JP2004061321A - Method and apparatus for analyzing trace impurities in gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an analysis method and an analysis apparatus of a very small quantity of impurity that can be analyzed at a higher precision. <P>SOLUTION: In the analysis method of the very small quantity of impurity in a gas using a mass spectroscope for separating the very small quantity of impurity in a sample gas by a separation column 2 of a gas chromatograph, ionizing the very small quantity of impurity at an ion source section 19, and separating mass, pressure in the ion source section 19 from the separation column 2 is kept higher than an atmospheric pressure for analysis. <P>COPYRIGHT: (C)2004,JPO

Description

【００２６】
表１に示した結果から、大気圧よりも高い圧力とすることにより、水分ブランク濃度が著しく減少することがわかった。
【００２７】
ついで、７．２ｐｐｂの水素不純物を含む窒素ガスについて、１０回繰り返して分析した際の繰り返し精度を表２示した。変動係数が小さく、良好な繰り返し精度であることが確認できた。この様に繰り返し精度が良好であることから、水分ブランクの影響が低減されていることが推測できた。
【００２８】
【表２】

【００２９】
また、分離カラム２からイオン源部１９内の圧力を変化させたときの水素のピーク強度を、図２にグラフで示した。測定圧力範囲内においては圧力をかける程、ピーク強度が向上し、感度が向上することが確認できた。
また、イオン源部１９内の圧力が０のときと、０．０６ＭＰａＧの場合のクロマトグラフを図３に示した。大気圧よりも大きな圧力とすることにより、大気圧の場合と比べて、ピーク強度が増大し、検出下限は数倍となり、感度が大きく増大した。
【００３０】
以上の実験の結果より、分離カラム２からイオン源部１９の圧力を大気圧よりも高くするという簡便な手法によって、微量不純物の検出感度が大幅に向上し、その分析精度が大きく向上することが確認できた。
【００３１】
【発明の効果】
以上説明したように本発明においては、高精度の分析が可能なガス中の微量不純物の分析方法及び装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の分析方法を用いた分析装置の一例を示した系統図である。
【図２】実施例において、イオン源部１９内の圧力を変化させたときの水素のピーク強度を示したグラフである。
【図３】実施例で得られたクロマトグラフを示した図である。
【符号の説明】
１　試料ガス源、
２　分離カラム、
３　ガスクロマトグラフ（ＧＣ）
４　８方ガス切換コック
５　計量管
６　精製ガス源
６ａ　精製ガス流路
７　流量制御装置
７ａ　キャリヤーガス流路
８　流量制御装置
９　メークアップガス経路
１０　分離ガス流出経路
１１　ＧＣ／ＡＰＩＭＳ接続経路
１２　排出分流経路
１３　背圧制御装置（バックプレッシャーレギュレーター）
１４　排出経路
１５　イオン源ガス導入経路
１７　イオン源排気流量制御装置
１８　イオン源排出ガス排出経路[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for analyzing trace impurities in a gas.
[0002]
Problems to be solved by the prior art and the invention
A method and an apparatus for analyzing trace impurities in a gas are used, for example, in the field of semiconductor manufacturing.
In the semiconductor manufacturing field, many gas phase steps are used in a device manufacturing process. The presence of a trace amount of gas impurities in the high-purity bulk gas used in such a gas-phase process adversely affects device performance. Therefore, monitoring and analysis of trace amounts of impurities in the high-purity bulk gas are required.
[0003]
In monitoring and analyzing the impurity concentration in a high-purity gas, for example, a ppb level high sensitivity analyzer is required. Gas chromatography / atmospheric pressure ionization mass spectrometry (GC / APIMS analysis method; APIMS is Atmospheric Pressure Ionization Mass Spectrometer) and the like are known as high sensitivity analysis methods used for such applications.
