JP4091977B2 - Fourier transform ion cyclotron resonance mass spectrometry method - Google Patents

Description

The present invention relates to a Fourier transform ion cyclotron resonance mass spectrometry method, and in particular, in a mass analysis of a gas sample having a quantitative limitation, a Fourier transform ion cyclotron for effectively introducing the sample into an analyzer for analytical measurement. Resonant mass spectrometry method

  Conventionally, analysis of reaction gas in chemical plant, analysis of metabolic function and anesthesia based on analysis of inhalation gas, call of living body, medical or medical component analysis to know reaction process, or semiconductor As a means for analyzing a desorbed gas and a generated gas for obtaining the surface state or reaction progress from a gas component desorbed by heating a catalyst or the like, a mass spectrometer has been proposed.

  Among these mass spectrometers, for example, Japanese Patent Application Laid-Open No. 5-54852 (Patent Document 1), which newly uses a Fourier transform method, has sufficient stability and automatically compensates for magnetic field drift. Thus, a Fourier transform mass spectrometer capable of performing high resolution mass spectrometry is disclosed. That is, this Fourier transform mass spectrometer ionizes a sample gas introduced into a high vacuum cell placed in a static magnetic field and applies a high frequency to an irradiation electrode pair provided in the high vacuum cell to generate a high frequency electric field. Apply to ions to induce ion cyclotron resonance in ions of a specific component to be measured, detect the ion cyclotron resonance as a high frequency electrical attenuation signal, convert this high frequency electrical attenuation signal into a digital signal, and time domain signal Is a magnetic field generating means comprising a permanent magnet or an electromagnet as a static magnetic field, a variable magnetic field compensation coil for compensating for the fluctuation of the static magnetic field, and a highly stable DC power source. And detecting long-period fluctuations in the magnetic field as changes in the ion cyclotron resonance frequency of a specific component, And a feedback means for feeding back the reduction amount in the highly stable direct-current power source as an error signal of the magnetic field varies, and is configured to control the magnetic field to hold the static magnetic field / radiation frequency ratio constant.

  The Fourier transform mass spectrometer configured as described above applies an irradiation frequency that approximates the ion cyclotron resonance frequency of the specific target ion to be measured to the irradiation electrode pair, and thus digitally converts the detected high-frequency attenuation signal. The specific target ions can be excited sufficiently large to be measurable within the limited dynamic range. In this Fourier transform mass spectrometer, the specific target ions in the sample gas can be continuously detected by supplying the sample gas continuously or periodically to the high vacuum cell.

  In addition, even if there is a change in the static magnetic field over time, the change over time is detected as a change in the ion cyclotron resonance frequency, and the irradiation frequency or the static magnetic field is controlled according to the change in the ion cyclotron resonance frequency. This makes it possible to compensate for changes in the magnetic field over time, or to calibrate the frequency measurement value, and to enable high-precision measurement even for changes in the ambient temperature surrounding the room or device where the Fourier transform mass spectrometer is installed. It is obtained.

Japanese Patent Laid-Open No. 5-54852

  However, when the amount of sample gas is very small, it is difficult to obtain a sufficient mass spectrum as an analysis result by the mass spectrometer described above. That is, in the case of a trace gas, infrared spectroscopy by an infrared analyzer is not easy, and injection into a gas chromatograph is difficult by sampling in a high vacuum due to the exclusion of background gas.

  For example, it may be necessary to analyze gas components that are adsorbed, occluded or encapsulated in the material. In other words, in various industries such as quality control requirements for residual gas in incandescent bulbs, development of discharge tubes and special bulbs, analysis of impurities in semiconductor packages, gas components in foam materials and their changes over time, etc. There is a request. In this case, the concentration of the target gas component is not necessarily low, but the amount is often strictly limited. Therefore, it is necessary to introduce the trace component gas desorbed from the sample into the analyzer as it is and effectively ionize it.

  However, in the past, there have been no studies and reports on means for obtaining an appropriate mass spectrum by mass spectrometry using this kind of trace component gas.

Therefore, an object of the present invention is a simple configuration capable of effectively analyzing a trace gas that is decomposed by adsorption, occlusion, or heating in a material in a Fourier transform ion cyclotron resonance mass spectrometry method for measuring a gas sample. An object of the present invention is to provide a Fourier transform ion cyclotron resonance mass spectrometry method that is easy to operate.

