Atmospheric pressure chemical ionization source and atmospheric pressure mass spectrometer

Abstract

The application belongs to the technical field of mass spectrum analysis, and particularly relates to an atmospheric pressure chemical ionization source and an atmospheric pressure mass spectrum. The ionization source shell, metal shell, curtain plate and skimmer electrode are sequentially connected. The ionization source shell is divided into a chemical ionization reaction chamber and a reagent ion reaction chamber by an electrode ring. The metal discharge needle is installed on the ionization source shell and extends into the chemical ionization reaction chamber. The electrode ring is arranged in the chemical ionization reaction chamber and the reagent ion reaction chamber. The chemical ionization reaction chamber, the reagent ion reaction chamber and the metal shell are respectively provided with air holes. The outer periphery of the electrode ring is sealingly connected with the inner wall of the ionization source shell, and a through hole is formed in the center of the electrode ring. The ionization source can effectively improve the chemical ionization by vertically fixing the discharge needle, and the ion transmission efficiency is enhanced by combining the ion transmission effect of the electrode ring, so that the sensitivity of the instrument is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of mass spectrometry analysis, in particular to an atmospheric pressure chemical ionization source and an atmospheric pressure mass spectrometer, which can be used for online detection of HCN in human exhaled breath. Background Art

[0002] Hydrocyanic acid (HCN) is present in trace amounts in human exhaled breath, at concentrations as low as 1 part per billion by volume (ppbv). The endogenous source of HCN can be traced back to the early studies of Goldstein and Rieders. The primary sources of HCN in healthy individuals are thiocyanate conversion, leukocyte immune responses, and oral enzyme oxidation. HCN is present in trace amounts in healthy human exhaled breath, at concentrations ranging from 1 to 62 ppb, and oral HCN concentrations are 2 to 14 times higher than nasal HCN concentrations.

[0003] Researchers have recently discovered that HCN concentrations in exhaled breath are associated with a variety of disease symptoms and metabolic behaviors. Because other in vitro testing methods (such as cough swabs and tissue extraction) are invasive, time-consuming, and unsuitable for individuals with difficulty producing sputum, exhaled breath HCN testing is considered a more appropriate screening method. Summary of the Invention

[0004] In order to efficiently ionize HCN, the present invention aims to provide an atmospheric pressure chemical ionization source and an atmospheric pressure mass spectrometer, which can generate O2 in the atmospheric pressure negative ion mode. - High concentration improves detection sensitivity.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] An atmospheric pressure chemical ionization source according to the present invention comprises a metal discharge needle, an ionization source housing, a metal shell, a curtain plate, and a skimmer electrode. The ionization source housing, the metal shell, the curtain plate, and the skimmer electrode are sequentially connected. The interior of the ionization source housing is divided into a chemical ionization reaction chamber and a reagent ion reaction chamber by an electrode ring. The metal discharge needle is mounted on the ionization source housing and extends into the chemical ionization reaction chamber. Both the chemical ionization reaction chamber and the reagent ion reaction chamber are provided with electrode rings. Air holes are respectively formed on the ionization source housing corresponding to the chemical ionization reaction chamber, the ionization source housing corresponding to the reagent ion reaction chamber, and the metal shell. The outer periphery of the electrode ring is sealedly connected to the inner wall of the ionization source housing, and a through hole is formed in the center of the electrode ring. The front surface of the curtain plate is in sealing contact with the metal shell, and the back surface of the curtain plate is in sealing contact with the skimmer electrode. The center of the curtain plate is provided with a through hole, and a single side hole is formed on the periphery of the through hole on the curtain plate. The single side hole is connected to the air hole on the metal shell. The back surface of the curtain plate is provided with a groove for connecting the single side hole with the through hole on the curtain plate.

[0007] Wherein: the ions generated in the chemical ionization reaction chamber can only enter the reagent ion reaction chamber through the electrode ring used to separate the chemical ionization reaction chamber and the reagent ion reaction chamber.

[0008] The sidewall of the chemical ionization reaction chamber, the reagent ion reaction chamber and the metal shell is provided with a gas hole, the axial direction of the gas hole provided on the sidewall is perpendicular to the metal discharge needle; the top surface of the ion source shell is also provided with a gas hole, the axial direction of the gas hole provided on the top surface is parallel to the metal discharge needle.

[0009] The concentration of negative ions in the chemical ionization reaction chamber and the reagent ion reaction chamber is controlled by adjusting the hot air and sample gas to enter through different gas holes and selecting different gas holes as tail gas outlets.

