JP2002340795A - Apparatus for measuring isotope gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To greatly save the trouble and time for measurement with an isotope gas-measuring apparatus utilized in an exhalation-inspecting apparatus for inspecting the presence/absence of pylori bacilli. SOLUTION: A sample cell 16c with a band pass filter 17c is set. The band pass filter 17c selects a wavelength which is different from absorption wavelengths of<12> CO2 and<13> CO2 and is not absorbed by the other substances (wavelength slightly shorter than the absorption wavelength of<12> CO2 by way of an example). A detection signal S3 obtained by receiving light which has passed a sample gas circulating in the sample cell 16c is made a reference when absorbances of the<12> CO2 and<13> CO2 are to be measured. Accordingly, measuring a reference gas for obtaining the reference which is carried out conventionally is eliminated. The need for switching operation between the reference gas and the sample gas is eliminated, so that the measurement can be simplified greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an isotope gas measuring apparatus for measuring a gas to be measured containing carbon dioxide isotopes ¹² CO ₂ and ¹³ CO ₂ using a non-dispersive infrared absorption method. The present invention relates to an isotope gas measurement device suitable for a breath test device for testing the presence or absence of Helicobacter pylori in the stomach of a subject using a so-called urea breath test method.

[0002]

2. Description of the Related Art Conventionally, a method called an isotope tracer method has been used to examine metabolism, accumulation, excretion and the like in a living body. In this method, a substance that behaves in a living body and exhibits the same behavior as the target element or substance to be tracked is labeled with an isotope to form a tracer, and the behavior of the target substance is examined by tracking the isotope.

[0003] As a specific application example, Helicobacter pylori (generally referred to as "H. pylori", henceforth referred to as "H. pylori"), which is said to cause gastric ulcer or duodenal ulcer, exists in the stomach of a subject. There is a test to see if it is. H. pylori has strong urease activity and breaks down urea into carbon dioxide and ammonia. Therefore, urea labeled with ¹³ C, which is a stable isotope of carbon ¹² C, is administered to a subject, and the concentration of ¹³ CO ₂ contained in the breath of the subject (actually, ¹² CO ₂ and ¹³ CO 2 ₂ ). If H. pylori is present in the subject's stomach, ¹³ CO ₂
Should be higher than a normal person without H. pylori, so that the presence or absence of H. pylori can be estimated. This is a test method called a urea breath test method.

More specifically, in order to determine the presence or absence of H. pylori infection, ¹² CO _{2 in} breath before and after administration of a reagent is determined.
Calculate the ratio of the concentrations of and ¹³ CO ₂ . That is, δ ¹³ C (permil) b before the administration of the reagent and δ ¹³ C (permil) a after the administration of the reagent are respectively calculated by equation (1), and the difference Δ ¹³ C
C (per mill) is obtained by the equation (2). δ ¹³ C (per mil) = [( ¹³ CO ₂ concentration in expiration / ¹² CO ₂ concentration in expiration) − ( ¹³ CO ₂ concentration of international standard substance / ¹² CO ₂ concentration of international standard substance)] / 1.12. 372 × 10 ⁻² × 1000 (1) Δ ¹³ C (permil) = δ ¹³ C (permil) b−δ ¹³ C (permil) a (2) When infected with H. pylori, this value is obtained. Is said to increase by 2.5 (per mil) or more.

In such inspections, conventionally, mass spectrometers and infrared spectrophotometers have been generally used for measuring the concentrations of carbon dioxide ¹² CO ₂ and ¹³ CO ₂ . These devices are fairly expensive and cumbersome to operate. Therefore, recently, as a non-dispersive infrared analysis method, a breath test apparatus using an isotope gas measurement apparatus using a simpler filter spectroscopic means is commercially available.

FIG. 5 is a schematic configuration diagram of a conventional isotope gas measuring device using a non-dispersive infrared analysis method. The gas passage system of this apparatus includes a sample gas introduction pipe 40 and an atmosphere introduction pipe 41.
, A carbon dioxide removal filter 42 provided on the air introduction pipe 41, the gas introduction pipe 15, and the sample gas introduction pipe 40.
Alternatively, a three-way valve 43 for selectively connecting the atmosphere introduction pipe 41 to the gas introduction pipe 15 and ¹² CO ₂ connected to the gas introduction pipe 15 are provided.
A first sample cell 16a for measurement, a second sample cell 16b for ¹³ CO ₂ measurement connected to the first sample cell 16a by a connection pipe 18, and an exhaust pipe 19 connected to the second sample cell 16b
And a pump 20 provided on the exhaust pipe 19.

