JP2947742B2 - Isotope gas spectrometry method and measurement device - 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 relates to an isotope gas spectrometry method and apparatus for measuring the concentration or concentration ratio of an isotope gas by focusing on the light absorption characteristics of the isotope.

[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]

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 ¹³ 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.¹³CO_TwoConcentration calibration curve creation
Perform in a similar manner. However, infrared spectroscopy¹³CO_Twoconcentration
Or¹³CO_TwoConcentration ratio (¹³CO_Twoconcentration/¹²CO_TwoConcentration saw
I say. The same applies hereinafter) when measuring
The actual difference in oxygen concentration¹³CO_TwoDark
Degree or¹³CO_TwoThe result that is different from the concentration ratio appears,
It has been found by various experiments.

[0009] Figure 9, ¹³ CO ₂ concentration so that the concentration of the same oxygen different, making the measurement gas obtained by diluting ¹³ CO ₂ in oxygen and nitrogen, relative to oxygen content, ¹³ CO ₂ concentration ratio 5 is a graph in which the measured values are plotted. However, ¹³ CO ₂
The measured value of the concentration ratio is ¹³ CO ₂ when the oxygen content is 0%.
Standardized by concentration ratio. From this graph, it can be seen that the ¹³ CO ₂ concentration ratio is constant and changes according to the oxygen concentration.

Therefore, without knowing this fact, oxygen
Gas to be measured including¹³CO_TwoConcentration or¹³CO_TwoDark
If you measure the power ratio, a different result will appear
Is clear. FIG. 10 shows the measured gas containing no oxygen.
about,¹³CO_TwoThe results of measurement with various density ratios
It is a graph shown. The horizontal axis is the actual¹³CO_TwoConcentration ratio, vertical axis
Is¹³CO _TwoIt represents the measured value of the concentration ratio. However,¹³CO_TwoDark
The degree ratio is¹³CO_TwoNormalized with the smallest value of concentration ratio
You.

FIG. 11 is a graph showing the results of measurement of each gas to be measured containing oxygen at a high concentration (about 90%) with various ¹³ CO ₂ concentration ratios. The horizontal axis is the actual ¹³ CO
_{2 The} concentration ratio, and the vertical axis represents the measured value of the ¹³ CO ₂ concentration ratio. However, the ¹³ CO ₂ concentration ratio is normalized by the smallest value of the ¹³ CO ₂ concentration ratio. Comparing FIGS. 10 and 11, in the graph of FIG. 10, and the measured actual ¹³ CO ₂ concentration ratio ¹³
The correlation with the CO ₂ concentration ratio (slope of the graph) is almost 1: 1 whereas the graph of FIG. 11 shows the actual ¹³ CO ₂ concentration.
The correlation between the concentration ratio and the measured ¹³ CO ₂ concentration ratio has changed to about 1: 0.3.

As described above, the measured value of the ¹³ CO ₂ concentration or the ¹³ CO ₂ concentration ratio is affected by the oxygen concentration of the gas to be measured, although the cause is not well understood. If the concentration or concentration ratio of the component gas is obtained without correction based on the oxygen concentration, it is expected that a large error will occur. Therefore, the present invention solves the above-mentioned technical problem, introduces a gas to be measured containing carbon dioxide ¹³ CO ₂ as a component gas into a cell, and precisely measures the concentration or concentration ratio of the component gas when performing spectroscopic measurement. It is an object of the present invention to realize an isotope gas spectroscopic measurement method and a measurement apparatus that can perform measurement.

[0013]

According to the isotope gas spectrometry of the present invention, a gas to be measured is introduced into a cell, and a component gas ¹³ CO 2 is supplied.
First step of determining the absorbance corresponding to ₂ wavelengths, by using a calibration curve prepared with ¹³ CO ₂ of a known concentration by measuring including gas, a second seeking the ¹³ CO ₂ concentration Step, and measure the oxygen concentration contained in the gas to be measured,
Using the correction curve prepared by concentration of the oxygen concentration and ¹³ CO ₂ is measuring a known gas, in which a third step of correcting the concentration of ¹³ CO ₂ in accordance with the measured oxygen concentration (Claim 1).