[0010] The electrode rings in the ion source shell are arranged in parallel and coaxially, and the axial center lines of the ion source shell, the metal shell, the curtain plate, the skimmer electrode and the electrode rings are collinear.

[0011] The metal shell is annular, and a space is left between the inner sidewall of the metal shell and the ion source shell; a gas channel is formed in the metal shell, one end of the gas channel communicates with the space between the metal shell and the ion source shell, and the other end of the gas channel communicates with the one-side hole; the gas hole provided on the metal shell communicates with the space between the metal shell and the ion source shell.

[0012] The metal discharge needle is a direct current corona discharge.

[0013] The curtain plate is a disc-shaped structure with a through hole in the middle, the front surface and the back surface of the curtain plate are provided with sealing grooves, and sealing rings for sealing with the metal shell or the skimmer electrode are arranged in the sealing grooves; an annular groove is arranged on the back surface of the curtain plate between the through hole and the sealing groove provided on the back surface, the one-side hole is arranged in the annular groove, a communication groove is arranged between the annular groove and the through hole, the communication groove is arranged along the radial direction of the curtain plate, and the two ends of the communication groove respectively communicate with the annular groove and the through hole.

[0014] The atmospheric pressure mass spectrometer comprises an atmospheric pressure chemical ionization source; the atmospheric pressure chemical ionization source and a mass analyzer are combined, the ion transmission efficiency is enhanced through the ion transmission effect of the electrode ring, and the sensitivity of the instrument is greatly improved.

[0015] The advantages and positive effects of the present application are as follows:

[0016] The atmospheric pressure chemical ionization source of the present application can effectively improve the chemical ionization by vertically fixing the metal discharge needle, the ion transmission efficiency is enhanced through the ion transmission effect of the electrode ring, and the sensitivity of the instrument is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Fig. 1 is a schematic diagram of the overall structure of the atmospheric pressure chemical ionization source of the present application;

[0018] Figure 2 Fig. 2 is another schematic diagram of the overall structure of the atmospheric pressure chemical ionization source of the present application;

[0019] Figure 3 Fig. 3 is a schematic diagram of the internal structure of the atmospheric pressure chemical ionization source of the present application;

[0020] Figure 4 Fig. 4 is another schematic diagram of the internal structure of the atmospheric pressure chemical ionization source of the present application;

[0021] Figure 5 Fig. 5 is a front view of the curtain plate of the present application;

[0022] Figure 6 Fig. 6 is a back view of the curtain plate of the present application;

[0023] Figure 7 Fig. 7 is a graph of the intensity of reagent ions under different supply voltages;

[0024] Wherein: 1 is a metal discharge needle, 2 is a chemical ionization reaction chamber, 3 is a reagent ion reaction chamber, 4 is an electrode ring A, 5 is an electrode ring B, 6 is an electrode ring C, 7 is an electrode ring D, 8 is a curtain plate, 9 is a skimmer electrode, 10 is a gas hole, 11 is an ionization source shell, 12 is a gas sealing plug, 13 is a metal shell, 14 is a single-sided hole, 15 is a sealing groove, 16 is an annular groove, and 17 is a communication groove. DETAILED DESCRIPTION

[0025] The present application will be further described in detail below with reference to the accompanying drawings.

[0026] As Figures 1 to 6As shown, the atmospheric pressure chemical ionization source of the present invention includes a metal discharge needle 1, an ionization source housing 11, a metal shell 13, a curtain plate 8, and a skimmer electrode 9. The ionization source housing 11, the metal shell 13, the curtain plate 8, and the skimmer electrode 9 are connected in sequence. The rear end of the curtain plate 8 is the mass spectrometry inlet skimmer electrode 9 leading to the ion transmission and mass spectrometry ion analysis system. The interior of the ionization source housing 11 is divided into a chemical ionization reaction chamber 2 and a reagent ion reaction chamber 3 by an electrode ring. The metal discharge needle 1 is mounted on the ionization source housing 11 and extends into the chemical ionization reaction chamber 2. Electrode rings are provided in both the chemical ionization reaction chamber 2 and the reagent ion reaction chamber 3. Air holes 10 are respectively formed on the ionization source housing 11 corresponding to the chemical ionization reaction chamber 2, the ionization source housing 11 corresponding to the reagent ion reaction chamber 3, and the metal shell 13. There are at least four to eight air holes 10. The outer periphery of the electrode ring is sealed to the inner wall of the ionization source housing 11, and a through hole is formed in the center of the electrode ring. The front of the curtain plate 8 is sealed against the metal shell 13, and the back of the curtain plate 8 is sealed against the skimmer electrode 9. A through hole is opened in the center of the curtain plate 8, and a single-sided hole 14 is opened on the periphery of the through hole on the curtain plate 8. The single-sided hole 14 is connected to the air hole 10 on the metal shell 13. A groove is provided on the back of the curtain plate 8 for connecting the single-sided hole 14 and the through hole on the curtain plate 8.

