JP2000002679A - Odor measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure an odor accurately by removing residue of a sample gas for previous measurement from a channel. SOLUTION: A sample gas is fed through a capturing pipe 19 by coupling a valve 17 between a and b, and sample components are adsorbed by an adsorbent. N2 is then fed through the capturing pipe 19 by coupling the valve 17 between b and c and the sample gas remaining in the channel subsequent to the valve 17 is purged. Subsequently, the capturing pipe 19 is heated while feeding N2 reversely through the capturing pipe 19 by switching a six-way valve 18 to a position shown by a solid line and the sample components liberated from the adsorbent are introduced to a flow cell 26. Thereafter, the valve 17 is coupled between a and c and the N2 gas is discharged from a sample gas introduction port 16 thus purging the sample gas remaining in the channel preceding the valve 17. Consequently, the sample gas in the sample gas channel is purged between the sample gas introduction port 16 and the valve 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an odor measuring device for measuring an odor component contained in a sample gas using an odor sensor which is a kind of gas sensor. The odor measuring device of the present invention is used in a wide range of fields such as quality inspection of foods and fragrances, quantitative detection of odor pollution, fire alarm by detection of burnt odor, and further, criminal investigation such as tracking, identification, authentication and drug inspection of persons. Available to

[0002]

2. Description of the Related Art An odor sensor electrically (or optically) converts a physical change of an odor component contained in air (or a supplied sample gas) caused by adhering to a sensitive surface of the sensor. It is to be measured. As an odor sensor, a sensor using an oxide semiconductor and a sensor using a conductive polymer are known.

When measuring an odor component in a sample gas having a relatively low concentration using an odor measurement device using such an odor sensor, a thermal desorption method (thermal desorption) is used to increase the concentration of the component to be measured. Is often performed. In the thermal desorption method, first, a sample gas is passed through a concentrating tube loaded with an adsorbent for adsorbing the component to be measured, and the component to be measured contained in the sample gas is adsorbed on the adsorbent. Then, after the component to be measured is sufficiently adsorbed, the temperature of the adsorbent is rapidly raised while flowing a carrier gas through the concentrating tube. Thus, the component to be measured that has been adsorbed is released from the adsorbent in a short time, and is carried on the carrier gas to the odor sensor at a high concentration. As the carrier gas, a chemically inert gas such as nitrogen gas is used so as not to not respond to the odor sensor and not to damage the sensitive film or electrode of the odor sensor.

[0004]

In a configuration using such a concentrating tube, the sample gas and the carrier gas are usually introduced into the concentrating tube alternatively by switching a valve or the like. In the case of continuously measuring a plurality of types of sample gases, the accuracy of the measurement is impaired if any of the sample components in the previously measured sample gas remain in the channel.

The present invention has been made in view of the above points, and an object of the present invention is to provide an odor measuring device that concentrates a sample gas in a concentration tube and then introduces the gas into an odor sensor. It is an object of the present invention to provide an odor measurement device capable of completely removing components in a sample gas obtained and performing the next measurement.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a collection tube loaded with an adsorbent that adsorbs a sample component contained in a sample gas and releases the sample component by heating. A odor measuring device comprising: a gas concentrating means including: and a odor detecting means for detecting a sample component concentrated by the gas concentrating means, a) a sample gas supply port to which a sample gas supply source is detachably connected; B) a carrier gas supply source for supplying a carrier gas; c) flow path switching means for connecting the sample gas supply port, the carrier gas supply source, and the collection tube to each other, and when gas is concentrated, The sample gas supply port is connected to the collection tube, the sample gas flows through the collection tube to adsorb the sample components to the adsorbent, and then the carrier gas is connected to the carrier gas supply source and the collection tube. To the collection tube Te expel residual sample gas, also is characterized by comprising a flow passage switching means for discharging the carrier gas is connected to the sample gas inlet and a carrier gas supply source from the sample gas supply port, a.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In this configuration, the carrier gas is:
In addition to being used to drive out the residue of the sample gas introduced into the flow path during gas enrichment, the sample component adsorbed by the adsorbent in the collection tube is released when the sample component is released by heating. It can be used to carry to odor detection means.

