Gas Detection Device and Gas Detection Method

Abstract

To provide a gas detection device that can measure a specific gas component in a gas with high sensitivity by a simple method using a gas detection element.SOLUTION: A gas detection device 1 includes a container 2 that contains a collected gas, a tube 3 that is connected to the container at one end, a pump 4 that is connected to the other end of the tube and draws the gas in the container through the tube, and a gas detection element 5 that is placed in a flow path in the tube through which the gas flows and detects specific gases contained in the gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gas detection device and a gas detection method for detecting a specific gas contained in a gas which is a biological gas such as exhaled breath.

Background Art

[0002] In recent years, biological gas analysis, particularly exhaled breath analysis, has attracted attention as a health management method due to its non-invasive nature, and exhaled breath analyzers have been developed. For example, Patent Document 1 reports an exhaled breath analyzer, but the semiconductor sensor for detection provides a cavity separate from the gas flow path and precisely controls the flow rate. Further, Patent Document 2 reports a passive sampler for gas collection, but there, a porous diffusion plate or filter is provided to eliminate the influence of wind speed and expose the gas.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When attempting to collect a gas such as human exhaled breath released as a biological gas and precisely analyze a specific gas component to be detected in that gas, when using a semiconductor sensor or the like as a gas detection element, in order to accurately perform gas detection, it is necessary to accurately control the flow rate in order to accurately grasp the amount of gas in contact with the sensor, and for this purpose, a precise collection device design and a special structure in addition to the flow path are required. Also, in the case of a passive sampler, a diffusion plate that requires precise processing and, in addition, the installation of a plurality of diffusion control methods are required.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a gas detection device and a gas detection method for detecting a specific gas to be detected in a gas with high sensitivity by a simple method.

Means for Solving the Problems

[0006] The gas detection device of the present invention for solving the above problems includes a container for storing the collected gas, a tube having one end communicating with the container, a pump connected to the other end of the tube for sucking the gas in the container through the tube, and a gas detection element disposed in a flow path in the tube through which the gas flows for detecting a specific gas contained in the gas. , the gas detection element has a porous structure carrying a gas detection agent that reacts with the specific gas, and the pump sucks the gas so that the gas flow rate becomes diffusion rate-limiting. It is characterized by the above.

[0007] Further, the gas detection method of the present invention includes a housing step of housing the collected gas in a container, a suction step of communicating the container with one end of a tube and sucking the gas so that the gas in the container flows through the tube by a pump connected to the other end of the tube, and a detection step of exposing the gas to a gas detection element disposed in a flow path in the tube through which the gas flows by the suction step and detecting a specific gas contained in the gas based on a change in characteristics of the gas detection element. , the gas detection element has a porous structure carrying a gas detection agent that reacts with the specific gas, and the pump sucks the gas so that the gas flow rate becomes diffusion rate-limiting. It is characterized by the above.

Effects of the Invention

[0008] According to the gas detection device and the gas detection method of the present invention, by connecting one end to a container for storing gas, connecting the other end to a pump, and disposing a gas detection element inside a tube through which the gas passes, and sucking the gas with a pump or the like, detection can be performed based on the diffusion rate-limiting of the gas to be detected, so there is no need to precisely control the gas flow rate, and there is an excellent effect that the accuracy can be easily improved. Further, by making the tube transparent, measurement can be performed without taking out the gas detection element from the tube while the gas is flowing, and there is an excellent effect that the measurement can be performed accurately.

Brief Description of the Drawings

[0009]

Figure 1

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Figure 7

Best Mode for Carrying Out the Invention

[0010] Hereinafter, the best mode of the present invention will be described with reference to the drawings. However, such examples do not limit the technical scope of the present invention.

[0011] FIG. 1 is a diagram showing a first configuration example of a gas detection device according to an embodiment of the present invention. The gas detection device 1 includes a container 2 for accommodating a sampled gas, a pipe 3 having one end (gas inlet side) communicating with the container 2, a pump 4 connected to the other end (gas outlet side) of the pipe 3 and sucking the gas in the container 2 through the pipe 3, and a gas detection element 5 disposed in a flow path in the pipe 3 through which the gas in the container 2 flows. Note that FIG. 1(a) shows a configuration in which one gas detection element 5 is disposed in the pipe 3, and FIG. 1(b) shows a configuration in which two (a plurality of) gas detection elements 5 are disposed in the pipe 3.

