Device capable of efficiently dissociating hydrated cluster ions in ionization source

Abstract

The invention belongs to the technical field of mass spectrometry instruments, and particularly relates to a device capable of efficiently dissociating hydrated cluster ions in an ionization source, which comprises a sample introduction tube, a vacuum ultraviolet lamp, an ionization source cavity, a repulsion electrode, a transmission electrode group and a vacuum pump, the vacuum ultraviolet lamp, the repulsion electrode and the transmission electrode group are respectively and sequentially arranged in the ionization source cavity, a direct current voltage is applied to the repulsion electrode, and a direct current voltage and a radio frequency voltage are applied to the transmission electrode group. According to the invention, on one hand, the heating effect of the radio frequency electric field on the ions is utilized, and on the other hand, the high-energy photoelectrons in the radio frequency electric field can fully collide with the hydration cluster ions, so that efficient dissociation of the hydration cluster ions under high air pressure is realized; in addition, the introduction of the radio frequency electric field also prolongs the molecular ion reaction time and enables the sample ions to be further focused in the ionization source, so that the transmission efficiency of the sample ions is improved, and the detection sensitivity of the instrument is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of mass spectrometry instruments, and specifically relates to a device capable of efficiently dissociating hydrated cluster ions in an ionization source. Background Art

[0002] The photoionization technology based on commercial vacuum ultraviolet lamps is an attractive soft ionization technology. Photoionization itself has excellent ionization efficiency, high molecular ion yield, and easy-to-interpret spectra. Using a simple and compact vacuum ultraviolet lamp as the light source reduces the usage cost, so it is widely used in environmental analysis, clinical diagnosis, industrial process monitoring and other fields.

[0003] In addition, in the photoionization source, selecting different reagent gases to generate reagent ions under the action of photoionization and performing ion-molecule reactions with sample molecules (M) effectively broadens the detection range of the photoionization source. However, in the proton transfer reaction using water as the reagent ion, a large number of hydrated cluster ions H3O + ·(H2O) n (n = 1, 2) and [MH] + ·(H2O) n (n = 1, 2) are generated. This not only increases the complexity of spectrum analysis but also reduces the ionization ability of the reagent ions. More importantly, as the pressure in the ionization source increases, the proportion of cluster ions also increases. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide a device capable of efficiently dissociating hydrated cluster ions in an ionization source.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A device capable of efficiently dissociating hydrated cluster ions in an ionization source, comprising a sampling tube, a vacuum ultraviolet lamp, an ionization source cavity, a repulsion electrode, a transmission electrode group, and a vacuum pump;

[0007] The ionization source cavity is respectively provided with a vacuum pumping port and an ion output port, and the vacuum pumping port is connected to the vacuum pump;

[0008] The vacuum ultraviolet lamp, the repulsion electrode, and the transmission electrode group are respectively installed inside the ionization source cavity in sequence. The light emitted from the light source emitting end of the vacuum ultraviolet lamp sequentially passes through the repulsion electrode and the transmission electrode group. The vacuum ultraviolet lamp is located on the side of the repulsion electrode away from the ion output port, and the transmission electrode group is located on the side of the repulsion electrode close to the ion output port;

[0009] There are two sample introduction tubes. One end of one of the sample introduction tubes is located outside the ionization source cavity and is connected to an external water vapor source. One end of the other sample introduction tube is located outside the ionization source cavity and is used to allow sample molecules to enter the ionization source cavity through the sample introduction tube. The other ends of the two sample introduction tubes both penetrate into the ionization source cavity and extend to the position between the repulsion electrode and the transmission electrode group;

[0010] A DC voltage is applied to the repulsion electrode, and a DC voltage and an RF voltage are applied to the transmission electrode group.

[0011] A valve is provided on the vacuum pumping port.

[0012] A mass analyzer is provided outside the ionization source cavity, and the sample input end of the mass analyzer is connected to the ion output port.

[0013] The vacuum pumping port is arranged at the top of the ionization source cavity, the ion output port is arranged on the side surface of the ionization source cavity, the axial center line of the vacuum pumping port is perpendicular to the horizontal plane, and the axial center lines of the ion output port and the light source emitting end of the vacuum ultraviolet lamp are both parallel to the horizontal plane.

