JP2947737B2 - 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 of an isotope gas by focusing on the difference in the light absorption characteristics of the isotopes.

[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 breath of the patient, specifically the concentration ratio of ¹³ CO ₂ to ¹³ CO ₂ , which is the final metabolite, is measured. If it can, the existence of the HP can be confirmed.

However, the concentration ratio between ¹³ CO ₂ and ¹³ CO ₂ is as large as 1: 100 in nature, so that it is difficult to measure the concentration ratio in the breath 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
Creation is performed in the same manner. However, infrared spectroscopy
When measuring, the relationship between concentration and absorbance is Lambert-Beer's
A calibration curve is created assuming that it follows the law, but Lambert-Be
The er law itself is an approximation, and in fact Lambert-Beer's
May not follow the rules. Therefore, the calibration curve
Calibration curve works well for limited data points
It is conceivable that no fitting is performed.

FIG. 9 shows the density ratio (¹³CO_Twoconcentration/¹²CO_Two
Concentration) is constant (1.077%) ¹²CO_TwoDifferent concentration
Measure the absorbance of each gas to be measured and create
Using the calibration curve¹²CO_TwoDetermine the concentration and create the calibration
Using lines¹³CO_TwoDetermine the concentrations and calculate their concentration ratio professionally.
It is the graph which was set. According to the graph,¹²CO_TwoDark
At different degrees, the measured concentration ratio is the actual concentration ratio (1.
077%).

Although the cause of this shift is not well understood, the reflectance, refractive index, stray light, and the like change depending on the density, and furthermore, the results overlap with the error characteristic of the least square method used when the calibration curve was obtained. It is considered to be. If the concentration of the component gas is obtained without correcting the characteristics of the deviation, it is expected that a large error will occur.

Therefore, the present invention solves the above-mentioned technical problem, and introduces a gas to be measured including a plurality of component gases into a cell.
It is an object of the present invention to realize an isotope gas spectrometry method and a measurement device capable of accurately measuring the concentration ratio of component gases when performing spectrometry.

[0012]

Isotope Gas spectrometry method of the present invention SUMMARY OF] is the carbon dioxide ¹² CO _2, carbon dioxide ¹³ CO
Leads to the measurement gas containing ₂ as component gases into a cell, ¹²
First step of determining the absorbance corresponding to the wavelength of the CO ₂ and ¹³ CO _2, by using a calibration curve prepared by measuring a gas containing ¹² CO ₂ and ¹³ CO ₂ in the known concentration, the measurement gas seeking ¹² CO ₂ and ¹³ CO ₂ concentration, ¹² CO ₂
When the second step of determining a concentration ratio between ¹³ CO _2, and ¹² C
Using the correction curve prepared by concentration ratio of O ₂ and ¹³ CO ₂ concentrations and ¹² CO ₂ and ¹³ CO ₂ is measuring a known gas, ¹² CO ₂ in accordance with the concentration of ¹² CO ₂ And ¹³ C
This includes a third step of correcting the concentration ratio with O ₂ .

According to the arrangement, as compared with conventional methods, in the third step, the concentration ratio of the concentrations and ¹² CO ₂ in CO ₂ and ¹³ CO ₂ and ¹³ CO ₂ are known gas measurement A method of correcting the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ according to the concentration of ¹² CO ₂ using a correction line created by the above method has been added. By the correction of the concentration ratio, the concentration ratio of the component gas should be originally constant, but the concentration ratio of the component gas fluctuates according to the difference in the concentration of the component gas.
By correcting the phenomenon that has been seen in the past, the measurement accuracy of the concentration ratio of the component gas can be improved.

[0014] Correction line in the third step, specifically, the ¹² CO ₂ and ¹³ CO ₂ concentrations and ¹² CO ₂ and ¹³ C
Concentration ratio of O ₂ is the known gas, ¹² CO ₂ and ¹³
Obtains the absorbance corresponding to the wavelength of the CO _2, the concentration of ¹² CO ₂ and ¹³ CO ₂ using the calibration curve and ¹² CO ₂ and ¹³ CO
₂ and the concentration ratio of the obtained ¹² CO ₂ and ¹²
It is obtained by plotting the concentration ratio between CO ₂ and ¹³ CO _2, and the correction method in the third step is a method of correcting the concentration of ¹² CO ₂ obtained in the second step for the gas to be measured.
Concentrations by applying the correction line ¹² CO ₂ and determine the concentration ratio correction value for the ¹³ CO _2, the ¹² CO ₂ obtained in the second step ¹³
This is performed by dividing the concentration ratio with CO ₂ by the concentration ratio correction value obtained from the correction line (claim 2).

