Method for detecting glyoxal by cluster-mediated chemical ionization

Abstract

The application discloses an experimental device and method for realizing efficient detection of glyoxal through cluster-mediated chemical ionization. + , CH2Br2 + The reagent ion is transmitted to a molecular ion reaction zone through an isolation electrode; when glyoxal and high-concentration alcohol are jointly injected into the ion molecular reaction zone, a cluster-mediated signal enhancement effect is found for the first time in the ionization process of glyoxal, a protonated glyoxal-alcohol molecular ion is generated, and then enters a time-of-flight mass analyzer for analysis and detection. The analysis method does not need complex sample pretreatment, and a spectrum can be obtained in 30s, so that rapid and high-sensitivity detection of glyoxal is realized.

Description

Technical Field

[0001] This invention relates to quality analysis instruments, specifically to an experimental apparatus and method for the efficient detection of glyoxal via cluster-mediated chemical ionization. Background Technology

[0002] Glyoxal, the simplest α-dicarbonyl compound in molecular structure, is widely used as a cross-linking agent in the paper and textile industries due to its ability to effectively improve the tensile strength and water resistance of paper. However, glyoxal is genotoxic; it can disrupt the integrity of DNA structure by cross-linking or reacting with DNA. Excessive intake or absorption of glyoxal can also lead to protein modification and the formation of advanced glycation end products (AGEs), which are associated with the pathologies of diabetes and age-related diseases. Therefore, achieving highly sensitive detection of glyoxal has attracted widespread attention.

[0003] Commonly used analytical methods for glyoxal include high-performance liquid chromatography (HPLC), ultraviolet spectrophotometry (UV spectrophotometry), and gas chromatography-mass spectrometry (GC-MS). HPLC detection of glyoxal requires derivatization with 2,4-dinitrophenylhydrazine (DNPH). However, DNPH is reactive with other carbonyl compounds, thus interfering with the quantification of glyoxal. UV spectrophotometry has a high detection limit but weak qualitative ability. While GC-MS offers accurate qualitative analysis and a low detection limit, its analytical procedures are cumbersome and time-consuming.

[0004] In recent years, soft ionization mass spectrometry techniques, such as CI-MS and PI-MS, have become an important and universal detection technique for online analysis of trace small-molecule volatile organic compounds due to their advantages such as fast analysis speed, high molecular ion yield, and easy spectrum interpretation. However, among existing soft ionization techniques, the direct and rapid analysis of glyoxal remains a significant challenge due to its low direct ionization efficiency.

[0005] Therefore, this invention develops a cluster-mediated chemical ionization method for the efficient detection of glyoxal. First, the reagent gas enters the reagent ion generation region, where it is directly photoionized to produce reagent ions S. + reagent ion S + After being transmitted to the ion molecular reaction region via the isolation electrode, when glyoxal and a high concentration of alcohol are co-injected, a cluster-mediated signal enhancement effect is discovered for the first time during the ionization of glyoxal, generating a protonated molecular ion of glyoxal-alcohol, thus achieving efficient analysis and detection of glyoxal. Summary of the Invention

[0006] The purpose of this invention is to provide a highly efficient method for the detection of glyoxal based on time-of-flight mass spectrometry. This method involves using a carrier gas to carry dibromomethane reagent molecules into the reagent ion generation region, where they are directly photoionized to generate reagent ions CH2Br2. +CH2Br2 + Reagent ions are transported to the molecular ion reaction region via an isolating electrode. When glyoxal and a high concentration of alcohol are co-injected into the molecular ion reaction region, a cluster-mediated signal enhancement effect is observed for the first time during the ionization of glyoxal, generating protonated molecular ions of glyoxal-alcohol clusters. These protonated ions are then analyzed and detected by a time-of-flight mass analyzer. This analytical method requires no complex sample pretreatment and can obtain a spectrum in just 30 seconds, thus achieving rapid and highly sensitive detection of glyoxal.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for detecting glyoxal via cluster-mediated chemical ionization, employing an apparatus comprising an online dynamic gas mixing system and an ionization source.

