JPH09105714A - Isotope gas spectrophotometry and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance measurement precision of concentration ratio between component gases by correcting the concentration ratio according to the concentrations of the component gases by using a correction curve. SOLUTION: As to a gas to be measured, which consists of component gases with known concentrations and a known concentration ratio, absorbances corresponding to the wavelengths of the component gases are found. Then, using a working curve, concentrations and concentration ratio of the component gases are found. When the found concentrations and the found concentration ratio of the component gases are plotted, a correction curve is formed. Using the formed correction curve, the concentration ratio of the component gases is corrected according to the concentrations of the component gases. According to the concentration ratio correction, a fluctuation phenomenon in the concentration ratio of the component gases is corrected in compliance with a difference between the concentrations of the component gases, so that measurement precision of the concentration ratio of the component gases can be improved.

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.

The present invention relates to an isotope gas spectroscopic measurement method and a measuring apparatus for measuring the concentration of isotope gas, paying attention to the difference in isotope light absorption characteristics.

[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 the urea marked with the isotope ¹³ C was administered to the living body, the concentration of ¹³ CO _{2 in} the exhaled breath of the patient, which is the final metabolite, specifically, the concentration ratio of ¹³ CO ₂ and ¹³ CO ₂ was measured. If it is possible, the existence of HP can be confirmed.

However, the concentration ratio of ¹³ CO ₂ to ¹³ CO ₂ is as large as 1: 100 in the natural world, and therefore it is difficult to measure the concentration ratio in the exhaled air of a patient with high accuracy. 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]

However, even if an attempt is made to obtain the concentration ratio by using the method described in the above-mentioned publication, there are the following problems. To find the ¹² CO ₂ concentrations and the ¹³ CO ₂ concentration, a gas of known ¹² CO ₂ concentration, using a gas of known ¹² CO ₂ concentration shall prepare a calibration curve, respectively.

[0008]¹²CO_TwoTo create a concentration calibration curve,¹²
CO_TwoTry changing the concentration several times, ¹²CO_TwoThe absorbance of
Measure and set the horizontal axis¹²CO_TwoFor concentration, the vertical axis is¹²CO_TwoSucking
Plot the magnitude, determine the curve using least squares
It is usual to specify. Also,¹³CO_TwoConcentration calibration curve
The creation is done in the same way. However, using infrared spectroscopy,
When measuring, the relationship between concentration and absorbance is that of Lambert-Beer
Create a calibration curve assuming that the law is followed, but Lambert-Be
er's law itself is an approximate expression, and in practice Lambert-Beer's
Sometimes you don't follow the rules. Therefore, the calibration curve
The calibration curve works well for the limited data points created
It may not fit.

FIG. 9 shows the concentration ratio (¹³CO_Twoconcentration/¹²CO_Two
Concentration) is constant (1.077%), ¹²CO_TwoDifferent concentration
It is created by measuring the absorbance of each gas to be measured.
Using the calibration curve¹²CO_TwoCalculated concentration and created calibration
With lines¹³CO_TwoFind the concentrations and calculate the ratio of those concentrations.
It is the graph that I put. According to the graph,¹²CO_TwoDark
If the degree is different, the measured concentration ratio is the actual concentration ratio (1.
(077%) is rippling.

Although the cause of this deviation is not well known, the reflectance, the refractive index, the stray light, etc. change depending on the concentration, and the result overlaps with the error characteristic of the least squares method used when the calibration curve is obtained. Is considered to be. If the concentration of the component gas is calculated without correcting the characteristic of this deviation, it is expected that a large error will occur.

Therefore, the present invention solves the above-mentioned technical problems and introduces a gas to be measured containing a plurality of component gases to a cell,
An object of the present invention is to provide an isotope gas spectroscopic measurement method and a measurement device capable of accurately measuring the concentration ratio of component gases when performing spectroscopic measurement.

[0012]

The method of spectroscopic measurement of isotope gas according to the present invention comprises a first step of introducing a gas to be measured into a cell and obtaining an absorbance corresponding to the wavelength of each component gas, the component gas having a known concentration. The second step of obtaining the concentration and concentration ratio of the component gas, and the measured gas of which the concentration and concentration ratio of the component gas are known, using a calibration curve created by measuring the measurement gas containing A third step of correcting the concentration ratio of the component gas according to the concentration of the component gas by using the correction line created by the above is included.

