High efficiency spatially focused vuv ionization source

Abstract

The present application relates to ionization source in analytical instrument, specifically, it is a kind of high-efficiency spatial focusing VUV ionization source, including hollow closed cylindrical cavity, VUV lamp and convex lens and ion exit are respectively arranged at the both ends of closed cylindrical cavity;VUV lamp, convex lens, cylindrical cavity and ion exit are sequentially arranged;Sample inlet is arranged at the side of closed cylindrical cavity near convex lens;Ionization reaction focusing zone is arranged in the inside of closed cylindrical cavity;At least one ion transmission zone is arranged in the inside of closed cylindrical cavity, near the side of ion exit, and the ion transmission zone is composed of two pairs of cylindrical electrodes;Tail gas outlet is arranged at the side of closed cylindrical cavity, between cylindrical electrode and cylindrical electrode;Ion extraction electrode is arranged at the side of closed cylindrical cavity;The ionization source and mass spectrum or ion mobility spectrum are combined, and the focal size of ion can be reduced, and the ion transmission efficiency and detection sensitivity when passing through sampling micropore are improved.

Description

Technical Field

[0001] This invention relates to ionization sources in analytical instruments, specifically a high-efficiency VUV photoionization source technology. Specifically, it achieves efficient spatial overlap between the sample and VUV light through a special design, improving ionization efficiency. Simultaneously, a radio frequency electric field is applied to the ionization reaction region to spatially focus ions, avoiding ion loss due to radial divergence and improving ion utilization efficiency. Furthermore, the size of the beam spot is controlled using a convex lens, combined with ion focusing, to enhance ion utilization during mass spectrometry detection. Background Technology

[0002] Ionization sources are one of the key technologies in ion-type detection instruments such as mass spectrometry and ion mobility spectrometry. Traditional ion mobility spectrometry commonly uses radioactive ionization sources. 63 Ni ionization source. 63 Ni can emit beta rays with an average energy of 17 keV. After undergoing a series of complex reactions with the carrier gas, it finally forms reagent ions H₃O. + (Positive ion detection mode) and O2 _ (Negative ion detection mode) The reagent ions react with the sample to ionize it. Radioactivity 63 Ni ionization sources are favored by scientists due to their simplicity, stability, and lack of external power supply. However, their radioactivity necessitates safety inspections and special safety measures, which bring many challenges to their practical application. Furthermore... 63 The ion concentration produced by Ni ionization sources is not high enough, resulting in weak ion mobility spectra and a small linear range. Therefore, in recent years, researchers have been actively seeking non-radioactive ionization sources to replace traditional radioactive ones. 63 Ni ionization sources. Several non-radioactive ionization sources used in ion mobility spectrometry include photoionization sources (including VUV lamps and lasers), corona discharge ionization sources, and electrospray ionization sources specifically designed for ionizing liquids.

[0003] The aforementioned ionization sources are all surface ionization sources, typically exceeding 5 mm in diameter. To ensure high vacuum in mass spectrometry, sampling orifices of only a few tenths of a millimeter are usually used for sample introduction. This results in the loss of a large number of product ions generated during ionization. Furthermore, atmospheric pressure ionization sources usually contain a large number of reactant ions, which can cause ion trap mass spectrometry and quadrupole mass spectrometry storage saturation, limiting the number of target ions and affecting sensitivity. Additionally, the Coulomb repulsion generated by these ions can affect resolution. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art, and to concentrate a large-scale ionization source under atmospheric pressure into a microfocus to provide ion utilization efficiency and enable ion screening, thereby improving mass spectrometry sensitivity and resolution.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A space-focused VUV ionization source

[0007] It includes a hollow, sealed cylindrical cavity, with a VUV lamp and an ion outlet at each end of the sealed cylindrical cavity; the light outlet of the VUV lamp faces the inside of the cavity, and a convex lens is provided at the light outlet of the VUV lamp. The emitted light from the VUV lamp is transmitted along the axis of the cavity after passing through the convex lens. The VUV lamp, convex lens, cylindrical cavity and ion outlet are arranged in sequence from left to right.

