JPH11230896A - Gas cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas cell which can reduce a quantity of a sample gas to be consumed when a gas in a main body is substituted with the sample gas, can be simplified in constitution and improve a substitution speed. SOLUTION: The gas cell has a main body 137 for storing a sample gas, an introduction hole 137 through which the sample gas is introduced into the main body 137, an exit hole 137b through which the gas in the main body 137 is guided outside, and a substitution means 138 which can forcibly discharge the gas in the main body 137 outside through the exit hole 137b and can suck forcibly the sample gas from the introduction hole 137a into the main body 137.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas cell, and more particularly to an improvement in a mechanism for introducing a sample gas.

[0002]

2. Description of the Related Art Conventionally, many patients with dyspepsia secondary to peptic ulcer complaining of symptoms such as dyspepsia and gastritis and patients with non-ulcer dyspepsia are infected with Helicobacter pylori. Is known to be. Helicobacter pylori has been confirmed in and inside the gastric mucosa of infected persons, and endoscopy and biopsy of the stomach had to be performed in order to examine the presence or absence of the infection. However,
In the endoscopy and biopsy of the stomach, it was difficult to perform a measurement for quantifying Helicobacter pylori infection.

[0003] Therefore, the presence or absence of Helicobacter pylori, which is considered to be present in or near the stomach of an infected person, and the status of the infection can be easily grasped, and the human body is not damaged during the test. The development of testing methods has been strongly desired in this type of field. A breath test method can be considered to meet such a demand. This breath test is ¹³
After administering and consuming urea labeled with CO ₂ to a subject, breath is collected from the subject and analyzed to determine whether or not the stomach or Helicobacter pylori in the vicinity of the stomach is infected and the status of the infection. It is to be measured.

That is, when urea labeled with ¹³ CO ₂ is administered to an infected person, Helicobacter pylori existing in the stomach and its vicinity decomposes the administered urea into carbon dioxide and ammonia. Therefore, this breath test method analyzes the carbon dioxide in the breath of a subject before administration of urea labeled with ¹³ CO ₂ and after the administration and consumption of the urea using an infrared spectrophotometer, and compares the results. ¹³ for total CO ₂ or ¹² CO ₂ of infected person
Since the CO ₂ abundance ratio is increasing, this increase is measured to determine the presence or absence of Helicobacter pylori infection and the status of the infection. FIG. 1 shows such an infrared spectrophotometer. Infrared spectrophotometer 10 shown in FIG.
, The infrared light beam L ₁ emitted from the light source 12 passes through the gas cell 16 and enters the detectors 18 and 19.

Here, the amount of the infrared light beam L _{2 in} the ¹² CO ₂ absorption band reaching the detector 18 changes in accordance with the concentration of ¹² CO ₂ in the breath introduced into the gas cell 16, and is proportional to the amount of light. The signal is taken as the output of detector 18. Also,
¹³ CO quantity of the infrared light beam L ₃ of ₂ corresponds to the concentration reaches the detector 19 ¹³ CO ₂ absorption band is changed, the signal proportional to the quantity of light is taken out as the output of the detector 19. These signals are subjected to arithmetic processing by control means such as the CPU 20 and CO
For ₂ whole or ¹² CO ₂ was measured abundance ratio of ¹³ CO _2.

[0006] Then, by measuring the ¹³ CO ₂ presence ratio before and after the administration administration of urea labeled with to ¹³ CO ₂ as described above, ¹³ CO ₂ abundance after administration, prior to administration ¹³ CO _{2 If the} ratio was higher than the abundance ratio, it was determined that Helicobacter pylori infection was present. By the way, the structure of the gas cell 16 having the conventional configuration is fixed, and the inside of the gas cell 16 is washed with the dry nitrogen gas in the nitrogen container 22 before introducing the sample gas. After the cleaning, the sample gas was allowed to flow into the gas cell 16 over a long period of time, and the dry nitrogen gas and the like in the gas cell 16 were replaced with the sample gas.

More specifically, the sample gas in the sample container 26 is sucked in by the syringe type gas replacement device 24 through the pipes 28, 30 and 32, and the sample gas is exhausted to thereby discharge the pipe 3.
It has been general that the sample gas flows into the gas cell 16 through the ports 2 and 34. Here, the syringe-type gas replacement device 24 sucks the sample gas and pushes the sample gas into the gas cell 16 at a flow rate of about half or less of the time of the suction. The data output from the detector 18 was integrated by the CPU 20 after being stabilized.

[0008]

However, in the infrared spectrophotometer 10 having the conventional structure, the structure of the gas cell 16 is fixed, and only the sample gas is introduced into the gas cell 16 so that, for example, Since the dry nitrogen gas was replaced by the sample gas, when the dry nitrogen gas in the gas cell 16 was replaced by the sample gas, the concentration was changed only gradually, and there was still room for improvement in the replacement speed.