In order to achieve the above object, a Fourier transform ion cyclotron resonance mass spectrometry method according to the present invention includes a sample chamber in which a sample is inserted and arranged, and a turbo molecular pump and a foreline trap with respect to the sample chamber via a high vacuum valve. Open and close the vacuum line to which the rotary pump is sequentially connected, the analysis line to be connected to the sample chamber via a variable valve for connection to the mass spectrometer, and the vacuum line and the analysis line A branch line that communicates with each other via a valve, a temperature sensor provided in the sample chamber, and after the sample is sealed in the sample chamber, the chamber is evacuated to a high vacuum, thereby reducing the degree of vacuum in the chamber. Fourier transform that comprises a means for heating the desorption while monitoring the gas component at a temperature sensor, a means for introducing the gaseous component to the mass spectrometer Using Equation ion cyclotron resonance mass spectrometer,
Putting the sample in a heating means and sealing the sample chamber with a flange;
Closing the high vacuum valve and the variable valve, opening the open / close valve , and exhausting the sample chamber to 10 ⁻¹ to 10 ⁻³ Torr using a rotary pump ;
Closing the open / close valve and opening the high vacuum valve to evacuate the sample chamber to a high vacuum of 10 ⁻⁶ Torr;
Exhausting the sample chamber sufficiently, opening the variable valve, closing the vacuum valve and exhausting through the mass spectrometer;
And then heating the sample to the required temperature with the means for heat desorption,
The method includes a step of performing analytical measurement by introducing a minute amount of a component evaporated and desorbed from a heated sample into a mass spectrometer via a variable valve.

  According to the present invention, since a trace gas sample in a high vacuum can be directly introduced into a mass spectrometer and measured, a mass spectrum avoiding background signal contamination can be obtained, and the dynamic range of the analyzer can be reduced. The problem can be reduced. Therefore, according to the gas introducing device in the mass spectrometer according to the present invention, the use of the Fourier transform ion cyclotron resonance mass spectrometer as the mass spectrometer makes it possible to easily obtain a very high mass resolution. Due to the characteristics of the conversion method, the mass of the introduced gas component can be accurately determined, and gas components having the same mass number but different masses can also be directly separated, identified and quantified.

  Next, embodiments of the gas introduction device according to the present invention will be described in detail below with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a gas introduction apparatus according to the present invention, and shows a configuration for introducing a gas component desorbed from a sample into a mass spectrometer. That is, reference numeral 10 indicates a sample chamber. A specific example of the sample chamber 10 is shown in FIG. However, in FIG. 1 and FIG. 2, a vacuum line 20 in which a turbo molecular pump 14, a foreline trap 16 and a rotary pump 18 are sequentially connected to the sample chamber 10 is connected to the sample chamber 10 through a high vacuum valve 12. Therefore, this vacuum line 20 is used to evacuate the sample chamber 10 to a high vacuum. The sample chamber 10 is connected to an analysis line 24 for connection to a mass spectrometer (not shown) via a variable valve 22. Further, a branch line 28 that connects the analysis line 24 and the vacuum line 20 to each other via an opening / closing valve 26 is connected. Reference numeral 30 indicates a vacuum gauge connected to the vacuum line 20.

  In the apparatus of the present embodiment, the sample chamber 10 has a movable shaft 32 that linearly moves in the axial direction or rotationally moves around the shaft, and the sample is crushed at the tip of the movable shaft 32. A crushing means 34 is provided. Reference numeral 10 a indicates a flange portion that can be freely opened and closed for inserting the sample S into the sample chamber 10.

In the apparatus of this embodiment configured as described above, the sample S is inserted and arranged in the sample chamber 10 through the flange portion 10a. Next, the high vacuum valve 12 and the variable valve 22 are closed, the open / close valve 26 is opened, and the rotary pump 18 is driven to evacuate the sample chamber 10 to 10 ⁻¹ to 10 ⁻³ Torr. Thereafter, the open / close valve 26 is closed, the high vacuum valve 12 is opened, and the sample chamber 10 is evacuated to a high vacuum of about 10 ⁻⁶ Torr. This is a treatment for removing a residual gas component that hinders detection of a trace gas as a background signal or an unnecessary signal in mass spectrometry. Therefore, the ultimate vacuum pressure of the exhaust can be kept high until the amount of residual gas inside the sample chamber 10 (sample chamber volume × vacuum pressure) becomes sufficiently smaller than the amount of target gas desorbed from the sample S. is necessary. The ultimate vacuum can be measured with the vacuum gauge 30.