According to the above construction, in comparison with the conventional method, in the third step, using the correction line created by measuring the measured gas whose component gas concentration and concentration ratio are known, A method of correcting the concentration ratio of the component gas according to the concentration of the component gas is added. By this correction of the concentration ratio, the concentration ratio of the component gas should originally be constant,
It is possible to enhance the measurement accuracy of the concentration ratio of the component gas by correcting the phenomenon that has been conventionally observed that the concentration ratio of the component gas varies depending on the difference in the concentration of the component gas.

The correction line in the third step is, specifically, the absorbance corresponding to the wavelength of the component gas is obtained for the gas to be measured whose concentration and concentration ratio of the component gas are known, and the calibration curve is used. It is obtained by obtaining the concentration and concentration ratio of the component gas, and plotting the obtained concentration and concentration ratio of the component gas. The correction method in the third step is the method for the measured gas in the second step. The concentration ratio correction value of the component gas is obtained by applying the obtained concentration of the component gas to the correction line, and the concentration ratio of the measured gas obtained in the second step is the concentration of the component gas obtained from the correction line. It is performed by dividing by the ratio correction value (claim 2).

In the method of claim 2, the obtained relationship between the concentration of the component gas and the concentration ratio can be approximated by a quartic curve (claim 3). This is because it is empirically known that the graph of the shift as shown in FIG. 9 can be approximated by a quartic curve. Multiple component gases are carbon dioxide ¹² CO
₂ and carbon dioxide ¹³ CO ₂ (claim 4).

Further, the isotope gas spectroscopic measurement apparatus of the present invention is a measurement apparatus for carrying out the above isotope gas spectroscopic measurement method of the present invention, and is introduced into a cell as a means for realizing a data processing function. Was measured for the measured gas,
Absorbance calculating means for obtaining the absorbance based on the amount of light corresponding to the wavelength suitable for each component gas, and using the calibration curve created by measuring the measured gas containing the component gas of known concentration, the component Concentration calculating means for determining the concentration and concentration ratio of the gas, and the component gas determined by the concentration calculating means by using the correction line created by measuring the measured gas whose concentration and concentration ratio of the component gas are known And a concentration ratio correction unit that corrects the concentration ratio of the component gas obtained by the concentration calculation unit according to the concentration (5).

[0017]

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
An embodiment of the present invention for spectroscopically measuring the concentration of
A detailed description will be given 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 volume of the exhalation bag may be about 250 ml. Thereafter, a urea diagnostic agent was orally administered and 10-1
After 5 minutes, exhaled air is collected in an exhaled bag in the same manner as before administration.

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

On the other hand, a reference gas (any gas having no absorption in the wavelength range to be measured, such as nitrogen gas) is supplied from the gas cylinder. The reference gas is divided into two, one enters the reference cell 11c through the flow meter M ₁ and the other communicates with 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.

[0020] 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.
One of the three-way valve V ₂ is connected to the first sample cell 11a through the _two- way valve V ₄ , and the other is connected to the three-way valve V ₁ . Further, a gas injector 21 (capacity 60 cc) for quantitatively injecting the sample gas or the base gas is interposed between the three-way valve V ₃ and the first sample cell 11a. The gas injector 21 is shaped like an injector having a piston and a cylinder, and the driving of the viston is performed 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.
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. A reference gas is introduced into the reference cell 11c and is exhausted. The length of the first sample cell 11 a is specifically 13 mm, and the second sample cell 11 a
Specifically, the length of b is 250 mm, and the length of the reference cell 11c is specifically 236 mm.

Reference numeral L indicates an infrared light source device. The infrared light source device L includes two waveguides 23 for irradiating infrared rays.
a and 23b are provided. Any method may be used to generate infrared rays. For example, a ceramic heater (surface temperature 45
0 ° C.) can be used. Further, a rotating chopper 22 that cuts off infrared rays at a constant cycle and passes through is provided. Of the infrared rays emitted from the infrared light source device L,
An optical path formed by those passing through the first sample cell 11a and the reference cell 11c is called a "first optical path", and a second optical path
The optical path formed by the one passing through the sample cell 11b is defined as “second
Optical path ”(see FIG. 2).

