JP2000111524A - Mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mass spectrometer in which the inside of a vacuum container in a measuring or standby state can be returned to atmospheric pressure in a short time. SOLUTION: When the inside of a vacuum container 1 is to be returned to atmospheric pressure in a maintenance operation or the like, a temperature regulator 9 and an evacuation pump 2 are stopped. Then, when a leak switch 14 is turned on, a solenoid valve 12 is opened. An inert gas in a high-pressure gas cylinder 13 is jetted from a nozzle 10 and a nozzle 11 which are arranged and installed so as to be close to a heating part (a sample introduction part 3 and an ionization part 4 in the figure) inside the vacuum container 1. Consequently, the heating part is cooled quickly. When a pressure inside the vacuum container 1 reaches atmospheric pressure, a pressure switch 15 acts, and the solenoid, valve 12 is closed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mass spectrometer used for gas chromatography mass spectrometry (GC / MS) and the like.

[0002]

2. Description of the Related Art Conventionally, a gas chromatography mass spectrometer (GC / MS device) used for analyzing components of an organic compound by mass spectrometry has a structure as shown in FIG. The sample from which the components have been separated by the gas chromatograph (GC) is subjected to removal of the carrier gas by the separator of the sample introduction unit 3 and decompression from the GC side at atmospheric pressure to the mass spectrometer (MS) side under high vacuum. It is sent from the introduction unit 3 to the ionization unit 4. When the sample is subjected to, for example, an electron impact ionization method in the ionization section 4, molecules and atoms of the sample are ionized by being bombarded by thermoelectrons emitted from a filament such as rhenium. The molecules and atomic ions of the ionized sample are subjected to mass separation by a mass spectrometer 5 such as a quadrupole mass analyzer, and the molecules and atomic ions of the sample subjected to mass separation are detected by an ion detection unit such as an electron multiplier. By detecting in step 6, qualitative and quantitative measurement of the specific element in the sample is performed. In the system from ionization to ion detection, it is necessary to maintain a high vacuum in order to eliminate collision of the measured ions with other ions and residual gas. Therefore, the sample introduction unit 3, the ionization unit 4, the mass analysis unit 5, and the ion detection unit 6 is housed in the vacuum vessel 1, and an exhaust pump 2 for that purpose is connected to the vacuum vessel 1. During analysis and during standby, the exhaust pump 2 is operated so that the inside of the vacuum vessel 1 is always kept at a high vacuum.

On the other hand, the sample introduction section 3, ionization section 4, mass analysis section 5, and ion detection section 6 are generally heated to a temperature of about 200 ° C. in order to prevent adsorption and adhesion of the sample. Heaters 7, 8 and a temperature controller 9 for that purpose are prepared. In order to return the vacuum container 1 to the atmospheric pressure for maintenance of the apparatus, a method of attaching a leak valve 17 for leaking to the atmosphere as shown in FIG. Vacuum container 1 like
In order to introduce a replacement gas (inert gas such as nitrogen or helium) into the vacuum vessel 1 to keep the inside clean, a replacement gas cylinder 16 and a solenoid valve 12 are attached. At the time of maintenance, the heaters 7 and 8 are turned off, the operation of the exhaust pump 2 is stopped, and the leak valve 17 is opened to return the inside of the vacuum vessel 1 to the atmospheric pressure, or in the case of part A, the solenoid valve 12 is opened and the replacement gas cylinder 16 is opened. The replacement gas is introduced into the vacuum vessel 1 and when the inside of the vacuum vessel 1 reaches the atmospheric pressure, the electromagnetic valve 12 is closed.

[0004]

The conventional mass spectrometer is constructed as described above. However, when the vacuum vessel is returned to the atmospheric pressure for maintenance of the apparatus, the valve is opened and the air is suddenly opened. When a hot gas or a replacement gas is introduced into a vacuum vessel, the surface of the heated section, which is hot, is violently oxidized by oxygen in the air, causing impurities and dirt in the air to seize, possibly causing damage to the heated section ( Even when the replacement gas is introduced, if the vacuum container is opened for maintenance, the opening is large and there is a risk of contact with room air.) Therefore, the heating is usually stopped first, and the temperature of the heating unit is set to 100
The evacuation was stopped after waiting for the temperature to drop below ゜ C, and then the vacuum vessel was returned to atmospheric pressure.

[0005] For this reason, once the vacuum vessel is returned to the atmospheric pressure, a long waiting time is required, and the workability is extremely poor. The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a mass spectrometer that can complete its operation in a short time when returning a vacuum vessel to atmospheric pressure.

[0006]

In order to achieve the above object, a mass spectrometer according to the present invention separates ions by mass into a sample introduction section for introducing a sample and an ionization section for ionizing the introduced sample. At least one of the mass spectrometer and the ion detector for detecting the separated ions is provided with a heating means, and a nozzle connected to a high-pressure gas source via a shutoff valve is installed. And is disposed toward the heating portion. As a result, the nozzle connected to the high-pressure gas source rapidly reduces the temperature of the heating unit, and can return the vacuum container to the atmospheric pressure in a short time.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the mass spectrometer of the present invention will be described below with reference to FIG. In FIG. 1, reference numeral 1 denotes a vacuum vessel to which an exhaust pump 2 is connected. Reference numeral 3 denotes a sample introduction unit for introducing a sample sent from the gas chromatograph. The ionization unit 4, the mass analysis unit 5, and the ion detection unit 6 are connected to each other and disposed in the vacuum vessel 1. Then, the sample introduction unit 3, the ionization unit 4, the mass analysis unit 5, and the ion detection unit 6
Among them, heaters 7 and 8 are arranged for a portion to be heated (in the figure, the sample introduction unit 3 and the ionization unit 4 are selected as a portion to be heated). , 8. On the other hand, nozzles 10 and 11 having appropriate orifices are provided corresponding to heated portions, and these nozzles 10 and 11 are connected to a high-pressure gas cylinder 13 of an inert gas such as helium gas, argon gas or nitrogen gas. The piping is connected via a valve 12.
The electromagnetic valve 12 is connected to a pressure switch 15 attached to the vacuum vessel 1 and a leak switch 14 attached to the operation panel via an electric circuit (indicated by a dotted line in the figure).