[0009] The online dynamic gas mixing system includes a dilution gas source, a mass flow controller, a stainless steel gas mixing chamber, a micro-injection pump, a carrier gas pipeline, and an electric heating device on the outer wall of the stainless steel gas mixing chamber. The carrier gas inlet of the stainless steel gas mixing chamber is connected to the dilution gas source through the carrier gas pipeline, and the outlet of the stainless steel gas mixing chamber is connected to the reaction gas inlet pipe or sample gas inlet pipe of the ionization source. The reaction gas or sample gas is introduced into the ionization region of the ionization source through a three-way valve, and the third port of the three-way valve is connected to the atmosphere.

[0010] One or more of the following electric heating elements, electric heating belts, or electric heating wires are wound around the outer wall of the carrier gas pipeline, the outer wall of the stainless steel gas mixing chamber, the outer wall of the tee, and the reaction gas inlet pipe and the sample gas inlet pipe to maintain constant temperature heating, and can work under the conditions of room temperature to 300 ℃.

[0011] The working principle of the online dynamic gas mixing system is as follows: First, prepare the analyte solution or pure reagent of the required concentration. Then, use a micro-injection pump to inject the pre-prepared solution into the heated gas mixing chamber at a constant flow rate. At the same time, use a mass flow controller to introduce a carrier gas of constant flow rate into the gas mixing chamber. By precisely controlling the flow rates of the prepared solution and the carrier gas, the required concentration of reagent and analytical gas can be obtained at the outlet of the gas mixing chamber.

[0012] The ionization source includes an ultraviolet light source, a reaction gas inlet tube, a sample gas inlet tube, and an ionization source cavity. The ionization source cavity is characterized in that: the ionization source cavity is a hollow, sealed chamber with a through hole at the top of the ionization source cavity. The light window of the ultraviolet light source extends into the ionization source cavity through the through hole, and the ultraviolet light source is sealed to the through hole.

[0013] Inside the ionization source cavity, along the emission direction of the ultraviolet beam emitted by the ultraviolet light source, an ion repulsion electrode, an ion transport electrode, an isolation electrode, an ion focusing electrode, and an ionization source outlet electrode are arranged sequentially. All of these electrodes are annular structures with through holes in the middle, and they are spaced apart and placed parallel to each other by annular insulating gaskets with through holes in the middle. The through holes of the electrodes and the insulating gaskets are coaxial. The insulating gaskets are sealed to the adjacent electrode plates.

[0014] The isolation electrode and the ion focusing electrode divide the ionization region between the ion repulsion electrode and the ionization source outlet electrode into three chambers from top to bottom: the reagent ion generation region between the repulsion electrode and the isolation electrode, the ion molecular reaction region between the isolation electrode and the ion focusing electrode, and the ion focusing region between the ion focusing electrode and the ionization source outlet electrode.

[0015] The reactive gas inlet tube passes through the outer wall of the ionization source chamber, and its gas outlet extends into the reagent ion generation region. The outlet faces the gap between the repulsion electrode and the ion transport electrode plate near the repulsion electrode. The gas outlet is positioned facing the ultraviolet beam irradiation area. The reactive gas generates reagent ions or sample ions in the area through which the ultraviolet beam passes. The reagent ions or sample ions pass through the central through-hole of the isolation electrode and enter the ion molecular reaction region. The inlet of the reactive gas inlet tube is connected to a certain concentration of reactive gas through a three-way valve.

[0016] The sample gas inlet tube passes through the outer wall of the ionization source cavity, and its gas outlet end extends into the interior of the ion molecular reaction zone. The outlet end faces the gap between the isolation electrode and the ion transport electrode plate near the isolation electrode, and its gas outlet end is set facing the ion molecular reaction zone.

[0017] A through hole A is provided at the bottom of the ionization source cavity, and the ionization source outlet electrode is sealed to the bottom of the ionization source cavity; the circular through hole of the ionization source outlet electrode is provided corresponding to through hole A, that is, the sample ions pass through the circular through hole and through hole A of the ionization source outlet electrode and leave the ionization source cavity.

[0018] A gas outlet is provided on the side wall of the ionization source cavity. The gas outlet is connected to a pumping valve through a vacuum line. A vacuum pump is connected to the other end of the side pumping valve through a vacuum line.

[0019] The reaction gas contains a gas containing a reaction reagent, which is one or more of the following haloalkanes: CH2Br2, C2H4Br2, CH2Cl2, etc.

[0020] The sample gas contains alcohol C n H 2n+1A certain concentration of glyoxal solution is prepared using OH (n is an integer from 1 to 4) and water as solvents, and then the sample gas is diluted to a certain concentration using an online dynamic gas mixing system.

