JP6843395B2 - Three-component simultaneous analyzer and three-component simultaneous analysis method - Google Patents

Description

The present invention relates to a three-component simultaneous analyzer and a three-component simultaneous analysis method.

Methane gas, carbon dioxide, and nitrous oxide contained in atmospheric gas are greenhouse gases that contribute significantly to global warming, and their generation and extinction mechanisms are greatly affected by fluctuations in the redox state of soil. It is important as a gas component. Here, the concentration of the methane gas in the atmosphere is 1.744 ppm, which is much lower than that of carbon dioxide (about 390 ppm). However, the greenhouse effect (Global Warming Potential (GWP)) of methane gas is 25 times higher than that of the same amount of carbon dioxide. The concentration of nitrous oxide in the atmosphere is 319 ppb, which is about 1/1000 times that of carbon dioxide. However, the GWP value of nitrous oxide is also the same as that of methane gas. It shows a higher value than carbon dioxide. Specifically, the GWP value of nitrous oxide is 298 times that of carbon dioxide. Regarding the above-mentioned methane gas, carbon dioxide and nitrous oxide having such greenhouse effect characteristics, reduction targets are set by the Kyoto Protocol, and it is necessary to measure the concentration with high accuracy in order to estimate the amount generated. There is.

The three components contained in the above-mentioned atmospheric gas have different chemical properties. Therefore, when a gas chromatograph is used to measure the gas concentration in the atmosphere, since the carrier gas used is different, it is usual to prepare three gas chromatographs and adopt a method of detecting them individually. there were.

In particular, various studies have been conducted on a method for detecting nitrous oxide having an atmospheric concentration on the order of ppb. For example, as a method for detecting nitrous oxide, a method using an electron capture detector, which is a selective detector utilizing electron capture ability, and a carrier gas obtained by adding 5% of methane gas to argon gas has been proposed so far. (Non-Patent Documents 1 and 2). However, since the concentration of nitrous oxide in atmospheric gas is extremely low as described above, it is necessary to take various measures for removing impurities and reducing noise.

Nobuyoshi Aroma, "Isotope Handbook", p. 606, Maruzen, 1984 Yoshida et al., "Study on Analysis Method of Ultratrace Elements in Gas (2)", High Pressure Gas, Vol. 29, No. 2 (1992) Sudo, S. et al., 1997. Precise measurement of atmospheric concentration of CH3Br by GC / ECD. Chemistry Letters, Vol.26 No.3 239-240

However, conventional methods for detecting methane gas, carbon dioxide and nitrous oxide contained in atmospheric gas require labor and time to obtain measurement results. Therefore, in recent years, there has been a demand for the realization of a device capable of detecting the above three components contained in atmospheric gas with high accuracy by a labor-saving method.

Based on the above, the present invention simultaneously analyzes the three components of methane gas, carbon dioxide and nitrous oxide contained in the atmospheric gas at a high S / N ratio even when the sample concentration is on the ppb order. It provides a three-component simultaneous analyzer capable of detection and a three-component simultaneous analysis method.

The present inventor has diligently studied the design guideline in order to realize a device capable of detecting the above three components contained in atmospheric gas with high accuracy. As a result, the present inventor made a configuration in which a capillary column or a stainless steel column was used in combination with the packed column, because the molecular weights were almost the same, it was difficult to completely separate carbon dioxide and carbon dioxide by gas chromatography. We have found that it is effective as a design guideline for increasing the detection sensitivity and S / N ratio of nitrous oxide, and have reached the present invention.

According to the present invention, it is a three-component simultaneous analyzer for detecting three components composed of methane gas, carbon dioxide and nitrous oxide contained in the atmospheric gas which is an analysis sample.
The three-component simultaneous analyzer
The first gas flow path and
A second gas flow path and a third gas flow path located downstream of the first gas flow path,
Between the first gas flow path and the second gas flow path, and between the first gas flow path and the third gas flow path, the first gas flow path and the first gas flow path. It has a first state in which the two gas flow paths communicate with each other, and a switching valve for switching between the first gas flow path and the second state in which the third gas flow path communicates with each other.
The first gas flow path is
The carrier gas introduction part that introduces the carrier gas and
The sample introduction unit into which the analysis sample is introduced and the sample introduction unit
A first gas phase containing the methane gas and the carbon dioxide are located on the downstream side of the carrier gas introduction section and the sample introduction section and cause a flow delay depending on the type of the component contained in the analysis sample. A first column arranged to obtain a second gas phase containing carbon and the nitrous oxide.
Have,
The second gas flow path is
A hydrogen flame ionization detector for detecting the methane gas contained in the first gas phase is provided at the downstream end.
The third gas flow path is
A second column consisting of packed columns and
A third gas phase containing carbon dioxide and the nitrous oxide are located downstream of the second column and cause a flow delay depending on the type of the component contained in the second gas phase. A third column consisting of a capillary column or a stainless steel column arranged to obtain a fourth gas phase containing nitrous oxide, and
A thermal conductivity type detector for detecting the carbon dioxide contained in the third gas phase on the downstream side of the third column.
An electron capture detector for detecting the nitrous oxide contained in the fourth gas phase, which is located downstream of the thermal conductivity detector.
A three-component simultaneous analyzer having the above is provided.

