JP3988675B2 - Odor measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an odor measuring apparatus that measures an odor component contained in a sample gas by using an odor sensor that is a kind of gas sensor, and in particular, there is a mixture of odorous components other than the original odor of the original purpose such as food and drink. In such a case, the present invention relates to an odor measuring apparatus suitable for distinguishing and evaluating them.
[0002]
[Prior art]
Conventionally, component analysis using a gas chromatograph mass spectrometer (GCMS) or the like has been the mainstream for measuring various index values relating to odor. However, in such component analysis, measurement takes time, skill is required for measurement, the types of signals obtained for samples are very many, and their analysis and interpretation are difficult, and sensory values based on human olfaction There are various problems such as no correlation.
[0003]
On the other hand, in recent years, an odor measurement apparatus using an odor sensor that responds to an odor substance has been developed (see, for example, Patent Document 1, Patent Document 2, and Non-Patent Document 1). In such an odor measurement apparatus, based on detection signals acquired by a plurality of odor sensors, various multivariate analysis processes such as cluster analysis and principal component analysis, or nonlinear analysis process using a neural network are performed, The separation distance of odors of a plurality of samples (whether or not they are in a close category) can be obtained.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-352088 [Patent Document 2]
JP 2002-22692 A [Non-Patent Document 1]
“Effect identification device FF-1”, [online], Shimadzu Corporation, [Search April 23, 2003], Internet, <URL: http : //www.an.shimadzu.co.jp/products/food/ff1.htm>
[0005]
[Problems to be solved by the invention]
However, since the selectivity of the odor sensor used in the current odor measuring device is not yet sufficiently high, a certain odor sensor responds not only to one type of odor but also to a plurality of types of odors. Therefore, for example, when you want to measure off-flavor mixed in orange juice, if the amount of off-flavor component is very small, it is masked by the strong smell of orange juice, which is the main component, and the off-flavor component is detected. It is very difficult to do.
[0006]
Generally, when it is desired to detect a small amount of an odorous component, a pretreatment for increasing the concentration of a component to be measured by concentrating a sample gas is useful. For example, in the heat desorption method (thermal desorption), a sample gas is circulated through a collection tube loaded with an adsorbent that adsorbs a component to be measured, and the component to be measured contained in the sample gas is adsorbed to the adsorbent. Then, after the component to be measured is sufficiently adsorbed, the temperature of the adsorbent is rapidly increased while flowing the carrier gas through the collection tube. As a result, the component to be measured that has been adsorbed is detached from the adsorbent in a short time, and is carried on the carrier gas to the odor sensor. By appropriately setting the temperature rise of the adsorbent, the flow rate of the carrier gas, etc., it is possible to supply the odor sensor with the measured component concentration considerably higher than the original sample gas.
[0007]
However, as described above, when a very small amount of off-flavor components are mixed in a large amount of orange juice, the main component of orange juice is also concentrated at the same time even if concentration processing is performed. The response of the odor sensor to the component becomes too large and the sensor output is saturated. That is, the main component becomes a background component, which prevents detection of off-flavor components.
[0008]
In addition, a method of concentrating only the off-flavor components without collecting the main component by selecting the type of adsorbent to be filled in the collection tube is conceivable, but the collection tube is replaced for each type of measurement target. In addition, it takes time and labor, and depending on the type of off-flavor component, it may pass through the main component without being collected by the adsorbent, and may not be measured properly.
[0009]
The present invention has been made in view of the above points, and the main purpose thereof is to separate the main component and off-flavor components, which are background components, regardless of the content thereof, for example, against the main components. An object of the present invention is to provide an odor measuring apparatus capable of accurately evaluating the content ratio of off-flavor components.
