Miniaturized portable mass spectrometer based on vacuum ultraviolet photoionization source and analysis method thereof

Abstract

This invention discloses a miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source and its analytical method, relating to the field of mass spectrometry analysis technology. The mass spectrometer includes: a sample introduction and pre-screening module, consisting of a sample introduction system and an intelligent sample pre-screening unit. The sample introduction system enables gas-liquid sample switching. The pre-screening unit collects data through physical and chemical characteristic detection subunits, and outputs target compound type and parameter adjustment instructions after processing by a data analysis subunit. This invention, through the intelligent sample pre-screening unit in the sample introduction and pre-screening module, utilizes physical and chemical characteristic detection subunits to quickly acquire physicochemical characteristic data such as the color spectrum, volatile components, and pH value of the sample. The compound type recognition model built into the data analysis subunit can automatically compare with the sample characteristic database, quickly identify the target compound type, and generate ionization source parameter adjustment instructions, greatly simplifying the operation process and reducing detection time.

Description

Technical Field

[0001] This invention relates to the field of mass spectrometry analysis technology, specifically to a miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source and its analysis method. Background Technology

[0002] Mass spectrometry is an extremely important analytical tool in modern scientific research and industrial testing. With its advantages of high sensitivity, high resolution and ability to provide rich information on compound structures, it plays an irreplaceable role in many disciplines and industries such as chemistry, biology, environmental science, and medical diagnostics. By converting sample molecules into ions and separating and detecting them based on the mass-to-charge ratio of the ions, mass spectrometers can accurately determine the types and contents of various compounds in a sample.

[0003] However, existing mass spectrometry technology has many problems and cannot meet the needs of practical applications. In terms of operation procedures, traditional mass spectrometers are complex and require extensive training for professionals to master. This not only increases the cost of use but also limits their application in some field tests that require high levels of operator expertise. The adjustment of analytical parameters also largely relies on manual operation, lacking intelligence and automation, resulting in low analytical efficiency and susceptibility to errors introduced by human factors. In traditional vacuum ultraviolet photoionization sources, there is a lack of real-time beam monitoring and adjustment mechanisms. In actual use, factors such as vibration and temperature changes can easily alter the focusing state of the vacuum ultraviolet beam, leading to a decrease in ionization efficiency and affecting the detection sensitivity and accuracy of the mass spectrometer. In addition, there is a technological gap in the integration of intelligent pre-screening and targeted analysis functions in miniaturized mass spectrometers. Existing miniaturized mass spectrometers often can only perform simple sample analysis and cannot automatically perform pre-screening and targeted analysis based on sample characteristics, making it difficult to meet the demand for efficient and accurate analysis in rapid field testing. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a miniaturized portable mass spectrometer and its analytical method based on a vacuum ultraviolet photoionization source. It enables gas-liquid sampling via a sample introduction and pre-screening module using a micro-pump, liquid sampler, and three-way valve. Sample characteristic data is collected using RGB optical detection, a gas sensor array, and a pH electrode. Data analysis identifies the target compound and generates parameter adjustment commands. The vacuum ultraviolet light source module adjusts the wavelength and intensity of the deuterium lamp according to the commands. After focusing by the optical focusing system, the sample is ionized in the ionization chamber. The beam control module monitors the beam state in real time and automatically adjusts the focus. The mass analysis module uses a reflective time-of-flight structure to separate ions based on their mass-to-charge ratio. The detection module converts the ion signal into an electrical signal through a microchannel plate detector, achieving efficient and accurate analysis of the sample.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: On one hand, a miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source, the mass spectrometer comprising: The sample introduction and pre-screening module consists of a sample introduction system and an intelligent sample pre-screening unit. The sample introduction system enables the switching of gas and liquid sample introduction. The pre-screening unit collects data through the physical and chemical property detection subunit, and outputs the target compound type and parameter adjustment instructions after processing by the data analysis subunit. Vacuum ultraviolet light source module: It consists of a tunable excitation unit, an optical focusing system and an ionization chamber. The tunable excitation unit adjusts the wavelength and intensity of the light source, the optical focusing system adjusts the focus through a mirror, and the ionization chamber provides the sample ionization space and optimizes ion extraction. The beam control module includes a beam monitoring unit and an adaptive adjustment unit. The monitoring unit detects the beam divergence and position, and the adaptive adjustment unit processes the signals, compares and calculates the deviation, and drives the piezoelectric ceramic micro-displacement platform to adjust the reflector of the optical focusing system, thereby realizing closed-loop control of beam focusing. The mass analysis module adopts a reflective time-of-flight structure, consisting of an ion acceleration zone, a field-free flight zone, and a reflection zone. The acceleration zone accelerates ions, the field-free flight zone separates ions, and the reflection zone refocuses ions. Each region achieves its corresponding function through specific structures and electric field settings. The detection module adopts a microchannel plate detector structure, consisting of an input window, a microchannel plate array, and an anode. The input window allows ions to pass through, the microchannel plate array amplifies the ion signal, and the anode converts the signal into an electrical signal, which is then amplified and transmitted to the data processing unit.

