Electron impact ionization source

Abstract

The present invention discloses an electron impact ionization source, relating to the field of ionization technology. The electron impact ionization source at least includes a first ionization chamber, a second ionization chamber and a sample introduction control member; the first ionization chamber is provided with a first sample introduction port; the second ionization chamber is communicated with the first ionization chamber, and the second ionization chamber is provided with a second sample introduction port; the sample introduction control member is respectively communicated with the first sample introduction port and the second sample introduction port and is adapted to introduce a sample to be measured, and the sample introduction control member is used to control the sample to be measured to enter the first ionization chamber and / or the second ionization chamber. The present invention improves the structure of the electron impact ionization source, improves the adaptability of the electron impact ionization source to different samples. The electron impact ionization source has four ionization modes, which can meet different ionization requirements, so as to meet the analysis requirements in different fields. In addition, the high service life and high ionization efficiency of the ion source are effectively guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of ionization technology, and particularly to an electron bombardment ionization source. Background Art

[0002] A mass spectrometer is a scientific instrument for analyzing the components of chemical substances. Its working method is to ionize the molecules of the analyte by certain means, and then screen and measure the ions through an ion optical system. A mass spectrometer usually consists of an injection system, an ion source, a mass analyzer, a detector, a vacuum system, an electronic control system, etc.

[0003] The ion source is a key component in a mass spectrometer, and its function is to ionize the gaseous sample molecules introduced by the injection system. The ionization of sample molecules is the primary link in mass spectrometry. The performance of the ion source has a significant impact on many indicators of the instrument. Whether the sample molecules can be effectively ionized will directly affect important indicators such as the types of detectable substances, detection limits, and sensitivity. The electron bombardment ionization source is a widely used ion source. Its basic principle is that the filament emits electrons, the accelerating electric field accelerates the electrons, and the high-energy electrons bombard the analyte molecules to cause the analyte molecules to ionize.

[0004] In recent years, with the progress of science and technology and the increase in application requirements, higher requirements have been put forward for mass spectrometry detection. In practical applications, the analytes to be measured are diverse, and different samples have different ionization requirements for the mass spectrometer. For example, high-concentration and high-throughput injection samples require the ion source to have a higher load capacity and be more resistant to contamination, low-concentration samples require the ion source to have a higher ionization efficiency, and unknown mixed samples require the ion source to perform specific ionization to improve the accuracy of qualitative analysis.

[0005] The existing mass spectrometers use a general-purpose single ionization chamber ionization source for electron bombardment, which cannot perform different ionization modes for analytes with different requirements. The adaptability of the electron bombardment ionization source to different samples is poor, resulting in the ion source being easily contaminated when dealing with high-concentration samples and having insufficient ionization efficiency when dealing with low-concentration samples, affecting the accuracy of qualitative and quantitative analysis. Summary of the Invention

[0006] The main purpose of the present invention is to provide an electron bombardment ionization source, aiming to improve the adaptability of the electron bombardment ionization source to different samples to meet different ionization requirements.

[0007] To achieve the above object, the present invention provides an electron bombardment ionization source, which at least includes:

[0008] A first ionization chamber provided with a first injection port;

[0009] A second ionization chamber communicating with the first ionization chamber, the second ionization chamber being provided with a second injection port; and

[0010] An injection control component, which is respectively communicated with the first injection port and the second injection port and is adapted to introduce a sample to be measured, and the injection control component is used to control the sample to be measured to enter the first ionization chamber and / or the second ionization chamber.

[0011] Optionally, the injection control component is a sample switching valve, and the sample switching valve is used to control the flow direction of the sample to be measured; and / or

[0012] The volume of the first ionization chamber is larger than the volume of the second ionization chamber.

[0013] Optionally, the electron bombardment ionization source further includes a first filament group disposed in the first ionization chamber and a second filament group disposed in the second ionization chamber, and both the first filament group and the second filament group include two filaments disposed opposite to each other.

[0014] Optionally, the electron bombardment ionization source further includes an extraction assembly. The second ionization chamber is provided with a sample outlet. The extraction assembly is communicated with the sample outlet and is adapted to be communicated with a mass analyzer. The extraction assembly is used to extract the fragment ions generated by ionization; the extraction assembly includes an extraction lens, a focusing lens and an ejection lens which are sequentially arranged at intervals. The extraction lens is used to extract the fragment ions from the sample outlet, the focusing lens is used to focus the fragment ions, and the ejection lens is used to extract the fragment ions to the mass analyzer; and / or

[0015] The electron bombardment ionization source further includes a repulsion electrode. The repulsion electrode is disposed in the first ionization chamber or forms the chamber wall on one side of the first ionization chamber, and the repulsion electrode is used to push the generated fragment ions to the sample outlet.

