CN104241077B - Normal pressure micro-glow discharge maldi mass spectrometer ion gun of magnetically confined and mass spectrometer - Google Patents

Abstract

The invention discloses a magnetic field-confined atmospheric pressure micro-glow discharge desorption mass spectrometry ion source, which includes an ion source body for generating normal-pressure micro-glow discharge, and a uniform intensity for providing confined micro-glow discharge plasma and sample ions The Helmholtz coil of the magnetic field and the ring electrode used to generate an electrostatic field to assist in focusing charged particles; the ion source body is in the magnetic field generated by the Helmholtz coil, and the ion flow generated by the ion source body passes through the electric field generated by the ring electrode. The invention also discloses a mass spectrometer composed of a magnetic field-confined microglow discharge desorption mass spectrometer ion source. The invention has the advantages of low energy consumption, small appearance, simple structure, easy operation, little influence on the outside world, high signal enhancement, no need for sample pretreatment, rapid analysis, non-invasive analysis, clean and pollution-free.

Description

Atmospheric pressure microglow discharge desorption mass spectrometry ion source and mass spectrometer with magnetic field confinement

technical field

The invention relates to the technical field of detection, in particular to a magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source and a mass spectrometer analyzer.

Background technique

Mass spectrometry is a method of mass spectrometry by measuring the mass-to-charge ratio of the measured sample ions. As an important detection tool in analytical science, mass spectrometer has the advantages of high sensitivity, fast analysis speed, good selectivity, and can be used in chemometrics. It is widely used in chemistry, chemical industry, materials, environment, geology, energy, medicine, Criminal investigation, life science, sports medicine and other fields, and it plays a huge role in the qualitative and quantitative analysis of trace analytes. For a long time, people have been committed to improving the analytical performance of mass spectrometers, and the improvement of this performance mainly starts with optimizing the structure of mass spectrometers. The structure of a mass spectrometer mainly includes an ion source, a mass analyzer, a detector and a vacuum system. In order to improve the sensitivity of mass spectrometry and meet different analysis purposes, various mass analyzers have been developed, including ion traps, quadrupoles, orbitraps, and time-of-flight mass analyzers. In addition, the ionization efficiency of the sample and the transmission efficiency of ions between the ion source and the inlet of the mass spectrometer are the key factors that dominate the performance of mass spectrometry. In order to improve the ionization efficiency, there are commercialized electrospray ionization (Electrospray ionization, ESI), atmospheric pressure chemical ionization (Atmospheric pressure chemical ionization, APCI), matrix assisted laser desorption ionization (Matrix assisted laser desorption ionization, MALDI) Etc. through electrospray, high-pressure gas discharge, matrix, laser and other methods to improve the efficiency of energy transfer to meet the ionization of samples with different properties. Meanwhile, proton transfer reaction mass spectrometry (PTR-MS) and selective ionization drift tube mass spectrometry (SIFT-MS) use electrostatic fields to extract and focus charged particles, thereby improving the efficiency of ion transmission between the ion source and the mass spectrometer inlet. It has also been reported that magnetic fields are used to replace electrostatic fields to achieve focusing on target ions, but so far magnetic fields have only been used to confine high-energy electrons and ions in very pressure environments, and the magnetic field strength is often as high as several hundred to several thousand Gauss ( Gs), which may affect the normal operation of other components in the mass spectrometer.

In recent years, atmospheric pressure ionization technology has received widespread attention in the fields of instrumental analysis, food analysis, organic chemistry, polymers, biology, etc. . Atmospheric open source mass spectrometry ionization technology (Ambient mass spectrometry) started from the desorption electrospray ionization technology (Desorption Electrospray Ionization, DESI) reported by R.G. Cooks et al. in 2004, and the direct real-time analysis ionization technology (Direct Analysis in Real Time, DART). Other atmospheric pressure ion sources that have appeared in recent years include Desorption Atmospheric Pressure Chemical Ionization (DAPCI), Dielectric Barrier Discharge Ionization (DBDI), Flowing Atmospheric Pressure Afterglow (Flowing Atmospheric Pressure Afterglow, FAPA), Desorption Atmospheric Pressure Photoionization (DAPPI), Probe Electrospray Ionization (PESI), Microwave-Induced Plasma Desorption Ionization (MIPDI), etc. The working principle of this kind of atmospheric pressure ion source mainly includes two processes of desorption and ionization. The general process of generating ions includes: a certain light source (infrared, ultraviolet), or a certain energy source (electric field, thermal energy) acts on a certain carrier (gas, reagent) to generate a charged body with a certain energy, which acts on the surface of the sample. Molecules on the sample surface are desorbed concurrently or subsequently ionized. These technologies play an important role in various fields, but in the normal pressure environment, the sample ions are susceptible to external interference, which greatly reduces the ion transmission efficiency, which greatly limits the sensitivity of normal pressure mass spectrometry. At the same time, this type of atmospheric pressure ion source requires a high energy source, high heat complicates the mass spectrogram, the structure of the ion source is complicated, and the production cost is high, so further improvement and improvement are needed. Therefore, it is of great significance to develop and provide a normal-pressure ionization technology with a simple structure, low energy consumption, and soft ionization that ensures high ion transmission efficiency.