[0006] Furthermore, the sample introduction and pre-screening module consists of a sample introduction system and an intelligent sample pre-screening unit. The sample introduction system adopts a combination structure of a micro air pump and a micro liquid injector, connected by a three-way valve to form a switchable dual-channel sample introduction structure. The micro air pump adopts a diaphragm structure and is equipped with a flow regulating device. The micro liquid injector adopts an injection pump structure and is equipped with a high-precision stepper motor drive system. The intelligent sample pre-screening unit includes a physical property detection subunit, a chemical property detection subunit, and a data analysis subunit. The physical property detection subunit integrates an RGB three-color LED light source and a spectral sensor to form a reflective optical detection structure. It is also equipped with a metal oxide semiconductor gas sensor array. Each sensor is independently packaged and integrates a heating element. The chemical property detection subunit adopts a micro glass electrode structure with a pH-sensitive membrane on the electrode surface. It is equipped with a reference electrode and a signal amplification circuit. The data analysis subunit calculates the feature matching degree of the detection data using formulas, and quantitatively compares the multi-dimensional data of the physical property detection subunit and the chemical property detection subunit with the compound feature database to generate the target compound type discrimination result and the corresponding ionization source parameter adjustment scheme.

[0007] Furthermore, in the sample introduction and pre-screening module, the data analysis subunit calculates the feature matching degree of the detection data using a formula, which is: ,in, This indicates the degree of matching between sample detection data and characteristic data of a certain compound in the database, with a value range of [0, 1]. The closer the value is to 1, the higher the match between the sample and the compound. This represents the number of feature data dimensions involved in the matching calculation. It is the first Weight coefficients for each feature data dimension. For the sample at the The detection values ​​of each feature data dimension. Is a certain compound in the database in the first... Standard values ​​for each feature data dimension.

[0008] Furthermore, the vacuum ultraviolet light source module adopts a miniaturized integrated structure, consisting of a tunable excitation unit, an optical focusing system, and an ionization chamber. The tunable excitation unit includes a deuterium lamp light source, a filter group, and a light intensity adjustment device. The filter group adopts a rotary structure to achieve switching of different wavelength passbands. The optical focusing system consists of three non-collinearly arranged mirrors. The surface of the parabolic mirror is coated with a high-reflectivity metal film. The first mirror collimates the light emitted by the light source, the second mirror performs preliminary focusing, and the third mirror completes the final focusing. All three mirrors are connected to the piezoelectric ceramic driving element through flexible hinges. During the configuration of the light source parameters, the adjusted vacuum ultraviolet light intensity is calculated by formula according to the adjustment scheme generated by the sample introduction and pre-screening module. The ionization chamber is a cylindrical stainless steel cavity with a sample introduction capillary inside. Ion extraction slits are set at both ends of the ionization chamber. The slit width can be adjusted by a fine-tuning mechanism. The inner wall is coated with a low surface energy material.

[0009] Furthermore, the vacuum ultraviolet light source module calculates the adjusted vacuum ultraviolet light intensity according to the adjustment scheme generated by the sample introduction and pre-screening module, using the following formula: ,in, This is the adjusted vacuum ultraviolet light intensity. This is the base intensity value of the light source, the default intensity setting of the light source before any parameter adjustments are made. It is the intensity adjustment coefficient, a constant preset according to the ionization characteristics of different target compounds, used to control the amplitude of light intensity modulation. It is an estimate of the target compound concentration determined by the sample injection and pre-screening module. It is the maximum detectable concentration of this type of compound recorded in the database.

[0010] Furthermore, the beam control module includes a beam monitoring unit and an adaptive adjustment unit. The divergence detection device of the beam monitoring unit adopts a double-slit diffraction structure with a fixed distance between the front and rear slits. A linear CCD detector is installed at a specific distance to capture the diffraction spot. The four photodiodes of the four-quadrant photodetector are arranged in a square. A small aperture at the front end is used to limit the range of the beam entering the system. The signal processing subunit of the adaptive adjustment unit preprocesses the signal output by the beam monitoring unit. The comparison subunit compares the processed data with a preset reference value to calculate the adjustment amount of the reflector. The driving subunit uses pulse width modulation technology to generate a driving signal based on the deviation to control the extension and retraction of the piezoelectric ceramic micro-displacement platform. This platform is connected to the reflector of the optical focusing system through a rigid connector, enabling precise adjustment of six degrees of freedom.

[0011] Furthermore, in the beam control module, the comparison subunit compares the processed data with a preset reference value to calculate the mirror adjustment amount, the calculation formula of which is: Calculate the adjustment amount of the reflector, where To adjust the displacement, As a comprehensive regulatory factor, and These are the current detected divergence and location coordinates, respectively. and For ideal reference.