[0004]
The APIMS ionizes a sample gas under atmospheric pressure, generally by a beta ray emitted from a corona discharge or a radiation source, and can selectively ionize impurities by a subsequent ion-molecule reaction. After the generated ions are separated by mass, they are detected by a secondary electron multiplier or the like.
GC / APIMS was developed to further expand the scope of APIMS. In the GC / APIMS analysis method, first, for example, a few ml of a sample gas is introduced into the GC from a sample gas source, and the sample enters the inlet of the separation column with the carrier gas and passes through the separation column. , The main component gas and each trace impurity are isolated for each substance.
The isolated trace impurities flow out of the separation column outlet together with the carrier gas.
Next, a make-up gas (addition gas) composed of a gas of the same type as the carrier gas is generally introduced into the carrier gas containing a trace amount of impurities flowing out of the separation column, and mixed. The makeup gas is added in order to adjust the amount of gas introduced into a mass spectrometer described later and to stabilize the discharge of the ion source of the mass spectrometer using corona discharge, for example.
As described above, the mixed gas of the carrier gas, the trace impurities, and the makeup gas is introduced into the ion source, and the trace impurities are ionized under the atmospheric pressure. Then, the ionized trace impurities are detected and quantified by the mass spectrometer.
[0005]
However, the conventional GC / APIMS analysis method may have insufficient analysis sensitivity and accuracy. For example, the sensitivity and accuracy of the analysis may differ depending on the type of the trace impurity, and it is difficult to perform the analysis with high accuracy depending on the type of the trace impurity.
Accordingly, it is an object of the present invention to provide a method and an apparatus for analyzing trace impurities in a gas, which enable more accurate analysis.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a first invention is to separate a trace impurity in a sample gas by a separation column of a gas chromatograph, ionize the trace impurity in an ion source part, and perform gas separation using a mass spectrometer for mass separation. In the method for analyzing trace impurities in gas, the analysis is performed while maintaining the pressure of the ion source from the separation column higher than the atmospheric pressure.
According to a second aspect, in the analysis method of the first aspect, the amount of the gas supplied to the mass spectrometer and the amount of the gas discharged from the mass spectrometer are adjusted so that the ions are separated from the separation column. This is a method for analyzing trace impurities in a gas, characterized in that analysis is performed while maintaining the pressure of the source unit higher than the atmospheric pressure.
According to a third aspect, in the analysis method according to the second aspect, an amount of gas exhausted from an exhaust path provided on a downstream side of the ion source unit, an outlet of the separation column, and an inlet of the ion source unit And adjusting both the amount of gas discharged from the discharge path provided between the two.
A fourth invention is based on a back pressure of at least one of a discharge path provided between an outlet of the separation column and an inlet of the ion source section or a discharge path provided at a downstream side of the ion source section. The analysis method according to the third aspect of the invention, wherein an amount of gas supplied to the mass spectrometer and an amount of gas discharged from the mass spectrometer are adjusted.
A fifth invention is directed to a gas chromatograph and a method for analyzing a trace impurity in a gas using a mass spectrometer that ionizes a trace impurity in a sample gas separated by a separation column of the gas chromatograph in an ion source section and performs mass separation. In the device,
An apparatus for analyzing trace impurities in a gas, comprising: a control unit for controlling the pressure of the ion source from the separation column to a pressure higher than the atmospheric pressure.
A sixth invention is characterized in that the control means comprises a flow control means for adjusting an amount of gas supplied to the mass spectrometer, and a flow control means for adjusting an amount of gas discharged from the mass spectrometer. An analyzer according to the fifth aspect of the invention, characterized in that:
In a seventh aspect, a flow rate control means for controlling an amount of gas discharged from the mass spectrometer comprises:
Back pressure control means provided between at least one of a discharge path provided between an outlet of the separation column and an inlet of the ion source unit or a downstream side of the ion source unit,
Flow rate control means for controlling the amount of gas discharged from a discharge path provided on the subsequent stage of the ion source section,
The analyzer according to the sixth aspect of the invention, further comprising: a flow control unit configured to control an amount of gas discharged from a discharge path provided between an outlet of the separation column and an inlet of the ion source unit. is there.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an example of a system diagram of an analyzer used for the analysis method of the present invention. This analyzer is schematically composed of a gas chromatograph (GC) 3 and a mass spectrometer 20 provided on the outlet side thereof.