[0021] The ionization principle of cluster-mediated chemical ionization is as follows: The VUV Kr discharge lamp emits photons, which first collide with the reactant gas molecules to generate reagent ions S. + The reagent ion S + The sample is transferred to the ion-molecule reaction region via the isolation electrode (10); when glyoxal is introduced into the ion-molecule reaction region along with alcohol or water, chemical ionization occurs between the reagent ions and the glyoxal-alcohol cluster molecules or glyoxal-water cluster molecules, producing protonated molecular ions of the glyoxal-alcohol cluster, namely [C2H2O2·C n H 2n+1 OH·H] + (n is an integer from 1 to 4), or it can produce a protonated molecular ion of glyoxal-water clusters, i.e., [C2H2O2·H2O·H] + The glyoxal then enters the quality analyzer for analysis and detection, thus achieving efficient analysis and detection of glyoxal.

[0022] The reaction gas enters the reagent ion generation area through the reaction gas inlet tube. The reaction gas is a pure solution of the reaction reagent diluted to the required concentration by an online dynamic gas mixing system. The diluting gas is one or more of nitrogen, argon, helium or other rare gases with a mass purity greater than 99.999%.

[0023] The sample gas to be tested enters the ion molecular reaction zone through the sample gas inlet tube. The sample gas is prepared by using one or more solvents, such as alcohol or water, and then diluted to the required concentration by the online dynamic gas mixing system. The diluent gas is one or more of nitrogen, argon, helium or other rare gases with a mass purity greater than 99.999%.

[0024] The lower opening of the central through-hole of the isolation electrode is provided with a convex electrode with an annular protrusion coaxial with the through-hole, which can effectively prevent sample gas backflow and affect the ionization of reagent ions; the ultraviolet beam passes through each electrode through-hole along the axial direction of the electrode.

[0025] The lower end face of the annular protrusion is located above plane A, which is the upper surface of the electrode of the ion transport electrode near the isolation electrode. A gap is left between the lower end face of the annular protrusion and plane A. The gas outlet end of the sample gas inlet tube is set to the side wall of the annular protrusion.

[0026] The ultraviolet light source is a gas discharge lamp, a laser light source, or a synchrotron radiation light source.

[0027] Cluster-mediated chemical ionization sources can operate in two modes, simply by changing the type of gas in the reactant inlet tube and the electric field conditions in the ionization region.

[0028] The working gas pressure inside the ionization source is 10. -3 -10 5 Pa.

[0029] The mass analyzer is one of the following: quadrupole mass analyzer, ion trap mass analyzer, magnetic mass analyzer, time-of-flight mass analyzer, or any combination of two or more of the above mass analyzers.

[0030] The reaction gas inlet tube and the sample gas inlet tube can be metal capillaries or quartz capillaries, and there can be one or several; the length is 0.05~5 m, and the inner diameter is 25~500 μm.

[0031] The advantages of this method are as follows:

[0032] 1. Compared with direct photoionization, this method uses dibromomethane as a reagent ion. When glyoxal and high-concentration alcohol are co-injected, the cluster-mediated signal enhancement effect that occurs during the ionization of glyoxal is utilized to achieve efficient chemical ionization of glyoxal.

[0033] 2. The characteristic ion of glyoxal is the protonated molecular ion of a cluster, namely [C₂H₂O₂·C₂]. n H 2n+1 OH·H] + This can effectively avoid interference from other carbonyl compounds in its qualitative and quantitative analysis;

[0034] 3. Compared with GC-MS, this method does not require complicated sample pretreatment and can obtain a mass spectrum in 30 seconds, enabling rapid and highly sensitive detection. Attached Figure Description

[0035] Figure 1 This is a diagram of the experimental apparatus for the present invention;

[0036] Figure 2 The mass spectrum of formaldehyde under photoionization and reagent-assisted ionization with dibromomethane ions. Detailed Implementation

[0037] like Figure 1 As shown, a device and method for efficient detection of glyoxal via cluster-mediated chemical ionization includes an online dynamic gas mixing system 1 and an ionization source 2.

