A high-field asymmetric waveform ion mobility spectrometer and method with dual ion sources

Abstract

The present invention provides a high-field asymmetric waveform ion mobility spectrometer and method with a dual ion source. The mobility spectrometer includes: a dual ion source assembly, a FAIMS analyzer, and a data acquisition and control unit; the dual ion source assembly includes an ultraviolet light ion source and a gas discharge ion source; the input end of the data acquisition and control unit is connected to the output end of the FAIMS analyzer, and the output end of the data acquisition and control unit is respectively connected to the ultraviolet light ion source and the gas discharge ion source; the data acquisition and control unit is used to control the working mode of the dual ion source assembly and collect and process the electrical signals generated by ion migration inside the FAIMS analyzer. The present invention utilizes the differences in the ionization products of the two ion sources to expand the range and accuracy of analyzable compounds, and realizes the measurement of FAIMS in multiple modes while or by switching the ion sources.

Description

Technical Field

[0001] The present invention relates to the technical field of gas-phase ion analysis, and particularly relates to a high-field asymmetric waveform ion mobility spectrometer and method with a dual ion source. Background Art

[0002] High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) is a gas-phase ion separation technology operating in an atmospheric pressure environment, which uses the non-linear variation of the mobility of different ions under a high-intensity electric field to achieve ion identification. Due to its high sensitivity, fast detection speed, easy miniaturization, simple operation and no need for sample pretreatment, high-field asymmetric waveform ion mobility spectrometry has been applied in the fields of environmental monitoring, food safety, medical health and public safety. The measurement result of a high-field asymmetric waveform ion mobility spectrometer is closely related to the behavior of sample component ions. The ionization of sample components is the most basic step for FAIMS detection, and the component that realizes this function is called an ion source. In addition to the initial ion formation step, subsequent ion behaviors such as the duration of ion existence and further reactions in the carrier gas will also affect the measurement result of the high-field asymmetric waveform ion mobility spectrometer.

[0003] 63 The Ni ionization source is commonly used for the ionization of sample components in a high-field asymmetric waveform ion mobility spectrometer, and has the characteristics of high ionization efficiency, stability and long service life. However, 63 Since the Ni ionization source is a radioactive source, there are strict regulations and restrictions on its transportation, processing and use, and it cannot be widely promoted. In addition 63 The Ni source cannot accurately control the generation of ion current, and the magnitude of the ion current directly affects the sensitivity and resolution of the high-field asymmetric waveform ion mobility spectrometer.

[0004] Non-radioactive ion sources, such as gas discharge ion sources (GD) and ultraviolet light ion sources (UV), have gradually become alternative solutions. The gas discharge ion source uses the gas discharge energy under an extremely asymmetric waveform electric field to ionize sample molecules, and has the advantages of simple structure, high ionization energy and no radiation, and has broad development prospects in the field of ion sources of ion mobility spectrometers. The ionization efficiency of the gas discharge ion source is closely related to the charge affinity of sample molecules, making it particularly suitable for the highly sensitive and high-abundance ionization of polar compounds such as alcohols and ammonia. On the other hand, due to the different electric field intensities around the gas discharge electrode, product ions and cluster ions can be formed through different processes, and the formation of product ions is also affected by ion-molecule reactions. Therefore, the sample ionization products are complex, which is not conducive to the later identification of the FAIMS system.

[0005] The ultraviolet light ion source is based on the principle that ions are formed by the collision of emitted photons with neutral sample molecules. It is known from the literature that the most probable ionization pathway for sample molecule M provides M + product ions. This soft ionization method results in fewer ion fragments, clean ionization products, and high ionization efficiency. The ionization of the ultraviolet light ion source does not depend on charge affinity and is one of the main means for highly sensitive ionization of non-polar compounds. Combining with FAIMS technology, on-site highly sensitive detection of non-polar substances such as benzene and n-hexane has been achieved. However, the ionization condition of the ultraviolet light ion source is whether the photon energy exceeds the ionization energy of the sample molecule, which limits the range of ionizable compounds.

[0006] Currently, there have been reports on replacing the ion source during the FAIMS detection process to take advantage of the strengths of each ion source. For example, Miller et al. used an ultraviolet light ion source and a radioactive ion source respectively to complete sample ionization and verified the high-performance chemical detection of the first microelectromechanical system (MEMS) radio frequency ion mobility spectrometer (rf-IMS); Li Hua et al. used a gas discharge ion source and an ultraviolet lamp ion source successively as the ion source in the experiment to obtain FAIMS spectra to study the differences in generated ions. These methods of replacing the ion source have problems such as difficulty in ensuring the consistent relative position of the ion source and replacing the hardware source, which pose challenges to the control of experimental parameters.

[0007] Therefore, it is of great significance to design and implement a high-field asymmetric waveform ion mobility spectrometer with a wide range of analyzable compounds, high sensitivity, and high specificity. Summary of the Invention

[0008] To solve the deficiencies in the prior art, the present invention provides a high-field asymmetric waveform ion mobility spectrometer and method with a dual ion source.

