JP7410495B2 - Gas component detection device - Google Patents

Description

The present invention relates to a gas component detection device that detects gas components using gas chromatography technology.

Currently, various devices for detecting components using chromatography (see, for example, Patent Document 1) are put into practical use. Gas chromatography is one type of chromatography. Gas chromatography detects components contained in gases.

Conventionally, gas component detection devices using gas chromatography detect gas components by transporting a gas to be detected using a carrier gas and exposing the gas to a detector. Such a gas component detection device uses a column.

The column is a so-called flow path for a carrier gas mixed with a gas to be detected, and is arranged upstream of the detector. By appropriately setting the specifications of the column, a plurality of components in the gas to be detected and the carrier gas pass through the column at different propagation times. As a result, the times at which the plurality of components contained in the gas to be detected reach the detector are different. Therefore, the detector can detect multiple components individually.

Special Publication No. 2005-517197

However, when using a specific sensor (semiconductor type, catalytic combustion type, electrochemical type) as a detector, it is not easy to shorten the detection time while ensuring detection sensitivity at a predetermined level.

Therefore, an object of the present invention is to have high detection sensitivity and shorten detection time while using a specific sensor such as a semiconductor sensor as a detector.

The gas component detection device of the present invention includes a column, a first flow path, and a delay mechanism. The column is arranged upstream of the semiconductor sensor in the transport direction of the carrier gas mixed with the gas to be detected. The first flow path is connected between the column and the semiconductor sensor. The delay mechanism causes the flow rate of carrier gas in the column to be slower than the flow rate of carrier gas in the first flow path.

With this configuration, the flow rate of the gas to be detected flowing through the column is slow, and the ability to separate multiple components of the gas to be detected is improved. Furthermore, in this configuration, the flow rate of the gas to be detected that reaches the semiconductor sensor is high, and the detection speed is high.

According to this invention, the detection time can be shortened while achieving high detection sensitivity.

FIG. 1 is a diagram showing the configuration of a gas component detection device according to an embodiment of the present invention. FIG. 2 is a graph showing the transition state of the output voltage of the semiconductor sensor for each concentration. FIG. 3 is a graph showing the transition state of the output voltage of the semiconductor sensor depending on the flow velocity within the cavity. FIG. 4 is a diagram showing a chromatogram of gas chromatography according to the configuration of the present invention and a chromatogram according to a comparative configuration. FIG. 5 is a schematic diagram showing the configuration of a column portion of the gas component detection device according to the embodiment of the present invention.

A gas component detection device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of a gas component detection device according to an embodiment of the present invention. Note that FIG. 1 schematically shows an example of a gas component detection device using functional blocks and the like.

(Configuration of gas component detection device 10)
As shown in FIG. 1, the gas component detection device 10 includes a first flow path 21 and a column 30. Further, the gas component detection device 10 includes a second flow path 22 , a third flow path 23 , a fourth flow path 24 , a fifth flow path 25 , a sixth flow path 26 , a sensor device 40 , a component detection section 43 , a blower 51 , a filter 52, an input container 60, a valve 231, and a drive section 510.

The first flow path 21, the second flow path 22, the third flow path 23, the fourth flow path 24, the fifth flow path 25, and the sixth flow path 26 are tubular with a constant diameter.

One end of the first flow path 21 is connected to the sensor device 40 , and the other end of the first flow path 21 is connected to the column 30 . One end of the second flow path 22 is connected to the column 30, and the other end of the second flow path 22 is connected to the discharge port of the blower 51.

One end of the third flow path 23 is connected to the second flow path 22 , and the other end of the third flow path 23 is connected to the charging container 60 . The valve 231 is provided in the third flow path 23. By opening and closing the valve 231, the state of communication between the second flow path 22 and the charging container 60 is controlled.

One end of the fourth flow path 24 is connected to the sensor device 40, and the other end of the fourth flow path 24 is a discharge port 240.

One end of the fifth flow path 25 is connected to the suction port of the blower 51, and the other end of the fifth flow path 25 is connected to the filter 52. One end of the sixth flow path 26 is connected to the filter 52, and the other end of the sixth flow path 26 is connected to the carrier gas intake port 260.