[0038] The online dynamic gas mixing system 1 includes a dilution gas source 3, a mass flow controller 4, a stainless steel gas mixing chamber 5, a micro-injection pump 6, a carrier gas pipeline, and an electric heating device 20 on the outer wall of the stainless steel gas mixing chamber. The carrier gas inlet of the stainless steel gas mixing chamber 5 is connected to the dilution gas source 3 through the carrier gas pipeline, and the outlet of the stainless steel gas mixing chamber 5 is connected to the reaction gas inlet pipe 14 or the sample gas inlet pipe 15 of the ionization source. The reaction gas or sample gas is introduced into the ionization region of the ionization source 2 through the three-way valve 7. The third port of the three-way valve 7 is connected to the atmosphere.

[0039] One or more of the following electric heating elements, electric heating belts, or electric heating wires are wound around the outer wall of the carrier gas pipeline, the outer wall of the stainless steel gas mixing chamber 5 and the outer wall of the tee 7, as well as the reaction gas inlet pipe 14 and the sample gas inlet pipe 15 to maintain constant temperature heating, and can work under ambient temperature - 300 ℃ conditions.

[0040] The working principle of the online dynamic gas mixing system is as follows: First, prepare the analyte solution or pure reagent of the required concentration. Then, use a micro-injection pump 6 to inject the pre-prepared solution into the heated gas mixing chamber 5 at a constant flow rate. At the same time, use a mass flow controller 4 to introduce a carrier gas of constant flow rate into the gas mixing chamber 5. By precisely controlling the flow rates of the prepared solution and the carrier gas, the required concentration of reagent and analytical gas can be obtained at the outlet of the gas mixing chamber 5.

[0041] The ionization source includes an ultraviolet light source 8, a reaction gas inlet tube 14, a sample gas inlet tube 15, and an ionization source cavity 16. The ionization source cavity 16 is characterized in that: the ionization source cavity 16 is a hollow sealed chamber, and a through hole is provided at the top of the ionization source cavity 16. The light window of the ultraviolet light source 8 extends into the ionization source cavity 16 through the through hole, and the ultraviolet light source 8 is sealed to the through hole.

[0042] Inside the ionization source cavity 16, along the emission direction of the ultraviolet beam emitted by the ultraviolet light source 8, an ion repulsion electrode 9, an ion transport electrode 11, an isolation electrode 10, an ion focusing electrode 12, and an ionization source outlet electrode 13 are arranged sequentially. All of these electrodes are annular structures with through holes in the middle, and they are spaced apart and placed in parallel by annular insulating pads with through holes in the middle. The through holes of the electrodes and the insulating pads are coaxial. The insulating pads are sealed to the adjacent electrode plates.

[0043] The isolation electrode 10 and the ion focusing electrode 12 divide the ionization region between the ion repulsion electrode 9 and the ionization source outlet electrode 13 into three chambers from top to bottom: the reagent ion generation region 21 located between the repulsion electrode 9 and the isolation electrode 10, the ion molecule reaction region 22 located between the isolation electrode 10 and the ion focusing electrode 12, and the ion focusing region 23 located between the ion focusing electrode 12 and the ionization source outlet electrode 13.

[0044] The reaction gas inlet tube 14 passes through the outer wall of the ionization source cavity 16, and its gas outlet end extends into the reagent ion generation region 21. The outlet end faces the space between the repulsion electrode 9 and the ion transport electrode 11 plate near the repulsion electrode 9. The gas outlet end is set facing the ultraviolet beam irradiation area. The reaction gas generates reagent ions or sample ions in the area through which the ultraviolet beam passes. The reagent ions or sample ions pass through the central through hole of the isolation electrode 10 and enter the ion molecule reaction region 22. The inlet end of the reaction gas inlet tube 14 is connected to a certain concentration of reaction gas 19 through a three-way valve.

[0045] The sample gas inlet tube 15 passes through the outer wall of the ionization source cavity 16, and its gas outlet end extends into the interior of the ion molecular reaction zone 22. The outlet end faces the gap between the isolation electrode 10 and the ion transport electrode 11 plate near the isolation electrode 10, and its gas outlet end is set facing the ion molecular reaction zone.

[0046] A through hole A is provided at the bottom of the ionization source cavity 16, and the ionization source outlet electrode 13 is sealed to the bottom of the ionization source cavity 16; the circular through hole of the ionization source outlet electrode 13 is provided corresponding to the through hole A, that is, the sample ions pass through the circular through hole and through hole A of the ionization source outlet electrode 13 and leave the ionization source cavity 16.