  When the inside of the sample chamber 10 is sufficiently evacuated, the variable valve 22 is opened and the vacuum valve 12 is closed. The sample chamber 10 is then exhausted through the mass spectrometer. If the degree of vacuum in the sample chamber 10 is balanced with the mass spectrometer, the mass spectrum of the residual gas displayed on the monitor display (not shown) of the mass spectrometer becomes almost constant. If the sample S is crushed by the movable shaft 32 by operating the crushing means 34 in this state, the gas contained in the sample is desorbed. The gas component thus desorbed can be introduced into the mass spectrometer via the variable valve 22 and its mass spectrum can be obtained. As a result, the gas component contained in the sample can be analyzed from the difference between the obtained mass spectrum and the previous residual gas mass spectrum.

In the embodiment shown in FIG. 2, the sample S is a small light bulb, and the case where the gas component enclosed in the small light bulb S is analyzed will be described below. In other words, in the quality control of the bulb, it is required to know the pressure and components of the gas inside the bulb. An incandescent lamp is generally manufactured by arranging a filament assembly or the like in a glass bulb and exhausting and sealing it with a rotary pump or the like. Therefore, the atmospheric pressure in the small sphere is 10 ⁻¹ to 10 ⁻³ Torr, and the amount of enclosed gas is very small. For this reason, prior to crushing the sphere, the sample chamber 10 is evacuated to a high vacuum of 10 ⁻⁶ Torr or less so as to avoid the influence of the residual gas in the chamber. Therefore, after evacuating to high vacuum, if the crushing means 34 is operated to crush the sample bulb S, the gas in the sphere diffuses into the sample chamber 10. The diffused gas is introduced into the mass spectrometer via the variable valve 22 and subjected to analytical measurement. 3A and 3B show a crushing part 36 that is attached to the tip of the movable shaft 32 of the crushing means 34 and crushes the sample S such as a light bulb. In order to function effectively regardless of the position where the sample is placed, a large number of through holes 38 having a diameter that is the same as the inner diameter of the sample chamber 10 and configured so that the desorbed gas can easily pass therethrough are formed. It is configured as a perforated plate or a lattice member. In the analysis of the sample, the gas contained in the sample is a mixed component in most cases. Therefore, the mass spectrum to be measured is a mixed spectrum in which the spectra of the individual components are added at an intensity corresponding to the content ratio. Therefore, when measurement is performed with a general mass spectrometer other than a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer, the spectra of components having the same mass number overlap each other, and discrimination is difficult. In principle, it is impossible to identify and quantify the components of the sample from such a mixed spectrum.

  Therefore, a so-called GC-MS method in which mass analysis is performed after a gas chromatograph is preliminarily isolated and individual components are isolated can be carried out as a general method for analysis of mixed components. It is practically impossible at present to inject a trace gas mixture into the pressurized carrier gas of a gas chromatograph, and these analyzes are difficult.

  However, according to the gas introduction device according to the present invention described above, a trace gas sample in a high vacuum can be directly introduced into a mass spectrometer and measured, so that a mass spectrum avoiding background signal contamination can be obtained. The problem of the dynamic range of the analyzer can be reduced. Therefore, when used in connection with a Fourier transform ion cyclotron resonance mass spectrometer, the chemical composition of the constituent gas component can be directly determined by precise measurement of the mass of the component gas.

  FIG. 4 is a cross-sectional side view of an essential part showing another embodiment of the sample chamber 10. That is, in FIG. 4, the sample S is a mercury discharge lamp or a special bulb in which a halogen, a rare gas, or the like is added. Therefore, in this embodiment, mercury vapor also diffuses when the sample S is crushed. However, mercury vapor may react with metals such as the sample chamber 10, flange, packing, and valve to form amalgam, which may deteriorate them. For this reason, in the present embodiment, the high vacuum bellows tube 40 connects the position of the sample S and the operation part of the sample chamber 10.

In the analysis measurement in this embodiment, only the sample and the flange portion 10a where the sample is arranged are immersed in a cryogen and cooled. When the cryogen is dry ice + amyl acetate, for example, the mercury vapor pressure is in the 10 ⁻⁹ Torr range. This is significantly lower than the vapor pressure of 10 ⁻³ Torr at normal temperature. That is, since the desorbed mercury vapor is trapped in the flange portion 10a that is almost cooled, the material corrosion can be reduced to about 10 ⁻⁶ as compared with the case where the bellows tube 40 is not connected.

  In the present embodiment, the bellows tube 40 is preferably made of thin stainless steel, has a long creepage distance, and has a very low thermal conductivity. As a result, even if the above-described sample arrangement portion is sufficiently cooled, it is possible to avoid a temperature drop in the mechanical operation unit such as the crushing means 34 and the valve. However, in the bellows tube 40, the exhaust conductance is low. For this, it is effective to use a high-vacuum ceramic tube or glass adapter that is commercially available recently.

