JP2002350340A - Apparatus and method for measuring isotopic gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the deterioration of accuracy for calculating a ratio of concentration between<12> CO2 and<13> CO2 due to influence by mutual interference in absorption of the<12> CO2 and the<13> CO2 . SOLUTION: A plurality of data having three parameters of the ratio of concentration and absorbances of the<12> CO2 and the<13> CO2 are obtained by measuring reference gases that a plurality of gases having known ratios of concentration are diluted in phases. An analytical surface that an analytical curve is three-dimensionally extended in a three-dimensional space having three axes of the parameters, is formed. Data representing the analytical surface are stored in a memory 33. When a sample gas having an unknown ratio of concentration is measured, the absorbances of the<12> CO2 and<13> CO2 are found and a calculating part 32 of the ratio of concentration directly calculates the ratio of concentration δ<13> C from two absorbances by referring to the data in the memory 33. The complicated analytical curve to consider and eliminate the mutual interference does not need to be found. An error component is eliminated and the ratio of concentration can be accurately calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is carbon dioxide ¹² CO
_{2 and} an isotope gas measuring device and a measuring method for measuring a gas to be measured containing ¹³ CO ₂ which is a stable isotope using a non-dispersive infrared absorption method, more specifically, using a so-called urea breath test method. The present invention relates to an isotope gas measurement device and a measurement method suitable for a breath test device for testing the presence or absence of Helicobacter pylori in the stomach of a subject.

[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, the concentration of ¹³ CO ₂ should be higher than that of a normal person without H. pylori. Can be. This is a test method called a urea breath test method.

In such an inspection, conventionally, ¹² CO ₂
In general, mass spectrometers and infrared spectrophotometers have been used for measuring the concentration of ¹³ CO ₂ , but these devices are rather expensive and cumbersome to operate. Therefore, recently, an isotope gas measuring apparatus using a non-dispersive infrared analysis method using wavelength selection of infrared light by an interference filter has been used (for example, see Japanese Patent No. 2947737).

In such a conventional isotope gas measuring apparatus, a calibration curve representing the relationship between absorbance and concentration is used to calculate the concentrations of ¹² CO ₂ and ¹³ CO ₂ contained in the gas to be measured. That is, in advance, a calibration curve representing the relationship between the absorbance and the concentration of ¹² CO ₂ was created based on the result of measuring a standard gas containing a known concentration of ¹² CO ₂ , and separately from this,
A calibration curve representing the relationship between the absorbance and the concentration of ¹³ CO ₂ is created based on the result of measuring a standard gas containing ¹³ CO ₂ at a known concentration. Then, using the exhaled gas before and after administering the reagent containing urea to a living body as a gas to be measured, the infrared absorbances of ¹² CO ₂ and ¹³ CO ₂ contained in the gas to be measured are measured, and the two calibration curves are obtained. ^{12 in the} gas to be measured
The concentration of CO _{2 and} the concentration of ¹³ CO ₂ are determined. Then, from the calculated values of these concentrations, ¹² CO ₂ and ¹³ CO ₂
Is calculated.

[0006]

However, the infrared absorption wavelengths of carbon dioxide ¹² CO ₂ and its stable isotope ¹³ CO ₂ are close to each other (the difference is about 130 n).
m), and the isotope abundance ratio is as small as about 1.1% in general atmosphere. Therefore, using an interference filter, ¹² CO ₂ and
^With the method of reducing the mutual interference effect by extracting the infrared light of the specific wavelength range corresponding to each of ¹³ CO ₂ , it is inevitable that the interference effect of ¹² CO ₂ remains strongly in the measurement result of ¹³ CO ₂ . Moreover, the interference effect of ¹² CO ₂ for ¹³ CO ₂ is often appear non-linearly with its concentration. When preparing a calibration curve representing the relationship between absorbance and concentration, it is necessary to find a calibration curve that can eliminate the influence of interference between ¹² CO ₂ and ¹³ CO ₂ as described above. In some cases, the influence of interference varies nonlinearly depending on the gas concentration, and it is very difficult to create a calibration curve that can completely eliminate the influence of interference.
As a result, ¹² error occurs CO ₂ and the absorbance of ¹³ CO ₂ in calculating the density, respectively, ¹² C, which is calculated therefrom
Errors also occur in the concentration ratio between O ₂ and ¹³ CO ₂ .

