JP6548260B2 - Gas analyzer and gas analysis method - Google Patents

Description

  The present invention relates to a gas analyzer and a gas analysis method. In particular, the present invention relates to a gas analyzer and a gas analysis method for analyzing the mass of trace components in a gas using freeze condensation and temperature programmed desorption.

  It is known to use cryogenic concentration (also called cryofocus) in the analysis of trace constituents contained in gas. There is a gas analyzer using such a cryofocus (see, for example, Non-Patent Document 1).

  Non-Patent Document 1 discloses that volatile compounds are extracted and analyzed using a gas analyzer that combines a cryofocuser, gas chromatography (GC) and mass spectrometer (MS). According to the gas analyzer of Non-Patent Document 1, the cryofocusing device is installed in front of the inlet of the GC column, and the sample is installed in the cryofocusing device by cooling the adsorption tube to a temperature lower than room temperature. Low temperature condensation (freeze condensation) of gas components on the surface of the adsorption tube is performed. At this time, the temperature of cooling is adjusted in accordance with the sample gas component.

  The procedure of gas analysis by the gas analyzer described in Non-Patent Document 1 is as follows. The cryofocus is cooled to an arbitrary temperature, and the sample gas component is freeze-condensed into a cooled adsorption tube by introducing a sample gas into it. After sufficiently freeze-condensing the sample gas, the sample gas component is volatilized by rapidly heating the adsorption tube to obtain a concentrated sample gas component. Then, the concentrated sample gas is analyzed by GC-MS. Thus, cryofocus-GC-MS according to Non-Patent Document 1 enables analysis of trace gas components such as volatile organic compounds (VOCs) contained in the atmosphere, exhaled breath and the like.

  However, according to Non-Patent Document 1, in gas analysis by cryofocus-GC-MS, cryofocus is used only for concentration of sample gas, and gas analysis itself is performed by GC-MS. The GC-MS is relatively large and is not easy to handle, and is expensive, so there are problems such as limitation of an engine which can be introduced into the apparatus. Furthermore, in gas analysis by GC, there are also problems such as the need for preliminary knowledge on the properties of the gas to be measured when selecting a GC column, and the need for certain learning in measurement operation and data analysis. It would be desirable if a gas analyzer was developed that is better in handling than Cryofocus-GC-MS and does not require skilled technology or knowledge.

  On the other hand, Temperature programmed desorption (TPD) or Thermal desorption spectroscopy (TDS) is known as a method for analyzing gas species adsorbed on the surface of a solid substrate by MS or the like while raising the substrate temperature. There is. TPD is still widely used in the surface science field as a method used to analyze the adsorption state of gas species and the like adsorbed on the surface of a solid substrate.

There is an apparatus using TPD which can cool a substrate to a cryogenic temperature of about 10 K (see, for example, non-patent documents 2 and 3). Non-patent documents 2 and 3 perform analysis of gas species adsorbed on a solid substrate surface in ultrahigh vacuum (vacuum degree is 10 ⁻⁶ Pa or less) using a cryogenic TPD apparatus.

  However, the cryogenic TPD devices described in Non-Patent Documents 2 and 3 are assumed to be used in the field of surface science, and can not analyze gases such as the atmosphere and breath. It would be desirable if the cryogenic TPD device could be modified to analyze gases such as air and breath.

C. Lee et al., Analytical Methods, 2015, 5, 7, 3521 R. Souda, Surf. Sci. , 605, 201, 1257 A. K. Santra et al. Phys. Chem. , B 106, 2002, 340

  An object of the present invention is to provide a gas analyzer that analyzes the mass of a substance contained in an extremely small amount in a gas, and a gas analysis method.

A gas analyzer for analyzing the mass of one or more substances out of the plurality of substances according to the present invention comprises a vacuum chamber having a first vacuum pump and having an introduction pipe for introducing the gas; A cooling device connected to a vacuum chamber, and a support connected to the cooling device and disposed in the vacuum chamber, wherein at least one substance of the introduced gas is frozen by the cooling device The apparatus includes: a support on which a substrate to be condensed is placed; a heating device for heating the substrate placed on the support; and a mass analysis mechanism connected to the vacuum chamber, the mass analysis mechanism comprising A suction pipe for sucking the one or more substances detached from the substrate by the heating device, and a part of the one or more substances sucked by the suction pipe are evacuated to make the inside of the mass analysis mechanism in a vacuum state Maintenance A second vacuum pump, and a mass analyzer that analyzes the mass of the one or more substances that have not been evacuated, and the suction tube is disposed such that one open end thereof faces the substrate, And the suction tube is movable in proximity to the substrate, and the suction tube has a tapered shape so that the diameter of the one open end is smaller than the diameter of the other portion of the suction tube, The above-mentioned subject is achieved by this.
The ratio of the bore diameter of the other portion of the suction pipe to the bore diameter of the one open end may be in the range of 2.5 or more and 5.5 or less.
The diameter of the one open end may be in the range of 5 mm to 7 mm.
The tube thickness of the one open end having the tapered shape may be thicker than that of the other portion.
The second vacuum pump may maintain the inside of the mass analysis mechanism in a vacuum state in the range of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻² Pa or less.
The support may be further provided with a moving mechanism that moves and rotates the support in the x, y and z directions.
The movement of the support by the moving mechanism and / or the suction tube such that the surface of the substrate placed on the support and the end face of the one open end of the suction tube face in parallel. You may further provide the control part which controls movement.
The control unit may control the moving mechanism and / or the suction pipe such that the distance between the one open end and the substrate is in the range of more than 0 mm and 3 mm or less.
The control unit may control the moving mechanism and / or the suction pipe such that a distance between the one open end and the substrate is in a range of 0.5 mm or more and 1 mm or less.
The cooling device may be a mechanical refrigerator or a cryogen.
The heating device may be selected from the group consisting of a resistive heating device, an infrared heating device and an electron impact heating device.
The apparatus may further include a control unit that controls the operation of a heating device that heats the substrate.
The mass analyzer may be selected from the group consisting of a quadrupole mass analyzer, a time of flight mass analyzer, and a cyclotron resonance mass analyzer.
The support may include a cold head and a heat transfer bar, and the substrate may be mounted on the tip of the heat transfer bar.
The first vacuum pump may maintain the vacuum chamber in a vacuum state of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻¹ Pa or less.
According to the present invention, a method of analyzing a mass of one or more substances among a plurality of substances according to the present invention comprises the steps of: evacuating the inside of a vacuum chamber; at least a substrate located in the vacuum chamber; Cooling to a temperature not higher than triple point among the triple points of each of the one or more substances, introducing the gas into the vacuum chamber, and freezing and condensing the one or more substances on the substrate; Heating the substrate, respectively desorbing the one or more substances from the substrate, and analyzing the mass of the one or more substances using a mass spectrometer, wherein the aperture diameter of one open end is that Using the suction pipe smaller than the diameter of the other part, the one or more substances are suctioned by the suction pipe while the one open end is opposed so as not to contact the substrate Both evacuated part of aspirated said one or more substances in the suction tube, and analyzing the remaining mass analyzer includes a step, thereby achieving the above-mentioned problems.
The analyzing may include evacuating a portion of the one or more substances to maintain a vacuum in the range of 1 × 10 ⁻⁸ Pa to 1 × 10 ⁻² Pa.
In the freezing and condensing step, the gas may be introduced at a partial pressure in the range of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻¹ Pa or less, and may be frozen and condensed for a time in the range of 30 seconds or more and 15 minutes or less .
In the freezing and condensing step, the substrate may be cooled to a temperature equal to or lower than the lowest thermal desorption temperature among thermal desorption temperatures of at least one or more substances.
In the analysis step, the suction pipe may be opposed to the substrate such that the distance between the one open end of the suction pipe and the substrate is in the range of more than 0 mm and 3 mm or less.
The analyzing may measure the temperature-programmed desorption spectrum of each of the one or more substances, and analyze the mass of each of the one or more substances from the respective temperature-programmed desorption spectrum.
The analyzing step may calculate peak areas in the respective temperature programmed desorption spectra.
The freezing and condensing step may further include preliminary freezing and condensing at least a portion of the plurality of substances different from the one or more substances.
In the preliminary freeze-condensing step, the partial region of the substrate is higher than the highest thermal desorption temperature among the thermal desorption temperatures of each of the one or more materials, and the one or more materials Cooling to a temperature equal to or lower than the thermal desorption temperature of at least a portion of the plurality of different substances, and freezing and condensing the at least a portion on the portion of the substrate, and another region of the substrate Cooling to a temperature below the lowest thermal desorption temperature of the thermal desorption temperatures of each of the one or more substances, and freezing and condensing the one or more substances on the other region of the substrate. It may further include.
In the desorption step, the substrate may be heated at a heating rate of 2 K / min to 8 K / min for each thermal desorption temperature range of ± 20 K of the one or more substances.
The one or more substances may be selected from the group consisting of volatile organic compounds, noble gas elements and air pollutants.
The substrate may be selected from the group consisting of oxide single crystals, polycrystalline metals, single crystal metals, single crystal semiconductors and layered materials.

