Ionization device

Abstract

The invention discloses an ionization device. Electrospray is an ionization mode, and after the electrospray is combined with a mass spectrometer or an ion mobility instrument, atoms and molecules can be analyzed or some microorganisms or cells can be directly analyzed. Based on the process that liquid fluid is atomized and expanded firstly and then gaseous fluid is compressed before entering an instrument in the electrospray process, a geometric structure cavity matched with the liquid fluid in shape is designed and used for spraying. By means of the mode that the shape is matched with the introduction process of the fluid, spray moves forwards as much as possible in a laminar flow mode, so that more stable spray fluid is obtained, and ions can be better introduced into an instrument for analysis.

Description

Technical Field

[0001] The present technology is applicable to the ionization of atoms, molecules, or aggregates composed of molecules, and the technical field and scenarios of devices that require constraining ions to enter an instrument, and particularly relates to an ionization device. Background Art

[0002] By means of electrospray, target molecules can be made into charged gaseous ions, which can be used for the analysis of target substances after being used in combination with a mass spectrometer or an ion mobility spectrometer.

[0003] In the process of electrospray ionization, a liquid sample passes through a spray needle, forms a spray under the action of an electric field, and further generates gas-phase charged ions during the processes of evaporation and Coulomb explosion. The charged ions then enter the instrument for analysis. In this process, the ionization ratio of sample molecules, the stability of the spray / ion fluid (i.e., as laminar flow rather than turbulent flow as much as possible), and the entry of charged ions as completely as possible and neutral molecules as little as possible into the vacuum interface determine the sensitivity, signal stability, and signal-to-noise ratio of the mass spectrometer. Generally, it is considered that only a very low proportion of ions reach the detector from the start of generation, and most ions are lost during the transmission process, and the main loss occurs during the entry into the instrument.

[0004] So far, there have been many ways to solve this problem. One is similar to Patent US4531056, which realizes ionization and ion introduction through a series of disc-shaped or conical ion lenses. Two is similar to Patent US5432343, which realizes ionization and ion introduction through an ion transfer tube plus an ion lens. The above two methods are the mainstream technical solutions of current commercial instruments. At the same time, with the development of the ion funnel technology, various companies have further introduced ion funnels for ion focusing on the basis of the above two methods. Three is similar to Patent US6992299, which uses an air flow-constrained ionization method, mainly controlling the front end of ionization and not considering the aerodynamics at the vacuum inlet end; another example is Patent CN102142352, which mentions a method of controlling the spray by placing the spray position at a certain air flow zero point to achieve stable spraying, but does not fully consider the geometric shape constraints and guidance of the spray fluid dynamics. The above methods one and two mainly focus on the transmission optimization based on the electric field and lack consideration in terms of spray fluid dynamics; methods three and four do not fully consider the dynamic constraints of the spray fluid during the entire movement process, and at the same time, the consideration of the electric field constraints on ion movement is also insufficient.

[0005] The gas flow of electrospray forms a high-speed and stable free jet at the outlet end of the spray needle and gradually presents a horn-like amplified trajectory; at the vacuum interface end of the mass spectrometer interface, the jet enters the mass spectrometer in an inverted horn shape. So far, no technology has fully considered the aerodynamic characteristics of gas flow expansion and contraction and optimized ion transport based on the bilateral fluid form. In the 19th century, the Laval (Patent US 522,066) introduced the Laval nozzle design, which generates a high-speed jet through a converging-diverging shape, and this design is widely used in other nozzle designs such as rocket engines and jet engines. Electrospray ionization also follows similar physical laws, and an unoptimized nozzle structure will generate turbulent flow, resulting in fluctuations in signals and loss of ions. Through a similar principle, this patent presents a nearly symmetric Laval nozzle-like interface design at the nozzle orifice and the mass spectrometry inlet respectively, improving the ion transport efficiency, forming a stable fluid and simplifying the structure. At the same time, based on the fact that the loss of ions at the ion source is mainly due to the expansion of the ion gas cluster, additional gas flow and ion electric field focusing devices can be further added to assist in the constraint of the ion beam shape. Summary of the Invention

[0006] The present invention forms a structure similar to a Laval nozzle at the spray needle of the ion source by providing a geometric combination structure with a special design, and through the combination of a spray chamber matching the spray fluid form, supplemented by gas pressure and gas flow control, so that the spray fluid maintains a laminar flow state as much as possible throughout the process and enters the mass spectrometer as completely as possible.