[0014] The axial center lines of the two sample introduction tubes are both parallel to the axial center line of the light source emitting end of the vacuum ultraviolet lamp.

[0015] The repulsion electrode is a ring-shaped flat plate structure with a circular through-hole in the middle;

[0016] The transmission electrode group is composed of several layers of parallel and equally spaced ring-shaped electrodes all having circular through-holes, and the aperture sizes of the circular through-holes of each ring-shaped electrode are all equal.

[0017] All the ring-shaped electrodes of the transmission electrode group have the same thickness.

[0018] The DC voltages applied to the repulsion electrode and each ring-shaped electrode of the transmission electrode group decrease in sequence along the direction of the light emitted from the light source emitting end of the vacuum ultraviolet lamp to form a DC gradient electric field.

[0019] The RF peak-to-peak amplitudes of any two adjacent ring-shaped electrodes in the transmission electrode group are equal and the phases are opposite.

[0020] The center line of the circular through-hole of the repulsion electrode, the center lines of the circular through-holes of all the ring-shaped electrodes of the transmission electrode group, the axial center line of the ion output port, and the axial center line of the light source emitting end of the vacuum ultraviolet lamp are all collinear.

[0021] The advantages and positive effects of the present invention are:

[0022] In the present invention, on the one hand, the heating effect of the radio frequency electric field on ions is utilized, and on the other hand, high-energy photoelectrons in the radio frequency electric field can collide sufficiently with hydrated cluster ions, thereby realizing the efficient dissociation of hydrated cluster ions under high pressure. In addition, the introduction of the radio frequency electric field also increases the molecular ion reaction time and further focuses the sample ions in the ionization source, improving the transmission efficiency of the sample ions and greatly enhancing the detection sensitivity of the instrument. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the present invention.

[0024] In the figure: 1 is a sampling tube, 2 is a vacuum ultraviolet lamp, 3 is an ionization source cavity, 4 is a repulsion electrode, 5 is a valve, 6 is a vacuum pump, and 7 is a transmission electrode group. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following further describes the present invention in conjunction with the Figure 1 accompanying drawings in detail.

[0026] A device capable of efficiently dissociating hydrated cluster ions in an ionization source, as Figure 1 shown, in this embodiment, it includes a sampling tube 1, a vacuum ultraviolet lamp 2, an ionization source cavity 3, a repulsion electrode 4, a transmission electrode group 7, and a vacuum pump 6.

[0027] The ionization source cavity 3 is respectively provided with a vacuum pumping port and an ion output port, and the vacuum pumping port is connected to the vacuum pump 6. The vacuum pump 6 pumps out the gas in the ionization source cavity 3 through the vacuum pumping port, making the ionization source cavity 3 form a negative pressure; the air pressure in the ionization source cavity 3 generally remains at 10 - 1000 Pa. The vacuum pump 6 is a commercially available product and is controlled by an external controller.

[0028] The vacuum ultraviolet lamp 2, the repulsion electrode 4, and the transmission electrode group 7 are respectively installed inside the ionization source cavity 3 in sequence. The light emitted from the light source emitting end of the vacuum ultraviolet lamp 2 passes through the repulsion electrode 4 and the transmission electrode group 7 in sequence. The vacuum ultraviolet lamp 2 is located on the side of the repulsion electrode 4 away from the ion output port, and the transmission electrode group 7 is located on the side of the repulsion electrode 4 close to the ion output port. The installation structures of the vacuum ultraviolet lamp 2, the repulsion electrode 4, and the transmission electrode group 7 adopt existing technologies. A DC voltage is applied to the repulsion electrode 4, and a DC voltage and a radio frequency voltage are applied to the transmission electrode group 7.

[0029] There are two sample introduction tubes 1. One end of one sample introduction tube 1 is located outside the ionization source cavity 3 and is connected to an external water vapor source. The other end of the other sample introduction tube 1 is located outside the ionization source cavity 3 and is used to allow sample molecules to enter the ionization source cavity 3 through the sample introduction tube 1. The other ends of the two sample introduction tubes 1 both penetrate into the ionization source cavity 3 and extend to the position between the repelling electrode 4 and the transmission electrode group 7. The setting of the external water vapor source adopts the prior art. One end of the other sample introduction tube 1 can be directly placed in an environment with sample molecules or can be connected to the source providing the sample molecules.