Further, the infrared spectrophotometer 1 having the above-mentioned conventional configuration is used.
At 0, when replacing the dry nitrogen gas or the like in the gas cell 16 with the sample gas, the sample gas was sucked by the syringe-type gas replacement device 24. This was pushed into the gas cell 16 at a flow rate of about half or less of the suction time, but the data output by the detector 18 is integrated only for a few seconds after stabilization.

[0010] Accordingly, only a very small amount of the sample gas used contributes to the measurement, which is not satisfactory in terms of effective use of the sample. In particular, this problem was more serious for a sample gas such as exhaled gas, for which it is difficult to secure a sufficient amount.

Therefore, as a technique for solving such a problem, a technique for evacuating dry nitrogen gas or the like in the gas cell 16 is conceivable, but the syringe type gas replacement device 24 has such an evacuating function. I do not have
In the infrared spectrophotometer 10 having the conventional configuration, the suction means 36 such as a vacuum pump had to be separately provided.

However, if the suction means 36 such as a vacuum pump is separately provided only for evacuating the dry nitrogen gas or the like in the gas cell 16, a new problem that the structure of the apparatus becomes complicated arises. In this type of field, when dry nitrogen gas or the like in a gas cell is replaced with a sample gas, a technique capable of reducing the consumption of the sample gas and improving the replacement speed while simplifying the configuration. The development of was strongly desired. Further, in the infrared spectrophotometer 10 having the above-described conventional configuration, the measured values obtained by the detector 18 vary, and there is still room for improvement in the measurement accuracy. Was not done.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to reduce the consumption of a sample gas when replacing the gas in the gas cell with the sample gas, and to simplify the configuration thereof. Another object of the present invention is to provide a gas cell that can improve the replacement speed while achieving the above.

[0014]

In order to achieve the above object, a gas cell according to the present invention is characterized by comprising a main body, an inlet, an outlet, and one replacement means. The body contains the sample gas. The introduction hole is for introducing a sample gas into the main body. The outlet hole is for leading the gas in the main body to the outside. The replacement means is capable of forcibly exhausting gas in the main body to the outside from the outlet hole, and capable of forcibly sucking a sample gas into the main body from the introduction hole. is there.

In the gas cell, the replacement means includes a piston provided on the inner peripheral surface of the main body so as to be slidable in the direction of the introduction hole or the extraction hole, and the piston is interposed between the piston and the piston. It is possible to allow the gas in the main body to flow from the inlet hole side to the outlet hole side, but it is preferable to provide a check valve for preventing the gas from flowing from the outlet hole side to the inlet hole side.

Further, in the gas cell, the replacement means is provided in the introduction hole, wherein the sample gas flows into the main body from the introduction hole in an open state, and from the introduction hole in a closed state. A valve capable of preventing sample gas from flowing into the main body, and a suction means provided in the outlet hole and capable of suctioning gas in the main body,
By closing the valve and forcibly exhausting the gas in the main body to the outside by the suction means, the inside of the main body is brought into a negative pressure state, and the valve is opened in this state. It is preferable that the sample gas is forcibly sucked into the main body.

Further, in the gas cell, the main body is provided with an outside air intake / exhaust hole, and the replacing means is provided inside the main body with two sides of the introduction hole and the outlet hole and the outside air intake / exhaust hole. It is preferable to include a film-like elastic body to be divided. In addition, the present inventors have conducted intensive studies on the causes of the variation in the measured values, and as a result, have found that the variation in the measured values can be significantly reduced by keeping the flow rate of the sample gas flowing in the gas cell constant. They have found and completed the present invention.

That is, in the gas cell, when the sample gas is introduced into the main body, the valve is closed, and the gas in the main body is exhausted by the suction means so that the inside of the main body has a negative pressure. In this state, the sample gas is forcibly sucked into the main body by opening the valve in this state, and when detecting the light transmitted through the main body, the sample gas keeps the inside of the main body constant. It is preferable to provide a control means for appropriately controlling the suction force of the suction means so as to flow at the speed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a schematic configuration of an infrared spectrophotometer using a gas cell according to one embodiment of the present invention. In the present embodiment, a case will be described in which ¹³ CO ₂ abundance ratio in breath is measured using human breath as a sample gas, and the presence or absence of Helicobacter infection is determined based on the measurement result. Also, portions corresponding to those in FIG. 1 are denoted by reference numeral 100, and description thereof is omitted. The infrared spectrophotometer 110 shown in FIG.
, Detectors 118 and 119 and a CPU 120.