[0012] The container 2 is preferably a gas collection bag (sampling bag) that collects and stores gases, particularly biological gases such as exhaled air. As the material of the gas collection bag 2, any material that does not adsorb the specific gas to be detected contained in the gas may be used. For example, a Teflon (registered trademark)-coated bag is used.

[0013] The tube 3 through which the gas passes is, for example, cylindrical or rectangular prism-shaped. In the case of a cylindrical shape, its cross-sectional shape is circular or elliptical. In the case of a rectangular prism-shaped tube, various shaped tubes such as a square or a rectangle including polygons can be adopted as its cross-sectional shape. At one end of the tube 3, a gas collection bag 2 containing the collected gas is attached in communication with the inside of the tube 3 so that the gas can flow in. A valve 9 for opening and closing the flow path of the tube 3 may be provided with respect to the container 2.

[0014] As the tube 3, for example, a transparent glass tube can be used. In the case of a transparent glass tube, as will be described later, by installing a light source outside the tube, such as an LED light source, and a light detector, such as a photodiode, for changes in the light absorption amount or reflection amount of the gas detection element 5 installed inside the tube 3, the state of the gas detection element 5 can be measured in real time without exposing it to the outside air after exposure, and the result can be obtained quickly. Also, by avoiding contamination by the outside air, high-precision measurement can be achieved. Further, by acquiring an image of the gas detection element 5 through the transparent glass tube, the color information of the gas detection element 5 can be converted into the gas concentration of the specific gas by image processing, making the measurement more convenient.

[0015] As the material of the tube 3, any material that does not adsorb the specific gas may be used. For example, a glass tube, a quartz tube, a Teflon tube, etc. can be used.

[0016] Also, the diameter of the tube 3 through which the gas passes may be such that the gas detection element 5 can be inserted, and for example, it can be set to 10 mm to 20 mm.

[0017] The pump 4 is attached to the other end side of the pipe 3 and sucks the gas in the container 2 attached to one end side through the pipe 3. Due to the suction of the pump 4, the gas in the container 2 flows from one end side to the other end side of the pipe 3.

[0018] The pump 4 may be any pump that can suck gas at a flow rate (suction volume) of, for example, 0.05 L / min to 2.0 L / min. With the cross-sectional area of the pipe being a constant, the flow rate is proportional to the flow velocity. If the flow rate is too low, the detection of the gas will be supply-rate limited rather than diffusion-rate limited, so the output of the gas detection element 5 will depend on the flow velocity. If the flow velocity is too high, it is necessary to collect a large amount of gas, which will increase the error and may even make the collection difficult. Therefore, the pump 4 of the present invention sucks the gas so that the flow velocity of the gas flowing through the pipe 3 becomes diffusion-rate limited.

[0019] As the pump 4, for example, a small pump that can control the flow velocity, such as a small pump used for environmental measurement using a detection tube, may be used, or a manual pump may also be used.

[0020] The gas detection element 5 is a gas detection element having a porous structure carrying a gas detection agent that reacts with a specific gas component to be detected. The specific gas is, for example, ketones such as acetone, aldehydes such as formaldehyde, nitrogen oxides, etc. In the gas detection element 5 having a porous structure, the pore diameter of the porous body is, for example, 4 nm, and it may be within the range of 4 nm to 100 nm. The pore diameter of the porous body may be a small pore diameter that can be detected in the diffusion rate of the gas in the detection of the gas.

[0021] The gas detection element 5 is arranged in the flow path in the tube 3 such that its detection surface is, for example, parallel to the longitudinal direction of the tube 3. That is, the gas in the tube 3 flows across the detection surface of the gas detection element 5 from one end side to the other end side. If arranged in parallel, when the detection surfaces are the upper and lower surfaces, gas diffusion occurs on the upper and lower surfaces. Also, for example, it may be arranged in the flow path in the tube 3 such that it is, for example, perpendicular to the longitudinal direction. In this case, since the conductance of the detection element is very small, the gas in the tube 3 collides with the detection surface of the gas detection element 5 and then flows across the surface of the detection element vertically and horizontally. Here, gas diffusion occurs from the contact surface between the detection element and the gas into the detection element.