[0012] Furthermore, the quality analysis module adopts a reflective time-of-flight structure, consisting of an ion acceleration zone, a field-free flight zone, and a reflection zone. The parallel plate electrodes in the ion acceleration zone are made of high-purity aluminum plates with anodized surfaces. The electrode spacing is fixed by high-precision positioning posts. High-voltage power supply modules are connected to both ends of the electrodes to generate a stable DC electric field. An ion optical lens group is installed at the entrance of the acceleration zone to focus and guide the ion beam. The field-free flight zone uses carbon fiber guide rails with embedded metal wires for grounding. The guide rail surface is polished. Ion collimators are installed at both ends of the flight zone to control the ion beam divergence angle. The reflection electrode group in the reflection zone consists of multiple concentric ring electrodes separated by insulating gaskets. Each electrode is connected to an independent high-voltage power supply. By applying different voltages, a nonlinear electric field distribution is formed, achieving secondary focusing of ions. An ion receiving slit is set at the exit of the reflection zone to screen ions with specific flight times.

[0013] Furthermore, the detection module adopts a microchannel plate detector structure, consisting of an input window, a microchannel plate array, and an anode. The input window is made of borosilicate glass with an aluminum film deposited on its surface as an ion incident window. The microchannel plate array is a dual MCP cascade structure with a channel diameter of 10-20 μm, a channel spacing of 12-24 μm, and a tilt angle of 8-15°. The anode adopts a segmented structure, consisting of multiple independent anode strips, each equipped with an independent charge-sensitive amplifier.

[0014] On the other hand, an analytical method based on a miniaturized portable mass spectrometer using a vacuum ultraviolet photoionization source, the method comprising: Sample introduction and pre-screening: The sample is introduced into the pre-screening unit through the sample introduction system. The physical property detection subunit completes the acquisition of color spectrum data and analysis of volatile components. The chemical property detection subunit completes the pH value measurement. The data analysis subunit compares the detection data with the pre-stored compound characteristic database to generate the target compound type identification result and the ionization source parameter adjustment scheme. Light source parameter configuration: Adjust the excitation unit parameters of the vacuum ultraviolet light source module and the initial position of the optical focusing system according to the pre-screening results; Beam focusing adjustment: The beam monitoring unit collects vacuum ultraviolet beam parameters in real time, and the adaptive adjustment unit calculates the adjustment amount of the optical element based on the control algorithm, drives the actuator to adjust the position of the reflector of the optical focusing system, and realizes closed-loop control of the beam focusing state; Sample ionization: The sample enters the ionization chamber and undergoes a photoionization reaction with optimized focused vacuum ultraviolet light; Mass Analysis and Detection: Ions enter the time-of-flight mass analyzer. The accelerating voltage is automatically adjusted according to the mass-to-charge ratio of the target compound. After flying in the field-free flight region, the ions are refocused in the reflection region and reach the detector. The microchannel plate detector converts the ion signal into an electrical signal, which is then amplified and digitized by the analog-to-digital converter. The data processing unit processes the collected signal to generate a mass spectrum and complete the qualitative analysis of the compound.

[0015] Compared with existing technologies, this miniaturized portable mass spectrometer and its analytical method based on a vacuum ultraviolet photoionization source have the following advantages: 1. This invention utilizes an intelligent sample pre-screening unit in the sample introduction and pre-screening module, along with physical and chemical property detection subunits, to rapidly acquire physicochemical property data such as color spectrum, volatile components, and pH value of samples. The compound type identification model built into the data analysis subunit can automatically compare with the sample property database, quickly identify the target compound type, and generate ionization source parameter adjustment instructions, greatly simplifying the operation process, reducing detection time, and enabling the mass spectrometer to quickly adapt to the detection needs of different samples.

[0016] 2. This invention integrates a beam divergence detection device and a position sensor in the beam monitoring unit of the beam control module, enabling real-time acquisition of vacuum ultraviolet beam parameters. The adaptive adjustment unit calculates the adjustment amount of optical elements based on the control algorithm, drives the actuator to adjust the position of the reflector of the optical focusing system, and realizes closed-loop control of the beam focusing state. This maintains the focusing state of the vacuum ultraviolet beam in real time, effectively overcoming the problem that traditional vacuum ultraviolet photoionization sources are easily affected by vibration and temperature changes, leading to a decrease in ionization efficiency. This ensures that the sample can undergo a highly efficient photoionization reaction with the stably focused vacuum ultraviolet light in the ionization chamber, thereby guaranteeing the stability and accuracy of mass spectrometry detection. Attached Figure Description

[0017] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings; Figure 1 This is a schematic diagram of the overall structure of a miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source; Figure 2 This is a schematic diagram of the overall process of a miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source. Figure 3 This is a schematic diagram of the sample introduction and pre-screening module of a miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source; Figure 4 This is a schematic diagram of the structure of a miniaturized portable mass spectrometer vacuum ultraviolet light source module based on a vacuum ultraviolet photoionization source; Figure 5 This is a schematic diagram of the beam control module of a miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source. Figure 6 This is a schematic diagram of the structure of a miniaturized portable mass spectrometer mass analysis module based on a vacuum ultraviolet photoionization source; Figure 7 This is a schematic diagram of the detection module of a miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source.