The column 30 includes an individual flow path 31 , an individual flow path 32 , an individual flow path 33 , and an individual flow path 34 . A first end of the individual flow path 31 , a first end of the individual flow path 32 , a first end of the individual flow path 33 , and a first end of the individual flow path 34 are connected by a flow path coupling portion 301 . The second end of the individual flow path 31 , the second end of the individual flow path 32 , the second end of the individual flow path 33 , and the second end of the individual flow path 34 are connected by a flow path coupling portion 302 . The channel coupling portion 301 is connected to the first channel 21 , and the channel coupling portion 302 is connected to the second channel 22 . The column 30, that is, the individual channel 31, the individual channel 32, the individual channel 33, and the individual channel 34, are made of a flexible material and are made of a material that does not react with the gas to be detected. Note that the specific configuration of the column 30 will be described later.

Sensor device 40 includes a cavity 41 and a sensor 42. The cavity 41 is a space formed by the housing of the sensor device 40 and includes an inlet 411 and an outlet 412. The inlet 411 communicates with the first channel 21 , and the outlet 412 communicates with the fourth channel 24 .

Sensor 42 has a detection surface 420. Sensor 42 is arranged in the housing of sensor device 40 such that detection surface 420 is exposed within cavity 41 . The sensor 42 outputs from the output terminal 421 a voltage whose intensity corresponds to the concentration of the gas component that has come into contact with the detection surface 420 . Specifically, the sensor 42 is, for example, a semiconductor type sensor. Note that the sensor 42 is not limited to a semiconductor type sensor, but may be a catalytic combustion type sensor or an electrochemical type sensor.

The component detection unit 43 uses the output voltage of the sensor 42 to detect the components of the gas to be detected and their concentrations. Note that the component detection unit 43 has a known configuration, and a detailed description thereof will be omitted.

The blower 51 is a device that transports fluid in one direction, and is, for example, a blower using a piezoelectric material. By using a piezoelectric blower, the blower 51 can be made smaller. A drive section 510 is connected to the blower 51. The drive unit 510 supplies drive power to the blower 51. The blower 51 is driven by this driving power and transports the fluid from the suction port to the discharge port.

The filter 52 is a gas purification filter, and filters out impurities such as dust and particulates contained in the air, for example. The input container 60 contains the gas to be detected. For example, in the case where the gas component detection device is used to detect a specific component (for example, an acetone component) in human breath, the human breath is stored in the input container 60 in advance.

(Method for transporting gas to be detected and detecting components in gas component detection device 10)
In the above configuration, the blower 51 is driven and the valve 231 is opened. Thereby, the air that is the source of the carrier gas flows into the sixth flow path 26 from the carrier gas intake port 260 and is filtered by the filter 52. This generates carrier gas. The carrier gas is transported from the filter 52 to the fifth flow path 25 and sucked into the blower 51. The blower 51 discharges carrier gas into the second flow path 22 .

When the carrier gas flows into the second flow path 22 , the gas to be detected flows into the second flow path 22 from the input container 60 via the third flow path 23 . Thereby, the gas to be detected is mixed with the carrier gas, and the carrier gas mixed with the gas to be detected (hereinafter referred to as mixed gas for convenience of explanation) is transported from the second flow path 22 to the column 30.

The mixed gas carried into the column 30 is separated into an individual flow path 31 , an individual flow path 32 , an individual flow path 33 , and an individual flow path 34 at the flow path coupling portion 302 . The mixed gas flows into individual channels 31, 32, 33, and 34, respectively. At this time, the flow rate of the mixed gas flowing through the individual channels 31-34 decreases. The mixed gases flowing through the individual channels 31 , 32 , 33 , and 34 are combined at the channel coupling portion 301 and flow into the first channel 21 . By merging the mixed gases flowing into the individual channels 31-34, the flow rate of the mixed gas in the first channel 21 increases again.

The mixed gas that has flowed through the first channel 21 flows into the cavity 41 from the inlet 411 , passes through the fourth channel 24 from the outlet 412 , and is discharged from the outlet 240 . At this time, the mixed gas comes into contact with the detection surface 420 of the sensor 42 in the cavity 41, so that the components of the gas to be detected are detected.

Since the plurality of components of the gas to be detected have different flow rates in the column 30, the sensor 42 can detect the plurality of components individually.