Contents of the invention

The present invention aims to provide an atmospheric pressure microglow discharge desorption mass spectrometry ion source based on a magnetic field confined atmospheric pressure microglow discharge plasma, and an atmospheric pressure desorption mass spectrometer composed of it to solve the problem of existing atmospheric pressure mass spectrometry. Problems with ionization technology.

In order to achieve the above object, the present invention is achieved by adopting the following technical solutions:

The magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source provided by the present invention mainly includes a Helmholtz coil that provides a magnetic field to confine micro plasma and other charged particles, and an atmospheric pressure microglow discharge plasma ion source 1. An annular electrode that provides an electrostatic field to assist in focusing charged particles, the ion source body is placed in a magnetic field generated by a Helmholtz coil, and the ion flow generated by the ion source body passes through the electric field generated by the annular electrode.

In the above-mentioned technical solution of the present invention, the composition of the normal pressure micro-glow discharge plasma ion source includes a micro-plasma generation cavity processed on an insulating material base member, and a micro-plasma generation cavity fixedly arranged on the wall surface of the micro-plasma generation cavity A pair of electrodes used to break down the working gas to generate discharge and a gas path conversion joint fixed at the inlet of the micro-plasma generation chamber for connecting the working gas introduction system, the electrodes are connected to a DC stabilized power supply of 80-3000V. The electrode is preferably connected to a DC stabilized power supply whose voltage can be adjusted in the range of 200-500V; the inlet of the micro-plasma generation chamber is preferably connected to a working gas introduction system designed with a gas flow controller through a gas path conversion joint to ensure The flow rate of the working gas is controlled in the range of 0.5L/min to 2.5L/min. If the flow rate of the working gas exceeds this range (less than 0.5L/min or higher than 2.5L/min), the ion source provided by the present invention can still work normally. The working voltage applied to the electrodes is generally in the range of 200-500V, and the total power is less than 4W.

In the above technical solution of the present invention, the micro-plasma generating chamber is preferably a lumen with a rectangular section, and either the height or the width of the section of the lumen is less than 1 mm. The electrode is preferably a sheet electrode. Preferably, the two electrodes constituting the electrode pair are fixedly arranged face to face on the two walls of the micro-plasma generating chamber, where the distance between the two walls is not greater than 1 mm. The wall surface in the micro-plasma generating chamber used to fix the plate-shaped electrode preferably has a dimension perpendicular to the lumen of not less than 1 mm. The electrodes are preferably fixed in the micro-plasma generating chamber at a position less than or equal to 10 millimeters from the ejection outlet, and the distance usually adopted is 1-3 millimeters.

In the above technical solution of the present invention, the material of the electrode is a conductive metal material such as platinum, copper, silver, preferably platinum or brass with a purity of not less than 99.99%; the material of the base member is an insulating material For example, aluminum oxide, polytetrafluoroethylene, quartz or bakelite; preferably aluminum oxide, bakelite, quartz, etc. with a purity of not less than 96%.

In the above technical solution of the present invention, the Helmholtz coil for providing the magnetic field comprises an insulator support and two coaxial and parallel series coils. The coil is wound on an insulating support, the two coils are connected in series, the number of winding turns and the radius are the same, and the distance between the coils is equal to the radius of the coils. The current in the two coils is in the same direction, and is provided by a low-voltage DC power supply that can provide current in the range of 0-5A. The magnetic field provided by the coil is proportional to the current, and the magnetic field is adjustable according to the coil current, and the range preferably includes 10-50Gs. The diameter of each coil is not smaller than the width of the base body of the micro-plasma generating chamber.

In the above technical solution of the present invention, the material of the insulator bracket is ceramics, aluminum oxide, polytetrafluoroethylene, quartz or bakelite; the material of the coil wire is a conductive metal material such as copper, aluminum, silver .

In the above technical solution of the present invention, the inner and outer diameters and thickness of the annular electrode that provides an electrostatic field to assist in focusing charged particles are not limited, and the inner diameter should not be smaller than the plasma outlet of the atmospheric pressure microglow discharge desorption mass spectrometry ion source width. The electric potential of the ring electrode is provided by a high-voltage static power source whose voltage is adjustable in the range of -1500V-1500V, and the adjustable voltage range of the static power source preferably includes -400V-400V.

In the above technical solution of the present invention, the material of the annular electrode that provides an electrostatic field to assist in focusing the charged particles is a conductive material such as copper, steel, iron, aluminum, platinum, and silver.

The mass spectrometer is composed of the above-mentioned atmospheric microglow discharge desorption mass spectrometry ion source confined by the magnetic field. Provide a DC stabilized power supply with a voltage range of 80-3000V, a mass spectrometer and a mass spectrometer data processing system. The supply voltage range includes 80-3000V DC stabilized power supply with positive and negative poles connected to form a circuit, the outlet of the micro-plasma generation chamber and the plasma gas inlet of the mass spectrometer face the sample between them, and the mass spectrometer Connect with the mass spectrometry data processing system.

In the above mass spectrometer of the present invention, the normal pressure microglow discharge desorption mass spectrometry ion source is preferably installed on a vertical rotary table that can rotate in the range of 0 to 90° in the vertical plane, and the rotary table is installed on a 3D On the translation platform, in order to adjust the relative position between the outlet of the micro plasma generation chamber of the atmospheric desorption mass spectrometry ion source and the sample and the plasma gas inlet of the mass spectrometer, so that the plasma gas ejected from the outlet of the plasma generation chamber Align the sample to be tested and the plasma gas inlet of the mass spectrometer so that the plasma generation chamber is on the center line of the Helmholtz and ring electrodes. The Helmholtz coil is arranged between the sample inlet of the mass spectrometer and the ion source of atmospheric desorption mass spectrometry or includes the ion source of atmospheric desorption mass spectrometry. The ring electrode is placed outside the plasma outlet of the atmospheric desorption mass spectrometry ion source, the direct distance between the two is preferably less than 10mm, and the ring electrode should be coaxial and parallel to the Helmholtz coil.