[0022] Also, as shown in FIG. 1(b), a plurality of gas detection elements 5 that react to different specific gas components may be arranged in parallel in the tube 3. It is possible to detect a plurality of types of specific gases simultaneously.

[0023] FIG. 2 is a diagram showing a second configuration example of the gas detection device according to the embodiment of the present invention. The second configuration example further includes a light source 6 and a photodetector 7 as compared with the first configuration example. Also, the tube 3 is a transparent tube or a tube that can transmit a certain amount of the light to be detected. The light source 6 and the photodetector 7 are arranged sandwiching the gas detection element 5 arranged in the tube 3, and the light emitted by the light source (for example, an ultraviolet light-emitting diode) 6 irradiates the gas detection element 5 arranged in the tube 3. The photodetector 7 is, for example, a detection unit of a photodiode or a spectrophotometer, and detects the light transmitted through the gas detection element 5. Thereby, the absorbance of the gas detection element 5 can be measured in a state where the gas detection element 5 is arranged in the tube 3.

[0024] Note that after flowing gas in the tube 3 and exposing the gas detection element 5 arranged in the tube 3 to the gas, the gas detection element 5 may be taken out of the tube 3, the taken-out gas detection element 5 may be arranged at a predetermined position, and the absorbance of the gas detection element 5 may be measured by the light source 6 and the photodetector 7.

[0025] FIG. 3 is a diagram showing a third configuration example of the gas detection device according to the embodiment of the present invention. The third configuration example further includes an imaging device (camera or scanner) 8 as compared with the first configuration example. Further, the tube 3 is a transparent tube or a tube capable of acquiring a detection image to some extent. The imaging device 8 is arranged to be able to image the detection surface of the gas detection element 5 through the transparent tube 3, and by imaging the detection surface of the gas detection element 5 with the imaging device 8, the color information (for example, RGB value) of the gas detection element 5 can be measured from the image data.

[0026] In addition, after flowing a gas in the tube 3 and exposing the gas detection element 5 arranged in the tube 3 to the gas, the gas detection element 5 may be taken out of the tube 3, the taken-out gas detection element 5 may be arranged at a predetermined position, and the gas detection element 5 may be imaged by the imaging device 8, and the color information may be acquired from the image data.

[0027] FIG. 4 is a flowchart of a gas detection method by the gas detection device of the present invention. In the gas detection method, first, a gas that is a biological gas such as exhaled breath is collected and stored in the container 2 (S100). Then, the container 2 is attached to one end of the tube 3 so as to be communicable, and the gas in the container 2 is sucked so that the gas flows through the tube by the pump 4 connected to the other end of the tube 3 (S102), that is, the gas is forcibly flowed into the tube 3 by the suction of the pump 4. The gas is exposed to the gas detection element 5 arranged in the tube 3 through which the gas flows at a predetermined flow rate by the suction operation (S104), and a specific gas contained in the gas is detected based on the characteristic change of the gas detection element 5 exposed to the gas (S106).

[0028] In the suction step (S102), the suction operation of the pump 4 is controlled so that the gas flows through the tube 3 at a flow rate equal to or higher than a certain value so that the flow rate of the gas becomes diffusion rate-limiting.

[0029] Further, when the gas is exhaled gas, the pump is not required by a human directly exhaling without collecting the gas, and the above steps may be performed by adjusting the amount of exhaled breath by the human.

[0030] The change in the characteristics of the gas sensor element 5 is, for example, a change in the degree of light absorption (absorbance) of the gas sensor element 5. Based on the second configuration example of FIG. 2, the absorbance of the gas sensor element 5 may be measured in situ by using a transparent tube for the tube 3 and attaching a light source 6 and a photodetector 7 to the tube 3. Also, according to the first configuration example, after the gas sensor element 5 is exposed to the gas in the tube 3, the gas sensor element 5 may be taken out of the tube 3 and the absorbance may be measured using the light source 6 and the photodetector 7. The concentration of a specific gas can be determined corresponding to the absorbance of the gas sensor element 5.