(Specific configuration of column 30)
As described above, the column 30 includes the individual channels 31, 32, 33, and 34. The individual channels 31, 32, 33, and 34 are connected in parallel between the channel coupling section 301 and the channel coupling section 302.

The individual channels 31, 32, 33, and 34 are tubular with a constant diameter. The channel cross-sectional area S31 of the individual channel 31, the channel cross-sectional area S32 of the individual channel 32, the channel cross-sectional area S33 of the individual channel 33, and the channel cross-sectional area S34 of the individual channel 34 are the same. . In addition, in this application, the cross-sectional area of the flow path is the area of the cut surface of the internal space when the pipe is cut at a plane perpendicular to the direction in which the pipe extends, and the cross-sectional area of the flow path is the area of the cut surface of the internal space when the tube is cut in a plane perpendicular to the direction in which the tube extends. In this case, it refers to the area that is the sum of the cross-sectional areas of each of those individual channels.

Furthermore, the internal structure of the individual flow path 31, the internal structure of the individual flow path 32, the internal structure of the individual flow path 33, and the internal structure of the individual flow path 34 are the same. The same internal structure means, for example, that the material and thickness of the adsorbent or carrier formed on the inner wall surface of the tube are the same. Compared to a structure in which the adsorbent or carrier is filled inside the tube, by forming the adsorbent or the carrier on the inner wall surface of the tube, the individual flow paths 31, the individual flow paths 32, the individual flow paths 33, and This is effective because it is easier to make the internal structures of the individual flow paths 34 the same with higher accuracy. Note that the column 30 may be either a packed column or a capillary column. As the stationary phase and the liquid phase, known ones can be used.

In such a configuration, the channel cross-sectional area S31 of the individual channel 31, the channel cross-sectional area S32 of the individual channel 32, the channel cross-sectional area S33 of the individual channel 33, and the channel cross-sectional area of the individual channel 34 S34 is the same as the channel cross-sectional area S21 of the first channel 21.

The cross-sectional area of the column 30 is the cross-sectional area S31 of the individual flow path 31, the cross-sectional area S32 of the individual flow path 32, the cross-sectional area S33 of the individual flow path 33, and the cross-sectional area S33 of the individual flow path 34. This is the area obtained by adding the flow path cross-sectional area S34. Therefore, the channel cross-sectional area of the column 30 is larger than the channel cross-sectional area S21 of the first channel 21. Thereby, the flow rate of the mixed gas flowing through the column 30 becomes slower than the flow rate of the mixed gas flowing through the first channel 21. That is, column 30 functions as a delay mechanism.

(Effects due to the configuration of the gas component detection device 10)
By having the above-described configuration, the gas component detection device 10 can obtain the following effects.

FIG. 2 is a graph showing the transition state of the output voltage of the semiconductor sensor for each concentration. FIG. 2 shows a case where one type of component to be detected (for example, acetone) is detected. In FIG. 2, the horizontal axis shows the elapsed time from the start of detection, and the vertical axis shows the voltage difference ΔV with respect to the baseline voltage. FIG. 2 shows cases of density DE1, density DE2, density DE3, and density DE4. The density DE3 is higher than the density DE4, the density DE2 is higher than the density DE3, and the density DE1 is higher than the density DE2. That is, the relationship is density DE1>density DE2>density DE3>density DE4.

As shown in FIG. 2, when the sensor 42 is used, the higher the concentration of the component to be detected, the higher the voltage difference ΔV at saturation. Therefore, the gas component detection device 10 can detect the concentration of the component from the magnitude of the voltage difference ΔV.

FIG. 3 is a graph showing the transition state of the output voltage of the semiconductor sensor depending on the flow velocity within the cavity. FIG. 3 shows a case where one type of component to be detected (for example, acetone) is detected. In FIG. 3, the horizontal axis shows the elapsed time from the start of detection, and the vertical axis shows the voltage difference ΔV with respect to the baseline voltage. FIG. 3 shows cases of flow velocity FV1, flow velocity FV2, flow velocity FV3, and flow velocity FV4. The flow rate FV3 is higher than the flow rate FV4, the flow rate FV2 is higher than the flow rate FV3, and the flow rate FV1 is higher than the flow rate FV2. That is, the relationship is as follows: flow velocity FV1>flow velocity FV2>flow velocity FV3>flow velocity FV4.