In the mass spectrometer of the present invention, the working gas introduction system is preferably provided with a gas flow controller to ensure that the flow rate of the working gas is controlled within the range of 0.5L/min-2.5L/min.

In the above-mentioned mass spectrometer of the present invention, the sample introduction system includes a sampling pump, a sampling needle and a capillary, the injection speed range of the sampling pump preferably includes 0.1 μL/min～5 μL/min, and the sampling needle The capacity is preferably greater than 5μL. The capillary is used to connect the sampling needle and the working gas path, and its material is PEEK.

In the above-mentioned mass spectrometer of the present invention, the DC power supply is preferably a DC stabilized power supply whose voltage can be adjusted in the range of 200-500V, and the current applied to the electrodes to ionize the working gas is controlled in the range of 2-20mA for The total power of ionization is generally less than 4W, so that the temperature of the plasma gas ejected from the ejection port of the micro-plasma generation chamber is controlled within the range of 20-100°C.

The working gas applicable to the present invention may be helium, argon, nitrogen, etc., preferably helium or argon. The gas source of the working gas is generally steel cylinder gas, and the flow rate of the working gas can be controlled by a mass flow controller placed on the pipeline between the steel cylinder and the ion source. The flow rate of the working gas is generally 0.5-2.5L/min.

The sample is subjected to mass spectrometry analysis by using the magnetic field-confined atmospheric microglow discharge desorption mass spectrometer provided by the present invention, and the form of the sample can be solid, liquid or gaseous. For solid and liquid samples, the sample can be placed on the carrier between the outlet of the ion source micro-plasma generation chamber and the plasma gas inlet of the mass spectrometer, and the plasma gas ejected from the outlet of the micro-plasma generation chamber To the sample to be measured, the molecules on the surface of the sample are desorbed and ionized under the action of the plasma gas. For liquid and gaseous samples, an appropriate amount of sample can also be drawn with a sampling needle, and the flow rate is controlled by a syringe pump to inject the sample into the plasma working gas path through a capillary, and then sent into the plasma generation chamber together with the working gas. After the sample is ionized, it enters the mass spectrometer from the plasma gas inlet of the mass spectrometer for sample mass spectrometry analysis.

The atmospheric pressure microglow discharge desorption mass spectrometer provided by the magnetic field confinement provided by the present invention is used to carry out mass spectrometry analysis on the sample. Under different working gas flow rates and the current intensity applied to the electrode breakdown working gas, the ionic strength and type of the obtained mass spectrogram There will be a difference. This is because at different current intensities, the content of active components in the plasma, that is, the metastable atoms, is different, which will affect the ionization efficiency of the sample; and at different working gas flow rates, the plasma gas The temperature of the plasma is different, and the plasma linear velocity is also different, so the main desorption mechanism (thermal desorption, momentum desorption) of the sample will change, which will further affect the subsequent ionization process. Therefore, the user can adjust the current intensity and gas flow rate of the ion source according to the actual situation to achieve the best test effect.

The atmospheric pressure microglow discharge desorption mass spectrometer provided by the present invention is used to carry out mass spectrometry analysis on the sample. In the absence of a magnetic field and an electrostatic field, in the positive ion and negative ion scanning modes of the mass spectrometer, the obtained to-be The mass spectra of the tested samples are also different. This is because when the ion source of the present invention is used to ionize samples, the formation mechanisms of positive and negative ions are different. The formation process of positive ions includes Penning ionization, proton transfer, and charge transfer, in which the proton transfer reaction will form [M+H] ⁺ ions, and the protons are mainly provided by water clusters, which are mainly composed of metastable atoms ( He ^m ) and atmospheric moisture through Penning ionization. In order to further verify the ionization mechanism, the emission spectrum of the plasma in the range of 200-1100nm was analyzed (Figure 4, Figure 5). The existence of N ₂ , NO, and OI peaks proved the existence of the charge transfer process, and the OH peak assisted The existence of the proton transfer process was confirmed, and ArI and HeI provided a theoretical basis for Penning ionization. Under the positive ion mode, the reaction that takes place under the guidance of the plasma (taking helium as an example) ejected by the ion source provided by the present invention is as follows:

He ^* +nH ₂ O→He+(H ₂ O) _n-1 H ⁺ +OH ^-

He ^* +M → He+M ⁺ +e ^-

(H ₂ O) _n H ⁺ +M→M(H ₂ O) _n-1 H ⁺ +H ₂ O

In the negative ion mode, O ₂ ^- is the main active reagent. O ₂ ^- will absorb protons on the molecules of the sample to be tested through the deprotonation mechanism to generate [MH] ^- ions, and will generate M ^- through the mechanism of electron transfer and electron capture. ion. M ^- ions are formed as follows:

The magnetic field confinement provided by the present invention is based on the atmospheric pressure micro-glow discharge plasma desorption mass spectrometer, if the interference of external components is not considered, the positive and negative charged particles in the micro-plasma gas flow ejected from the micro-plasma generation chamber Under the action of the magnetic field provided by the Helmholtz coil, it will perform a helical movement around the central axis of the coil, as shown in FIG. 6 . Lorenz radius of the motion Helical lead The velocity v of the charged particles is approximately equal to the linear velocity of the plasma flow.