[0008] The beam adjustment zone, composed of VUV lamps and convex lenses, adjusts the beam diameter according to the size of the ion outlet;

[0009] A sample inlet is provided on the side of the sealed cylindrical cavity near the convex lens;

[0010] Inside the sealed cylindrical cavity, near the left side of the convex lens, there is at least one quadrupole electrode consisting of two pairs of cylindrical electrodes A, with the axis of the quadrupole electrode coaxial with the axis of the cavity; serving as the focusing area for the ionization reaction.

[0011] Inside the sealed cylindrical cavity, near the ion outlet, there is at least one quadrupole electrode consisting of two pairs of cylindrical electrodes B, with the axis of the quadrupole electrode coaxial with the axis of the cavity; serving as the ion transport region.

[0012] An exhaust gas outlet is provided on the side wall of a sealed cylindrical cavity between cylindrical electrode A and cylindrical electrode B;

[0013] An ion extraction electrode is provided at the right end of the sealed cylindrical cavity.

[0014] The ionization source, with cylindrical electrodes A and B positioned close to the inner wall of a sealed cylindrical cavity, ensures that the sample is ionized and bound in the ionization reaction focusing region and bound in the ion transport region. The diameter of the internal cavity of the quadrupole electrode surrounded by cylindrical electrode A is smaller than the diameter of the internal cavity of the quadrupole electrode surrounded by cylindrical electrode B. The amplitude of the radio frequency power supply applied to cylindrical electrode A is smaller than the amplitude of the radio frequency power supply applied to cylindrical electrode B. The frequency of the radio frequency power supply applied to cylindrical electrode A is smaller than the frequency of the radio frequency power supply applied to cylindrical electrode B.

[0015] In the ionization source, radio frequency voltage and DC voltage U1 with opposite phases are applied to two pairs of cylindrical electrodes in the ionization reaction focusing region; radio frequency voltage and DC voltage U2 with opposite phases are applied to two pairs of cylindrical electrodes in the ion transport region; and DC voltage U3 is applied to the ion extraction electrode. During positive ion detection, the potentials of DC voltages U1, U2, and U3 gradually decrease; during negative ion detection, the potentials of DC voltages U1, U2, and U3 gradually increase.

[0016] The cylindrical electrode pairs described herein have a length greater than 1 cm, and the number of electrode pairs is no less than two. An radio frequency power supply, with a frequency between 50 Hz and 13.6 MHz, powers the discharge electrode pairs; this power supply is an isolated power supply with an isolation withstand voltage of 200 to 5000 V. The ionization source is used in conjunction with mass spectrometry or ion mobility spectrometry to reduce the focal spot size of ions, thereby improving ion transmission efficiency and detection sensitivity when passing through the sampling micropore.

[0017] Application of the ionization source in mass spectrometry or ion mobility spectrometry.

[0018] The application is characterized in that: the ionization source, when used in conjunction with mass spectrometry or ion mobility spectrometry, can reduce the focal size of ions and improve the ion transmission efficiency and detection sensitivity when passing through the sampling micropore.

[0019] The advantages of this invention are: This invention provides a spatially focused VUV ionization source, which interacts the quadrupole transport region and the ionization reaction region to improve ionization and transport efficiency; furthermore, the secondary space compression and transport are used to reduce the size of ions, which is beneficial to improving ion utilization efficiency and sensitivity. Attached Figure Description

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0021] Figure 1 Schematic diagram of the structure of a high-efficiency VUV photoionization source. Cylindrical cavity (1), VUV lamp (2), sample inlet (3), exhaust gas outlet (4), near ion outlet (5), cylindrical electrode A (6), cylindrical electrode B (7), convex lens (8), ion extraction electrode (11), ionization reaction focusing region (9), ion transport region (10).