Further, according to the present invention, it is a three-component simultaneous analysis method for detecting three components consisting of methane gas, carbon dioxide and nitrous oxide contained in the atmospheric gas which is an analysis sample.
The carrier gas introduction process that introduces the carrier gas into the gas flow path and
A sample introduction step of introducing the analysis sample into the gas flow path filled with the carrier gas, and
A first gas separation step of obtaining a first gas phase containing methane gas and a second gas phase containing carbon dioxide and nitrous oxide from the components contained in the analysis sample.
A second gas separation step of obtaining a third gas phase containing carbon dioxide and a fourth gas phase containing nitrous oxide from the components contained in the second gas phase.
Have,
The first gas separation step is
A step of passing the analysis sample through a first column for causing a flow delay depending on the type of the component, and
In the subsequent step of the step of passing the gas through the first column, the methane gas introduction step of introducing the first gas phase into a gas flow path having a hydrogen flame ionization detector and the second gas phase are heated. The process of introducing into a gas flow path having a conductivity type detector and an electron capture type detector,
In the subsequent step of the methane gas introduction step, the step of detecting the methane gas contained in the first gas phase by the hydrogen flame ionization detector is included.
The second gas separation step is
A step of passing the second gas phase through a second column composed of a packed column, and
A step of passing the second gas phase through a third column composed of a capillary column or a stainless steel column for causing a flow delay depending on the type of the component.
In the subsequent step of the step of passing the gas through the third column, the thermal conductivity type detector detects carbon dioxide contained in the third gas phase, and the electron capture type detector detects the carbon dioxide contained in the third gas phase. A step of detecting nitrous oxide contained therein and a method for simultaneous analysis of three components including the same are provided.

According to the present invention, three components composed of methane gas, carbon dioxide and dinitrogen monoxide contained in atmospheric gas are simultaneously detected at a high S / N ratio even when the sample concentration is on the order of ppb in one analysis. It is possible to provide a three-component simultaneous analyzer and a three-component simultaneous analysis method.

The above-mentioned objectives and other objectives, features and advantages will be further clarified by the preferred embodiments described below and the accompanying drawings below.

It is a system diagram which shows the structure of the three-component simultaneous analyzer which concerns on this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by the same reference numerals, and description thereof will be omitted as appropriate.

<Simultaneous three-component analyzer>
FIG. 1 is a schematic view showing the configuration of a three-component simultaneous analyzer according to the present embodiment.
First, the three-component simultaneous analyzer according to the present embodiment (hereinafter, also referred to as the present analyzer) detects three components composed of methane gas, carbon dioxide, and dinitrogen monoxide contained in the atmospheric gas as an analysis sample. It is a device for. Then, as shown in FIG. 1, the analyzer includes a first gas flow path A, a second gas flow path B located downstream of the first gas flow path A, and a third gas flow path. A first gas flow path between the path C, the first gas flow path A and the second gas flow path B, and between the first gas flow path A and the third gas flow path C. A switching valve 400 for switching between a first state in which A and the second gas flow path B communicate with each other and a second state in which the first gas flow path A and the third gas flow path C communicate with each other. have. Hereinafter, each configuration related to this analyzer will be described.

First, the first gas flow path A is more than a carrier gas introduction unit 10 for introducing a carrier gas, a sample introduction unit 30 (injection port) for introducing an analysis sample, a carrier gas introduction unit 10 and a sample introduction unit 30. On the downstream side, a flow delay is caused depending on the type of the component contained in the analysis sample to obtain a first gas phase containing methane gas and a second gas phase containing carbon dioxide and dinitrogen monoxide. It has a first column 60, which is arranged for the purpose.

In this analyzer, the carrier gas introduction unit 10 described above preferably includes the carrier gas purification device 20. By doing so, it is possible to improve the purity of the carrier gas introduced into the present analyzer. Then, when the above-mentioned three components are detected using the carrier gas whose purity has been increased by the carrier gas purifying device 20, the S / N ratio and detection of the analysis result are affected by the impurities contained in the carrier gas. It is possible to prevent the sensitivity from being lowered. Specifically, by using a carrier gas such as nitrogen gas or helium gas whose purity has been increased by the carrier gas purification device 20, the detection peak of impurities contained in the carrier gas is the detection of the above three components to be analyzed. It is possible to prevent inconveniences such as overlapping with the peak and the above-mentioned impurities accumulated in the gas separation column (first to third columns, etc.) described later increasing the detector noise and shortening the column life. be able to.

The carrier gas purification device 20 described above is used to increase the purity of the carrier gas introduced into the analyzer, but from the viewpoint of dramatically improving the purity of the carrier gas, it is provided with a multi-stage carrier gas purification mechanism. It is preferable to have. Further, as a specific example of the carrier gas purification mechanism provided in the carrier gas purification device 20, a gas purification filter such as a charcoal filter, a moisture chart wrap, an oil mist trap, a hydrocarbon removal pipe filled with activated carbon, and a molecular sieve are filled. Examples thereof include a moisture absorbent tube, a trace oxygen / water removal tube filled with a resin (for example, manufactured by SUPELCO, OMI-4, etc.).

