JP2885687B2 - Isotope gas spectrometry - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The metabolic function of a living body can be measured by administering a drug containing an isotope to a living body and then measuring the change in the isotope concentration or the change in the concentration ratio. Body analysis has been used to diagnose diseases in the medical field. In addition to the fields of medicine, isotope analysis is used for studies of photosynthesis and metabolism of plants, and is used for tracing ecosystems in the field of geochemistry.

[0002] The present invention, by focusing on the difference in the light absorption characteristics of isotopes, but about the isotope gas spectroscopic measurement how to measure the concentration of the isotope gas.

[0003]

2. Description of the Related Art In general, it is known that bacteria other than stress include bacteria called Helicobacter pylori (HP) as a cause of gastric ulcer and gastritis. If HP is present in the patient's stomach, it is necessary to perform eradication treatment by administration of antibiotics or the like. Therefore, it is important to determine whether HP is present in the patient. HP is
It has strong urease activity and breaks down urea into carbon dioxide and ammonia.

[0004] On the other hand, carbon has a mass number of 12 and isotopes having a mass number of 13 and 14 in addition to a carbon atom having a mass number of 12. Among these, the isotope ¹³ C having a mass number of 13 has no radioactivity, Handling is easy because it exists stably. Therefore, after administering urea marked with the isotope ¹³ C to the living body, the concentration of ¹³ CO ₂ in the patient's breath, which is the final metabolite, specifically, the concentration ratio of ¹³ CO ₂ to ¹² CO ₂ is measured. If it can, the existence of the HP can be confirmed.

However, the concentration ratio of ¹³ CO ₂ to ¹² CO ₂ is as large as 1: 100 in nature, and it is difficult to accurately measure the concentration ratio in a patient's breath. Conventionally,
^As a method for determining the concentration ratio between ¹³ CO ₂ and ¹² CO ₂ , a method using infrared spectroscopy is known (Japanese Patent Publication No. Sho 61-42).
No. 219, JP-B-61-42220).

[0006] The method described in JP-B-61-42220 is
Two long and short cells were prepared, and the length of the cell was set so that the absorption of ¹³ CO ₂ in one cell was equal to the absorption of ¹² CO _{2 in} one cell, and the cells were transmitted through the two cells. In this method, light is guided to both cells, and the light intensity at a wavelength that achieves the maximum sensitivity is measured. According to this method, the light absorption ratio at the concentration ratio in the natural world can be set to 1. If the concentration ratio deviates from this, the light absorption ratio deviates by the amount of the deviation. You can see the change in the ratio.

[0007]

SUMMARY OF THE INVENTION The concentration of CO ₂ , especially ¹³
Since the concentration of CO ₂ is very low, a sensitive measurement must be made. However, if the sensitivity of the measurement is increased, if there are fluctuations in the constants of the measurement system, such as fluctuations in the intensity of the light source, fluctuations in the temperature of the gas itself, fluctuations in the temperature of the cell into which the gas is introduced, and fluctuations in the sensitivity of the photodetector, The measured light intensity responds sensitively,
There is a problem that an error occurs in the measured value due to factors other than the actual gas to be measured.

In order to solve the above problem, it is conceivable to start the measurement after sufficient time until the measurement system is settled down. However, in this case, the processing capacity is reduced, and a large amount of sample can be obtained in a short time. Users will not be able to respond to user requests for measurement. Further, in the measurement, for one breath, by measuring the absorbance of ¹² CO _2, ¹² CO
Using a calibration curve for ₂ to calculate the ¹² CO ₂ concentration, ¹³ CO ₂
Measure the absorbance of ¹³ C using the calibration curve for ¹³ CO ₂
Calculate the O ₂ concentration. Similar measurements are made for other types of exhalation.

At this time, if the CO ₂ concentration is substantially the same for the two types of exhaled air, the range in which the calibration curve of ¹² CO _{2 or} the calibration curve of ¹³ CO ₂ is used can be narrowed. Therefore,
The measurement accuracy can be improved by limiting the range in which the calibration curve is used.

According to the present invention, when a gas to be measured containing a plurality of component gases is introduced into a cell and spectrometry is performed, the concentration of the component gas can be accurately measured by limiting the range in which a calibration curve is used. An object of the present invention is to realize an isotope gas spectrometry method that can be performed.