[0016] Optionally, the electron bombardment ionization source has at least 4 working modes: a high-throughput mode, a high-sensitivity mode, a secondary ionization mode and a qualitative mode;

[0017] When the high-throughput mode is adopted, the injection control component controls the sample to be measured to be introduced into the first ionization chamber, and the first ionization chamber works so that the sample to be measured collides with electrons in the first ionization chamber;

[0018] When the high-sensitivity mode is adopted, the injection control component controls the sample to be measured to be introduced into the second ionization chamber, and the second ionization chamber starts ionization work so that the sample to be measured collides with electrons in the second ionization chamber;

[0019] When adopting the secondary ionization mode, the sample introduction control component controls the introduction of the sample to be measured into the first ionization chamber, and the first ionization chamber and the second ionization chamber start ionization work simultaneously, so that the sample to be measured collides successively in the first ionization chamber and the second ionization chamber.

[0020] When adopting the qualitative mode, the sample to be measured is a mixed sample. The sample introduction control component controls the introduction of the sample to be measured into the first ionization chamber. The first ionization chamber starts the soft ionization mode and the electron energy gradually increases, and the second ionization chamber starts the hard ionization mode, so that the substances in the sample to be measured are gradually subjected to soft ionization to form molecular ions, and then enter the second ionization chamber for hard ionization to generate fragment ions.

[0021] Optionally, when adopting the qualitative mode, the electron energy of the first ionization chamber is 7 eV to 20 eV, and it is scanned from 7 eV to 20 eV with a scanning step of 0.1 eV, and the electron energy of the second ionization chamber is 70 eV.

[0022] Optionally, when adopting the high-throughput mode, a zero-potential voltage is applied to the first ionization chamber and a negative voltage is applied to the second ionization chamber to introduce fragment ions into the second ionization chamber.

[0023] Optionally, when adopting the high-sensitivity mode, a positive voltage is applied to the first ionization chamber and a zero-potential voltage is applied to the second ionization chamber to push the fragment ions into the second ionization chamber.

[0024] Optionally, when adopting the secondary ionization mode, a zero-potential voltage is applied to the first ionization chamber and a negative voltage is applied to the second ionization chamber to enable the fragment ions to enter the second ionization chamber from the first ionization chamber.

[0025] Optionally, when adopting the qualitative mode, a zero-potential voltage is applied to the first ionization chamber and a negative voltage is applied to the second ionization chamber to introduce the molecular ions into the second ionization chamber.

[0026] In the technical solution of the present invention, the electron impact ionization source includes a first ionization chamber, a second ionization chamber and a sample injection control member; the first ionization chamber is provided with a first sample injection port; the second ionization chamber is communicated with the first ionization chamber, and the second ionization chamber is provided with a second sample injection port; the sample injection control member is respectively communicated with the first sample injection port and the second sample injection port and is adapted to introduce a sample to be measured, and the sample injection control member is used to control the sample to be measured to enter the first ionization chamber and / or the second ionization chamber. It can be understood that the present invention improves the structure of the electron impact ionization source. By using the sample injection control member to determine the flow direction of the sample to be measured to the first ionization chamber or the second ionization chamber and setting two independently controllable ionization chambers to set different ionization modes, the adaptability of the electron impact ionization source to different samples is greatly improved. For different samples, suitable ionization methods can be adopted to meet different ionization requirements, thus meeting the analysis requirements in different fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0028] Figure 1 It is a schematic structural diagram of an embodiment of the electron impact ionization source of the present invention;

[0029] Figure 2 It is an application schematic diagram of the electron impact ionization source of the present invention in the high-throughput mode;

[0030] Figure 3 It is an application schematic diagram of the electron impact ionization source of the present invention in the high-sensitivity mode;

[0031] Figure 4 It is an application schematic diagram of the electron impact ionization source of the present invention in the secondary ionization mode;

[0032] Figure 5 It is an application schematic diagram of the electron impact ionization source of the present invention in the qualitative mode.

[0033] Explanation of the reference numerals in the drawings:

[0034] 10. First ionization chamber; 20. Second ionization chamber; 30. Sampling control component; 10a. First sampling port; 20a. Second sampling port; 11. First filament group; 12. Repelling electrode; 21. Second filament group; 20b. Sample outlet; 41. Extraction lens; 42. Focusing lens; 43. Ejection lens; a. Electron; b. Sample to be measured; c. Fragment ion; b1. First substance; b2. Second substance; c1. Molecular ion of the first substance; c2. Mixed fragment ion.