As described above, in the conventional method, the absorbance is increased.
Calculate the concentration using the calibration curve even when measuring with high accuracy
An error occurred during the process, and the presence or absence of H. pylori was determined.
When a situation arises in which an indeterminate decision must be made when
There is a problem. The present invention has been made in view of such a point.
The main purpose is to¹²CO
_TwoWhen¹³CO_TwoDue to close absorption wavelengths
Eliminate interference effects, ¹²CO_TwoWhen¹³CO_TwoHigh concentration ratio of
Isotope gas measurement device and
It is to provide a setting method.

[0008]

[MEANS FOR SOLVING THE PROBLEMS]
The isotope gas measuring device according to the present invention made in
A measuring cell through which gas flows, and an infrared
A light source for irradiating light, and infrared light transmitted through the measurement cell.
And a detector for receiving light.¹²CO _TwoAnd that
Is a stable isotope of¹³CO_TwoThe measured gas containing
Introduced to the fixed cell, ¹²CO_Twoas well as¹³CO_TwoCorresponding to each
Gas measurement to measure the absorbance of infrared light with different wavelengths
A) in the setting device¹²CO_TwoWhen¹³CO_TwoThe concentration ratio of
Created based on the measurement results for several standard gases
The¹²CO_TwoWhen¹³CO_TwoConcentration ratio of¹²CO_TwoAbsorbance,
as well as¹³CO_TwoIn a three-dimensional space with the absorbance of
Storage means for storing data representing the calibration plane of b)¹²
CO_TwoWhen¹³CO_TwoMeasured gas whose concentration ratio is unknown
Into the cell, ¹²CO_Twoas well as¹³CO_TwoCorresponding to each
For measuring the absorbance of infrared light having different wavelengths
And c) data representing the calibration surface stored in the storage means.
By reference, obtained by the absorbance measurement means¹²CO_Two
as well as¹³CO_TwoCalculate the unknown concentration ratio from the absorbance of
And a concentration ratio calculating means.

Further, the present invention has been made to solve the above problems.
The method for measuring an isotope gas according to the present invention includes the steps of:
And irradiating the measurement cell with infrared light
A light source that receives infrared light transmitted through the measurement cell.
And a carbon dioxide ¹²CO_TwoAnd its stable isotope
Body¹³CO_TwoTo be measured into the measuring cell
Enter¹²CO_Twoas well as¹³CO_TwoHave wavelengths corresponding to
Using an isotope gas measuring device to measure the absorbance of infrared light
And¹²CO_TwoWhen¹³CO_TwoThe gas to be measured whose concentration ratio is unknown
A method for determining the concentration ratio of¹²CO_TwoWhen¹³CO_TwoOf several types with known concentration ratios
Introduce the reference gas into the measuring cell,¹²CO_Twoas well as¹³CO_TwoNiso
Measure the absorbance of infrared light having the corresponding wavelength,
Based on the measurement results¹²CO_TwoWhen¹³CO_TwoConcentration ratio of¹²
CO_TwoAbsorbance, and¹³CO_TwoThe absorbance of
A calibration surface in a three-dimensional space is created, and data representing the calibration surface is created.
Calibration surface creation step to retain data, b)¹²CO_TwoWhen¹³CO_TwoGas to be measured whose concentration ratio is unknown
Introduce into the measuring cell, ¹²CO_Twoas well as¹³CO_TwoTo each
Absorbance measurement to measure the absorbance of infrared light having a corresponding wavelength
C) by referring to data representing the calibration surface,
Obtained by means of absorbance measurement¹²CO_Twoas well as¹³CO_TwoSucking
A density ratio calculation step for calculating the unknown density ratio from the luminous intensity.
And is characterized by including.

