CN104810234A - Mass spectrometer and ionization device thereof - Google Patents

Abstract

The invention provides an ionization device which is used for ionizing sample molecules and comprises an atomizer and a microwave plasma emitter, wherein the atomizer receives and atomizes the sample molecules, and the microwave plasma emitter is used for emitting microwave plasma and ionizing the atomized sample molecules through the microwave plasma. The invention combines the high-temperature atomization mode with the microwave plasma mode, realizes the atomization and ionization of the sample, skillfully makes up for the defect of insufficient energy of the original microwave plasma light source, and improves the sensitivity of the mass spectrometer. The high temperature generated by the atomizer has larger energy, so that most of samples can be atomized, and metal ground state atoms of the samples can be obtained. Effectively overcomes the defects of weak energy and low ionization degree of a microwave plasma light source.

Description

Mass spectrometer and its ionization device

technical field

The invention relates to the technical field of spectrometers, in particular to a mass spectrometer and an ionization device thereof.

Background technique

Atomic spectroscopy has always been the most important means for people to analyze the elemental composition. Especially after the emergence of ICP light sources (power between 500 watts and 5000 watts) with excellent atomization and excitation properties. ICP spectroscopy has become the dominant method for emission spectroscopic analysis. For ultratrace analysis, ICP mass spectrometry has a clear advantage.

Another microwave plasma (MWP) light source developed at the same time as ICP has also been widely used. However, the microwave energy used in this method is relatively weak. During sample injection, the sample is generally sent into the microwave plasma source through an atomizer to form an aerosol. This sample injection method is very similar to the flame atomic absorption sample injection method. The difference is that because microwaves cannot provide enough energy and power, most of the microwave power will be absorbed by the sample solvent, and the microwave energy that actually plays an ionizing effect is a very small part, resulting in weakened ionization of the sample. The intensity of the ion current caused by mass spectrometry is weakened, which affects the sensitivity of the whole machine.

Therefore, providing a microwave plasma mass spectrometry method or a microwave plasma light source with higher microwave energy to overcome the shortcomings of the weak microwave plasma light source energy (about 150 watts) has become an urgent problem in this industry. Big technical problem.

Contents of the invention

The invention aims to solve the technical problem that the microwave energy of the microwave plasma mass spectrometry method in the prior art is relatively weak.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

The present invention proposes an ionization device for ionizing sample molecules, wherein the ionization device includes an atomizer and a microwave plasma emitter, and the atomizer receives and atomizes the sample molecules, The microwave plasma launcher is used to emit microwave plasma, and the atomized sample molecules are ionized by the microwave plasma.

According to an embodiment of the present invention, the atomizer is a flame atomizer, and the flame atomizer generates a flat flame region through combustion of combustion gas and atomizes the sample molecules.

According to another embodiment, the emission direction of the microwave plasma is perpendicular to the plane of the flame region.

According to another embodiment, the combustion gas is an air-acetylene mixed gas.

According to another embodiment, the atomizer is a graphite furnace atomizer, comprising a furnace body, a graphite tube disposed inside the furnace body through which light can pass, a sample injection window arranged at the upper end of the furnace body, and an opening. The openings at the ends of both sides of the furnace body, the sample molecules enter the graphite tube through the sampling window, the graphite tube atomizes the sample molecules at high temperature, and the microwave plasma is injected through the openings The graphite tube is used to ionize the sample molecules.

According to another embodiment, the emitting direction of the microwave plasma is perpendicular to the incident direction of light in the graphite tube.

According to another embodiment, the microwave plasma emitted by the microwave plasma emitter is argon plasma.

In order to solve the above technical problems, the technical solution proposed by the present invention also includes: proposing a mass spectrometer, including a sample source, an ionization device, a mass analyzer and a detector, wherein the ionization device is the ionization device , the sample source emits sample molecules, the ionization device atomizes and ionizes the sample molecules, and the ionized sample ions enter the mass analyzer and enter the detector after being separated according to the mass-to-charge ratio.

It can be seen from the above technical scheme that the mass spectrometer and its ionization device proposed by the present invention introduce an atomization method on the basis of microwave plasma technology, and combine the high-temperature atomization method with the microwave plasma method to realize the atomization of the sample. It cleverly makes up for the defect of insufficient energy of the original microwave plasma light source, and improves the sensitivity of the mass spectrometer. Among them, the high temperature generated by the atomizer has greater energy, which can atomize most of the samples and obtain the metal ground state atoms of the samples. It effectively makes up for the disadvantages of weak microwave plasma light source energy and low ionization degree. The microwave plasma emitted by the microwave plasma emitter can ionize the sample and then perform mass analysis on the ionized sample by the mass analyzer.

