JPH09166546A - Isotope gas spectrometry and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method, by which in the case of introducing gas to be measured containing plural component gases to a cell to perform spectrometry, the influence of the fluctuation with time of a measurement system can be reduced, and by which the concentration of component gas can be measured precisely. SOLUTION: A process of filling cells 11a, 11b with reference gas to measure the quantity of light and a process of filling the cells 11a, 11b with gas to be measured to measure the quantity of light are alternately performed. Thus, the absorbance is obtained from of the quantity of light obtained by filling the gas to be measured and the average value of the quantities of light obtained by filling reference gas before and after filling the gas to be measured. At this time, the time fluctuation before and after the measurement of gas to be measured can be corrected by obtaining the average value of quantities of light of reference gas, so that it is possible to remove the influence of the charge with passage of time of a measurement system.

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 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]

The concentration of CO ₂ , especially ¹³
Since the concentration of CO ₂ is very low, highly sensitive measurement must be performed. However, if the measurement sensitivity is increased, if there are fluctuations in various constants of the measurement system, such as fluctuations in the intensity of the light source, fluctuations in the temperature of the gas itself, fluctuations in the temperature of the cell that introduces the gas, fluctuations in the sensitivity of the photodetector, etc. The amount of light measured also reacts sensitively,
There is a problem that an error occurs in the measured value due to factors other than the actual measured gas.

In order to solve the above-mentioned problem, it may be possible to start the measurement after allowing a sufficient time for the measurement system to settle down. However, in this case, the processing capacity is lowered and a large amount of sample is collected in a short time. The user's request for measurement cannot be met. In addition, in the measurement, the absorbance of ¹² CO ₂ was measured for one type of exhaled gas to obtain ¹² CO 2.
Using a calibration curve for ₂ to calculate the ¹² CO ₂ concentration, ¹³ CO ₂
Absorbance of ¹³ C is measured using a calibration curve for ¹³ CO ₂ .
Calculate the O ₂ concentration. Similar measurements are made for other types of exhaled breath.

At this time, if the CO ₂ concentrations are almost the same for the two kinds of exhaled breath, the range of using the calibration curve of ¹² CO _{2 or} the calibration curve of ¹³ CO ₂ can be narrowed. Therefore,
The measurement accuracy can be improved by limiting the range in which the calibration curve is used. Therefore, the present invention solves the above-mentioned technical problems, introduces a measured gas containing a plurality of component gases into a cell, and when performing spectroscopic measurement, it is possible to reduce the influence of time variation of the measurement system, An object of the present invention is to realize an isotope gas spectroscopic measurement method and a measurement device capable of accurately measuring the concentration of a component gas.

Further, according to 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 range of using the calibration curve is limited to precisely measure the concentration of the component gas. It is an object of the present invention to realize an isotope gas spectroscopic measurement method that can be performed.

[0011]

The isotope gas spectroscopic measurement method according to claim 1 for achieving the above object, comprises the steps of filling a cell with a reference gas and measuring the amount of light, and measuring gas in the cell. Alternately performing the step of measuring the light amount by satisfying, the light amount of the light obtained by filling the gas to be measured, before and after, the method of obtaining the absorbance from the average value of the light amount of the light obtained by filling the reference gas Is.

[0012] Usually, the absorbance is measured by performing the steps of filling the reference gas and measuring the amount of light and the step of filling the cell with the gas to be measured and measuring the amount of light once to obtain the absorbance. According to the method of the present invention, the absorbance is obtained from the amount of light obtained by filling the gas to be measured and the average value of the amount of light obtained by filling the reference gas before and after that.

Thus, the time variation before and after the measurement of the gas to be measured can be corrected by taking the average value of the light amount of the reference gas, and the influence of the aging of the measurement system can be removed. The measurement result of the reference gas after the measurement of the gas to be measured is also the measurement result of the reference gas before the measurement of the next gas to be measured. You can

Further, in the isotope gas spectroscopic measurement method according to the second aspect, the average value of the light quantity of light obtained by filling the reference gas and the light quantity of light obtained before and after filling the same gas to be measured. Determine the absorbance from and. In this method, since the same measured gas must be measured twice, the efficiency is lowered, but this method also takes the average value of the light amount of the measured gas as the time variation before and after the measurement of the measured gas. Therefore, it is possible to correct it, and it is possible to remove the influence of the change with time of the measurement system.