[0018] Figure label: 1. Reflection zone; 2. Field-free flight zone; 3. Detection module; 4. Ion acceleration zone; 5. Linear CCD detector; 6. Photodetector; 7. Double-slit diffraction device; 8. Optical focusing system; 9. Filter group; 10. Intelligent sample pre-screening unit; 11. Miniature liquid injector; 12. Three-way valve; 13. Miniature air pump; 14. Vacuum pump; 15. Deuterium lamp light source. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 like Figure 1 As shown, this miniaturized portable mass spectrometer consists of a sample introduction and pre-screening module, a vacuum ultraviolet light source module, a beam control module, a mass analysis module, and a detection module 3 connected in sequence. The output end of the sample introduction and pre-screening module is connected to the sample introduction capillary of the vacuum ultraviolet light source module through a sealed sample transmission pipeline, ensuring that the sample can smoothly enter the ionization region from the pre-screening stage. The ion extraction slit of the vacuum ultraviolet light source module is precisely aligned with the inlet of the ion acceleration zone 4 of the mass analysis module, ensuring that the ions generated by ionization can efficiently enter the mass analysis stage. The ion receiving slit of the mass analysis module is connected to the input window of the detection module 3, so that the ions after mass analysis can be accurately captured by the detection module 3. The modules are physically connected through specific interfaces and transmission paths, and signal interaction and collaborative operation are achieved through data transmission lines and control lines.

[0021] The miniature oil-free diaphragm gas pump and plunger-type syringe pump in the sample introduction system achieve flexible switching between gas and liquid sample introduction channels via a three-way switching valve. When gaseous samples need to be analyzed, the electromagnetically driven three-way switching valve opens the gas path, and the miniature gas pump 13 delivers the gaseous sample to the intelligent sample pre-screening unit 10 at a stable flow rate through the polytetrafluoroethylene (PTFE) injection line. For liquid samples, the three-way switching valve switches to the liquid path, and the miniature liquid injector 11 injects the liquid sample with a precise injection volume using a high-precision ceramic plunger rod and seals. In the physical characteristic detection subunit of the intelligent sample pre-screening unit 10, the LED light source array of the RGB optical detection structure emits light covering 380-780°. Light in the 0nm spectral range shines on the sample surface, and the reflected light is received by a high-resolution linear CCD image sensor, thereby acquiring the sample's reflectance spectrum data. Each sensitive element of the metal oxide semiconductor gas sensor array, under the action of an independent heating control circuit, responds to various volatile substances and detects volatile components in the sample. The micro glass electrode of the chemical property detection subunit reacts with ions in the sample through the nanoscale ion exchange layer in its composite membrane structure. Combined with a solid Ag / AgCl reference electrode, and through a signal amplification circuit integrating a low-noise operational amplifier and a programmable gain control unit, the sample's pH value can be measured quickly and accurately.

[0022] like Figure 3As shown, the data analysis subunit converts the analog signals output by the physical and chemical property detection subunit into digital signals via a high-speed ADC. Then, it performs a rapid search and matching with the compound feature database with a built-in hierarchical storage structure to determine the types of target compounds that may be present in the sample. Based on the analytical requirements of the corresponding compounds in the database, it generates parameter adjustment instructions for the vacuum ultraviolet light source module and the mass analysis module.

[0023] The deuterium lamp of the tunable excitation unit in the vacuum ultraviolet light source module is encapsulated in a vacuum quartz sleeve. With the help of a heat dissipation device, it maintains a stable operating temperature and continuously generates vacuum ultraviolet light. A stepper motor drives the rotary filter group 9, which quickly switches to a bandpass filter of appropriate wavelength according to instructions generated by the sample introduction and pre-screening module, achieving precise adjustment of the light source wavelength. The liquid crystal electronically controlled variable attenuator flexibly adjusts the transmittance of the vacuum ultraviolet light by changing the applied voltage, thereby controlling the light intensity. The three parabolic mirrors of the optical focusing system 8 are coated with a high-reflectivity metal film layer. The first mirror... The light emitted by the deuterium lamp is collimated and propagated in parallel. The second mirror performs initial focusing on the parallel light rays, and the third mirror completes the final focusing, accurately focusing the light rays into the ionization chamber. The three mirrors are connected to the piezoelectric ceramic driving element through flexible hinges, which can achieve precise adjustment of minute angles and positions to ensure the best beam focusing effect. The ionization chamber is the core place for sample ionization. The cylindrical stainless steel cavity is equipped with a treated sample introduction capillary. The width of the ion extraction slits at both ends can be adjusted by a fine-tuning mechanism. The inner wall is coated with a low surface energy material to effectively reduce ion adsorption.