Further, proportional gas spectroscopic measurement method of the present invention is a plurality of component gases carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO _2, guides the measurement gas to the cell, ¹² CO ₂
And ¹³ a first step of determining the absorbance corresponding to the wavelength of CO _2, by using a calibration curve prepared by measuring a gas containing ¹² CO ₂ and ¹³ CO ₂ in the known concentration, ¹² CO
_{2 to determine} the concentration of ¹³ CO ₂ , the second step of determining the concentration ratio of ¹² CO ₂ and ¹³ CO _2, and measure the concentration of oxygen contained in the gas to be measured, oxygen concentration and ¹² CO ₂ and ¹³
Using the correction curve obtained by the concentration of CO ₂ measuring a known gas, ¹² C depending on the measured oxygen concentration
The method includes a third step of correcting the concentration ratio between O ₂ and ¹³ CO ₂ (claim 2).

According to the method described above, as compared with conventional methods, in the third step, the oxygen concentration by using the correction curve prepared was measured by the oxygen concentration measuring a known gas A method of correcting the concentration or the concentration ratio of the component gas according to the above is added. By this correction, the concentration of component gas should be a constant value, but the phenomenon discovered this time, that the measured concentration of component gas fluctuates according to the difference in oxygen concentration, is corrected, and the concentration or concentration of component gas is corrected. The measurement accuracy of the ratio can be improved.

The oxygen concentration may be detected using various oxygen sensors, or may be calculated by obtaining the absorbance in an oxygen molecule spectrum by a spectroscopic method. The correction line in the third step of the method according to claim 1, wherein the concentration of ¹³ CO ₂ and the oxygen concentration are known .
For gas, obtains the absorbance corresponding to a wavelength of ¹³ CO ₂ is obtained a ¹³ CO ₂ concentration using the calibration curve obtained by plotting the concentration of ¹³ CO ₂ obtained relative to the oxygen concentration The correction method in the third step is as follows:
By applying the concentration of oxygen gas obtained in the third step for the gas to be measured to a correction line, a concentration correction value of ¹³ CO ₂ was obtained,
This is performed by dividing the concentration of ¹³ CO ₂ obtained in the second step by the concentration correction value obtained from the correction line (claim 3).

The correction line in the third step of the method according to the second aspect is, specifically, ¹² CO ₂ and ¹³ CO _2.
Concentrations and the oxygen concentration for known gas of, ¹² CO ₂
And the absorbance corresponding to the wavelength of ¹³ CO ₂ is obtained, the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ is obtained using the calibration curve, and the obtained concentration ratio is plotted against the oxygen concentration. The correction method in the third step is to apply a concentration line of the oxygen gas obtained in the third step with respect to the gas to be measured to obtain a concentration ratio correction value between ¹² CO ₂ and ¹³ CO ₂ , This is performed by dividing the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ obtained in the step 2 by the concentration ratio correction value obtained from the correction line (claim 4).

An isotope gas spectrometer of the present invention is a measuring device for performing the above-mentioned isotope gas spectrometry method of the present invention, and is provided to a cell as a means for realizing a data processing function. An absorbance calculating means for obtaining an absorbance based on the amount of light corresponding to the wavelength suitable for each component gas measured for the measured ¹² CO ₂ and ¹³ CO ₂ , and a known concentration of ¹² CO ₂ and ¹³ CO ₂ . using a calibration curve prepared by measuring the free gas, of ¹² CO ₂ concentration and ¹³ CO
₂ , concentration calculating means for determining the concentration ratio of ¹² CO ₂ and ¹³ CO ₂ , oxygen concentration measuring means for measuring the oxygen concentration contained in the gas to be measured, oxygen concentration and ¹² CO ₂ and
Using the correction curve prepared by the ¹³ CO ₂ concentration measuring a known gas, depending on the measured oxygen concentration
A concentration ratio correcting means for correcting the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ is included (claim 5).