  The gas analyzer according to the present invention freezes and condenses at least one substance to be analyzed on a substrate by a cooling device, and thermally desorbs each of the one or more substances to be analyzed by a heating device. Since desorption is performed at temperature, it is possible to obtain a gas (selective enrichment gas) in which one or more substances are selectively concentrated at each thermal desorption temperature. Furthermore, the selective enrichment gas is mass analyzed in a mass spectrometer equipped with a mass spectrometer, a second vacuum pump and a mass spectrometer, but such selective enrichment gas is aspirated and introduced into the mass spectrometer. The suction tube is disposed such that one open end thereof faces the substrate and is movable so as to be close to the substrate, so that the mixing of unnecessary gas released from a place other than the substrate is suppressed. Be able to analyze with high accuracy. Furthermore, since the suction pipe has a tapered shape so that the diameter of one open end is smaller than the diameter of the other part of the suction pipe, the second vacuum pump is a part of the selectively condensed gas that has been drawn. It is possible to exhaust the part efficiently. As a result, the vacuum in the mass analysis mechanism is maintained so that the mass analyzer operates and allows analysis. The gas analyzer according to the present invention is advantageous because it eliminates the need for chromatography, which not only reduces the overall size of the device but also simplifies the operation of the device.

  The gas analysis method according to the present invention cools the substrate to a temperature below the lowest triple point among the triple points of each of the at least one substance, and the thermal desorption temperature specific to the one or more substances from the substrate. At each thermal desorption temperature, it is possible to obtain a gas in which one or more substances are selectively concentrated. Although the selective concentration gas is drawn by the suction tube and analyzed using a mass spectrometer, the selective concentration gas is drawn while opposing the one open end not to contact the substrate, so that it is removed from the place other than the substrate Contamination of unwanted unwanted gas is suppressed, enabling highly accurate analysis. In addition, since the bore diameter of one open end of the suction pipe is smaller than the bore diameter of the other part, exhausting of a part of the selectively condensed gas sucked by the suction pipe is efficiently performed. As a result, the operable vacuum state of the mass analyzer is maintained so that the mass analyzer operates and allows analysis.

Schematic of gas analyzer according to the invention The schematic diagram which expands and shows a part of suction pipe by this invention Flow chart for performing gas analysis of the present invention Diagram showing freeze condensation and selective enrichment gas Diagram schematically showing freeze condensation and selective enrichment gas by preliminary freeze condensation Schematic diagram of the gas analyzer of the present invention constructed in Example 1 Figure 2 shows the effect of the distance between the substrate and the suction tube on temperature and pressure according to Example 1 The figure which shows the temperature rising desorption spectrum at the time of freezing-condensing the atmosphere containing ⁸⁴ Kr 0.65 ppm by 6K for 1 minute by Example 2 The figure which shows the relationship of the density | concentration of ⁸⁴ Kr and the ion current which were calculated | required from the thermal desorption peak at the time of freezing and condensing the atmosphere containing ⁸⁴ Kr of various density | concentrations in 6K for 1 minute by Example 2. The figure which shows the relationship of the freeze-condensing time and the ion current which were calculated | required from the thermal desorption peak at 6 K and the atmosphere containing ⁸⁴ Kr 0.65 ppm according to Example 2 freeze-condensing for 6 hours and various times. The figure which shows the mass spectrometry spectrum by the comparative example 3 The figure which shows the temperature rising desorption spectrum at the time of freeze-condensing air | atmosphere containing acetone 100 ppm by the Example 4, acetone, and air | atmosphere at 50 K for 1 minute for 1 minute. The figure which shows the relationship between the acetone concentration and the ion current which were obtained from the temperature rising desorption spectrum at the time of freezing and condensing the air | atmosphere containing the acetone of various concentration by 50K and 1 minute by Example 4 The figure which shows the temperature rising desorption spectrum at the time of freezing-condensing the air containing 100 ppm of acetone by 145 K for 1 minute by Example 5 according to Example 5.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same number is given to the same element and the description is abbreviate | omitted.

  FIG. 1 is a schematic view of a gas analyzer according to the present invention.

  The gas analyzer 100 according to the present invention performs mass analysis of at least one substance out of gas (gas) composed of a plurality of substances by freeze condensation and temperature-programmed desorption (freeze-condensed-temperature programmed desorption analysis). It can be carried out. The plurality of substances is any substance that constitutes a gas, but the one or more substances to be analyzed are preferably one or more from the group consisting of rare gas elements, volatile organic compounds (VOCs) and air pollutants. It is a substance to be selected. The rare gas element is a Group 18 element of the periodic table, and includes helium, neon, argon, krypton, xenon, radon and the like. Volatile organic compounds (VOCs) are formaldehyde, toluene, acetone, ethanol, 2-propanol, hexanal, d-limonene, propionaldehyde and the like. Air pollutants include nitrogen compounds (NOx) such as nitrogen dioxide, sulfur compounds (SOx) such as sulfur dioxide, photochemical oxidants (Ox), carbon monoxide (CO) and the like. With the gas analysis device 100 according to the invention, not only the presence of one or more substances to be analyzed as described above, but also its mass analysis can be performed.

  The gas analyzer 100 according to the present invention has an inlet pipe 110 for introducing a gas composed of a plurality of substances, and is connected to a chamber 130 provided with a first vacuum pump 120 for adjusting the internal pressure, and the vacuum chamber 130 Connected to the cooling device 140, the support 150 connected to the cooling device 140 and disposed in the vacuum chamber 130, the heating device 170 for heating the substrate 160 placed on the support 150, and the vacuum chamber 130 And the mass spectrometer 180. A substrate 160 on which at least one substance to be analyzed among a plurality of substances introduced from the introduction pipe 110 is frozen and condensed by the cooling device 140 is mounted on the support 150.

  With such a configuration, the gas analyzer 100 according to the present invention freezes and condenses at least one or more substances to be analyzed, and performs temperature programmed desorption analysis. In detail, the gas analyzer 100 according to the present invention freezes and condenses at least one substance among a plurality of substances introduced from the introduction pipe 110 on the substrate 160 by the cooling device 140. Then, the temperature at which the freeze-condensed substance thermally desorbs (thermal desorption temperature) is intrinsic to the substance, and the heating device 170 is used to analyze at least one of the thermal desorption temperatures from the substrate 160 at one or more temperatures. Allow each of the substances to thermally desorb. A gas (also referred to simply as a selective enrichment gas), in which the one or more substances to be analyzed in this way are selectively enriched, can be obtained at each thermal desorption temperature. If the mass spectrometry mechanism 180 functions to detect only a substance having a specific mass-to-charge ratio (m / z) with respect to the selectively enriched gas thus obtained, the temperature rise with the heating device 170 It is possible to obtain a thermal desorption spectrum having a thermal desorption peak according to at least one or more substances. It goes without saying that mass spectrometry can be performed for all substances by freeze-condensing all of the introduced gases consisting of a plurality of substances.

  In addition, since the thermal desorption temperature is unique to the substance as described above, for example, even different molecular species having the same molecular weight can be easily separated since they have different thermal desorption temperatures.

The first vacuum pump 120 is preferably one or more pumps selected from the group consisting of a rotary pump, an oil diffusion pump, a turbo molecular pump, and an ion pump. The vacuum chamber 130 is maintained at a vacuum of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻¹ Pa or less by the first vacuum pump 120.

  The cooling device 140 is not limited as long as it can cool at least one or more substances to be analyzed to the temperature below its triple point, but is preferably a mechanical refrigerator or freezing medium. Specifically, the mechanical refrigerator is a Stirling refrigerator, a Gifford McMahon refrigerator (GM refrigerator), a pulse tube refrigerator, or the like. Cryogens include liquid nitrogen, liquid helium and the like. By using these, since it is possible to cool to cryogenic temperature, it is possible to freeze and condense the substance to be reliably analyzed.

  The support 150 is not particularly limited as long as the substrate 160 can be mounted and the substrate 160 can be cooled by the refrigerator 140. For example, the support 150 includes a cold head and a heat transfer rod, and the tip of the heat transfer rod The substrate 160 may be placed. Thus, the substrate 160 can be efficiently cooled, and the operability of the substrate 160 is excellent.