[0009] In the first aspect of the present invention, a high-field asymmetric waveform ion mobility spectrometer with a dual ion source is provided. The ion mobility spectrometer includes:

[0010] a dual ion source assembly, a FAIMS analyzer, and a data acquisition and control unit;

[0011] The dual ion source assembly includes an ultraviolet light ion source and a gas discharge ion source;

[0012] The input end of the data acquisition and control unit is connected to the output end of the FAIMS analyzer, and the output end of the data acquisition and control unit is respectively connected to the ultraviolet light ion source and the gas discharge ion source;

[0013] The data acquisition and control unit is used to control the working mode of the dual ion source assembly and collect and process the electrical signals generated by ion migration inside the FAIMS analyzer.

[0014] Furthermore, the dual ion source assembly further includes an ionization cavity formed by a first migration tube plate and a second migration tube plate; the ultraviolet light ion source and the gas discharge ion source are both installed on the ionization cavity.

[0015] Furthermore, the ultraviolet light ion source is fixed on the first migration tube plate through a first fixture plate.

[0016] Furthermore, the gas discharge ion source is fixed on the second migration tube plate through a second fixture plate.

[0017] Furthermore, the gas discharge ion source includes: a gas discharge ground electrode provided on the first migration tube plate, an insulating base provided on the second migration tube plate, and a gas discharge needle electrode penetrating and installed in the insulating base;

[0018] The gas discharge ground electrode is a copper ring, which is penetrated and installed on the first migration tube plate;

[0019] One end of the gas discharge needle electrode extends into the ionization cavity, and the other end is located outside the ionization cavity for external connection to a circuit;

[0020] The gas discharge ion source and the ultraviolet light ion source are correspondingly arranged, and the bottom window of the ultraviolet light ion source is directly opposite to the inner hole opened on the gas discharge ground electrode.

[0021] Through the combination of the first fixture plate and the second fixture plate, the gas discharge ion source and the ultraviolet light ion source are maintained at the same relative position of the FAIMS analyzer.

[0022] Furthermore, both the first migration tube plate and the second migration tube plate are of flat plate structure, and their materials are PCB or glass material.

[0023] Furthermore, the ultraviolet light ion source is connected to the output end of the data acquisition and control unit through a first switch;

[0024] The gas discharge ion source is connected to the output end of the data acquisition and control unit through a second switch;

[0025] Both the first switch and the second switch are digital control switches.

[0026] Furthermore, the FAIMS analyzer includes correspondingly arranged deflection electrodes and detection electrodes;

[0027] The detection electrode is used to collect ion detection results.

[0028] Further, the data acquisition control unit includes a DC voltage module, a weak signal detector, a data acquisition card, and a computer;

[0029] The input end of the DC voltage module is connected to the output end of the data acquisition card, and the output end of the DC voltage module is connected to the deflection electrode;

[0030] The input end of the weak signal detector is connected to the detection electrode, and the output end of the weak signal detector is connected to the input end of the data acquisition card;

[0031] The output end of the data acquisition card is connected to the input end of the computer.

[0032] The data acquisition card determines the positive and negative ion detection mode by controlling the positive and negative polarities of the DC voltage module, and also determines the working mode of the dual ion source assembly through the on-off states of the first switch and the second switch, thereby determining the ion source working mode.

[0033] In the second aspect of the present invention, a detection method for a high-field asymmetric waveform ion mobility spectrometer with a dual ion source is provided. The method includes:

[0034] (1) Selection of working mode: Determine the ion source working mode according to the detection requirements;

[0035] (2) Generation and migration of ions: Sample molecules are ionized into charged particles by the dual ion source assembly, and under the action of the carrier gas, the charged particles enter the interior of the FAIMS analyzer;

[0036] (3) Detection of ions: Under the action of the internal electric field of the FAIMS analyzer, the sample characteristic ions among the charged particles are deflected and hit the detection electrode to generate a weak signal, forming a current signal;

[0037] (4) Data visualization and recording: The data acquisition control unit collects the current signal, and performs spectral data display and establishes a spectral database according to the ion source working mode and the collected current signal. The collected spectral data needs to be displayed on the user interface to grasp the experimental results in real time, and the spectral database is established for subsequent analysis.

[0038] Further, the method also includes performing spectral analysis according to the ion source working mode and the obtained spectral database; when performing spectral analysis, the ion source working mode and the spectral database are used as input parameters for input.

[0039] The performing spectral analysis according to the ion source working mode and the obtained spectral database includes:

[0040] (41) Preprocess the sample data according to the ion source working mode and the spectral database; the preprocessing includes normalization and scaling; by performing standardization processing on the original spectral data, standardized data is obtained to improve the efficiency during subsequent principal component analysis operations. The goal of normalization in the preprocessing is to make the mean of the spectral data 0; scaling is to keep the amplitude of the spectral data at the same order of magnitude.

[0041] (42) Use the principal component analysis method to perform dimensionality reduction and feature extraction on the spectral data under different ion source working modes, calculate the principal components and the data restoration rates corresponding to different numbers of principal components; by performing dimensionality reduction and feature extraction processing on the spectral data, low-dimensional features that can represent the main information in the original data are obtained.