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

In order to achieve the above object,
Because of Claim 1 proportional gas spectroscopic measurement according methods, two types of measurement gas collected from one analyte, CO ₂ in the CO ₂ concentration and the other gas to be measured of one of the gas to be measured
Is higher than the concentration, the one of the CO ₂ concentration of the gas to be measured by diluting one of the measurement gas to be equal to the CO ₂ concentration of the other gas to be measured, the concentration ratio ¹³ C of each gas to be measured
The O ^_2/12 CO ₂ is a method of measuring.

According to this method, it is possible to measure each of the two types of exhaled air under the condition that the CO ₂ concentration is equal, so that the range of the calibration curve to be used can be limited.
As a result, measurement accuracy can be improved. The method according to claim 2 or 3 , wherein a single cell is filled with the first type of gas to be measured, the light quantity is measured, and after discharging, the second gas is measured.
Based on the assumption that the measured amount of light meets the kind of the gas to be measured, shows a specific procedure for the isotope gas spectroscopic measurement method according to claim 1, wherein.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, after a urea diagnostic agent marked with isotope ¹³ C is administered to humans, ¹³ CO _{2 in} exhaled breath
When spectroscopically measuring the concentration of the embodiment of the present invention,
This will be described in detail with reference to the accompanying drawings. I. Breath test First, the breath of the patient before administration of the urea diagnostic agent is collected in a breath bag. The capacity of the exhalation bag may be about 250 ml. Thereafter, a urea diagnostic agent was orally administered and 10-1
Five minutes later, the breath is collected in a breath bag in the same manner as before administration.

Before administration, the exhalation bags after administration are respectively set in predetermined nozzles of the isotope gas spectrometer, and the following automatic control is performed. II. FIG. 1 is a block diagram showing the overall configuration of an isotope gas spectrometer. The exhalation bag that collects exhaled air after administration (hereinafter referred to as “sample gas”) and the exhalation bag that collects exhaled air before administration (hereinafter referred to as “base gas”) are set in nozzles N ₁ and N ₂ , respectively. The nozzle N ₁ is connected to a three-way valve V ₁ through a transparent resin pipe (hereinafter simply referred to as “pipe”), and the nozzle N ₂ is connected to a three-way valve V ₂ through a pipe.

On the other hand, a reference gas (any gas having no absorption in the wavelength range to be measured, for example, nitrogen gas) is supplied from a gas cylinder. Reference gas divided into two-way, one enters a reference cell 11c through the flow meter M _1, the other leads to the three-way valve V ₃ through the flow meter M _2. The reference gas that has entered the reference cell 11c exits the reference cell 11c and is discharged as it is.

[0021] While the divided from way valve V ₃ leads to the three-way valve V _1, and the other thereof is connected to the first sample cell 11a for measuring the absorption of ¹² CO _2.
Also, while the divided from way valve V ₂ are two-way leads to the first sample cell 11a through a valve V _4, the other is connected to the three-way valve V _1. Furthermore, between the three-way Harrub V ₃ and the first sample cell 11a, is interposed or gas injector 21 for quantitatively injecting (volume 60 cc) the sample gas or the base gas. The gas injector 21 is shaped like a syringe having a piston and a cylinder. The piston is driven by a motor (not shown), a feed screw connected to the motor, and a nut fixed to the piston. Done by

As shown in FIG. 1, the cell chamber 11 contains ¹² CO 2.
Short first sample cell 11 for measuring the absorption of ₂
a, comprising a long second sample cell 11b for measuring the absorption of ¹³ CO ₂ and a reference cell 11c for flowing a reference gas, the first sample cell 11a and the second sample cell 11b are in communication with each other, Cell 1
The gas led to the first sample cell 11a
b and is exhausted. The reference gas is guided to the reference cell 11c and exhausted. The length of the first sample cell 11a is specifically 13 mm, and the length of the second sample cell 11a is 11 mm.
The length of b is specifically 250 mm, and the length of the reference cell 11c is specifically 236 mm.

