JP4472893B2 - Odor measurement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to how to measure the odor, in particular, it relates to how to measure the gas containing much moisture and volatile odor components expiratory like smell (e.g. halitosis).
[0002]
[Prior art]
The odor measuring device is basically a gas sensor, and quantitatively measures various components contained in a gas sample to be measured. Sensors for such odor measuring devices include those that use changes in the resistance value of metal oxide semiconductors and conductive polymers, and a membrane that incorporates a sensitive substance in a lipid membrane or an organic membrane is attached to a quartz resonator. Various types of devices have been devised, such as those using the change in vibration frequency, and further using the surface acoustic wave by attaching the sensitive film on the SAW device.
[0003]
In any type, the gas sensor performs measurement by adsorbing a target component, but not only the odor component but also moisture is adsorbed in many cases. Therefore, when used as an odor measuring device, conventionally, moisture has been previously removed from the measurement target gas and then sent to the gas sensor.
[0004]
[Problems to be solved by the invention]
Conventionally, gas chromatographs (hereinafter referred to as “GC”) and sensory tests have been used in combination for the measurement of bad breath. The sensory test has a feature that it is possible to comprehensively evaluate bad breath substances, but there are problems in measurement accuracy and quantification. On the other hand, the measurement by GC has the advantage that the odor can be quantified, but in the case of bad breath, the measurement components have been exclusively measured from hydrogen sulfide (H ₂ S), methyl mercaptan (CH ₃ SH), dimethyl sulfide (( Since it is limited to three types of volatile sulfides (hereinafter referred to as “VSC”) of CH ₃ ) ₂ S), there is a problem that it is difficult to approach comprehensive bad breath evaluation.
[0005]
It is said that a lot of VSC is contained in exhaled breath with strong bad breath. However, as described above, the conventional odor measuring device is premised on removing moisture in advance, so that the VSC is removed during the moisture removing process. There was also a problem that a part was removed at the same time and the sensitivity was lowered.
[0006]
The present invention has been made in order to solve such problems, and the object of the present invention is to have high reproducibility even if the gas has a high content of moisture and volatile components such as bad breath. An object of the present invention is to provide an odor measurement method capable of giving a measurement result close to the sensory test result.
[0007]
[Means for Solving the Problems]
Hey measurement methods Ru engaged to the present invention was made in order to solve the above problems includes a odor component collecting material having a predetermined water trapping capacity, a sample is passed through a gas sample into said odor component adsorbent introduced Means, heating means for heating the odor component collecting material, means for feeding dry inert gas to the odor component collecting material, and separation from the odor component collecting material by feeding the inert gas An odor measuring method using an odor measuring device comprising:
When measuring a gas sample containing moisture and odor components, after a predetermined amount of the gas sample is passed through the odor component adsorbent, drying without performing heating of the odor component collecting member by said heating means the inert gas the gas sample is disengaged from the odor component collecting material by feeding to the odor component collecting material sent to the analysis unit, and performs the measurement by the analyzer.
[0008]
The “inert gas” used here only needs to be inert to the odor sensor, and includes an inert gas in a narrow sense such as argon gas and helium gas, as well as nitrogen gas. In some cases (depending on the type of odor sensor), methane gas or the like can be used.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
In the odor measuring method according to the present invention, after a sample is supported on the odor component collecting material, the sample is sent to the odor sensor at high speed by a dry inert gas without heating. Thereby, almost all of the odor component contained in the sample is sent to the odor sensor and measured. Here, although moisture is also sent to the odor sensor at the same time, the amount of gas sample to be passed through the odor component collecting material is determined by the amount of moisture that can be collected by the odor component collecting material ( By setting this to be equal to or greater than the moisture collection capacity of the odor component collection material, the amount of moisture carried by the odor component collection material becomes a constant value (moisture collection capacity). Therefore, by setting the measurable amount of the odor sensor to be more than that, the odor sensor can measure the target odor component and can easily correct the influence of moisture.
[0010]
The measuring object of the odor measuring method according to the present invention is not limited to gas. When the sample is an aqueous solution, or when the sample is a solid containing a lot of moisture, the gas sample generated by heating (or bubbling in the case of an aqueous solution) also contains a lot of moisture. In the odor measuring method according to the invention, these can also be analyzed.
[0011]
In addition, in the analysis part used in the method according to the present invention, the metal oxide semiconductor sensor, the conductive polymer film sensor, etc., which are used in a normal odor measuring apparatus, can be used.