The code D detects infrared rays that have passed 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;
Of 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 24
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 kept at a constant temperature (25 ° C.) by a heater and a Peltier element, and the portions of the detecting elements in the packages 26a and 26b are kept at 0 ° C. by a Peltier element.

FIG. 2 is a sectional view showing a detailed structure of the cell chamber 11. The cell chamber 11 itself is made of stainless steel, and is sandwiched by metal plates (for example, brass plates) 12 at the top, bottom, left and right, and is sealed by a heat insulating material 14 via a heater 13 sandwiched at the top, bottom, left and right. 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 through the first sample cell 11a and the reference cell 11c in series, and a second optical path passes through the second sample cell 11b. Reference numerals 15 and 1
Reference numerals 6 and 17 denote sapphire transmission windows that transmit infrared rays. The cell chamber 11 is heated to a constant temperature (4
The temperature is controlled to be maintained at 0 ° C. III. Measurement procedure 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, base gas measurement-> reference gas measurement-> base gas measurement, sample gas measurement-> reference gas measurement-> sample gas measurement, etc. may be performed, but the same base gas and sample gas are measured twice. You have to do it, which reduces efficiency. The efficient former procedure will be described below.

During the measurement, the reference gas is constantly flowing in the reference gas 11c. III-1. Reference Measurement As shown in FIG. 3, a clean reference gas is flown in the gas channel and the cell chamber 11 of the isotope gas spectrometer for about 15 seconds at a flow rate of 200 ml per minute to clean the gas channel and the cell chamber 11. .

Next, as shown in FIG. 4, the gas flow path is changed and a reference gas is flowed to clean the gas flow path and the cell chamber 11. After about 30 seconds, each detection element 25
The light quantity is measured with a and 25b. The reference measurement is performed in this manner in order to calculate the absorbance. In this way, 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
Write ¹³ R ₁ . III-2. Base Gas Measurement Next, the reference gas is prevented from flowing through the first sample cell 11a and the second sample cell 11b, and the base gas is sucked by the gas injector 21 from the exhalation bag (FIG. 5).
reference).

After sucking the base gas, as shown in FIG. 6, the base gas is mechanically pushed out at a constant flow rate using a gas injector 21. During this period, each detection element 25
The light quantity is measured with a and 25b. In this way,
The light amount obtained by the first detection element 25a is written as ¹² B, and the light amount obtained by the second detection element 25b is written as ¹³ B. III-3. Reference measurement Again, the gas channel and the cell are washed and the light quantity of the reference gas is measured (see FIGS. 3 and 4).

In this way, the light amount ¹² R ₂ obtained by the first detecting element 25a and the light amount ¹³ R ₂ obtained by the second detecting element 25b are described. III-4. Sample gas measurement The reference gas is prevented from flowing through the first sample cell 11a and the second sample cell 11b, and the sample gas is sucked by the gas injector 21 from the exhalation bag (see FIG. 7).

After sucking the sample gas, as shown in FIG. 8, the sample gas is mechanically pushed out at a constant speed by using a gas injector 21. During this time, each detection element 2
The light amount is measured by 5a and 25b. In this way, the amount of light obtained by the first detection element 25a is set to ¹² S,
The amount of light obtained by the detection element 25b of ¹³ is written as ¹³ S. III-5. Reference measurement Again, the gas channel and the cell are washed and the light quantity of the reference gas is measured (see FIGS. 3 and 4).

[0032] 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. IV. Data processing IV-1. Calculation of Absorbance of Base Gas First, the amount of transmitted light of the reference gas ¹² R ₁ ,
^{Using 13} R ₁ , the amount of transmitted light of the base gas ¹² B, ¹³ B, and the amount of transmitted light of the reference gas ¹² R ₂ , ¹³ R ₂ , the absorbance of ¹² CO ₂ in the base gas ¹² Abs (B) and ¹³ CO ₂ Determine the absorbance ¹³ Abs (B).

[0033] 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 Abs (B), ¹³ Abs (B) = − log [2 ¹³ B / ( ¹³ R ₁ + ¹³ R ₂ )].

As described above, when the absorbance is calculated, the average value (R ₁ + R) of the light amounts of the reference measurements performed before and after is performed.
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, it is possible to quickly start the measurement without waiting for a complete thermal equilibrium (usually several hours) when starting up the device.