[0035] The realization of the object, functional features and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] It should be noted that all the directional indications (such as up, down, left, right, front, back,...) in the embodiments of the present invention are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0038] In the description of the present invention, it should also be noted that, unless otherwise clearly defined and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0039] In addition, the descriptions involving "first", "second", etc. in the present invention are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text is that it includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or the solution where A and B are satisfied simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on what can be achieved by those of ordinary skill in the art. When the combination of technical solutions results in contradictions or cannot be achieved, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0040] The present invention provides an electron impact ionization source.

[0041] Referring to Figure 1 and Figure 2 In an embodiment of the present invention, the electron impact ionization source includes a first ionization chamber 10, a second ionization chamber 20, and a sample injection control member 30; the first ionization chamber 10 is provided with a first sample injection port 10a; the second ionization chamber 20 is communicated with the first ionization chamber 10, and the second ionization chamber 20 is provided with a second sample injection port 20a; the sample injection control member 30 is respectively communicated with the first sample injection port 10a and the second sample injection port 20a and is adapted to introduce a sample to be measured b, and the sample injection control member 30 is used to control the sample to be measured b to enter the first ionization chamber 10 and / or the second ionization chamber 20.

[0042] In addition, the electron impact ionization source of the present invention can also be provided with more ionization chambers to achieve more ionization modes, so as to meet the ionization requirements in more scenarios. In other words, the control of introducing the sample to be measured b by the sample injection control member 30 for two or more successively communicated ionization chambers all falls within the scope of the technical solutions of the present invention.

[0043] In this embodiment, both the first ionization chamber 10 and the second ionization chamber 20 can adopt the cross bombardment method. The electron impact ionization source further includes a first filament group 11 provided in the first ionization chamber 10 and a second filament group 21 provided in the second ionization chamber 20. Both the first filament group 11 and the second filament group 21 include two filaments arranged oppositely, a total of four filaments. The energy of the electrons a entering the ionization chamber can be controlled by controlling the voltage of the filaments, so as to meet the ionization requirements of different samples to be measured b. To improve the ionization effect of cross bombardment, as Figure 1 shown, the first sample injection port 10a and the second sample injection port 20a can be respectively arranged in the middle of their respective ionization chambers, and the two filaments of each ionization chamber are respectively arranged on both sides of the sample injection port.

[0044] In this embodiment, the sample injection control member 30 may be a sample switching valve or other devices that can effectively control the sample flow direction, which is not limited here.

[0045] It can be understood that the present invention improves the structure of the electron bombardment ionization source. By determining the flow direction of the sample to be measured b to the first ionization chamber 10 or the second ionization chamber 20 through the sample injection control member 30 and setting two independently controllable ionization chambers to set different ionization modes, the adaptability of the electron bombardment ionization source to different samples is greatly improved. For different samples, suitable ionization methods can be adopted to meet different ionization requirements, thereby meeting the analysis requirements in different fields.

[0046] In some embodiments, referring to Figures 2 to 5 , the volume of the first ionization chamber 10 can be set to be larger than the volume of the second ionization chamber 20. The main purpose is:

[0047] In some cases, as Figure 2 shown, the sample to be measured b is injected into the first ionization chamber 10 with a larger volume, and the ionization is controlled to occur in the first ionization chamber 10. Since the first ionization chamber 10 has a large volume and can carry more analyte molecules, it can effectively ensure that the instrument is less contaminated and the stability of the instrument is guaranteed under the condition of high-concentration and high-throughput sample injection.

[0048] In some other cases, as Figure 3 shown, when the ionization concentration of the sample to be measured b is low and the sample injection volume is small, the sample to be measured b is injected into the second ionization chamber 20 with a smaller volume, and the ionization is controlled to occur in the second ionization chamber 20. Since the volume of the second ionization chamber 20 is small, the sample to be measured b will not diffuse extensively, and the analyte molecules of the sample to be measured b are more concentrated, and the probability of their collision with the electrons a is greater, which helps to improve the ionization efficiency; moreover, the small-volume ionization chamber can ensure that the generated fragment ions c have a more concentrated spatial distribution and energy distribution, making the ion energy more concentrated, which can ensure the high transmission efficiency of the ions, thereby improving the sensitivity of the instrument.

[0049] In addition, in some other cases, as Figure 4 shown, the sample to be measured b is injected into the first ionization chamber 10 with a larger volume, and the ionization occurs in both the first ionization chamber 10 and the second ionization chamber 20. This ion source has a higher ionization efficiency. Under the condition of high-concentration and high-throughput sample injection, it can not only ensure that the instrument is less contaminated but also ensure a higher ionization efficiency, improving the signal response of the instrument to high-concentration samples.