In addition, the mass spectrometer 20 ionizes the gas introduced into the mass spectrometer 20, exhausts excess gas from the introduced gas, and removes a small amount of ions generated by the ion source 19. A differential pumping section (not shown) for introducing gas into a mass separating section described later; a mass separating section (not shown) for separating the ions by mass (for each type); And a detection unit (not shown) for detecting the position.
[0008]
Inside of the space between the separation column 2 provided in the GC 3 and the ion source unit 19 (that is, the separation column 2, the separation gas outflow path 10, the GC / APIMS connection path 11, the ion source gas introduction path 15, and the ion source unit 19) Can be controlled at a constant pressure higher than the atmospheric pressure by adjusting the amount of gas supplied to the analyzer and the amount of gas discharged from the analyzer.
That is, the pressure inside the analyzer can be made higher than the atmospheric pressure by making the flow rate of the discharged gas smaller than the flow rate of the initially supplied gas (carrier gas, makeup gas, or the like). Although depending on the setting of the pressure and the like, for example, by setting the flow rate of the supplied gas to be 1.1 to 10 times, preferably 1.5 to 3 times the flow rate of the discharged gas, the ion Pressure can be applied to the source 19.
During the analysis, when the pressure inside the analyzer becomes higher than the set initial pressure (set pressure), the amount of gas to be discharged is increased, and the internal pressure becomes lower than the set pressure. In this case, if the amount of gas to be discharged is reduced, the internal pressure can be kept constant at the set pressure even during the analysis. The control of the internal pressure during this analysis is performed, for example, by measuring the back pressure (upstream or primary pressure) of the control unit by a back pressure control device provided in a gas discharge path as described later. It can be performed by controlling the amount of gas discharged based on the value.
[0009]
In the analyzer of this example, the purified gas supplied from the purified gas source 6 passes through the purified gas flow path 6a, and is branched into a carrier gas flow path 7a and a make-up gas path 9 at the tip thereof. The flow control devices (flow control means for adjusting the amount of gas supplied to the analyzer) 7 and 8 control the flow rate of each gas supplied to the analyzer.
The flow rate of the discharged gas is determined by the amount of the gas discharged from the discharge path 14 through the discharge branch path 12 that is branched from the outlet of the separation column 2 to the inlet of the ion source unit 19. The pressure is controlled by a pressure control device (back pressure regulator) 13, and the amount of gas discharged from a discharge path 18 provided on the downstream side (exit side) of the ion source unit 19 is controlled by an ion source exhaust flow control device 17. This can be adjusted. Therefore, in this example, the flow control means for controlling the amount of gas discharged from the mass spectrometer is the back pressure control device 13 and the ion source exhaust flow control device 17, and the back pressure control device 13 controls the back pressure control. It also functions as a means and a gas flow control means for adjusting the amount of gas discharged from the discharge path 14.
In addition, it is preferable that the back pressure control device 13 is provided at a position close to the ion source unit 19 from the viewpoint of pressure adjustment.
[0010]
As described above, the gas is discharged from the discharge paths 14 and 18 provided at the front (inlet side) and the rear (outlet side) of the ion source unit 19, and the amount of gas discharged from each of the discharge paths 14 and 18 is reduced. By controlling the balance, the pressure between the separation column 2 and the ion source 19 can be stably maintained.
Specifically, for example, excess gas excluding the gas introduced into the mass separation unit is discharged from the discharge path 18 connected to the differential exhaust unit of the mass spectrometer 20, and the excess gas is measured by the back pressure control device 13. When the measured value of the back pressure becomes higher than the value of the back pressure capable of holding the internal pressure at the set pressure with reference to the measured value of the back pressure, the discharge path 14 is controlled by the operation of the back pressure control device 13. When the measured value of the back pressure becomes low, the amount of gas to be discharged is reduced.