Description of drawings

FIG. 1 is a schematic structural view of the first embodiment of the ionization device proposed by the present invention;

2 is a block diagram of the workflow of the first embodiment of the ionization device proposed by the present invention;

3 is a schematic structural view of a second embodiment of the ionization device proposed by the present invention;

Fig. 4 is a block diagram of the workflow of the mass spectrometer proposed by the present invention.

Wherein, the reference signs are explained as follows:

1. Atomizer; 2. Microwave plasma emitter; 3. Flame atomizer; 30. Burner; 31. Flame area; 32. Atomizer; 33. Spray chamber; 4. Graphite furnace atomizer ; 40. furnace body; 41. sampling window; 42. opening; 5. sample source; 6. mass analyzer; 7. detector.

Detailed ways

Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and that the descriptions and illustrations therein are illustrative in nature and not intended to limit the present invention. invention.

The invention proposes a mass spectrometer and an ionization device constituting the mass spectrometer, that is, a mass spectrometer combining atomizer and microwave plasma technology.

Due to the low degree of ionization (the ratio of the number of ions to the total number of atomic ions) of microwave plasma, the ionization effect of the ICP method cannot be achieved. The ICP method can be estimated by the saha equation, which can generate an ionization degree close to 1%, so that the ion concentration reaches a high level, which can be considered as a thermal plasma. The ionization degree of microwave plasma is relatively low. For example, the temperature of argon flame produced by microwave is about 2000°C. According to the Boltzmann statistical distribution formula in atomic physics, the ionization energy at this temperature is Argon at 11ev has a lower probability. Therefore, the ionization degree of the existing microwave plasma light source to general metal atoms is below one ten-thousandth, which cannot meet the requirements for use.

In order to solve the problem of low energy of the microwave plasma light source and increase its degree of ionization, the present invention provides the following embodiments, which can be summarized as combining the atomization method, especially the high-temperature atomization method, with the microwave plasma method to achieve The method of "sample → atomization → ionization".

Ionization device embodiment 1

As shown in Figure 1, the present invention proposes an ionization device for ionizing sample molecules. It mainly includes an atomizer 1 and a microwave plasma emitter 2 . Atomizer 1 is mainly used to receive sample molecules and atomize them. The microwave plasma emitter 2 is mainly used to emit microwave plasma, and ionize the atomized sample molecules through the microwave plasma.

As shown in FIG. 1 and FIG. 2 , in this embodiment, the atomizer 1 is a flame atomizer 3 and a conventional structure can be selected. The flame atomizer 3 generates a planar high-temperature flame by burning gas to atomize sample molecules. It mainly includes an atomizer 32 , an atomization chamber 33 and a burner 30 connected in sequence.

In addition, as shown in Figure 1, the emission direction of the microwave plasma is perpendicular to the approximate plane of the high-temperature flame.

As shown in FIG. 1 , in this embodiment, the microwave plasma launcher 2 can be of a conventional structure, and the microwave plasma emitted by it can be of argon plasma. Since the argon plasma contains argon ions, its electron affinity is 15.76V, which can easily snatch an extranuclear electron from the metal atom, so that the entire metal atom is ionized.

As shown in FIG. 2 , during the working process, the sample molecules enter the nebulizer 32 and are atomized by the nebulizer 32 , and then become an aerosol state. The sample molecules in the aerosol state enter the atomization chamber 33 to be further refined and fully and evenly mixed with the combustion gas, so that the high-temperature flame emitted by the flame atomizer 3 can achieve a more stable laminar flow state. The combustion gas can be air-acetylene mixed gas, but it is not limited to this. The flame temperature of this combustion gas can reach above 2300°C, which can provide higher total energy and evaporate the moisture in the aerosol. Most of the sample molecules are atomized during combustion. The sample molecules fully and evenly mixed with the combustion gas enter the burner 30, evaporate and dry in the high-temperature flame to form dry aerosol mist particles, and then melt and dissociate into the ground state free atom vapor after being heated by the high-temperature flame to realize the atomization. Function. The microwave plasma launcher 2 emits argon plasma to the approximately planar high-temperature flame region 31 at a vertical angle, and the argon ions contained therein snatch an extranuclear electron from the atomized sample molecule, and the sample atom is ionized and Released into other analytical equipment, such as mass analyzers.

In addition, the injection method of the sample molecules in this embodiment is not necessarily limited to spray forms such as aerosol, and direct injection in solid or gaseous state can also be used.