[0047] A gas outlet is provided on the side wall of the ionization source cavity 16. The gas outlet is connected to a suction valve 17 through a vacuum line. A vacuum pump 18 is connected to the other end of the side suction valve through a vacuum line.

[0048] The reaction gas contains a gas containing a reaction reagent, which is one or more of the following haloalkanes: CH2Br2, C2H4Br2, CH2Cl2, etc.

[0049] The sample gas contains alcohol C n H 2n+1 A certain concentration of glyoxal solution is prepared using OH (n is an integer from 1 to 4) and water as solvents, and then the sample gas is diluted to a certain concentration using an online dynamic gas mixing system.

[0050] The ionization principle of cluster-mediated chemical ionization is as follows: The VUV Kr discharge lamp emits photons, which first collide with the reactant gas molecules to generate reagent ions S. + The reagent ion S + The sample is transferred to the ion-molecule reaction region via the isolation electrode 10. When glyoxal is co-injected with alcohol or water into the ion-molecule reaction region, chemical ionization occurs between the reagent ions and the glyoxal-alcohol cluster molecules or glyoxal-water cluster molecules, producing protonated molecular ions of the glyoxal-alcohol cluster, namely [C2H2O2·C n H 2n+1 OH·H] +(n is an integer from 1 to 4), or it can produce a protonated molecular ion of glyoxal-water clusters, i.e., [C2H2O2·H2O·H] + The glyoxal then enters the quality analyzer 24 for analysis and detection, thereby achieving efficient analysis and detection of glyoxal.

[0051] The reaction gas enters the reagent ion generation zone 21 through the reaction gas inlet tube 14. The reaction gas is a pure solution of the reaction reagent diluted to the required concentration by the online dynamic gas mixing system 1. The diluting gas is one or more of nitrogen, argon, helium or other rare gases with a mass purity greater than 99.999%.

[0052] The sample gas to be tested enters the ion molecular reaction zone 22 through the sample gas inlet tube 15. The sample gas is prepared by using one or more of alcohol or water as a solvent, and then diluted to the required concentration by the online dynamic gas mixing system 1. The diluent gas is one or more of nitrogen, argon, helium or other rare gases with a mass purity greater than 99.999%.

[0053] The lower opening end of the central through hole of the isolation electrode 10 is provided with a convex electrode with an annular protrusion coaxial with the through hole, which can effectively prevent sample gas backflow and affect the ionization of reagent ions; the ultraviolet beam passes through each electrode through hole along the axial direction of the electrode.

[0054] The lower end face of the annular protrusion is located above the plane A on the upper surface of the electrode of the ion transport electrode, which is close to the lower part of the isolation electrode, and there is a gap between the lower end face of the annular protrusion and the plane A; the gas outlet end of the sample gas inlet tube 15 is set to the side wall of the annular protrusion.

[0055] The ultraviolet light source 8 is a gas discharge lamp, a laser light source, or a synchrotron radiation light source.

[0056] Cluster-mediated chemical ionization sources can operate in two modes, simply by changing the type of gas in the reactant inlet tube and the electric field conditions in the ionization region.

[0057] The reaction gas inlet tube 14 and the sample gas inlet tube 15 can be metal capillaries or quartz capillaries, and can be one or several; the length is 0.05~5 m and the inner diameter is 25~500 μm.

[0058] In practical implementation, based on the photoionization time-of-flight mass spectrometry of the VUV Kr discharge lamp, the gas pressure in the ionization region was adjusted to approximately 500 Pa. In photoionization (PI) mode, due to the low photoionization efficiency, glyoxal could not be effectively detected. In cluster-mediated chemical ionization (CMCI) mode, the injection flow rate of pure CH2Br2 reagent was set to 4.42 μL / min and the flow rate of clean air was set to 0.5 L / min. The concentration of CH2Br2 reagent gas entering the reagent ion generation region through the reaction gas injection tube 14 was 3200 ppm. CH2Br2 was generated after direct photoionization. + Reagent ions are transported to the ion-molecule reaction region via an isolating electrode. Taking ethanol as a solvent as an example, 0.5 ppm glyoxal and 400 ppm ethanol are jointly introduced into the ion-molecule reaction region through the sample gas inlet tube using an online dynamic gas mixing system. CH2Br2 + The reagent ions undergo chemical ionization with the glyoxal-ethanol cluster, producing a protonated molecular ion of the cluster, namely [C2H2O2·C2H5OH·H]. + .like Figure 2 The images shown are the mass spectra of glyoxal at 0.5 ppm under PI and CMCI conditions, respectively.