The sample introduction unit 30 described above in this analyzer is provided with a septum (packing) in order to prevent inconveniences such as leakage of the analysis sample to the outside of the apparatus and mixing of outside air. Such a septum has a sealing property that can maintain the carrier gas pressure in the sample introduction unit 30 and can prevent the analysis sample from leaking to the outside of the apparatus even if the analysis is performed a plurality of times. It is not limited as long as it meets the conditions such as what it is doing. However, it is preferable to replace the septum with a new one with a maximum of 100 sample introductions as a guide, in order to prevent the above-mentioned inconvenience from occurring due to deterioration due to the multiple sample introductions.

Further, the sample introduction unit 30 in this analyzer may have an automatic gas injection device (autosampler) from the viewpoint of reducing the labor and time required to acquire the measurement result.

A flow delay is caused on the downstream side of the carrier gas introduction section 10 and the sample introduction section 30 in the first gas flow path A in the present analyzer according to the type of the component contained in the analysis sample, and methane gas is introduced. There is a first gas phase containing and a first column 60 arranged to obtain a second gas phase containing carbon dioxide and dinitrogen monoxide. As described above, the first column 60 causes a flow delay depending on the type of the component contained in the analysis sample. Therefore, when the analysis sample is passed through the first column 60. , The retention time of the components contained in the analysis sample will be different.

Here, the column filler contained in the first column 60 is preferably a styrene polymer fine powder or an effective activated carbon fine powder. Of these, effective activated carbon fine powder is preferable from the viewpoint of causing a clear difference in retention time between methane gas contained in the analysis sample and carbon dioxide and nitrous oxide. Here, specific examples of the effective activated carbon fine powder include zeolite powder containing a molecular sieve and activated carbon. When such effective activated carbon fine powder is used as a column filler, Unibeds C (manufactured by GL Science Co., Ltd.), activated carbon (SHINCARBON ST: Shinwa Kako), Molecular Sieve5A (manufactured by GL Science Co., Ltd.) and Molecular Sieve13X (manufactured by GL Science Co., Ltd.) A commercially available filler such as (manufactured by) may be used. Next, specific examples of the styrene polymer fine powder include commercially available porous polymer-based fillers such as Waters' Porapak Q, Porapak N, Porasil D and Porapak QS. Above all, a filler called Unibeds C (manufactured by GL Science Co., Ltd.) is preferable because it can cause a slight difference in the retention time between carbon dioxide and nitrous oxide.

Further, in the first column 60 of the present analyzer, methane gas having a molar mass of about 16 g / mol and carbon dioxide and dinitrogen monoxide having a molar mass of about 44 g / mol are in different gas phases. Since the configuration is arranged from the viewpoint of separating so as to be included, the packed column is used from the viewpoint of excellent separation of hydrocarbons and a large amount of samples that can be processed, rather than the theoretical number of stages per unit length of the column. It is preferable to have.

The column temperature of the first column 60 is, for example, preferably 70 ° C. or higher and 170 ° C. or lower, and more preferably 80 ° C. or higher and 150 ° C. or lower. By doing so, it is possible to make a clear difference in the retention time between the first gas phase containing methane gas and the second gas phase containing carbon dioxide and nitrous oxide.

In addition to the first column 60, the first gas flow path A in this analyzer is filled with styrene polymer fine powder from the viewpoint of suppressing column bleeding when the column is heated under high temperature conditions. It is preferable to further include a column encapsulated as an agent. Examples of such styrene polymer fine powders include commercially available porous polymer-based fillers such as Waters' Porapak Q, Porapak N, Porapak D and Porapak QS.

Further, the first gas flow path A is on the downstream side of the sample introduction section 30 in the first gas flow path A, and on the upstream side of the first column 60, the analysis result S / From the viewpoint of improving the N ratio, it is preferable to further include, for example, a water removal trap and an oxygen removal trap in order to remove water, oxygen and the like contained in the analysis sample.

Next, the second gas flow path B has a hydrogen flame ionization detector 100 (hereinafter, also referred to as FID 100) for detecting the methane gas contained in the first gas phase described above at the downstream end. ing. The FID 100 generally refers to a detector that measures the concentration of total hydrocarbons by measuring the ionic current generated when the gas to be measured is burned in a hydrogen flame. Therefore, the detector FID100 is suitable for detecting hydrocarbons such as methane gas. For the detection of methane gas using FID100, for example, a carrier gas is flowed at a flow rate of 20 mL / min or more and 40 mL / min or less, the temperature of FID100 is set to 200 ° C. or more and 300 ° C. or less, and 1 mL of an analytical sample is introduced. When introduced from the part 30, it can be detected with a holding time of about 2 minutes.

On the upstream side of the second gas flow path B from the FID 100, a column containing styrene polymer fine powder as a filler is further included from the viewpoint of suppressing the occurrence of column bleeding when the column is heated under high temperature conditions. Is preferable. Examples of such styrene polymer fine powders include commercially available porous polymer-based fillers such as Waters' Porapak Q, Porapak N, Porasil D and Porapak QS.

Next, the third gas flow path C is located on the downstream side of the second column 70 made of a packed column and the second column 70, and is a type of component contained in the second gas phase. A third column 80 consisting of a capillary column or a stainless steel column arranged to obtain a third gas phase containing carbon dioxide and a fourth gas phase containing dinitrogen monoxide, which causes a flow delay accordingly. From the thermal conductivity type detector 200 for detecting carbon dioxide contained in the third gas phase, which is on the downstream side of the third column 80, and the thermal conductivity type detector 200. Also on the downstream side, it has an electron trap type detector 300 for detecting dinitrogen monoxide contained in the fourth gas phase.