[0019]

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 performing spectral measurement of the concentration ratio,
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 is 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.

The exhalation bags before and 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.

[0022] 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, the gas injector 21 for quantitatively injecting the sample gas or the base gas (volume 60 cc) is interposed. The gas injector 21 has a shape like a syringe having a piston and a cylinder. The drive of the piston 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 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.

An O ₂ sensor 18 is provided in an exhaust pipe led from the reference cell 11c. As the O ₂ sensor 18, a commercially available oxygen sensor can be used. For example, a solid electrolyte gas sensor such as a zirconia sensor or an electrochemical gas sensor such as a galvanic cell type sensor can be used. Symbol L indicates an infrared light source device. The infrared light source device L includes two waveguides 23a and 23b for irradiating infrared rays. The method of generating infrared rays may be any method, for example, a ceramic heater (surface temperature of 450 ° C.) or the like can be used. In addition, a rotating chopper 22 that cuts off and passes infrared rays at a constant cycle is provided. Among the infrared rays emitted from the infrared light source device L, an optical path formed by a light passing through the first sample cell 11a and the reference cell 11c is referred to as a "first light path", and an optical path formed by a light passing through the second sample cell 11b. Is referred to as a “second optical path” (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;
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 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 by a metal plate (for example, a brass plate) 12, and is sealed by a heat insulating material 14 via a heater 13 sandwiched 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 between 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.). 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, 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, 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 flowed through the gas flow path and the cell chamber 11 for about 15 seconds at a rate of about 200 ml per minute into the gas flow path and the cell chamber 11 of the isotope gas spectrometer.
Wash.

Next, as shown in FIG. 4, a reference gas is flowed 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. III-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. III-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).

As described above, 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. III-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 in, 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. III-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).

Thus, the light quantity obtained by the first detection element 25a is written as ¹² R ₃ , and the light quantity obtained by the second detection element 25b is written as ¹³ R ₃ . IV. Data processing IV-1. Calculation of absorbance of base gas First, the transmitted light amount of the reference gas ¹² R ₁ ,
^{Using 13} R ₁ , the transmitted light amount of the base gas ¹² B, ¹³ B, and the transmitted light amount 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 The absorbance is determined as ¹³ Abs (B).

[0035] 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.

It should be noted that III. As described at the beginning of the above, when the procedure of base gas measurement → reference gas measurement → base gas measurement → sample gas measurement → reference gas measurement → sample gas measurement, etc. is adopted, the base 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) = - it is determined by the 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 transmitted light amount of the reference gas ¹² R ₂ ,
^{Using 13} R ₂ , the transmitted light amount of the sample gas ¹² S, ¹³ S and the transmitted light amount of the reference gas ¹² R ₃ , ¹³ R ₃ , the absorbance of ¹² CO ₂ in the sample gas, ¹² Abs (S), and ¹³ CO ₂
Absorbance ¹³ Request and Abs (S).

[0038] 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 taken, and the absorbance is calculated using the average value and the light amount obtained by the sample gas measurement. Therefore, the influence of the drift can be offset. In addition, III. 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.

The calibration curve is created by using a measured gas having a known ¹² CO ₂ concentration and a measured gas having a known ¹³ CO ₂ concentration. Strictly speaking, a gas containing ¹² CO ₂ and a gas containing ¹³ CO ₂ are measured independently, and a gas containing ¹² CO ₂ and ¹³ CO ₂ is measured. So, 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 overlap. In the book shelf determination, 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, data obtained by correcting the partial overlap of the absorption spectrum is actually used.

[0041] The ¹² CO ₂ concentration is obtained a calibration curve, ¹² the CO ₂ concentration taking 20 points in the range of about 0% to 6%, measuring the absorbance of ¹² CO _2. The curve passing through each data point is determined using the least squares method. The approximation by the quadratic equation resulted in a curve with relatively few errors.
In the present embodiment, a calibration curve approximated by a quadratic equation is employed.