[0042] (43) Select the first k principal components PC1, PC2, …, PC k whose data restoration rates are greater than 95% after being processed by the principal component analysis method, and form the feature set Z = {PC1, PC2, …, PC k}. Screen the principal components and data restoration rates calculated in step (42), and select the first k principal components with data restoration rates greater than 95%, which can ensure that the compressed data retains the most important information in the original data.

[0043] (44) Perform visualization and recognition processing on the spectral data and the feature set under different ion source modes. Performing visualization processing on the spectral data in the input spectral database can intuitively compare the ion information under different ion source working modes, such as the number of ions and abundance; performing visualization processing on the feature set obtained in step (43) can intuitively observe the influence of the dual-ion source device on the FAIMS recognition dimension.

[0044] Further, the ion source working mode includes three modes: using any one of the ion sources in the dual-ion source component, using both ion sources in the dual-ion source component simultaneously, and switching between the two ion sources in the dual-ion source component.

[0045] The beneficial effects of the present invention are as follows:

[0046] (1) The present invention makes full use of the unique advantages of the gas discharge ion source and the ultraviolet light ion source, and designs a dual-ion source high-field asymmetric waveform ion mobility spectrometer integrating the gas discharge ion source and the ultraviolet light ion source. This ion mobility spectrometer can select the ion source working mode during the FAIMS operation according to the detection requirements, and there are three working modes to choose from: ① using any one of the ion sources; ② using both ion sources simultaneously; ③ quickly switching between the ion sources, and the range of compounds can be analyzed by using the different expansions of the products of the two ion sources.

[0047] (2) The detection method described in the present invention can switch the working mode of the ion source according to the detection requirements, and can obtain the ion information corresponding to the migration spectrometer under different working modes of the ion source. Since the physical and chemical properties of the substance to be measured are different, the ionization effects of different ion sources will be different. Selecting a suitable working mode of the ion source can improve the ionization effect of the ion source on the substance to be measured.

[0048] (3) The present invention not only expands the range of compounds that can be analyzed by FAIMS without replacing the ion source, but also obtains FAIMS spectral data with higher information richness by changing the working mode of the ion source. In addition, the present invention can improve the recognition dimension of FAIMS under multiple working modes of the ion source by using the dimensionality reduction and feature processing methods of FAIMS data.

[0049] It should be understood that the content described in the summary of the invention is not intended to limit the key or important features of the embodiments of the present invention, nor to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In combination with the accompanying drawings and with reference to the following detailed description, the above and other features, advantages and aspects of the embodiments of the present invention will become more obvious. In the drawings, the same or similar reference numerals represent the same or similar elements, where:

[0051] Figure 1 is a schematic structural diagram of a dual-ion-source high-field asymmetric waveform ion mobility spectrometer in the present invention;

[0052] Figure 2 is a schematic structural diagram of a dual-ion-source assembly in the present invention;

[0053] Figure 3 is a schematic diagram of the detection method of a dual-ion-source high-field asymmetric waveform ion mobility spectrometer in the present invention;

[0054] Figure 4 is a flowchart of the spectral analysis method of a dual-ion-source high-field asymmetric waveform ion mobility spectrometer in the present invention;

[0055] Figure 5a is the FAIMS spectrum of toluene under different working modes of the ion source;

[0056] Figure 5b is a curve graph of the data reduction rate corresponding to the number of principal components processed by PCA; in Figure 5a and Figure 5b , UV represents the use of only an ultraviolet light ion source, GD represents the use of only a gas discharge ion source, and UV and GD represent the simultaneous use of an ultraviolet light ion source and a gas discharge ion source;

[0057] Figure 6a The PCA processing score chart for operating only in the ultraviolet light ion source mode;

[0058] Figure 6b The PCA processing score chart for operating only in the gas discharge ion source mode.

[0059] Among them, the corresponding relationship between the reference numerals in the figures and the component names is as follows:

[0060] 1. Dual ion source assembly, 2. Ultraviolet light ion source, 3. Charged particles, 4. First switch, 5. FAIMS analyzer, 6. DC voltage module, 7. Data acquisition card, 8. Computer, 9. Weak signal detector, 10. Sample characteristic ions, 11. Second switch, 12. Gas discharge ion source, 13. Sample molecules, 14. First fixture plate, 15. Second fixture plate, 5-1. First migration tube plate, 5-2. Second migration tube plate, 5-3. Deflection electrode, 5-4. Detection electrode, 12-1. Gas discharge ground electrode, 12-2. Insulating base, 12-3. Gas discharge needle electrode. Detailed implementation manners

[0061] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, 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 some but not all of the embodiments of the present invention. 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.

[0062] In addition, the term "and / or" in this article is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0063] Next, refer to Figures 1 - 2 to describe the high-field asymmetric waveform ion mobility spectrometer with a dual ion source provided by the embodiments of the present invention.

[0064] As Figure 1 and Figure 2 shown, a high-field asymmetric waveform ion mobility spectrometer with a dual ion source. The ion mobility spectrometer includes:

[0065] Dual ion source assembly 1, FAIMS analyzer 5 and data acquisition and control unit.