[0022] Figure 2 Image of mass spectrometry coupled with ionization source and ion trap. Detailed Implementation

[0023] A space-focused VUV ionization source

[0024] It includes a hollow, sealed cylindrical cavity, with a VUV lamp and an ion outlet at each end of the cavity; the light outlet of the VUV lamp faces the inside of the cavity, and a convex lens is provided at the light outlet of the VUV lamp. The emitted light from the VUV lamp is transmitted along the axis of the cavity after passing through the convex lens. The VUV lamp, convex lens, cylindrical cavity, and ion outlet are arranged in sequence from left to right; the internal diameter of the cavity is 8 mm.

[0025] The beam adjustment zone, composed of a VUV lamp and a convex lens, adjusts the beam diameter according to the size of the ion outlet; the adjusted beam diameter is 5mm.

[0026] A sample inlet is provided on the side of the sealed cylindrical cavity near the convex lens; the inlet diameter is 5 mm.

[0027] Inside the sealed cylindrical cavity, near the left side of the convex lens, there is at least one quadrupole electrode consisting of two pairs of cylindrical electrodes A, with the axis of the quadrupole electrode coaxial with the axis of the cavity; serving as the focusing area for the ionization reaction; the quadrupole has a diameter of 6 mm and a length of 15 mm;

[0028] Inside the sealed cylindrical cavity, near the ion outlet, there is at least one quadrupole electrode consisting of two pairs of cylindrical electrodes B, with the axis of the quadrupole electrode coaxial with the axis of the cavity; serving as the ion transport region; the quadrupole has a diameter of 8 mm and a length of 10 mm.

[0029] An exhaust gas outlet is provided on the side wall of a sealed cylindrical cavity between cylindrical electrode A and cylindrical electrode B;

[0030] An ion extraction electrode is provided at the right end of the sealed cylindrical cavity;

[0031] The ionization source, with cylindrical electrodes A and B positioned close to the inner wall of a sealed cylindrical cavity, ensures that the sample is ionized and bound in the ionization reaction focusing region and bound in the ion transport region. The diameter of the internal cavity of the quadrupole electrode surrounded by cylindrical electrode A is smaller than the diameter of the internal cavity of the quadrupole electrode surrounded by cylindrical electrode B. The amplitude of the radio frequency power supply applied to cylindrical electrode A is smaller than the amplitude of the radio frequency power supply applied to cylindrical electrode B. The frequency of the radio frequency power supply applied to cylindrical electrode A is smaller than the frequency of the radio frequency power supply applied to cylindrical electrode B. The amplitude of the radio frequency power supply applied to cylindrical electrode A is 700 V; the amplitude of the voltage applied to cylindrical electrode B is 400 V; the frequency of the radio frequency power supply applied to cylindrical electrode A is 500 kHz; and the frequency of the radio frequency power supply applied to cylindrical electrode B is 1.5 MHz.

[0032] In the ionization source, radio frequency voltage and DC voltage U1 with opposite phases are applied to two pairs of cylindrical electrodes in the ionization reaction focusing region; radio frequency voltage and DC voltage U2 with opposite phases are applied to two pairs of cylindrical electrodes in the ion transport region; and DC voltage U3 is applied to the ion extraction electrode. During positive ion detection, the potentials of DC voltages U1, U2, and U3 gradually decrease; during negative ion detection, the potentials of DC voltages U1, U2, and U3 gradually increase.

[0033] The application of the ionization source in mass spectrometry or ion mobility spectrometry, when used in conjunction with mass spectrometry, can reduce the focal size of ions and improve ion transmission efficiency and detection sensitivity when passing through sampling micropores.

[0034] This invention utilizes VUV light for efficient ionization of samples. The radio frequency power supply has a frequency of 50Hz, a sinusoidal voltage waveform, and a peak voltage of 500V; the DC power supply also has a voltage of 500V. The distance between the first and second annular electrodes is 2mm, and the distance between the second and third annular electrodes is 10mm. The first annular electrode is connected to the radio frequency power supply via the introduction of the third annular electrode to reduce the start-up discharge power. See the detailed device description below. Figure 1 The sample to be tested is ionized in the ionization region on the power supply side under the action of carrier gas, and enters the detection equipment such as ion mobility spectrometer through ion outlet 10.