[0008] First, when the sample gas supply port and the collection tube are connected by the flow path switching means while the sample gas supply source is connected to the sample gas supply port, the sample gas introduced into the sample gas supply port is connected. Flows into the collection tube, and the sample component is adsorbed on the adsorbent. After the sample components are sufficiently adsorbed, the flow path switching means is switched to flow the carrier gas from the carrier gas supply source to the collection tube. As a result, the sample gas remaining in the collection tube and the flow path before and after the collection pipe (particularly, the flow path from the flow path switching means to the collection pipe) is pushed out and replaced by the carrier gas. At this time, the sample component adsorbed by the adsorbent remains as it is. At the same time or thereafter, the sample gas supply source is removed from the sample gas supply port, and the sample gas supply port and the carrier gas supply source are connected by the flow path switching unit.
As a result, the carrier gas is discharged from the sample gas supply port via the flow path switching means. As a result, the sample gas remaining in the flow path between the sample gas supply port and the flow path switching means is also expelled. In order to simultaneously drive out the sample gas remaining in both the sample gas supply port side and the collection tube side with the flow path switching means interposed therebetween, the three components of the sample gas supply port, the carrier gas supply source, and the collection pipe are required. Both may be connected at the same time.

In order to introduce the sample components into the odor detecting means, the adsorbent is heated while flowing the carrier gas through the collection tube, and the sample components adsorbed by the adsorbent are desorbed and put on the carrier gas. It is good to carry it to the odor detection means. Further, for that purpose, a flow path switching means for selectively switching between a flow path in which the gas passing through the collection tube is directly discharged to the outside and a flow path in which the gas is introduced into the odor detection means is provided. It is preferable to keep it.

[0010]

In the odor measuring apparatus according to the present invention, the sample gas introduced into the flow path including the collection tube for the adsorption of the sample component and remaining in the flow path at the end of the adsorption is: Subsequent expelling of the sample gas in the upstream and downstream directions clears the inside of the flow path. Therefore, when the odor measurement of another sample gas is performed next, accurate and highly reproducible measurement can be performed without being affected by the components of the sample gas previously measured.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the odor measuring device according to the present invention will be described below with reference to FIG. FIG. 1 is a configuration diagram of a main part of the odor measuring device of the present embodiment, centering on a gas flow path.

The flow paths on the outlet side of the constant pressure valve 11 provided at the gas outlet of the nitrogen gas container 10 filled with pure nitrogen gas (N 2) have two first and second needle valves 13 and 15, respectively. It branches into two nitrogen gas flow paths 12 and 14. The flow path connected to the sample gas inlet 16 and the first nitrogen gas flow path 12 are connected to ports a and c of a three-way valve (3 port 3 position valve) 17, respectively, and the remaining port b is a hexagonal valve. The valve (6 port 2 position valve) 18 is connected to port a. Further, the second nitrogen gas flow path 14 is connected to the port d of the six-way valve 18.
It is connected to the. A collection tube 19 provided with a heater 20 for heating is connected between the port c and the port f of the hexagonal valve 18, and the collection tube 19 is connected to the collection tube 19 in accordance with a sample component to be measured. For example, a carbon-based adsorbent or another appropriate adsorbent is filled.

The port b of the six-way valve 18 is connected to a three-way valve (three-port two-position valve) 21 through an outlet 2.
4 and a flow path connected to the outlet 24 via the needle valve 22 and the pump 23 are selectively connected. The port e of the six-way valve 18 is connected to a flow cell 26 having an odor sensor 25, and the downstream outlet thereof is connected to a discharge port 32 via a valve 30 and a check valve 31. The six-way valve 18 and the flow cell 26
A constant temperature bath 27 controlled to a predetermined temperature by a temperature adjusting unit 28
It is installed in. The resistance change between the electrodes of the odor sensor 25 is measured by the measuring unit 29, and the odor is identified based on the measurement result.

The control unit 33 is provided with an operation unit 34. The three-way valves 17, 21, the six-way valve 18, the pump 23, the heater 2
0, controls the operation of each unit such as the temperature adjustment unit 28. In addition,
As a pipe material for each flow path, P which has little adsorption of sample components
It is desirable to use a TFE tube.

FIG. 2 is a diagram showing an example of the configuration of a three-port valve 17 having three ports and three positions. This three-way valve 1
7 includes three two-way valves 171, 172, and 173 such that one port of each of the two-way valves 171, 172, and 173 is connected in common, and the other port is connected to an external flow path. It has become. In this configuration, an appropriate two of the three two-way valves 171, 172, and 173 are controlled so as to flow, so that any two of the three ports a, b, and c are controlled. Ports are connected.