[0027] The ionization source housing 11 of this embodiment is divided into a chemical ionization reaction chamber 2 and a reagent ion reaction chamber 3 by an electrode ring B5. An electrode ring A4 is disposed within the chemical ionization reaction chamber 2, located above electrode ring B5. Within the reagent ion reaction chamber 3, electrode rings C6 and D7 are disposed below electrode ring B5, from top to bottom. The outer peripheries of electrode rings A4, B5, C6, and D7 are all sealed to the inner wall of the ionization source housing 11. The through holes defined in the centers of electrode rings A4, B5, C6, and D7 have varying diameters, ranging from 2 to 10 mm, and are ¼ the inner diameter of the reagent ion reaction chamber 3. The voltages of electrode rings A4, B5, C6, and D7 decrease sequentially from top to bottom. Airflow can flow between the chemical ionization reaction chamber 2 and the reagent ion reaction chamber 3 through electrode ring A5. The electrode rings A4 , B5 , C6 and D7 in the ionization source housing 11 are parallel and coaxially arranged, and collinear with the axial center lines of the ionization source housing 11 , the metal shell 13 , the curtain plate 8 and the skimmer electrode 9 .

[0028] The material of the metal discharge needle 1 can be selected based on user analysis requirements (e.g., 304 stainless steel, 316 stainless steel, tungsten steel, tungsten, or molybdenum). In this embodiment, the metal discharge needle 1 is made of 304 stainless steel and utilizes a DC corona discharge mechanism. The metal discharge needle 1 is located at the sealed end of the chemical ionization reaction chamber 2 and extends into the chemical ionization reaction chamber 2 along the axial direction of the ionization source housing 11.

[0029] The side walls of the chemical ionization reaction chamber 2, the reagent ion reaction chamber 3, and the metal shell 13 are provided with air holes 10, the axes of which are perpendicular to the metal discharge needle 1. The top surface of the ionization source housing 11 is also provided with air holes 10, the axes of which are parallel to the metal discharge needle 1. The chemical ionization reaction chamber 2 of this embodiment is provided with a set of two air holes 10, which are symmetrically located on either side of the axial centerline of the ionization source housing 11. The axial centerlines of the two air holes 10 are collinear and intersect perpendicularly with the axial centerline of the ionization source housing 11. The reagent ion reaction chamber 3 of this embodiment is provided with two groups of four air holes 10, one group of two air holes 10 located at the top is symmetrically located on both sides of the axial center line of the ionization source shell 11, and the axial center lines of the two air holes 10 are collinear; the other group of two air holes 10 located at the bottom is symmetrically located on both sides of the axial center line of the ionization source shell 11, and the axial center lines of the two air holes 10 are collinear; the axial center lines of the three groups of air holes 10 on the ionization source shell 11 are parallel and coplanar, and intersect perpendicularly with the axial center line of the ionization source shell 11. Each group of air holes 10 is located between two adjacent electrode rings. The ions generated in the chemical ionization reaction chamber 2 can only enter the reagent ion reaction chamber 3 through the electrode ring B5 used to separate the chemical ionization reaction chamber 2 and the reagent ion reaction chamber 3. By regulating the purge gas and sample gas to enter through different air holes 10 and selecting different air holes 10 as the exhaust gas outlet, the negative ion concentration in the chemical ionization reaction chamber 2 and the reagent ion reaction chamber 3 is regulated, so that the internal O2 - Concentration changes.

[0030] The metal shell 13 is an annular structure made of stainless steel, with a gap between the inner wall and the ionization source housing 11. An airway is opened inside the metal shell 13, one end of the airway is connected to the gap between the metal shell 13 and the ionization source housing 11, and the other end of the airway is connected to the single-side hole 14. The airway in this embodiment is L-shaped. The air hole 10 opened on the metal shell 13 leads to the gap between the metal shell 13 and the ionization source housing 11. Back-blowing gas is introduced through the air hole 10 opened on the metal shell 13, and the back-blowing gas is then introduced through the single-side hole 14; the introduced back-blowing gas ensures that the small holes on the Skimmer electrode 9 are not blocked by impurities in the sample, ensuring that the air path is completely sealed; the air holes 10 that are not used during work are blocked with gas sealing plugs 12 to prevent gas escape.