Further, the isotope gas spectroscopic measurement apparatus according to claim 4 relates to the same invention as the isotope gas spectroscopic measurement method according to claim 1, and the isotope gas spectroscopic measurement apparatus according to claim 5 is the same. The present invention relates to the same invention as the method for measuring isotope gas spectroscopy according to claim 2. The plurality of component gases may be carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO ₂ .

Further, in the isotope gas spectroscopic measurement method according to the seventh aspect, for two kinds of measured gases collected from one specimen, the CO ₂ concentration of one measured gas is the CO ₂ concentration of the other measured gas. _If it is higher than ₂ concentration, one of the measured gases is diluted until the CO ₂ concentration of the one measured gas becomes equal to the CO ₂ concentration of the other measured gas, and the concentration ratio of each measured gas is ¹³ CO. a method of measuring ^_2/12 CO _2.

According to this method, two kinds of exhaled air can be measured under the condition that the CO ₂ concentrations are equal, so that the range of the calibration curve to be used can be limited.
As a result, measurement accuracy can be improved. The method according to claim 8 or 9, wherein a single cell is filled with the gas to be measured of the first type to measure the amount of light, and after discharging, the second cell is discharged.
The specific procedure of the isotope gas spectroscopic measurement method according to claim 7, which is premised on filling a kind of gas to be measured and measuring the light amount.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, after a urea diagnostic agent marked with isotope ¹³ C is administered to humans, ¹³ CO _{2 in} exhaled breath
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, for example, nitrogen gas) is supplied from a 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.

[0021] While the divided from way valve V ₃ leads to the three-way valve V _1, and the other thereof is connected to the first sample cell 11a for measuring the absorption of ¹² CO _2.
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 piston is driven by a motor (not shown), a feed screw connected to the motor, and a nut fixed to the piston. Done by

As shown in FIG. 1, the cell chamber 11 contains ¹² CO 2.
Short first sample cell 11 for measuring the absorption of ₂
a, comprising a long second sample cell 11b for measuring the absorption of ¹³ CO ₂ and a reference cell 11c for flowing a reference gas, the first sample cell 11a and the second sample cell 11b are in communication with each other, Cell 1
The gas led to the first sample cell 11a
b and is exhausted. 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 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 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 the 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 heaters 13 installed 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. IIIa. Measurement Procedure 1 Measurement is performed in the order of reference gas measurement → base gas measurement → reference gas measurement → sample gas measurement → reference gas measurement → .... However, in addition to this procedure, 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 cell 11c. IIIa-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 . IIIa-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 by 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. IIIa-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. IIIa-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. IIIa-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).

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

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

In this measurement, if the CO ₂ concentration of the pre-measured base gas is C of the pre-measured sample gas
If it is lower than the O ₂ concentration, the concentration of the base gas is measured as it is, and the CO ₂ concentration of the sample gas is
After diluting the sample gas until the concentration becomes equal to ₂ , the CO ₂ concentration of the sample gas is measured. The measurement is performed in the following procedure: base gas preliminary measurement → sample gas preliminary measurement → reference gas measurement → base gas measurement → reference gas measurement → sample gas measurement → reference gas measurement →. IIIb-1. Base gas preliminary measurement In the gas channel and cell chamber 11 of the isotope gas spectrometer,
Gas flow path and cell chamber 1 by flowing a clean reference gas
While cleaning No. 1, the reference light amount is measured.

Next, the base gas is sucked from the breath bag by the gas injector 21, and the base gas is mechanically pushed out at a constant flow rate using the gas injector 21. During this period, the detection element 2
The light amount of the base gas is measured by 5a, and the CO ₂ concentration is obtained from the absorbance using a calibration curve. IIIb-2. Preliminary measurement of sample gas In the gas channel and cell chamber 11 of the isotope gas spectrometer,
Gas flow path and cell chamber 1 by flowing a clean reference gas
While cleaning No. 1, the reference light amount is measured.