[0050] To further improve the ionization efficiency, mainly referring to Figure 1 and Figure 2, in one embodiment, the electron bombardment ionization source may further include an extraction assembly. The second ionization chamber 20 is provided with a sample outlet 20b. The extraction assembly is communicated with the sample outlet 20b and is adapted to be communicated with a mass analyzer. The extraction assembly is used to extract the fragmented ions c generated by ionization; the extraction assembly includes an extraction lens 41, a focusing lens 42, and an ejection lens 43 which are sequentially arranged at intervals. The extraction lens 41 is used to extract the fragmented ions c from the sample outlet 20b, the focusing lens 42 is used to focus the fragmented ions c, and the ejection lens 43 is used to extract the fragmented ions c to the mass analyzer.

[0051] Further, referring to Figure 1 and Figure 2 , the electron bombardment ionization source may further include a repulsion electrode 12. The repulsion electrode 12 is arranged in the first ionization chamber 10 or forms the chamber wall on one side of the first ionization chamber 10. The repulsion electrode 12 is used to push the generated fragmented ions c to the sample outlet 20b. Such a setting helps to further improve the ionization effect of the electron bombardment ionization source.

[0052] As Figure 1 and Figure 2 shown, when the electron bombardment ionization source works, the sample to be measured b first enters the sample switching valve. The sample switching valve switches to determine whether to introduce the sample into the first injection port 10a or the second injection port 20a. The sample enters the first ionization chamber 10 or the second ionization chamber 20 through the injection port. Each ionization chamber adopts a double-filament structure and is symmetrically placed around the ionization chamber. One filament can be turned on each time it works. The electrons a emitted by the filament enter the ionization chamber through acceleration to form a high-energy electron beam (generally, the acceleration voltage is 70V, so the energy of the high-energy electron beam is generally 70eV). The high-energy electron beam collides with the molecules of the sample to be measured b entering the ionization chamber, causing the molecules of the sample to be measured b to ionize and generate fragmented ions c. The repulsion electrode 12 applies a positive voltage to push the generated fragmented ions c to the rear end. The extraction lens 41, the focusing lens 42, and the ejection lens 43 apply negative voltages to extract the fragmented ions c from the ionization chamber and focus the fragmented ion beam. The fragmented ions c finally enter the next-stage mass analyzer through the extraction lens 41, the focusing lens 42, and the ejection lens 43.

[0053] In some embodiments, as Figures 2 to 5 shown, the electron bombardment ionization source proposed by the present invention has at least 4 working modes: high-throughput mode, high-sensitivity mode, secondary ionization mode, and qualitative mode. These 4 working modes respectively correspond to the following 4 groups of control methods:

[0054] 1) When the high-throughput mode is adopted, mainly referring to Figure 2, the sample introduction control member 30 controls the introduction of the sample to be measured b into the first ionization chamber 10, and the first ionization chamber 10 operates to cause the sample to be measured b to collide with electrons a in the first ionization chamber 10.

[0055] In the high-throughput mode, the sample to be measured b is introduced into the first ionization chamber 10, and the filament of the first ionization chamber 10 is turned on. Electrons a collide with the molecules of the sample to be measured b in the first ionization chamber 10 to form fragment ions c. At this time, a zero-potential voltage is applied to the first ionization chamber 10, and a negative voltage is applied to the second ionization chamber 20. For the first ionization chamber 10, the second ionization chamber 20 acts like the extraction lens 41 described above and can introduce the fragment ions c into the second ionization chamber 20, and then into the extraction lens 41, the focusing lens 42, the ejection lens 43, and finally into the next-stage mass analyzer.

[0056] It can be understood that in this mode, the sample to be measured b is injected into the first ionization chamber 10 with a larger volume, and ionization occurs in the first ionization chamber 10. Since the first ionization chamber 10 has a larger volume and can carry more analyte molecules, it can ensure that the instrument is less contaminated and the stability of the instrument is guaranteed under the conditions of large-concentration and high-throughput sample introduction.

[0057] 2) When the high-sensitivity mode is adopted, mainly refer to Figure 3 , the sample introduction control member 30 controls the introduction of the sample to be measured b into the second ionization chamber 20, and the second ionization chamber 20 starts the ionization operation to cause the sample to be measured b to collide with electrons a in the second ionization chamber 20.