Next, five points of data are taken in the vicinity of the concentration of ¹² CO ₂ determined for the base gas using the above calibration curve. This 5-point data range is equivalent to 1.5% in terms of the concentration range, and is 1/4 of the calibration curve range (6%) obtained above. Then, a calibration curve is created again in this narrow range. When a calibration curve is created using such a narrow range of data, it is recognized that the fitting between the data and the approximate curve is improved, and the error in creating the calibration curve is extremely reduced. Therefore, using the re-created calibration curve, the absorbance of the base gas was ¹² Abs.
Calculate the concentration of the component gas from (B).

Similarly, for the sample gas, ¹² CO
_Find the concentration of ₂ . Next, determine the calibration curve for ¹³ CO ₂ concentration, the ¹³ CO ₂ concentration 0.00% 0.07%
Take 20 points in the range and measure the absorbance of ¹³ CO ₂ . The curve passing through each data point 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.

Next, five points of data are obtained for the base gas near the ¹³ CO ₂ concentration determined using the above calibration curve. This 5-point data range corresponds to 0.015% in terms of the concentration range, which is 1/4 of the calibration curve range (0.07%) obtained above. Then, a calibration curve is created again in this narrow range. When a calibration curve is created using such a narrow range of data, it is recognized that the fitting between the data and the approximate curve is improved, and the error in creating the calibration curve is extremely reduced. Therefore, the concentration of the component gas is determined from the absorbance ¹³ Abs (B) of the base gas using the re-created calibration curve.

Next, the same applies to sample gas.
¹³ Determine the concentration of CO ₂ . The concentration of ¹² CO ₂ in the base gas, determined using the calibration curve, is calculated as ¹² Conc (B),
Further corrected the concentration of ¹³ CO ₂ in the base gas
¹³ Conc (B), the concentration of ¹² CO ₂ in the sample gas ¹²
Conc (S), the concentration of ¹³ CO ₂ in the corrected sample gas is written as ¹³ Conc (S). IV-4. Calculation of concentration ratio The concentration ratio between ¹³ CO ₂ and ¹² CO ₂ is determined. The ¹³ CO ₂ concentration ratio in the base gas is: ¹³ Conc (B) / ¹² Conc (B) The ¹³ CO ₂ concentration ratio in the sample gas is obtained by ¹³ ConC (S) / ¹² 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 , so that both have substantially the same value. IV-5. Correction of Concentration Ratio Then, the oxygen concentration correction according to the present invention is performed on the ¹³ CO ₂ concentration ratio of the base gas and the sample gas.

Therefore, the ¹³ CO ₂ concentration ratio is corrected using a graph (FIG. 9) in which the measured value of the ¹³ CO ₂ concentration ratio is plotted against the oxygen content of the gas to be measured. Specifically, the oxygen concentration value contained in the exhaled air detected by the O ₂ sensor 18 is applied to the horizontal axis in FIG. 9 to obtain the ¹³ CO ₂ concentration ratio normalized value. Then, the ¹³ CO ₂ concentration ratio of the base gas and the sample gas is divided by the ¹³ CO ₂ concentration ratio standardized value. Then, the ¹³ CO ₂ concentration ratio corrected by the oxygen concentration can be obtained. 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: per mill (per thousand)) Modifications The present invention is not limited to the above embodiments.
In the above embodiment, the base gas and sample gas of ¹² C
The O ₂ concentration and ¹³ CO ₂ concentration were determined, the concentration ratio was calculated, and the oxygen concentration was corrected for this concentration ratio. But,
¹² CO ₂ concentration of base gas and sample gas, ¹³ CO ₂
Determine the concentration and correct the oxygen concentration to obtain ¹² CO ₂ concentration, ¹³ C
It is also possible to correct the O ₂ concentration and then take the concentration ratio.