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

[0038] In this manner, the light quantity of ¹² R ₁ obtained by the first detection element 25a, the amount of light obtained by the second detection element 25b are the ¹³ R _1. IIIb-4. Base gas measurement CO ₂ concentration of the base gas obtained by the first detection element 25a in “IIIb-1. Preliminary measurement of base gas” and “II
Ib-2. Comparing the CO ₂ concentration of the sample gas obtained by the first detection element 25a in a sample gas preliminary measurement ", when CO ₂ concentration of the base gas is darker than the CO ₂ concentration of the sample gas, in the gas injector 21 And base gas C
After diluting the base gas with the reference gas until the O ₂ concentration becomes equal to the CO ₂ concentration of the sample gas,
Measure the light quantity of the base gas.

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

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

Thus, 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 will be described. IIIb-6. Sample gas measurement If the base gas was diluted in “IIIb-4. Base gas measurement”, inhale the sample gas from the exhalation bag and then
The sample gas is mechanically extruded at a constant flow rate using the gas injector 21, and during this period, the detection elements 25a, 2
The light amount is measured by 5b.

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

In this way, the first detection element 25a
Amount of light obtained¹²R_Three, Obtained with the second detection element 25b
Light intensity¹³R_ThreeWrite IV. Data processing IV-1. Calculation of Absorbance of Base Gas First, the reference obtained in the above measurement procedure 1 or measurement procedure 2 was used.
Lens gas transmitted light amount ¹²R₁,¹³R₁, Base gas permeability
Light intensity¹²B,¹³B, amount of transmitted light of reference gas
¹²R_Two,¹³R_TwoIn the base gas¹²CO_Two
Absorbance of¹²Abs (B),¹³CO_TwoAbsorbance of¹³Abs (B)
Ask for.

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

IIIa. As mentioned at the beginning of
Gas measurement → Reference gas measurement → Base gas measurement → Support
Sample gas measurement → Reference gas measurement → Sample gas
If the procedure of measurement ... is adopted, the
¹²CO_Two Absorbance of¹²Abs (B) is¹² Abs (B) = -log [(¹²B₁+¹²B_Two ) / 2¹²R]¹³CO_Two Absorbance of¹³Abs (B) is¹³ Abs (B) = -log [(¹³B₁ +¹³B_Two) / 2¹³R]. Where R is the permeation of the reference gas
Light intensity, B₁, B_TwoIs the reference gas measurement
It is the amount of transmitted light of the base gas before and after. IV-2. Calculation of absorbance of sample gas Next, refer to the measurement procedure 1 or the measurement procedure 2 described above.
Lens gas transmitted light amount ¹²R_Two,¹³R_TwoOf the sample gas
Amount of transmitted light¹²S,¹³S, amount of transmitted reference gas¹²R
_Three,¹³R_Three In the sample gas¹²CO_Two of
Absorbance¹²Abs (S),¹³CO_Two Absorbance of¹³Abs (S)
Ask.

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

In this way, when calculating the absorbance, 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, IIIa. 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 created by using the measured gas whose ¹² CO ₂ concentration is known and the measured gas whose ¹³ CO ₂ concentration is known. To obtain a calibration curve, the ¹³ CO ₂ absorbance is measured while varying the ¹² CO ₂ concentration within the range of 0% to 6%. 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 ¹³ CO ₂ concentration 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 and} the absorption spectrum of ¹³ CO ₂ partially overlap. In this measurement,
^Since a gas in which ¹² CO ₂ and ¹³ CO ₂ are mixed is to be measured, it is necessary to correct the overlap when determining a calibration curve. In this measurement, a calibration curve in which the overlap of the absorption spectra is partially corrected is actually used.

The base gas obtained 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_Two When¹²CO_Two The concentration ratio is determined. For base gas
Concentration ratio¹³ Conc (B) /¹²Conc (B) The concentration ratio in the sample gas is¹³ Conc (S) /¹²Required by Conc (S).

The concentration ratio 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. ¹³ C ¹³ C variation in comparing the variation of the determined sample gas and the base gas is obtained by the following expression.