[0031] For example, as a gas detection device using an acetone detection element for detecting acetone as the gas sensor element 5, as shown in FIG. 2, the gas sensor element 5 is arranged between, for example, an ultraviolet light emitting diode with a central wavelength of emitted light of 385 nm as the light source 6 and a photodetector as the photodetector 7, and the light transmitted through the gas sensor element 5 can be detected by the photodetector, and the output signal from the photodetector is processed to output the change in the absorbance of the gas sensor element. With such a simple device configuration, the measurement of the above-mentioned extremely trace amount of acetone can be easily performed.

[0032] Also, the change in the characteristics of the gas sensor element 5 is, for example, a change in the color of the gas sensor element 5. Based on the third configuration example of FIG. 3, the color information of the gas sensor element 5 is obtained by imaging the gas sensor element 5 with an imaging device 8 and measuring the RGB values of the image data. The image of the gas sensor element 5 may be obtained in situ through the tube 3 using a transparent tube 3. Also, according to the first configuration example, after the gas sensor element 5 is exposed to the gas in the tube 3, the gas sensor element 5 is taken out of the tube 3 and imaged with the imaging device 8, and the color information (RGB values) may be obtained from the image data. The concentration of a specific gas can be determined corresponding to the color information of the gas sensor element 5.

Example

[0033] Hereinafter, the present invention will be specifically described based on examples. Here, specific conditions are shown for easy understanding of the invention, but the implementation of the present invention is not limited to the following combinations of implementation and numerical ranges.

[0034] An acetone gas sensor element was used as the gas sensor element. The manufacturing method of the acetone gas sensor element is, for example, the method disclosed in Document 1 below. Document 1: Microchemical Journal, 159, (2020)105428

[0035] A porous glass with a pore diameter of 4 nm was used as the substrate. A gas sensor element whose absorption spectrum (absorbance) in the range of 300 nm to 2000 nm had been measured in advance with a spectrophotometer (photodetector) was placed parallel to the glass tube inside a glass tube with an inner diameter of 12 mm. Air with a humidity of about 50% and an acetone concentration of 5 ppm was adjusted in a commercially available 2 L sampling bag. The cock of the sampling bag was connected to the glass tube using a silicon rubber stopper and a Teflon tube. The other end of the transparent glass tube was connected to a pump using a silicon rubber stopper and a Teflon tube. A suction pump for atmospheric measurement was used as the pump. The pump was operated to allow ventilation at a flow rate of 0.05 L / min for 5 minutes. Then, the gas sensor element was taken out and the absorption spectrum in the range of 300 nm to 2000 nm was measured with a spectrophotometer, and the difference in absorbance at 390 nm was calculated.

[0036] Next, a similar system was assembled and the pump was operated to allow ventilation at a flow rate of 0.1 L / min for 5 minutes. Then, the gas sensor element was taken out and the absorption spectrum in the range of 300 nm to 2000 nm was measured with a spectrophotometer, and the change amount of absorbance at 390 nm was calculated.

[0037] Next, a similar system was assembled and the pump was operated to allow ventilation at a flow rate of 0.2 L / min for 5 minutes. Then, the gas sensor element was taken out and the absorption spectrum in the range of 300 nm to 2000 nm was measured with a spectrophotometer, and the change amount of absorbance at 390 nm was calculated.

[0038] Next, a similar system was assembled, the pump was operated, and air was passed through at a flow rate of 0.3 L / min for 5 minutes. Then, the gas sensor element was taken out, and the absorption spectrum from 300 nm to 2000 nm was measured with a spectrophotometer, and the change amount of the absorbance at 390 nm was calculated.

[0039] The measurement results of the change amount of the absorbance of the gas sensor element corresponding to the gas flow rate are shown in Fig. 5. The difference in absorbance is constant at any flow rate, and it is diffusion-controlled for the detection of acetone by the sensor element. It was clarified that fine control is not necessary if the flow rate is 0.05 L / min or more. Also, it was shown that measurement can be easily performed using a small volume of gas with a simple system using only such a gas sensor element and a tube.