In the method of claim 2, the obtained ¹² C
The relationship between the concentration of O ₂ and the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ is
It can be approximated by a fourth-order curve (claim 3). FIG.
This is because it has been empirically known that the deviation graph as shown in FIG.

An isotope gas spectrometer of the present invention is a measuring device for performing the above-described isotope gas spectrometry method of the present invention, and is provided to a cell as a means for realizing a data processing function. Was measured for the gas to be measured,
And absorbance calculation means for determining the absorbance based on the amount of light corresponding to a wavelength suitable for ¹² CO ₂ and ¹³ CO _2, is created by measuring a gas containing ¹² CO ₂ and ¹³ CO ₂ in the known concentration Using the calibration curve, ¹² CO ₂
And determine the concentration of ¹³ CO _2, ¹² a density calculating means for calculating a concentration ratio between CO ₂ and ¹³ CO _2, the concentration ratio of ¹² CO ₂ and ¹³ CO ₂ concentrations and ¹² CO ₂ and ¹³ CO ₂ known using the correction curve prepared by measuring the gas, ¹² CO ₂ and ¹³ CO determined by the concentration calculating means in accordance with the ¹² CO ₂ concentration determined by the concentration calculating means
And a density ratio correcting means for correcting the density ratio with the _second (claim 4).

[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
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 an 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.

[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.
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.

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 code 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,
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 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.). 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 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, the gas flow path is changed to supply a reference gas, 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).

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. 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).

The amount of light obtained by the first detecting element 25a in this manner is written as ¹² R ₃ , and the amount of light obtained in the second detecting 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).

[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 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).

[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, 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.

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 ¹² 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.

Further, the ¹³ CO ₂ concentration is adjusted 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, 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 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. ^{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 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_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 , so that both have substantially the same value. IV-5. Correction of concentration ratio The concentration ratio obtained as described above is a value deviated from the actual concentration ratio in accordance with the difference in ¹² CO ₂ concentration, as described in [Problems to be Solved by the Invention]. ing.

[0043] do not know the cause of this shift, but, ¹² C
It is considered that the result is that the reflectance, the refractive index, the stray light, and the like change depending on the O ₂ concentration, and overlap with the error characteristic of the least square method used when the calibration curve was obtained. If the concentration ratio is calculated without correcting the deviation characteristics, it is expected that a large error will occur.Therefore, the concentration of the component gas is different, and the concentration ratio is constant. Absorbances ¹² Abs and ¹³ Abs are determined, and the concentration and concentration ratio of the component gas are determined using the above 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. .

This result is specifically shown in FIG. In the graph of FIG. 9, since the concentration ratio on the vertical axis is not standardized, it is easier to handle if the concentration ratio on the vertical axis is standardized. FIG. 10 shows a graph in which the concentration ratio of the vertical axis is normalized with the concentration ratio of the gas having the lowest CO ₂ concentration being “1” (the normalized concentration ratio is hereinafter referred to as “normalized concentration ratio”).

Further, in order to connect these plotted points, a least square approximation is performed. Approximate expression, ^{quartic, F (x) = ax 4} + bx 3 + cx 2 + dx ten e (F: normalized concentration ratio, a to e: coefficient, x: ¹² CO ₂ concentration) those expressed in the precision Since it is empirically known that a good approximation of Note that a spline function may be used instead of the quartic equation.

The standardized concentration ratios of the component gases are obtained by applying the component gas concentrations ¹² Conc (B) and ¹² Conc (S) obtained for the patient's breath, which is the gas to be measured, to the correction equations, respectively.
Concentration ratio of measured gas obtained from measurement ¹³ Conc (B) / ¹² Co
nc (B), ¹³ Conc (S) / ¹² Conc (S) are divided by the normalized concentration ratio obtained from the correction expression to obtain a corrected concentration ratio.

Density ratio after correction = ¹³ Conc (B) / [ ¹² Conc (B) F ( ¹² Conc)] Density ratio after correction = 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: per mille (per thousand))

[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 spectrometry was performed. 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
Is plotted on the abscissa and ¹³ Conc / ¹² Conc on the ordinate, as shown in FIG.

The maximum value of ¹³ Conc / ¹² Conc is 1.083%,
The minimum was 1.076%, with a difference of 0.007%. Next, when the concentration ratio ¹³ Conc / ¹² Conc was corrected using the correction formula, a more flat 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%, and the difference is 0.00
15%.