  The substrate 160 is not particularly limited as long as it is a stable material in the atmosphere and has a flat surface, but is preferably selected from the group consisting of oxide single crystals, polycrystalline metals, single crystal metals, single crystal semiconductors and layered materials. Be done. More specifically, the oxide single crystal is zinc oxide, sapphire or the like, and the polycrystalline metal is polycrystalline tantalum, polycrystalline niobium, polycrystalline tungsten, an alloy thereof or the like. The single crystal metal is single crystal niobium or the like. The single crystal semiconductor is single crystal silicon or the like. Layered materials are graphite and the like.

  The heating device 170 is not particularly limited as long as it can heat at least one or more substances to be analyzed to the thermal desorption temperature, but is selected from the group consisting of, for example, a resistance heating device, an infrared heating device and an electron impact heating device A heating device is employed. These heating devices not only are easy to operate but also allow for precise temperature control. Moreover, an electromagnetic wave heating apparatus, an induction heating apparatus, etc. are also employable.

  Further, a temperature sensor such as a thermocouple may be installed near the substrate 160, for example, the support 150 so that the cooling temperature of the substrate 160 by the cooling device 140 and the heating temperature of the substrate by the heating device 170 can be accurately measured. .

  Furthermore, the operation of the cooling device 140 and / or the heating device 170 may be controlled by programming, which will be described later, in which the control unit described later stores the triple point and / or thermal desorption temperature of the substance to be analyzed. Good.

  In addition, in FIG. 1, although the heating apparatus 170 is shown as being installed in the support body 150, it does not restrict to this structure. For example, when an infrared heating device is used as the heating device 170, the substrate 160 may be irradiated with infrared light.

  Furthermore, we have appropriately aspirated the selectively enriched gas of each of the one or more substances to be analyzed by temperature programmed desorption into the mass spectrometry mechanism 180, as well as the aspirated selectively enriched gas It is found that it is necessary to control the degree of vacuum in the mass spectrometric analysis mechanism 180 by gas concentration analysis with high accuracy by freeze condensation-temperature programmed desorption analysis, and suitable for freeze condensation-programmed temperature desorption analysis The gas analyzer 100 of the present invention equipped with a mass spectrometer 180 was developed. The mass spectrometry mechanism 180 will be described in detail.

  In the gas analysis apparatus 100 according to the present invention, the mass analysis mechanism 180 is aspirated by the aspiration pipe 181 for aspirating selectively concentrated gas of one or more substances desorbed from the substrate 160 by the heating device 170 and The second vacuum pump 182 exhausts a part of the selected concentrated gas and maintains the inside of the mass analysis mechanism 180 in a vacuum state, and the mass analyzer analyzes the mass of the remaining selectively condensed gas which has not been exhausted. And 183.

  FIG. 2 is a schematic view showing an enlarged part of a suction pipe according to the present invention.

  Here, the suction pipe 181 is disposed such that one open end 210 thereof faces the surface of the substrate 160 and is movable so as to be close to the substrate 160. Thereby, the mixing of the unnecessary gas desorbed from the place other than the substrate 160 into the suction pipe 181 is suppressed, and highly accurate analysis is enabled. Although the movement of the suction tube 181 is shown in FIG. 1 as moving in the horizontal direction with respect to the paper surface, the movement of the suction tube 181 is not limited to this as long as it can move close to the surface of the substrate 160. In addition, the movement of the suction tube 181 may be performed manually, for example, visually from a window (viewing port) provided in the vacuum chamber 130, or a control unit described later controls the movement device etc. It is also good.

  The suction pipe 181 has a tapered shape such that the diameter φ of one open end 210 is smaller than the diameter φ of the other portion 220. As a result, the conductance of the second vacuum pump 182 can be increased, so that a part of the sucked selective concentrated gas can be efficiently exhausted. As a result, since the vacuum state in the mass spectrometer 180 is maintained, the mass spectrometer 183 operates reliably and enables highly accurate analysis.

  In the suction pipe 181, preferably, the ratio of the diameter Φ of the other portion 220 to the diameter φ of one open end 210 satisfies the range of 2.5 or more and 5.5 or less. Thereby, the conductance of the second vacuum pump 182 can be further increased. More preferably, the ratio of the diameter Φ of the other portion 220 to the diameter φ of one open end 210 satisfies the range of 4 or more and 4.5 or less. Thereby, the conductance of the second vacuum pump 182 can be reliably increased.

  In the suction pipe 181, preferably, the bore diameter φ of one open end 210 satisfies the range of 5 mm or more and 7 mm or less. Thereby, the vacuum between the vacuum chamber 130 and the mass analysis mechanism 180 can be divided.

  In the suction tube 181, preferably, the tube thickness of one open end 210 is thicker than that of the other portion 220. As a result, even if the suction pipe 181 is sufficiently brought close to the substrate 160, the temperature rise of the substrate 160 due to the heat radiation is suppressed, so that the temperature rise can be made accurate and the analysis can be performed with high accuracy.

  The suction tube 181 is preferably made of a material having a small emissivity, specifically, a material having an emissivity satisfying the range of 0 or more and 0.5 or less with respect to light having a wavelength of 1 μm. Thereby, even when the suction pipe 181 is brought close to the surface of the substrate 160, it is possible to suppress the temperature rise due to the heat radiation in the mass analysis mechanism 180. The material satisfying the above-mentioned emissivity is, for example, stainless steel, aluminum whose surface is polished, or the like.

Similar to the first vacuum pump 120, the second vacuum pump 182 is one or more pumps selected from the group consisting of a rotary pump, an oil diffusion pump, a turbo molecular pump, and an ion pump, but the second vacuum pump By 182, the mass spectrometry mechanism 180 is maintained lower than the degree of vacuum of the vacuum chamber 130, preferably in a vacuum state of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻² Pa or less. This ensures evacuation of part of the selectively concentrated gas aspirated by the aspirating tube 181, and the operation range of the mass spectrometer 183 is achieved, so that mass spectrometry can be performed reliably.

  Although the second vacuum pump 182 is shown as a single unit in FIG. 1, vacuum pumps may be provided in multiple stages to maintain the above-described vacuum state.

The mass analyzer 183 employs any mass analyzer used for mass analysis, but exemplarily includes a group consisting of a quadrupole mass analyzer, a time-of-flight mass analyzer, and a cyclotron resonance mass analyzer. A mass spectrometer selected from These can be applied to and operate in the mass spectrometer of the present invention. Among other things, the quadrupole mass spectrometer operates at a vacuum of 1 × 10 ⁻² Pa, which is advantageous because it is not necessary to maintain the vacuum in the mass spectrometer 180 at a high vacuum.

  Mass spectrometer 183 measures the thermal desorption spectrum for the selectively enriched gas. The control unit described above may receive the data of the temperature-programmed desorption spectrum, calculate the peak area, and perform mass analysis.

  Returning to FIG. 1 again, the gas analyzer 100 of the present invention may further include a moving mechanism (not shown) that controls the operation of the support 150. The moving mechanism is, for example, provided on the top of the support 150, and can move and rotate the support 150 in the x, y and z directions. Thereby, even if the support 150 is deformed by the cooling by the cooling device 140 or the heating by the heating device 170, the substrate 160 mounted on the support 150 and the one open end 210 of the suction pipe 181 can be secured. High accuracy analysis can be achieved.

  The gas analyzer 100 of the present invention may further include a control unit (not shown) that controls the movement mechanism and / or the operation of the suction pipe 181. The control unit moves the support 150 by the moving mechanism and / or the suction tube so that the surface of the substrate 160 placed on the support 150 and the one open end 210 of the suction tube 181 face in parallel. Control the movement of 181. The control unit may simultaneously control both the operation of the moving mechanism and the operation of the suction tube 181, or may control either one.

  The control unit includes a central processing unit (CPU) and an application specific integrated circuit (ASIC), and controls the movement of the support 150 by the moving mechanism and / or the movement of the suction pipe 181. As a result, the surface of the substrate 160 and one open end 210 of the suction tube 181 can be made to face each other in parallel, so that the selectively concentrated gas desorbed from the substrate 160 is sucked, and the system of analysis is improved. obtain.

  More preferably, the control unit moves the support 150 by the moving mechanism and / or the suction tube 181 such that the distance between the surface of the substrate 160 and the one opening resistance 210 is in the range of more than 0 mm and 3 mm or less. Control the movement. Thereby, even when the selective concentration gas from substrate 160 is sucked, temperature rise and vacuum fluctuation due to heat radiation in mass spectroscope 180 do not substantially affect mass spectrometer 183. So you can analyze it reliably.