The infrared light beam L ₁ emitted from the light source 112 passes through the gas cell 116 and enters the detectors 118 and 119.
Here, ¹² CO _{2 in the} exhaled gas introduced into the gas cell 116.
Amount of the infrared light beam L ₂ of the ¹² CO ₂ absorption band reaching the detector 118 corresponding to the concentration is changed, the signal proportional to the quantity of light is taken out as the output of the detector 118. Also, ¹³ C
Amount of the infrared light beam L ₃ of O ₂ corresponding to the concentration reaches the detector 119 ¹³ CO ₂ absorption band is changed, the signal proportional to the quantity of light is taken out as the output of the detector 119. These signals are subjected to arithmetic processing by control means such as the CPU 120, and C
For O ₂ all or ¹² CO ₂ was measured abundance ratio of ¹³ CO _2. Then, by measuring the ¹³ CO ₂ abundance after before and administration administration of urea labeled with the to ¹³ CO ₂ as described above, ¹³ CO ₂ abundance after administration, ¹³ CO ₂ abundance before administration If it was higher than that of, this was judged as having Helicobacter pylori infection.

The present invention is characterized in that the gas in the main body can be forcibly exhausted to the outside from the outlet hole, and the sample gas is forcibly sucked into the main body from the inlet hole. Is provided with one possible replacement means.
For this reason, in this embodiment, the gas cell 116
As shown in (1), a main body 137, an introduction hole 137a, an outlet hole 137b, and a replacement unit are provided.

The main body 137 contains a sample gas such as exhaled gas. The introduction hole 137a is for introducing a sample gas into the main body 137. The lead-out hole 137b is provided in the main body 13
This is for leading the gas inside 7 to the outside.

In this embodiment, the replacement means is the main body 13
7 includes a piston 138 slidably provided on the inner peripheral surface, and the piston 138 is slid in the left-right direction in the figure by a rod 140. The piston 138 is provided with a communication hole 141 so that the left chamber 142 and the right chamber 143 of the main body 137 can be temporarily communicated with the piston 138 interposed therebetween. That is, a check valve 144 is provided in the communication hole 141, and when the check valve 144 is open, the left chamber 142
Can flow into the right chamber 143 through the communication hole 141, but the gas in the right chamber 143 is prevented from flowing into the left chamber 142.

A valve 145 is provided in the introduction hole 137a, and the sample gas is supplied to the main body 137 by the valve 145.
Although it is possible to flow into the inside, the gas in the main body 137 is prevented from flowing backward from the introduction hole to the outside. By sliding the piston 138 a plurality of times in the left-right direction in FIG.
7b can be forcibly exhausted to the outside, and the sample gas can be forcibly exhausted from the introduction hole 137a through the valve 144 to the main body 137.
The air can be forcibly sucked in.

In the present embodiment, the left side surface 146 of the main body 137 is used as an entrance window and an exit window, and the surface 138a of the piston 138 on the left chamber 142 side may reflect incident light in the incident direction. A mirror surface is provided so that it can be used. Therefore, the light L1 is emitted from the left side surface 146 of the main body 137.
Further, the light enters the gas cell 116 and is irradiated on the sample gas in the main body 137. The light L1 that has passed through the sample gas is first reflected in the incident direction on the surface 138a of the piston 138, and is emitted again from the left side surface 146 to the outside of the main body 137.
The light enters the detectors 118 and 119 shown in FIG.

The infrared spectrophotometer 110 using the gas cell 116 according to this embodiment is configured as described above, and its operation will be described below. First, the valve 145 is opened as shown in FIG.
Is moved from the left side to the right side in FIG. here,
The check valve 144 is closed, and the right chamber 14 of the main body 137 is closed.
The dry nitrogen gas and the like in 3 are forcibly scavenged to the outside through the outlet 137b, and the sample gas is introduced into the left chamber 142 of the main body 137 through the inlet 137a through the valve 145.

On the other hand, as shown in FIG.
45 is closed, and the piston 138 is moved by the rod 140 from the right to the left in the figure. Here, the check valve 144
Is naturally opened, and the sample gas in the left chamber 142 of the main body 137 flows into the right chamber 143 through the communication hole 141 of the piston 138. In this way, the piston 138
Can be forcibly scavenged dry nitrogen gas and the like in the main body 137 to the outside by only sliding the rod a plurality of times in the left and right direction in FIG. can do.

As a result, as compared with the conventional cell structure in which the dry nitrogen gas is replaced by the sample gas only by introducing the sample gas into the gas cell, the gas cell 116 is more efficient. For example, the dry nitrogen gas or the like can be replaced with a sample gas. As a result, the replacement speed can be improved, and the amount of sample consumed before the inside of the gas cell 116 is replaced with a sample gas such as dry nitrogen gas can be greatly reduced.