The second column 70 in the third gas flow path C is arranged to adjust the balance between the outlet pressure of the second gas flow path B described above and the outlet pressure of the third gas flow path C. ing. As described above, by having the second column 70 in this analyzer, the influence of the valve shock generated when the flow path state is switched by using the switching valve 400 on the baseline and the detected peak shape is reduced. can do. Specifically, it is possible to suppress the occurrence of inconveniences such as baseline fluctuation and detection peak shape fluctuation due to the valve shock. In order to accurately detect trace components such as nitrous oxide contained in the analytical sample introduced into this analyzer, it is particularly important to reduce the inconvenience caused by the valve shock described above as much as possible. The outlet pressure of the second gas flow path B refers to the gas pressure on the upstream side of the hydrogen flame ionization detector 100 in the second gas flow path B, and is the third gas flow path. The outlet pressure of C refers to the outlet pressure of the third column 80 in the third gas flow path C.

Here, in this analyzer, when the outlet pressure of the second gas flow path B is R2 and the outlet pressure of the third gas flow path C is R3, the second column 70 causes R2 /. The value of R3 is preferably 1 or more and 40 or less, and more preferably 2 or more and 30 or less. By doing so, the two components of carbon dioxide and nitrous oxide can be detected at a high S / N ratio. The outlet pressure of the gas flow path is generally proportional to the diameter of the column.

The column filler contained in the second column 70 is preferably a styrene polymer fine powder or an effective activated carbon fine powder. Of these, effective activated carbon fine powder is preferable from the viewpoint of causing a clear difference in retention time between methane gas contained in the analysis sample and carbon dioxide and nitrous oxide. Here, specific examples of the effective activated carbon fine powder include zeolite powder containing a molecular sieve and activated carbon. When such effective activated carbon fine powder is used as a column filler, commercially available fillers such as Unibeds C (manufactured by GL Science), activated carbon, Molecular Sieve 5A (manufactured by GL Science) and Molecular Sieve 13X (manufactured by GL Science) are used. May be used. Next, specific examples of the styrene polymer fine powder include commercially available porous polymer-based fillers such as Waters' Porapak Q, Porapak N, Porasil D and Porapak QS. In particular, a filler called Unibeds C (manufactured by GL Science Co., Ltd.) is preferable because it can cause a slight difference in the retention time between carbon dioxide and nitrous oxide.

The column temperature of the second column 70 is, for example, preferably 70 ° C. or higher and 110 ° C. or lower, more preferably 75 ° C. or higher and 100 ° C. or lower, and even more preferably 80 ° C. or higher and 90 ° C. or lower.

Next, as described above, the third column 80 in the third gas flow path C is a capillary column or a stainless steel column located downstream of the second column 70, and is carbon dioxide and nitrous oxide. In order to cause a flow delay depending on the type of the component contained in the second gas phase including and to obtain a third gas phase containing carbon dioxide and a fourth gas phase containing nitrous oxide. It is arranged in. In general, a capillary column or a stainless steel column has a smaller column inner diameter and a higher number of theoretical plates than a packed column. Therefore, according to the third column 80, it is possible to reduce the flow rate of the gas that has passed through the second column 70. That is, according to the third column 80, the outlet pressure of the third column 80 can be controlled to be smaller than the outlet pressure of the second column 70. As a result, in this analyzer, since the molecular weights are almost the same, there is a clear difference in the retention times of carbon dioxide and nitrous oxide, which were difficult to completely separate in the conventional analyzer. It becomes possible to make it. In other words, since the analyzer employs the configuration having the third column 80, it is possible to detect each of carbon dioxide and nitrous oxide with high accuracy.

Here, the column inner diameters of the second column 70 and the third column 80 are such that the second column 70 is 1 mm or more and 5 mm or less, and the third column 80 is 0.1 mm or more and 1 mm or less. It is more preferable that the second column 70 is 2 mm or more and 4.5 mm or less, and the third column 80 is 0.2 mm or more and 0.8 mm or less. By doing so, both carbon dioxide and nitrous oxide components contained in the analytical sample introduced into the present analyzer can be detected with high S / N ratios, respectively.

The outlet flow rate of the third column 80 (outlet flow rate in the third gas flow path C) in this analyzer is accurate even if the amount of dinitrogen monoxide, which is extremely low in the atmospheric gas, is on the order of ppb. From the viewpoint of good detection, when an analytical sample of 500 μL or more is introduced from the sample introduction unit 30, it is preferable that the outlet flow rate is 3 mL / min or more and 25 mL / min or less, preferably 3 mL / min or more. It is more preferable that the concentration is 20 mL / min or less.

Examples of the column packing material to be included in the third column 80 include methylpolysiloxane and the like. As the third column 80, a commercially available capillary column such as HP-1 (manufactured by Agilent Technologies) or DB-1 (manufactured by Agilent Technologies), or a Polymer Q (made by Agilent Technologies) having a size of about 80 to 100 mesh is used. A stainless steel column of about 2 to 5 m containing a porous polymer-based filler such as (manufactured by GL Science), Porapak N (manufactured by GL Science) and Porasil D (manufactured by GL Science) can be used. Above all, it is preferable to use PoraBOND Q from the viewpoint of improving the separation efficiency of carbon dioxide and nitrous oxide.