  More preferably, the control unit moves the support 150 by the moving mechanism and / or the suction tube 181 such that the distance between the surface of the substrate 160 and the one opening resistance 210 is in the range of 0.5 m to 1 mm. Control the movement of As a result, even when the selective concentration gas is sucked, the temperature rise due to the heat radiation in the mass analysis mechanism 180 is surely suppressed and the degree of vacuum is reduced, so that the analysis can be performed with high accuracy.

  Next, with reference to FIGS. 1 to 5, a gas analysis method for gas analysis will be described, which analyzes the mass of one or more substances out of the plurality of substances according to the present invention. In addition, since one or more substances to be analyzed are as described in the gas analyzer 100, the description will be omitted.

FIG. 3 is a flow chart of gas analysis of the present invention.
FIG. 4 is a diagram schematically showing freeze condensation and selective enrichment gas.

Step S310: The inside of the vacuum chamber 130 (FIG. 1) is evacuated. Here, the vacuum chamber 130 is maintained at a vacuum of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻¹ Pa or less by the first vacuum pump 120 (FIG. 1) or the like.

  Step S320: The substrate 160 (FIG. 1) located in the vacuum chamber 130 is, for example, by the cooling device 140 (FIG. 1) or the like to the lowest temperature of the triple point among the at least one substance. Cooling. Then, a gas is introduced into the vacuum chamber 130. Thereby, at least one or more substances to be analyzed out of the gas composed of a plurality of substances are freeze-condensed on the substrate 160. As an illustrative substance to be analyzed, krypton, rare gas elements such as argon and neon, triple points of volatile organic compounds such as acetone and thermal desorption temperatures are shown in Table 1.

  The state of freezing and condensation will be described in detail with reference to FIG. As shown in FIG. 4A, the region 410 of the substrate 160 is cooled to a temperature not higher than the triple point of the at least one or more substances.

  Next, as shown in FIG. 4 (B), a gas consisting of one or more substances to be analyzed (black) and the other substances (white) is introduced. Here, for the sake of simplicity, it is assumed that one or more substances to be analyzed and other substances are each one. That is, the gas consisting of a plurality of substances is made of two kinds of substances. Furthermore, the triple point of the other substances shall be higher than that of the one or more substances to be analyzed.

  When the gas is introduced, any substance freezes and condenses on the area 410 of the substrate 160, as shown in FIG. 4 (C). That is, one or more substances to be analyzed are always frozen and condensed on the substrate 160. Although FIG. 4C shows an example in which all substances are substantially freeze-condensed, the present invention is not limited to this. Since at least one or more substances to be analyzed may be freeze-condensed, the triple point of the other substances is significantly lower than that of the one or more substances, and in step S320, the substrate 160 is The temperature may be higher than the triple point of the substance and may be lower than the triple point of one or more substances.

  As shown in Table 1, the triple point of the material is usually above its thermal desorption temperature. Thus, preferably, the substrate 160 is cooled to a temperature below the lowest thermal desorption temperature of the thermal desorption temperatures of each of the at least one substance. Thereby, one or more substances can be surely frozen and condensed on the substrate 160.

In step S320, preferably, the gas is introduced at a partial pressure in the range of 1 × 10 ⁻⁸ Pa to 1 × 10 ⁻¹ Pa, and freeze condensation is performed for a time in the range of 20 seconds to 15 minutes. If a gas is introduced under these conditions, a predetermined amount of one or more substances can be freeze-condensed, and mass analysis can be performed. More preferably, the gas is freeze-condensed for a time ranging from 1 minute to 15 minutes. This freezes and condenses more one or more substances, thereby improving the peak intensity of the thermal desorption spectrum and reducing the detection limit. If it exceeds 15 minutes, there is a possibility that the degree of vacuum may decrease due to the temperature rising and releasing in step S330 described later. More preferably, the gas is freeze condensed for a time ranging from 3 minutes to 10 minutes. As a result, the peak intensity of the temperature-programmed desorption spectrum is further improved and the peak area is increased. Therefore, the detection limit can be further reduced, and a decrease in the degree of vacuum can be suppressed to allow high-accuracy analysis.

  Step S330: The substrate 160 is heated by, for example, the heating device 170 (FIG. 1) or the like to separate one or more substances from the substrate 160. Since the thermal desorption temperature is specific to the substance, the temperature is raised and heated so as to be the thermal desorption temperature of each of one or more substances. This provides a concentrated gas (selective enrichment gas) in which each of the one or more substances to be analyzed is selectively eliminated at each thermal desorption temperature. Briefly, heating may be in the range of each thermal desorption temperature ± 20 K of one or more substances (synonymous in the range of at least -20 K or more of thermal desorption temperature to at least +20 K or less of thermal desorption temperature) More preferably, the heating is performed to the range of the thermal desorption temperature of each of the one or more substances ± 30 K. As a result, an accurate thermal desorption peak can be obtained, so that analysis can be performed with high accuracy. Thermal desorption temperatures specific to rare gas elements such as krypton, argon, neon and volatile organic compounds such as acetone are shown in Table 1 as an exemplary substance to be analyzed.

  Refer to FIG. 4 again. As shown in FIG. 4D, the heating in step S330 heats the region 410 of the substrate 160 to the thermal desorption temperature of the substance to be analyzed (black). Of the two substances freeze-condensed in step S320, the substances to be analyzed are all thermally desorbed from the substrate 160. Since the thermal desorption temperature is intrinsic to the substance, the other substances (white) remain on the substrate 160 without thermal desorption. The result is a selectively enriched gas 420 consisting primarily of the material to be analyzed. That is, although it is desirable that the selective enrichment gas consists of the substance to be analyzed alone, it may contain other substances unavoidable in the analytical range.

  As shown in Table 1, the thermal desorption temperature is usually lower than triple point. Therefore, in practice, prior to step S330, the inside of the vacuum chamber may be evacuated to remove the gas remaining in the vacuum chamber without being freeze condensed. This enables high precision analysis. Subsequently, the substrate 160 can be cooled to a temperature that can be cooled by a cooling device (for example, a number K such as 5 K when a two-stage GM refrigerator is used as the cooling device, a one-stage GM refrigerator) It is good to cool to several tens of K, such as 50 K, and then to perform step S330. Thereby, each of the one or more substances can be surely heated and desorbed at the inherent thermal desorption temperature. In step S330, when the temperature is continuously raised from a cryogenic temperature (eg, several K to several tens of K) to about room temperature, a temperature-programmed desorption spectrum having each thermal desorption peak of one or more substances can be obtained.

  Preferably, in step S330, the substrate 160 is heated from a cryogenic temperature to the thermal desorption temperature of one or more substances at a temperature rising rate of 2 K / min to 8 K / min. Such a heating rate ensures that one or more substances to be analyzed are thermally desorbed from the substrate 160, so that each selectively enriched gas is efficiently obtained.

  Step S340: Analyze mass of one or more substances using a mass spectrometer 183 (FIG. 1). Using a suction tube 181 (FIG. 1) whose aperture diameter at one open end is smaller than the aperture diameter of the other part, suction one or more substances while facing one open end so as not to contact the substrate 160 (FIG. 1) While aspirating with the pipe 181, a part of the one or more substances aspirated with the aspirating pipe 181 is evacuated, and the remainder is analyzed with the mass spectrometer 183.

  The selective enrichment gas obtained in step S330 is aspirated by the aspiration tube 181 and analyzed using the mass spectrometer 183, but the selective enrichment gas is aspirated while the one open end is opposed so as not to contact the substrate. Therefore, the mixture of unnecessary gas desorbed from the place other than the substrate is suppressed, enabling highly accurate analysis. In addition, since the bore diameter of one open end of the suction pipe 181 is smaller than the bore diameter of the other part, exhaust of a part of the selectively concentrated gas sucked by the suction pipe 181 is efficiently performed. As a result, the operable vacuum state of mass analyzer 183 is maintained so that mass analyzer 183 operates and allows analysis.

In step S340, preferably, a portion of each of the one or more substances thermally desorbed in step S330 is evacuated so as to maintain a vacuum state in the range of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻² Pa or less. . This ensures that the mass spectrometer 183 operates.

  In step S340, preferably, the suction pipe 181 is opposed to the substrate 160 such that the distance between one opening end of the suction pipe 181 and the substrate 160 (FIG. 1) is in the range of more than 0 mm and 3 mm or less. Thereby, even when the selective concentration gas from substrate 160 is sucked, the temperature rise and the vacuum degree fluctuation by the heat radiation do not substantially affect mass spectrometer 183, so that it can be surely analyzed. .