As shown in FIG. 3, when the sensor 42 is used, the higher the flow rate of the mixed gas containing the component to be detected, the faster the time for the voltage difference ΔV (output voltage) with respect to the baseline voltage to become saturated. That is, the transient response becomes faster. Therefore, the higher the flow rate, the faster the detection target component can be detected. That is, by increasing the flow velocity in the first flow path 21, the detection time can be shortened.

Here, for example, in a conventional column that does not have the configuration of the present application, the flow rate of the column becomes equivalent to the flow rate of the first flow path 21. When the flow rate in the column increases, the separation ability of the component of the gas to be detected in the column decreases, and the desired sensitivity for the component to be detected cannot be obtained.

However, in the gas component detection device 10 of the present invention, the flow rate in the column 30 can be made slower (lower) than the flow rate in the first channel 21, as described above. Thereby, it is possible to suppress a decrease in the separation ability of the components of the gas to be detected in the column 30, and the component to be detected can be detected with high sensitivity.

FIG. 4 is a diagram showing a chromatogram according to the gas chromatography configuration of the present invention and a chromatogram according to a comparative configuration. The comparative configuration does not include the column 30 with a large flow passage cross-sectional area like the present invention, has the same flow passage cross-sectional area as the first flow passage 21, and has the same length as the individual flow passages 31-34 of the column 30. Shows a configuration with columns of length equal to the sum value. As shown in FIG. 4, by providing the configuration of the present application, the signal strength of the component to be detected becomes higher than that of the comparative configuration. Therefore, the gas component detection device 10 of the present application can detect the component to be detected with high sensitivity.

In this way, by having the configuration of this embodiment, the gas component detection device 10 can shorten the detection time while detecting the component to be detected with high sensitivity.

Furthermore, as shown in FIG. 2(B), the relationship between the concentration and the voltage difference ΔV is the same as in the saturated state even during the transient response period. Therefore, even during the transient response period, it is possible to detect the concentration of the component to be detected with high accuracy. Thereby, the component can be detected within the transient response period before the voltage difference ΔV is saturated, for example, like the measurement time tm in FIG. 2, and the gas component detection device 10 can further shorten the detection time.

At this time, the channel cross-sectional area S21 of the first channel 21 is set based on the transient response characteristic of detection by the sensor 42, that is, the reaction rate, and the channel cross-sectional area S21 of the column 30 (each individual channel 31 , 32, 33, and 34 (the sum of flow path cross-sectional areas S31, S32, S33, and S34) may be set based on the separation ability of the components of the gas to be detected. In other words, the ratio between the flow path cross-sectional area S21 of the first flow path 21 and the flow path cross-sectional area of the column 30 determines the optimum measurement time tm that can maintain accuracy in the sensor 42 and shorten the time required for the column 30. It is better if the setting is based on the expected resolution.

In addition, in the column 30 described above, the length L31 of the individual flow path 31, the length L32 of the individual flow path 32, the length L33 of the individual flow path 33, and the length L34 of the individual flow path 34 are set as much as possible. Preferably they are the same. As a result, the difference in resolution between the individual channels 31, 32, 33, and 34 is reduced or eliminated, and the component to be detected can be detected with higher sensitivity. However, the length L31 of these individual channels 31, the length L32 of the individual channels 32, the length L33 of the individual channels 33, and the length L34 of the individual channels 34 are determined according to the requirements of the gas component detection device 10. They may be different within the minimum resolution required. Note that this concept can also be applied to the flow path cross-sectional area and internal structure, and although they may be different within the range allowed by the separation ability, it is preferable that they be the same as possible.

Further, the detection surface 420 of the sensor 42 is preferably parallel to the direction of conveyance of the mixed gas in the cavity 41. Since the detection surface 420 and the transport direction are parallel, variations in the baseline of signal strength are reduced. This is because, for example, changes in temperature of the detection surface 420 of the sensor 42 due to contact with the mixed gas can be suppressed.

Thereby, the SN ratio of the output voltage of the sensor 42 can be improved. Therefore, the gas component detection device 10 can detect the component to be detected with even higher accuracy.