[0030] Specifically, in this embodiment, a valve 5 is provided on the vacuum pumping port for controlling the opening and closing of the vacuum pumping port. The valve 5 is a commercially available needle valve, which is convenient for opening and closing adjustment.

[0031] Specifically, in this embodiment, a mass analyzer is provided outside the ionization source cavity 3. The sample input end of the mass analyzer is connected to the ion output port. The ions discharged from the ion output port are received by the mass analyzer for subsequent detection. The setting method of the mass analyzer is the prior art. In this embodiment, the mass analyzer can be a commercially available time-of-flight mass analyzer, quadrupole mass analyzer, ion trap mass analyzer, sector magnetic field mass analyzer or ion cyclotron resonance mass analyzer.

[0032] Specifically, in this embodiment, the vacuum pumping port is provided at the top of the ionization source cavity 3, and the ion output port is provided on the side surface of the ionization source cavity 3. The axial center line of the vacuum pumping port is perpendicular to the horizontal plane, and the axial center lines of the ion output port and the light source emitting end of the vacuum ultraviolet lamp 2 are both parallel to the horizontal plane; the axial center lines of the two sample introduction tubes 1 are both parallel to the axial center line of the light source emitting end of the vacuum ultraviolet lamp 2, which is easy to manufacture and can ensure the detection accuracy. In this embodiment, the vacuum ultraviolet lamp 2 can be a commercially available low-pressure inert gas discharge lamp, such as: krypton (Kr) discharge lamp, deuterium (D2) discharge lamp, xenon (Xe) discharge lamp, etc. In this embodiment, the sample introduction tube 1 can be a capillary tube made of stainless steel, quartz or polyether ether ketone (PEEK), etc., with an inner diameter of 50 - 500 μm and a length of 10 - 60 cm.

[0033] Specifically, in this embodiment, the repelling electrode 4 is a ring-shaped flat plate structure with a circular through hole in the middle. The thickness of the repelling electrode 4 is 1 - 8 mm, and the diameter of the circular through hole is 2 - 6 mm.

[0034] In this embodiment, the transmission electrode group 7 is composed of six layers of annular pole pieces arranged in parallel at equal intervals and each having a circular through-hole. The aperture sizes of the circular through-holes of all the annular pole pieces are equal, all being 8 - 20 mm. In this embodiment, the thicknesses of all the annular pole pieces of the transmission electrode group 7 are the same, all being 1 - 6 mm. In this embodiment, the repulsion electrode 4 and all the annular pole pieces of the transmission electrode group 7 can be made of a conductive metal (such as stainless steel, etc.) or a flat plate with a conductive metal layer plated on its surface. In this embodiment, the axial centerlines of the circular through-holes of the repulsion electrode 4, all the annular pole pieces of the transmission electrode group 7, the axial centerline of the ion output port, and the axial centerline of the light-emitting end of the light source of the vacuum ultraviolet lamp 2 are collinear and parallel to the horizontal plane.

[0035] Specifically, in this embodiment, the DC voltages applied to the repulsion electrode 4 and each annular pole piece of the transmission electrode group 7 decrease successively along the direction of the light emitted from the light-emitting end of the light source of the vacuum ultraviolet lamp 2 to form a DC gradient electric field, and the gradient voltage corresponding to this DC gradient electric field is 1 - 20 V / cm; the radio frequency applied to the transmission electrode group 7 has a frequency of 0.5 - 5 MHz and a radio frequency peak-to-peak value of 10 - 500 V. The radio frequency peak-to-peak amplitudes of any two adjacent annular pole pieces in the transmission electrode group 7 are equal and the phases are opposite. The setting method of the voltages at each place and the energization method of the repulsion electrode 4 and each annular pole piece of the transmission electrode group 7 both adopt the prior art.