Reference symbol L indicates an infrared light source device. The infrared light source device L has two waveguides 23 for irradiating infrared light.
a and 23b. The method of generating infrared rays may be any method, for example, a ceramic heater (surface temperature 45 ° C).
0 ° C.) can be used. In addition, a rotating chopper 22 that cuts off and passes infrared rays at a constant cycle is provided. Of the infrared rays emitted from the infrared light source device L,
An optical path formed by an object passing through the first sample cell 11a and the reference cell 11c is referred to as a “first optical path”,
The optical path formed by the object passing through the sample cell 11b is referred to as “second
(See FIG. 2).

The symbol D detects infrared light passing through the cell.
FIG. The infrared detector D is
A first wavelength filter 24a placed in a first optical path and a first wavelength filter 24a;
Detecting element 25a, the second wavelength filter placed in the second optical path.
It has a filter 24b and a second detection element 25b. No.
One wavelength filter 24a is¹²CO_TwoMeasuring absorption
For this reason, it passes infrared light with a wavelength of about 4280 nm (bandwidth about
20 nm), the second wavelength filter 24b ¹³CO_Twoof
Pass infrared light at a wavelength of about 4412 nm to measure absorption.
(Bandwidth about 50 nm). First
Detection element 25a and second detection element 25b detect infrared rays.
Any element can be used as long as the element emits, for example, PbSe.
Such a semiconductor infrared sensor is used.

The first wavelength filter 24a and the first detection element 25a are contained in a package 26a filled with an inert gas such as Ar, and the second wavelength filter 24a.
b, the second detection element 25b is also contained in a package 26b filled with an inert gas. The entire infrared detecting device D is maintained at a constant temperature (25 ° C.) by a heater and a Peltier element, and the parts of the detecting elements in the packages 26a and 26b are maintained at 0 ° C. by a Peltier element.

FIG. 2 is a sectional view showing the detailed structure of the cell chamber 11. As shown in FIG. The cell chamber 11 itself is made of stainless steel, and is vertically and horizontally sandwiched between metal plates (for example, a brass plate) 12, and is sealed with a heat insulating material 14 via heaters 13 installed vertically and horizontally. The cell chamber 11 is divided into two stages, one of which has a first sample cell 11a and a reference cell 11c, and the other of which has a second sample cell 11b.

A first optical path passes in series through the first sample cell 11a and the reference cell 11c, and a second optical path passes through the second sample cell 11b. Symbol 15, 1
Reference numerals 6 and 17 denote sapphire transmission windows that transmit infrared rays. The cell chamber 11 is heated at a constant temperature (4
(0 ° C.). IIIa. Measurement procedure 1 Measurement is performed in the order of reference gas measurement → base gas measurement → reference gas measurement → sample gas measurement → reference gas measurement → ‥‥. However, in addition to this procedure, the procedure of base gas measurement → reference gas measurement → base gas measurement, sample gas measurement → reference gas measurement → sample gas measurement, and ‥‥, but the same base gas and sample gas are measured twice Efficiency must be reduced. Hereinafter, the former efficient procedure will be described.

During the measurement, a reference gas is constantly flowing in the reference cell 11c. IIIa-1. Reference Measurement As shown in FIG. 3, a clean reference gas is flowed at 200 ml / min for about 15 seconds into the gas flow path and the cell chamber 11 of the isotope gas spectrometer to clean the gas flow path and the cell chamber 11. .

Next, as shown in FIG. 4, a reference gas is supplied by changing the gas flow path, and the gas flow path and the cell chamber 11 are cleaned. After about 30 seconds, each detection element 25
The light quantity is measured by a and 25b. The reason for performing the reference measurement in this way is to calculate the absorbance. In this manner, the amount of light obtained by the first detection element 25a is ¹² R ₁ , and the amount of light obtained by the second detection element 25b is
¹³ written as R _1. IIIa-2. Base Gas Measurement Next, the base gas is sucked from the expiration bag by the gas injector 21 so that the reference gas does not flow through the first sample cell 11a and the second sample cell 11b (FIG. 5).
reference).

After the base gas has been sucked in, the base gas is mechanically pushed out at a constant flow rate using a gas injector 21 as shown in FIG. During this time, each detection element 25
The light quantity is measured by a and 25b. In this way,
The amount of light obtained by the first detection element 25a ¹² B, write the resulting quantity and the ¹³ B in the second detection element 25b. IIIa-3. Reference measurement The gas flow path and the cell are washed again, and the light quantity of the reference gas is measured again (see FIGS. 3 and 4).