[0024] In the double-slit diffraction structure of the beam monitoring unit in the beam control module, the fixed-distance slits cause diffraction of the vacuum ultraviolet beam. A linear CCD detector 5, installed at a specific distance, captures the diffracted spot. The beam divergence is calculated by analyzing the spot. The four photodiodes of the four-quadrant photodetector 6 are arranged in a square. A small aperture at the front limits the beam's entry range, detecting only the beam position in the central region. Based on the differences in the electrical signals of the four photodiodes, the beam focal point is precisely determined. Figure 5 As shown, the signal processing subunit of the adaptive adjustment unit preprocesses the signal output by the beam monitoring unit, the comparison subunit compares the processed data with the preset reference value and calculates the adjustment amount, and the driving subunit uses pulse width modulation technology to control the extension and retraction of the piezoelectric ceramic micro-displacement platform according to the generated corresponding driving signal. The piezoelectric ceramic micro-displacement platform is connected to the reflector of the optical focusing system 8 through a rigid connector, which can realize precise adjustment of six degrees of freedom, thereby quickly correcting the beam focusing state.

[0025] The parallel plate electrodes in ion acceleration zone 4 of the mass analysis module are made of high-purity aluminum plates with anodized surfaces. High-precision positioning posts fix the electrode spacing. High-voltage power supply modules connected at both ends generate a stable and adjustable DC electric field. An ion optical lens assembly is installed at the entrance of the acceleration zone to focus and guide the incoming ion beam, ensuring the ions enter the accelerating electric field in a favorable shape. Under the influence of the electric field, the ions gain kinetic energy and accelerate. The carbon fiber guide rail in the fieldless flight zone 2 has high strength and low weight characteristics. Internally embedded metal wires are grounded to prevent static electricity accumulation from interfering with ion flight. The guide rail surface is polished to reduce ion flight drag. Ion collimators installed at both ends of the flight zone control the ion beam divergence angle, ensuring that ions fly along a predetermined path in the fieldless flight zone 2. Ions with different mass-to-charge ratios achieve time separation due to differences in flight speed over the same flight distance. The reflective electrode assembly in the reflection zone 1 consists of multiple concentric ring electrodes separated by insulating gaskets. Each electrode is connected to an independent high-voltage power supply. By applying different voltages, a nonlinear electric field distribution is formed, such as... Figure 1 As shown, the ions entering the reflection zone 1 are refocused, change their flight direction, and re-enter the field-free flight zone 2, eventually arriving at the detection module 3 in a specific order, thus achieving efficient separation of ions with different mass-to-charge ratios.

[0026] The input window of detection module 3 is a circular borosilicate glass plate with a nano-scale ultrathin aluminum film vapor-deposited on its surface. The microchannel plate array adopts a frustum-shaped microchannel structure with a secondary electron emission material coated on the inner wall. When two MCPs are cascaded, the two microchannel plates are stacked at a certain angle, which significantly improves the gain and resolution. When ions collide with the inner wall of the microchannel plate, a secondary electron avalanche is generated, and the electronic signal is amplified. The anode adopts a segmented printed circuit board structure, with insulating material filling the spaces between the anode bars. Each anode bar is connected to an independent charge-sensitive amplifier. The amplifier uses a low-noise field-effect transistor as the input stage, and an integrating capacitor is used to achieve charge-to-voltage conversion. The amplified electrical signal is transmitted to the subsequent data processing unit via a coaxial cable, such as... Figure 7 As shown, this provides accurate signal data for the qualitative analysis of compounds.

[0027] Example 2 The sample to be analyzed is placed in the injection system. According to the physical state of the sample, the control device sends a command to the three-way switching valve. If the sample is gaseous, the three-way switching valve opens the gas path under electromagnetic drive, and the miniature oil-free diaphragm gas pump starts. The gaseous sample is delivered to the intelligent sample pre-screening unit 10 through the polytetrafluoroethylene injection pipeline at a stable flow rate. If the sample is liquid, the three-way switching valve switches to the liquid path, and the miniature liquid injector 11 injects the liquid sample into the injection pipeline at the set precise flow rate and delivers it to the intelligent sample pre-screening unit 10.

[0028] After the intelligent sample pre-screening unit 10 is activated, the physical property detection subunit and the chemical property detection subunit work synchronously. In the physical property detection subunit, the LED light source array of the RGB optical detection structure emits light to illuminate the sample. The high-resolution linear CCD image sensor acquires the sample reflectance spectrum data in a very short time. Under the action of the heating control circuit, each sensitive element of the metal oxide semiconductor gas sensor array quickly responds to the volatile components of the sample. The micro glass electrode of the chemical property detection subunit is immersed in the sample, and its composite film structure reacts with the ions in the sample. Combined with the reference electrode, the pH value of the sample is quickly and accurately measured through the signal amplification circuit. The analog signals output by each detection module 3 are transmitted to the data analysis subunit and analyzed using the formula. Calculate the matching degree between sample detection data and compound characteristic data in the database, where, The matching degree is represented by a value in the range [0, 1]. The closer the value is to 1, the higher the matching degree. The number of feature data dimensions involved in the matching calculation covers multiple dimensions of physical and chemical property detection. It is the first The weight coefficients for each feature data dimension are set according to the importance of each feature in compound identification. For the sample at the The detection values ​​of each feature data dimension. Is a certain compound in the database in the first... The standard values ​​of each feature data dimension are calculated using this formula to ultimately determine the types of target compounds that may be present in the sample. Based on the analytical requirements of the corresponding compounds in the database, detailed parameter adjustment instructions are generated for the vacuum ultraviolet light source module and the mass analysis module, providing precise parameter guidance for subsequent analysis steps.