Example

[0040] An acetone sensor element was used as the gas sensor element. The manufacturing method of the acetone sensor element is, for example, the method disclosed in the above-mentioned Document 1. Porous glass with a pore diameter of 4 nm was used as the substrate. The gas sensor element, for which an image had been acquired in advance with a digital camera, was placed parallel to the inside of a glass tube with an inner diameter of 12 mm. Air with a humidity of about 50% and an acetone concentration of 5 ppm was adjusted in a commercially available 2 L sampling bag. The cock of the sampling bag was connected to the glass tube using a silicon rubber stopper and a Teflon tube. The other end of the glass tube was connected to a pump using a silicon rubber stopper and a Teflon tube. A suction pump for atmospheric measurement was used as the pump. The pump was operated, and air was passed through at a flow rate of 0.05 L / min for 5 minutes. Then, the gas sensor element was taken out, and an image was acquired with a digital camera (imaging device). The images before and after exposure were subjected to RGB analysis, and the change amount of the B / G value was calculated.

[0041] Next, a similar system was assembled, the pump was operated, and air was passed through at a flow rate of 0.1 L / min for 5 minutes. Then, the gas sensor element was taken out, and an image was acquired. The images before and after exposure were subjected to RGB analysis, and the change amount of the B / G value was calculated.

[0042] Next, a similar system was assembled, the pump was operated, and ventilation was carried out at a flow rate of 0.2 L / min for 5 minutes. Then, the gas sensor element was taken out and an image was acquired. The images before and after exposure were subjected to RGB analysis, and the change amount of the B / G value was calculated.

[0043] Next, a similar system was assembled, the pump was operated, and ventilation was carried out at a flow rate of 0.3 L / min for 5 minutes. Then, the gas sensor element was taken out and an image was acquired. The images before and after exposure were subjected to RGB analysis, and the change amount of the B / G value was calculated.

[0044] The measurement results of the change amount of the color information (B / G value) of the gas sensor element corresponding to the gas flow rate are shown in Fig. 6. The change amount of the B / G value is almost constant at any flow rate, and it is diffusion-controlled for the detection of acetone by the sensor element. It was clarified that fine control is not necessary if the flow rate is 0.05 L / min or more. Also, it was shown that measurement can be easily performed using a small volume of gas with a simple system using only such a gas sensor element and a tube.

Example

[0045] An acetone sensor element and a nitrogen dioxide sensor element were used as the gas sensor elements. The manufacturing method of the acetone sensor element is, for example, the method disclosed in the above-mentioned Document 1. The manufacturing method of the nitrogen dioxide sensor element is, for example, the method disclosed in the following Document 2. Document 2: Sensors and Actuators B 173, 191 - 196(2012)

[0046] A porous glass with a pore diameter of 4 nm was used as the substrate. Each gas sensor element, whose absorption spectrum in the range of 300 nm to 2000 nm had been measured in advance with a spectrophotometer, was placed parallel to a glass tube with an inner diameter of 12 mm, 1 cm away from the glass tube. A mixed gas with a humidity of about 50%, an acetone concentration of 5 ppm, and a nitrogen dioxide concentration of 100 ppb was adjusted in a commercially available 2 L sampling bag. The cock of the sampling bag was connected to the glass tube using a silicon rubber stopper and a Teflon tube. The other end of the glass tube was connected to a pump using a silicon rubber stopper and a Teflon tube. An aspiration pump for atmospheric measurement was used as the pump. The pump was operated and air was passed through at a flow rate of 0.05 L / min for 5 minutes. Then, each gas sensor element was taken out and its absorption spectrum in the range of 300 nm to 2000 nm was measured with a spectrophotometer. For the acetone sensor element, the change amount of the absorbance at 390 nm was calculated, and for the nitrogen dioxide sensor element, the change amount of the absorbance at 525 nm was calculated.