[0058] In the high-sensitivity mode, the sample to be measured b is introduced into the second ionization chamber 20, and the filament of the second ionization chamber 20 is turned on. Electrons a collide with the molecules of the sample to be measured b in the second ionization chamber 20 to form fragment ions c. At this time, a positive voltage is applied to the first ionization chamber 10, and a zero-potential voltage is applied to the second ionization chamber 20. For the second ionization chamber 20, the first ionization chamber 10 acts like the repulsion electrode 12 and can push the fragment ions c towards the extraction lens 41, the focusing lens 42, the ejection lens 43, and finally into the next-stage mass analyzer.

[0059] It can be understood that in this mode, the sample to be measured b is injected into the second ionization chamber 20 with a smaller volume, and ionization occurs in the second ionization chamber 20. Since the second ionization chamber 20 has a smaller volume, the sample to be measured b will not spread extensively, the sample molecules are more concentrated, and the probability of their collision with electrons a is greater, which helps to improve the ionization efficiency; moreover, the small-volume ionization chamber can ensure that the generated fragment ions c have a more concentrated spatial distribution and energy distribution, making the ion energy more concentrated and ensuring a high ion transmission efficiency, thereby improving the sensitivity of the instrument. This mode is suitable for samples with a lower ionization concentration and a smaller sample injection volume.

[0060] 3) When adopting the secondary ionization mode, mainly refer to Figure 4 , the sample introduction control member 30 controls the introduction of the sample b to be measured into the first ionization chamber 10. The first ionization chamber 10 and the second ionization chamber 20 are simultaneously turned on for ionization work, so that the sample b to be measured collides with the electrons a in the first ionization chamber 10 and the second ionization chamber 20 successively.

[0061] In the secondary ionization mode, the sample b to be measured is introduced into the first ionization chamber 10, and the filaments of the first ionization chamber 10 and the second ionization chamber 20 are simultaneously turned on. The electrons a collide with the molecules of the sample b to be measured in the first ionization chamber 10 to form fragment ions c. At this time, a zero potential voltage is applied to the first ionization chamber 10, and a small negative voltage is applied to the second ionization chamber 20. The fragment ions c enter the second ionization chamber 20 from the first ionization chamber 10, and a small amount of un-ionized molecules will be carried into the second ionization chamber 20. The high-energy electrons a in the second ionization chamber 20 collide with these un-ionized molecules to form secondary ionization, making the sample ionized more fully. After secondary ionization, the fragment ions c pass through the extraction lens 41, the focusing lens 42, and the ejection lens 43, and finally enter the next-stage mass analyzer.

[0062] It can be understood that in this mode, the sample b to be measured is injected into the first ionization chamber 10 with a larger volume, and ionization occurs in the first ionization chamber 10 and the second ionization chamber 20. This mode has a higher ionization efficiency than the high-throughput mode. In the case of large-concentration and high-throughput sample introduction, it can not only ensure that the instrument is less contaminated, but also ensure a higher ionization efficiency, significantly improving the signal response of the instrument to high-concentration samples.

[0063] 4) When adopting the qualitative mode, mainly refer to Figure 5 , the sample b to be measured is a mixed sample. The sample introduction control member 30 controls the introduction of the sample b to be measured into the first ionization chamber 10. The first ionization chamber 10 turns on the soft ionization mode and controls the energy of the electrons a emitted by the filament to gradually increase. The second ionization chamber 20 turns on the hard ionization mode, so that the substances of the sample b to be measured are gradually subjected to soft ionization to form molecular ions, and then enter the second ionization chamber 20 for hard ionization to generate fragment ions c. Among them, the energy of the electrons a in the first ionization chamber 10 can be set to 7 eV to 20 eV, and scanned from 7 eV to 20 eV with a scanning step of 0.1 eV. The energy of the electrons a in the second ionization chamber 20 can be set to 70 eV.

[0064] In the qualitative mode, the sample b to be measured is introduced into the first ionization chamber 10. The sample b to be measured is a mixed sample including a first substance b1 and a second substance b2. At the same time, the filaments of the first ionization chamber 10 and the second ionization chamber 20 are turned on. The filament of the first ionization chamber 10 adopts a soft ionization mode, that is, the energy of the electron beam generated by the filament of the first ionization chamber 10 is set to 7 eV to 20 eV (the ionization energy of general gas molecules is in the range of 7 eV to 20 eV, that is, only one electron a is lost, and the ionization energy for generating molecular ions), and the energy of the electron beam emitted by the filament of the second ionization chamber 20 is set to a conventional 70 eV. The energy of the electron beam generated by the filament of the first ionization chamber 10 is scanned from 7 eV to 20 eV with a scanning step of 0.1 eV. When the energy of the electron a in the first ionization chamber 10 is exactly higher than the ionization energy of the first substance b1, the molecules of this substance undergo soft ionization. At this time, only one electron a is lost from the molecules of this substance, forming molecular ions c1 of the first substance. The first ionization chamber 10 is applied with a zero potential voltage, and the second ionization chamber 20 is applied with a small negative voltage. The molecular ions c1 of the first substance enter the second ionization chamber 20 under the action of the electric field, and collide with the high-energy electron beam (70 eV energy) in the second ionization chamber 20 to generate fragment ions c of this substance. The fragment ions c enter the next-stage mass analyzer through the extraction lens 41, the focusing lens 42, and the ejection lens 43 for qualitative analysis.