Further, the dry nitrogen gas or the like in the main body 137 can be forcibly discharged to the outside only by the piston 138, which is substantially one replacement means, and the main body 137
Since the sample gas can be forcibly introduced into the chamber, a vacuum pump etc. for discharging the gas inside the main body to the outside and a cylinder type gas replacement device etc. for introducing the sample gas into the main body are separately provided. The configuration can be simplified as compared with the configuration provided in the first embodiment. The valve 145 and the piston 1
Each operation of 38 is controlled by the CPU 120.
As a result, effects such as high speed, accuracy, and easy operation can be obtained as compared with those in which each operation of the valve 145 and the piston 138 is performed by a human operation.

Second Embodiment FIG. 4 shows a schematic configuration of an infrared spectrophotometer using a gas cell according to a second embodiment of the present invention. Note that portions corresponding to those in FIG. 2 are denoted by reference numeral 100, and description thereof is omitted. Gas cell 216 according to the second embodiment of the present invention
A suction means 258 such as a vacuum pump or a diaphragm pump capable of forcibly sucking the gas in the main body 237 is provided in the outlet hole 237b of the main body 237 with a valve 25.
9 are provided.

Then, when introducing the sample gas into the gas cell 216, the CPU 220 operates the suction means 258 with the valve 245 closed to activate the main body 237.
The inside of the gas cell 216 is brought into a negative pressure state, and the valve 245 is opened in this state to introduce the sample gas into the main body 237. Can be replaced by

As described above, according to the gas cell 216 according to the second embodiment of the present invention, similarly to the gas cell according to the first embodiment, the main body is provided by only one replacement means, in this embodiment, the suction means 258. The gas in the 237 can be forcibly discharged to the outside, and the sample gas can be forcibly sucked into the main body 237. As a result, the conventional cell structure is fixed and, for example, the dry nitrogen gas in the gas cell is efficiently replaced as compared with the gas cell in which the dry nitrogen gas is replaced by the sample gas only by introducing the sample gas into the gas cell. Nitrogen gas or the like can be replaced with a sample gas.

As a result, the replacement speed can be improved, and the amount of the sample consumed before the inside of the gas cell is replaced with a sample gas such as dry nitrogen gas can be significantly reduced. Further, the gas in the main body 237 can be forcibly discharged to the outside only by one of the replacement means, in this embodiment, the suction means 258, and the sample gas can be forcibly introduced into the main body 237. Because it is possible, body 2
Compared to those in which a vacuum pump or the like for discharging the gas in the outside 37 and a cylinder-type gas replacement device or the like for introducing the sample gas into the main body 237 are separately provided,
The configuration can be simplified.

The operations of the valve 245 and the suction means 258 are controlled by the CPU 220. As a result, it is possible to obtain effects such as high-speed operation and accurate operation facilitation as compared with those performed by human operations. The CPU 220 also controls the light L transmitted through the main body 237.
When detecting L2 and L3, the suction force of the suction means 258 is appropriately controlled so that the sample gas flows in the main body 237 at a constant speed. As a result, as compared with the case where the flow rate of the sample gas flowing in the gas cell is not taken into consideration, the variation in the measured value due to the variation in the sample gas flowing in the gas cell 216 can be largely prevented, and the measurement accuracy can be reduced. Improvement can be achieved.

Third Embodiment FIG. 5 is a schematic configuration of an infrared spectrophotometer using a gas cell according to a third embodiment of the present invention, and FIG. 6 is an enlarged view of the gas cell according to the third embodiment of the present invention. It is shown. 4 are added to the portions corresponding to those in FIG. Gas cell 31 according to a third embodiment of the present invention
6, the main body 337 is provided with one outside air intake / exhaust hole 348, an introduction hole 337a, and an outlet hole 337b as shown in FIG. Further, a film-like elastic body 354 that divides the inside of the main body 337 into a lower chamber 351 on the side of the outside air intake / exhaust hole 348 and an upper chamber 352 on the side of the inlet 337a and the outlet 337b.
(For example, a rubber balloon or the like) is provided.

The outside air intake / exhaust hole 348 is provided with a valve 349, and the outside air can be adjusted by the valve 349. Further, a nitrogen container 322 and a sample container 326 are provided in the introduction hole 337a via a valve 345. A suction means 358 such as a vacuum pump or a diaphragm pump capable of forcibly sucking gas in the upper chamber 352 of the main body 337 is provided in the outlet hole 337b.
9 are provided.