A light source 10, a condenser lens 11, and a rotary chopper 12 for blocking and passing infrared light at a constant period are provided outside one end face of each of the sample cells 16a and 16b. On the other hand, a condensing lens 13 and a photodetector 14 for detecting light passing through the sample cells 16a and 16b, respectively, are disposed outside the opposite end face.

[0008] The first, second sample cell 16a, the light incident side end surface of the 16b, the first bandpass filter 17a for passing the light corresponding to the absorption wavelengths of ¹² CO ₂ and ¹³ CO
_{And a second} bandpass filter 17b for transmitting light corresponding to the _two absorption wavelengths. The first and second band-pass filters 17a and 17b are ¹² CO ₂ and ¹³ C, respectively.
The peak wavelength band of the O ₂ only a interference filter for selectively transmitting, as an example, the first band-pass filter 17a for ¹² CO _2, the center wave number 2360 cm ^-1, the full width at half maximum 80 cm ^-1, whereas the second band-pass filter 17b for ¹³ CO _2, the center wave number 2260 cm ^-1, when the full width at half maximum 70cm ^-1, it is possible to select the peak due to absorption independently of one another.

A general measurement operation using the above-described conventional apparatus is as follows. First, a reference gas (zero gas) serving as a reference is measured. In this example, carbon dioxide CO ₂
Is used as a reference gas. That is, the flow path is set by the three-way valve 43 as shown by the dotted line in FIG. 5, and the pump 20 is operated. As a result, the air is sucked through the air introduction pipe 41, and after the carbon dioxide is removed by the carbon dioxide removal filter 42, the air is introduced into the first sample cell 16a through the gas introduction pipe 15. Then, the gas is diffused and filled inside the first sample cell 16a and the second sample cell 16b, and is discharged to the outside through the exhaust pipe 19.

The chopper 12 is driven to rotate at a predetermined constant rotation speed, whereby the infrared light emitted from the light source 10 is separated from the first and second sample cells 16a and 16b by a predetermined light-shielding period.
And the first and second band pass filters 1
Only the light near the predetermined wavelength is extracted by 7a and 17b and sent into the sample cells 16a and 16b. These monochromatic lights pass through the atmosphere containing no carbon dioxide filled in the sample cells 16a and 16b, are appropriately absorbed, and are introduced into the photodetector 14. Therefore, the photodetector 14 interposes a light receiving signal (ie, a dark current signal or a light receiving signal due to external light) when the chopper 12 blocks light,
Light receiving signals corresponding to the intensities of the light passing through the sample cells 16a and 16b are output alternately. This output signal is output to chopper 1
The signals are distributed to the signals corresponding to the sample cells 16a and 16b in synchronization with the second rotation cycle, and the signals for a predetermined time are integrated by synchronous rectification. This measured value is temporarily stored as a value for the reference gas in each of the sample cells 16a and 16b.

Next, the measurement of the sample gas to be measured is performed.
Run. That is, the three-way valve 43 indicates a solid line in FIG.
The flow path is set so that the pump 20 operates. This
Thereby, the sample gas (exhaust gas) is passed through the sample gas introduction pipe 40.
Gas) is sucked and the first sample cell is
16a. Then, the first and second sample cells 16
a, diffuses and fills inside 16b, passes through exhaust pipe 19
It is discharged outside. At this time, also when measuring the above reference gas
Irradiated with infrared light in the same way as ¹²C
O_Twoas well as¹³CO_TwoLight received as a result of absorption by
A signal is obtained. And the measured value of this sample gas
Calculate the ratio to the measured value of the reference gas,¹²CO _Twoas well as¹³C
O_TwoAnd the absorbance for¹²CO_TwoWhen
¹³CO_TwoThe concentration ratio is determined.