Next, the operation of the mass spectrometer shown in FIG. 1 will be described. During measurement or standby of the mass spectrometer, the exhaust pump 2 is operated, and the vacuum vessel 1 is kept at a high vacuum of about 10 ⁻³ Pa. The portions to be heated in the vacuum vessel 1, that is, the sample introduction section 3 and the ionization section 4, are heated to 250 ° C. to 20 ° C. by the heaters 7 and 8 provided respectively.
It is heated to a high temperature of about 0 ° C. In order to control the temperature of the heaters 7 and 8 to be constant, the temperature controller 9 turns on and off the power of these heaters. Here, when the operation of the mass spectrometer is temporarily stopped for maintenance or the like, and the interior of the vacuum vessel 1 is to be returned to the atmospheric pressure, the operator operates the heaters 7 and 8.
Is turned off by the temperature controller 9 to stop heating, and further, the operation of the exhaust pump 2 is stopped. When the leak switch 14 is turned on, the solenoid valve 12 is opened, and the gas in the high-pressure gas cylinder 13 is injected from the nozzles 10 and 11 toward the heated portion. At the moment when the nozzles 10 and 11 are opened, the injected gas becomes adiabatic free expansion into a vacuum part,
In this case, since the inside of the vacuum vessel 1 is kept in a vacuum, there is no force against the expansion of the gas, so there is no interaction between the gas molecules, and the distance between the gas molecules due to the expansion increases (the volume increases). ) Does not change the gas temperature because no energy enters or exits. However, since the evacuation is stopped and the container is in a sealed state, the pressure in the vacuum container 1 increases in a very short time, and the injection of the high-pressure gas shifts to adiabatic reversible expansion into the vacuum container 1. That is, a force against the gas expansion is generated, and the internal energy of the gas is consumed by the expansion, and as a result, the gas temperature decreases. Assuming that the volume of the high-pressure gas changes (expands) from V1 to V2,
Similarly, when the absolute temperature changes from T1 to T2, the gas temperature T2 in the vacuum vessel 1 becomes T
2 = T1 (V1 / V2) ^{γ− 1,} and the heating unit is rapidly cooled. When the pressure in the vacuum chamber 1 reaches the atmospheric pressure, the pressure switch 15 operates and the solenoid valve 12 is closed.

In the illustrated example, the sample introduction section 3 and the ionization section 4 are selected as heating portions, and nozzles are provided for the sample introduction section 3 and the ionization section 4. May be provided, and more efficient flight of sample ions can be expected.

[0010] In the above embodiment, the high pressure gas is used as the source of the injection gas into the vacuum vessel 1.
However, the present invention is not limited to this. For example, a liquefied gas can be used as the injection gas source. Further, in the above embodiment, the solenoid valve 12 was closed when the pressure in the vacuum vessel 1 reached the atmospheric pressure. However, it was confirmed that the temperature of the heated portion was reduced to 100 ° C. or less by using the temperature controller 9. Upon detection, this signal can be used to close the solenoid valve 12. In this case, the vacuum vessel 1
If a non-return valve is attached to the vacuum vessel 1 in order to prevent the internal pressure from increasing, and if a certain amount of gas is allowed to flow out to keep the inside of the vacuum vessel 1 at a low pressure, the expansion will be large, and the temperature drop will be large. Cooling is more effective.

[0011]

According to the mass spectrometer of the present invention, the high-pressure gas is jetted from the nozzle to the heated portion in the vacuum vessel, so that the temperature of the heated portion can be rapidly lowered. Therefore, it is not necessary to wait for a long time to return the vacuum container to the atmosphere, and it is possible to open the vacuum container in a short time and perform maintenance.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a mass spectrometer of the present invention.

FIG. 2 is a diagram showing a conventional mass spectrometer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum container 9 ... Temperature controller 2 ... Exhaust pump 10, 11 ... Nozzle 3 ... Sample introduction part 12 ... Solenoid valve 4 ... Ionization part 13 ... High-pressure gas cylinder 5 ...... Mass spectrometer 14 Leak switch 7, 8 Heater 15 Pressure switch

Claims (1)

[Claims] 1. A sample introduction section for introducing a sample, an ionization section for ionizing the introduced sample, a mass analysis section for separating ions by mass, an ion detection section for detecting separated ions, and In a mass spectrometer comprising a vacuum container to house therein, at least one of the sample introduction unit, the ionization unit, the mass analysis unit, and the ion detection unit includes a heating unit, and a nozzle connected to a high-pressure gas source via a shutoff valve. Wherein the nozzle is installed in the vacuum vessel toward the heating portion.