Claims

1. A method for detecting glyoxal via cluster-mediated chemical ionization, characterized in that: The apparatus used includes an online dynamic gas distribution system (1) and an ionization source (2): The online dynamic gas mixing system (1) includes a dilution gas source (3), a mass flow controller (4), a stainless steel gas mixing chamber (5), a micro-injection pump (6), a carrier gas pipeline, and an electric heating device (20) on the outer wall of the stainless steel gas mixing chamber. The carrier gas inlet of the stainless steel gas mixing chamber (5) is connected to the dilution gas source (3) through the carrier gas pipeline, and the outlet of the stainless steel gas mixing chamber (5) is connected to the reaction gas inlet pipe (14) or the sample gas inlet pipe (15) of the ionization source. The reaction gas or sample gas is introduced into the ionization zone of the ionization source (2) through the three-way valve (7). The third port of the three-way valve (7) is connected to the atmosphere. The electric heating device (20) is equipped with one or more of the following: an electric heating plate, an electric heating belt, or an electric heating wire, which maintains constant temperature heating. It is wrapped on the outer wall of the carrier gas pipeline, the outer wall of the stainless steel gas mixing chamber (5), the outer wall of the tee (7), the reaction gas inlet pipe (14), and the sample gas inlet pipe (15). It can work at room temperature -300 ℃. The working principle of the online dynamic gas mixing system is as follows: First, prepare the analyte solution or pure reagent of the required concentration. Then, use a micro-injection pump (6) to inject the pre-prepared solution into the heated gas mixing chamber (5) at a constant flow rate. At the same time, use a mass flow controller (4) to introduce a constant flow rate of carrier gas into the gas mixing chamber (5). By precisely controlling the flow rate of the prepared solution and the carrier gas, the required concentration of reagent and analytical gas can be obtained at the outlet of the gas mixing chamber (5). The ionization source includes an ultraviolet light source (8), a reaction gas inlet tube (14), a sample gas inlet tube (15), and an ionization source cavity (16). The ionization source cavity (16) is characterized in that: the ionization source cavity (16) is a hollow sealed chamber, and a through hole is provided at the top of the ionization source cavity (16). The light window of the ultraviolet light source (8) extends into the ionization source cavity (16) through the through hole, and the ultraviolet light source (8) is sealed to the through hole. Inside the ionization source cavity (16), along the ultraviolet light beam emission direction emitted by the ultraviolet light source (8), an ion repulsion electrode (9), an ion transport electrode (11), an isolation electrode (10), an ion transport electrode (11), an ion focusing electrode (12), and an ionization source outlet electrode (13) are arranged in sequence. All of these electrodes are annular structures with through holes in the middle, and they are spaced apart and placed in parallel by annular insulating pads with through holes in the middle. The through holes of the electrodes and the insulating pads are coaxial, and the insulating pads are sealed to the adjacent electrode plates. The isolation electrode (10) and the ion focusing electrode (12) divide the ionization region between the ion repulsion electrode (9) and the ionization source outlet electrode (13) into three chambers from top to bottom: the reagent ion generation region (21) between the repulsion electrode (9) and the isolation electrode (10), the ion molecule reaction region (22) between the isolation electrode (10) and the ion focusing electrode (12), and the ion focusing region (23) between the ion focusing electrode (12) and the ionization source outlet electrode (13). The reaction gas inlet tube (14) passes through the outer wall of the ionization source cavity (16), and its gas outlet end extends into the reagent ion generation area (21). The outlet end faces the gap between the repulsion electrode (9) and the ion transport electrode (11) near the repulsion electrode (9). Its gas outlet end is set facing the ultraviolet beam irradiation area. The reaction gas generates reagent ions or sample ions in the area through which the ultraviolet beam passes. The reagent ions or sample ions pass through the central through hole of the isolation electrode (10) and enter the ion molecule reaction area (22). The inlet end of the reaction gas inlet tube (14) is connected to a certain concentration of reaction gas (19) through a three-way valve (7). The sample gas inlet tube (15) passes through the outer wall of the ionization source cavity (16), and its gas outlet end extends into the interior of the ion molecular reaction zone (22). The outlet end faces the gap between the isolation electrode (10) and the ion transport electrode (11) plate near the isolation electrode (10), and its gas outlet end is set facing the ion molecular reaction zone. A through hole A is provided at the bottom of the ionization source cavity (16), and the ionization source outlet electrode (13) is sealed to the bottom of the ionization source cavity (16); the circular through hole of the ionization source outlet electrode (13) is provided corresponding to the through hole A, that is, the sample ions pass through the circular through hole and through hole A of the ionization source outlet electrode (13) and leave the ionization source cavity (16). A gas outlet is provided on the side wall of the ionization source cavity (16). The gas outlet is connected to a vacuum valve (17) through a vacuum pipeline. A vacuum pump (18) is connected to the other end of the side vacuum valve through a vacuum pipeline. The reaction gas contains a gas of the reaction reagent, which is one or more of CH2Br2, C2H4Br2, and CH2Cl2; The sample gas contains alcohol C n H 2n+1 A glyoxal solution of a certain concentration is prepared using one or more solvents, such as OH and water, and then diluted to a certain concentration of sample gas using an online dynamic gas mixing system (1). n H 2n+1 In OH, n is an integer from 1 to 4; The ionization principle of cluster-mediated chemical ionization is as follows: The VUV Kr discharge lamp emits photons, which first collide with the reactant gas molecules to generate reagent ions S. + The reagent ion S + The sample is transferred to the ion-molecule reaction region via the isolation electrode (10); when glyoxal is introduced into the ion-molecule reaction region along with alcohol or water, chemical ionization occurs between the reagent ions and the glyoxal-alcohol cluster molecules or glyoxal-water cluster molecules, producing protonated molecular ions of the glyoxal-alcohol cluster, namely [C2H2O2·C n H 2n+1 OH·H] + n is an integer from 1 to 4, or it can produce a protonated molecular ion of glyoxal-water cluster, i.e., [C2H2O2·H2O·H]. + The glyoxal then enters the quality analyzer (24) for analysis and detection, thereby achieving efficient analysis and detection of glyoxal.