  In step S340, more preferably, the suction pipe 181 is opposed to the substrate 160 such that the distance between one open end of the suction pipe 181 and the substrate 160 is in the range of 0.5 mm or more and 1 mm or less. As a result, even in the case where the selective concentration gas is sucked, the temperature rise due to heat radiation is surely suppressed and the degree of vacuum is reduced, so that analysis can be performed with high accuracy. Further, since there is a distance of 0.5 mm or more, even if the support 150 is deformed due to cooling and heating, the suction pipe 181 does not collide with the substrate 160 and break.

  In step S340, preferably, mass spectrometer 183 measures a thermal desorption spectrum having thermal desorption peaks of each of the thermally desorbed one or more substances. Mass spectrometry of each of the one or more substances is performed based on the temperature-programmed desorption spectrum obtained. Such a temperature programmed desorption spectrum can be easily obtained by using a conventional mass spectrometer 183. More preferably, mass spectrometry is performed by calculating the peak area of the thermal desorption spectrum. Such calculation may be performed manually or may be performed by a control unit provided with a CPU.

  FIG. 5 is a view schematically showing freeze condensation and selective enrichment gas by preliminary freeze condensation.

  Referring to FIG. 4, the freeze condensation in step 320 is shown to be performed only once for the introduced gas consisting of a plurality of substances, but the present invention is not limited thereto. Step S320 preliminarily freeze-condenses at least a part of the introduced plurality of substances, which is different from the one or more substances to be analyzed (referred to as removal substance for simplicity) It is also good. The preliminary freeze-condensation ensures that a selectively enriched gas that is not affected by the removal material is obtained if the thermal desorption temperature of each of the one or more materials to be analyzed is lower than that of the removal material. It is valid.

  As shown in FIG. 5A, the partial region 510 of the substrate 160 is higher than the highest thermal desorption temperature among the thermal desorption temperatures of one or more of the substances, and the removal material has Cool to a temperature below the thermal desorption temperature.

  Next, as shown in FIG. 5 (B), a gas comprising one or more substances (black) to be analyzed and a removal substance (white) is introduced. Here, for the sake of simplicity, one or more substances to be analyzed and one substance to be removed are each one. That is, the gas consisting of a plurality of substances is made of two kinds of substances. In addition, the thermal desorption temperature of the removal material is higher than that of the one or more materials to be analyzed.

  When the gas is introduced, only the removal substance of the two substances freezes and condenses on the area 510 of the substrate 160 as shown in FIG. 5 (C). Here, the substance to be analyzed has not yet been freeze-condensed.

  Next, as shown in FIG. 5D, the other region 520 of the substrate 160 is cooled to a temperature equal to or lower than the lowest thermal desorption temperature among the thermal desorption temperatures of one or more of the substances. Since the remaining gas is substantially only one or more substances to be analyzed, as shown in FIG. 5E, only one or more substances are frozen and condensed in another region 520 of the substrate 160. be able to.

  As shown in FIG. 5F, the heating in step S330 causes another region 520 of the substrate 160 to be heated to the thermal desorption temperature of the substance to be analyzed (black), and the freeze-condensed analysis. The substance to be removed is all thermally desorbed from another area 520 of the substrate 160. As a result, a selectively enriched gas 530 consisting only of the substance to be analyzed is obtained.

  Since the selective enrichment gas 530 obtained in this manner performs preliminary freeze-condensation of the removal material, the removal material contained is more effective than, for example, the selective concentration gas 420 shown in FIG. 4 (D). As little as possible. Mass spectrometric analysis of such a selectively enriched gas 530 enables highly accurate analysis.

  It is also possible to carry out preliminary freeze-condensing multiple times to pre-freeze freeze-condens two or more substances and remove two or more effects.

  As described above, the gas analyzer 100 according to the present invention and the cryofocus-GC-MS represented by the above-mentioned non-patent document 1 are examples of the gas analyzer 100 according to the present invention for separating substances by gas chromatography. The apparatus configuration is completely different in that the substance separation is performed using the thermal desorption temperature unique to the substance, and naturally, the mass spectroscope 180 essential for freeze condensation-thermal desorption analysis is not provided. Please note.

  Further, the gas analysis apparatus 100 according to the present invention and the cryogenic TPD apparatuses represented by the non-patent documents 2 and 3 described above have a configuration in which the gas analysis apparatus according to the present invention is specialized for gas analysis. It should be noted that the device configuration differs in that the low temperature TPD device does not include the mass analysis mechanism 180.

  Furthermore, as far as the apparatus configuration is different, it is obvious that the procedure of the gas analysis method according to the present invention is, of course, also different from that of cryofocus-GC-MS and cryogenic TPD apparatuses.

  The gas analyzer 100 and the gas analysis method of the present invention perform low temperature condensation-temperature programmed desorption analysis, but as described above, even if the gas is composed of a plurality of substances (components), each substance In the separation of the substrate, it is only necessary to control the temperature of the substrate surface by utilizing the thermal desorption temperature specific to the substance. Since the separation of each substance is easily performed, a temperature-programmed desorption spectrum having a thermal desorption peak corresponding to the number of gas species can be obtained, and mass spectrometry can be performed from each thermal desorption peak.

  Furthermore, in the gas analysis apparatus 100 and the gas analysis method of the present invention, separation of different molecular species having the same molecular weight is also possible. If thermal species have the same molecular weight but are different molecular species, the thermal desorption temperature is different, so that a temperature-programmed desorption spectrum having thermal desorption peaks at different temperatures is obtained. Both acetone and propionaldehyde contained in exhaled breath have a molecular weight of 58, but if the gas analyzer 100 and gas analysis method of the present invention are employed, the thermal desorption peak of m / z = 58 at different temperatures is obtained. The temperature rising desorption spectrum is easily obtained.

  Furthermore, in the gas analysis apparatus 100 and the gas analysis method of the present invention, as described above, gas chromatography is not required, and gas separation can be performed simply by controlling the temperature of the substrate 160. Therefore, not only the apparatus can be simplified but also smaller than cryofocus-GC-MS. In addition, since the operation of the device is simplified, skilled skills and knowledge are not required.

  Next, the present invention will be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples.

Example 1
In Example 1, a specific gas analyzer of the present invention was configured.
FIG. 6 is a schematic view of the gas analyzer of the present invention constructed in the first embodiment.

The gas analyzer of Example 1 has an introduction pipe for introducing a gas having a variable leak valve 13 and an ultra-high vacuum (UHV) chamber 14 (base pressure: 7 × 10 ⁻ ) provided with a first vacuum pump 12. ⁹ Pa), Gifford McMahon type closed cycle He mechanical refrigerator 1 to 3 (Iwatani, HE05, compressor 1, flexible tube 2, refrigerator 3) connected to the UHV chamber 14, and mechanical refrigerator 3 And heat the zinc oxide single crystal substrate 7 mounted on the tip of the heat transfer rod 5 of the support and the support comprising the cold head 15 and the heat transfer rod 5 disposed in the UHV chamber 14 As a heating device, a resistance heating device (heater) 17 and a mass analysis mechanism 610 connected to the UHV chamber 14 were provided. The substrate 7 was an oxygen-terminated (0001) plane substrate, and had a size of 10 mm × 10 mm × 0.5 mm.

  The mass analysis mechanism 610 evacuates a part of the one or more substances sucked by the suction pipe 620 and the suction pipe 620 for sucking one or more substances to be analyzed which are separated from the substrate 7 by the heater 17; Quadruple mass spectrometer (manufactured by AMETEK, Dycor) equipped with a second vacuum pump 11 for maintaining the inside of the mass analysis mechanism 610 in a vacuum state, and an electron multiplier for analyzing the mass of one or more substances not evacuated. 10 and further equipped. The suction tube 620 is made of stainless steel having an emissivity of 0.35 (1 μm).

  The suction tube 620 was disposed with its one open end 9 facing the substrate 7 and was movable by the moving device 8 so as to be close to the substrate 7 in the horizontal direction with respect to the paper surface. The suction tube 620 had a tapered shape so that the bore diameter of one open end 9 was 6 mm and smaller than the bore diameter (25.4 mm) of the other part of the suction tube 620. The ratio of the aperture of the other part to the aperture of one open end 9 was 4.2. The tube thickness of one open end having a tapered shape was thicker than that of the other part.

  The gas analyzer of Example 1 further includes a Si diode temperature sensor 16 (manufactured by LakeShore, DT-670-SD-1.4H) at the tip of the heat transfer rod 5 so that the temperature of the substrate 7 can be measured. . The gas analyzer of Example 1 further includes a manipulator 4 which moves a support composed of the cold head 15 and the heat transfer rod 5 in the x, y and z directions and rotates as a movement mechanism. In the vicinity of the substrate 7, a tungsten filament 6 for cleaning the surface of the substrate 7 was installed.