[0010]

Embodiments and effects of the present invention For example, the presence or absence of H. pylori
Gas used in the urea breath test, etc.
Measurement device, it is contained in the gas to be measured (exhaled air)¹²C
O_Twoas well as¹³CO_TwoAre not required,
I want to¹²CO_TwoWhen¹³CO₂Is the concentration ratio. Therefore,
In the isotope gas measuring device and measuring method according to the present invention,
As if¹²CO _Twoas well as¹³CO_TwoAfter measuring the absorbance of
Refer to the absorbance vs. concentration calibration curve from each absorbance
do it¹²CO_Twoas well as¹³CO_TwoCalculate the concentration of
¹²CO_TwoWhen^{1 Three}CO_TwoTwo-stage line to find the concentration ratio with
Instead of going through¹²CO_TwoAbsorbance and¹³CO_TwoSucking
Directly from luminosity¹²CO_TwoWhen¹³CO_TwoCalculate the concentration ratio of
You. for that reason,¹²CO_TwoWhen¹³CO_TwoConcentration ratio of¹²CO_Two
Absorbance, and¹³CO_TwoWith absorbance of 3 as a parameter
Use the calibration surface in the dimensional space. "Calibration surface" here
Is a three-dimensional calibration curve drawn in a conventional two-dimensional plane.
This is a concept extended to space.

In order to create such a calibration surface, ¹² C
A plurality of standard gases obtained by diluting a plurality of gases having known concentration ratios of O ₂ and ¹³ CO ₂ in a plurality of stages (the concentration ratio is unchanged at this time) are measured, and each standard gas is measured. In
The absorbance of ¹² CO _{2 and} the absorbance of ¹³ CO ₂ are calculated. As a result, a plurality of data having three parameters of the concentration ratio of ¹² CO ₂ to ¹³ CO ₂ , the absorbance of ¹² CO ₂ , and the absorbance of ¹³ CO ₂ are obtained, and the three parameters are set as axes orthogonal to each other. These data are arranged in a three-dimensional space, and a calibration surface for interpolating between the data is created. The storage means may store, as data representing the calibration surface, for example, a calculation formula or a table for obtaining two absorbances as inputs and obtaining a concentration ratio as an output.

Since the calibration surface is prepared based on the result of measuring a standard gas containing both ¹² CO ₂ and ¹³ CO ₂ , the parameter ¹² CO ₂ , which constitutes the calibration surface, is used.
And the ^{1 3} CO ₂ absorbance includes the influence of mutual interference (however, the actual interference ¹³ CO ₂ for ¹² CO ₂ in the most negligible, only the interference of ¹² CO ₂ for ¹³ CO ₂ Is a problem). Therefore, as in the past, when creating a calibration curve, it is necessary to consider the mutual interference effect between ¹² CO ₂ and ¹³ CO ₂ and to create a calibration curve so as to eliminate the influence. Not required, ¹² CO in gas to be measured
When calculating the concentration ratio from the absorbances of ₂ and ¹³ CO ₂ , little error occurs due to the mutual interference effect.

Therefore, according to the isotope gas measuring apparatus and the measuring method according to the present invention, ¹² CO contained in the gas to be measured is contained.
_Since the concentration ratio of ₂ to ¹³ CO ₂ can be obtained more accurately than in the past, if this device and method are applied to a breath test device, it can be more accurately determined whether or not the subject has H. pylori. It is possible to make a determination.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a breath test apparatus using an isotope gas measuring apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a breath test apparatus according to this embodiment. The gas flow path system of the apparatus includes a flow path switching unit 22 including first and second valves 23 and 24 for switching between the sample gas and the reference gas and flowing the gas to the gas introduction pipe 21;
A first measurement cell 14 having a short cell length, a second measurement cell 17 having a long cell length, and first and second measurement cells 14,
17, an exhaust pipe 25 connected near one end of the second measurement cell 17, and a pump 26 and a flow sensor 27 provided on the exhaust pipe 25.