For example, assuming that the carrier gas flowing through the flow path 10 is 100 cc, the makeup gas flowing through the flow path 9 is 500 cc, and the gas flowing from the ion source 19 of the analyzer into the mass separation unit (not shown) is about 100 cc. The discharge amount from the ion source in the passage 18 is controlled to 400 cc by the flow controller 17 so that the amount of gas supplied to the mass separation unit is increased by 100 cc.
At this time, when the set pressure inside the discharge branch path 12 is controlled as a back pressure by the back pressure control device 13 provided in the discharge branch path 12, the back pressure increases, and when the back pressure exceeds 0.02 MPaG, the back pressure increases. When the flow rate of the gas to be discharged is appropriately increased by the control device 13 so as to maintain the pressure of the upstream discharge branch path 12 at 0.02 MPaG, the pressure in the gas system including the ion source unit 19 can be kept constant. . When the pressure becomes lower than 0.02 MPa, the set pressure can be maintained by lowering the flow rate of the gas to be discharged by the back pressure control device 13.
Note that the back pressure control device 13 can be provided in one or both of the discharge paths 14 and 18.
[0011]
Note that the pressure inside the ion source unit 19 is substantially equal to the value controlled by the back pressure control device 13. The pressures in the separation gas outflow path 10, the GC / APIMS connection path 11, and the ion source gas introduction path 15 are structurally similar to the pressure in the normal ion source 19.
Since the separation column 2 is filled with the separation agent, the pressure in the separation column 2 is higher on the inlet side (the sample gas source 1 side) than on the outlet side (the separation gas outlet path 10 side).
[0012]
At this time, the pressure inside the range from the separation column 2 to the ion source unit 19 is set to 0.005 MPaG or more, preferably 0.01 MPaG or more.
If it is less than 0.005 MPa, the effect of improving the accuracy of analysis may not be obtained.
The upper limit is not particularly limited, and various parameters such as the pressure resistance of equipment such as a mass flow controller provided in the measurement device, the pressure resistance of the mass spectrometer, and the capacity of the exhaust pump for maintaining the mass separation unit of the mass spectrometer under the specified vacuum. It can be determined by conditions. Generally, it is, for example, 1 MPa or less, preferably 0.3 MPaG or less.
In addition, although it depends on the amount of water in the measurement system and the like, the effect is usually obtained at 0.3 MPa or less. More preferably, it is desirable to be less than 0.13 MPa.
[0013]
In order to optimize the sensitivity of a trace impurity to be analyzed (high sensitivity), it is preferable to select an optimal flow rate, pressure, and the like. In other words, the condition that provides the highest sensitivity may differ depending on the type of the trace impurity.
In automatic analysis, etc., control is performed so that set values such as flow rate and pressure are set to optimal values for each type of trace impurities, and analysis is performed for each trace impurity with the highest sensitivity at all times. It is also possible to use a control device that performs the control.
[0014]
Hereinafter, an example of the analysis method will be described following the measurement operation.
First, the flow rate control devices 7 and 8 for controlling the flow rate of the gas supplied to the analyzer are set to a predetermined flow rate, and the back pressure control device 13 for controlling the flow rate of the gas discharged from the analyzer is set in advance. The source exhaust flow control device 17 is set to a predetermined flow rate, and the makeup from the purified gas source 6 is controlled while controlling the internal pressure between the separation column 2 and the ion source 19 to be higher than the atmospheric pressure. Flow gas and carrier gas.
[0015]
In the analysis, first, a sample gas is supplied from the sample gas source 1. When the sample gas is introduced, the sample gas is introduced into one of the two measuring tubes 5, 5 connected to the eight-way gas switching cock 4, and a fixed amount of the sample gas is collected.