Further, the above-mentioned control of the flow rate is realized by the blower 51 arranged on the upstream side of the second flow path 22. The flow passage cross-sectional area S22 of the second flow passage 22 is the same as the flow passage cross-sectional area S21 of the first flow passage 21. Thereby, by arranging a current meter or the like in the second flow path 22 to measure the flow speed and feeding it back to the drive unit 510, the flow speed in the first flow path 21 can be easily controlled. By arranging the current meter on the upstream side of the connection position with the third flow path 23 in the second flow path 22, it is possible to suppress the current meter from being exposed to the gas to be detected.

Furthermore, in the above-described configuration, after the second flow path 22 achieves the same flow rate as the first flow path 21, the flow rate is temporarily reduced in the column 30. A third flow path 23 is connected to the second flow path 22 having a high flow rate. Thereby, the gas to be detected is drawn into the second flow path 22 from the input container 60 at a high flow rate, and the gas component detection device 10 can efficiently draw in the gas to be detected.

Further, the third channel 23 can also be connected to a plurality of individual channels 31-34 of the column 30. However, as described above, by connecting the third flow path 23 to the second flow path 22, the gas to be detected can be drawn in efficiently.

Furthermore, in the above description, a mode is shown in which the column 30 is configured with a plurality of individual channels 31-34, so that the channel cross-sectional area of the column 30 is made larger than the channel cross-sectional area S21 of the first channel 21. Ta. However, it is also possible to apply another embodiment, for example as shown in FIG. FIG. 5 is a schematic diagram showing the configuration of a column portion of the gas component detection device according to the embodiment of the present invention.

As shown in FIG. 5, the column 30A has a tubular shape with a larger diameter than the first flow path 21 and the second flow path 22. That is, the channel cross-sectional area S30A of the column 30A is larger than the channel cross-sectional area S21 of the first channel 21 and the channel cross-sectional area S22 of the second channel 22.

Even with such a configuration, the gas component detection device can shorten the detection time while achieving high detection sensitivity.

Note that it is also possible to combine the configuration shown in FIG. 1 and the configuration shown in FIG. 5 described above. That is, the flow path cross-sectional area of each individual flow path of the column shown in FIG. 1 may be larger than the flow path cross-sectional area S21 of the first flow path 21. Further, if the flow path cross-sectional area as a column is larger than the flow path cross-sectional area S21 of the first flow path 21, the flow path cross-sectional area of the individual flow path is larger than the flow path cross-sectional area S21 of the first flow path 21. It may be different, such as smaller.

10: Gas component detection device 21: First flow path 22: Second flow path 23: Third flow path 24: Fourth flow path 25: Fifth flow path 26: Sixth flow path 30, 30A: Columns 31, 32 , 33, 34: Individual flow path 40: Sensor device 41: Cavity 42: Sensor 43: Component detection unit 51: Blower 52: Filter 60: Input container 231: Valve 240: Outlet 260: Carrier gas intake port 301: Flow Channel coupling section 302: Channel coupling section 411: Inflow port 412: Outflow port 420: Detection surface 421: Output terminal 510: Drive section

Claims (6)

A sensor that detects the components of the gas to be detected;
a column disposed upstream of the sensor in the transport direction of the carrier gas mixed with the gas to be detected;
a first flow path connected between the column and the sensor;
Equipped with
The column includes a delay mechanism that makes the flow rate of the carrier gas in the column slower than the flow rate of the carrier gas in the first flow path,
The sensor is a semiconductor type sensor,
further comprising a sensor device having a cavity in which the sensor and a detection surface of the sensor are built;
Gas component detection device. The delay mechanism is
Including one in which the flow passage cross-sectional area of the column is larger than the flow passage cross-sectional area of the first flow passage.
The gas component detection device according to claim 1. The delay mechanism is
The column is configured with a plurality of individual channels,
The plurality of individual channels are each coupled to one channel at a first end and a second end,
The first end is connected to the first flow path.
The gas component detection device according to claim 2. The flow rate of the column is set based on the separation ability of the components of the detected gas,
The flow rate of the first flow path is set based on the reaction rate of the sensor,
A gas component detection device according to any one of claims 1 to 3. The detection surface of the sensor is parallel to the transport direction of the carrier gas within the cavity.
A gas component detection device according to any one of claims 1 to 4. comprising a detection unit that detects a component of the detected gas from the output signal of the sensor,
The detection unit detects the component from a transient response of the sensor.
A gas component detection device according to any one of claims 1 to 5 .

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