The magnetic field confinement provided by the present invention is based on the normal pressure microglow discharge plasma desorption mass spectrometer. When the low magnetic field strength is 0-50Gs, the mass spectrum signal increases with the increase of the magnetic field strength, and when the magnetic field strength is higher than 40Gs, the mass spectrometry signal increases slowly, as shown in Figure 7. If a magnetic field as high as hundreds of Gs is used, the enhancement of the mass spectrometer signal is not as good as the signal magnification of 50Gs. This is because the strong magnetic field may over-focus the charged particles, the frequency of ion-ion/electron collisions increases, and the movement of target ions Trajectories are disrupted by collisions or direct charge quenching, resulting in a reduction in the mass spectrometric signal.

In the magnetic field confinement based on atmospheric pressure microglow discharge plasma desorption mass spectrometer provided by the present invention, the electrostatic field provided by the ring electrode will focus on the particles with the same charge in the plasma flow passing through the center of the electrode, and at the same time discrete and Annihilation of oppositely charged particles assists the magnetic field in confining the target ions and reduces charge loss from ion-ion/electron collisions. When a positive potential is applied to the ring electrode, under a magnetic field of 50Gs, the electrostatic field does not affect the enhancement factor of the mass spectrometer signal, while when a negative potential is applied to the ring electrode, under a magnetic field of 50Gs, the mass spectrometer signal is enhanced compared to that without a magnetic field The multiple increases with the increase of the electrostatic field between 0 and -600V, and reaches the maximum value at -600V (Figure 8). However, if the potential is too strong, it will annihilate the target ions with the opposite charge, resulting in a decrease in the mass spectrometry signal (Figure 9). While ensuring the mass spectrometry signal intensity, an electrostatic field of -100V ~ -400V combined with a 50Gs magnetic field can obtain better mass spectrometry signals. Enhancement.

Compared with the existing mass spectrometry ion source, the magnetic field-confined atmospheric pressure microglow discharge plasma-based atmospheric pressure open-source desorption mass spectrometry ion source has the following outstanding technical effects and advantages:

1. The magnetic field-confined atmospheric pressure desorption mass spectrometry ion source based on atmospheric microglow discharge plasma provided by the present invention can be directly connected to a mass spectrometer with an atmospheric pressure interface to realize the detection of solid, liquid, and gas samples , and easy to disassemble.

2. The atmospheric pressure desorption mass spectrometry ion source based on the atmospheric pressure micro-glow discharge plasma provided by the present invention is confined by the magnetic field. The confinement of the magnetic field to the charged particles under the atmospheric pressure has been tested, and the mass spectrometry inlet and the atmospheric pressure ion source have been improved. The ion transfer efficiency between.

3. The ion source provided by the present invention has a simple structure, Helmholtz coils and electrode materials are readily available, easy to manufacture, and the manufacturing cost is much lower than other existing ion sources.

4. Maintain the power of the DC power supply of the atmospheric pressure desorption mass spectrometry ion source based on the atmospheric pressure microglow discharge plasma provided by the present invention not greater than 4W, the voltage is generally not greater than 500V, and the energy consumption is lower than other ion sources.

5. The mass spectrometer equipped with the ion source provided by the present invention is used to detect the sample. Under a weak magnetic field of tens of Gs, the signal enhancement degree of the sample can reach more than ten times, and the weak magnetic field will affect other components in the mass spectrometer. And the impact of the surrounding environment is small.

6. The mass spectrometer equipped with the ion source provided by the present invention is used to detect the sample, and the plasma plume is clearly visible, which is convenient for adjusting and calibrating the relative position of the sample and the ion source; the plasma plume has low energy and low temperature, and does not It will cause burns on the surface of the sample, so this inspection method is a non-destructive analysis method.

7. The mass spectrometer equipped with the ion source provided by the present invention is used to detect the sample without pretreatment of the sample, the operation is simple and the qualitative analysis takes less time (less than 5s).

8. The sample is detected by a mass spectrometer equipped with the ion source provided by the present invention, which has a sensitive response to trace samples and a fast response, and high-throughput online analysis can be realized.

9. The mass spectrometer equipped with the ion source provided by the present invention is used to detect the sample without the assistance of spray reagents and will not pollute the environment.

10. The ion source provided by the present invention has a compact appearance, and the Helmholtz coil and the ring electrode are easy to disassemble, which is suitable for the development and application of subsequent portable mass spectrometers.

The advantages of the magnetic field-confined atmospheric pressure desorption mass spectrometry ion source based on atmospheric pressure microglow discharge plasma can be summarized as follows: low energy consumption, small size, simple structure, easy operation, small influence on the outside world, high signal The degree of enhancement is large, no sample pretreatment is required, the analysis is rapid, non-invasive analysis can be achieved, clean and pollution-free, etc.

Description of drawings

Accompanying drawing 1 is the schematic diagram of the atmospheric pressure micro-glow discharge desorption mass spectrometry ion source confined by the magnetic field of the present invention.