The column temperature of the third column 80 is, for example, preferably 70 ° C. or higher and 170 ° C. or lower, and more preferably 80 ° C. or higher and 160 ° C. or lower. By doing so, it becomes possible to detect each of carbon dioxide and nitrous oxide with a high S / N ratio.

The third gas flow path C is a thermal conductivity type detector 200 (hereinafter, also referred to as TCD200) for detecting carbon dioxide contained in the above-mentioned third gas phase on the downstream side of the third column 80. .)have. The TCD200 generally refers to a detector that measures the concentration of the component to be measured by measuring the difference in thermal conductivity between the component to be measured and the carrier gas. Therefore, the detector called TCD200 is suitable for detecting components other than the components contained in the carrier gas. The carbon dioxide using TCD200 is detected, for example, when the carrier gas is flowed at a flow rate of 35 mL / min or more and 45 mL / min or less, the holding time is about 4 to 5 minutes from the start of the outflow of the carrier gas. Can be done.

The third gas flow path C has an electron capture detector 300 (hereinafter, also referred to as ECD300) for detecting nitrous oxide contained in the above-mentioned fourth gas phase on the downstream side of the TCD200. Have. In such an ECD300, in general, the ion current flowing between the electrodes in the ECD300 is reduced by combining the emitted electrons with the ionized carrier gas using β rays of ^{63 Ni and the parent electron substance.} It refers to a detector that measures the amount and measures the concentration of the parent electron substance. Therefore, a detector called ECD300 is suitable for detecting components such as nitro compounds. The detection of nitrous oxide using ECD300 is performed, for example, when the carrier gas is flowed at a flow rate of 35 mL / min or more and 45 mL / min or less, the detection time is about 4 to 5 minutes from the start of the outflow of the carrier gas. can do.

Further, it is preferable that the third gas flow path C further has an additive gas introduction unit 50 for introducing the additive gas on the downstream side of the TCD 200 and on the upstream side of the ECD 300. As described above, the detector called ECD300 utilizes the ion current (more specifically, the negative ion current) that flows between the electrodes by ionizing the carrier gas. Therefore, the carrier gas needs to contain a sufficient amount of components that are easily ionized. Therefore, by supplying gas components such as nitrogen gas and methane gas that are easily ionized from the added gas introduction unit 50 into the third gas flow path C, nitrous oxide having an extremely low content in the atmospheric gas is supplied. It is possible to accurately detect the amount of gas in the order of ppb.

Next, a three-component simultaneous analysis method (hereinafter, also referred to as this analysis method) for detecting three components consisting of methane gas, carbon dioxide and nitrous oxide contained in the atmospheric gas as an analysis sample using the above-mentioned analyzer. .) Will be described.

This analysis method includes a carrier gas introduction step of introducing a carrier gas into a gas flow path, a sample introduction step of introducing an analysis sample into a gas flow path filled with the carrier gas, and components contained in the analysis sample. From the first gas separation step of obtaining a first gas phase containing methane gas and a second gas phase containing carbon dioxide and dinitrogen monoxide, and from the components contained in the second gas phase, carbon dioxide It is a method having a second gas separation step of obtaining a third gas phase containing carbon and a fourth gas phase containing dinitrogen monoxide.

(Carrier gas introduction process)
In the present analysis method, first, the carrier gas is introduced into the first gas flow path A from the carrier gas introduction unit 10 in the present analyzer shown in FIG. By doing so, all the gas components existing in the gas flow path in this analyzer can be replaced with the carrier gas. The flow rate of the carrier gas should be appropriately set by the flow rate regulator mounted on this analyzer in consideration of the relationship between the specifications of the column to be used and the retention time (retention time) of the component to be analyzed. However, it is preferably 20 mL / min or more and 40 mL / min or less from the viewpoint of causing a difference in the retention time of the three components composed of methane gas, carbon dioxide and nitrous oxide.

In this analysis method, it is preferable to increase the purity of the carrier gas by using the carrier gas purifying device 20 before introducing the carrier gas into the first gas flow path A. That is, it is preferable that the carrier gas introduction step further includes a step of improving the purity of the carrier gas. By doing so, it is possible to prevent the S / N ratio and the detection sensitivity of the analysis result from being lowered due to the influence of impurities contained in the carrier gas. Specifically, by increasing the purity of the carrier gas in advance by the carrier gas purifying device 20, the detection peaks of impurities contained in the carrier gas overlap with the detection peaks of the above three components to be analyzed. It is possible to prevent the above-mentioned impurities accumulated in the gas separation columns (first to third columns, etc.) described later from causing inconveniences such as increasing detector noise and shortening the column life. In particular, the purity of the carrier gas is preferably 99.999% or more, preferably 99.9999%, from the viewpoint of accurately detecting the amount of nitrous oxide having an extremely small content in the atmospheric gas on the order of ppb. It is more preferably 99.999999% or more, further preferably 99.999999% or more, and most preferably 99.999999% or more. If the upper limit of the purity of the carrier gas is about 99.999999%, it is possible to prevent the inconvenience caused by the above-mentioned impurities. The carrier gas is preferably helium gas or nitrogen gas having a purity of 99.999% or more. The carrier gas purification device 20 described above preferably includes a multi-stage carrier gas purification mechanism from the viewpoint of improving the purity of the carrier gas as much as possible.