Next, the operation of the odor measuring device will be described in detail along the measuring procedure. (I) Collection of sample components First, the control unit 33 switches the three-way valve 17 so that the sample gas inlet 16 is connected to the port a of the six-way valve 18 (communicates the ports a and b), and controls the six-way valve 17. The three-way valve 21 is switched so that the port b of the valve 18 is connected to the needle valve 22 side. Further, the pump 23 is operated by switching the six-way valve 18 to the connection state shown by the broken line in FIG. Then, the sample gas introduced into the sample gas inlet 16 by the suction force of the pump 23 passes through the collection tube 19 via the three-way valve 17 (flows in the direction of arrow A in FIG. 2) and the six-way valve 18 (see FIG. 2). 1 (from left to right in FIG. 1), and further through a six-way valve 18, a three-way valve 21, and a needle valve 22 to be discharged from a discharge port 24. The sample gas contains, for example, a sample component (odor component) to be measured in clean air. At this time, the heater 20 is not energized, and the sample component contained in the sample gas is adsorbed by the adsorbent when the sample gas passes through the collection tube 19.

On the other hand, since the gas pressure at the gas outlet of the nitrogen gas container 10 is higher than the gas pressure at the outlet 32, the nitrogen gas supplied through the second nitrogen gas flow path 14 is supplied through the six-way valve 18. Circulates through the flow cell 26 and discharges 3
Exhausted from 2. The flow rate of this nitrogen gas is appropriately adjusted by the opening of the needle valve 15. This allows
The odor sensor 25 is kept in a nitrogen gas atmosphere.

(Ii) Replacement of Sample Gas in Collection Tube After flowing the sample gas through the collection tube 19 for a predetermined time, the control unit 33 switches the three-way valve 17 (ports b and c).
The first nitrogen gas flow path 12 is connected to the six-way valve 18.
And the port b of the six-way valve 18 is connected directly to the outlet 24 by switching the three-way valve 21. Then, since the gas pressure at the gas outlet of the nitrogen gas container 10 is higher than the gas pressure at the outlet 24,
The nitrogen gas supplied from the nitrogen gas container 10 instead of the sample gas is the first nitrogen gas flow path 12-the three-way valve 17 (flows in the direction of the arrow B in FIG. 2)-the six-way valve 18-the collecting pipe 19- The gas passes through the six-way valve 18-the three-way valve 21 and is discharged from the discharge port 24. As a result, the sample gas remaining in the flow path from the common connection point of the three-way valve 17 to the three-way valve 21 including the collection tube 19 is pushed out to the outside by the nitrogen gas. Also at this time, the heating by the heater 20 is not performed, and the sample component previously adsorbed by the adsorbent in the collection tube 19 remains as it is. On the other hand, since nitrogen gas continues to flow through the flow cell 26, the odor sensor 25 is kept in a nitrogen gas atmosphere.

(Iii) Introduction of Sample Components into Flow Cell After flowing nitrogen gas through the collection tube 19 for a predetermined time, the control unit 33 switches the six-way valve 18 to the connection state shown by the solid line in FIG. Then, the second nitrogen gas flow path 14-the six-way valve 18-the collecting pipe 19-the six-way valve 18-the flow cell 2
6-A discharge passage 32 is formed. In this state, energization of the heater 20 is started, and the collection tube 19 is rapidly heated (for example, at a heating rate of about 10 ° C./sec to about 250 to 300 ° C.). As a result, the sample component adsorbed on the adsorbent in the collection tube 19 is separated from the adsorbent, and rides on the nitrogen gas flowing in the opposite direction (from right to left in FIG. 1) to the flow cell. Transported to 26. When the nitrogen gas containing the sample component passes through the flow cell 26, the sample component is adsorbed on the sensitive film of the odor sensor 25, and the electric resistance between the electrodes of the odor sensor 25 changes. The measuring unit 29 detects the sample component by detecting the resistance change. In addition, at least during the period of introduction of the sample components, the thermostat 27 is maintained at about 40 ° C. by the temperature adjusting unit 28. Thereby, the influence of the temperature dependency of the detection by the odor sensor 25 can be avoided, and the high-boiling-point sample components can be circulated smoothly.