Accompanying drawing 2-1 is the top view structural representation of an embodiment of the atmospheric pressure microglow discharge desorption mass spectrometry ion source of the present invention;

Accompanying drawing 2-2 is a left view structural diagram of accompanying drawing 2-1;

Accompanying drawing 2-3 is a schematic view of the internal structure of the normal-pressure microglow discharge desorption mass spectrometry ion source shown in Fig. 2-1.

Accompanying drawing 3 is equipped with the ion source of the present invention and is equipped with the schematic diagram of the way of detection and analysis of solid and liquid samples by the atmospheric pressure microglow discharge desorption mass spectrometer.

Accompanying drawing 4 is the emission spectrogram of atmospheric pressure microglow discharge argon plasma.

Accompanying drawing 5 is the emission spectrogram of normal pressure microglow discharge helium plasma.

Accompanying drawing 6 is the schematic diagram of the helical movement of charged particles in a uniform magnetic field.

Accompanying drawing 7 is a schematic diagram of the variation of the intensity of the most common m/z279 ion in the background image of the mass spectrum with the magnetic field of the Helmholtz coil.

Accompanying drawing 8 is equipped with the mass spectrometer total ion flow of the mass spectrometry analyzer of the atmospheric pressure microglow discharge plasma desorption ion source of the magnetic field confinement of the present invention, and the change graph of the increase factor of the ring electrode potential under the external magnetic field of 50Gs.

Accompanying drawing 9 is equipped with the mass spectrometer total ion current of the mass spectrometer equipped with the atmospheric pressure micro-glow discharge plasma desorption ion source confined by the magnetic field of the present invention at 50Gs and 0Gs respectively with the change diagram of the potential of the ring electrode.

Figure 10 is a mass spectrogram obtained by detecting and analyzing the methanol:water (1:1) solution of paracetamol with a mass spectrometer equipped with an atmospheric microglow discharge plasma desorption ion source of the present invention.

Accompanying drawing 11 is the quantitative curve and the corresponding mass spectrogram obtained by semi-quantitative analysis of phenacetin solution with the mass spectrometer equipped with the atmospheric pressure microglow discharge plasma desorption ion source of the present invention.

Accompanying drawing 12-1 is equipped with the mass spectrometer of the atmospheric pressure microglow discharge plasma desorption ion source of the magnetic field confinement of the present invention and analyzes the mass spectrogram obtained by analyzing toluene under the situation of not adding an external magnetic field;

Accompanying drawing 12-2 is when adding 50Gs external magnetic field, analyze the mass spectrogram obtained by toluene;

Accompanying drawing 12-3 is the change diagram of the [M+CH ₃ +H] ⁺ ion intensity of toluene with the magnetic field of the Helmholtz coil.

Accompanying drawing 13-1 is the mass spectrogram that is equipped with the atmospheric pressure micro-glow discharge plasma desorption ion source of magnetic field confinement of the present invention to analyze the mass spectrogram obtained from cigarette filtrate under the condition of not adding an external magnetic field;

Accompanying drawing 13-2 is the mass spectrogram obtained by analyzing the cigarette filtrate when adding a 50Gs external magnetic field.

In the figure: 1- ion source body; 2- Helmholtz coil; 3- ring electrode; 4- ion source base part; 5- electrode; 8-air inlet of gas path conversion joint; 9-micro plasma generation chamber; 10-micro plasma plume; 11-mass spectrometer plasma inlet; 12-sample ion; 13-sample; 14-sample carrier; .

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings.

The magnetic field confinement based on atmospheric pressure microglow discharge desorption mass spectrometry ion source disclosed by the present invention, as shown in Figure 1, the structure mainly includes an ion source body 1 for generating atmospheric pressure microglow discharge, providing confined microglow discharge plasma and A Helmholtz coil 2 with a uniform magnetic field for sample ions, and a ring electrode 3 that generates an electrostatic field to assist in focusing charged particles. The current of the Helmholtz coil 2 is provided by a low-voltage DC power supply that can provide current in the range of 0-5A. A feasible size of the Helmholtz coil 2 is 160 mm inner diameter, 220 mm outer diameter, and the center-to-center distance between the two coils is 80 mm. As shown in Figure 3, the Helmholtz coil 2 is 5 mm away from the mass spectrometer inlet, the atmospheric pressure microglow discharge ion source body 1 is placed in the Helmholtz coil 2, and the mass spectrometer plasma inlet 11 is connected to the ion source. The source bodies 1 are all located on the centerline of the Helmholtz coil 2 . The ring electrode 3 is 5 mm away from the sub-source outlet, and the center line of the ring electrode 3 coincides with the center line of the Helmholtz coil 2 .