In this manner, the light amount ¹² R ₂ obtained by the first detection element 25 a and the light amount ¹³ R ₂ obtained by the second detection element 25 _b are written. IIIa-4. Sample gas measurement The sample gas is sucked from the expiration bag by the gas injector 21 so that the reference gas does not flow through the first sample cell 11a and the second sample cell 11b (see FIG. 7).

After the sample gas has been sucked, the sample gas is mechanically pushed out at a constant speed using a gas injector 21 as shown in FIG. During this time, each detection element 2
The light quantity is measured by 5a and 25b. In this manner, the amount of light obtained by the first detection element 25a ¹² S, second
The amount of light obtained by the detection element 25b are the ¹³ S. IIIa-5. Reference measurement The gas flow path and the cell are washed again, and the light quantity of the reference gas is measured again (see FIGS. 3 and 4).

[0033] Thus, the first detection element 25a in the resulting amount of ¹² R _3, Write obtained amount and the ¹³ R ₃ in the second detection element 25b. IIIb. In the measurement procedure 2 the measurement procedure 1, it was not able to match the CO ₂ concentration in the CO ₂ concentration and the sample gas based gas.

However, if the CO ₂ concentration is the same for the base gas and the sample gas, a calibration curve of ¹² CO ₂ and ¹³ C
The range in which the O ₂ calibration curve is used can be narrowed. Therefore, measurement accuracy can be improved by limiting the range in which the calibration curve is used. In the measurement procedure 2, in order to substantially coincide with the CO ₂ concentration in the CO ₂ concentration and the sample gas based gas, the first preliminary measurement, the CO ₂ concentration of the base gas, the CO ₂ concentration of the sample gas is measured, respectively, in this measurement, base gas until the CO ₂ concentration of the base gas that has been pre-measured is higher than the CO ₂ concentration of the pre-measured sample gas, the CO ₂ concentration of the base gas is equal to the CO ₂ concentration of the sample gas After dilution, the concentration of the base gas is measured, and then the concentration of the sample gas is measured.

In this measurement, if the CO ₂ concentration of the base gas measured in advance is measured, the C ₂ concentration of the sample gas measured in advance is measured.
If it is lower than the O ₂ concentration, the concentration of the base gas is measured as it is, and the CO ₂ concentration of the sample gas is
After diluting the sample gas until the concentration becomes equal to ₂ , the CO ₂ concentration of the sample gas is measured. The measurement is performed in the following order: base gas preliminary measurement → sample gas preliminary measurement → reference gas measurement → base gas measurement → reference gas measurement → sample gas measurement → reference gas measurement → ‥‥. IIIb-1. Base gas preliminary measurement In the gas channel and cell chamber 11 of the isotope gas spectrometer,
Gas flow path and cell chamber 1 by flowing a clean reference gas
In addition to the washing of step 1, the reference light quantity is measured.

Next, the base gas is sucked from the expiration bag by the gas injector 21, and the base gas is mechanically pushed out at a constant flow rate using the gas injector 21. During this time, the detection element 2
In step 5a, the light quantity of the base gas is measured, and the CO ₂ concentration is determined from the absorbance using a calibration curve. IIIb-2. Preliminary measurement of sample gas In the gas channel and cell chamber 11 of the isotope gas spectrometer,
Gas flow path and cell chamber 1 by flowing a clean reference gas
In addition to the washing of step 1, the reference light quantity is measured.

Next, the sample gas is sucked from the expiration bag by the gas injector 21, and the sample gas is mechanically pushed out at a constant speed using the gas injector 21. During this time, the light intensity of the sample gas is measured by the detection element 25a, and the CO ₂ concentration is determined using the calibration curve based on the absorbance. IIIb-3. Reference Measurement Next, the reference gas is flowed while changing the gas flow path, and the gas flow path and the cell chamber 11 are cleaned. After a lapse of about 30 seconds, the light quantity is measured by the respective detection elements 25a and 25b.