[0066] The dual ion source assembly 1 includes an ultraviolet light ion source 2 and a gas discharge ion source 12. Specifically, the dual ion source assembly 1 further includes an ionization cavity composed of a first migration tube plate 5-1 and a second migration tube plate 5-2. The ultraviolet light ion source 2 and the gas discharge ion source 12 are both installed on the ionization cavity.

[0067] The ultraviolet light ion source 2 is connected to the output end of the data acquisition and control unit through a first switch 4; the gas discharge ion source 12 is connected to the output end of the data acquisition and control unit through a second switch 11;

[0068] The output end of the FAIMS analyzer 5 is connected to the input end of the data acquisition and control unit;

[0069] The data acquisition and control unit is used to control the working mode of the dual ion source assembly 1 and collect and process the electrical signals generated by ion migration inside the FAIMS analyzer 5. The data acquisition and control unit is responsible for the control function and the data acquisition function. The data acquisition and control unit controls the on / off of the ultraviolet light ion source 2 and the gas discharge ion source 12 respectively by controlling the on / off of the first switch 4 and the second switch 11, solves the control of the on / off of the ultraviolet light ion source and the gas discharge ion source, and the cooperation of the on / off of the ultraviolet light ion source and the gas discharge ion source realizes multiple ion source working modes.

[0070] By setting the dual ion source assembly, the present invention can integrate the ultraviolet light ion source and the gas discharge ion source into the flat FAIMS at the same time, solves the limitation problem of using the ultraviolet light ion source or the gas discharge ion source alone in the FAIMS, and achieves the effects of expanding the range of analyzable compounds and improving the abundance of spectral information.

[0071] The electrical signals generated by ion migration inside the FAIMS analyzer are transmitted to the input end of the data acquisition and control unit through its output end for collection, solves the conversion problem of ion information to electrical signals, and the data acquisition and control unit collects the electrical signals generated by ions in real time.

[0072] Further, the ultraviolet light ion source 2 is fixed on the first migration tube plate 5-1 through a first fixture plate 14. The first fixture plate is used to fix the ultraviolet light ion source on the FAIMS analyzer 5 and determine the position of the ultraviolet light ion source.

[0073] Further, the gas discharge ion source 12 is fixed on the second migration tube plate 5-2 through a second fixture plate 15. The second fixture plate is used to fix the gas discharge ion source on the FAIMS analyzer 5 and determine the position of the gas discharge ion source.

[0074] Further, the gas discharge ion source 12 includes:

[0075] The gas discharge ground electrode 12-1 disposed on the first migration tube plate 5-1, the insulating base 12-2 disposed on the second migration tube plate 5-2, and the gas discharge needle electrode 12-3 penetrating and installed in the insulating base 12-2;

[0076] The gas discharge ground electrode 12-1 is a copper ring, which is penetratingly installed on the first migration tube plate 5-1;

[0077] One end of the gas discharge needle electrode 12-3 extends into the ionization cavity, and the other end is located outside the ionization cavity for external connection to a circuit;

[0078] The gas discharge ion source 12 is arranged corresponding to the ultraviolet light ion source 2, and the bottom window of the ultraviolet light ion source 2 is directly opposite to the inner hole opened on the gas discharge ground electrode 12-1.

[0079] The combination of the first fixture plate 14 and the second fixture plate 15 keeps the gas discharge ion source 12 and the ultraviolet light ion source 2 in the same relative position of the FAIMS analyzer 5.

[0080] Utilize the processable advantages of FAIMS flat materials to integrate the gas discharge ion source structure, solve the problems of ion generation and ion injection, and realize that the discharge electrode generates reaction ions in the ionization cavity and injects them into the gas stream. Among them, the gas discharge ground electrode is a copper ring penetratingly installed on the first migration tube plate, which is a part of the gas discharge ion source and forms a needle-ring gas discharge structure with the gas discharge needle electrode. One end of the gas discharge needle electrode extends into the ionization cavity for generating reaction ions and injecting them into the gas stream, and the other end is located outside the ionization cavity for external connection to the circuit of the gas discharge, realizing the installation and operation of the discharge electrode. Through the combination of the first fixture plate and the second fixture plate, the ultraviolet light ion source and the gas discharge ion source are kept in the same relative position of the FAIMS analyzer, and the photons emitted by the ultraviolet light ion source reach the ionization cavity through the inner hole of the ring electrode of the needle-ring gas discharge structure. Such a design makes the double ion source assembly structure more compact and ensures that there are no other influencing factors when comparing the two ion sources, solving the problems brought by replacing hardware and different relative positions of the ion sources.

[0081] Furthermore, both the first migration tube plate 5-1 and the second migration tube plate 5-2 are of flat plate structure, and their materials are PCB or glass materials. Utilize the advantages of the compactness and small volume of the flat plate structure to improve the sensitivity and integration of FAIMS. Utilize the advantages of the precise processability of PCB or glass materials to more reasonably integrate the double ion source assembly. Solve the problems of the large volume of the cylindrical FAIMS and the need to replace multiple external ion sources.