As shown in Figure 2-1, Figure 2-2 and Figure 2-3, the composition of the ion source body 1 mainly includes: a micro-plasma generation cavity 9 processed on an ion source base part 4 made of ceramic material, Face-to-face inlaid on the upper and lower walls of the micro-plasma generation chamber 9, a pair of platinum sheet electrodes 5 for breaking down the working gas to generate discharge, and fixed at the inlet end of the micro-plasma generation chamber for connecting the working gas introduction system The gas path conversion joint 6, the sheet electrode 5 is connected to the positive and negative poles of the DC power supply that can be adjusted between 80 ~ 3000V to form a circuit, and the two sheet electrodes 5 are arranged at a distance of about 7 from the outlet of the micro plasma generation chamber. 1 mm, to reduce the interference of the external air flow on the discharge, and ensure that the plasma plume ejected from the ejection port 7 of the micro-plasma generation chamber can extend to the outside of the micro-plasma generation chamber, so as to calibrate the relative relationship between the sample and the ion source Location. The size of the flow channel of the plasma generation chamber is: 26.6 mm in length, 2.4 mm in width, and 0.7 mm in height. The gas circuit switching head 6 is sealed and connected with the inlet of the micro plasma generation chamber with high temperature resistant epoxy resin glue, so as to ensure the airtightness of the gas circuit inside the micro plasma generation chamber 9 . When using this ion source to detect samples, the working gas (argon or helium) enters the micro-plasma generation chamber 9 from the air inlet 8 at the end of the gas circuit conversion head 6, and is struck when it flows through the two sheet electrodes 2. Atmospheric pressure micro-glow discharge occurs, thereby generating the micro-plasma necessary for ionizing the sample.

As shown in Figure 3, the analyzer disclosed by the present invention is composed of a magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source, and its composition mainly includes a working gas introduction system, a sample introduction system, and an atmospheric pressure microglow discharge desorption mass spectrometry ion source. Ion source, DC power supply whose voltage can be adjusted in the range of 80-3000V, mass spectrometer and mass spectrometry data processing system. Atmospheric pressure microglow discharge desorption mass spectrometry ion source is clamped and fixed on a vertical rotating platform that can rotate within the range of 0-90° in the vertical direction, and the vertical rotating platform is placed on a 3-dimensional (3D) translation platform to make the plasma The generating cavity 9 is located on the center line of the Helmholtz coil 2 and the ring electrode 3 . The working gas introduction system is a helium or argon cylinder equipped with a mass flow meter to ensure that the flow rate of helium or argon as a working gas in the micro-plasma generation chamber is controlled within the range of 0.5-2.5L/min. The sample introduction system includes a sampling pump, a sampling needle and a capillary tube, the sampling speed of the sampling pump is adjustable in the range of 0.1 μL/min to 5 μL/min, the capacity of the sampling needle is 5 ml, and the capillary tube is used to connect the sampling The material of needle and working air path is PEEK. Atmospheric pressure micro-glow discharge desorption mass spectrometry ion source is connected to the working gas introduction system through its gas path conversion joint 6, and the two sheet electrodes of the atmospheric pressure micro-glow discharge desorption mass spectrometry ion source are connected to the direct current whose voltage can be adjusted in the range of 80-3000V. The positive and negative poles of the power supply are connected to form a circuit, and the plasma ejection port 7 of the plasma generation chamber of the atmospheric pressure microglow discharge desorption mass spectrometry ion source is placed opposite to the plasma inlet port of the mass spectrometer, and the sample A10, The sample B13 is placed on the sample carrier 14, and the mass spectrometer is connected with the mass spectrometry data processing system.

When adopting the mass spectrometer provided by the present invention to analyze solid and liquid samples, the solid (or liquid) sample 13 is placed on the carrier 14 between the ion source plasma ejection outlet and the mass spectrometer plasma gas inlet 11, so that from The plasma gas ejected from the ejection port of the ion source is aimed at the sample to be tested, so that the molecules on the surface of the sample are desorbed and ionized under the action of the plasma gas. The carrier of block, paste and liquid samples can be ordinary glass slides, filter paper, ceramic sheets, stainless steel sheets, etc. Liquid samples can also be placed directly in the container, and powder samples need to be fixed on the above-mentioned surface with double-sided adhesive tape. Carrier and then detected to prevent the powder sample from entering the mass spectrometer with the airflow and blocking the inlet of the mass spectrometer. The horizontal distance between the sample and the inlet of the mass spectrometer is 5-20 mm, and the vertical distance is 2-10 mm. The horizontal distance between the ion source and the sample is usually 1-5 mm, the vertical distance is 1-5 mm, and the horizontal distance between the ion source and the entrance of the mass spectrometer is usually 10-20 mm. The angle between the plasma gas beam ejected from the ion source and the sample surface can be flexibly adjusted within the range of 0° to 90° to ensure the best mass spectrum signal in the actual detection process.

The mass spectrometer provided by the present invention is used to analyze liquid or gaseous sample gas samples, and an appropriate amount of samples can also be extracted with a sampling needle, and the flow rate is controlled by a syringe pump to inject the sample into the plasma working gas circuit through a capillary tube and then sent together with the working gas. Plasma chamber. After the sample is ionized, it enters the mass spectrometer from the plasma gas inlet of the mass spectrometer for sample mass spectrometry analysis.

The mass spectrometer provided by the invention is used to detect a liquid sample without adding a magnetic field and an electrostatic field, and specifically the paracetamol solution is used as the detection object.