Ionization device embodiment 2

The second embodiment of the ionization device proposed by the present invention differs from the above-mentioned first embodiment in that:

As shown in Figure 3, in this embodiment, the atomizer 1 of the ionization device is a graphite furnace atomizer 4, which utilizes a larger current to pass through a graphite tube with a higher resistance value to generate high temperature to make the sample molecule atoms change. The graphite furnace atomizer 4 also includes a furnace body 40, the interior of the furnace body 40 is provided with a graphite tube that can pass through the light originally used for atomic absorption spectroscopic analysis, and the upper end of the furnace body 40 is provided with a sampling window 41. Holes 42 are opened at both ends of the body 40 .

During the working process, the sample molecules enter the graphite tube provided inside the furnace body 40 through the sampling window 41, and a relatively large current is passed through the graphite tube to generate a high temperature in the graphite tube, which can reach 2000-3000 °C, so that the sample molecule atoms change. The microwave plasma launcher 2 emits argon plasma at an angle perpendicular to the light passing through the graphite tube, injects into the furnace body 40 through the opening 42 and enters the graphite tube, and the argon ions contained in the argon plasma snatch the atomized sample An extranuclear electron in the molecule, the sample atom is ionized and released, and enters other analytical equipment.

Mass spectrometer implementation

As shown in Figure 4, the mass spectrometer proposed by the present invention includes a sample source 5 that emits sample molecules, an ionization device that ionizes the sample molecules, receives the ionized sample molecules emitted by the ionization device, and analyzes the ionized sample molecules according to the mass Mass analyzer 6 and detector 7 for charge ratio separation. Wherein the ionization device is the ionization device proposed by the present invention.

During the working process, the sample source 5 releases the sample molecules, the ionization device atomizes and ionizes the sample molecules, and the ionized sample molecules enter the mass analyzer 6, and after the mass analyzer 6 separates the sample molecules according to the mass-to-charge ratio, the sample molecules After entering the detector 7, the separated sample ions enter the detector 7 one by one, collect and amplify the ion signal, process it with a computer, and draw it into a mass spectrum.

In addition, in this embodiment, when the atomizer 1 in the ionization device is a flame atomizer 3, light can pass through its high-temperature flame region 31 to perform atomic absorption spectroscopic analysis, that is, the mass spectrometer proposed by the present invention It can also be used as a spectrometer-mass spectrometer dual-purpose device.

While the mass spectrometer and ionization apparatus thereof of the present invention have been described with reference to several exemplary embodiments, it is to be understood that the terms which have been used are descriptive and exemplary, and not restrictive. Since the invention can be embodied in various forms without departing from its concept or essence, the above-described embodiments are not limited to any of the foregoing details, but should be construed broadly within the spirit and scope of the appended claims. All changes and modifications within the scope of the claims or their equivalents should be covered by the appended claims.

Claims (8)

1. an ionization apparatus, for ionization of sample molecule, is characterized in that, described ionization apparatus comprises:

Atomizer (1), receives described sample molecule and makes its atomization; And

Microwave plasma launcher (2), for penetrating microwave plasma, and makes atomizing sample molecule ionization by described microwave plasma.

2. ionization apparatus according to claim 1, it is characterized in that, described atomizer (1) is flame atomizer (3), and described flame atomizer (3) is produced the flame region (31) of flat by the burning of burning gases and made described sample molecule atomization.

3. ionization apparatus according to claim 2, is characterized in that, the injection direction of described microwave plasma is perpendicular to the plane of described flame region (31).

4. ionization apparatus according to claim 2, is characterized in that, described burning gases are air acetylene mist.

5. ionization apparatus according to claim 1, it is characterized in that, described atomizer (1) is graphite furnace atomizer (4), comprise body of heater (40), being located at described body of heater (40) inside can through the graphite-pipe of light, be located at the sample introduction window (41) of described body of heater (40) upper end and be opened in the perforate (42) of described body of heater (40) both side ends, described sample molecule enters graphite-pipe by sample introduction window (41), sample molecule described in described graphite-pipe high temperature atomic, described microwave plasma injects described graphite-pipe with sample molecule described in ionization through described perforate (42).

6. ionization apparatus according to claim 5, is characterized in that, direction is injected perpendicular to the light in described graphite-pipe in the injection direction of described microwave plasma.

7. mass spectrometer according to claim 1, is characterized in that, the microwave plasma that described microwave plasma launcher (2) sends is argon plasma.

8. a mass spectrometer, comprise sample source (5), ionization apparatus, mass analyzer (6) and detector (7), it is characterized in that, described ionization apparatus is the ionization apparatus in claim 1 ~ 8 described in any one, described sample source (5) releases sample molecule, described ionization apparatus is to described sample molecule atomization and ionization, and Ionized sample ions enters after described mass analyzer (6) separates by mass-to-charge ratio and enters described detector (7).