Each of the first measuring cell 14 and the second measuring cell 17 has a substantially cylindrical shape, and is arranged so that the central axes of the two are substantially coincident with each other and a predetermined distance is provided between opposing end faces. ing. At the center of the gap, a light source 10 that emits infrared light on both sides and choppers 11 and 12 that are coaxially rotated by a motor 13 on both sides of the light source 10 are provided. As the light source 10, for example, a ceramic heater can be used. Each of the choppers 11 and 12 has an opening at a predetermined position, and irradiates the measuring cells 14 and 17 with infrared light intermittently as the chopper rotates. First measurement cell 1
On the opposite end faces of the fourth and second measuring cells 17, ¹²
In order to selectively pass infrared light having an absorption wavelength of CO ₂ and ¹³ CO ₂ , a band-pass first interference filter 15 having center wavelengths of 4250 nm and 4415 nm is used.
And a second interference filter 18 are attached, and further outside, a first detector 16 and a second detector 19 are installed. As the first and second detectors 16 and 19, detectors using PbSe as light receiving elements are used, but other detectors such as a pyroelectric detector may be used. The first and second detectors 1
6 and 19 are maintained at about −20 ° C. by a temperature control unit (not shown) in order to keep the detection sensitivity constant. The first and second interference filters 15 and 18 are maintained at about 25 ° C. by a temperature control unit (not shown) in order to prevent a change in wavelength transmission characteristics due to a temperature rise due to irradiation of infrared light. Has become.

The detection outputs of the first and second detectors 16 and 19 are both input to an arithmetic processing unit 30. The arithmetic processing unit 30 includes, as its functions, an absorbance calculation unit 31, a concentration ratio calculation unit 32, and a calibration surface memory 33.
After the digital conversion, a calculation process described later is performed to calculate the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ . On the other hand, the control unit 40 controls the operation of each unit of the present apparatus.

In the apparatus of this embodiment, the first measuring cell 14 has a cell length of 25 mm, and the second measuring cell 17 has a cell length of 250 mm.
mm. The reason why the cell lengths of the two measurement cells 14 and 17 are greatly different in this way is that the concentration of the target carbon dioxide is greatly different, so that the effects of light attenuation due to the absorption of the two are adjusted to the same degree. Detectors 16, 19
The reason is that the linearity of the input-to-output characteristic of the above is operated within a favorable range.

In the present apparatus, a standard gas having a known concentration ratio is measured, a calibration surface is created based on the measurement result, and data representing the calibration surface is stored in the calibration surface memory 33. The processing procedure at that time is shown in the flowchart of FIG.
As the standard gas, a gas obtained by serially diluting a plurality of gases whose concentration ratios of ¹² CO ₂ and ¹³ CO ₂ are known is used.

(I) Measurement of reference gas First, measurement of a reference gas (zero gas) is executed (step S1). As the reference gas, for example, the air from which carbon dioxide CO ₂ has been removed can be used. That is, the switching of the flow path by the flow path switching unit 22 and the operation of the pump 26 cause the reference gas to flow through the first and second measurement cells 1 through the gas introduction pipe 21.
4 and 17 are introduced. The reference gas is the first and second measurement cells 1
4, 17 are diffused and filled inside, and discharged through the exhaust pipe 25 to the outside.

The infrared light emitted from the light source 10 to both sides is intermittently transmitted by the choppers 11 and 12 (for example, the intermittent frequency is set to about 700 Hz).
After passing through the atmosphere that does not contain CO ₂ filled inside the measurement cells 14 and 17 and receiving appropriate absorption, the first and second
The light reaches the interference filters 15 and 18. Then, only the light of the specific wavelength range is extracted by the first and second interference filters 14 and 17, respectively, and the first and second detectors 16 and 1 are extracted.
9 is introduced. Since the infrared transmitted light is intermittent, the first and second detectors 16 and 19 receive the light receiving signal corresponding to the light receiving intensity when light passes and the light receiving signal corresponding to the light receiving intensity when light is blocked (that is, dark light). A current signal and a light receiving signal due to external light) are alternately output in accordance with the above-mentioned intermittent cycle.

In the arithmetic processing section 30, the absorbance calculating section 31
Receives the detection signals from the first and second detectors 16 and 19, receives a timing signal synchronized with the intermittent cycle from the control unit 40, and integrates the respective detection signals for a predetermined time by synchronous rectification. At this time, the first and second
Measurement value (signal integrated value) R12 corresponding to detectors 16 and 19
And R13 are temporarily stored internally as values for the reference gas (step S2).