The amount of light obtained by the first detecting element 25a in this manner is written as ¹² R ₁ , and the amount of light obtained in the second detecting element 25b is written as ¹³ R ₁ . IIIb-4. Base gas measurement In “IIIb-1. Preliminary base gas measurement”, the CO ₂ concentration of the base gas obtained by the first detection element 25a and “II
Ib-2. Comparing the CO ₂ concentration of the sample gas obtained by the first detection element 25a in a sample gas preliminary measurement ", when CO ₂ concentration of the base gas is darker than the CO ₂ concentration of the sample gas, in the gas injector 21 And base gas C
After diluting the base gas with the reference gas until the O ₂ concentration becomes equal to the CO ₂ concentration of the sample gas,
Measure the light quantity of the base gas.

With such dilution, the CO ₂ concentration can be made substantially the same for the two types of exhaled air, so that the range in which the calibration curve of ¹² CO _{2 or} the calibration curve of ¹³ CO ₂ is used can be narrowed. In measuring procedure 2 of this embodiment, there are means of CO ₂ concentration at the substantially same for the two types of breath, always constant CO ₂ concentration as described in KOKOKU 4-12414 Patent Publication It should be noted that the procedure to keep the data is not necessarily adopted. This is because if the CO ₂ concentration in the base gas and the sample gas can be made the same, the purpose of narrowing the range in which the calibration curve is used can be sufficiently achieved. According to the actual measurement, the CO ₂ concentration of the base gas and the sample gas varies from 1% to 5%, and it is very troublesome to keep the CO ₂ concentration constant at all times.

[0040] If the CO ₂ concentration of the base gas is less than the CO ₂ concentration of the sample gas is directly measuring the base gas without dilution base gas. The measurement is performed by mechanically extruding the base gas at a constant flow rate by using the gas injector 21 and during this time, by the respective detection elements 25a and 25b. Thus, the first detection element 25a ¹² B and the resulting amount of light, the amount of light obtained by the second detection element 25b are the ¹³ B. IIIb-5. Reference measurement The gas flow path and the cell are washed again, and the light quantity of the reference gas is measured.

The amount of light ¹² R ₂ obtained by the first detection element 25 a and the amount of light ¹³ R ₂ obtained by the second detection element 25 _b are written as described above. IIIb-6. Sample gas measurement When the base gas is diluted in “IIIb-4. Base gas measurement”, after inhaling the sample gas from the expiration bag,
The sample gas is mechanically extruded at a constant flow rate using the gas injector 21, and during this time, the respective detection elements 25a, 25
5b, the light quantity is measured.

[0042] If the undiluted base gas "IIIb-4. Base gas measurement", until the ratio and the CO ₂ concentration of the CO ₂ concentration and the base gas of the sample gas are equal in the gas injector 21 After diluting the sample gas with the reference gas, the light intensity of the sample gas is measured by the respective detection elements 25a and 25b. In this way,
The amount of light obtained by the first detection element 25a ¹² S, write the resulting quantity and the ¹³ S in the second detection element 25b. IIIb-7. Reference gas measurement The gas flow path and the cell are washed again, and the light quantity of the reference gas is measured.

As described above, the first detecting element 25a
The amount of light obtained¹²R_Three, Obtained by the second detection element 25b.
Light intensity¹³R_ThreeWrite IV. Data processing IV-1. Calculation of absorbance of base gas First, the reference obtained in measurement procedure 1 or 2 was used.
Light transmitted by the reference gas ¹²R₁,¹³R₁, Base gas permeability
Excessive light¹²B,¹³B, the amount of transmitted reference gas
¹²R_Two,¹³R_TwoUsing in the base gas¹²CO_Two
Absorbance of¹²Abs (B) and¹³CO_TwoAbsorbance of¹³Abs (B) and
Ask for.

[0044] Here, ¹² CO ₂ absorbance ¹² Abs (B) is, ¹² Abs (B) = - calculated in log _{^{[2 12 B / (12 R 1}} + 12 R 2) ], ¹³ CO ₂ absorbance ¹³ determined by log _{^{[2 13 B / (13 R 1}} + 13 R 2) ] ^{- abs (B), 13 abs} (B) =.

As described above, when calculating the absorbance, the average value (R ₁ + R) of the light amounts of the reference measurements performed before and after
₂ ) Take the value of 2 and calculate the absorbance using the average value and the amount of light obtained from the base gas measurement. Therefore, offset the effect of drift (time change affects the measurement). Can be. Therefore, measurement can be started immediately without having to wait for complete thermal equilibrium (usually several hours) when starting up the device.