Dissolve pure paracetamol powder in a solvent of methanol:water 50:50 (v:v) to prepare a solution with a paracetamol content of 30 mg/L. Use a pipette gun to pipette 2 μL of the solution and drop it on a glass slide with a small groove, or any other open vessel that can be used to hold the reagent. The container carrying the liquid sample is placed between the outlet of the ion source micro-plasma gas generation chamber and the plasma gas inlet of the mass spectrometer, and the flow rate of helium as the working gas and the current intensity of the breakdown are adjusted to obtain the best mass spectrometer signal. The mass spectrum finally obtained by the above operations is shown in Figure 10, the peak at m/z=303 corresponds to the protonated dimer [2M+H] ⁺ of paracetamol, and the peak at m/z=279 is the plasticizer phthalic acid The protonated molecular ion peak of dibutyl ester, which may be introduced into the detection system when using most experimental equipment containing plasticizers, the peak at m/z=152 is attributed to [M+H] ⁺ of paracetamol peak. The overall peak shape of the paracetamol solution mass spectrogram shown in Figure 10 is clear and easy to identify, with fewer impurity peaks and fragment peaks. Therefore, it has great advantages to use the ion source provided by the present invention for qualitative analysis of liquid samples.

The mass spectrometer provided by the present invention can be used to conduct semi-quantitative analysis on the sample alone without adding a magnetic field or an electrostatic field, and specifically, phenacetin is used as the analysis object.

Dissolve phenacetin powder in pure methanol to form a series of solutions with different concentrations. Add a certain amount of paracetamol as an internal standard in each solution, and ensure that the concentration of paracetamol in each solution is the same. A sample is tested sequentially from low concentration to high concentration. The way of sampling can be to directly put the solution in an open vessel, or drop 5 μL of the sample on the filter paper, and use the ion source provided by the present invention to analyze the sample. Accompanying drawing 11 shows the quantitative curve of phenacetin obtained by argon plasma, the sample injection carrier used is filter paper, the concentration of each point on the linear regression line is the concentration of phenacetin sample, and the intensity corresponding to each point It is the ratio of the peak areas of phenacetin and paracetamol in the mass spectrum ion chromatogram obtained by the sample. Under this setting, the detection range of phenacetin was 10 ⁴ , each sampling point was repeated 8 times, and the RSD corresponding to each point ranged from 10% to 20%. It should be noted that this example is a manual sample injection, so human factors greatly interfere with the accuracy and repeatability of the detection. Introducing an automatic sampling device (such as a peristaltic pump, a mechanical pump, a chromatographic related device) will significantly improve the quantitative performance of the mass spectrometer equipped with the ion source provided by the present invention. has outstanding potential.

Using the mass spectrometer provided by the present invention, the detection signal of the sample can be improved through the confinement of the magnetic field, specifically using toluene as the analysis object:

A certain amount of toluene was extracted with a 5mL sampling needle, and after the air bubbles in the needle tube were exhausted, the sampling needle was connected to the capillary of the Unicom plasma working gas circuit, and the liquid sample was injected into the gas circuit by pushing the sampling needle with a pump. Set the speed of the injection pump to 1 μL/min, the flow rate of the working gas (helium) to 1.2 L/min, and the microglow discharge current to 12 mA. Adjust the current of the Helmholtz coil so that the coil can generate a uniform magnetic field of 0-50Gs, and provide a potential of -100V to the ring electrode. According to the above operation, the mass spectrum of toluene obtained under the magnetic field of 0Gs and 50Gs is shown in Figure 12-1 and 12-2, and the peaks m/z 91, m/z 94, and m/z 108 correspond to [MH] ⁺ of toluene respectively , [M+2H] ⁺ , [M+CH ₃ +H] ⁺ product ion. The mass spectrum signals of the three ions increased by 10, 11, and 15 times from 0Gs to 50Gs. Figure 12-3 shows the variation of the intensity of the peak m/z94 with the magnetic field of the coil. It can be seen that the confinement and focusing effect of the external magnetic field on the ions can significantly enhance the mass spectrum signal of the sample ions.

The mass spectrometer provided by the present invention is used to analyze and detect complex samples in real life, specifically taking cigarettes bought in stores as detection objects. Cut the cigarette paper from the cigarette purchased from the store, take an appropriate amount of shredded tobacco and soak it in 40ml of methanol for 1 hour, and filter the soaking solution to remove solid impurities therein. Inject the filtrate into the plasma working gas path directly by pumping samples, set the pump flow rate to 0.5 μL/min, and other working conditions are the same as when toluene is used as the analysis object. Accompanying drawings 13-1 and 13-2 are the mass spectrograms of the components in the cigarette filtrate obtained when there is no magnetic field and a 50Gs magnetic field respectively, wherein m/z163 is the [M+H] ⁺ peak of nicotine, the main component in the cigarette, and m/z79 is Fragmentation peak of nicotine, m/z 149 is the fragmentation peak of plasticizer in cigarette paper and carrier gas pipeline. Comparing the ordinates of the two figures, it can be seen that the mass spectrum signals of each component in the cigarette filtrate are enhanced to varying degrees under an external magnetic field of 50Gs compared to when no magnetic field is applied, and the intensity of m/z163 increases by about 6 times. m/z79 increases about 10 times.

Certainly, the present invention also can have other various embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes All changes and modifications should belong to the scope of protection of the appended claims of the present invention.