When cleaning the inside of the cell and introducing nitrogen gas, as shown in FIG. 6A, the valve 345 is closed and the upper chamber 352 of the main body 337 is moved by the suction means 358.
By sucking the gas inside, the inside of the upper chamber 352 is brought into a negative pressure state. Then, the film-like elastic body 354 is pulled inward of the main body 337, that is, upward in the drawing. Then, when the valve 349 is opened, outside air is sucked into the lower chamber 351, whereby the gas in the upper chamber 352 is satisfactorily pushed out.

Here, by flowing nitrogen gas through the valve 345, the gas in the upper chamber 352 can be replaced with nitrogen gas. Then, as the inside of the upper chamber 352 is replaced with nitrogen gas, the elastic body 354 gradually returns to its original shape as shown in FIG. It is gradually exhausted to the outside.
When the volume of the lower chamber 351 becomes minimum, the inside of the upper chamber 352 can be completely replaced with nitrogen gas.

When the sample gas is introduced, the gas in the upper chamber 352 of the main body 337 is sucked by the suction means 358 with the valve 345 closed, as shown in FIG. The inside of the chamber 352 is in a negative pressure state. Then, the film-like elastic body 354 is pulled inward of the main body 337, that is, upward in the drawing, and outside air is introduced into the lower chamber 351.

When the volume of the upper chamber 352 becomes minimum, the suction by the suction means 358 is temporarily stopped by closing the valve 359, and the sample gas is caused to flow by the valve 345. Then, the elastic body 354 gradually returns to its original shape as shown in FIG. 4B, whereby the sample gas is sucked into the upper chamber 352 and the outside air in the lower chamber 351 is exhausted to the outside through the outlet hole 348. Is done. When the volume of the lower chamber 351 becomes minimum, the inside of the upper chamber 352 can be completely filled with the sample gas. Then, the valve 345 is closed, and the suction means 358 is turned off.
After ff, measurements can be taken.

Thus, according to the gas cell 316 according to the third embodiment of the present invention, the suction means 358 is further provided.
By expanding and contracting the film-like elastic body 354, the gas in the main body 337 can be more favorably led out and the sample gas can be favorably introduced, so that compared with the gas cell 216 according to the second embodiment, Gas replacement can be performed more favorably.

As a result, as compared with a conventional cell structure in which the sample gas is replaced by a sample gas only by introducing a sample gas into the gas cell, the gas cell 316 is more efficient. For example, the dry nitrogen gas or the like can be replaced with a sample gas. Thereby, the replacement speed can be improved and the gas cell 21 can be improved.
For example, the amount of the sample consumed before the inside of the tube 6 is replaced with a sample gas such as a dry nitrogen gas can be significantly reduced.

The film-like elastic body 3 such as a rubber balloon is
The dry nitrogen gas and the like in the main body 337 can be forcibly exhausted to the outside only by using only the sample 54, and the sample gas can be forcibly sucked into the main body 337. The configuration can be simplified as compared with the case where a vacuum pump or the like for discharging and a cylinder type gas replacement device or the like for introducing a sample gas into the main body are separately provided. The valves 345, 349, 35
9 and the operation of the suction means 358 are controlled by the CPU 320. Thereby, each valve and suction means 3
58 operations are faster than human operations.
Effects such as accuracy and ease of operation can be obtained.

Further, in this embodiment, the case where one outside air intake / exhaust hole 348 is used has been described, but these may be provided separately. Note that the gas cell of the present invention is not limited to the above configuration, and various modifications are possible within the scope of the invention.

[0045] For example, but as the sample gas can be any gas, ¹² compared to the CO ₂ abundance in nature is very small, and includes a very small ¹³ CO ₂ absorbance compared to the ¹² CO _2, also Normally, for a sample gas such as exhaled gas that is not considered to be collected in a relatively large amount from the subject, when the gas in the gas cell is replaced with the sample gas, the consumption of the sample gas can be significantly reduced. It is very effective to use the gas cell of the present invention. Furthermore, in the present embodiment, various methods can be considered as a method for measuring the ¹³ CO ₂ abundance ratio. For example, the following method is given as an example.

[0046] ¹³ CO ₂ abundance ratio measurement method In the present embodiment, the CPUs 120, 220, 320
CPU 420, which is the same control means as shown in FIG.
The calibration curve creating means 460 and the approximate straight line determining means 462
When,¹³CO_TwoIt is equipped with existence ratio determination means 464, but before that
First, a normal preparation step (s1) and a measurement of a known sample are performed.
The fixed step (s2) must be performed. That is,
In the production process (s1),¹³CO_TwoStandard with known abundance
sample(¹²CO_TwoWhen¹³CO_TwoAre mixed)¹³CO_TwoExistence
Multiple ratios with different ratios¹³CO_TwoA standard sample with a known abundance
obtain.