[0012]

As described above, in the conventional isotope gas measuring device, the sample cells 16a, 16b
It is necessary to perform a gas switching operation in which a reference gas containing no carbon dioxide is flowed therein, followed by a sample gas (or vice versa). Further, at the time of such a gas switching operation, it is necessary to secure a sufficient time for replacing the gas in the sample cells 16a and 16b. For this reason, it takes time and effort for the measurement, and it is difficult to increase the processing capacity. In particular, when used as a breath test apparatus in health examinations and the like, it is necessary to perform tests on a large number of subjects skillfully, and there is a demand for improving the processing capacity.

In the above-mentioned conventional isotope gas measuring apparatus, since the sample gas flows in series inside the two sample cells 16a and 16b, it is strictly required to measure the absorbance of ¹² CO ₂ . The sample gas in the first sample cell 16a and the second sample cell 1 for measuring the absorbance of ¹³ CO ₂
The sample gas in 6b is not exactly the same. Since the sample gas receives infrared light and increases in temperature while flowing through the sample cells 16a and 16b, an error due to such a difference in gas temperature between the first sample cell 16a and the second sample cell 16b occurs. Inevitable. Further, as the length of the sample cell becomes longer, the influence of carbon dioxide adsorbing on the inner wall surface of the sample cell cannot be ignored. Such a factor is one factor that hinders improvement in measurement accuracy.

The present invention has been made in view of the above points, and a first object of the present invention is to perform high-precision measurement in a short time without switching between a reference gas and a sample gas. Is to provide an isotope gas measurement device capable of performing the following.

A second object of the present invention is to improve the analysis accuracy by eliminating the influence of component fluctuations and differences in conditions during the passage of the sample gas through the sample cell, and to improve the structure. Is to provide an isotope gas measuring device which is simple.

[0016]

Means for Solving the Problems, Embodiments of the Invention, and
According to the first aspect of the present invention, there is provided the present invention.
Isotope gas analyzer¹²CO_Twoas well as¹³C
O_TwoIs introduced into the sample cell containing¹²CO_Twoas well as
¹³CO_TwoThe absorbance of light having a wavelength corresponding to
By measuring¹²CO_Twoas well as¹³CO_TwoFind the concentration of
In the isotope gas measuring device, a) the gas to be measured is circulated inside,¹²CO_TwoCorresponding to
For measuring the degree of absorption of light having the first wavelength
1) a sample cell, b) the gas to be measured is circulated inside,¹³CO_TwoCorresponding to
For measuring the degree of absorption of light having the second wavelength
C) the gas to be measured is circulated therein, and the first and second cells are
Other objects that are different from the wavelength of and contained in the gas to be measured
Has a third wavelength that is not affected by absorption by quality
A third sample cell for measuring the degree of light absorption, and d) sequentially irradiating the first, second and third sample cells with light.
E) detecting light transmitted through the first, second and third sample cells.
And f) transmitting light through the first sample cell and transmitting light through the third sample cell.
From the detection signal by the light detection means for the overlight¹²CO
_TwoOf the second sample cell and the third sample cell.
Of the transmitted light of the sample cell by the light detecting means
From the signal¹³CO _TwoIs calculated, and the absorbance of both
Than¹²CO_Twoas well as¹³CO_TwoEach concentration and / or both
Computing means for calculating the concentration ratio of the user.

In the isotope gas measuring apparatus according to the first aspect of the invention, instead of the detection signal for the reference gas containing no carbon dioxide, which has been conventionally used as a reference for calculating the absorbance, A detection signal is used for transmitted light having a wavelength at which no carbon dioxide or other light-absorbing substance is present. For this purpose, a third sample cell is prepared. For example, the gas to be measured is flowed in series through the first, second, and third sample cells. When the gas to be measured is exhaled air, many absorption peaks mainly due to water are present in a region having a longer wavelength than the first and second wavelengths corresponding to ¹² CO ₂ and ¹³ CO ₂ . On the other hand, in a region adjacent to the shorter wavelength side than the first and second wavelengths, there is no absorption peak due to another substance. Therefore, it is preferable to select a wavelength in such a region as the third wavelength.

According to the isotope gas measuring apparatus according to the first invention, in a state where the gas to be measured flows through the sample cell without using the reference gas, ¹² CO ₂ and ¹³ CO ₂ contained in the gas to be measured are contained. Can be measured, from which ¹²
The concentration and concentration ratio of CO ₂ and ¹³ CO ₂ can be determined. Therefore, a gas switching operation between the reference gas and the gas to be measured is not required, so that the measurement time can be greatly reduced and the trouble of the measurement can be saved.