[0010]
[Means for Solving the Problems]
The present invention, which has been made to solve the above problems, includes a collection tube having an adsorbent that adsorbs a sample component contained in a sample gas and releases the sample component by heating, and a plurality of sample components for detecting the sample component. An odor detecting means having an odor sensor; and a sample gas that flows through the collection tube to adsorb the sample component to the adsorbent and then the sample component that is released from the adsorbent is introduced to the odor detecting means. In the odor measuring device comprising a flow path switching means for flowing a carrier gas to the collecting tube,
a) When the sample components collected in the adsorbent are separated, the temperature of the collection tube is raised stepwise to find different component separation temperatures for the main component and the off-flavor component in the sample . Preliminary measurement execution control means for performing preliminary measurement and storing the component desorption temperature;
b) When the sample components collected in the adsorbent are separated, the temperature of the collection tube is sequentially set to the component removal temperature stored in the preliminary measurement, while the odor detection means and the main component are different from odor. Main measurement execution control means for acquiring respective detection signals of the components ,
c) arithmetic processing means for calculating the ratio of the content of the main component and the off-flavor component in the sample based on the detection signal acquired in the main measurement;
It is characterized by having.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
In the odor measuring apparatus according to the present invention, measurement of a sample that is a measurement target is executed in two stages of preliminary measurement and main measurement. That is, the preliminary measurement execution control unit first causes the sample gas to flow into the collection tube, and then when the collection tube is heated to release the collected component, the heating temperature is rapidly increased to a high temperature. Instead, for example, the temperature is increased step by step from a predetermined lower limit temperature by a predetermined temperature step. Then, it is confirmed whether or not a detection signal by the odor detecting means can be obtained at each temperature in the temperature raising process, and the temperature at which the detection signal is obtained is stored as a component separation temperature. Generally, various components adsorbed on the adsorbent of the collection tube are detached from the adsorbent at a temperature determined for each component. Accordingly, different components are more likely to be detached from the adsorbent at different temperatures, and the separation of different components becomes higher as the temperature step during temperature rise is narrowed.
[0012]
For this reason, one or more component desorption temperatures stored when the predetermined upper limit temperature is reached correspond to various components in the sample, and components that desorb from the adsorbent at other temperatures. Can be determined to not exist. Subsequently, this measurement execution control means flows the sample gas to be measured through the collection tube, collects the sample components, and then heats the collection tube to release the collected components. Are sequentially set to the one or more component desorption temperatures. For example, if there are two component desorption temperatures, Ta and Tb (Ta <Tb), the temperature is rapidly increased from normal temperature to Ta first, and the temperature is maintained and the odor is detected and then Ta to Tb. Raise temperature rapidly. Then, the odor is detected again while maintaining the temperature. As a result, different components that depart from the collecting tube at each temperature Ta and Tb can be introduced into the odor detecting means in a concentrated state.
[0013]
In addition, since it is possible to change the degree of concentration of the component depending on the flow rate of the carrier gas that flows to the collection tube when the component is removed from the adsorbent, for example, the content is originally high and there is no need for concentration, or the concentration level is desired to be reduced Such a component may be controlled so as to increase the flow rate of the carrier gas when the component is released.
[0014]
The odor measuring apparatus according to the present invention separates a plurality of mixed components, and after sufficiently concentrating components whose contents are very small and difficult to detect as they are. , Smell detection can be performed. Therefore, for example, even when a large amount of main components and a minute amount of off-flavor components are mixed, the off-flavor components can be reliably detected without being affected by the main components. Evaluation can be performed with high accuracy.
[0015]
Further, in the odor measuring apparatus according to the present invention, although it is necessary to perform a preliminary measurement, it is only necessary to set the temperature for only the component contained in the sample during the main measurement. Therefore, when the types of components contained in a plurality of samples are the same, the preliminary measurement needs to be performed only once, so that the overall measurement efficiency can be improved by reducing the measurement time required for the main measurement. it can.
[0017]
Moreover , according to the odor measuring apparatus according to the present invention, even when a large amount of the main component, which is a background component, and a very small amount of the off-flavor component are mixed, it is high by separating the off-flavor component from the main component. Since it can detect with accuracy, the ratio of the content of the main component and the off-flavor component in the sample can be accurately determined.
[0018]
【Example】
Hereinafter, an odor measuring apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram centering on the gas flow path of the odor measuring apparatus of the present embodiment, FIG. 2 is a flowchart showing the procedure of the measuring operation in this apparatus, and FIG. FIG. 4 is a diagram showing an example of the temperature rise profile during the preliminary measurement of the apparatus and an example of the odor detection output corresponding thereto, and FIG. 5 is an example of the temperature rise profile during the main measurement of the apparatus and the odor detection output corresponding thereto. FIG.
[0019]
The odor measuring apparatus is roughly divided into a pretreatment unit for removing moisture contained in the sample gas and concentrating the sample component, and an odor detecting unit for detecting the sample component. The pre-processing unit alternatively uses a collection pipe 16 provided with a heater 17 for heating and a first gas flow path 14 connected to one end of the collection pipe 16 as a sample gas introduction port 10 or a sensor cell 21. The first valve 12 for connection to the exhaust gas and the second gas flow path 15 connected to the other end of the collection pipe 16 are selectively connected to the exhaust port 19 via the nitrogen gas supply port 11 or the pump 18. And a second valve 13 for performing the operation. The collection tube 16 is filled with, for example, a carbon-based adsorbent or other appropriate adsorbent 16a according to the sample component to be measured.