Thereafter, the sample gas is accompanied by the carrier gas via the 8-way gas switching cock 4 and introduced into the separation column 2 filled with the separating agent. In addition, as the separating agent, an arbitrary separating agent such as a molecular sieve type, a unibead type or the like can be used.
While passing through the separation column 2, the sample gas introduced into the separation column 2 is isolated for each of the main component gas and the trace impurities contained in the sample gas, and is connected to the outlet of the separation column 2. It flows out to the separated gas outflow path 10.
[0016]
A make-up gas path 9 is connected to the other end of the separation gas outflow path 10. The gas containing trace impurities is mixed with the make-up gas while the GC / APIMS connection path 11 and an ion branched at the end thereof. The gas is introduced into the ion source 19 through the source gas introduction path 15.
The makeup gas is not indispensable, but is used for stabilizing the ionization of the mass spectrometer 20 as described above, and a sufficient amount of gas to be detected by the mass spectrometer 20 is added. Things.
The flow rate of the makeup gas is determined by, for example, the characteristics of the mass spectrometer 20, the balance with the flow rate of the carrier gas, and the like.
Further, a branching portion of the GC / APIMS connection route 11 with the ion source gas introduction route 15 is connected to a discharge branching route 12 and a discharge route 14 following the branching route. By the action of the back pressure control device 13 provided therebetween, a predetermined flow rate of gas is discharged by branching from between the GC / APIMS connection path 11 and the ion source gas introduction path 15.
[0017]
Then, the sample ionized by the ion source unit 19 of the mass spectrometer 20 passes through a slit (not shown) provided in the ion source unit 19. Next, the ions generated by the ion source unit 19 are separated by mass (for each type) in the mass separation unit, and then introduced into the detection unit and detected.
The ion source section 19 is connected to an ion source exhaust gas exhaust path 18 from which excess gas is exhausted. The amount of the discharged gas is controlled by the ion source exhaust flow control device 17.
[0018]
By the way, in the present invention, it is presumed that the analysis accuracy is improved because the amount of water (water blank concentration) in the mass spectrometer 20 can be reduced. When a trace impurity is measured in the mass spectrometer 20 using an ion molecule reaction at atmospheric pressure in the presence of moisture, a trace impurity (e.g., hydrogen) having a smaller electron affinity than moisture or a trace impurity (e.g., carbon dioxide, etc.) having a higher ionization potential than moisture. ), The coexisting moisture has an adverse effect, resulting in poor accuracy and sensitivity in the analysis of these types of trace impurities.
On the other hand, it is normal that moisture is adsorbed to the separating agent in the GC separation column. This adsorbed water cannot be sufficiently reduced in a short time only by purging a commonly used carrier gas having a reduced water content, and the separating agent remains in trace amounts for a long time during the analysis. Continue to exhale and its concentration fluctuates.
In some cases, the water present in the mass spectrometer 20 may be at a level of several ppb to several tens ppb.
The influence of such adsorbed moisture is considered to be a specific problem caused by connecting the GC3 to the mass spectrometer 20 that ionizes at atmospheric pressure using an ion molecule reaction.
[0019]
Therefore, when the internal pressure in the range from the separation column 2 to the ion source unit 19 is increased, it becomes difficult for water to be desorbed from the separating agent in the separation column 2. As a result, it is possible to prevent the water in the separating agent of the separation column 2 from being introduced into the mass spectrometer 20 through the pipe connecting the separation column 2 and the ion source unit 19, and thereby, it is possible to prevent trace amounts of impurities. It is thought that the analysis accuracy and sensitivity of the sample are improved. Further, in the analysis method and the analysis device of the present invention, the repetition accuracy is improved. This is presumed to be because the moisture blank concentration is reduced, so that the variation in the analytical value due to the variation in the moisture blank concentration every measurement is reduced.