[0047] Next, a similar system was set up and the pump was operated to pass air through at a flow rate of 0.1 L / min for 5 minutes. Then, each gas sensor element was taken out and its absorption spectrum in the range of 300 nm to 2000 nm was measured with a spectrophotometer. For the acetone sensor element, the change amount of the absorbance at 390 nm was calculated, and for the nitrogen dioxide sensor element, the change amount of the absorbance at 525 nm was calculated.

[0048] Next, a similar system was set up and the pump was operated to pass air through at a flow rate of 0.2 L / min for 5 minutes. Then, each gas sensor element was taken out and its absorption spectrum in the range of 300 nm to 2000 nm was measured with a spectrophotometer. For the acetone sensor element, the change amount of the absorbance at 390 nm was calculated, and for the nitrogen dioxide sensor element, the change amount of the absorbance at 525 nm was calculated.

[0049] Next, a similar system was set up and the pump was operated to pass air through at a flow rate of 0.3 L / min for 5 minutes. Then, each gas sensor element was taken out and its absorption spectrum in the range of 300 nm to 2000 nm was measured with a spectrophotometer. For the acetone sensor element, the change amount of the absorbance at 390 nm was calculated, and for the nitrogen dioxide sensor element, the change amount of the absorbance at 525 nm was calculated.

[0050] The measurement results of the change amount of the absorbance of each gas detection element corresponding to the gas flow velocity are shown in Fig. 7. At any flow velocity, the difference in absorbance of each is constant, and it is diffusion-controlled for the detection of acetone and nitrogen dioxide by the detection element. It was clarified that fine control is not necessary if the flow velocity is 0.05 L / min or more. Also, it was shown that each substance in the mixed gas can be accurately measured using a small volume of gas simply and conveniently in such a simple system that only uses a plurality of gas detection elements and tubes.

[0051] The present invention is not limited to the above embodiments, and even if there are design changes within the scope not departing from the gist including various modifications and corrections that can be conceived by those having ordinary knowledge in the field of the present invention, it is of course included in the present invention.

Explanation of reference numerals

[0052] 1: Gas detection device, 2: Container, 3: Tube, 4: Pump, 5: Gas detection element, 6: Light source, 7: Photodetector, 8: Imaging device, 9: Valve

Claims

1. A container for containing the collected gas, A tube with one end communicating with the container, A pump connected to the other end of the tube for sucking the gas in the container through the tube, A gas detection element disposed in the flow path of the tube through which the gas flows for detecting a specific gas contained in the gas, The gas detection element is composed of a porous structure carrying a gas detection agent that reacts with the specific gas, The pump is characterized in that it sucks the gas so that the gas flow rate becomes diffusion rate-limiting. A gas detection device.

2. The gas detection device according to claim 1, further comprising a light source for irradiating the gas detection element with light and a photodetector for detecting transmitted light from the gas detection element in order to measure the absorbance of the gas detection element.

3. The gas detection device according to claim 1, further comprising an imaging device for imaging the gas detection element in order to acquire color information of the gas detection element.

4. A containing step of containing the collected gas in a container, A suction step of communicating the container with one end of the tube and sucking the gas so that the gas in the container flows through the tube by a pump connected to the other end of the tube, A detection step of exposing the gas to a gas detection element disposed in the flow path of the tube through which the gas flows by the suction step and detecting a specific gas contained in the gas based on a change in characteristics of the gas detection element, The gas detection element is composed of a porous structure carrying a gas detection agent that reacts with the specific gas, The pump is characterized in that it sucks the gas so that the gas flow rate becomes diffusion rate-limiting. A gas detection method.

5. The gas detection method according to claim 4, characterized in that a specific gas contained in the gas is detected based on a comparison between a characteristic value of the gas detection element measured in advance before exposure to the gas and a characteristic value of the gas detection element measured in a state of being exposed to the gas.

6. The characteristic value of the gas detection element is the absorbance of the gas detection element. The absorbance of the gas detection element is measured by irradiating the gas detection element with light from a light source and detecting transmitted light from the gas detection element by a photodetector. The gas detection method according to claim 5.

7. The characteristic value of the gas detection element is the color information of the gas detection element. The gas detection method according to claim 5, characterized in that the gas detection element is imaged by an imaging device and RGB values of the imaged image data are measured.

Images