[0012]
Odor measurement how according to the present invention is particularly suitable for measuring halitosis. That is, the strong halitosis breath are abundant volatile sulfide (VSC) is, when this is measured in a conventional way, odor component contribution is larger as bad breath during water removal also will be removed at the same time In many cases, the results were not consistent with the results of the sensory test. Because the way according to the present invention with respect to it can be analyzed without missing even odor components volatile, by the analysis method, it is possible to produce the results of the sensory test and sufficiently cope with measurement results.
[0013]
【Example】
In order to confirm the effect of the odor measurement method according to the present invention, the result of measurement by this method was compared with the result of measurement by gas chromatograph and the result of sensory evaluation by using breath as a sample.
[0014]
First, the configuration of the apparatus used for carrying out the method according to the present invention and the measurement method will be described. FIG. 1 is a configuration diagram centering on a gas flow path of the odor measuring apparatus of the present embodiment. In FIG. 1, 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 ) are first and second flow rate control units 13 such as a mass flow controller, respectively. , 16 and molecular sieve filters 14 and 17 for removing impurities are branched into two channels, a first nitrogen gas channel 12 and a second nitrogen gas channel 15. The sample flow channel connected to the sample suction port 18 via the PTFE membrane filter 19 for dust removal and the first nitrogen gas flow channel 12 are selectively connected to a six-way valve (6-port two-position valve) 21 by a three-way valve 20. Connected to port a. The second nitrogen gas flow path 15 is connected to the port d of the six-way valve 21. A collection tube 22 provided with a heater 23 for heating is connected between the port c and the port f of the hexagonal valve 21. The collection tube 22 is filled with, for example, an activated carbon adsorbent or other appropriate collection material according to the odor component to be measured.
[0015]
The port b of the six-way valve 21 is selectively connected by a three-way valve 24 to a flow path that passes through the pump 25 and the flow meter 26 or a flow path that does not pass, and both are connected to the exhaust port 27. The port e of the hexagonal valve 21 is connected to a flow cell 28 provided with a plurality (six in this example) of odor sensors 29, and its downstream outlet is connected to an exhaust port 30. The odor sensor 29 is an odor sensor that uses a metal oxide semiconductor as a sensitive film and has different characteristics in detection sensitivity with respect to various odor components. The hexagonal valve 21 and the flow cell 28 are installed in a thermostatic chamber 36, and the thermostatic chamber 36 is controlled by a temperature adjusting unit 37 so as to reach a predetermined temperature.
[0016]
In the tank 33, the air sucked from the air suction port 31 by the pump 32 is compressed and stored. The tank 33 is connected to the inlet of the flow cell 28 via a third flow rate control unit 34 and an activated carbon filter 35 for removing impurities. Thus, an appropriate amount of air can be mixed with the sample flowing into the flow cell 28. Note that pure oxygen gas may be mixed instead of air. If pure oxygen gas is used, the volume to be mixed can be greatly reduced as compared with air. Therefore, the ratio of dilution of odor components is small, which is advantageous in improving the sensitivity of detection by the odor sensor 29.
[0017]
The detection signals of the six odor sensors 29 are input to the signal processing unit 40, respectively. The signal processing unit 40 includes an A / D conversion unit 41 that converts an analog detection value into a digital value for each odor sensor 29, an odor classification processing unit 42, and an odor index calculation unit 43. The odor classification processing unit 42 and the odor index calculating unit 43 can realize their functions by executing predetermined software on a personal computer, for example. The odor index calculated in the signal processing unit 40 is displayed on the display unit 39. The control unit 38 controls the three-way valves 20 and 24, the six-way valve 21, the pumps 25 and 32, the heater 23, the temperature adjustment unit 37, the signal processing unit 40, and the like as described later according to a predetermined program.
[0018]
In this embodiment, a metal oxide semiconductor sensor is used as the odor sensor 29. However, the present invention is not limited to this, and a sensor using a conductive polymer may be used. In that case, since it is not necessary to supply air or oxygen to the flow cell 28, in the structure shown in FIG. 1, the component for mixing air with the gas which flows into the flow cell 28 can be omitted.
[0019]
Next, a method for measuring bad breath using the odor measuring apparatus will be described. Here, the measurement was performed under the following three conditions.
(a) Normal conditions: The conventional measurement method.
(1) Heat the trapping material to a low temperature (40 ° C).
(2) After the sample is collected by the collection material in the collection tube 22, the collection material is dry purged (dried).