Note that IIIa. Base as mentioned at the beginning of
Gas measurement → Reference gas measurement → Base gas measurement →
Sample gas measurement → Reference gas measurement → Sample gas
If the procedure of measurement is adopted, the base gas
¹²CO_Two Absorbance of¹²Abs (B) is¹² Abs (B) =-log [(¹²B₁+¹²B_Two ) / 2¹²R]¹³CO_Two Absorbance of¹³Abs (B) is¹³ Abs (B) =-log [(¹³B₁ +¹³B_Two) / 2¹³R]. Here, R is the transmission of the reference gas.
Light intensity, B₁, B_TwoIs the reference gas measurement
This is the transmitted light amount of the front and rear base gases. IV-2. Calculation of absorbance of sample gas Next, the reference obtained in measurement procedure 1 or 2
Light transmitted by the reference gas ¹²R_Two,¹³R_TwoOf the sample gas
Transmitted light¹²S,¹³S, amount of transmitted reference gas¹²R
_Three,¹³R_Three Using in the sample gas¹²CO_Two of
Absorbance¹²Abs (S) and¹³CO_Two Absorbance of¹³Abs (S) and
Ask.

[0047] Here, ¹² CO ₂ absorbance ¹² Abs (S) is, ¹² Abs (S) = - calculated in log _{^{[2 12 S / (12 R 2}} + 12 R 3) ], ¹³ CO ₂ absorbance ¹³ abs (S) is, ¹³ abs (S) = - is determined by the log _{^{[2 13 S (13 R 2 +}} 13 R 3) ].

As described above, when calculating the absorbance, the average value of the light amounts of the reference measurements performed before and after is calculated, and the absorbance is calculated using the average value and the light amounts obtained by the sample gas measurement. Therefore, the influence of the drift can be offset. Note that IIIa. Base gas measurement → reference gas measurement → base gas measurement,
If the procedure of sample gas measurement → reference gas measurement → sample gas measurement, etc. is adopted, the absorbance ¹² Abs (S) of ¹² CO ₂ of the sample gas is ¹² Abs (S) = − log [( ¹² S _{1 ^{+ 12 S 2) / 2 12}} R ] at sought, ¹³ CO ₂ absorbance ¹³ Abs (S) is, ¹³ Abs (S) = - in log _{^{[(13 S 1 + 13 S 2}} ) / 2 13 R ! Desired. Here, R is the transmitted light amount of the reference gas, and S ₁ and S ₂ are the transmitted light amounts of the sample gas before and after the measurement of the reference gas, respectively. IV-3. Calculation of Concentration The concentration of ¹² CO _{2 and} the concentration of ¹³ CO ₂ are determined using a calibration curve.

A calibration curve is prepared using a gas to be measured having a known ¹² CO ₂ concentration and a gas to be measured having a known ¹³ CO ₂ concentration. In order to obtain a calibration curve, the absorbance of ¹³ CO ₂ is measured by changing the concentration of ¹² CO _{2 in} the range of about 0% to 6%. The horizontal axis is ¹² CO ₂ concentration, and the vertical axis is ¹² C
Take the O ₂ absorbance, plot and determine the curve using least squares. Since the curve approximated by the quadratic equation has a relatively small error curve, the calibration curve approximated by the quadratic equation is employed in the present embodiment.

The concentration of ¹³ CO _{2 is set} to 0.00% to 0.0%.
The absorbance of ¹³ CO ₂ is measured while changing it in the range of about 7%. The horizontal axis is taken as ¹³ CO ₂ concentration, the vertical axis is taken as ¹³ CO ₂ absorbance, plotted, and the curve is determined using the least squares method. Since the curve approximated by the quadratic equation has a relatively small error curve, the calibration curve approximated by the quadratic equation is employed in the present embodiment.

Strictly speaking, the gas containing ¹² CO ₂ and the gas containing ¹³ CO ₂ are measured independently, and the gas containing ¹² CO ₂ and ¹³ CO ₂ is mixed. , The absorbance of ¹³ CO ₂ will be different. This is because the wavelength filter used has a bandwidth and the absorption spectrum of ¹² CO _{2 and} the absorption spectrum of ¹³ CO ₂ partially overlap. In this measurement,
^Since a gas in which ¹² CO ₂ and ¹³ CO ₂ are mixed is to be measured, it is necessary to correct the overlap when determining a calibration curve. In this measurement, a calibration curve in which the overlap of the absorption spectra is partially corrected is actually used.