2. The method according to claim 1, characterized in that: The reaction gas enters the reagent ion generation zone (21) through the reaction gas inlet tube (14). The reaction gas is a pure solution of the reaction reagent diluted to the required concentration by the online dynamic gas mixing system (1). The diluent gas is one or more of nitrogen, argon, helium or other rare gases with a mass purity greater than 99.999%.

3. The method according to claim 1, characterized in that: The sample gas to be tested enters the ion molecular reaction zone (22) through the sample gas inlet tube (15). The sample gas is prepared by one or more of alcohol or water as a solvent, and then diluted to the required concentration by the online dynamic gas mixing system (1). The diluent gas is one or more of nitrogen, argon, helium or other rare gases with a mass purity greater than 99.999%.

4. The method according to claim 1, characterized in that: The central through hole of the isolation electrode (10) has a convex electrode with an annular protrusion coaxial with the through hole at the lower opening end, which can effectively prevent sample gas backflow and affect the ionization of reagent ions; the ultraviolet beam passes through each electrode through hole along the axial direction of the electrode. The lower end face of the annular protrusion is located above the plane A on the upper surface of the electrode of the ion transport electrode near the lower part of the isolation electrode, and there is a gap between the lower end face of the annular protrusion and the plane A; the gas outlet end of the sample gas inlet tube (15) is set to the side wall of the annular protrusion.

5. The method according to claim 1, characterized in that: The ultraviolet light source (8) is a gas discharge lamp light source, a laser light source, or a synchrotron radiation light source.

6. The method according to claim 1, characterized in that: The working gas pressure inside the ionization source is 10. -3 -10 5 Pa.

7. The method according to claim 1, characterized in that: The mass analyzer (24) is one of a quadrupole mass analyzer, an ion trap mass analyzer, a magnetic mass analyzer, a time-of-flight mass analyzer, or any combination of two or more of the above mass analyzers.

8. The method according to claim 1, characterized in that: The reaction gas inlet tube (14) and the sample gas inlet tube (15) are metal capillaries or quartz capillaries, one or several in number; the length is 0.05~5 m and the inner diameter is 25~500 μm.

Images