Specifically, four 5% standard samples ( ¹³ CO ₂
Abundance ratio -24.6δ%, -9.51δ%, 12.62δ
%, The 33.1Deruta%) diluted with nitrogen gas, each of the ¹³ CO
₍₂ ) Prepare standard samples of 2%, 3%, 4% and 5% for the abundance ratio (a total of 16 samples). However, the δ% mentioned here is
For example, the ratio of ¹³ CO ₂ to ¹² CO _{2 in} arrowhead stone is set to 0
The value when δ% is used. In the present embodiment, this value was used as a standard value of the ¹³ CO ₂ abundance ratio.

After the completion of the preparation step (s1),
In the unknown sample measurement step (s2), the preparation step (s2)
¹² CO ₂ absorption band of the standard sample obtained in 1), for example, 2
The absorbance at 2290 cm ^-1 from the 390cm ^{-1 12} C
O ₂ absorbance, ¹³ CO ₂ absorption band, for example, the absorbance at 2320 cm ⁻¹ to 2220 cm ⁻¹ is measured as ¹³ CO ₂ absorbance by, for example, the infrared spectrophotometer 110 according to the first embodiment of the present invention shown in FIG. I do. Also, determine the absorbance ratio by dividing the ¹³ CO ₂ absorbance ¹² CO ₂ absorbance ⁽¹³ CO ₂ absorbance / ¹² CO ₂ absorbance).

Specifically, the abundance ratio of ¹³ CO ₂ -24.6δ%
3%, 4%, 5% of standard samples are measured in order from 2%. Then, the ¹³ CO ₂ abundance ratio -9.51 δ%, 12.6
Similarly, for 2δ% and 33.1δ%, standard samples of 3%, 4%, and 5% are measured in order from 2%. And
After the completion of the known sample measurement step (s2), the CPU 420
Starts the following arithmetic processing.

First, the calibration curve preparing means 460 calculates the ¹² CO ₂ absorbance of the standard sample obtained by the infrared spectrophotometer 110 and the ¹³ CO ₂ absorbance of the standard sample.
From the relationship of the CO ₂ absorbance, each ¹³ CO ₂ abundance ratio (−2
4.6δ%, -9.51δ%, 12.62δ%, 33.
The second approximation equation 466, which is a calibration curve for 1δ%), is determined (see FIG. 8). That is, as shown in FIG.
The results of points (4 × 4 points) are plotted on the horizontal axis (x-axis) of the graph as ¹² CO
_{2 Take the} absorbance and plot the absorbance ratio (y axis) on the vertical axis (y axis) of the graph.
¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) and plot. After completion of the plotting, the calibration curve creating means 4
60 finds a quadratic approximation 466 (y = ax ² + bx + c) for each ¹³ CO ₂ abundance (δ%).

For example, when the abundance ratio of ¹³ CO ₂ is −24.6δ%, the second approximation formula 466a (y = 0.7389 × ² −
0.5644x + 0.7086) look, ¹³ CO ₂ abundance secondary approximation formula for -9.51δ% 466b (y
= 0.7389x ² -0.5644x + 0.7131)
When the ¹³ CO ₂ abundance ratio is 12.62δ%, the quadratic approximation formula 466c (y = 0.7389x ² −0.564) is obtained.
4x + 0.7198), and the ¹³ CO ₂ abundance ratio is 33.
For 1δ%, the quadratic approximation 466d (y = 0.938)
Seek 9x ² -0.5644x + 0.7259).

Then, the quadratic approximations 466a to 466 are obtained.
After the determination of d, the approximate straight line determining means 462 compares the ¹² CO ₂ absorbance of the unknown sample obtained by the infrared spectrophotometer 110 with the second-order approximation formulas 466a to 466d, and
¹³ CO ₂ abundance in ¹² CO ₂ absorbance and absorbance ratio ⁽¹³ C
A first-order approximation straight line is determined from the relationship of (O ₂ absorbance / ¹² CO ₂ absorbance).

[0053] That is, first ¹³ CO ₂ abundance ¹² of an unknown sample
The CO ₂ absorbance and ¹³ CO ₂ absorbance determined by infrared spectrophotometer 110 according to the first embodiment of the present invention shown in FIG. 2, also by dividing by the ¹³ CO ₂ absorbance of an unknown sample ¹² CO ₂ absorbance Absorbance ratio of unknown sample ( ¹³ CO ₂ absorbance / ¹² CO ₂
Absorbance). Here, for example, ¹² CO _{2 of} an unknown sample
When absorbance is 0.2, as shown in FIG. 8 ¹² CO
₂ Draw a straight line of absorbance (x) = 0.2, and draw the straight line (x =
0.2) and the quadratic approximations 466a to 466d (P
_a, P _b, P _c, determine the P _d).