In the isotope gas measuring apparatus according to the first invention, the wavelength for obtaining a reference value for calculating the absorbance (that is, the wavelength of light used in the third sample cell) is ¹² CO ₂ and ¹³ CO 2. _Since the wavelength differs from the wavelength of the absorption peak for ₂ , the detection signal may be wavelength-dependent. In some cases, such wavelength dependence can be corrected using the results obtained by preliminary experiments and the like.However, due to factors such as the emission spectrum of the light source fluctuating with temperature, the results obtained in the preliminary calculation In some cases, the correction cannot be made sufficiently.

Therefore, in order to further improve the measurement accuracy, the gas to be measured is circulated inside and the first and second gas are measured.
And a fourth sample cell for measuring the degree of absorption of light having a fourth wavelength which is different from the third wavelength and which is not affected by absorption by another substance contained in the gas to be measured. further provided, on the basis of the detection signal for the fourth detection signal for the light transmitted through the sample cell and light transmitted through said third sample cell, the first time ¹² CO ₂ and ¹³ CO ₂ is zero , The value of the detection signal for the second wavelength may be estimated, and the absorbance of ¹² CO ₂ and ¹³ CO ₂ may be determined using this value.

Further, an isotope gas measuring apparatus according to a second aspect of the present invention, which has been made to solve the above-mentioned problem, comprises a carbon dioxide ¹² C
A gas to be measured containing O ₂ and ¹³ CO ₂ is introduced into the sample cell,
^{In an} isotope gas measuring apparatus for measuring the concentrations of ¹² CO ₂ and ¹³ CO ₂ by measuring the absorbance of light having wavelengths corresponding to ¹² CO ₂ and ¹³ CO ₂ respectively, A) a cylindrical sample cell that is circulated through; b) light irradiating means for irradiating light from one end surface side of the sample cell in a direction substantially parallel to the axial direction thereof; c) a light incident side end surface of the sample cell or A first filter, which is provided on the light emission side end face and selects a wavelength corresponding to the absorption peak of ¹² CO ₂ , and a second filter which selects a wavelength corresponding to the absorption peak of ¹³ CO ₂ , are juxtaposed. D) light distributing means provided outside the light incident side end face of the sample cell and distributing light irradiated from the light irradiating means so as to sequentially pass through the first and second filters. E) passing through the sample cell and the first filter; And light, is characterized by comprising: a light detector for detecting the light transmitted through the said sample cell and the second filter, the.

In the isotope gas measuring apparatus according to the second aspect of the present invention, the sample gas into which the gas to be measured flows is one, and the light irradiation means and the light distribution means make the single sample cell substantially axially inside the single sample cell. Two light beams are alternately irradiated in parallel directions. These two light beams pass through the first and second filters and the inside of the sample cell, respectively, and are detected by the light detecting means. In the light detecting means, the same as in the case where two sample cells are provided as in the related art. Then, a detection signal for transmitted light absorbed by ¹² CO ₂ and a detection signal for transmitted light absorbed by carbon dioxide ¹³ CO ₂ are alternately output.

Therefore, the isotope gas measuring apparatus according to the second aspect of the invention can measure gas components ( ¹² CO ₂ and ¹³ CO ₂ ) contained in exactly the same gas to be measured and having different molecular absorption coefficients. Therefore, it is possible to achieve high measurement accuracy without being affected by an increase in temperature due to infrared light absorption or adsorption to the inner wall of the sample cell.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the isotope gas measuring apparatus according to the first invention will be described below with reference to FIGS.

FIG. 1 is a schematic configuration diagram of an isotope gas measuring apparatus according to this embodiment. Components that are the same as or correspond to those in the device shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted unless otherwise required. In the apparatus of this embodiment, ¹² CO
_{In addition} to the first sample cell 16a for measuring ₂ and the second sample cell 16b for measuring ¹³ CO ₂ , a third sample cell 16c for obtaining a detection signal serving as a reference when calculating absorbance is provided. Is provided. That is, the gas introduction pipe 15
The sample gas that has flowed further into the first sample cell 16a flows into the third sample cell 16c via the connection pipe 18a, further flows into the second sample cell 16b via the connection pipe 18b, and finally the exhaust pipe 19 Is discharged to the outside through The chopper 12 converts the infrared light emitted from the light source 10 into first to third infrared light.
The sample is sequentially distributed to the sample cells 16a to 16c.