(Sample introduction process)
Next, in this analysis method, the analysis sample is introduced from the sample introduction unit 30 into the gas flow path filled with the carrier gas. Specifically, 1 to 2 mL of atmospheric gas collected in a container such as a vial is introduced into the sample introduction unit 30 using a gas tight syringe.

In this analysis method, from the viewpoint of reducing the labor and time required to acquire the measurement result, for example, an automatic gas injection device (autosampler) is used to inject atmospheric gas from the sample introduction unit 30 to the gas flow path. It may be introduced.

(First gas separation step)
Then, in this analysis method, the analysis sample is passed through a first column 60 for causing a flow delay depending on the type of the component. By doing so, each component contained in the analysis sample can be separated into a first gas phase containing methane gas and a second gas phase containing carbon dioxide and nitrous oxide. From the viewpoint of suppressing the occurrence of column bleeding when the column is heated under high temperature conditions before and / or after passing through the first column 60, the analysis sample is made of Waters' Polymer Q and Polymer. Commercially available porous polymer-based fillers such as N, Porasil D and Porapak QS may be passed through an encapsulated column. In this analysis method, each component contained in the first gas phase is held in the first column 60 for a shorter time than each component contained in the second gas phase.

Next, the first gas phase containing methane gas is introduced into the second gas flow path B having the hydrogen flame ionization detector 100, and after the methane gas introduction step, the flow path state is switched by the switching valve 400. The second gas phase containing carbon dioxide and dinitrogen monoxide is introduced into a third gas flow path C having a thermal conductivity detector 200 and an electron capture detector 300. The flow path state is switched by the switching valve 400 at an appropriate timing in consideration of the flow rate of the carrier gas, the holding time of each component by the first column 60, and the like.

Next, the methane gas contained in the first gas phase introduced into the second gas flow path B is detected by the FID 100. Regarding the first gas phase introduced into the second gas flow path B, from the viewpoint of suppressing the occurrence of column bleeding when the column is heated under high temperature conditions, Waters before introducing into the FID 100 It is preferable to pass a column containing a commercially available porous polymer-based filler such as Porapak Q, Porapak N, Porasil D and Porapak QS manufactured by the same company.

(Second gas separation step)
Next, the second gas phase containing carbon dioxide and nitrous oxide introduced into the third gas flow path C is passed through the second column 70 made of a packed column. Then, the second gas phase is passed through a third column 80 made of a capillary column or a stainless steel column for causing a flow delay depending on the type of the component. By doing so, each component contained in the second gas phase can be separated into a third gas phase containing carbon dioxide and a fourth gas phase containing nitrous oxide. In this analysis method, each component contained in the third gas phase is held in the third column 80 for a shorter time than each component contained in the fourth gas phase.

Then, carbon dioxide contained in the third gas phase obtained by passing through the third gas phase is detected by TCD200, and then nitrous oxide contained in the fourth gas phase passing through TCD200 is detected. Detected by ECD300. Here, in this analysis method, from the detection of carbon dioxide by TCD200 to the introduction of the fourth gas phase into the ECD300, that is, from the detection of carbon dioxide to the detection of nitrous oxide. From the viewpoint of accurately detecting the amount of nitrous oxide having an extremely small content in the atmospheric gas on the order of ppb, it is preferable to introduce methane gas or nitrogen gas into the gas flow path as an additive gas. Further, according to the findings obtained by the present inventor so far, even when nitrogen gas is used as a carrier gas, the detection sensitivity (and S / N) of nitrous oxide by ECD300 is obtained by adding methane gas. The ratio) can be improved up to 10 times (Non-Patent Document 3).

In the present embodiment, in one analysis, three components composed of methane gas, carbon dioxide and nitrous oxide contained in the atmospheric gas are simultaneously detected at a high S / N ratio even when the sample concentration is on the order of ppb. be able to. Further, according to the present embodiment, for example, it is possible to quantify three components composed of methane gas, carbon dioxide and nitrous oxide contained in atmospheric gas by one analysis.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above can be adopted.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

<Example 1>
FIG. 1 is a system diagram showing a configuration of a three-component simultaneous analyzer according to this embodiment. In assembling such a device, a total of two commercially available gas chromatographs (GC-14B type gas chromatograph (manufactured by Shimadzu Corporation) and GC-17A type gas chromatograph (with ECD)) are used in order to utilize the functions of the column constant temperature bath and the like. Shimadzu Corporation)) was prepared. Then, as shown in FIG. 1, the gas supply system, switching valve (A) 400 (manufactured by Shimadzu Corporation, pneumatically driven 10-way switching valve), switching valve (B) 500 (manufactured by Shimadzu Corporation, pneumatically driven type). 10-way switching valve), various separation columns, FID100 (Shimadzu, GC-14B FID), TCD200 (Shimadzu, GC-14B TCD) and ECD300 (Shimadzu, GC-17A ECD) ) Are placed respectively. For the gas pipes for connecting each device, SUS316 tubes having an outer diameter of 2 mm were used.