[0020]
The odor detector includes a sensor cell 21 having a plurality of odor sensors 21a therein. Here, the odor sensor 21a is an odor sensor that uses, as a sensitive film, a metal oxide semiconductor having different detection sensitivities for various odor components. However, the odor sensor is not limited to this and is a conventional odor sensor. Various known sensors can be used.
[0021]
Detection signals based on resistance changes between the electrodes of the plurality of odor sensors 21 a are digitized by the A / D converter 22 and then sent to the data processing unit 23 and the control unit 24. The data processing unit 23 has a function of identifying the quality and intensity of the odor based on these detection signals. The control unit 24 controls the operations of the first and second valves 12 and 13, the pump 18, the data processing unit 23, and the like according to a predetermined control program. The heating operation by the heater 17 is controlled in cooperation. The substance of the data processing unit 23 and the control unit 24 is a personal computer, and each function is achieved by operating a predetermined control / processing program on the computer.
[0022]
Next, an example of a typical measurement operation in this odor measuring apparatus will be described. When a sample to be measured is given, the control unit 24 controls each unit as follows to perform a preliminary measurement prior to the main measurement (step S1). Here, a sample in which a small amount or a trace amount of off-flavor components are mixed in a certain main component (for example, orange juice) is assumed.
[0023]
The controller 24 switches the first valve 12 so that the first gas flow path 14 is connected to the sample gas inlet 10 and collects the sample component, and the second gas flow path 15 is connected to the exhaust port 19. The second valve 13 is switched so as to be connected to the pump 18 and the pump 18 is operated (step S2). Then, as shown in FIG. 3 (A), the sample gas is sucked from a sample bag (not shown) attached to the sample gas inlet 10, and the sample gas passes through the collection tube 16 via the first valve 12, and further The gas is discharged from the exhaust port 19 through the second valve 13. At this time, the heater 17 is not energized (strictly speaking, the heater 17 is controlled so as to maintain the collection tube 16 at a constant temperature of 40 ° C., for example), and when the sample gas passes through the collection tube 16. Various sample components contained in the sample gas are adsorbed by the adsorbent 16a.
[0024]
Usually, the moisture contained in the sample gas is also adsorbed to the adsorbent 16a in the collection tube 16, and this moisture may adversely affect the subsequent measurement. Therefore, after allowing the sample gas to flow through the collection tube 16 for a predetermined time, the control unit 24 opens the sample gas inlet 10 and switches the second valve 13 to supply the second gas passage 15 with nitrogen gas. Connect to mouth 11. Dry nitrogen gas as a carrier gas is supplied to the nitrogen gas supply port 11 at a high gas pressure. Since the inlet gas pressure at this time is higher than the gas pressure of the sample gas inlet 10, the carrier gas passes through the collection tube 16 from the bottom to the top through the second valve 13 as shown in FIG. Then, it flows out from the sample gas inlet 10 through the first valve 12 to the outside. At that time, the water adsorbed on the adsorbent 16a in the collection tube 16 is volatilized in the dry nitrogen gas and carried to the outside, so that the moisture is removed while the sample components remain in the adsorbent 16a. (Step S3).
[0025]
Thereafter, the control unit 24 switches the first valve 12 to connect the first gas flow path 14 to the sensor cell 21. A carrier gas in which air (or oxygen) is slightly mixed with dry nitrogen gas is supplied to the nitrogen gas supply port 11 at a high gas pressure. As shown in FIG. 3C, the carrier gas passes through the collection tube 16 through the second valve 13 and flows to the sensor cell 21 through the first valve 12. The reason why air (or oxygen) is mixed slightly rather than pure nitrogen gas is because the odor sensor using a metal oxide semiconductor requires oxygen for the detection mechanism. When using a odor sensor, air and oxygen are not required.