[0082] Further, both the first switch 4 and the second switch 11 are digital control switches. The first switch 4 and the second switch 11 are respectively used to control the on / off of the ultraviolet light ion source 2 and the gas discharge ion source 12. Multiple ion source working modes are achieved through the cooperation of the on / off states of the switches.

[0083] Further, the FAIMS analyzer 5 includes a deflection electrode 5-3 and a detection electrode 5-4 which are correspondingly arranged;

[0084] The detection electrode 5-4 is used to collect the detection results of ions.

[0085] Further, the data acquisition control unit includes a DC voltage module 6, a weak signal detector 9, a data acquisition card 7 and a computer 8;

[0086] The input end of the DC voltage module 6 is connected to the output end of the data acquisition card 7, and the output end of the DC voltage module 6 is connected to the deflection electrode 5-3;

[0087] The input end of the weak signal detector 9 is connected to the detection electrode 5-4, and the output end of the weak signal detector 9 is connected to the input end of the data acquisition card 7;

[0088] The output end of the data acquisition card 7 is connected to the input end of the computer 8.

[0089] The data acquisition card 7 determines the positive and negative ion detection modes by controlling the positive and negative polarities of the DC voltage module 6, and also determines the working mode of the dual ion source assembly 1 by controlling the on / off of the first switch 4 and the second switch 11, so as to achieve different ion source working modes.

[0090] The functions of the DC voltage module, the weak signal detector, the data acquisition card and the computer respectively correspond to: voltage control, signal acquisition, instruction processing, signal display and processing. The data acquisition card controls the voltage output by the DC voltage module to change the voltage on the deflection electrode. The weak signal detector converts the ion information collected by the detection electrode into an electrical signal and then transmits it to the data acquisition card for signal acquisition. The data acquisition card transmits the collected signal to the computer and is also responsible for the sending and receiving of system control instructions. The computer is used to display and process the collected signal. The positive and negative ion detection mode refers to detecting positive ions or negative ions. Since the output end of the DC voltage module is connected to the deflection electrode, by changing the positive and negative polarities, either the deflection electrode is at a positive voltage, then the detection electrode attracts positive ions; or it is at a negative voltage, then the detection electrode attracts negative ions. Therefore, by changing the polarity of the DC voltage module, different polar ions can be detected and collected.

[0091] The working principle of the above ion mobility spectrometer is as follows:

[0092] The sample molecule 13 is ionized into charged particles 3 by the dual ion source assembly 1. Among them, the dual ion source assembly 1 includes two ion sources, an ultraviolet photoionization source 2 and a gas discharge ion source 12. The two ion sources are fixed to the outside of the upper plate 5-1 of the migration tube and the lower plate 5-2 of the migration tube through the first fixture plate 14 and the second fixture plate 15. Under the action of the carrier gas, the charged particles 3 enter the interior of the FAIMS analyzer 5. Under the action of the internal electric field, the sample characteristic ions 10 migrate backward. Under the action of the deflection voltage generated by the DC voltage module 6 and applied to the deflection electrode 5-3, the characteristic ions 10 strike the detection electrode 5-4 and generate a weak signal. The weak signal detector 9 detects the current signal and then transmits it to the connected data acquisition card 7. The computer 8 communicates with the data acquisition card 7 to control the system and can perform spectral data display and data analysis. The data acquisition card 7 controls the positive and negative polarities of the DC voltage module 6 to achieve positive and negative ion mode detection, and at the same time controls the on-off of the first switch 4 and the second switch 11 to control the working mode of the dual ion source assembly 1, so as to realize different ion source working modes.

[0093] Figure 3 It is a schematic diagram of the detection method of a dual ion source high-field asymmetric waveform ion mobility spectrometer. For different detection requirements, select the appropriate ion source working mode to achieve high-sensitivity and specific detection of FAIMS without changing the ion source. At the same time, expand the range of compounds that can be analyzed by FAIMS and improve the richness of spectral data. As Figure 3 shown, the method includes the following steps:

[0094] (1) Selection of working mode: Determine the ion source working mode according to the detection requirements. The measurement and control system selects the ion source working mode among the following three modes according to the detection requirements: ① Use any one of the ion sources, ② Use both ion sources at the same time, ③ Quickly switch between the ion sources. Using any one of the ion sources, a determined compound can be detected, and the ion source can be selected according to its physical and chemical properties. For polar compounds, use the gas discharge ion source; for non-polar compounds, use the ultraviolet photoionization source. Using both ion sources at the same time can perform full-range coverage detection on a mixture of polar and non-polar compounds. Quickly switching between the ion sources during the operation of FAIMS can perform specific real-time detection on a mixture of polar and non-polar compounds.

[0095] (2) Generation and migration of ions: The sample molecule is ionized into charged particles by the dual ion source assembly. Under the action of the carrier gas, the charged particles enter the interior of the FAIMS analyzer.

[0096] (3) Detection of ions: Under the action of the internal electric field of the FAIMS analyzer, the sample characteristic ions in the charged particles deflect and strike the detection electrode to generate a weak signal, forming a current signal.