(Ii) Measurement of sample gas (standard gas) Next, measurement of the standard gas to be measured is executed (step S4). That is, by the switching of the flow path by the flow path switching unit 22 and the operation of the pump 26, the standard gas having a known concentration ratio of ¹² CO ₂ and ¹³ CO ₂ is supplied to the first and second measurement via the gas introduction pipe 21. The cells are introduced into cells 14 and 17. Then, they are diffused and filled in the first and second measurement cells 14 and 17, and discharged through the exhaust pipe 25 to the outside. The light source 10 and the choppers 11 and 12 are driven in the same manner as in the measurement of the reference gas. At this time, the signals detected by the first and second detectors 16 and 19 are integrated in the absorbance calculator 31 in the same manner. When measuring the standard gas, the infrared light emitted from the light source 10 is strongly absorbed by CO ₂ contained in the standard gas.
Since the first interference filter 15 extracts only the vicinity of the absorption wavelength of ¹² CO ₂ , the first detector 16 extracts ¹² CO ₂
Only the infrared light affected by the absorption due to absorption is detected. On the other hand, since only the absorption wavelength is extracted by ¹³ CO ₂ in the second interference filter 18, ¹³ in the second detector 19 CO ₂
Only the infrared light affected by the absorption due to absorption is detected. At this time, the measured values (signal integrated values) corresponding to the first and second detectors 16 and 19 are S12 and S13 (step S12).
4).

Further, the absorbance calculator 31 calculates the absorbance A1 of ¹² CO ₂ from the measured values R12, R13, S12 and S13.
2, and it obtains the ¹³ CO ₂ absorbance A13 based on the following equation (step S5). A12 = -ln (S12 / R12) A13 = -ln (S13 / R13) Thus, in response to the concentration ratio of ¹² CO ₂ and ¹³ CO _2, ¹²
Absorbance A12 and ¹³ CO ₂ absorbance A13 of CO ₂ is obtained (step S6).

Measurements for all prepared standard gases are completed.
If not completed ("N" in step S7),
Return to step S3,¹²CO_TwoWhen¹³CO_TwoIs the same as above.
Multiple targets diluted with one gas at different dilutions
Repeat the above measurement for the reference gas, further,¹²
CO_TwoWhen¹³CO_TwoGases with different concentration ratios
Repeat the same measurement for the standard gas
And do it. And the resulting,¹²CO_TwoWhen¹³CO_Two
Concentration ratio δ¹³C,¹²CO_TwoAbsorbance A12, and^{1 Three}CO_Twoof
The point that three parameters of absorbance A13 are set as one set
Are arranged in a three-dimensional space with parameters as axes.
(Step S)
8). Note that the concentration ratio δ¹³C is a value determined by the following equation. δ¹³C (unit: per mil) = [((in sample gas)¹³CO_Two
Concentration / in sample gas ¹²CO_TwoConcentration)-(of international reference material
¹³CO_TwoConcentration / International reference material¹²CO_TwoConcentration)] / (international
Reference material¹³CO_TwoConcentration / International reference material¹²CO_Twoconcentration)
× 1000

FIG. 2 shows data obtained by the above measurement in a three-dimensional space. As described above, the measurement data is discrete, but a calibration surface is created by interpolating the measurement data based on the measurement data.
A calculation formula representing the calibration surface or a data group (a set of δ ¹³ C, A12, A13) on the calibration surface is obtained and stored in the calibration surface memory 33 (step S9). Therefore, when a calculation formula is stored in the calibration surface memory 33, the concentration ratio calculation unit 32 applies the absorbance of ¹² CO _{2 and} the absorbance of ¹³ CO ₂ given from the absorbance calculation unit 31 to the above calculation formula. Thus, the concentration ratio δ ¹³ C can be calculated. When the data group on the calibration surface is stored in the calibration surface memory 33, the concentration ratio calculation unit 32
Input the absorbance of ¹² CO _{2 and} the absorbance of ¹³ CO ₂ given from the absorbance calculation unit 31 to the calibration surface memory 33, and calculate the concentration ratio δ ¹³ C output from the calibration surface memory 33 according to the calculation result. can do.