Next, the ¹³ CO ₂ abundance ratio (δ%) at each of the intersections (P _a , P _b , P _c , P _d ) is shown on the horizontal axis (x-axis) of the graph.
, The absorbance ratio at the intersections P _a , P _b , P _c , and P _d (
¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) is plotted on the vertical axis (y
Axis), a first-order approximation straight line 468 (y =
0.0003x + 0.6327) is subtracted. Then, after the creation of the primary approximate straight line 468, ¹³ CO ₂ present ratio determining unit 464 collates the absorbance ratio of the unknown sample ⁽¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) in the primary approximate line 468, ¹³ CO
₂ Determine the abundance ratio (δ%).

Here, for example, the absorbance ratio of an unknown sample ( ¹³ C
When O ₂ absorbance / ¹² CO ₂ absorbance) is 0.63, ^{1 3} CO abundance [delta]% of ₂ for ¹² CO ₂ of an unknown sample from the primary approximate straight line 468 shown in the figure obtained with -0.83Deruta% .

As described above, according to the ¹³ CO ₂ abundance ratio measuring method according to the present embodiment, the CPU 420 controls the horizontal axis (x
The ¹² CO ₂ absorbance of the standard sample was taken on the (axis), and the absorbance ratio ( ¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) of the standard sample was also taken on the vertical axis (y axis) of the graph. FIG. 8 shows the correlation between the ¹² CO ₂ absorbance and the ¹³ CO ₂ absorbance.
Can be determined.

Then, the quadratic approximations 466a to 466 are obtained.
After the determination of d, the ¹² CO ₂ absorbance of the unknown sample was calculated by the second approximation formula 4.
Reference is made to 66a to 466d, and a first approximation straight line 468 is determined from the relationship between the ¹³ CO ₂ abundance ratio and the absorbance ratio ( ¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) of the unknown sample at ¹² CO ₂ absorbance. Absorbance ratio of the unknown sample ⁽¹³ CO ₂ absorbance / ¹² CO ₂ absorbance) against this first order approximation straight line 468, ¹³ CO
_{(2) Since the} abundance ratio was determined, ¹² CO ₂ absorbance and ¹³
The ¹³ CO ₂ abundance ratio can be determined by correlating the CO ₂ absorbance. Thus, ¹² the absorption band of the absorption band and ¹³ CO ₂ in the CO ₂ is very close, some of these absorption spectra overlap, ¹² CO ₂ and ¹³ CO ₂ ¹² of exhalation are mixed CO ₂ for ¹³ CO ₂ Only the abundance ratio can be accurately measured.

[0058]

As described above, according to the gas cell of the present invention, as described above, the introduction hole for introducing the sample gas into the main body and the outlet hole for introducing the gas inside the main body to the outside. And one replacement means capable of forcibly exhausting the gas in the main body to the outside from the outlet hole and capable of forcibly sucking the sample gas into the sample cell from the introduction hole. Therefore, the gas in the main body can be forcibly exhausted to the outside from the outlet hole and the sample gas can be forcibly sucked into the main body from the inlet hole only by the replacement means. As a result, according to the gas cell according to the present invention, the conventional cell structure is fixed and compared with a gas cell in which, for example, dry nitrogen gas in the gas cell is replaced with the sample gas only by introducing the sample gas into the gas cell. For example, the dry nitrogen gas in the gas cell can be efficiently replaced with the sample gas.
Thus, according to the gas cell of the present invention, the replacement speed can be improved, and the amount of the sample consumed in the gas cell before, for example, replacing the dry nitrogen gas or the like with the sample gas can be significantly reduced. . According to the gas cell of the present invention, the gas in the main body can be forcibly discharged to the outside and the sample gas can be forcibly introduced into the main body by only one replacement means. The configuration can be simplified as compared with a case in which a vacuum pump or the like for exhausting the gas to the outside and a cylinder-type gas replacement device or the like for introducing the sample gas into the main body are separately provided. . Further, in the gas cell, the replacement means includes a piston provided on the inner peripheral surface of the main body so as to be slidable in the direction of the introduction hole or the exit hole, and the piston includes:
With the piston interposed, it is possible for the gas in the main body to flow from the introduction hole side to the discharge hole side, but by providing a check valve that prevents the gas from flowing from the discharge hole side to the introduction hole side, Forcibly exhaust the gas inside the main body to the outside from the outlet hole,
Further, the sample gas can be forcibly sucked into the main body through the introduction hole. According to the gas cell of the present invention,
The replacement means is provided in the outlet hole and uses suction means capable of forcibly sucking gas in the main body, and for example, forcing dry nitrogen gas or the like in the main body by the one suction means. By setting the inside of the main body to a negative pressure state and forcing the sample gas into the main body in this state,
For example, dry nitrogen gas or the like in the cell can be more efficiently replaced with a sample gas. Further, in the gas cell, the main body is provided with an outside air intake / exhaust hole, and the replacement means includes:
By including a film-like elastic body divided into two on the side of the outside air intake / exhaust hole, utilizing the expansion and contraction of the film-like elastic body by the suction means, the gas in the main body is more preferably evacuated,
The sample gas can be favorably introduced. According to the gas cell of the present invention, the sample gas flows into the main body from the introduction hole in the open state, and the sample gas flows into the main body from the introduction hole in the closed state. When the sample gas is introduced into the main body, the valve is closed, and the gas in the main body is exhausted by the suction means to thereby create a negative pressure in the main body. By providing control means for forcibly sucking the sample gas into the main body by opening the valve in this state, these operations are performed at a higher speed than those performed by human work. And effects such as accuracy, ease of operation, and the like. Further, when detecting the light transmitted through the main body by the control means, by controlling the suction means so that the sample gas flows at a constant speed in the main body, the sample gas flowing in the gas cell is controlled. The flow rate can be kept constant. As a result, it is possible to greatly reduce the variation in the measured value due to the variation in the flow rate of the sample flowing in the gas cell, and to improve the measurement accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a schematic configuration of a conventional infrared spectrophotometer.