[0036] Working principle:

[0037] During operation, the sample molecules to be measured and the required water vapor respectively enter the ionization source cavity 3 from the two sample introduction tubes 1. The gas in the ionization source cavity 3 is pumped out through the vacuum pumping port by the vacuum pump 6 to make the ionization source cavity 3 form a negative pressure, which enables the sample molecules (M) to be measured and the required water vapor to enter smoothly and efficiently; after the sample molecules (M) and water vapor are introduced into the interior of the ionization source cavity 3, various hydrated cluster ions will be formed in the case of a high water vapor content; by adjusting the radio frequency voltage on the transmission electrode group 7, high-energy photoelectrons can collide fully with the hydrated cluster ions to effectively dissociate the hydrated cluster ions and reduce the complexity of spectral analysis; in addition, the introduction of the radio frequency electric field also increases the molecular ion reaction time and further focuses the sample ions in the ionization source, improving the transmission efficiency and enhancing the sensitivity.

Claims

1. An apparatus capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: It includes a sampling tube (1), a vacuum ultraviolet lamp (2), an ionization source cavity (3), a repulsion electrode (4), a transmission electrode group (7), and a vacuum pump (6); The ionization source cavity (3) is respectively provided with a vacuum pumping port and an ion output port, and the vacuum pumping port is connected to the vacuum pump (6); The vacuum ultraviolet lamp (2), the repulsion electrode (4), and the transmission electrode group (7) are respectively and sequentially installed inside the ionization source cavity (3). The light emitted from the light source emitting end of the vacuum ultraviolet lamp (2) sequentially passes through the repulsion electrode (4) and the transmission electrode group (7). The vacuum ultraviolet lamp (2) is located on one side of the repulsion electrode (4) away from the ion output port, and the transmission electrode group (7) is located on one side of the repulsion electrode (4) close to the ion output port; There are two sampling tubes (1). One end of one sampling tube (1) is located outside the ionization source cavity (3) and is connected to an external water vapor source. One end of the other sampling tube (1) is located outside the ionization source cavity (3) and is used to allow sample molecules to enter the ionization source cavity (3) through the sampling tube (1). The other ends of the two sampling tubes (1) both penetrate into the ionization source cavity (3) and extend to the position between the repulsion electrode (4) and the transmission electrode group (7); A DC voltage is applied to the repulsion electrode (4), and a DC voltage and an RF voltage are applied to the transmission electrode group (7).

2. The apparatus according to claim 1, capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: A valve (5) is provided on the vacuum pumping port.

3. The apparatus according to claim 1, capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: A mass analyzer is provided outside the ionization source cavity (3), and the sample input end of the mass analyzer is connected to the ion output port.

4. The apparatus according to claim 1, capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: The vacuum pumping port is arranged at the top of the ionization source cavity (3), the ion output port is arranged on the side surface of the ionization source cavity (3), the axial center line of the vacuum pumping port is perpendicular to the horizontal plane, and the axial center lines of the ion output port and the light source emitting end of the vacuum ultraviolet lamp (2) are both parallel to the horizontal plane.

5. The apparatus according to claim 1, capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: The axial center lines of the two sampling tubes (1) are both parallel to the axial center line of the light source emitting end of the vacuum ultraviolet lamp (2).

6. The apparatus according to claim 1, capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: The repulsion electrode (4) is a ring-shaped flat plate structure with a circular through hole in the middle; The transmission electrode group (7) is divided into several layers of parallel and equally spaced ring-shaped electrodes all having circular through holes, and the aperture sizes of the circular through holes of each ring-shaped electrode are all equal.

7. The apparatus according to claim 6, capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: The thicknesses of all the ring-shaped electrodes of the transmission electrode group (7) are the same.

8. The apparatus according to claim 6, capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: The DC voltages applied to the repulsion electrode (4) and each ring-shaped electrode of the transmission electrode group (7) decrease sequentially along the direction of the light emitted from the light source emitting end of the vacuum ultraviolet lamp (2) to form a DC gradient electric field.

9. The apparatus according to claim 6, capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: The RF peak-to-peak amplitudes of any two adjacent ring-shaped electrodes in the transmission electrode group (7) are equal and the phases are opposite.

10. The apparatus according to claim 6, capable of efficiently dissociating hydrated cluster ions in an ionization source, characterized in that: The center line of the circular through hole of the repulsion electrode (4), the center lines of the circular through holes of all the ring-shaped electrodes of the transmission electrode group (7), the axial center line of the ion output port, and the axial center line of the light source emitting end of the vacuum ultraviolet lamp (2) are all collinear.

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