[0029] After receiving parameter adjustment commands generated during the sample introduction and pre-screening steps, the vacuum ultraviolet light source module first controls the stepper motor to drive the filter group 9 turntable according to the commands, quickly and accurately switching to the bandpass filter corresponding to the wavelength of the ionization of the active target compound, thus completing the adjustment of the light source wavelength. Simultaneously, the light intensity adjustment device, according to the commands, adjusts the light intensity using the formula... Precisely adjust the intensity of vacuum ultraviolet light, among which, The adjusted vacuum ultraviolet light intensity, This is the base intensity value of the light source, which is the preset default intensity. The intensity adjustment coefficient was determined through numerous experiments based on the ionization characteristics of different target compounds. This is an estimate of the target compound concentration determined by the injection and pre-screening modules. The formula is based on the relationship between compound concentration and required ionization light intensity, and is the maximum detectable concentration value of this type of compound recorded in the database. It enables adaptive adjustment of light intensity to ensure that appropriate energy is provided for sample ionization. During the adjustment of light intensity and wavelength, the piezoelectric ceramic driving element of the optical focusing system 8 maintains its initial position to ensure that the beam focusing state is not affected in the initial stage of parameter adjustment. The ionization chamber is evacuated through the connected vacuum pump 14 pipeline. As the vacuum pump 14 continues to work, the internal pressure of the ionization chamber gradually decreases until the set working vacuum level is reached, creating a stable vacuum environment for sample ionization. This completes the comprehensive parameter configuration of the light source module.

[0030] The beam monitoring unit continuously collects divergence and position data of the vacuum ultraviolet beam. The double-slit diffraction structure monitors the beam divergence in real time. The linear CCD detector 5 quickly captures the diffraction spot and performs analysis and calculation. The four-quadrant photodetector 6 continuously detects the position of the beam center region and transmits the collected data to the adaptive adjustment unit in real time. The adaptive adjustment unit preprocesses the collected data, and the comparison subunit compares the processed data with a pre-set standard value, i.e., the ideal beam divergence value. and the coordinates of the ideal beam focal position A detailed comparison was made using formulas. Calculate the adjustment amount of the reflector, where, This refers to the amount of displacement or angle that the reflector needs to be adjusted. As a comprehensive regulatory factor, This represents the currently detected beam divergence value. These are the coordinates of the currently detected beam focal point. To adjust the direction coefficient, when the current detected value is greater than the ideal value, When the current detected value is less than the ideal value, The drive subunit generates a corresponding drive signal using pulse width modulation technology based on the calculated adjustment amount, and precisely controls the extension and retraction of the piezoelectric ceramic micro-displacement platform. The piezoelectric ceramic micro-displacement platform drives the reflector of the optical focusing system 8 to adjust its position and angle through a rigid connector. The adjusted beam parameters are then detected in real time by the beam monitoring unit, forming a tight closed-loop feedback adjustment.

[0031] After configuring the light source parameters and adjusting the beam focus, the sample smoothly enters the ionization region through the sample guide capillary in the ionization chamber. At this point, under optimized focusing and appropriately intense vacuum ultraviolet light irradiation, the sample molecules absorb photon energy, undergo photoionization, and generate positive ions and electrons. The pre-set electric field in the ionization chamber accelerates the generated ions and guides them to the ion extraction slit, while the electrons are absorbed by the grounding electrode to prevent them from interfering with subsequent analysis. Under the influence of the electric field, the ion beam passes through the ion extraction slit with good shape and speed, smoothly entering the mass analysis module, preparing for subsequent ion separation and detection.

[0032] After entering the ion acceleration zone 4 of the mass analysis module, the ions gain kinetic energy and accelerate under the stable and adjustable DC electric field generated by the parallel plate electrodes. The ion optical lens group further focuses and guides the ion beam, allowing the ions to enter the field-free flight zone 2 in an ideal state. In the field-free flight zone 2, because ions with different mass-to-charge ratios require different flight times for the same flight distance, ions are separated according to their mass-to-charge ratio. The special design of the carbon fiber guide rail and the function of the ion collimator ensure that the ions maintain a good trajectory and state during flight. The separated ions enter the reflection zone 1, where they are refocused under the nonlinear electric field distribution formed by the reflection electrode group. After changing their flight direction, they re-enter the field-free flight zone 2 and are finally separated in a specific order. The ion beam arrives at the detection module 3 at precise time intervals. The input window of the detection module 3 receives the ion beam, and the ions collide with the inner wall of the microchannel plate, triggering a secondary electron avalanche. The electronic signal is greatly amplified in the dual MCP cascade structure. The amplified electronic signal reaches the anode, and the segmented anode structure converts the electronic signal into an electrical signal. The charge-sensitive amplifiers connected to each anode bar further amplify the electrical signal. The amplified signal is transmitted to the data processing system through a coaxial cable. The data processing system performs a series of complex operations such as digital processing, baseline correction, and peak identification on the signal, and finally generates a detailed and accurate mass spectrum. Based on the mass spectrum and related algorithms, qualitative analysis of the compound is performed to obtain specific information about the target compound in the sample, thus completing the entire analysis process.