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

[0055]

[Examples] ¹² CO ₂ concentration was measured a plurality of times with the same isotope gas spectrophotometer for the same gas to be measured containing carbon dioxide gas (CO ₂ concentration was naturally the same). Device startup 1
After a lapse of time, sample gas measurement was performed 10 times in the order of reference gas measurement → sample gas measurement → reference gas measurement → sample gas measurement → reference gas measurement → .... Method A of the present invention for obtaining the absorbance of the sample gas based on the average value of the reference gas measured values before and after the measurement of the sample gas, and a method for obtaining the absorbance of the sample gas based on the measured value of the reference gas only before the measurement of the sample gas The concentration was obtained from B and.

The results of calculating the concentration by the method A are shown in Table 1.
Shown in In Table 1, the concentration measured at the first time is set to 1, and the concentrations obtained after the second time are standardized. In method A, the standard deviation of the calculated concentration data was 0.0009.

[0057]

[Table 1]

The results of calculating the concentration by the method B are shown in Table 2.
Shown in Also in Table 2, the density measured in the first time is set to 1 and the density obtained after the second time is normalized. In method B, the standard deviation of the concentration data was 0.0013.

[0059]

[Table 2]

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

[0061]

As described above, according to the present invention as set forth in claim 1 or 4, the light quantity of light obtained by filling the gas to be measured and the light quantity of light obtained by filling the reference gas before and after that are obtained. Since the absorbance is calculated from the average value, the time variation before and after the measurement of the gas to be measured can be corrected by taking the average value of the light amount of the reference gas, and the effect of changes over time in the measurement system can be eliminated. it can. Also,
The measurement result of the reference gas after measuring the measured gas is
Since it also becomes the measurement result of the reference gas before the measurement of the next gas to be measured, the measurement result of the reference gas at one time can be utilized twice, and the efficiency can be improved.

According to the present invention of claim 2 or 5, the amount of light obtained by filling the reference gas with
Before and after that, since the absorbance is obtained from the average value of the light intensity of the light obtained by filling the measured gas, the time variation before and after measurement of the measured gas is calculated by taking the average value of the light intensity of the measured gas. It can be corrected and the influence of aging of the measurement system can be removed.

Further, according to the present invention as set forth in claim 7, 8 or 9, the CO ₂ concentration can be made substantially the same for the two kinds of measured gases. Therefore, a calibration curve of ¹² CO _{2 or} a calibration curve of ¹³ CO ₂ can be obtained. The range of using can be narrowed. As the calibration curve has a narrower range, a higher accuracy can be obtained. Therefore, by limiting the range in which the calibration curve is used, measurement accuracy can be improved.

[Brief description of the drawings]

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

FIG. 2 is a 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.

[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 front page (72) Inventor Yasushi Hamao 1-42, Chuo, Kosai-cho, Koga-gun, Shiga (72) Inventor Eiji Ikegami 112, Tomeizaka, Mizuguchi-cho, Koga-gun, Shiga (72) Inventor Kazunori Tsutsui, Shiga 38, 670 Mizuguchi, Mizuguchi-cho, Koka-gun

Claims (9)