[0031] The curtain plate 8 of the embodiment is a disc structure with a through hole in the middle, the front and back surfaces of the curtain plate 8 are provided with sealing grooves 15, and the sealing grooves 15 are internally provided with sealing rings for sealing with the metal shell 13 or the skimmer electrode 9; the back surface of the curtain plate 8 is provided with an annular groove 16 between the through hole and the sealing groove 15 provided on the back surface, the single-sided hole 14 is provided in the annular groove 16, a communication groove 17 is provided between the annular groove 16 and the through hole, the communication groove 17 is provided along the radial direction of the curtain plate 8, and the two ends of the communication groove 17 are in communication with the annular groove 16 and the through hole, respectively. The front surface of the curtain plate 8 of the embodiment is provided with three circular sealing grooves 15 concentrically, and the single-sided hole 14 is located between the first and second sealing grooves 15 from the outside to the inside; the back surface of the curtain plate 8 is provided with one sealing groove 15. The communication grooves 17 of the embodiment are two, which are symmetrically arranged with the axial center line of the curtain plate 8 as the center, the center lines of the two communication grooves 17 are collinear, and the center lines of the two communication grooves 17 are perpendicular to the axial center line of the curtain plate 8.

[0032] The purge gas pipeline, the sample gas pipeline, the backflush gas pipeline and the tail gas pipeline connected with the gas hole 10 of the embodiment are all polytetrafluoroethylene pipes, the inner diameter is 3 mm, the length is 5-100 cm, the gas sample injection amount is 2-100 mL / min, and the vacuum degree in the ionization source shell 11 is maintained at 60-80 Pa.

[0033] The skimmer electrode 9 of the embodiment is a prior art, the inner diameter of the small hole (close to the middle through hole on the side of the curtain plate 8) on the skimmer electrode 9 is 100-150 μm, and the ions generated in the ionization zone enter the mass analyzer (i.e. mass spectrometer) outside the ionization source cavity through the small hole on the skimmer electrode 9. The mass analyzer of the embodiment is a time-of-flight mass analyzer in the prior art.

[0034] The atmospheric pressure mass spectrometer of the embodiment comprises an atmospheric pressure chemical ionization source and a mass analyzer (i.e. mass spectrometer), which are combined with the electrode ring ion transmission effect, enhance the ion transmission efficiency, and greatly improve the sensitivity of the instrument.

[0035] When the atmospheric pressure chemical ionization source of the embodiment works, two gas holes 10 are symmetrically arranged on the left and right sides of the axial section of the chemical ionization reaction chamber 2, which are respectively marked as A and B; two gas holes 10 are symmetrically arranged on the left and right sides of the axial section of the reagent ion reaction chamber 3, which are respectively marked as C and D; the gas sealing plug 12 in the gas hole 10 on the top of the chemical ionization reaction chamber 2 is removed; the gas hole 10 on the metal shell 13 is marked as E. In the working mode, A is the purge gas inlet, C is the sample gas inlet, E is the backflush gas inlet, G is the tail gas outlet, and the rest B and D are plugged from the outside by the gas sealing plug 12.

[0036] The gases used for the purge gas and the backflush gas are all air filtered by activated carbon and / or silica gel molecular sieve, and the sample gas is HCN. The backflush gas flow is at least 2 times the purge gas flow.

[0037] Experimental example

[0038] In the working mode, the purge gas flow rate is set to 500mL / min, and the back-blowing gas flow rate is set to 1000mL / min. In order to keep the internal atmospheric pressure, the tail gas outlet maintains the atmospheric pressure unchanged, and the excess tail gas inside is naturally discharged from the ionization area. - (After the CID process, O2 - (H2O)n, CO3 - The bound water (H2O)n has been removed and is shown as O2 in the figure - ) to perform detection statistics and obtain the signal strength. The statistical results are as follows Figure 7 shown.