The feature of this apparatus is that a third sample cell 16c is provided instead of providing the switching mechanism between the sample gas and the reference gas as described above, and the third sample cell 16c filled with the sample gas is provided.
The point is that the absorbance is calculated using the detection signal for the light transmitted through c as a reference (that is, instead of the measurement result for the conventional reference gas).

FIG. 2 is an example of an absorbance spectrum of exhaled air. In FIG. 2, P1 is the peak of the absorption wavelength due to ¹² CO ₂ , and P2 is the peak of the absorption wavelength due to ¹³ CO ₂ . As described above, the center wave number 2360 cm ^-1 as the first band-pass filter 17a, that of the full width at half maximum 80 cm ^-1 (Fig. 2
Wavenumber region B1) can extract the peak P1 by using the in center wavenumber 2260 cm ^-1 as a second band pass filter 17b, be used as the full width at half maximum 70cm ^-1 to (wavenumber region B2 in Fig. 2) peak P2 can be extracted.

Further, a wave number position to be used as a reference is set to a wave number that does not overlap with the peaks P1 and P2 and a wave number that does not have absorption by substances other than CO ₂ . Although not clearly shown in FIG. 2, a large number of small peaks due to absorption of H ₂ O exist in a region having a smaller wave number (that is, a longer wavelength) than the wave number region B2. Is inappropriate. On the other hand, wave number region B1
A region adjacent to a region having a higher wave number (that is, a shorter wavelength) has no peak due to absorption of another substance, and thus is suitable as such a reference. Thus, the third bandpass filter 17c has a center wave number of 2460 cm.
^-1 , full width at half maximum 80 cm ^-1 (wave number region B in FIG. 2)
Use 3).

In the apparatus having the above configuration, the first to third trials are performed.
Exhaled air to be measured is flowed through the charge cells 16a to 16c,
While rotating the chopper 12 at a substantially constant rotation speed, each sample
The light transmitted through the cells 16a to 16c is detected by the photodetector 14.
Detect sequentially. An operation receiving a detection signal from the photodetector 14
The processing unit 30 converts the detection signal into a rotation of the chopper 12.
Distribute synchronously. As a result, each detection signal
Contained in gas¹²CO _TwoTo the transmitted light absorbed by
Detection signal S1, which is also contained in the sample gas¹³CO_TwoTo
The detection signal S2 for the transmitted light absorbed by
Transmission hardly affected by absorption by components in the sample gas
It is divided into a detection signal S3 for light. It should be noted that
As described above, the detection signal obtained when the light is blocked by the chopper 12 is
Process to remove the effects of dark current and external light.
You may.

In the arithmetic processing unit 30, the gas contained in the sample gas is used.
¹²CO_Twoas well as¹³CO_TwoConventionally used to calculate the absorbance of
Instead of the measured value of the reference gas,
Use as a standard value. That is, whether the detection signals S1 and S3
La¹²CO_TwoIs calculated from the detection signals S2 and S3.
¹³CO_TwoThe absorbance of is calculated. Furthermore, this¹²CO_Twoas well as ¹³
CO_TwoFrom the absorbance of¹²CO_TwoWhen¹³CO_TwoThe concentration ratio of
You. In order to determine such a concentration ratio, for example,
CO of known concentration_TwoCreated based on the result of measuring
The obtained calibration curve can be used. And this
Equations (1) and (2) are obtained from the calculated concentration ratios.
Using Δ¹³Calculate C (per mill).

As described above, in the apparatus of this embodiment, the result of measuring the sample gas is used as a reference for calculating the absorbance without using a reference gas as in the conventional apparatus.
A mechanism for switching between the reference gas and the sample gas is not required, and such a gas switching operation is not required. Therefore, measurement can be performed very efficiently.