Here, as the carrier gas supply system, a clean filter (Agilent gas cleaning unit: molecular sieve and Agilent gas cleaning unit: oxygen trap are used together) and a gas flow rate regulator (Shimadzu) are used as the carrier gas purification device 20. A carrier gas introduction unit 10 having a CFC-114PM type manufactured by Mfg. Co., Ltd. was adopted. Nitrogen (industrial grade) introduced from the carrier gas introduction unit 10 is increased in purity to 99.999% or more by passing through a clean filter, and then a three-component simultaneous analyzer with a gas flow rate of 30 mL / min. Carrier gas was introduced inside.

As the additive gas supply system, an additive gas introduction unit 50 having a gas flow rate regulator (manufactured by Shimadzu Corporation, CFC-114PM type) and a clean filter (manufactured by Superco, OMI-2 type) was adopted. High-purity methane (manufactured by JFP, G1 (purity 99.999% or more)) was introduced from the added gas introduction unit 50 at a gas flow rate of 1 to 5 mL / min.

The following separation columns were used in this analyzer.
Column Co1: Unibeds C 80/100 mesh (manufactured by GL Science, inner diameter 2 mm, length 0.5 m)
Column Co2: Porapak QS 80/100 mesh (manufactured by Waters, inner diameter 3 mm, length 1.5 m)
Column Co3: Porapak QS 80/100 mesh (manufactured by Waters, inner diameter 3 mm, length 1 m)
Column Co4: Porapak QS 80/100 mesh (manufactured by Waters, inner diameter 3 mm, length 2 m)
Column Co5: Porapak N 80/100 mesh (manufactured by Waters, inner diameter 3 mm, length 1 m)
Column Co6: CP PoraBOND Q 80/100 mesh (manufactured by Agilent Technologies, inner diameter 0.53 mm, length 1 m)
Column Co7: Porapak N 80/100 mesh (manufactured by Waters, inner diameter 3 mm, length 1 m)
Column Co8: Porapak QS 80/100 mesh (manufactured by Waters, inner diameter 3 mm, length 1 m)
Column Co9: Porapak QS 80/100 mesh (manufactured by Waters, inner diameter 3 mm, length 2 m)

In this analyzer, each of the nine separation columns described above was placed in a constant temperature bath controlled to the following temperature. The column Co1 was placed in a constant temperature bath controlled at 160 ° C., and the columns Co2 and Co9 were placed in a constant temperature bath controlled at 90 ° C. The column Co9 is arranged to maintain the resistance applied to the gas flow path under a certain condition.

Next, a method of using this analyzer for detecting three components consisting of methane gas, carbon dioxide and nitrous oxide contained in the atmospheric gas which is an analysis sample will be described.

First, 1 mL of atmospheric gas, which is an analytical sample collected in a vial, was introduced from the sample introduction unit 30 into a gas flow path filled with carrier gas using a gas tight syringe. In this way, a mixed gas of the analysis sample and the carrier gas was prepared.

The mixed gas passes through the columns Co8, Co2 and the column Co1 and flows into the gas flow path having the column Co7 by operating the switch valve 400 until 1.8 minutes have passed from the start of the outflow. Then, 2.5 minutes after the start of the outflow, the switching valve 400 was operated to allow the mixed gas to flow into the gas flow path having the columns Co5 and Co6.

First, methane gas was detected using FID100 2.8 minutes after the analysis sample was introduced from the sample introduction unit 30. In addition. The peak of methane gas was 0.3 minutes from the start of detection by FID100.

Then, 3.9 minutes after the analysis sample was introduced from the sample introduction unit 30, carbon dioxide was detected using TCD200. The peak of carbon dioxide was 0.3 minutes from the start of detection by TCD200.

Then, methane gas was added from the added gas introduction unit 50 to the mixed gas discharged from the TCD200. The added gas is 0.5% of the total amount of carrier gas at a flow rate of 0.15 mL / min of methane gas having a purity of 99.999% or more from the added gas introduction unit 50 after passing through the gas screen filter. Introduced so that. Then, 5.0 minutes after the analysis sample was introduced from the sample introduction unit 30, nitrous oxide was detected using ECD300. In addition. The peak of nitrous oxide was 0.3 minutes from the start of detection by ECD300.

Further, the switching valve 400 is operated, and the FID 100 before and after the mixed gas flows into the gas flow path having the columns Co2, Co1 and Co7 (hereinafter, referred to as before or after the inflow), and the gas having the columns Co5 and Co6. The outlet flow rate of the TCD 200 before and after flowing into the flow path was as follows.
<Before inflow>
FID100 outlet flow rate: 27.4 mL / min
Outlet flow rate 1 of TCD200 (analytical sample + carrier gas): 33.9 mL / min
Outlet flow rate 2 (carrier gas) of TCD200: 34.2 mL / min
<After inflow>
FID100 outlet flow rate: 28.0 mL / min
Outlet flow rate 1 of TCD200 (analytical sample + carrier gas): 34.3 mL / min
Outlet flow rate 2 (carrier gas) of TCD200: 34.2 mL / min

Table 1 below shows the results of detecting three components consisting of methane gas, carbon dioxide and nitrous oxide contained in the atmospheric gas using this analyzer.
Here, the concentrations of methane gas, carbon dioxide, and nitrous oxide contained in the atmosphere used as the measurement sample are methane gas: 1.74 ppm, carbon dioxide: 390 ppm, and nitrous oxide: 319 ppb, respectively.