[0065] As the scanning progresses, the energy of the electron a in the first ionization chamber 10 continues to increase step by step. When its energy is exactly higher than the ionization energy of the second substance b2, the molecules of the first substance b1 and the molecules of the second substance b2 undergo soft ionization, forming mixed molecular ions, that is, molecular ions c1 of the first substance and molecular ions of the second substance (not shown in the figure). The mixed molecular ions enter the second ionization chamber 20 and collide with the high-energy electron beam to generate mixed fragment ions c2 of the first substance b1 and the second substance b2. The mixed fragment ions c2 enter the mass analyzer through the extraction assembly for analysis, generating a mass spectrum.

[0066] It can be understood that in the case where the first substance b1 is known, the second substance b2 can be more accurately qualitatively analyzed. In this mode, various substances in the mixed sample can be analyzed one by one, eliminating the influence of spectral peak overlap during simultaneous injection, and ensuring that the instrument has higher qualitative ability.

[0067] In this embodiment, the high-throughput mode is to introduce the sample b to be measured into the first ionization chamber 10 for primary ionization, and the high-sensitivity mode is to introduce the sample into the second ionization chamber 20 for primary ionization. Since the volume of the first ionization chamber 10 is large, in the high-throughput mode, the ion source is not easily contaminated and is suitable for large-concentration and high-throughput injection. Since the volume of the second ionization chamber 20 is small, in the high-sensitivity mode, the ionization efficiency of the ion source is higher and is suitable for samples with lower concentrations and smaller injection volumes.

[0068] In the secondary ionization mode, the filaments of both ionization chambers emit electrons a with an energy of 70 eV. The sample b to be measured undergoes ionization through cross-collision with electrons a in the first ionization chamber 10, and then is introduced into the second ionization chamber 20. The electron beam in the second ionization chamber 20 undergoes cross-collision with the sample molecules again for deep ionization. Through the two cross-collision ionizations, it can be ensured that the sample is ionized more fully, ensuring that the instrument has a lower detection limit and is suitable for the analysis of trace samples.

[0069] In the qualitative mode, the first ionization chamber 10 adopts a soft ionization mode, and the electron beam energy is scanned from 7 eV to 20 eV with a scanning step of 0.1 eV. The second ionization chamber 20 adopts a conventional 70 eV electron beam. The mixed sample enters the first ionization chamber 10, and the energy of the electrons a in the first ionization chamber 10 gradually increases. When it is just higher than the first ionization energy of a certain substance, the substance is softly ionized to generate molecular ions and enters the second ionization chamber 20. The second ionization chamber 20 uses a 70 eV electron beam to bombard the molecular ions to generate fragment ion peaks, and the mass spectrometry then performs qualitative analysis on the fragment ion peaks. By controlling the energy of the first ionization chamber 10, it can be ensured that the substance molecules in the mixed sample are softly ionized one by one and enter the second ionization chamber 20 one by one, ensuring the accuracy of qualitative analysis.

[0070] For the qualitative mode, a specific embodiment is taken as an example for a detailed introduction:

[0071] In a specific application scenario, the mixed sample contains four substances: oxygen, carbon dioxide, nitrogen, and carbon monoxide (in fact, the specific components of the mixed sample are unknown to the experimenter before the experiment). Under 70 eV ionization, each substance has a standard spectral library. Under low ionization energy, molecules can only be ionized into molecular ions. For example, carbon dioxide is only ionized into a mass spectrometry peak with m / z = 44, oxygen is only ionized into a mass spectrometry peak with m / z = 32, nitrogen is only ionized into a mass spectrometry peak with m / z = 28, and carbon monoxide is only ionized into a mass spectrometry peak with m / z = 28. If this mixture enters a standard ionization source, the standard ionization source is bombarded and ionized by 70 eV electrons a, and the mass spectrometry peaks generated by these 4 substances are superimposed together, making it difficult to analyze (for example, carbon dioxide, nitrogen, and carbon monoxide all have a mass spectrometry peak at m / z = 28. In the standard ionization source, the spectral peaks will be superimposed here, resulting in difficulty in distinguishing the types of substances in this mixture). The mixture is introduced into the first ionization chamber 10 of the electron bombardment ionization source of the present invention. The first ionization chamber 10 scans from 7 eV to 20 eV with a scanning step of 0.1 eV. It is known that the first ionization energies of each substance are different. For example, the first ionization energy of oxygen is 12.2 eV, the first ionization energy of carbon dioxide is 13.8 eV, the first ionization energy of carbon monoxide is 14.0 eV, and the first ionization energy of nitrogen is 15.58 eV. When the energy of the first ionization chamber 10 reaches 12.2 eV, oxygen undergoes soft ionization to produce molecular ions. The molecular ions enter the second ionization chamber 20 under the action of the electric field and collide with 70 eV electrons a to generate fragment ions c. The fragment ions c are detected by the mass analyzer at the back end and analyzed and compared with the spectral library to know that this substance is oxygen. When the energy of the first ionization chamber 10 continues to increase to 13.8 eV, at this time, oxygen and carbon dioxide undergo soft ionization to produce molecular ions. The molecular ions enter the second ionization chamber 20 under the action of the electric field and collide with 70 eV electrons a to generate fragment ions c. The fragment ions c are detected by the mass analyzer at the back end. At this time, the spectral pattern is the superimposed spectral pattern of oxygen and carbon dioxide. Since one substance is known to be oxygen, the superimposed spectral pattern is subtracted from the standard spectral pattern of oxygen to obtain the spectral pattern of carbon dioxide, which is analyzed and compared with the standard spectral library to know that the second substance b2 is carbon dioxide. When the energy of the first ionization chamber 10 continues to increase to 14.0 eV, at this time, oxygen, carbon dioxide, and carbon monoxide undergo soft ionization to produce molecular ions. The molecular ions enter the second ionization chamber 20 under the action of the electric field and collide with 70 eV electrons a to generate fragment ions c. The fragment ions c are detected by the mass analyzer at the back end. At this time, the spectral pattern is the superimposed spectral pattern of oxygen, carbon dioxide, and carbon monoxide. At this time, two substances are known to be oxygen and carbon dioxide. The superimposed spectral pattern is subtracted from the standard spectral patterns of oxygen and carbon dioxide to obtain the spectral pattern of carbon monoxide, which is analyzed and compared with the spectral library to know that the third substance is carbon monoxide. And so on, the fourth substance can be analyzed, which is nitrogen.It can be seen that through the above method, it is possible to perform qualitative analysis on mixed samples containing multiple substances, greatly enhancing the qualitative analysis capability of the instrument.

[0072] In summary, the electron bombardment ionization source of the present invention adopts a dual ionization chamber and a four-filament structure, each ionization chamber can perform electron bombardment ionization independently, and each ionization chamber can adjust the ionization energy independently. In the present invention, the volumes of the two ionization chambers are different, the first ionization chamber 10 is larger in volume, and the second ionization chamber 20 is smaller in volume, and the present invention introduces a sample injection control component 30, which can control the sample to enter any ionization chamber. According to the injection volume and sample type, etc., a suitable ionization chamber can be selected in a targeted manner. For example, when the sample concentration is large, an ionization chamber with a larger volume can be selected, and the sample is not easily adsorbed on the inner wall of the ionization chamber, which can ensure the anti-pollution ability of the ionization chamber. The electron bombardment ionization source has four ionization modes: high-throughput mode, high-sensitivity mode, secondary ionization mode and qualitative mode. Different mass spectrometry data can be obtained by adopting different working modes, and targeted analysis can be performed on the sample b to be tested. For example, in the case of the secondary ionization mode, the instrument can have a lower detection limit, and can detect samples with lower concentrations. In the qualitative mode, the qualitative ability of the instrument can be enhanced. Among them, it should be particularly emphasized that in the qualitative mode, the first ionization chamber 10 adopts a soft ionization method, and gradually ionizes the substances of the sample b to be tested by gradually scanning the energy of the electron a, and gradually enters the second ionization chamber 20. The second ionization chamber 20 adopts a hard ionization method, and the substances to be tested entering the second ionization chamber 20 are subjected to hard ionization analysis to ensure the accuracy of the qualitative analysis. The present invention expands the application scenarios of the electron bombardment ionization source, can ensure that the instrument is not contaminated when high-concentration and high-throughput sampling is carried out, can ensure high ionization efficiency and high sensitivity of the instrument when low-concentration and small-volume sampling is carried out, and can ensure high qualitative ability of the instrument when complex sampling is carried out, thereby improving the versatility of the instrument and being able to meet the analysis needs of different fields.