  FIGS. 5A, 5 </ b> B, and 5 </ b> C show another embodiment of the crushing part 37 that is attached to the movable shaft 32 of the crushing means 34 and crushes the sample S. FIG. That is, the crushing part 37 of the present embodiment can be suitably used when analyzing and measuring a gas component contained in a sample such as a foam material. That is, unlike a light bulb or the like, this type of sample is flexible and elastic, so that the structure shown in FIG. . Therefore, as shown in the figure, the crushing part 37 is attached with two sharp blades 39 or conical members with opposite taper directions, so that even if the position of the sample is shifted, it is pressed so as not to move. The internal gas is separated by chopping, and the gas component is analyzed and measured.

  6 (a) and 6 (b) are cross-sectional side views of the main part showing still another embodiment of the sample chamber 10 configured to heat and desorb components adsorbed or occluded in the sample S. FIG. . In this embodiment, the sample chamber 10 is provided with a through terminal flange 50 instead of the crushing means, and a heater current terminal 52 and a temperature sensor sensor terminal 54 are mounted as terminals. A crucible 58 that can be heated by the heater 56 is disposed in the sample chamber 10. Therefore, in the analysis measurement of the sample S according to the present embodiment, the sample S is put in the crucible 58, the sample chamber 10 is sealed by the flange 50, the chamber is evacuated to a high vacuum, and then a current is supplied to the heater 56. The sample S in the crucible 58 is heated to a required temperature. The temperature at this time can be monitored by a temperature sensor as appropriate. In this way, the component vaporized and desorbed from the heated sample can be introduced into the mass spectrometer via the variable valve 22 and can be analyzed.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments, and various design changes can be made without departing from the spirit of the present invention.

It is a general | schematic systematic diagram of a mass spectrometer provided with the gas introduction apparatus which concerns on this invention. It is a principal part sectional side view showing one example of the gas introducing device concerning the present invention. An example of the crushing component attached to the movable shaft of the crushing means provided in the sample chamber of the gas introducing device according to the present invention is shown, (a) is a side view and (b) is a bottom view. It is a principal part cross-sectional side view which shows another Example of the gas introduction apparatus which concerns on this invention. The another example of the crushing component attached to the movable shaft of the crushing means provided in the sample chamber of the gas introducing device according to the present invention is shown, (a) is a bottom view, (b) is a right side view, and (c) is a front view. It is. The further another Example of the gas introduction apparatus which concerns on this invention is shown, Comprising: (a) is principal part sectional top view, (b) is principal part sectional side view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sample chamber 10a Flange part 12 High vacuum valve 14 Turbo molecular pump 16 Foreline trap 18 Rotary pump 20 Vacuum line 22 Variable valve 24 Analysis line 26 On-off valve 28 Branch line 30 Vacuum gauge 32 Movable shaft 34 Crushing means 36 Crushing part 37 Crushing Component 38 Through hole 39 Blade 40 Bellows tube 50 Flange with penetrating terminal 52 Current terminal 54 Sensor terminal 56 Heater 58 Crucible S Sample

Claims (1)

A sample chamber for inserting and arranging a sample, a vacuum line in which a turbo molecular pump, a foreline trap and a rotary pump are sequentially connected to the sample chamber via a high vacuum valve, and a variable valve for the sample chamber. An analysis line that is connected to be connected to the mass spectrometer via a branch line, a branch line that interconnects the vacuum line and the analysis line via an open / close valve, a temperature sensor provided in the sample chamber , and a sample a means for heating the desorption while monitoring a temperature sensor gaseous component from a sample without lowering the degree of vacuum in the chamber by exhausting the chamber to a high vacuum after sealing the sample chamber, the mass analyzing the gas component Using a Fourier transform ion cyclotron resonance mass spectrometer equipped with a means to be introduced into the meter ,
Putting the sample in a heating means and sealing the sample chamber with a flange;
Closing the high vacuum valve and the variable valve, opening the open / close valve , and exhausting the sample chamber to 10 ⁻¹ to 10 ⁻³ Torr using a rotary pump ;
Closing the open / close valve and opening the high vacuum valve to evacuate the sample chamber to a high vacuum of 10 ⁻⁶ Torr;
Exhausting the sample chamber sufficiently, opening the variable valve, closing the vacuum valve and exhausting through the mass spectrometer;
And then heating the sample to the required temperature with the means for heat desorption,
A Fourier transform ion cyclotron resonance mass using a Fourier transform ion cyclotron resonance mass spectrometer consisting of a step of introducing a small amount of components vaporized and desorbed from a heated sample into a mass spectrometer through a variable valve and performing an analytical measurement. Analysis method .

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