[0097] (4) Data visualization and recording: The data acquisition control unit acquires the current signal, and displays the spectral data and establishes a spectral database according to the ion source working mode and the acquired current signal. Record the FAIMS spectral data under different ion source working modes and establish a database, and then perform spectral analysis.

[0098] Figure 4 It is a flow chart of the spectral analysis method for a dual-ion-source high-field asymmetric waveform ion mobility spectrometer.

[0099] The detection method of the dual-ion-source high-field asymmetric waveform ion mobility spectrometer further includes performing spectral analysis according to the ion source working mode and the obtained spectral database;

[0100] The performing spectral analysis according to the ion source working mode and the obtained spectral database includes:

[0101] (41) Preprocess the sample data according to the ion source working mode and the spectral database; the preprocessing includes normalization and scaling;

[0102] (42) Use the principal component analysis method to reduce the dimension and extract features of the spectral data under different ion source working modes, calculate the principal components and the data reduction rates corresponding to different numbers of principal components;

[0103] (43) Select the first k principal components PC1, PC2,..., PC with a data reduction rate greater than 95% after being processed by the principal component analysis method k , and form a feature set Z = {PC1, PC2,..., PC k};

[0104] (44) Perform visualization and recognition processing on the spectral data and the feature set under different ion source modes.

[0105] Specifically, first, the system inputs the ion source working mode and the spectral database obtained from the experiment.

[0106] Due to the high dimensionality and information redundancy of FAIMS data, it is necessary to compress the data to improve the operation efficiency within the range of retaining the most important original data information. Use the principal component analysis method (PCA) to reduce the dimension and extract features of the spectral data under different ion source working modes. First, preprocess the original data of the sample, mainly normalization and scaling; then perform PCA processing on the preprocessed data, calculate the principal components and the data reduction rates corresponding to different numbers of principal components; select the first k principal components PC1, PC2,..., PC with a data reduction rate greater than 95% after PCA processing k , and form a feature set Z = {PC1, PC2,..., PC k}; Finally, the spectral data and feature sets under different ion source modes are visualized and subsequent identification is carried out.

[0107] The design principle of the present invention is as follows:

[0108] 1. Working principle of the dual ion source assembly

[0109] (1) Ionization principle of the gas discharge ion source

[0110] The ionization principle of the gas discharge ion source is based on the ion-molecule reaction in the gas phase under atmospheric pressure. The electrode emits high-energy primary electrons. In the positive ionization mode, the primary electrons collide with the surrounding carrier gas N2 molecules to ionize them and produce reaction ions, as shown in formula (1).

[0111] N2 + e - → N2 + + 2e - (1)

[0112] N2 under atmospheric pressure + will collide with gas molecules in the carrier gas and produce a series of ionization reactions, as shown in formulas (2) to (5).

[0113] N2 + + 2N2 → N4 + + N2 (2)

[0114] H2O + + H2O → H3O + + OH (3)

[0115] H3O + + H2O + N2 → H + (H2O)2 + N2 (4)

[0116] H + (H2O)2 + H2O + N2 → H + (H2O)3 + N2 (5)

[0117] The above process can be carried out procedurally to produce more hydrated ions H + (H2O) n , and the hydrated ions are the main reaction ions. When the sample molecule M enters the ionization region, the reaction ions collide with it to generate product ions, as shown in formula (6).

[0118] H + (H2O) n + M → MH + (H2O) n + Z → MH + (H2O) n-1 + H2O + Z (6)

[0119] When the concentration is further increased, the protonated monomer (product ion) will also collide with other sample molecules to form a proton-bonded dimer, as shown in Equation (7).

[0120] MH + (H2O) n +M→M2H + (H2O) n-1 +H2O (7)

[0121] (2) Ionization principle of the ultraviolet light ion source

[0122] The ionization principle of the ultraviolet light ion source is that the gas is excited under high pressure to release photons, and the photons directly act on the sample molecules to form positive ions, as follows:

[0123] hv+M→M + +e - (8)

[0124] Or:

[0125] hv+M→M * (9)

[0126] M * →M + +e - (10)

[0127] In the formula: M is the sample molecule; hv is the energy of the photon; M + is the product ion after ionization; M * is the excited state of the sample.

[0128] As can be seen from the above, the product ions finally obtained after the gas-phase sample molecule M is ionized by the gas discharge ion source are mainly MH + (H2O) n and M2H + (H2O) n . The product ions obtained by the ultraviolet light ion source ionizing the sample molecules are mainly M + .

[0129] The products of the two ion sources are different. Therefore, in the following different ion source working modes, the spectra detected by FAIMS are different. For the dual ion source assembly of the present invention, different product ions can be obtained by switching the ion source working mode.