For example, in the apparatus shown in FIG. 1, when a pressure of 0.04 MPa is applied to the range from the separation column 2 to the ion source unit 19, the water concentration measured at the atmospheric pressure in the mass spectrometer 20 is several tens ppb or more. , To several ppb.
Note that, for example, even if only the pressure in the ion source unit 19 in the former stage of the mass spectrometer 20 is higher than the atmospheric pressure, the moisture blank concentration cannot be sufficiently reduced. It is important that the overall pressure be higher than atmospheric pressure.
[0020]
Furthermore, by performing such pressure control, the flow rate of the gas passing through the slit provided in the ion source unit 19 can be increased, and it is presumed that the sensitivity of the analysis is improved. In the experiment, when a pressure of 0.04 MPa was applied, the flow rate of the gas passing through the slit was increased 1.5 times that in the case of controlling at atmospheric pressure, the peak of trace impurities became large, and the analysis accuracy was improved. Has been confirmed to be.
[0021]
The analysis method and the analyzer are not limited to those shown in FIG. 1, but may be a combination of a GC and a mass spectrometer, and can control the pressure between the GC separation column and the ion source. It is not particularly limited as long as it is one.
Further, the analysis method and the analysis apparatus of the present invention are used, for example, for analyzing a high-purity bulk gas used in a gas phase process of a semiconductor device manufacturing process as described above, for leak inspection after piping construction, quality assurance of a purifier, and the like. Can be used.
The sample gas to be measured is not particularly limited, but includes a rare gas such as nitrogen or argon as a main component gas, and as a trace impurity, an impurity (e.g., hydrogen) having an electron affinity smaller than that of water or water. Particularly high effects can be obtained for a gas containing a trace impurity (such as carbon dioxide) having a higher ionization potential.
[0022]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
The relationship between the pressure and the accuracy of the analysis was examined using an analyzer similar to that shown in FIG. The measurement target was hydrogen (trace impurities) in nitrogen gas (main component).
The measurement conditions were as follows.
[0023]
Carrier gas, makeup gas: helium,
Separation column: a stainless steel column (2 mmφ × 2 m) packed with molecular sieves 13XS (product name, manufactured by GL Sciences),
Sample gas sampling volume: 3 ml,
Pressure of purified gas source: 0.2 MPa,
Carrier gas flow rate: 56 ml / min,
Makeup gas flow rate: 500 ml / min.
[0024]
By controlling the back pressure control device 13 and the ion source exhaust flow control device 17, the water blank concentration detected when the pressure between the separation column 2 and the ion source section 19 is set to a pressure higher than the atmospheric pressure is increased. It was compared with the moisture blank concentration detected under atmospheric pressure conditions.
The results are shown in Table 1.
The pressure between the separation column 2 and the ion source 19 is represented by the pressure of the ion source 19 as a representative. As described above, the pressure of the outlet side of the separation column 2, the separation gas outflow path 10, the GC / APIMS connection path 11, and the ion source gas introduction path 15 is almost the same as the pressure in the ion source section 19 due to the configuration of the apparatus. It is. Normally, the pressure on the inlet side of the separation column 2 is slightly higher than the pressure in the ion source 19.
[0025]
[Table 1]

[0026]
From the results shown in Table 1, it was found that when the pressure was higher than the atmospheric pressure, the moisture blank concentration was significantly reduced.
[0027]
Next, Table 2 shows the repetition accuracy when the nitrogen gas containing 7.2 ppb hydrogen impurity was analyzed 10 times repeatedly. It was confirmed that the coefficient of variation was small and the repetition accuracy was good. Since the repetition accuracy was good in this way, it was inferred that the influence of the moisture blank was reduced.
[0028]
[Table 2]

[0029]
FIG. 2 is a graph showing the peak intensity of hydrogen when the pressure in the ion source 19 from the separation column 2 was changed. Within the measurement pressure range, it was confirmed that as the pressure was applied, the peak intensity was improved and the sensitivity was improved.