The base gas calculated using the calibration curve
In¹²CO_TwoThe concentration of¹²Conc (B) for base gas
Put¹³CO_TwoThe concentration of¹³Conc (B), sample gas
Kick ¹²CO_TwoThe concentration of¹²Conc (S) in sample gas
To¹³CO_TwoThe concentration of¹³Write Conc (S). IV-4. Calculation of concentration ratio¹³ CO_Two When¹²CO_Two The concentration ratio is determined. For base gas
Concentration ratio¹³ Conc (B) /¹²Conc (B) The concentration ratio in the sample gas is¹³ Conc (S) /¹²Required by Conc (S).

The concentration ratio was ¹³ Conc (B) / ¹² Conc (B)
^{+ 13 Conc (B), 13} Conc (S) / 12 Conc (S) + 13 may be defined as Conc (S). ^{This is because} the concentration of ¹² CO ₂ is much higher than the concentration of ¹³ CO ₂ , so that both have substantially the same value. IV-5. ¹³ C ¹³ C variation in comparing the variation of the determined sample gas and the base gas is obtained by the following expression.

Δ ¹³ C = [concentration ratio of sample gas−concentration ratio of base gas] × 10 ³ / [concentration ratio of base gas]
(Unit: Per mill (per thousand))

[0055]

EXAMPLE The same gas to be measured containing carbon dioxide (the same concentration of CO _2, of course) was used to measure the concentration of ¹² CO ₂ several times by this isotope gas spectrometer. Start-up 1
After a lapse of time, the sample gas measurement was performed 10 times in the order of reference gas measurement → sample gas measurement → reference gas measurement → sample gas measurement → reference gas measurement → ‥‥. The method A of the present invention for determining the absorbance of the sample gas based on the average value of the measured values of the reference gas before and after the measurement of the sample gas, and the method of determining the absorbance of the sample gas based on the measured values of the reference gas only before the measurement of the sample gas B and the respective densities were determined.

Table 1 shows the results of calculating the concentration by the method A.
Shown in In Table 1, the concentration measured at the first measurement is set to 1, and the concentrations obtained at the second measurement and thereafter are normalized. In the method A, the standard deviation of the calculated density data was 0.0009.

[0057]

[Table 1]

Table 2 shows the results of calculating the concentration by the method B.
Shown in Also in Table 2, the concentration measured at the first measurement is set to 1, and the concentrations obtained at the second measurement and thereafter are normalized. In method B, the standard deviation of the concentration data was 0.0013.

[0059]

[Table 2]

From the above, the method of the present invention for determining the absorbance from the light quantity obtained by filling the sample gas and the average value of the light quantity obtained by filling the reference gas before and after the sample gas is further improved. It was found that density data with little variation could be obtained.

[0061]

[0062]

[0063]

Effects of the Invention According to the present invention according to claim 1, wherein, two because it about the same concentration of CO ₂ for the gas to be measured, ¹² CO ₂ calibration curves and the ¹³ CO ₂ calibration curves Can be used in a narrower range. As the calibration curve has a narrower range, a higher accuracy can be obtained. Therefore, by limiting the range in which the calibration curve is used, measurement accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an isotope gas spectrometer.

FIG. 2 is a sectional view showing the structure of a cell chamber 11;

FIG. 3 is a diagram showing a gas flow path when a clean reference gas is flown through a gas flow path and a cell chamber of the isotope gas spectrometer for cleaning.

FIG. 4 is a diagram showing a gas flow path when a clean reference gas is flown through a gas flow path and a cell chamber of the isotope gas spectrometer to perform cleaning and reference measurement.

FIG. 5 is a diagram illustrating a first sample cell 11a having a reference gas;
It is a figure which shows the state in which the base gas is inhaled by the gas injector 21 from the expiration bag so that it may not flow through the 2nd sample cell 11b.