Claims

1. An atmospheric pressure chemical ionization source, characterized in that: The invention comprises a metal discharge needle (1), an ionization source housing (11), a metal shell (13), a curtain plate (8) and a skimmer electrode (9), wherein the ionization source housing (11), the metal shell (13), the curtain plate (8) and the skimmer electrode (9) are connected in sequence, and the interior of the ionization source housing (11) is divided into a chemical ionization reaction chamber (2) and a reagent ion reaction chamber (3) by an electrode ring, and the metal discharge needle (1) is installed on the ionization source housing (11) and extends into the chemical ionization reaction chamber (2), and the chemical ionization reaction chamber (2) and the reagent ion reaction chamber (3) are both provided with electrode rings; the chemical ionization reaction chamber (2) is provided with an electrode ring on the ionization source housing (11) corresponding to the chemical ionization reaction chamber (2), and the reagent ion reaction chamber (3) is provided with an electrode ring. Air holes (10) are respectively provided on the ionization source housing (11) and the metal shell (13) corresponding to the sub-reaction chamber (3); the outer periphery of the electrode ring is sealed and connected to the inner wall of the ionization source housing (11), and a through hole is provided in the center of the electrode ring; the front of the curtain plate (8) is sealed and abutted against the metal shell (13), and the back of the curtain plate (8) is sealed and abutted against the skimmer electrode (9), a through hole is provided in the center of the curtain plate (8), and a single-side hole (14) is provided on the periphery of the through hole on the curtain plate (8), the single-side hole (14) is connected to the air hole (10) on the metal shell (13), and a groove for connecting the single-side hole (14) and the through hole on the curtain plate (8) is provided on the back of the curtain plate (8).

2. The atmospheric pressure chemical ionization source according to claim 1, wherein: The ions generated in the chemical ionization reaction chamber (2) can only enter the reagent ion reaction chamber (3) through the electrode ring used to separate the chemical ionization reaction chamber (2) and the reagent ion reaction chamber (3).

3. The atmospheric pressure chemical ionization source according to claim 1, wherein: The side walls of the chemical ionization reaction chamber (2), the reagent ion reaction chamber (3) and the metal shell (13) are provided with air holes (10), and the axial direction of the air holes (10) provided on the side walls is perpendicular to the metal discharge needle (1); the top surface of the ionization source housing (11) is also provided with air holes (10), and the axial direction of the air holes (10) provided on the top is parallel to the metal discharge needle (1).

4. The atmospheric pressure chemical ionization source according to claim 1, wherein: By regulating the hot air and sample gas to enter through different air holes (10) and selecting different air holes (10) as tail gas outlets, the negative ion concentrations in the chemical ionization reaction chamber (2) and the reagent ion reaction chamber (3) are regulated.

5. The atmospheric pressure chemical ionization source according to claim 1, wherein: The electrode rings in the ionization source housing (11) are parallel to each other and coaxially arranged, and the axial center lines of the ionization source housing (11), the metal shell (13), the curtain plate (8), the skimmer electrode (9) and the electrode rings are collinear.

6. The atmospheric pressure chemical ionization source according to claim 1, characterized in that: The metal shell (13) is annular, with a gap between the inner wall and the ionization source housing (11). An air passage is provided inside the metal shell (13), one end of the air passage is connected to the gap between the metal shell (13) and the ionization source housing (11), and the other end of the air passage is connected to the single-side hole (14); the air hole (10) provided on the metal shell (13) is connected to the gap between the metal shell (13) and the ionization source housing (11).

7. The atmospheric pressure chemical ionization source according to claim 1, characterized in that: The metal discharge needle (1) is a direct current corona discharge.

8. The atmospheric pressure chemical ionization source according to claim 1, wherein: The curtain plate (8) is a disc-shaped structure with a through hole in the middle. The front and back sides of the curtain plate (8) are both provided with sealing grooves (15), and the sealing grooves (15) contain sealing rings for sealing with the metal shell (13) or the skimmer electrode (9). The back side of the curtain plate (8) is provided with an annular groove (16) between the through hole and the sealing groove (15) provided on the back side. The single-side hole (14) is provided in the annular groove (16). A connecting groove (17) is provided between the annular groove (16) and the through hole. The connecting groove (17) is provided along the radial direction of the curtain plate (8), and the two ends of the connecting groove (17) are respectively connected with the annular groove (16) and the through hole.

9. An atmospheric pressure mass spectrometer, characterized in that: The method comprises the atmospheric pressure chemical ionization source according to any one of claims 1 to 6.

10. The atmospheric pressure mass spectrometer according to claim 9, characterized in that: The atmospheric pressure chemical ionization source is coupled with a mass analyzer.

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