  In the gas analyzer of the first embodiment, the UHV chamber 14 is provided with a viewing port, and the manipulator 4 and the moving device 8 are operated while being viewed.

The gas analyzer of Example 1 was used to examine the influence of the distance between the substrate 7 and the suction tube 620 on temperature and pressure. First, the UHV chamber 14 was evacuated to 1 × 10 ⁻⁷ Pa by the first vacuum pump 12. Next, the substrate 7 was cooled to 18.6 K by the mechanical refrigerators 1 to 3. Next, He gas was introduced at a partial pressure of 7 × 10 ⁻⁴ Pa from the introduction pipe via the variable leak valve 13. The suction pipe 620 was moved by the moving device 8, and changes in temperature and pressure when the distance between the substrate 7 and one open end 9 of the suction pipe 620 was changed were examined. The temperature of the substrate 7 was measured by a Si diode temperature sensor 16. The pressure was measured by a vacuum gauge provided in the quadrupole mass spectrometer 10. The results are shown in FIG.

  FIG. 7 is a view showing the influence of the distance between the substrate and the suction tube on the temperature and pressure according to Example 1.

  According to FIG. 7, the temperature did not increase significantly as the distance between the substrate and the suction tube approaches 0.5 mm. This suggests that the heat radiation was suppressed because the thickness of one open end of the suction pipe was thicker than that of the other part. The pressure showed a tendency to decrease when the distance was 3 mm or less. From this, it is preferable that the distance between the one open end 9 and the substrate 7 be in the range of more than 0 mm and 3 mm or less, because temperature rise and vacuum fluctuation due to heat radiation do not substantially affect the mass analyzer. It can be said.

The pressure tended to decrease further when the distance was 1 mm or less. In particular, when the distance was 0.5 mm, the pressure was reduced to 1/20 of the introduced pressure (7 × 10 ⁻⁴ Pa), and it was found that the pressure rise was significantly suppressed. From this, it can be said that the range of 0.5 mm or more and 1 mm or less is particularly preferable as the distance between the one open end 9 and the substrate 7.

  In the following examples and comparative examples, the experiment was performed with the distance between one open end 9 and the substrate 7 in the range of 0.5 mm or more and 1 mm or less.

Example 2
In Example 2, the gas analysis method of the present invention was performed using the gas analyzer of Example 1, and mass analysis of ⁸⁴ Kr (krypton) in the atmosphere was performed. That is, a plurality of materials constituting the atmosphere _is a _{N 2, O 2, CO 2} , H 2, H 2 O and ⁸⁴ Kr, these one or more substances to be analyzed ^was 84 Kr .

The UHV chamber 14 was evacuated to 1 × 10 ⁻⁷ Pa by the first vacuum pump 12 (Step S 310 in FIG. 3). After evacuation, the compressors 1 of the mechanical refrigerators 1 to 3 were started to cool the substrate 7 to 6K. The temperature of the substrate 7 was measured by a Si diode temperature sensor 16. Next, flash heating was performed by electron impact heating using a tungsten filament 6 to clean the surface of the substrate 7. Cleaning was performed by repeating heating for 1 minute at a temperature of 600 ° C. three times.

After confirming that the substrate 7 has been cooled to 6 K, the atmosphere containing ⁸⁴ Kr of various concentrations as a sample gas is introduced from the introduction pipe into the UHV chamber 14 through the variable leak valve 13, and The gas was freeze condensed (step S320 in FIG. 3). The concentrations of ⁸⁴ Kr were 0.65 ppm, 0.94 ppm, 1.93 ppm, 9.77 ppm and 14.9 ppm. ^The partial pressure at the time of introduction of ⁸⁴ Kr was 1 × 10 ⁻² Pa, and the retention time was 20 seconds, 1 minute, 3 minutes and 10 minutes. ^Since the triple point of ⁸⁴ Kr is 115.8 K (Table 1), it was confirmed that the substrate 7 was cooled to a temperature equal to or less than the triple point of ⁸⁴ Kr.

Next, the substrate 7 was heated by the heater 17, and the freeze-condensed gas was heated and desorbed (Step S330 in FIG. 3). The mass of the desorbed gas was analyzed using the quadrupole mass spectrometer 10 (step S340 in FIG. 3). Specifically, one open end 9 of the suction tube 620 was opposed by the manipulator 4 and the moving device 8 so as not to contact the substrate 7. At this time, the distance between the suction pipe 620 and the substrate 7 was in the range of 0.5 mm or more and 1 mm or less. The desorbed gas is suctioned by the suction pipe 620, a part of the desorbed gas suctioned by the suction pipe 620 is exhausted by the second pump (differential exhaust pump) 11, and the remainder is quadrupled. The polar mass analyzer 10 was analyzed. At this time, the degree of vacuum in the mass analysis mechanism 610 was 1 × 10 ⁻² Pa or less.

Here, assuming that the thermal desorption temperature of ⁸⁴ Kr to be analyzed is unknown, the substrate 7 is heated from 6 K to 290 K at a heating rate of 5 K / min, and N ₂ , O ₂ , CO ₂ , H ₂ , The quadrupole mass spectrometer 10 was analyzed for each m / z of H ₂ O and ⁸⁴ Kr to obtain a thermal desorption spectrum. The results are shown in FIGS.

FIG. 8 is a diagram showing a temperature-programmed desorption spectrum when freeze-condensing an atmosphere containing ⁸⁴ Kr 0.65 ppm according to Example 2 at 6 K for 1 minute.

FIG. 8 (a) is a temperature-programmed desorption spectrum of ⁸⁴ Kr, and FIG. 8 (b) is a temperature-programmed desorption spectrum of N ₂ , O ₂ , CO ₂ , H ₂ and H ₂ O. The thermal desorption spectrum of ⁸⁴ Kr in FIG. 8 (a) shows several thermal desorption peaks, but the thermal desorption peak near 60 K is N ₂ (m / m in the atmosphere of FIG. 8 (b). Temperature-programmed desorption of z = 28), O ₂ (m / z = 32), CO ₂ (m / z = 44), H ₂ (m / z = 2) and H ₂ O (m / z = 18) It was not seen in the spectrum. From this, the thermal desorption peak around 60 K is not due to the desorption of the main components (N ₂ , O ₂ , CO ₂ , H ₂ and H ₂ O) in the air, but due to the desorption of ⁸⁴ Kr The thermal desorption temperature of ⁸⁴ Kr was found to be 60 K.

From the above, in the freeze condensation-temperature programmed desorption analysis by the gas analysis apparatus and the gas analysis method of the present invention, ⁸⁴ Kr contained in the atmosphere in an extremely small amount is released at 60 K ± 30 K from its peak width. It was confirmed that ⁸⁴ Kr to be analyzed was able to obtain a selectively enriched gas (selectively enriched gas), and it was found that mass spectrometry could be performed using a thermal desorption peak at 60K ± 30K.

FIG. 9 is a view showing the relationship between the concentration of ⁸⁴ Kr obtained from the thermal desorption peak and the ion current obtained by freezing and condensing the atmosphere containing ⁸⁴ Kr of various concentrations according to Example 2 at 6 K for 1 minute. .

^Since the thermal desorption peak of ⁸⁴ Kr is obtained near 60 K, the result of measuring the thermal desorption spectrum for the range of 40 K to 80 K is shown in the inset. The peak intensity of the thermal desorption peak increased with the increase of the ⁸⁴ Kr concentration, and the peak position was shifted to the low temperature side. The shift of the peak position is considered to be due to the thermal desorption occurring at a lower temperature due to the increase of the ⁸⁴ Kr interaction in the freeze-condensed gas as the ⁸⁴ Kr concentration increases.

The peak intensity and peak area (corresponding to the ion current) of each thermal desorption peak in the obtained temperature-programmed desorption spectrum were determined from fitting with a Gaussian distribution curve. The peak area thus determined was plotted against the ⁸⁴ Kr concentration, and as shown in FIG. 9, it was found that the ⁸⁴ Kr concentration and the ion current (signal strength) were in a linear relationship. This result was in good agreement with the increase in peak intensity in the inset.

  From the above, in the freeze condensation-temperature programmed desorption analysis according to the gas analysis apparatus and gas analysis method of the present invention, the concentration of the selectively concentrated gas is one or more substances to be analyzed in the gas introduced into the vacuum chamber. It was shown to be proportional to the concentration of This is advantageous for the calculation of the concentration if the relationship between the concentration of the substance to be analyzed and the ion current is stored in advance in the control unit or the like as a calibration curve.