(Iv) Cleaning the inside of the flow path and the odor sensor When the odor component detection operation as described above is completed, the control unit 33 stops heating by the heater 20. Thus, the collection tube 19 is gradually cooled by air cooling. Of course,
A fan may be provided for quick cooling, or cooling by water cooling may be performed. If the control unit 33 detects that the temperature of the collection tube 19 has dropped to about 40 ° C., or if a sufficient time has elapsed for the temperature to drop to about 40 ° C., the port a of the three-way valve 17 ,
The sample gas inlet 16 and the first nitrogen gas flow path 12 are connected so that c is communicated. At this time, the sample gas is not sent to the sample gas inlet 16, but is kept open to the atmosphere, for example. Then, since the gas pressure at the gas outlet of the nitrogen gas container 10 is higher than the gas pressure at the sample gas inlet 16, the nitrogen gas flows from the first nitrogen gas flow path 12 through the three-way valve 17 (arrow C in FIG. 2). Flows toward the sample gas inlet 16 and is discharged to the outside. As a result, the sample gas remaining in the flow path between the sample gas inlet 16 and the common connection point of the three-way valve 17 is also expelled by the nitrogen gas.

The control section 33 causes the temperature adjusting section 28 to raise the temperature of the thermostatic bath 27 to a predetermined temperature. As a result, when the ambient temperature of the odor sensor 25 rises, the sample components and other impurities adsorbed on the sensitive film are desorbed and carried out from the outlet 32 by the flowing nitrogen gas. As a result, the sensitive film of the odor sensor 25 recovers, and returns to a state where the sample components can be detected again.

As described above, the replacement of the sample gas in the collection tube 19 and the cleaning process in the flow path cause the sample gas introduction port 16 to flow through the path through which the sample gas flows when the sample components are introduced.
The sample gas is completely removed from the flow path from the flow to the three-way valve 21. Therefore, when the measurement of another sample gas is performed next, the concentration can be performed without being affected by the sample gas measured before that.

The series of processes relating to the measurement described above can be automatically performed according to a program preset in the control unit 33. For example, the time for switching each valve and the heating temperature of the heater 20 It is preferable that the parameters such as can be set from the operation unit 34 as appropriate according to the type of the sample component. In addition to the automatic measurement, the measurer may sequentially give instructions from the operation unit 34 to manually advance each measurement process.

It should be noted that the above embodiment is merely an example, and it is clear that modifications and modifications can be made within the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an odor measuring device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating an example of a three-way valve in the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Nitrogen gas container 11 ... Constant pressure valve 12,14 ... Nitrogen gas flow path 13,15,22 ... Needle valve 16 ... Sample gas inlet 17 ... Three-way valve (3 port 3 position) 171,172,173 ... Two-way valve 18 ... 6-way valve (6 port 2 position) 19 ... collection tube 20 ... heater 21 ... 3 way valve (3 port 2 position) 23 ... pump 24, 32 ... outlet 25 ... odor sensor 26 ... flow cell 33 ... control unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Taisei Kinoshita 1 Kuwabaracho, Nishinokyo, Nakagyo-ku, Kyoto, Japan Inside the Sanjo Plant, Shimadzu Corporation (72) Inventor Hiroshi Nakano 1 Shiwazu, Nishinokyokuwaharacho, Nakagyo-ku, Kyoto, Japan F-term in the Sanjo Plant (Reference) 2G046 AA01 BG02 BG07 CA09 EB01

Claims (1)

[Claims] 1. A gas concentrating means including a collection tube loaded with an adsorbent for adsorbing a sample component contained in a sample gas and releasing the sample component by heating, a sample component concentrated by the gas concentrating device. An odor measuring device comprising odor detecting means for detecting: a) a sample gas supply port to which a sample gas supply source is detachably connected; b) a carrier gas supply source for supplying a carrier gas; c) Flow path switching means for connecting the sample gas supply port, the carrier gas supply source, and the collection pipe to each other, and connecting the sample gas supply port and the collection pipe during gas enrichment to the collection pipe. The sample gas is allowed to flow to cause the sample components to be adsorbed by the adsorbent, and then the carrier gas supply source and the collection tube are connected to flow the carrier gas through the collection tube to drive out the residual sample gas, and the sample gas supply port And carrier A flow path switching means for connecting a gas supply source and discharging a carrier gas from a sample gas supply port.