[0033] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source, characterized in that, This mass spectrometer: The sample introduction and pre-screening module consists of a sample introduction system and an intelligent sample pre-screening unit. The sample introduction system enables the switching of gas and liquid sample introduction. The pre-screening unit collects data through the physical and chemical property detection subunit, and outputs the target compound type and parameter adjustment instructions after processing by the data analysis subunit. Vacuum ultraviolet light source module: It consists of a tunable excitation unit, an optical focusing system and an ionization chamber. The tunable excitation unit adjusts the wavelength and intensity of the light source, the optical focusing system adjusts the focus through a mirror, and the ionization chamber provides the sample ionization space and optimizes ion extraction. The beam control module includes a beam monitoring unit and an adaptive adjustment unit. The monitoring unit detects the beam divergence and position, and the adaptive adjustment unit processes the signals, compares and calculates the deviation, and drives the piezoelectric ceramic micro-displacement platform to adjust the reflector of the optical focusing system, thereby realizing closed-loop control of beam focusing. The mass analysis module adopts a reflective time-of-flight structure, consisting of an ion acceleration zone, a field-free flight zone, and a reflection zone. The acceleration zone accelerates ions, the field-free flight zone separates ions, and the reflection zone refocuses ions. Each region achieves its corresponding function through specific structures and electric field settings. The detection module adopts a microchannel plate detector structure, consisting of an input window, a microchannel plate array, and an anode. The input window allows ions to pass through, the microchannel plate array amplifies the ion signal, and the anode converts the signal into an electrical signal, which is then amplified and transmitted to the data processing unit.

2. The miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source according to claim 1, characterized in that, The sample introduction and pre-screening module consists of a sample introduction system and an intelligent sample pre-screening unit. The sample introduction system adopts a combination structure of a micro air pump and a micro liquid injector, connected by a three-way valve to form a switchable dual-channel sample introduction structure. The micro air pump adopts a diaphragm structure and is equipped with a flow regulating device. The micro liquid injector adopts an injection pump structure and is equipped with a high-precision stepper motor drive system. The intelligent sample pre-screening unit includes a physical property detection subunit, a chemical property detection subunit, and a data analysis subunit. The physical property detection subunit integrates an RGB three-color LED light source and a spectral sensor to form a reflective optical detection structure. It is also equipped with a metal oxide semiconductor gas sensor array. Each sensor is independently packaged and integrates a heating element. The chemical property detection subunit adopts a micro glass electrode structure with a pH-sensitive membrane on the electrode surface. It is equipped with a reference electrode and a signal amplification circuit. The data analysis subunit calculates the feature matching degree of the detection data using formulas, and quantitatively compares the multi-dimensional data of the physical property detection subunit and the chemical property detection subunit with the compound feature database to generate the target compound type discrimination result and the corresponding ionization source parameter adjustment scheme.

3. The miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source according to claim 2, characterized in that, In the sample injection and pre-screening module, the data analysis subunit calculates the feature matching degree of the detection data using a formula, which is: ,in, This indicates the degree of matching between sample detection data and characteristic data of a certain compound in the database, with a value range of [0, 1]. The closer the value is to 1, the higher the match between the sample and the compound. This represents the number of feature data dimensions involved in the matching calculation. It is the first Weight coefficients for each feature data dimension. For the sample at the The detection values ​​of each feature data dimension. Is a certain compound in the database in the first... Standard values ​​for each feature data dimension.

4. The miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source according to claim 1, characterized in that, The vacuum ultraviolet light source module adopts a miniaturized integrated structure, consisting of a tunable excitation unit, an optical focusing system, and an ionization chamber. The tunable excitation unit includes a deuterium lamp light source, a filter group, and a light intensity adjustment device. The filter group adopts a rotating structure to achieve switching of different wavelength passbands. The optical focusing system consists of three non-collinearly arranged mirrors. The surface of the parabolic mirror is coated with a high-reflectivity metal film. The first mirror collimates the light emitted by the light source, the second mirror performs preliminary focusing, and the third mirror completes the final focusing. All three mirrors are connected to piezoelectric ceramic driving elements through flexible hinges. During the configuration of light source parameters, the adjusted vacuum ultraviolet light intensity is calculated by formula according to the adjustment scheme generated by the sample introduction and pre-screening module. The ionization chamber is a cylindrical stainless steel cavity with a sample introduction capillary inside. Ion extraction slits are set at both ends of the ionization chamber. The slit width can be adjusted by a fine-tuning mechanism. The inner wall is coated with a low surface energy material.