[0007] The specific technical solution is as follows: Spraying is completed within an internal space approximating a spindle shape, followed by ionization and introduction into the mass spectrometer. The shape of the inner surface of the spindle is composed of two geometric bodies with nearly symmetric inner surfaces (the inner surface shapes of the two geometric bodies are approximately half of a spindle cut from the diameter maximum, but of different sizes; for ease of description, the half spindle closer to the needle is called the left half spindle, and the half spindle closer to the mass spectrometer is called the right half spindle). Further description is as follows: The liquid sample to be analyzed is introduced through the needle. The liquid at the needle outlet forms a high-speed free jet under the action of an electric field. This jet enters through the center of the tip of the left half spindle. During the forward movement of the jet, it continues to expand and finally becomes ionized gas. At the same time, around the needle, a gas is connected to provide gas pressure. This gas pressure forms an isolation air curtain between the jet and the inner surface of the left half spindle. The jet is further atomized during the forward movement and enters the right half spindle. The ionized gas is introduced into the mass spectrometry inlet through the tip of the right half spindle. Due to the proximity to the mass spectrometry inlet, the vacuum system inside the mass spectrometer forms a local negative pressure near the other end of the right half spindle. The ionized gas is compressed into the ion source under the action of inertia and pressure gradient. At the junction of the left half spindle and the right half spindle, gas can be connected to provide gas pressure. This gas forms an isolation air curtain along the inner surface of the right half spindle, restricting the ionized gas from entering the mass spectrometry inlet.

[0008] The stability of the mass spectrometry ion signal can be observed to adjust the position of the needle before and after the tip of the left half spindle and the overlapping degree at the contact of the two half spindles to obtain a more stable spray.

[0009] Generally, the needle orifice can be a flat orifice or a needle tip orifice with a gradually decreasing diameter.

[0010] The docking diameters of the two half spindle-shaped geometric bodies are one large and one small, and one spindle can be partially inserted into the other.

[0011] The specific spraying and technical implementation process of this solution is as follows:

[0012] 1. This process is mainly described in four sections: high-speed jet section, spray expansion section, gas / ion compression section, and gas / ion entry section.

[0013] 2. High-speed jet section: Under the action of an externally applied electric field, a stable jet is formed at the needle orifice of the liquid flow. The diameter of this jet is generally equivalent to the diameter of the needle orifice. Due to the relatively high initial velocity, it still exists in the form of a jet for a period of time. This jet enters through the tip of the left half spindle. Around the needle, a gas atmosphere is provided with a pressure of P1. By adjusting the gas source pressure, the spray and the jet can be made more stable; at the same time, an atmosphere gas G1 is formed, and G1 can restrict and isolate the jet from the geometric body.

[0014] 3. Spray expansion section: With the high-speed movement of the jet, the liquid flow and droplets break up under the action of the electric field and gas, and the jet finally forms a spray shape. During this process, the diameter of the fluid rapidly enlarges. In this process, problems similar to under-expansion and over-expansion at the end of the nozzle of a rocket engine will occur. If the nozzle diameter is too large, the high-speed fluid will be over-expanded; if the nozzle diameter is too small, the high-speed fluid will be under-expanded. Both states will form turbulence, resulting in the instability of the ion flow. By controlling the position of the spray needle and adjusting the degree of overlap between the left and right half-spindles, the shape inside the spindle can be changed, allowing the jet to enter the fluid compression section in a properly expanded state, that is, the diameter of the expanded spray is equivalent to the inner surface diameter of the air curtain G1 expanded under the action of the spray.

[0015] 4. Gas / ion compression section: In the spray expansion section, the spray further turns into gas and charged ions under the action of evaporation and Coulomb force. The original expansion section geometry is connected to a tapered geometry, and a gas atmosphere with a pressure of P2 is provided at the two connection ports to form the ambient gas G2. The pressure of this gas is slightly higher than the pressure after the expansion of G1. Under the dual action of the gas pressure P2, the geometry, and the gas pressure gradient, the gas / ion flow formed by the original spray is gradually compressed during the forward movement.

[0016] 5. Gas / ion inlet section: After the gas / ion flow is compressed and converged, it continues to move forward. It can enter the mass spectrometer in two ways. One way is to directly enter the mass spectrometer, which is suitable for the case where the liquid flow rate is not large. Another way is to introduce it into the mass spectrometer through a concentric but smaller-diameter ion transfer tube or ion lens to avoid excessive neutral molecules from entering the mass spectrometer. Description of the Drawings

[0017] Figure 1 It is a schematic cross-sectional view of the first ionization device provided by the present invention.

[0018] Figure 2 It is a schematic cross-sectional view of the second ionization device provided by the present invention. Detailed Embodiments

[0019] The following further describes the present invention in combination with the drawings:

[0020] Figure 1As shown, it is a typical embodiment of the present invention patent. It includes a spray needle 1, a spray chamber 3 (left semi-spindle geometry), an ionization chamber 4 (right semi-spindle geometry), and a mass spectrometer 5. When the sample is introduced from the spray needle 1, the liquid sample forms a high-speed jet at the spray needle port 2 under the action of the spray voltage 7. The spray voltage 7 of the mass spectrometer is applied between the spray needle 1 and the mass spectrometer inlet 6, and the spray needle is grounded to ensure the safety of the operator. The high-speed jet enters a spray chamber 3 with a gradually expanding diameter, forms a spray and is ionized; then it enters a gradually shrinking ionization chamber 4 and enters the mass spectrometer through the mass spectrometer inlet 6. The ionization chamber 4 can be in contact or not in contact with the mass spectrometer 5. At the spray needle port 2, an ambient gas G1 can be added, and the spray jet can be constrained by adjusting its pressure P1. Between the spray chamber 3 and the ionization chamber 4, an ambient gas G2 can also be added, and the pressure P2 can be adjusted to constrain the ionized sample fluid. Between the ionization chamber 4 and the mass spectrometer inlet 6, an ambient gas G3 can also be added, and the pressure P3 can be adjusted to constrain the ionized sample fluid entering the mass spectrometer.