FIG. 3 shows chromatographs when the pressure in the ion source unit 19 is 0 and when the pressure is 0.06 MPaG. By setting the pressure higher than the atmospheric pressure, the peak intensity was increased, the lower detection limit was increased several times, and the sensitivity was greatly increased as compared with the case of the atmospheric pressure.
[0030]
From the results of the above experiments, it is found that the simple method of setting the pressure of the ion source unit 19 from the separation column 2 higher than the atmospheric pressure can significantly improve the detection sensitivity of trace impurities and greatly improve the analysis accuracy. It could be confirmed.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a method and an apparatus for analyzing trace impurities in a gas, which enable highly accurate analysis.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an example of an analyzer using the analysis method of the present invention.
FIG. 2 is a graph showing the peak intensity of hydrogen when the pressure in the ion source unit 19 is changed in the example.
FIG. 3 is a diagram showing a chromatograph obtained in an example.
[Explanation of symbols]
1 sample gas source,
2 separation column,
3 Gas chromatograph (GC)
4 8-way gas switching cock 5 Metering pipe 6 Purification gas source 6a Purification gas flow path 7 Flow control device 7a Carrier gas flow path 8 Flow control device 9 Makeup gas path 10 Separation gas outflow path 11 GC / APIMS connection path 12 Discharge branch flow Path 13 back pressure control device (back pressure regulator)
14 discharge path 15 ion source gas introduction path 17 ion source exhaust flow control device 18 ion source exhaust gas discharge path

Claims (7)

A method for analyzing trace impurities in a gas using a mass spectrometer that separates trace impurities in a sample gas with a separation column of a gas chromatograph, ionizes the trace impurities in an ion source unit, and performs mass separation. A method for analyzing trace impurities in a gas, characterized in that the analysis is performed while maintaining the pressure of the ion source higher than the atmospheric pressure. In the analysis method according to claim 1, by adjusting the amount of gas supplied to the mass spectrometer and the amount of gas discharged from the mass spectrometer, the pressure of the ion source unit from the separation column, A method for analyzing trace impurities in a gas, wherein the analysis is performed while maintaining the pressure higher than the atmospheric pressure. 3. The analysis method according to claim 2, wherein the amount of gas discharged from a discharge path provided on a downstream side of the ion source unit, an outlet of the separation column, and an inlet of the ion source unit are provided. 4. An analysis method comprising adjusting both the amount of gas discharged from a discharged discharge path. Supply to the mass spectrometer based on a back pressure of at least one of a discharge path provided between an outlet of the separation column and an inlet of the ion source section or a discharge path provided at a downstream side of the ion source section. 4. The analysis method according to claim 3, wherein the amount of gas to be discharged and the amount of gas discharged from the mass spectrometer are adjusted. In a gas chromatograph, a trace impurity in a sample gas separated by a separation column of the gas chromatograph is ionized in an ion source part, and in a device for analyzing a trace impurity in a gas using a mass spectrometer for mass separation,
An apparatus for analyzing trace impurities in a gas, comprising: control means for controlling the pressure of the ion source from the separation column to a pressure higher than the atmospheric pressure. 6. The apparatus according to claim 5, wherein the control means comprises a flow control means for adjusting an amount of gas supplied to the mass spectrometer, and a flow control means for adjusting an amount of gas discharged from the mass spectrometer. The analyzer according to claim 1. Flow control means for controlling the amount of gas discharged from the mass spectrometer,
Back pressure control means provided between at least one of a discharge path provided between an outlet of the separation column and an inlet of the ion source unit or a downstream side of the ion source unit,
Flow rate control means for controlling the amount of gas discharged from a discharge path provided on the subsequent stage of the ion source section,
7. The apparatus according to claim 6, further comprising: a flow control unit configured to control an amount of gas discharged from a discharge path provided between an outlet of the separation column and an inlet of the ion source unit. Analysis equipment.

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