5. The miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source according to claim 4, characterized in that, The vacuum ultraviolet light source module calculates the adjusted vacuum ultraviolet light intensity according to the adjustment scheme generated by the sample introduction and pre-screening module, using the following formula: ,in, This is the adjusted vacuum ultraviolet light intensity. This is the base intensity value of the light source, the default intensity setting of the light source before any parameter adjustments are made. It is the intensity adjustment coefficient, a constant preset according to the ionization characteristics of different target compounds, used to control the amplitude of light intensity modulation. It is an estimate of the target compound concentration determined by the sample injection and pre-screening module. It is the maximum detectable concentration of this type of compound recorded in the database.

6. The miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source according to claim 1, characterized in that, The beam control module includes a beam monitoring unit and an adaptive adjustment unit. The divergence detection device of the beam monitoring unit adopts a double-slit diffraction structure with a fixed distance between the front and rear slits. A linear CCD detector is installed at a specific distance to capture the diffraction spot. The four photodiodes of the four-quadrant photodetector are arranged in a square. A small aperture at the front end is used to limit the range of the beam entering the system. The signal processing subunit of the adaptive adjustment unit preprocesses the signal output by the beam monitoring unit. The comparison subunit compares the processed data with a preset reference value to calculate the adjustment amount of the reflector. The drive subunit uses pulse width modulation technology to generate a drive signal based on the deviation to control the extension and retraction of the piezoelectric ceramic micro-displacement platform. This platform is connected to the reflector of the optical focusing system through a rigid connector, enabling precise adjustment of six degrees of freedom.

7. The miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source according to claim 6, characterized in that, In the beam control module, the comparison subunit compares the processed data with a preset reference value to calculate the mirror adjustment amount. The calculation formula is as follows: Calculate the adjustment amount of the reflector, where To adjust the displacement, As a comprehensive regulatory factor, and These are the current detected divergence and location coordinates, respectively. and For ideal reference.

8. The miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source according to claim 1, characterized in that, The quality analysis module adopts a reflective time-of-flight structure, consisting of an ion acceleration zone, a field-free flight zone, and a reflection zone. The parallel plate electrodes in the ion acceleration zone are made of high-purity aluminum plates with anodized surfaces. The electrode spacing is fixed by high-precision positioning posts. High-voltage power supply modules are connected to both ends of the electrodes to generate a stable DC electric field. An ion optical lens group is installed at the entrance of the acceleration zone to focus and guide the ion beam. The field-free flight zone uses carbon fiber guide rails with embedded metal wires for grounding. The guide rail surface is polished. Ion collimators are installed at both ends of the flight zone to control the ion beam divergence angle. The reflection electrode group in the reflection zone consists of multiple concentric ring electrodes separated by insulating gaskets. Each electrode is connected to an independent high-voltage power supply. By applying different voltages, a nonlinear electric field distribution is formed, achieving secondary focusing of ions. An ion receiving slit is set at the exit of the reflection zone to screen ions with specific flight times.

9. The miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source according to claim 1, characterized in that, The detection module adopts a microchannel plate detector structure, consisting of an input window, a microchannel plate array, and an anode. The input window is made of borosilicate glass with an aluminum film deposited on its surface as an ion incident window. The microchannel plate array is a dual MCP cascade structure with a channel diameter of 10-20 μm, a channel spacing of 12-24 μm, and a tilt angle of 8-15°. The anode adopts a segmented structure, consisting of multiple independent anode strips, each equipped with an independent charge-sensitive amplifier.

10. An analytical method for a miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source, the method being applicable to the miniaturized portable mass spectrometer based on a vacuum ultraviolet photoionization source as described in any one of claims 1-9, characterized in that, The method includes: Sample introduction and pre-screening: The sample is introduced into the pre-screening unit through the sample introduction system. The physical property detection subunit completes the acquisition of color spectrum data and analysis of volatile components. The chemical property detection subunit completes the pH value measurement. The data analysis subunit compares the detection data with the pre-stored compound characteristic database to generate the target compound type identification result and the ionization source parameter adjustment scheme. Light source parameter configuration: Adjust the excitation unit parameters of the vacuum ultraviolet light source module and the initial position of the optical focusing system according to the pre-screening results; Beam focusing adjustment: The beam monitoring unit collects vacuum ultraviolet beam parameters in real time, and the adaptive adjustment unit calculates the adjustment amount of the optical element based on the control algorithm, drives the actuator to adjust the position of the reflector of the optical focusing system, and realizes closed-loop control of the beam focusing state; Sample ionization: The sample enters the ionization chamber and undergoes a photoionization reaction with optimized focused vacuum ultraviolet light; Mass Analysis and Detection: Ions enter the time-of-flight mass analyzer. The accelerating voltage is automatically adjusted according to the mass-to-charge ratio of the target compound. After flying in the field-free flight region, the ions are refocused in the reflection region and reach the detector. The microchannel plate detector converts the ion signal into an electrical signal, which is then amplified and digitized by the analog-to-digital converter. The data processing unit processes the collected signal to generate a mass spectrum and complete the qualitative analysis of the compound.

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