[0021] Figure 2 Another typical embodiment of the present invention patent. It also includes a spray needle 1, a spray chamber 3 (left semi-spindle geometry), an ionization chamber 4 (discontinuous right semi-spindle geometry formed by an ion funnel), and a mass spectrometer 5. When the sample is introduced from the spray needle 1, the liquid sample forms a high-speed jet at the spray needle port 2 under the action of the spray voltage 7. The spray voltage 7 of the mass spectrometer is applied between the spray needle 1 and the mass spectrometer inlet 6. The high-speed jet enters a spray chamber 3 with a gradually expanding diameter, forms a spray and is ionized; the ionized gas further enters the ionization chamber 4 and enters the mass spectrometer through the mass spectrometer inlet 6. The ionization chamber 4 can be in contact or not in contact with the mass spectrometer 5. At the spray needle port 2, an ambient gas G1 can be added, and the spray jet can be constrained by adjusting its pressure P1. Between the spray chamber 3 and the ionization chamber 4, an ambient gas G2 can also be added, and the pressure P2 can be adjusted to constrain the ionized sample fluid. Between the ionization chamber 4 and the mass spectrometer inlet 6, an ambient gas G3 can also be added, and the pressure P3 can be adjusted to constrain the ionized sample fluid. By adding an ion funnel (a disc with an ion leak, forming a discontinuous right semi-spindle structure) inside the ionization chamber 4, the ions are focused and then can enter the mass spectrometer better.

[0022] The present invention is not limited to the above embodiments. All embodiments obtained without any creative work are within the protection scope of the present invention.

Claims

1. An ionization device, comprising a fluid electrospray needle, a geometric body 3 with a semi-spindle inner surface that gradually expands as the spray expands, which confines the spray to form a stable air flow (while isolating the influence of the external environment); a geometric body 4 with a semi-spindle inner surface whose diameter gradually decreases, which confines and compresses the ionized fluid into the mass spectrometer under a vacuum pressure difference, characterized in that: The needle is located at the center of the tip of the geometric body 3 and can move back and forth, observing and adjusting the stability of the spray through the mass spectrometry signal; One end of the spray voltage is grounded and connected to the needle or the fluid, and the other end is connected to the mass spectrometer; The needle can be in a gas atmosphere G1, and the gas can be air, nitrogen, argon or other inert gases. Some volatile substances that can promote ionization can be added to the gas to promote ionization; The interior of the geometric body 3 forms a shape similar to half of a spindle with a gradually increasing diameter. The needle spray enters at the tip of the geometric body 3 and expands and ionizes rapidly; The atmosphere gas G1 is squeezed towards the inner wall of the geometric body 3 during the expansion of the spray, forming an isolation air curtain between the spray and the inner wall of the geometric body; The geometric body 4 is a geometric body with a gradually decreasing diameter. Looking from the cross-section, the interior is similar to the other half of a spindle shape; At the interface between the geometric bodies 3 and 4, a gas atmosphere G2 can be introduced. The gas can be air, nitrogen, argon or other inert gases, and G2 can form another isolation air curtain along the inner wall of the geometric body 4; The expanded and ionized gas continues to move forward under the action of inertia in the geometric body 4, and is gradually compressed during the process of moving forward under the constraint of the inner wall shape of the geometric body 4 and the G2 isolation air curtain, and enters the mass spectrometer through the tip of the geometric body 4; After the ions enter the mass spectrometer from the geometric body 4, they can be further transmitted inside the mass spectrometer through an ion transfer tube or an ion lens. The geometric body 4 can also be directly connected to the ion optical path inside the instrument; Among them, the gas pressures of G1 and G2 can be adjusted by observing the mass spectrometry signal to obtain the gas pressure with the best mass spectrometry signal; The overlapping degree and relative position of the geometric bodies 3 and 4 can be adjusted by observing the mass spectrometry signal to obtain the relative position with the best mass spectrometry signal; The geometric body 4 can be partially hollowed out to better form a pressure difference under vacuum and confine the movement of the gas; At the interface between the geometric body 4 and the mass spectrometer inlet, a pressure G3 can be introduced to help form a more stable mass spectrometry signal.

2. An ionization device according to claim 1, characterized in that, The material of the geometric body can be metal, ceramic, plastic, glass, and they can be insulated from each other.

3. An ionization device according to claim 1, characterized in that, The geometric body 4 can be wholly or partly inside an ion funnel or a conical multi-pole rod, or directly replaced by it, using an electric field to further focus the ions.

4. An ionization device according to claim 1, characterized in that, The gas and the geometric body can be heated to help ionization.

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