[0073] The above descriptions are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. An electron bombardment ionization source, characterized in that: At least: A first ionization chamber is provided with a first injection port; a second ionization chamber, connected to the first ionization chamber, the second ionization chamber being provided with a second injection port, and the volume of the first ionization chamber being larger than the volume of the second ionization chamber; as well as An injection control component, which is connected to the first injection port and the second injection port respectively and is suitable for introducing a sample to be tested, and the injection control component is used to control the sample to be tested to enter the first ionization chamber and / or the second ionization chamber; The electron bombardment ionization source has at least four working modes: high flux mode, high sensitivity mode, secondary ionization mode and qualitative mode; When the high-throughput mode is adopted, the sample injection control component controls the sample to be tested to be introduced into the first ionization chamber, and the first ionization chamber works so that the sample to be tested collides with electrons in the first ionization chamber; When the high-sensitivity mode is adopted, the sample injection control component controls the sample to be tested to be introduced into the second ionization chamber, and the second ionization chamber starts ionization work, so that the sample to be tested collides with electrons in the second ionization chamber; When the secondary ionization mode is adopted, the sample injection control component controls the sample to be tested to be introduced into the first ionization chamber, and the first ionization chamber and the second ionization chamber start ionization work at the same time, so that the sample to be tested collides in the first ionization chamber and the second ionization chamber successively; When the qualitative mode is adopted, the sample to be tested is a mixed sample, the injection control component controls the sample to be tested to be introduced into the first ionization chamber, the first ionization chamber starts the soft ionization mode and the electron energy gradually increases, and the second ionization chamber starts the hard ionization mode, so that the substances in the sample to be tested are gradually soft-ionized to form molecular ions, and then enter the second ionization chamber for hard ionization to generate fragment ions.

2. The electron bombardment ionization source according to claim 1, characterized in that: The sample injection control component is a sample switching valve, and the sample switching valve is used to control the flow direction of the sample to be tested.

3. The electron bombardment ionization source according to claim 1, characterized in that: The electron bombardment ionization source further includes a first filament group arranged in the first ionization chamber and a second filament group arranged in the second ionization chamber. The first filament group and the second filament group both include two filaments arranged opposite to each other.

4. The electron bombardment ionization source according to claim 1, characterized in that: The electron bombardment ionization source also includes an extraction component, the second ionization chamber is provided with a sample outlet, the extraction component is connected to the sample outlet and is suitable for being connected to a mass analyzer, and the extraction component is used to extract the fragment ions generated by ionization; the extraction component includes an extraction lens, a focusing lens and an ejection lens which are sequentially arranged at intervals, the extraction lens is used to extract the fragment ions from the sample outlet, the focusing lens is used to bunch the fragment ions, and the ejection lens is used to extract the fragment ions to the mass analyzer; and / or The electron bombardment ionization source further includes a repeller electrode, which is disposed in the first ionization chamber or constitutes a chamber wall on one side of the first ionization chamber, and is used to push the generated fragment ions toward the sample outlet.

5. The electron bombardment ionization source according to claim 1, characterized in that: When the qualitative mode is adopted, the electron energy of the first ionization chamber is 7eV~20eV, and is scanned from 7eV to 20eV with a scanning step of 0.1eV. The electron energy of the second ionization chamber is 70eV.

6. The electron bombardment ionization source according to claim 1, characterized in that: When the high-throughput mode is adopted, a zero potential voltage is applied to the first ionization chamber, and a negative voltage is applied to the second ionization chamber, so as to introduce fragment ions into the second ionization chamber.

7. The electron bombardment ionization source according to claim 1, characterized in that: When the high-sensitivity mode is adopted, a positive voltage is applied to the first ionization chamber, and a zero potential voltage is applied to the second ionization chamber, so as to push the fragment ions into the second ionization chamber.

8. The electron bombardment ionization source according to claim 1, characterized in that: When the secondary ionization mode is adopted, a zero potential voltage is applied to the first ionization chamber, and a negative voltage is applied to the second ionization chamber, so that fragment ions enter from the first ionization chamber into the second ionization chamber.

9. The electron bombardment ionization source according to claim 1, characterized in that: When the qualitative mode is adopted, a zero potential voltage is applied to the first ionization chamber, and a negative voltage is applied to the second ionization chamber, so as to introduce molecular ions into the second ionization chamber.

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