FIG. 10 is a view showing the relationship between the freeze-condensing time and the ion current obtained from the thermal desorption peak when freeze-condensing the atmosphere containing ⁸⁴ Kr 0.65 ppm according to Example 2 at 6 K for various times.

^Since the thermal desorption peak of ⁸⁴ Kr is obtained near 60 K, the result of measuring the thermal desorption spectrum for the range of 40 K to 80 K is shown in the inset. The peak intensity of the thermal desorption peak increased with the increase of the freeze condensation time.

  The peak intensity and peak area of each thermal desorption peak in the obtained temperature-programmed desorption spectrum were determined from fitting with a Gaussian distribution curve. When the peak area thus determined was plotted against the freeze condensation time (low temperature condensation time), as shown in FIG. 10, it was found that the freeze condensation time and the ion current (signal strength) had a linear relationship. This result was in good agreement with the increase in peak intensity in the inset.

In addition, in the freeze condensation-temperature programmed desorption analysis by the gas analysis device and the gas analysis method of the present invention, it is shown that the detection lower limit of the quadrupole mass spectrometer 10 is improved along with the freeze condensation time. For example, according to the result of freeze condensation for 10 minutes in FIG. 10, the detection limit of ⁸⁴ Kr was calculated to be 0.03 ppm. This value was improved by one digit as compared to the lower limit of detection (0.3 ppm) shown in Comparative Example 3 described later, and it was confirmed that highly accurate analysis could be performed.

  From FIG. 10, if the freeze condensation time is 20 seconds or more and 15 minutes or less, mass analysis is possible, but in high precision analysis, in particular, the freeze condensation time is preferably 1 minute or more and 15 minutes or less, and further advanced In the analysis, it was confirmed that the freezing and condensing time is desirably 3 minutes or more and 10 minutes or less.

Comparative Example 3
In Comparative Example 3, mass analysis of ⁸⁴ Kr (krypton) in the atmosphere was performed without using freeze condensation-temperature programmed desorption, although the gas analyzer of Example 1 is used. Here, the concentration of ⁸⁴ Kr was 0.65 ppm.

In the measurement, the atmosphere was introduced into the UHV chamber 14 so that the partial pressure was 1 × 10 ⁻² Pa, and the mass analysis of ⁸⁴ Kr was performed by the quadrupole mass spectrometer 10 as it is. The dwell time at each point in the scan was 0.5 seconds. The results are shown in FIG.

  FIG. 11 is a diagram showing a mass spectrum according to Comparative Example 3.

According to the fact that the concentration of ⁸⁴ Kr in the atmosphere is 0.65 ppm and the peak signal-to-noise ratio near the peak at m / z = 84, ⁸⁴ Kr is not determined by freeze condensation-temperature desorption analysis. The lower detection limit of was found to be 0.3 ppm. As described in the second embodiment, the lower limit of detection can be reduced by adopting freeze condensation-thermal desorption analysis by the gas analysis device and gas analysis method of the present invention, so that highly accurate gas analysis is possible. It has been shown.

Example 4
In Example 4, the gas analysis method of the present invention was carried out using the gas analysis device of Example 1, and mass spectrometry of acetone was performed as one or more substances to be analyzed. The gas introduced into the UHV chamber 14 is atmospheric air (partial pressure: 1 × 10 ⁻² Pa), atmospheric air (partial pressure: 1 ppm, acetone, 1 ppm, 3 ppm, 10 ppm, 30 ppm and 100 ppm). It was 1 × 10 ⁻² Pa) and acetone (partial pressure: 1 × 10 ⁻⁶ Pa). The gas analysis was performed in the same manner as in Example 2 except that the cooling temperature of the substrate 7 was 50 K and the freeze condensation time was 1 minute. The results are shown in FIG. 12 and FIG.

  FIG. 12 is a diagram showing a temperature-programmed desorption spectrum when air containing 100 ppm of acetone, acetone, and the air according to Example 4 are freeze-condensed at 50 K for 1 minute.

  FIG. 12 (a) shows the temperature-programmed desorption spectrum (solid line) of the atmosphere containing 100 ppm of acetone and the temperature-programmed desorption spectrum (dotted line) of acetone, and FIG. 12 (b) shows the temperature programmed desorption of the atmosphere. It is a figure which shows an emission spectrum.

  According to FIG. 12 (a), the thermal desorption spectrum of the acetone-containing atmosphere had a thermal desorption peak at about 145 K, and the thermal desorption spectrum of acetone had a thermal desorption peak at about 125 K, All thermal desorption peaks were completely matched between m / z 43 and 58. From this, although the thermal desorption temperature was different, any thermal desorption peak could be identified as by acetone.

  As shown in FIG. 12 (b), according to the temperature programmed desorption spectrum for the main component in the air, the thermal desorption peak of water was the sharpest at about 145 K among the main components. From this, it is suggested that the thermal desorption peak of acetone in the acetone-containing atmosphere is affected by the water contained in the atmosphere, induced by the temperature-programmed desorption of water, and acetone is also temperature-programmed and desorbed. Be done. That is, the thermal desorption peak at about 145 K can be said to be a selectively concentrated gas consisting of acetone and water.

  FIG. 13 is a view showing the relationship between the acetone concentration and the ion current obtained from a temperature-programmed desorption spectrum when freeze-condensing the atmosphere containing acetone at various concentrations according to Example 4 at 50 K for 1 minute.

  The thermal desorption spectra of the acetone-containing atmosphere at each concentration all had thermal desorption peaks at about 145 K for m / z 43 and 58. The peak intensity and peak area (corresponding to the ion current) of the thermal desorption peak of each concentration were determined from fitting with a Gaussian distribution curve. When the peak area thus determined was plotted against the acetone concentration, it was found that the acetone concentration and the ion current (signal intensity) had a linear relationship. Also, the slope of the linear relationship where m / z is 43 was about 7 times as large as that of 58. This result was similar to the existing mass spectrum database (eg, NIST Chemistry Webbook http://webbook.nist.gov/chemistry).

The results in FIG. 13 show the same tendency as the ⁸⁴ Kr results described with reference to FIG. 9, and in the freeze condensation-thermal desorption analysis by the gas analysis device and gas analysis method of the present invention, selective concentration The concentration of the gas was shown to be proportional to the concentration of one or more substances to be analyzed in the gas introduced into the vacuum chamber. It has been found that the gas analyzer and gas analysis method of the present invention are effective for acetone analysis in exhaled breath. Also, the thermal desorption peak at about 145 K is affected by water in the atmosphere, and the selective enrichment gas contains acetone and water, but the selective enrichment gas is mainly the substance to be analyzed (here Then, it was found that gas analysis was possible if it contained acetone).

[Example 5]
In Example 5, the gas analysis method of the present invention, in particular, preliminary freeze-condensation, was carried out using the gas analyzer of Example 1, and mass spectrometry of acetone was performed as one or more substances to be analyzed.

  In Example 4, it was explained that the thermal desorption peak of acetone is affected by the thermal desorption of water in the thermal desorption spectrum of the acetone-containing atmosphere. In Example 5, the effect on the thermal desorption of acetone by preliminary freeze-condensing water was investigated.

Describe the specific procedure. The UHV chamber 14 was evacuated to 1 × 10 ⁻⁷ Pa by the first vacuum pump 12. After evacuation, the compressors 1 of the mechanical refrigerators 1 to 3 were started to cool the substrate 7 to 145K. The temperature of the substrate 7 was measured by a Si diode temperature sensor 16. Next, the atmosphere containing 100 ppm of acetone was introduced from the introduction pipe into the UHV chamber 14 through the variable leak valve 13 to preliminarily freeze and condense only water in the gas on the substrate 7. Here, the partial pressure at the time of introduction of the acetone-containing atmosphere was 1 × 10 ⁻² Pa, and the holding time was 1 minute. As shown in Table 1, 145 K was a temperature higher than the triple point of acetone and less than the thermal desorption temperature of water.

After 1 minute, the inside of the UHV chamber 14 was evacuated and the substrate 7 was cooled to 50K. Next, the substrate 7 was heated by the heater 17 to 260 K at a temperature rising rate of 5 K / min, and the freeze-condensed gas was heated and desorbed. The results analyzed by the quadrupole mass spectrometer 10 for each m / z of H ₂ O and acetone are shown in FIG.

  FIG. 14 is a diagram showing a temperature-programmed desorption spectrum when freeze-condensing the atmosphere containing 100 ppm of acetone according to Example 5 at 145 K for 1 minute.