[0130] 2. FAIMS detection principle

[0131] The gas-phase ions generated after ionization enter the interior of the FAIMS analyzer under the action of the carrier gas. Under the action of the electric field (greater than 10,000 V / cm) generated by the high-amplitude high-frequency separation voltage (Dispersion Voltage, DV), the ions are separated due to the change in mobility. At the same time, a DC-scanned compensation voltage (Compensation Voltage, CV) is applied, and the electric field generated by it compensates for the longitudinal displacement of the ions to screen the target ions. The signal intensity of FAIMS corresponding to the compensation voltage is the FAIMS spectrum. It can be seen that in the present invention, under different ion source working modes, due to different ionization products, FAIMS will generate different spectra. The spectra are displayed in real time by a computer to master the experimental results, and the spectral data under different ion source working modes are recorded and a database is established.

[0132] 3. FAIMS Spectrum Analysis

[0133] For the FAIMS database, it is represented by an m×n matrix X, as shown in formula (11). Each row of the matrix represents a sample, each column represents a feature, with a total of m samples and n features.

[0134]

[0135] Principal Component Analysis (PCA) is used to reduce the dimensionality of the features, and k features with a data reduction rate greater than 95% are retained. First, the original data is preprocessed, mainly normalization and scaling, to improve the efficiency during the PCA operation. The data normalization and rescaling are as shown in formula (12).

[0136]

[0137] In the formula, x i (j) refers to the j-th eigenvalue of the i-th sample, u (j) is the mean of the j-th feature of the data set, max(x (j) ) is the maximum value of the j-th feature of the data set, and min(x (j) ) is the minimum value of the j-th feature of the data set.

[0138] For the preprocessed matrix A, PCA processing is performed. First, the covariance matrix is calculated:

[0139]

[0140] In the formula, Σ is the covariance matrix, and the calculation result is an n×n matrix.

[0141] Then, the eigenvectors of the covariance matrix are calculated through singular value decomposition:

[0142] [U, S, V] = svd(∑) (14)

[0143] In the formula, svd is the singular value decomposition operation. Formula (14) has three return values, where U is an n×n matrix. Representing each column of U as a vector, n column vectors u 1 , u 2 , …, u n can be obtained. These vectors are the eigenvectors of the covariance.

[0144] Select the first k vectors to form the principal component eigenmatrix U reduce , that is, U reduce = [u 1 , u 2 , …, u k . Dimension reduction is performed on the preprocessed matrix A:

[0145] Z = AU reduce (15)

[0146] In the formula, Z is an m×k matrix. Therefore, the dimension-reduced data has k features. The value of A linearly projected along the u i direction is called the principal component (PC). Z is expressed as {PC1, PC2, …, PC k}.

[0147] The number of features after dimension reduction, that is, the number of principal components k, can use formula (16) as the constraint condition:

[0148]

[0149] In the formula, a i represents the i-th sample in the preprocessed dataset, represents the i-th sample restored from the compressed data. The numerator part represents the square of the average projection variance, and the denominator part represents the average value of the distances from all preprocessed samples to the origin. The physical meaning of this formula is that the number of principal components k selected makes the distortion of the data after PCA processing less than 5%, that is, the dimension-reduced data can restore 95% of the original data information.

[0150] 4. Case of specific experimental data

[0151] Under different ion source working modes, that is, using only the ultraviolet light ion source (UV), only the gas discharge ion source (GD), and using both the ultraviolet light ion source and the gas discharge ion source (UV and GD) respectively, the FAIMS spectra of toluene and the data reduction rate curves corresponding to the number of principal components processed by PCA are as Figure 5a and Figure 5b shown. From Figure 5aIt can be seen that by adding a gas discharge ion source, the intensity of the spectrum is increased, the number of peaks becomes larger, and the detection sensitivity and resolution of FAIMS are improved.

[0152] PCA is used to process the FAIMS spectral information under different ion source working modes, calculate the principal components and the data reduction rates corresponding to different numbers of principal components. The data reduction rate curve corresponding to the number of principal components after PCA processing is as Figure 5b shown. It can be Figure 5b seen that when only the ultraviolet light ion source (corresponding to the "UV" curve in the figure) is used as the ion source, selecting the first 2 principal components can achieve a data reduction rate greater than 95%. When only the gas discharge ion source (corresponding to the "GD" curve in the figure) or both the ultraviolet light ion source and the gas discharge ion source (corresponding to the "UV and GD" curve in the figure) are used as the ion source, selecting the first 3 principal components can achieve a data reduction rate greater than 95%.

[0153] For the results of PCA processing, under the condition of ensuring a data reduction rate higher than 95%, the first 2 principal components are selected for the FAIMS data processing in the working mode of only using the ultraviolet light ion source, and the first 3 principal components are selected for the FAIMS data processing in the working mode of only using the gas discharge ion source. Then, the PCA processing score plots of benzene, toluene, and xylene under these two ion source working modes are compared. The results are as Figure 6a and Figure 6b shown. Among them, Figure 6a is the two-dimensional plane score plot in the working mode of only using the ultraviolet light ion source, Figure 6b and Figure 6a is the three-dimensional solid score plot in the working mode of only using the gas discharge ion source. It can be seen from Figure 6b that both ion sources have achieved the distinction of the three compounds. Under the condition of a reduction rate higher than 95%, the number of features extracted in the working mode of using the ultraviolet light ion source is 2, while the number of features extracted in the gas discharge ion source mode is 3. By comparing Figure 5b it can be seen that the gas discharge ion source can increase the recognition dimension of FAIMS.