[0026]
The control unit 24 starts energization of the heater 17 and controls the heater 17 so that the temperature of the collection tube 16 increases stepwise with a temperature rising profile as shown in FIG. 4C, for example. The temperature rise profile in Fig. 4 (C) increases the temperature by 20 ° C every 30 seconds from the temperature of 40 ° C. After reaching 160 ° C, the temperature rises to the maximum temperature of 220 ° C. is there. Various sample components adsorbed on the adsorbent 16a of the collecting tube 16 are generally separated and volatilized when the adsorbent 16a becomes high temperature, but the adsorptivity (adsorption power) is considerably dependent on the type of the component. For this reason, the temperature at which separation from the adsorbent 16a occurs depends on the type of the component, and some types are released at a relatively low temperature, and other types are released only at a high temperature. For this reason, when the temperature of the collection tube 16 is increased stepwise as described above, the various components adsorbed on the adsorbent 16a rapidly desorb from the adsorbent 16a when reaching the respective desorption temperatures. Then, the air is introduced into the sensor cell 21 along the carrier gas flow.
[0027]
When such a carrier gas containing a sample component passes through the sensor cell 21, the sample component is adsorbed to the sensitive film of the odor sensor 21a, and the electric resistance between the electrodes of the odor sensor 21a changes, and this change is taken out as a detection signal. Accordingly, if the temperature step of the stepwise temperature rise as described above is set to be appropriately small, each sample component is separated by the difference in temperature desorbed from the adsorbent 16a, and the odor sensor 21a has each sample component. A detection signal can be obtained (step S4). In order to improve the separability, the temperature step may be reduced. However, since the time required for the preliminary measurement becomes longer, it is preferable to appropriately determine the balance between the two.
[0028]
For a certain odor sensor 21a, when the sample does not contain an off-flavor component and consists only of the main component, the detection output is as shown in FIG. 4A, for example. That is, in this example, the detection output corresponding to the main component is obtained only during the period in which the temperature is 140 ° C. On the other hand, when the sample contains an off-flavor component, the detection output is as shown in FIG. In this case, in addition to the detection output corresponding to the main component that appears when the temperature is 140 ° C., the detection output corresponding to the off-flavor component appears when the temperature is 100 ° C. With respect to other temperatures at which no detection output appears, it can be determined that there is no component in the sample that desorbs from the adsorbent 16a at that temperature.
[0029]
Therefore, the control unit 24 determines the detection signal in the process of increasing the temperature, and if there is a change enough to determine that some component has been detected, the temperature data Tn (n = 1, 2,. ) And stored in the temperature data memory 25 (step S5). Therefore, for example, when the change as shown in FIG. 4A occurs, only the temperature T1 = 100 [° C.] is stored in the temperature data memory 25, and when the change as shown in FIG. 4B occurs. Two temperature data of T1 = 100 [° C.] and T2 = 140 [° C.] are stored in the memory 25. However, since this is a detection signal of one odor sensor 21a, in fact, all the temperature data that can be determined that any of the plurality of odor sensors 21a has a detection output is stored in the memory 25. And
[0030]
Thereafter, in order to perform the cleaning process, the control unit 24 further increases the energization current to the heater 17 to raise the adsorbent 16a in the collection pipe 16 to a high temperature, and completely removes dirt components and the like adhering to the adsorbent 16a. Eject (step S6).
[0031]
Thus, the preliminary measurement is completed, and the main measurement is performed after the temperature of the collection tube 16 is sufficiently lowered (step S7). In this measurement, various components contained in the sample to be measured are collected in the adsorbent 16a in the collection tube 16 by the processing in steps S8 and S9 similar to steps S2 and S3, and then undesired moisture is collected. Only remove.
[0032]
Subsequently, the control unit 24 sets a flow path in the same manner as the process of step S4 and starts energizing the heater 17. However, at this time, the temperature data Tn stored in the previous preliminary measurement is read from the temperature data memory 25, and the temperature is increased stepwise in accordance with the temperature data Tn, that is, T1 → T2 →. Step S10).
[0033]
For example, when two temperature data of T1 = 100 [° C.] and T2 = 140 [° C.] are stored in the temperature data memory 25 corresponding to the detection output described with reference to FIG. A temperature rising profile as shown in FIG. 5C is set. That is, the temperature of the collection tube 16 is rapidly increased from 40 ° C., which is a steady temperature, to 100 ° C. (T1), and the temperature is maintained for a predetermined time (approximately 1 minute in this example). To 140 ° C. (T2), the temperature of the collection tube 16 is rapidly increased, and the temperature is maintained for a predetermined time.