As can be seen from the results in Table 1, according to this analyzer, when the sample concentration of the three components consisting of methane gas, carbon dioxide and nitrous oxide contained in the atmospheric gas is on the ppb order in one analysis, It was possible to detect at the same time with a high S / N ratio.
The measured concentrations of methane gas, carbon dioxide and nitrous oxide in the above examples were methane gas: 1.74 ppm, carbon dioxide: 390 ppm and nitrous oxide: 319 ppb, respectively.

This application claims priority on the basis of Japanese application Japanese Patent Application No. 2016-0233363 filed on February 10, 2016, and incorporates all of its disclosures herein.

Claims (10)

It is a three-component simultaneous analyzer for detecting three components consisting of methane gas, carbon dioxide and nitrous oxide contained in the atmospheric gas that is the analysis sample.
The three-component simultaneous analyzer
The first gas flow path and
A second gas flow path and a third gas flow path located downstream of the first gas flow path,
Between the first gas flow path and the second gas flow path, and between the first gas flow path and the third gas flow path, the first gas flow path and the first gas flow path. It has a first state in which the two gas flow paths communicate with each other, and a switching valve for switching between the first gas flow path and the second state in which the third gas flow path communicates with each other.
The first gas flow path is
The carrier gas introduction part that introduces the carrier gas and
The sample introduction unit into which the analysis sample is introduced and the sample introduction unit
A first gas phase containing the methane gas and the carbon dioxide are located on the downstream side of the carrier gas introduction section and the sample introduction section and cause a flow delay depending on the type of the component contained in the analysis sample. A first column arranged to obtain a second gas phase containing carbon and the nitrous oxide.
Have,
The second gas flow path is
A hydrogen flame ionization detector for detecting the methane gas contained in the first gas phase is provided at the downstream end.
The third gas flow path is
A second column consisting of packed columns and
A third gas phase containing carbon dioxide and the nitrous oxide are located downstream of the second column and cause a flow delay depending on the type of the component contained in the second gas phase. A third column consisting of a capillary column or a stainless steel column arranged to obtain a fourth gas phase containing nitrous oxide, and
A thermal conductivity type detector for detecting the carbon dioxide contained in the third gas phase on the downstream side of the third column.
An electron capture detector for detecting the nitrous oxide contained in the fourth gas phase, which is located downstream of the thermal conductivity detector.
A three-component simultaneous analyzer. The three-component simultaneous analyzer according to claim 1, wherein the carrier gas introduction unit includes a carrier gas purification device. The three-component simultaneous analyzer according to claim 1 or 2, wherein the column packing material contained in the first column is a styrene polymer fine powder or an effective activated carbon fine powder. The third gas flow path is on the downstream side of the thermal conductivity type detector in the third gas flow path, and is added to introduce the added gas on the upstream side of the electron capture type detector. The three-component simultaneous analyzer according to any one of claims 1 to 3, further comprising a gas introduction unit. The three-component simultaneous analyzer according to any one of claims 1 to 4, wherein the outlet pressure of the third column is smaller than the outlet pressure of the second column. The three components according to any one of claims 1 to 5, wherein the inner diameter of the second column is 1 mm or more and 5 mm or less, and the inner diameter of the third column is 0.1 mm or more and 1 mm or less. Simultaneous analyzer. This is a three-component simultaneous analysis method that detects three components consisting of methane gas, carbon dioxide, and nitrous oxide contained in the atmospheric gas that is the analysis sample.
The carrier gas introduction process that introduces the carrier gas into the gas flow path and
A sample introduction step of introducing the analysis sample into the gas flow path filled with the carrier gas, and
A first gas separation step of obtaining a first gas phase containing methane gas and a second gas phase containing carbon dioxide and nitrous oxide from the components contained in the analysis sample.
A second gas separation step of obtaining a third gas phase containing carbon dioxide and a fourth gas phase containing nitrous oxide from the components contained in the second gas phase.
Have,
The first gas separation step is
A step of passing the analysis sample through a first column for causing a flow delay depending on the type of the component, and
In the subsequent step of the step of passing the gas through the first column, the methane gas introduction step of introducing the first gas phase into a gas flow path having a hydrogen flame ionization detector and the second gas phase are heated. The process of introducing into a gas flow path having a conductivity type detector and an electron capture type detector,
In the subsequent step of the methane gas introduction step, the step of detecting the methane gas contained in the first gas phase by the hydrogen flame ionization detector is included.
The second gas separation step is
A step of passing the second gas phase through a second column composed of a packed column, and
A step of passing the second gas phase through a third column composed of a capillary column or a stainless steel column for causing a flow delay depending on the type of the component.
In the subsequent step of the step of passing the gas through the third column, the thermal conductivity type detector detects carbon dioxide contained in the third gas phase, and the electron capture type detector detects the carbon dioxide contained in the third gas phase. A three-component simultaneous analysis method including a step of detecting nitrous oxide contained therein. The step of detecting nitrous oxide is
The three-component simultaneous analysis according to claim 7, further comprising a step of introducing methane gas or nitrogen gas as an additive gas into the gas flow path between the detection of carbon dioxide and the detection of nitrous oxide. Method. The three-component simultaneous analysis method according to claim 7 or 8, wherein the carrier gas introduction step further includes a step of improving the purity of the carrier gas. The three-component simultaneous analysis method according to any one of claims 7 to 9, wherein the carrier gas is helium gas or nitrogen gas having a purity of 99.999% or more.

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