FIG. 2 is an explanatory diagram of a schematic configuration of an infrared spectrophotometer using the gas cell according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of an operation of the gas cell shown in FIG.

FIG. 4 is an explanatory diagram of a schematic configuration of an infrared spectrophotometer using a gas cell according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a schematic configuration of an infrared spectrophotometer using a gas cell according to a third embodiment of the present invention.

6 is an explanatory diagram of the operation of the gas cell shown in FIG.

FIG. 7 is an explanatory diagram of a ¹³ CO ₂ abundance ratio measuring method according to an embodiment of the present invention.

FIG. 8 is an example of a second-order approximation formula obtained by the ¹³ CO ₂ abundance ratio measurement method shown in FIG. 7;

FIG. 9 is an example of a first-order approximation straight line obtained by the ¹³ CO ₂ abundance ratio measuring method shown in FIG. 7;

[Explanation of symbols]

 110 ... infrared spectrophotometer 112 ... light source 116 ... gas cell 118, 119 ... detector 120 ... CPU (control means) 137 ... body 137a ... introduction hole 137b ... outlet hole 138 ... piston (substitution means)

Claims (5)

[Claims] 1. A gas cell used for detecting characteristics of a sample gas, comprising: a main body into which the sample gas is put; an introduction hole for introducing the sample gas into the main body; A gas outlet in the main body, the gas in the main body can be forcibly exhausted to the outside from the gas outlet, and the sample gas can be forcibly sucked into the main body from the inlet. A gas cell, comprising: a possible replacement means. 2. The gas cell according to claim 1, wherein the replacement means includes a piston provided on the inner peripheral surface of the main body so as to be slidable in a direction of the inlet hole or the outlet hole. A check valve is provided to prevent the gas in the main body from flowing from the introduction hole side to the outlet hole side with the piston in between, but to prevent the gas from flowing from the outlet hole side to the introduction hole side. And a gas cell. 3. The gas cell according to claim 1, wherein said replacement means is provided in said introduction hole, said sample gas flows into said main body from said introduction hole in an open state, and said sample gas flows in said main body in a closed state. A valve capable of preventing the sample gas from flowing into the main body from the introduction hole, and a suction means provided in the outlet hole and capable of sucking the gas in the main body, By closing the valve and forcibly exhausting the gas in the main body to the outside by the suction means, the inside of the main body is brought into a negative pressure state, and in this state, the valve is opened to open the main body. A gas cell wherein a sample gas is forcibly sucked into the inside. 4. The gas cell according to claim 3, wherein the main body is provided with an outside air intake / exhaust hole, and the replacement means is configured so that the inside of the main body has the side of the introduction hole and the outlet hole and the outside air intake / exhaust hole. A gas cell comprising a film-like elastic body divided into two sides. 5. The gas cell according to claim 3, wherein when the sample gas is introduced into the main body, the valve is closed and the gas in the main body is exhausted by the suction means. Make the body under negative pressure,
In this state, the sample gas is forcibly sucked into the main body by opening the valve, and when detecting the light transmitted through the main body, the sample gas flows in the main body at a constant speed. A gas cell comprising a control means for appropriately controlling the suction force of the suction means so as to flow.