[Claims] 1. A measurement gas containing a plurality of component gases is introduced into a cell, the absorbance of transmitted light having a wavelength suitable for each component gas is obtained, and the measurement gas containing a component gas of a known concentration is measured. Using the created calibration curve, in the isotope gas spectroscopic measurement method for measuring the concentration of each component gas, the step of filling the cell with a reference gas and measuring the light amount, and dropping the gas to be measured into the cell. The process of alternately measuring the light intensity is performed alternately, and the absorbance is calculated from the light intensity of the light obtained by filling the gas to be measured and the average value of the light intensity of the light obtained by filling the reference gas before and after that. And isotope gas spectroscopic measurement method. 2. A measurement gas containing a plurality of component gases is introduced into a cell, the absorbance of transmitted light having a wavelength suitable for each component gas is determined, and the measurement gas containing a component gas having a known concentration is measured. Using the created calibration curve, in the isotope gas spectroscopic measurement method for measuring the concentration of each component gas, the step of measuring the light amount by filling the cell with the reference gas, and the light amount by filling the cell with his measurement gas It is characterized by alternately performing the process of measuring and the light intensity of the light obtained by filling the reference gas and the average value of the light intensity of the light obtained by filling the same gas to be measured before and after that. And isotope gas spectroscopic measurement method. 3. 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 . 4. A measurement target gas containing a plurality of component gases is introduced into a cell, the amount of transmitted light having a wavelength suitable for 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, with respect to the measured gas and the reference gas introduced into the cell, the light amount of the light corresponding to the wavelength suitable for each component gas is alternated. Light amount measuring means to measure, the light amount of light obtained by filling the reference gas, and the absorbance calculation means for obtaining the absorbance from the average value of the light amount of the light obtained by filling the measured gas before and after that, and the known concentration Isotope gas, which comprises a concentration calculating means for obtaining the concentration of the component gas by using a calibration curve created by measuring the measured gas containing the component gas of Light measurement device. 5. A measurement gas containing a plurality of component gases is introduced into a cell, the amount of transmitted light having a wavelength suitable for 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, with respect to the measured gas and the reference gas introduced into the cell, the light amount of the light corresponding to the wavelength suitable for each component gas is alternated. A light quantity measuring means for measuring, a light quantity of light obtained by filling the gas to be measured, and an absorbance calculating means for obtaining the absorbance from the average value of the light quantity of the light obtained by filling the reference gas before and after, and a known concentration Isotope gas, which comprises a concentration calculating means for obtaining the concentration of the component gas by using a calibration curve created by measuring the measured gas containing the component gas of Light measurement device. 6. A plurality of component gases are carbon dioxide ¹² CO
_2. The isotope gas spectroscopic measurement device according to claim 4, which is ₂ and carbon dioxide ¹³ CO ₂ . 7. Carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO ₂
Guide the gas to be measured containing and as component gas to the cell, obtain the absorbance of the transmitted light of the wavelength suitable for each component gas, and use the calibration curve created by measuring the gas containing the component gas of known concentration In the isotope gas spectroscopic measurement method for measuring the concentration of each component gas, the CO ₂ concentration of one measured gas is the CO ₂ concentration of the other measured gas of two kinds of measured gases collected from one sample. _If it is higher than ₂ concentration, one of the measured gases is diluted until the CO ₂ concentration of the one measured gas becomes equal to the CO ₂ concentration of the other measured gas, and the concentration ratio of each measured gas is ¹³ CO. ^_2/12 CO ₂ isotope gas spectroscopic measurement method for measuring. 8. Carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO ₂
Using a calibration curve created by introducing a gas to be measured containing component gas into the cell, determining the absorbance of transmitted light having a wavelength suitable for each component gas, and measuring a gas containing a component gas having a known concentration. In the isotope gas spectrometry for measuring the concentration of each component gas, in the preliminary measurement, (a)
The two types of measurement gas collected from one sample, and the CO ₂ concentration of the first type of the gas to be measured, the CO ₂ concentration of the second type of gas to be measured were measured, in the measurement, (b ) is higher than the measured CO ₂ concentration of the second type of the measurement gas CO ₂ concentration of the first type of the measurement gas is measured are, the CO ₂ concentration of the first type of measurement gas second after dilution of the gas to be measured of the first type to be equal to the CO ₂ concentration of the types of the measurement gas by measuring the concentration ratio ¹³ CO ^_2/12 CO ₂ in the first type of the gas to be measured, the (c) two proportional gas spectroscopic measurement method for measuring the concentration ratio ¹³ CO ^_2/12 CO ₂ in the measurement gas. 9. Carbon dioxide¹²CO_TwoAnd carbon dioxide¹³CO_Two
The gas to be measured, which contains
Determine the absorbance of transmitted light of a wavelength suitable for the
Created by measuring gas containing component gases
Using the calibrated calibration curve to measure the concentration of each component gas
In the body gas spectrometry method, in the preliminary measurement, (a)
For two types of gas to be measured collected from one sample,
Of the first type gas to be measured_TwoConcentration and the second type
CO of measured gas_TwoMeasure each concentration, and
And (b) the CO of the measured first type gas to be measured._TwoDark
Of the second type gas to be measured whose degree is measured_TwoThan concentration
Is lower, the concentration ratio of the first type gas to be measured¹³CO_Two/
¹²CO_TwoIs measured as it is, and (c) the second type of gas to be measured
CO_TwoThe concentration of CO in the gas to be measured of the first type_TwoConcentration etc.
After diluting the second kind of gas to be measured until
Concentration ratio of different types of measured gas¹³CO_Two/¹²CO_TwoTo measure
Isotope gas spectroscopic measurement method.