In addition, III. When the procedure of base gas measurement → reference gas measurement → base gas measurement → sample gas measurement → reference gas measurement → sample gas measurement, ...
¹² CO ₂ absorbance ¹² Abs (B) is, ¹² Abs (B) = - calculated by log _{^{[(12 B 1 + 12 B 2}} ) / 2 12 R ], ¹³ CO ₂ absorbance ¹³ Abs (B) is , ¹³ Abs (B) = − log [( ¹³ B ₁ + ¹³ B ₂ ) / 2 ¹³ R]. Here, R is the transmitted light amount of the reference gas, and B ₁ and B ₂ are the transmitted light amounts of the base gas before and after the measurement of the reference gas, respectively. IV-2. Calculation of absorbance of sample gas Next, the amount of transmitted light of the reference gas ¹² R ₂ ,
¹³ R ₂ , the sample gas transmitted light amount ¹² S, ¹³ S, and the reference gas transmitted light amount ¹² R ₃ , ¹³ R ₃ are used to absorb ¹² CO ₂ in the sample gas ¹² Abs (S) and ¹³ CO ₂
The absorbance of ¹³ Abs (S) is calculated.

[0036] 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 determined by ¹³ Abs (S) = − log [2 ¹³ S ( ¹³ R ₂ + ¹³ R ₃ )].

As described above, when the absorbance is calculated, the average value of the light amount of the reference measurement performed before and after is taken, and the average value and the light amount obtained by the sample gas measurement are used to calculate the absorbance. Therefore, the influence of drift can be offset. In addition, III. As described at the beginning of the above, base gas measurement → reference gas measurement → base gas measurement,
When the procedure of measuring the sample gas → measuring the reference gas → measuring the sample gas 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], the ¹³ CO ₂ absorbance of ¹³ Abs (S) is ¹³ Abs (S) = − log [( ¹³ S ₁ + ¹³ S ₂ ) / 2 ¹³ R] Desired. Here, R is the amount of transmitted light of the reference gas, and S ₁ and S ₂ are the amounts of transmitted light 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.

The calibration curve is prepared using the measured gas whose ¹² CO ₂ concentration is known and the measured gas whose ¹³ CO ₂ concentration is known. In order to obtain a calibration curve, the ¹² CO ₂ concentration is changed in the range of 0% to 6% and the absorbance of ¹² CO ₂ is measured. The horizontal axis is ¹² CO ₂ concentration, and the vertical axis is ¹² C
For O ₂ absorbance, plot and determine curve using 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.

The concentration of ¹³ CO ₂ is 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 individually measured, and the gas containing ¹² CO ₂ and ¹³ CO ₂ is mixed. , The absorbance of ¹³ CO ₂ is different. This is because the wavelength filter used has a bandwidth and the absorption spectrum of ¹² CO ₂ partially overlaps with the absorption spectrum of ¹³ CO ₂ . ^{12 in} this measurement
Since the gas to be measured is a mixture of CO ₂ and ¹³ CO ₂ , it is necessary to correct the overlap when determining the 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 obtained by using the above calibration curve
In the¹²CO_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_TwoWhen¹²CO_TwoThe 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 is 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 , and thus both values are almost the same. IV-5. Correction of concentration ratio The concentration ratio obtained as described above is a value deviated from the actual concentration ratio depending on the difference in ¹² CO ₂ concentration, as described in [Problems to be Solved by the Invention]. ing.

The cause of this deviation is not clear, but it is ¹² C.
It is considered that this is because the reflectance, the refractive index, the stray light, etc. are changed depending on the O ₂ concentration and further overlap with the error characteristic of the least square method used when the calibration curve is obtained. If the concentration ratio is calculated without correcting this deviation characteristic, a large error is expected to occur.Therefore, the concentration of the component gas is different, and the measured gas with a constant concentration ratio is created. Absorbances of ¹² Abs and ¹³ Abs are determined, the concentration and concentration ratio of the component gas are determined using the calibration curve, and the concentration ¹² Conc of the component gas is plotted on the horizontal axis and the concentration ratio ¹³ Conc / ¹² Conc is plotted on the vertical axis. .