  FIG. 14 (a) is the temperature-programmed desorption spectrum obtained in Example 4, and relates to water (m / z = 18) and acetone (m / z = 58), respectively. FIG. 14 (b) is the temperature-programmed desorption spectrum obtained in Example 5, and relates to water (m / z = 18) and acetone (m / z = 58), respectively. From Fig. 14 (a), the intensity ratio of acetone to water (acetone / water) when freeze-condensed at 50K is 25.9, and from Fig. 14 (b), acetone and water when freeze-condensed at 145K And the intensity ratio (acetone / water) to it were 2.8. In other words, it was found that both acetone and water were efficiently freeze-condensed at 50 K of freeze aggregation, but water was overwhelmingly much more freeze condensed than at acetone at 145 K freeze condensation. .

  From this, as preliminary freeze-condensation, if water is frozen and condensed at 145 K and then acetone containing air from which water is removed is frozen and condensed at 50 K, the effect of water is eliminated, selective concentration consisting only of acetone It was confirmed that the gas could be obtained reliably and highly accurate gas analysis could be performed.

  The gas analysis apparatus and the gas analysis method of the present invention can perform mass analysis of trace components in a gas such as exhaled breath and air by freeze condensation-thermal desorption analysis. In particular, even if there are multiple trace components, they can be easily separated simply by freeze-condensing and heating to a unique temperature rising desorption temperature, and they do not require expert skills or specialized knowledge, so versatility is Extremely expensive. Since the existing gas chromatography is not required, the apparatus is not only simple but can be made small, so the versatility is high.

DESCRIPTION OF SYMBOLS 100 Gas analyzer 110 Introductory pipe 120, 12 1st vacuum pump 130, 14 Vacuum chamber 140 Cooling device 150 Support body 160, 7 Substrate 170, 17 Heating device 180, 610 Mass spectroscope 181, 620 Suction pipe 182, 11 Two vacuum pumps 183, 10 Mass analyzer 210, 9 Open end 220 Non-open end of suction tube 420, 530 Selectively condensed gas 1 Compressor 2 Flexible tube 3 Refrigerator 4 Manipulator 5 Heat transfer rod 6 Tungsten filament 8 Movement Device 13 Variable leak valve 15 Cold head 16 Si diode temperature sensor

Claims (27)

A gas analyzer that analyzes the mass of one or more substances out of a gas composed of a plurality of substances, comprising:
A vacuum chamber having an inlet pipe for introducing the gas and comprising a first vacuum pump;
A cooling device connected to the vacuum chamber;
A support connected to the cooling device and disposed in the vacuum chamber, on which a substrate for freezing and condensing at least one or more substances of the gas introduced by the cooling device is placed When,
A heating device for heating the substrate placed on the support;
A mass spectrometry mechanism connected to the vacuum chamber;
The mass spectrometry mechanism is
A suction pipe for suctioning the one or more substances detached from the substrate by the heating device;
A second vacuum pump for evacuating a part of the one or more substances sucked by the suction pipe and maintaining the inside of the mass analysis mechanism in a vacuum state;
And a mass analyzer for analyzing the mass of the one or more substances not evacuated.
The suction tube is disposed such that one open end thereof faces the substrate, and is movable so as to be close to the substrate,
The gas analyzer according to claim 1, wherein the suction pipe has a tapered shape such that the diameter of the one open end is smaller than the diameter of the other portion of the suction pipe.   The gas analyzer according to claim 1, wherein a ratio of a diameter of the other portion of the suction pipe to a diameter of the one open end is in a range of 2.5 or more and 5.5 or less.   The gas analyzer according to claim 1, wherein the diameter of the one open end is in the range of 5 mm to 7 mm.   The gas analyzer according to claim 1, wherein a tube thickness of the one open end having the tapered shape is thicker than that of the other portion. The gas analyzer according to claim 1, wherein the second vacuum pump maintains the inside of the mass analysis mechanism in a vacuum state in a range of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻² Pa or less.   The gas analyzer according to claim 1, further comprising a moving mechanism that moves and rotates the support in the x, y and z directions.   The movement of the support by the moving mechanism and / or the suction tube such that the surface of the substrate placed on the support and the end face of the one open end of the suction tube face in parallel. The gas analyzer according to claim 6, further comprising a control unit that controls movement.   The gas analyzer according to claim 6, wherein the control unit controls the moving mechanism and / or the suction pipe such that a distance between the one open end and the substrate is in a range of more than 0 mm and 3 mm or less. .   The gas analysis according to claim 8, wherein the control unit controls the moving mechanism and / or the suction pipe such that a distance between the one open end and the substrate is in a range of 0.5 mm to 1 mm. apparatus.   The gas analyzer according to claim 1, wherein the cooling device is a mechanical refrigerator or a cryogen.   The gas analyzer according to claim 1, wherein the heating device is selected from the group consisting of a resistive heating device, an infrared heating device and an electron impact heating device.   The gas analyzer according to claim 1, further comprising a control unit that controls the operation of a heating device that heats the substrate.   The gas analyzer according to claim 1, wherein the mass analyzer is selected from the group consisting of a quadrupole mass analyzer, a time of flight mass analyzer, and a cyclotron resonance mass analyzer.   The gas analyzer according to claim 1, wherein the support comprises a cold head and a heat transfer bar, and the substrate is mounted on the tip of the heat transfer bar. The gas analyzer according to claim 1, wherein the first vacuum pump maintains the vacuum chamber in a vacuum state of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻¹ Pa or less. A method of gas analysis for analyzing the mass of one or more substances out of a gas composed of a plurality of substances, comprising:
Evacuating the inside of the vacuum chamber;
The substrate located in the vacuum chamber is cooled to a temperature not higher than the triple point of the at least one of the one or more substances, the gas is introduced into the vacuum chamber, and the substrate is placed on the substrate Freezing and condensing the above substances;
Heating the substrate to desorb each of the one or more substances from the substrate;
Analyzing the mass of the one or more substances using a mass spectrometer, using a suction tube whose aperture of one open end is smaller than the aperture of the other part, the one open end being the substrate While suctioning the one or more substances in the suction pipe while facing each other so as not to come into contact with the other, exhaust some of the one or more substances sucked in the suction pipe, and analyze the rest with a mass spectrometer , Steps and methods. ^17. The method of claim 16, wherein the analyzing step evacuates a portion of the one or more materials to maintain a vacuum in the range of 1 x ^10-8 Pa to 1 x ^10-2 Pa. In the freezing and condensing step, the gas is introduced at a partial pressure in the range of 1 × 10 ⁻⁸ Pa or more and 1 × 10 ⁻¹ Pa or less, and freeze-condensed for a time in the range of 30 seconds or more and 15 minutes or less. The method according to 16.   The method according to claim 16, wherein the step of freezing and condensing cools the substrate to a temperature equal to or lower than the lowest thermal desorption temperature of the thermal desorption temperatures of each of the at least one substance.   The method according to claim 16, wherein the analyzing step makes the suction pipe face the substrate such that the distance between the one open end of the suction pipe and the substrate is in the range of more than 0 mm and 3 mm or less. .   The method according to claim 16, wherein the analyzing step measures a temperature-programmed desorption spectrum of each of the one or more substances, and analyzes a mass of each of the one or more substances from the respective temperature-programmed desorption spectrum. .   22. The method according to claim 21, wherein the analyzing step calculates peak areas in the respective temperature programmed desorption spectra.   17. The method of claim 16, wherein the freeze-condensing step further comprises preliminary freeze-condensing at least a portion of the plurality of materials different from the one or more materials. The preliminary freezing and condensing step comprises
At least a portion of the substrate is higher than the highest thermal desorption temperature among the thermal desorption temperatures of each of the one or more substances, and at least the plurality of substances different from the one or more substances Cooling to a temperature equal to or lower than a thermal desorption temperature of a part, and freezing and condensing the at least a part on the part of the substrate;
Cooling another region of the substrate to a temperature below the lowest thermal desorption temperature of the thermal desorption temperature of each of the one or more materials, and transferring the one or more materials to the other region of the substrate 24. The method of claim 23, further comprising: freezing and condensing.   The method according to claim 16, wherein the desorption step heats the substrate at a temperature rising rate of 2 K / min to 8 K / min for each thermal desorption temperature range of ± 20 K of the one or more substances. the method of.   17. The method of claim 16, wherein the one or more materials are selected from the group consisting of volatile organic compounds, noble gas elements and air pollutants.   17. The method of claim 16, wherein the substrate is selected from the group consisting of oxide single crystals, polycrystalline metals, single crystal metals, single crystal semiconductors and layered materials.