[0049]

[Example] For a gas to be measured containing oxygen in a high concentration (about 90%), the absorbance was measured while changing the ¹³ CO ₂ concentration ratio (known), and the ¹³ CO ₂ concentration ratio was measured by applying to a calibration curve. . Further, by using the correction line determined in FIG. 9, ¹³ CO
_{2. The} concentration ratio was corrected. When the actual ¹³ CO ₂ concentration ratio was normalized and plotted on the horizontal axis, and the corrected ¹³ CO ₂ concentration ratio was normalized and plotted on the vertical axis, the result was as shown in FIG.

The actual¹³CO_TwoConcentration ratio and measurement¹³CO_Twoconcentration
The correlation with the ratio (slope of the graph) is almost 1: 1
You. This is the graph of FIG.¹³CO_TwoConcentration ratio
And measurement ¹³CO_TwoThe correlation with the concentration ratio is about 1: 0.3
This is a significant improvement compared to Therefore,
By correcting using a correction line,¹³CO_TwoConcentration ratio
It was found that the accuracy was significantly improved.

[0051]

As described above, according to the isotope gas spectroscopic measurement method or measuring apparatus of the present invention, when a gas to be measured containing carbon dioxide ¹³ CO ₂ as a component gas is introduced into a cell and spectroscopically measured, Since the correction based on the concentration of oxygen contained in the measurement gas is performed, the concentration or concentration ratio of the component gas 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 sectional view showing the structure of a cell chamber.

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.

FIG. 9: A gas to be measured is prepared by diluting ¹³ CO ₂ with oxygen and nitrogen so that the ¹³ CO ₂ concentration ratio is the same and the oxygen concentration is different, and the ¹³ CO ₂ concentration ratio is measured with respect to the oxygen content. It is the graph which plotted the value. ¹³ The measured value of the CO ₂ concentration ratio is
It is standardized by the ¹³ CO ₂ concentration ratio when the oxygen content is 0%.

FIG. 10 shows ¹³ CO for the gas to be measured containing no oxygen.
₂ is a graph showing the results of measurement with changing the concentration ratio. The horizontal axis represents the actual ¹³ CO ₂ concentration ratio, and the vertical axis represents the measured value of the ¹³ CO ₂ concentration ratio. ^{The 13} CO ₂ concentration ratio is standardized by the smallest value of the ¹³ CO ₂ concentration ratio.

FIG. 11 is a graph showing the results of measurement of a gas to be measured containing oxygen at a high concentration (about 90%) while changing the ¹³ CO ₂ concentration ratio. The horizontal axis is the actual ¹³ CO ₂ concentration ratio, and the vertical axis is ¹³
It represents the measured value of the CO ₂ concentration ratio. ^{The 13} CO ₂ concentration ratio is ¹³ C
It is standardized by the smallest value of the O ₂ concentration ratio.

FIG. 12 is a gas to be measured containing oxygen at a high concentration (about 90%).
about,¹³CO_TwoThe measurement was performed while changing the concentration ratio, and
9 is a graph showing a result of the correction. The horizontal axis is the actual¹³
CO_TwoConcentration ratio, vertical axis is¹³CO_TwoIndicates the correction value of the density ratio.
¹³CO_TwoThe concentration ratio is¹³CO _TwoSpecify the smallest value of the concentration ratio.
It has been formalized.