The results are specifically shown in FIG. In the graph of FIG. 9, since the density ratio on the vertical axis is not standardized, it is easier to standardize the density ratio on the vertical axis. FIG. 10 shows a graph in which the concentration ratio on the vertical axis is standardized by setting the concentration ratio of the gas having the lowest CO ₂ concentration to be “1” (hereinafter, the normalized concentration ratio is referred to as “normalized concentration ratio”).

Further, in order to connect these plotted points, a least squares approximation is performed. The approximation formula is a quartic, F (x) = ax ⁴ + bx ³ + cx ² + dx tens e (F: normalized concentration ratio, a to e: coefficient, x: ¹² CO ₂ concentration) Since it is empirically known that this is a good approximation of, a quartic equation is used. In addition to the quartic equation, a spline function can be used.

The concentrations ¹² Conc (B) and ¹² Conc (S) of the component gases obtained for the exhaled air of the patient, which is the gas to be measured, are applied to the respective correction equations to obtain the normalized concentration ratio of the component gas,
Concentration ratio of measured gas obtained from measurement ¹³ Conc (B) / ¹² Co
Divide nc (B), ¹³ Conc (S) / ¹² Conc (S) by the normalized concentration ratio obtained from the correction formula to obtain the corrected concentration ratio.

Corrected density ratio = ¹³ Conc (B) / [ ¹² Conc (B) F ( ¹² Conc)] Corrected density ratio = ¹³ Conc (S) / [ ¹² Conc (S) F ( ¹² Conc) ] IV-6. 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: permill (percentage))

[0048]

EXAMPLE ¹² CO ₂ concentrations ¹² Conc is 1,2,3,4,5
And 6%, the concentration ratio ¹³ Conc / ¹² Conc is a constant value of 1.077
The isotope gas spectroscopic measurement was performed by using the measured gas (%). A concentration ¹² Conc of fit to the calibration curve ¹² CO ₂ absorbance obtained, and a concentration of ¹³ of ¹³ CO ₂ Conc measured, ¹² Conc
11 is plotted on the abscissa and ¹³ Conc / ¹² Conc on the ordinate. The result is shown in FIG.

The maximum value of ¹³ Conc / ¹² Conc is 1.083%,
The minimum value was 1.076%, and the difference was 0.007%. Next, when the concentration ratio ¹³ Conc / ¹² Conc was corrected using the correction formula, a flatter result was obtained as shown in FIG. In FIG. 12, the maximum value of ¹³ Conc / ¹² Conc is 1.
078%, the minimum value is 1.076%, the difference is 0.00
It was 15%.

Therefore, it was found that the variation width of ¹³ Conc / ¹² Conc is remarkably reduced by the correction using the correction formula.

[0051]

As described above, according to the isotope gas spectrometric measuring method or measuring apparatus of the present invention, when the gas to be measured containing a plurality of component gases is introduced into the cell and the spectroscopic measurement is performed, the concentration of the component gas is reduced. The ratio can be measured with better accuracy.

[Brief description of the drawings]

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

FIG. 2 is a cross-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 the gas flow path and the cell chamber of the isotope gas spectrophotometer for cleaning.

FIG. 4 is a diagram showing a gas flow path when a clean reference gas is flowed through the gas flow path and the cell chamber of the isotope gas spectrophotometer to wash and perform reference measurement.

FIG. 5: Reference gas is the first sample cell 11a,
It is a figure which shows the state in the middle of suck | inhaling the base gas from the exhalation bag with the gas injector 21 so that it may not flow through the 2nd sample cell 11b.

FIG. 6 is a diagram showing a gas flow path used when light amount is measured by the detection elements 25a and 25b while the base gas is sucked and then the base gas is mechanically pushed out at a constant speed by using the gas injector 21. FIG.

FIG. 7: Reference gas is the first sample cell 11a,
It is a figure which shows the state in the middle of inhaling the sample gas from the exhalation bag with the gas injector 21, without flowing through the 2nd sample cell 11b.

FIG. 8 shows the gas injector 21 after sucking the sample gas.
To extrude the sample gas mechanically at a constant speed,
It is a figure which shows a gas flow path when measuring the light quantity by each detection element 25a, 25b during this time.