Claims (21)

1. A magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source, characterized in that it comprises an ion source body for producing atmospheric pressure microglow discharge, for providing confined microglow discharge plasma and sample ions A Helmholtz coil with a uniform magnetic field, an annular electrode used to generate an electrostatic field to assist in focusing charged particles; the ion source body is in the magnetic field generated by the Helmholtz coil, and the ion flow generated by the ion source body passes through the ring The electric field generated by the electrodes. 2. the atmospheric pressure micro-glow discharge desorption mass spectrometry ion source of magnetic field confinement according to claim 1, is characterized in that, described ion source body comprises the micro-plasma generation chamber that processes on base piece, is fixed on micro-plasma A pair of electrodes on the wall of the plasma generating chamber used to break down the working gas to generate discharge and a gas path conversion joint fixed at the inlet of the micro plasma generating chamber for connecting the working gas introduction system, the electrodes and the output voltage are between 80 and 3000V Infinitely adjustable DC regulated power supply connection. 3. Atmospheric pressure microglow discharge desorption mass spectrometry ion source according to claim 2, is characterized in that, the section shape of described microplasma generation cavity is the lumen of rectangle, and one of height or width of lumen section is less than The electrode is a sheet electrode, and the two electrodes are respectively fixed on the opposite side walls of the micro-plasma generation chamber with a distance of no more than 1 mm. The dimension in the channel direction is not less than 1 millimeter, and the distance between the electrode and the ejection port of the micro plasma generation chamber is not more than 10 millimeters. 4. The atmospheric microglow discharge desorption mass spectrometry ion source according to claim 2, wherein the electrode is made of a conductive metal material, and the base member is made of an insulating material. 5. the atmospheric pressure micro-glow discharge desorption mass spectrometry ion source of magnetic field confinement according to claim 4, is characterized in that, the material of described electrode is platinum, copper or silver, and the material of described base part is ceramic, trioxide Aluminum, Teflon, Quartz or Bakelite. 6 . The magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source according to claim 2 , wherein the output of the DC stabilized power supply is infinitely adjustable within the range of 200-500V. 7 . 7. The atmospheric pressure microglow discharge desorption mass spectrometry ion source of magnetic field confinement according to claim 1, is characterized in that, described Helmholtz coil is made up of a pair of coaxial parallel and the same series conduction coil of number of turns , the distance between the two coils is equal to the coil radius, and the magnitude and direction of the current in the two coils are the same. 8. The magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source according to claim 7, characterized in that the current of the Helmholtz coil is 0-5A. 9. The magnetic field confined atmospheric microglow discharge desorption mass spectrometry ion source according to claim 1, characterized in that the radius of the Helmholtz coil is not less than the width of the ion source body. 10 . The magnetic field confined atmospheric microglow discharge desorption mass spectrometry ion source according to any one of claims 7 to 9 , wherein the magnetic field generated by the Helmholtz coil is in the range of 10 to 50 Gs. 11 . 11. The atmospheric pressure microglow discharge desorption mass spectrometry ion source of magnetic field confinement according to any one of claims 7 to 9, characterized in that, the core wire material of the lead wire wound with the Helmholtz coil is conductive metal Material, the skeleton supporting the coil is insulating material. 12. the atmospheric pressure microglow discharge desorption mass spectrometry ion source of magnetic field confinement according to claim 11, it is characterized in that, the core wire material of the wire that winds described Helmholtz coil is copper, aluminum or silver, supports The skeleton of the coil is made of ceramics, aluminum oxide, polytetrafluoroethylene, quartz or bakelite. 13. The magnetic field-confined atmospheric microglow discharge desorption mass spectrometry ion source according to claim 1, characterized in that the potential of the ring electrode is provided by an electrostatic source whose output voltage is adjustable in the range of -1500V to 1500V. 14. The magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source according to claim 13, characterized in that the adjustable output voltage range of the electrostatic source is -400V-400V. 15. The magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source according to claim 2, characterized in that the inner diameter of the ring electrode is not less than the width of the ejection port of the microplasma generation chamber. 16 . The magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source according to claim 15 , wherein the material of the ring electrode is conductive material. 17. The magnetic field-confined atmospheric pressure microglow discharge desorption mass spectrometry ion source according to claim 1, wherein the material of the ring electrode is copper, steel, iron, aluminum, platinum or silver. 18. A mass spectrometer comprising a magnetic field confinement atmospheric pressure microglow discharge desorption mass spectrometry ion source as claimed in any one of claims 2 to 6, characterized in that it comprises a working gas introduction system, a sample introduction system, a normal A pressure microglow discharge desorption mass spectrometry ion source mass spectrometer and a mass spectrometry data processing system, the atmospheric pressure microglow discharge desorption mass spectrometry ion source is connected to the working gas introduction system through a pipeline conversion joint, the mass spectrometer is connected to the mass spectrometry data processing system Connection; sample setup includes one of the following two methods: Mode 1: A sample is placed between the ejection port of the micro-plasma generation chamber and the plasma gas inlet of the mass spectrometer; Method 2: The micro-plasma generation chamber is directly facing the plasma gas inlet of the mass spectrometer, and the sample is directly injected into the gas channel by the syringe pump. 19. The mass spectrometer according to claim 18, characterized in that, the atmospheric pressure microglow discharge desorption mass spectrometry ion source confined by the magnetic field is installed on a three-dimensional translation stage. 20. The mass spectrometer according to claim 19, wherein the working gas introduction system is provided with a gas flow controller, and the flow rate of the working gas is controlled within the range of 0.5L/min˜2.5L/min. 21. The mass spectrometer according to claim 19, wherein the sample introduction system comprises a sampling pump, a sampling needle and a capillary, and the sampling speed of the sampling pump is 0.1 μL/min～5 μL/min, The capacity of the sampling needle is greater than 5 μL, and the capillary is used to connect the sampling needle and the working gas path, and the material of the capillary is PEEK.