[0035] The ionization source described above is coupled with an ion trap mass spectrometer as the ionization source for the ion trap mass spectrometer, and its structure is as follows: Figure 2 As shown. This instrument mainly consists of the following parts: a cylindrical cavity 1, a VUV lamp 2, a sample inlet 3, a tail gas outlet 4, a near-ion outlet 5, a cylindrical electrode A 6, a cylindrical electrode B 7, a convex lens 8, an ionization reaction focusing region 9, an ion transport region 10, and an ion extraction electrode 11. The sample detection process is as follows: the sample is ionized under the action of photons emitted by the VUV lamp 2, undergoes a full reaction in the ionization reaction focusing region 9, and is efficiently transported in the ion transport region 10; under the action of the ion extraction electrode 11, it enters the ion trap mass spectrometer 13 through the pulse sample introduction interface 12 for detection.

Claims

1. A space-focused VUV ionization source, characterized in that: It includes a hollow, sealed cylindrical cavity (1), with a VUV lamp (2) and an ion outlet (5) respectively at both ends of the sealed cylindrical cavity; the light outlet of the VUV lamp (2) faces the inside of the cavity, and a convex lens (8) is provided at the light outlet of the VUV lamp (2). The emitted light of the VUV lamp is transmitted along the axis of the cavity inside the cavity after passing through the convex lens. The VUV lamp (2), the convex lens (8), the cylindrical cavity (1) and the ion outlet (5) are arranged from left to right. The beam adjustment area, composed of VUV lamp (2) and convex lens (8), adjusts the beam diameter according to the size of ion outlet (5); A sample inlet (3) is provided on one side of the sealed cylindrical cavity (1) near the convex lens (8); Inside the sealed cylindrical cavity (1), near the left side of the convex lens (8), there is at least one quadrupole electrode composed of two pairs of cylindrical electrodes A (6), with the axis of the quadrupole electrode coaxial with the axis of the cavity (1); serving as the focusing area (9) for the ionization reaction. Inside the sealed cylindrical cavity (1), near the ion outlet (5), there is at least one quadrupole electrode consisting of two pairs of cylindrical electrodes B (7), with the axis of the quadrupole electrode coaxial with the axis of the cavity (1); serving as the ion transport region (10). An exhaust gas outlet (4) is provided on the side wall of a sealed cylindrical cavity (1) between cylindrical electrode A (6) and cylindrical electrode B (7). An ion extraction electrode (11) is provided at the right end of the sealed cylindrical cavity (1).

2. The ionization source according to claim 1, characterized in that: Cylindrical electrode A (6) and cylindrical electrode B (7) are positioned close to the inner wall of the sealed cylindrical cavity (1) to ensure that the sample is ionized and bound in the ionization reaction focusing area (9) and bound in the ion transport area (10). The diameter of the cavity inside the quadrupole electrode surrounded by cylindrical electrode A (6) is smaller than the diameter of the cavity inside the quadrupole electrode surrounded by cylindrical electrode B (7); the amplitude of the radio frequency power applied to cylindrical electrode A (6) is smaller than the amplitude of the radio frequency power applied to cylindrical electrode B (7); the frequency of the radio frequency power applied to cylindrical electrode A (6) is smaller than the frequency of the radio frequency power applied to cylindrical electrode B (7).

3. The ionization source according to claim 1 or 2, characterized in that: Radio frequency voltage and DC voltage U1 with opposite phases are applied to the two pairs of cylindrical electrodes in the ionization reaction focusing region (9); Radio frequency voltage and DC voltage U2 with opposite phases are applied to the two pairs of cylindrical electrodes in the ion transport region (10); A DC voltage U3 is applied to the ion extraction electrode (8); During positive ion detection, the potentials of DC voltages U1, U2, and U3 gradually decrease; during negative ion detection, the potentials of DC voltages U1, U2, and U3 gradually increase.

4. The application of any one of the ionization sources described in claims 1-3 in mass spectrometry or ion mobility spectrometry, characterized in that: When used in conjunction with mass spectrometry or ion mobility spectrometry, this ionization source can reduce the focal size of ions and improve ion transmission efficiency and detection sensitivity when passing through the sampling micropore.

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