In the apparatus of the present embodiment, the detection signals S1 and S3, S2 and S3 when calculating the absorbance are all the measurement results of the transmitted light having different wave numbers (wavelengths). If the measurement wavelengths are not the same, for example, a difference in emission intensity depending on the wavelength in the light source 10 and a difference in detection sensitivity depending on the wavelength in the photodetector 14 cause an error. It is desirable. Such wavelength dependence appears as, for example, the inclination of the straight line of the base portion excluding peaks near the wavenumber regions B1, B2, and B3 or the curvature of the curve in FIG. Therefore, if the state of the base portion is known in advance, the error caused by the difference in wavelength can be corrected quite appropriately.

However, for example, the wavelength dependence of the light emission intensity of the light source 10 may greatly vary depending on the light emission temperature, and it takes a considerable time for the temperature to sufficiently rise and stabilize. When the measurement is performed under unstable conditions, the error cannot be sufficiently eliminated even by the above-described correction. Therefore, in such a case, the following configuration can be adopted.

That is, the peaks P1 and P2 do not overlap, and C
A fourth sample cell provided with a fourth band-pass filter having a wave number region (for example, wave number region B4 in FIG. 2) that does not absorb by substances other than O ₂ and does not completely overlap with wave number region B3. In addition, the light having the wavelength selected by the fourth band-pass filter is transmitted through the sample gas, and the detection signal S4 is obtained by the photodetector 14. The detection signals S3 and S4 are both measurement results for transmitted light that is not absorbed by CO ₂ or other substances, but are affected by the wavelength dependence as described above because the wavelengths of the light are different. The values are different from each other (of course, they may be the same). Therefore, from the detection signals S3 and S4, a detection signal for a gas concentration of zero at each absorption wavelength of ¹² CO ₂ and ¹³ CO ₂ is estimated, and from the estimated value and the detection signals S 1 and S 2, ¹² CO ₂ and ¹³ CO ₂ are detected. The absorbance of CO ₂ is calculated. As a result, the wavelength dependency is corrected more accurately, and the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ can be obtained with high accuracy.

Next, an embodiment of the isotope gas measuring apparatus according to the second invention will be described with reference to FIGS.

FIG. 3 is a schematic configuration diagram of the isotope gas measuring apparatus according to the present embodiment, and FIG. 4 is a plan view of the filter 27 and the chopper 22 in FIG. Note that the same or corresponding components as those of the apparatus shown in FIGS. 1 and 5 are denoted by the same reference numerals, and description thereof will be omitted unless particularly necessary. Further, in this device, a gas switching mechanism such as a three-way valve is provided on the upstream side of the gas introduction pipe 15 similarly to the apparatus of FIG.
9 is provided with a pump, but is not shown in FIG.

The characteristics of the apparatus of this embodiment are as follows: ¹² CO ₂ and ¹³ CO ₂
In order to use a common sample cell 26 for measuring CO ₂ and irradiate the sample cell 26 with two lights having absorption peak wavelengths of ¹² CO ₂ and ¹³ CO ₂ respectively alternately and substantially in parallel, FIG. 4 shows the structure of the chopper 22 and the filter 27.
The point is as shown in the figure. That is, chopper 2
2 is rotated about the axis 22c, the opening 22a on the outer peripheral side and the opening 22b on the inner peripheral side of the chopper 22 alternately face each other on the light incident side end face of the sample cell 26. In the filter 27, a first band-pass filter portion 27a having the same wave number region as the first band-pass filter 17a is provided at a position facing the outer-peripheral opening 22a.
The second band pass filter 17 is located at a position where
a second band-pass filter unit 2 having the same wave number region as b
7b is provided. Therefore, light having an absorption peak wavelength of ¹² CO ₂ and light having an absorption peak wavelength of ¹³ CO ₂ are alternately transmitted through the sample cell 26. In addition,
The processing after the detection of the transmitted light and the measurement procedure including the switching operation between the sample gas and the reference gas are the same as those of the above-described conventional isotope gas measuring apparatus, and therefore the description thereof is omitted.

In this isotope gas measuring apparatus, the measurement for ¹² CO ₂ and the measurement for ¹³ CO ₂
The conditions (temperature and components) of the sample gas flowing through are almost the same. Therefore, the measurement can be performed with extremely high accuracy without being affected by a temperature rise due to light absorption or a component fluctuation due to adsorption or the like as in the related art.