[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 18 O ₂ sensor 21 Gas injector 24a 1 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) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 21/00-21/01 G01N 21/17-21/61 G01N 33/497 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A gas to be measured containing carbon dioxide ¹³ CO ₂ as a component gas is introduced into a cell, the amount of transmitted light having a wavelength suitable for the component gas is measured, and data processing is performed to measure the concentration of the component gas. in proportional gas spectroscopic measurement methods, lead to the measurement gas to the cell, a first step of determining the absorbance corresponding to a wavelength of ¹³ CO _2, is created by measuring a gas containing ¹³ CO ₂ in the known concentration Using the calibration curve, ¹³ CO ₂
A second step of determining the concentration of oxygen and the concentration of oxygen contained in the gas to be measured, and the oxygen concentration and ¹³ CO ₂ concentration are measured using a correction line created by measuring a known gas. A third step of correcting the concentration of ¹³ CO ₂ according to the oxygen concentration. 2. Carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO 2
Isotope gas spectroscopy to measure the concentration or concentration ratio of component gases by introducing the gas to be measured containing ₂ as a component gas into a cell, measuring the amount of transmitted light having a wavelength suitable for each component gas, and processing the data. in the method, measuring the gas containing lead to the measurement gas to the cell, a first determining the absorbance corresponding to a wavelength of ¹² CO ₂ and ¹³ CO ₂ process, the ¹² CO ₂ and ¹³ CO ₂ in the known concentration Using the calibration curve created by
Seeking ¹² CO ₂ concentrations and the ¹³ CO ₂ concentration, ¹² CO ₂ and ¹³
A second step of obtaining the concentration ratio of the CO _2, as well as to measure the concentration of oxygen contained in the measurement gas, the oxygen concentration and ¹² CO
Using the correction curve prepared by concentration of ₂ and ¹³ CO ₂ is measuring a known gas, the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ in response to the measured oxygen concentration in the measurement gas was An isotope gas spectrometry method, comprising a third step of correcting. 3. The correction line in the third step is: ¹³ CO
About ₂ concentration and the oxygen concentration is known gas, obtains the absorbance corresponding to a wavelength of ¹³ CO _2, by using the calibration curve ¹³ C
The concentration of O ₂ was obtained, and the obtained concentration of ¹³ CO ₂ was plotted against the oxygen concentration. The correction method in the third step was obtained in the third step for the gas to be measured. the concentration of the oxygen gas obtains a ¹³ CO ₂ concentration correction value by applying the correction line, the concentration of ¹³ CO ₂ obtained in the second step, characterized by dividing by the density correction value obtained from the correction line The isotope gas spectrometry method according to claim 1, wherein 4. The correction line in the third step is ¹² CO
Concentrations and the oxygen concentration of ₂ and ¹³ CO ₂ is the known gas, obtains the absorbance corresponding to a wavelength of ¹² CO ₂ and ¹³ CO _2, the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ using the calibration curve Is obtained by plotting the determined concentration ratio between ¹² CO ₂ and ¹³ CO ₂ with respect to the oxygen concentration. The correction method in the third step is a method in which the gas to be measured is obtained in the third step. the concentration of oxygen gas obtained concentration ratio correction value for the ¹² CO ₂ and ¹³ CO ₂ by applying the correction line, the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ obtained in the second step,
3. The isotope gas spectrometry method according to claim 2, wherein the isotope gas is divided by the concentration ratio correction value obtained from a correction line. 5. Carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO 2
_The gas to be measured containing ₂ as a component gas is led to the cell, the amount of transmitted light having a wavelength suitable for each component gas is measured, and the measured light amount is subjected to data processing by data processing means, thereby obtaining the concentration of the component gas. or in isotope gas spectroscopic measurement apparatus for measuring the concentration ratio, the data processing means, were measured for the measurement gas introduced into the cell, ¹² CO
Calibration curve prepared by measuring the absorbance calculation means for determining the absorbance based on the amount of light corresponding to a wavelength suitable for ₂ and ¹³ CO _2, a gas containing ¹² CO ₂ and ¹³ CO ₂ in the known concentration using, determine the ¹² CO ₂ concentrations and the ¹³ CO ₂ concentration in the measurement gas, and ¹² CO ₂
A density calculating means for calculating a concentration ratio between ¹³ CO _2, and the oxygen concentration measuring means for measuring a concentration of oxygen contained in the measurement gas, the concentration of the oxygen concentration and ¹² CO ₂ and ¹³ CO ₂ are known gas measurement Isotope gas spectroscopy, comprising a concentration ratio correcting means for correcting the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ in accordance with the measured oxygen concentration using the correction line created by measuring device.