[0034]
During the period in which the temperature of the collection tube 16 is maintained at 100 ° C., the off-flavor component adsorbed by the adsorbent 16 a is released and introduced into the sensor cell 21. At this time, since the main component has not yet detached from the adsorbent 16a, the odor sensor 21a can obtain a detection signal for only the off-flavor component (see FIG. 5A). Moreover, since the off-flavor component adsorbed by the adsorbent 16a at this time is volatilized in the carrier gas in a short time, even if the content when contained in the first sample gas is very small, The content in is higher in each stage than this, and is easily detected by the odor sensor 21a. Note that the concentration rate of the off-flavor component (same as the main component) at this time can be controlled by the gas flow rate per unit time and the gas flow time.
[0035]
Next, during the period in which the temperature of the collection tube 16 is maintained at 140 ° C., the main component adsorbed by the adsorbent 16 a is detached and introduced into the sensor cell 21. At this time, since the off-flavor component has already been almost completely removed from the adsorbent 16a, the odor sensor 21a can obtain a detection signal for only the main component. In this way, various components contained in the sample to be measured can be separated, and each component can be adequately concentrated and detected. Moreover, since only the temperature necessary for component separation (100 ° C. and 140 ° C. in the example of FIG. 5) is set and the temperature is raised stepwise, the measurement can be performed efficiently.
[0036]
After acquiring the off-flavor component and main component detection signals in this way, the data processing unit 23 performs the following processing, for example. That is, when the odor sensor 21a is an oxide semiconductor, when the base resistance value is R0 and the resistance value at the peak of the signal is Rs, -log (Rs / R0) And the ratio (amount of off-flavor component / principal component) is calculated. Then, by normalizing this value, the variation in the sample amount for each sampling is canceled. Thereby, the amount of off-flavor components with respect to the main component can be accurately obtained. After performing the main measurement in this way, the same cleaning process as in step S6 is performed (step S11), and all the measurements are completed with the adsorbent 16a being cleaned.
[0037]
In the above embodiment, when measuring a certain sample, a preliminary measurement was performed first, and then a series of measurements were performed in the procedure of performing the main measurement. When it is desired to measure the odor intensity of a large number of samples, a preliminary measurement is first performed on one kind of sample to find the expulsion temperature Tn of all components including off-flavor components, and the temperature data is used. This measurement can be performed on all samples. Thus, the preliminary measurement is not necessarily required for each main measurement, and the preliminary measurement can be omitted if the temperature data usable for the main measurement is already stored in the temperature data memory 25.
[0038]
Moreover, the said Example is an example of this invention, Comprising: It is clear that a deformation | transformation, correction, or addition can be performed suitably in the range of the meaning of this invention.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram centering on a gas flow path of an odor measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a procedure of a measurement operation in the odor measuring apparatus according to the present embodiment.
FIG. 3 is an explanatory diagram of a gas flow during a measurement operation in the odor measuring apparatus according to the present embodiment.
FIG. 4 is a diagram illustrating an example of a temperature rise profile during preliminary measurement of the odor measuring apparatus according to the present embodiment and an odor detection output corresponding thereto.
FIG. 5 is a diagram showing an example of a temperature rise profile during the actual measurement of the odor measuring apparatus according to the present embodiment and an odor detection output corresponding thereto.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Sample gas introduction port 11 ... Nitrogen gas supply port 12, 13 ... Valve 14, 15 ... Gas flow path 16 ... Collection pipe 16a ... Adsorbent 17 ... Heater 18 ... Pump 19 ... Exhaust port 21 ... Sensor cell 21a ... Odor sensor 22 ... A / D converter 23 ... data processing unit 24 ... control unit 25 ... temperature data memory

Claims (1)

A collection tube containing an adsorbent that adsorbs a sample component contained in the sample gas and releases the sample component by heating, an odor detection means having a plurality of odor sensors for detecting the sample component, and a sample in the adsorbent A flow path switching means for flowing a carrier gas through the collection tube to introduce the sample component released from the adsorbent into the odor detection means after flowing the sample gas through the collection tube to adsorb components. In the odor measuring device provided,
a) When the sample components collected in the adsorbent are separated, the temperature of the collection tube is raised stepwise to find different component separation temperatures for the main component and the off-flavor component in the sample . Preliminary measurement execution control means for performing preliminary measurement and storing the component desorption temperature;
b) When the sample components collected in the adsorbent are separated, the temperature of the collection tube is sequentially set to the component removal temperature stored in the preliminary measurement, while the odor detection means and the main component are different from odor. Main measurement execution control means for acquiring respective detection signals of the components ,
c) arithmetic processing means for calculating the ratio of the content of the main component and the off-flavor component in the sample based on the detection signal acquired in the main measurement;
An odor measuring apparatus comprising:

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