FIG. 9: Concentration ratios of component gases differ¹³ConC /¹²Co
Absorbance of component gas for measured gas with nc constant¹²A
bs,¹³Abs is calculated and the concentration of the component gas is calculated using the calibration curve.
¹³Conc,¹²conc and concentration ratio¹³Conc / 12Conc is calculated and the component
Gas concentration¹²Cooc on the horizontal axis, concentration ratio¹³Conc /¹²Vertical Conc
It is a graph plotted on the axis.

FIG. 10 is a graph in which the concentration ratio ¹³ Conc / ¹² Conc on the vertical axis is standardized by the value when the ¹² CO ₂ concentration is ¹² Conc = 0.5%.

[11] For the measurement gas, of ¹² CO ₂ concentration ¹² Conc
And a concentration of ¹³ CO ₂ of ¹³ Conc are measured, and ¹² Conc is plotted on the horizontal axis and ¹³ Conc / ¹² Conc is plotted on the vertical axis.

[12] For the measurement gas, of ¹² CO ₂ concentration ¹² Conc
And the concentration of ¹³ CO ₂ ¹³ Conc are measured, and the concentration ratio is ¹³ Conc /
After correcting ¹² Conc, ¹² Conc on the horizontal axis, ¹³ Conc / ¹² Conc
Is a graph in which is plotted on the vertical axis.

[Explanation of symbols]

D infrared detecting device L infrared light source device M _1, M ₂ flowmeters 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 1st detection element 24b 2nd wavelength filter 25b 2nd detection element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiji Ikegami 112 Higashimeisaka, Mizuguchi-cho, Koga-gun, Shiga (72) Inventor Kazunori Tsutsui 38, 670 Mizuguchi, Mizuguchi-cho, Koga-gun, Shiga

Claims (5)

[Claims] 1. An isotope gas for measuring the concentration of a component gas by introducing a measurement gas containing a plurality of component gases into a cell, measuring the amount of transmitted light having a wavelength suitable for each component gas, and processing the data. In the spectroscopic measurement method, the first step of introducing the gas to be measured into the cell and determining the absorbance corresponding to the wavelength of each component gas, the calibration curve created by measuring the gas to be measured containing the component gas of known concentration The second step of obtaining the concentration and concentration ratio of the component gas by using, and the concentration of the component gas using the correction line created by measuring the measured gas whose concentration and concentration ratio of the component gas are known. A method for spectroscopically measuring isotope gas, comprising a third step of correcting the concentration ratio of component gases in accordance with the above. 2. The correction line in the third step is to obtain the absorbance corresponding to the wavelength of the component gas for the gas to be measured whose concentration and concentration ratio of the component gas are known, and use the calibration curve to calculate the component gas Obtained by obtaining the concentration and the concentration ratio, and plotting the obtained concentration and concentration ratio of the component gas, the correction method in the third step, the correction method of the component gas obtained in the second step for the measured gas Apply the concentration to the correction line to obtain the concentration ratio correction value of the component gas, and divide the concentration ratio of the measured gas obtained in the second step by the concentration ratio correction value of the component gas obtained from the correction line. The isotope gas spectroscopic measurement method according to claim 1. 3. The correction line in the third step is obtained by approximating the obtained relationship between the concentration of the component gas and the concentration ratio by a quartic curve. Body gas spectroscopy method. 4. A plurality of component gases are carbon dioxide ¹² CO
_2. The isotope gas spectroscopic measurement method according to claim 1, which is ₂ and carbon dioxide ¹³ CO ₂ . 5. A measurement gas containing a plurality of component gases is introduced into a cell, the amount of transmitted light of the wavelengths left in each component gas is measured, and the measured amount of light is processed by data processing means. In the isotope gas spectroscopic measurement device for measuring the concentration of the component gas, the data processing means is based on the light amount of light corresponding to the wavelength suitable for each component gas, which is measured for the measured gas introduced into the cell. Absorbance calculating means for obtaining the absorbance, concentration calculating means for obtaining the concentration and concentration ratio of the component gas using the calibration curve created by measuring the measured gas containing the component gas of known concentration, and the component gas Using a correction line created by measuring the measured gas whose concentration and concentration ratio are known, the concentration calculation method according to the concentration of the component gas obtained by the concentration calculation means is calculated. Isotope Gas spectroscopic measurement apparatus which comprises a concentration ratio correction means for correcting the concentration ratio of gas components obtained by.