also used to control the closing of the first pinch valve, so that the air pressure drops accordingly, and is controlled to drop to a pressure suitable for the operation of the ion trap.

7. The ion source device for tribo-ionization using DAPI according to claim 6, characterized in that: The sample inhalation sampling time is 12 ms.

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