FIG. 6 is a diagram illustrating a gas flow path when a light amount is measured by each of the detection elements 25a and 25b while the base gas is mechanically pushed out at a constant speed by using the gas injector 21 after sucking the base gas. FIG.

FIG. 7 shows a first sample cell 11a having a reference gas;
FIG. 9 is a diagram showing a state in which a sample gas is being sucked in from a breath bag by a gas injector 21 so as not to flow through a second sample cell 11b.

FIG. 8 shows a gas injector 21 after aspirating a sample gas.
Mechanically extrude the sample gas at a constant speed using
FIG. 4 is a diagram showing gas flow paths when measuring the amount of light by the detection elements 25a and 25b during this time.

[Explanation of symbols]

D Infrared detector L Infrared light source device M ₁ , M ₂ Flow meter N ₁ , N ₂ nozzle V ₁ -V ₄ valve 11a First sample cell 11b Second sample cell 11c Reference cell 21 Gas injector 24a First wavelength filter 25a first detection element 24b second wavelength filter 25b second detection element

Continued on the front page (72) Inventor Eiji Ikegami 112 Tonasaka, Minaguchi-machi, Koka-gun, Shiga Pref. JP, A) JP-A-55-112546 (JP, A) JP-A-53-42890 (JP, A) JP-A-4-42041 (JP, A) JP-B-4-12414 (JP, B2) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) G01N 21/00-21/01 G01N 21/17-21/61

Claims (3)

(57) [Claims] 1. Carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO ₂
Using a calibration curve created by introducing a gas to be measured containing component gas into the cell, determining the absorbance of transmitted light having a wavelength suitable for each component gas, and measuring a gas containing a component gas having a known concentration. In the isotope gas spectrometry for measuring the concentration of each component gas, the CO ₂ concentration of one measured gas is reduced by the CO ₂ concentration of the other measured gas for two types of measured gases collected from one sample. is higher than ₂ concentration, the one of the CO ₂ concentration in the measurement gas is diluted one of the measurement gas to be equal to the CO ₂ concentration of the other gas to be measured, the concentration ratio ¹³ CO of each gas to be measured ^_2/12 CO ₂ isotope gas spectroscopic measurement method for measuring. 2. Carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO ₂
Using a calibration curve created by introducing a gas to be measured containing component gas into the cell, determining the absorbance of transmitted light having a wavelength suitable for each component gas, and measuring a gas containing a component gas having a known concentration. In the isotope gas spectrometry method for measuring the concentration of each component gas, in the preliminary measurement: (a) For two kinds of measured gases collected from one sample, the CO _{2 of} the first type of measured gas and concentration, the CO ₂ concentration of the second type of gas to be measured were measured, in the measurement, (b) a second type of the measurement is measured CO ₂ concentration of the first type of the measurement gas was measured If the CO ₂ concentration of the gas is higher than the CO ₂ concentration of the gas, the gas of the first type is diluted until the CO ₂ concentration of the gas of the first type becomes equal to the CO ₂ concentration of the gas to be measured of the second type. the concentration ratio of the first kind of gas to be measured ¹³ CO ^_2/12 The CO ₂ is measured, (c) the concentration ratio of the two kinds of the measurement gas ¹³ CO ^_2/12 CO ₂
Isotope gas spectrometry method for measuring gas. 3. Carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO ₂
Using a calibration curve created by introducing a gas to be measured containing component gas into the cell, determining the absorbance of transmitted light having a wavelength suitable for each component gas, and measuring a gas containing a component gas having a known concentration. In the isotope gas spectrometry method for measuring the concentration of each component gas, in the preliminary measurement: (a) For two kinds of measured gases collected from one sample, the CO _{2 of} the first type of measured gas and concentration, the CO ₂ concentration of the second type of gas to be measured were measured, in the measurement, (b) a second type of the measurement is measured CO ₂ concentration of the first type of the measurement gas was measured is lower than the CO ₂ concentration of the gas, the concentration ratio of the first kind of gas to be measured ¹³ CO ^_2/12 CO
₂ as it is, and (c) diluting the second type of gas to be measured until the CO ₂ concentration of the second type of gas to be measured becomes equal to the CO ₂ concentration of the first type of gas to be measured. Concentration ratio of the kind of gas to be measured ¹³
CO _^2/12 CO ₂ isotope gas spectroscopic measurement method for measuring.