It is to be noted that each of the above embodiments is merely an example, and it is obvious that various modifications and modifications are possible within the scope of the claims described in the claims of the present application.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of an isotope gas measurement device according to an embodiment of the first invention.

FIG. 2 is a graph showing an example of an absorption spectrum of breath.

FIG. 3 is a configuration diagram of a main part of an isotope gas measurement device according to an embodiment of the second invention.

FIG. 4 is a plan view of a filter and a chopper in the isotope gas measurement device of FIG.

FIG. 5 is a configuration diagram of a main part of a conventional isotope gas measurement device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Light source 11, 13 ... Condensing lens 12, 22 ... Chopper 22a ... Outer side opening 22b ... Inner side opening 22c ... Axis 14 ... Photodetector 15 ... Gas introduction pipe 16a ... First sample cell 16b ... Second sample Cell 16c Third sample cell 17a First bandpass filter 17b Second bandpass filter 17c Third bandpass filter 18a, 18b Connection pipe 19 Exhaust pipe 20 Pump 26 Sample cell 27 Filter 27a First bandpass filter unit 27b Second bandpass filter unit 30 Arithmetic processing unit

Continued on front page F-term (reference) 2G057 AA01 AB02 AB06 AC03 BA01 GA04 2G059 AA01 BB01 CC04 DD12 DD13 EE01 EE12 GG07 HH01 JJ02 JJ03 JJ11 JJ24 KK01 MM01 4B029 AA07 FA03 FA12 4B063 QA01 QAQ QAQ1 QAQ1QAQ1

Claims (2)

[Claims] 1. Carbon dioxide¹²CO_Twoas well as¹³CO_TwoIncluding
The measurement gas is introduced into the sample cell,¹²CO_Twoas well as¹³CO_TwoTo
Measuring the absorbance of light with the corresponding wavelength
By¹²CO_Twoas well as¹³CO_TwoGas measurement to determine the concentration of
A) the gas to be measured is circulated inside,¹²CO_TwoCorresponding to
For measuring the degree of absorption of light having the first wavelength
1) a sample cell, b) the gas to be measured is circulated inside,¹³CO_TwoCorresponding to
For measuring the degree of absorption of light having the second wavelength
C) the gas to be measured is circulated therein, and the first and second cells are
Other objects that are different from the wavelength of and contained in the gas to be measured
Has a third wavelength that is not affected by absorption by quality
A third sample cell for measuring the degree of light absorption, and d) sequentially irradiating the first, second and third sample cells with light.
E) detecting light transmitted through the first, second and third sample cells.
And f) transmitting light through the first sample cell and transmitting light through the third sample cell.
From the detection signal by the light detection means for the overlight¹²CO
_TwoOf the second sample cell and the third sample cell.
Of the transmitted light of the sample cell by the light detecting means
From the signal¹³CO _TwoIs calculated, and the absorbance of both
Than¹²CO_Twoas well as¹³CO_TwoEach concentration and / or both
And an arithmetic processing means for calculating a concentration ratio of the isotope gas. _2. A gas to be measured containing carbon dioxide ¹² CO ₂ and ¹³ CO ₂ is introduced into a sample cell, and the absorbance of light having a wavelength corresponding to ¹² CO ₂ and ¹³ CO ₂ is measured to obtain ¹² CO 2. _{In the} isotope gas measuring apparatus for determining the concentration of ₂ and ¹³ CO ₂ , a) a cylindrical sample cell through which the gas to be measured flows, and b) an axial direction from one end surface side of the sample cell. A light irradiating means for irradiating light in a direction substantially parallel to c) a first means for selecting a wavelength corresponding to an absorption peak of ¹² CO ₂ , which is provided on a light incident side end face or a light exit side end face of the sample cell; A wavelength selecting means in which a filter and a second filter for selecting a wavelength corresponding to the absorption peak of ¹³ CO ₂ are arranged in parallel. D) The light irradiation means is provided outside the light incident side end face of the sample cell. The light emitted from the means is passed through the first and second filters in order Light distributing means for distributing the light so as to pass through, e) light detecting means for detecting light transmitted through the sample cell and the first filter and light transmitted through the sample cell and the second filter. An isotope gas measurement device characterized by the above-mentioned.