As described above, the absorption wavelength of ¹² CO ₂ and ¹³ C
Since it is close to the absorption wavelength of O ₂ , it is difficult to completely separate the absorption wavelength ranges of both components by the interference filter. Therefore, when a gas containing both ¹² CO ₂ and ¹³ CO ₂ is measured, they are mutually affected by absorption by the other component. However, ¹³ because existence ratio of CO ₂ is about 1% of the ¹² CO _2, whereas the influence of the ¹³ CO ₂ of interference to ¹² CO ₂ is negligible negligible, ¹² for ¹³ CO ₂ Since the influence of the CO ₂ interference is large, only the latter is an effect that appears substantially. Since the absorbance of ¹² CO ₂ and ¹³ CO ₂ at one point of measurement data for constituting the above calibration surface is a result of measuring a standard gas containing both ¹² CO ₂ and ¹³ CO ₂ , These absorbances include the influence of the mutual interference as described above.

Note that the above-described operation of creating the calibration surface may be performed by the user who measures the unknown sample gas, but usually, the manufacturer of the device adjusts the device before shipment. Execute as one of the operations in the process,
It is convenient to store the data representing the calibration plane obtained as a result in the calibration plane memory 33 which is a nonvolatile memory. Of course, the light source 10, the interference filter 15,
Since the calibration surface may be changed when the detectors 18 and the detectors 16 and 19 are replaced, the data stored in the calibration surface memory 33 can be changed by performing a predetermined operation even after shipment. A function of rewriting to match the state of the device may be provided.

Using the above device,¹²CO_TwoWhen¹³CO_Twoof
When measuring sample gas (exhaled air) whose concentration ratio is unknown
Is as follows. That is, similar to the procedure described above,
CO _TwoFirst, a reference gas not containing
And the measured values (signal integration) corresponding to the second detectors 16 and 19
Is temporarily stored as a value for the reference gas. Uh
This time, the sample gas is supplied to the first and second measurement cells 14 and 17.
Introduce the sample gas¹²CO_Twoas well as¹³CO_Twoby
The absorbed infrared light is detected by the first and second detectors 16 and 19.
From the measured value and the previously obtained measured value¹²
CO_Twoas well as¹³CO_TwoThe absorbance of each is determined. Soshi
Therefore, the concentration ratio calculation unit 32 stores the data in the calibration surface memory 33.
Referring to the data representing the calibration surface¹²CO_Twoas well as¹³CO_Two
From the absorbance of the concentration ratio δ¹³Calculate C.

The measured absorbances of ¹² CO ₂ and ¹³ CO ₂ naturally include the influence of mutual interference as described above. On the other hand, since the two absorbances that constitute the calibration surface also include such an influence of mutual interference, if the absorbance obtained by the measurement is illuminated on the calibration surface to calculate the concentration ratio, the influence of such mutual interference is obtained. Does not appear in the calculation result of the concentration ratio. That is, the concentration ratio can be obtained with high accuracy.

[0031] ¹³ C with indicators to the reagent (urea) before and after administration to the subject, the breath test device of the present embodiment, respectively measuring the concentration ratio [delta] ¹³ C for breath該被examiner, the difference Calculate (decrease rate) Δ ¹³ C. It is generally said that this value increases by 2.5 (permil) or more when infected with H. pylori. This makes it possible to determine whether or not the subject has H. pylori.

The isotope gas measuring apparatus to which the present invention can be applied is not limited to the above-described configuration. That is, it is only necessary to measure the absorbance of infrared light due to the absorption of ¹² CO ₂ and ¹³ CO ₂ , and the configuration of the measurement cell can be modified into various forms. Further, instead of using a mechanical chopper, a device that emits infrared light intermittently by blinking a light source may be used. Obviously, other changes and modifications can be made within the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a breath test apparatus which is an embodiment of an isotope gas measurement apparatus according to the present invention.

FIG. 2 shows, in a three-dimensional space, data obtained by measuring a standard gas in the breath test apparatus of the present embodiment.
Graph on which the calibration surface is based.