[0154] In the description of this specification, terms such as "connection", "installation", "fixation", etc. should all be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0155] In the description of this specification, the descriptions of the terms "one embodiment", "some embodiments", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0156] The foregoing are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A high-field asymmetric waveform ion mobility spectrometer with a dual ion source, characterized in that, The migration spectrometer includes: a dual ion source assembly, a FAIMS analyzer, and a data acquisition and control unit; The dual ion source assembly includes an ultraviolet light ion source and a gas discharge ion source; The input end of the data acquisition and control unit is connected to the output end of the FAIMS analyzer, and the output end of the data acquisition and control unit is respectively connected to the ultraviolet light ion source and the gas discharge ion source; The data acquisition and control unit is used to control the working mode of the dual ion source assembly and collect and process the electrical signals generated by ion migration inside the FAIMS analyzer; The dual ion source assembly further includes an ionization cavity surrounded by a first migration tube plate and a second migration tube plate; the ultraviolet light ion source and the gas discharge ion source are both installed on the ionization cavity.

2. The migration spectrometer according to claim 1, wherein The ultraviolet light ion source is fixed on the first migration tube plate through a first fixture plate; The gas discharge ion source is fixed on the second migration tube plate through a second fixture plate.

3. The migration spectrometer according to claim 1, wherein The gas discharge ion source includes: a gas discharge ground electrode provided on the first migration tube plate, an insulating base provided on the second migration tube plate, and a gas discharge needle electrode penetrating and installed in the insulating base; The gas discharge ground electrode is a copper ring, which penetrates and is installed on the first migration tube plate; One end of the gas discharge needle electrode extends into the ionization cavity, and the other end is located outside the ionization cavity for external connection to a circuit; The gas discharge ion source is arranged corresponding to the ultraviolet light ion source, and the bottom window of the ultraviolet light ion source is directly opposite to the inner hole opened on the gas discharge ground electrode.

4. The migration spectrometer according to claim 1, wherein Both the first migration tube plate and the second migration tube plate are of a flat plate structure, and their materials are PCB or glass materials.

5. The migration spectrometer according to claim 1, wherein The ultraviolet light ion source is connected to the output end of the data acquisition and control unit through a first switch; The gas discharge ion source is connected to the output end of the data acquisition and control unit through a second switch; Both the first switch and the second switch are digital control switches.

6. The migration spectrometer according to claim 5, wherein The FAIMS analyzer includes a deflection electrode and a detection electrode arranged corresponding to each other; The detection electrode is used to collect ion detection results.

7. The migration spectrometer according to claim 6, wherein The data acquisition and control unit includes a DC voltage module, a weak signal detector, a data acquisition card, and a computer; The input end of the DC voltage module is connected to the output end of the data acquisition card, and the output end of the DC voltage module is connected to the deflection electrode; The input end of the weak signal detector is connected to the detection electrode, and the output end of the weak signal detector is connected to the input end of the data acquisition card; The output end of the data acquisition card is connected to the input end of the computer; The data acquisition card determines the positive and negative ion detection modes by controlling the positive and negative polarities of the DC voltage module, and also determines the working mode of the dual ion source assembly through the on / off states of the first switch and the second switch, thereby determining the ion source working mode.

8. The detection method of the migration spectrometer according to any one of claims 1 to 7, characterized in that The method includes: (1) Selection of working mode: Determine the ion source working mode according to the detection requirements; (2) Generation and migration of ions: Sample molecules are ionized into charged particles by passing through the dual ion source assembly, and under the action of the carrier gas, the charged particles enter the interior of the FAIMS analyzer; (3) Detection of ions: Under the action of the internal electric field of the FAIMS analyzer, the sample characteristic ions among the charged particles deflect and strike the detection electrode to generate a weak signal, forming a current signal; (4) Data visualization and recording: The data acquisition control unit collects the current signal, and displays the spectral data and establishes a spectral database according to the ion source working mode and the collected current signal.

9. The method according to claim 8, characterized in that The method further includes performing spectral analysis according to the ion source working mode and the obtained spectral database; The spectral analysis according to the ion source working mode and the obtained spectral database includes: (41) Preprocess the sample data according to the ion source working mode and the spectral database; the preprocessing includes normalization and scaling; (42) Use the principal component analysis method to reduce the dimension and extract features of the spectral data under different ion source working modes, and calculate the principal components and the data reduction rates corresponding to different numbers of principal components; (43) Select the first k principal components PC1, PC2, …, PCk with a data reduction rate greater than 95% after being processed by the principal component analysis method k , and form a feature set Z = {PC1, PC2, …, PC k}; (44) Perform visualization and recognition processing on the spectral data and the feature set under different ion source modes; the ion source working modes include using any one of the ion sources in the dual ion source assembly, using both ion sources in the dual ion source assembly simultaneously, and switching between the two ion sources in the dual ion source assembly in three modes.

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