Therefore, it was found that the range of fluctuation of ¹³ Conc / ¹² Conc was significantly reduced by performing correction using the correction formula.

[0051]

As described above, according to the isotope gas spectroscopic measuring method or measuring apparatus of the present invention, when a gas to be measured containing a plurality of component gases is guided to a cell and the spectroscopic measurement is performed, the concentration of the component gases 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 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.

FIG. 9: Concentration ratio of component gas is different¹³ConC /¹²Co
Absorbance of component gas for the gas to be measured where nc is constant¹²A
bs,¹³Determine Abs and use the calibration curve to determine the concentration of the component gas.
¹³Conc,¹²conc and concentration ratio¹³Find Conc / 12Conc and find the component
Gas concentration¹²Cooc on the horizontal axis, concentration ratio¹³Conc /¹²Conc vertical
It is a graph plotted on an axis.

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

[11] For the measurement gas, of ¹² CO ₂ concentration ¹² Conc
If, by measuring the concentration ¹³ of ¹³ CO ₂ Conc, the ¹² Conc the horizontal axis is a graph blotted ¹³ Conc / ¹² Conc in a vertical axis.

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

[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

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazunori Tsutsui 38, 670, Mizuguchi, Mizuguchi-machi, Koka-gun, Shiga Prefecture (56) References JP-A-5-296922 (JP, A) Cl ^6, DB name) G01N 21/00 -. 21/01 G01N 21/17 - 21/61 G01N 33/497 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. Carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO 2
_In the isotope gas spectrometry method of measuring the concentration of the component gas by guiding the gas to be measured containing ₂ as a component gas to the cell, measuring the amount of transmitted light having a wavelength suitable for each component gas and processing the data, It is created by measuring a 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 Of the measured gas using the calibration curve
Determine the concentration of ¹² CO ₂ and ¹³ CO _2, ¹² CO ₂ and ¹³ CO ₂
A second step of obtaining the concentration ratio between, as well as ¹² CO ₂ and ¹³
Concentration ratio of the concentration of CO ₂ and ¹² CO ₂ and ¹³ CO ₂ is known
Using the correction curve prepared by measuring the gas, characterized in that it comprises a third step of correcting the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ in accordance with the concentration of ¹² CO ₂ Isotope gas spectrometry method. 2. The correction line in the third step is ¹² CO
Concentration ratio of ₂ and ¹³ CO ₂ concentrations and ¹² CO ₂ and ¹³ CO ₂ for a known gas, obtains the absorbance corresponding to the wavelength of the ¹² CO ₂ and ¹³ CO _2, by using the calibration curve ¹² CO ₂ and ¹³ CO ₂ concentrations and ¹² CO ₂ and determine the concentration ratio between ¹³ CO _2, and ¹² CO ₂ concentrations obtained, ¹² CO ₂ and ¹³ CO
Obtained by plotting the concentration ratio of _2, the correction method in the third step, the ¹² CO ₂ by fitting the concentration of ¹² CO ₂ obtained in the second step for the gas to be measured to the correction line ^A correction value of the concentration ratio of ¹³ CO ₂ was obtained, and the concentration ratio of ¹² CO ₂ and ¹³ CO ₂ obtained in the second step was calculated as
2. The method according to claim 1, wherein the value is divided by the concentration ratio correction value obtained from a correction line. 3. A correction line in the third step, the concentration ratio of the relationship between the ¹² CO ₂ concentrations and the ¹² CO ₂ and ¹³ CO ₂ obtained, the obtained approximated by fourth order curve The isotope gas spectrometry method according to claim 2, characterized in that: 4. Carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO
_The gas to be measured containing ₂ as a component gas is led to a cell, the amount of transmitted light having a wavelength stored in each component gas is measured, and the measured light amount is subjected to data processing by data processing means, whereby the concentration of the component gas is measured. in proportional gas spectroscopic measurement apparatus that measures, 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 Of the gas to be measured using
Determine the concentration of ¹² CO ₂ and ¹³ CO _2, ¹² CO ₂ and ¹³ CO ₂
Using the correction curve prepared by the concentration ratio of the concentration calculation means for calculating the concentration ratio, ¹² CO ₂ and ¹³ CO ₂ concentrations and ¹² CO ₂ and ¹³ CO ₂ and measures the known gas A concentration ratio correcting unit that corrects the concentration ratio between ¹² CO ₂ and ¹³ CO ₂ determined by the concentration calculating unit according to the concentration of ¹² CO ₂ determined by the concentration calculating unit. Isotope gas spectrometer.