FIG. 3 is a flowchart illustrating a processing procedure of a calibration surface creation operation in the breath test apparatus according to the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Light source 11, 12 ... Chopper 13 ... Motor 14, 17 ... Measurement cell 15, 18 ... Interference filter 16, 19 ... Detector 20 ... Connection pipe 21 ... Gas introduction pipe 22 ... Flow-path switching part 23, 24 ... Valve 25 ... Exhaust pipe 26 ... Pump 27 ... Flow rate sensor 30 ... Calculation processing unit 31 ... Absorbance calculation unit 32 ... Concentration ratio calculation unit 33 ... Calibration surface memory 40 ... Control unit

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Junichi Kita 1 Nishinokyo Kuwabaracho, Nakagyo-ku, Kyoto F-term in Shimadzu Corporation (reference) 2G045 AA25 CB22 DB01 FA25 FB08 2G059 AA01 AA06 BB01 BB12 CC04 CC16 DD04 DD16 EE01 FF08 GG00 GG07 HH01 HH06 JJ03 JJ24 KK01 KK03 LL04 MM01 MM05 MM09 MM10 MM12 NN01 4B063 QA01 QA19 QQ03 QQ89 QR41 QX07

Claims (2)

[Claims] 1. A measuring cell through which a gas to be measured flows.
A light source for irradiating the measurement cell with infrared light;
A detector that receives infrared light transmitted through the
Carbonized¹²CO_TwoAnd its stable isotopes¹³CO_Twoincluding
The gas to be measured is introduced into the measurement cell,¹²CO_Twoas well as¹³C
O_TwoAbsorbance of infrared light having wavelengths corresponding to
In the isotope gas measuring device to be measured, a)¹²CO_TwoWhen¹³CO_TwoMultiple standard gases with known concentration ratios
Created based on the measurement results for¹²CO_TwoWhen
¹³CO_TwoConcentration ratio of¹²CO_TwoAbsorbance, and¹³CO_TwoSucking
A data representing a calibration plane in three-dimensional space with luminosity as a parameter
Storage means for storing data; b)¹²CO_TwoWhen¹³CO_TwoGas to be measured whose concentration ratio is unknown
Introduce into the measuring cell, ¹²CO_Twoas well as¹³CO_TwoTo each
Absorbance measurement to measure the absorbance of infrared light having a corresponding wavelength
C) data representing the calibration plane stored in the storage means.
By reference, obtained by the absorbance measurement means¹²CO_Two
as well as¹³CO_TwoCalculate the unknown concentration ratio from the absorbance of
An isotope gas measuring device comprising: a concentration ratio calculating unit. 2. A measuring cell through which a gas to be measured flows.
A light source for irradiating the measurement cell with infrared light;
A detector that receives infrared light transmitted through the
Carbonized¹²CO_TwoAnd its stable isotopes¹³CO_Twoincluding
The gas to be measured is introduced into the measurement cell,¹²CO_Twoas well as¹³C
O_TwoAbsorbance of infrared light having wavelengths corresponding to
Using an isotope gas measurement device to measure,¹²CO_TwoWhen¹³C
O_TwoThe concentration ratio of the gas to be measured whose concentration ratio is unknown
Measurement method for a)¹²CO_TwoWhen¹³CO_TwoOf several types with known concentration ratios
Introduce the reference gas into the measuring cell,¹²CO_Twoas well as¹³CO_TwoNiso
Measure the absorbance of infrared light having the corresponding wavelength,
Based on the measurement results¹²CO_TwoWhen¹³CO_TwoConcentration ratio of¹²
CO_TwoAbsorbance, and¹³CO_TwoThe absorbance of
A calibration plane in a three-dimensional space, and a calibration plane creation step for holding data representing the calibration plane.
B)¹²CO_TwoWhen¹³CO_TwoGas to be measured whose concentration ratio is unknown
Introduce into the measuring cell, ¹²CO_Twoas well as¹³CO_TwoTo each
Absorbance measurement to measure the absorbance of infrared light having a corresponding wavelength
C) by referring to data representing the calibration surface,
Obtained by means of absorbance measurement¹²CO_Twoas well as¹³CO_TwoSucking
A density ratio calculation step for calculating the unknown density ratio from the luminous intensity.
And a method for measuring an isotope gas.