(3) The collection tube 22 is connected to the flow cell, nitrogen gas is passed through the collection material, the odor component is sent to the flow cell 28, and measurement is performed by the odor sensor 29.
[0020]
(b) Top note condition: the method according to the present invention.
(1) Heat the trapping material to a low temperature (40 ° C).
(2) Collect the sample with a collecting material. Do not dry purge.
(3) The collection tube 22 is connected to the flow cell 28 without heating the collection material.
(4) Nitrogen gas is allowed to flow through the collection material at high speed to send the odor component to the flow cell 28 and measurement is performed by the odor sensor 29.
[0021]
(c) Deep note conditions
(1) The collector is rapidly heated to a high temperature (100 ° C or higher).
(2) After collecting the sample with the collecting material, the collected material is dry purged (dried).
(3) The collection tube 22 is connected to the flow cell 28, nitrogen gas is passed through the collection material, the odor component is sent to the flow cell 28, and measurement is performed by the odor sensor 29.
[0022]
First, a method for measuring bad breath in the case of normal conditions and deep note conditions will be described.
[0023]
(I) Collection of exhalation Exhalation of the subject is collected under the following conditions. The subject breathes with his nose for 30 seconds with his mouth closed, and then breathes into the sachet of a predetermined volume through the mouth. The amount of exhaled air at this time is set so that the total amount of moisture is not less than the moisture collecting capacity of the collecting material in the collecting tube 22. The smell bag filled with exhaled breath is attached to the sample inlet 18.
[0024]
(Ii) The collection material is heated to 40 ° C. under normal conditions and to 100 ° C. under deep note conditions, for example. The control unit 38 switches the three-way valve 20 so that the sample inlet 18 and the port a of the six-way valve 21 are connected, and switches the three-way valve 24 so that the port b of the six-way valve 21 is connected to the pump 25. . Further, the hexagonal valve 21 is switched so that the connection state shown by the broken line in FIG. Then, the breath sample in the odor bag is sucked from the sample suction port 18, relatively large solid suspended matters such as dust are removed by the membrane filter 19, and introduced into the collection tube 22 through the three-way valve 20 and the six-way valve 21. (From left to right in FIG. 1), the gas is further discharged from the exhaust port 27 through the six-way valve 21, the three-way valve 24, the pump 25, and the flow meter 26. At this time, heating by the heater 23 is not performed.
[0025]
When the sample passes through the collection tube 22, the odor component and moisture contained in the sample are adsorbed by the adsorbent (collection material) in the collection tube 22. At the time of this suction, the control unit 38 controls the suction force of the pump 25 so that the detection value by the flow meter 26 becomes a predetermined constant value so that the flow time of the sample becomes a predetermined value.
[0026]
(Iii) Replacement of gas in the collection tube When the above-mentioned circulation time has elapsed, the control unit 38 switches the three-way valve 20 to connect the first nitrogen gas flow path 12 to the port a of the six-way valve 21 and the three-way valve 24. The port b of the six-way valve 21 is directly connected to the discharge port 27 by switching. Then, instead of the sample, the nitrogen gas supplied from the nitrogen gas container 10 passes through the first nitrogen gas flow path 12-the three-way valve 20-the six-way valve 21-the collection tube 22-the six-way valve 21-the three-way valve 24, It is discharged from the discharge port 27. As a result, the sample gas remaining inside the flow path including the collection tube 22 is pushed out by the nitrogen gas. At this time, since heating by the heater 23 is not performed, the odor component previously adsorbed by the adsorbent remains as it is. On the other hand, since nitrogen gas is extremely dry, most of the water with weak adsorption characteristics and water adhering to the inner wall of the flow channel is volatilized into the nitrogen gas and carried away to the outside. Dehumidification up to is achieved.
[0027]
(Iv) Introduction of sample into odor sensor Thereafter, the control unit 38 switches the hexagonal valve 21 to the connection state indicated by the solid line in FIG. Then, a second nitrogen gas flow path 15-a hexagonal valve 21-a collection pipe 22-a hexagonal valve 21-a flow cell 28-an exhaust port 30 is formed. In this state, the heater 23 is energized to heat the collection tube 22 rapidly (for example, at a temperature rise rate of about 10 ° C./second). The heating at this time is raised to 220 ° C. under normal conditions. As a result, the odor component adsorbed by the adsorbent in the collection tube 22 is released from the adsorbent, and rides on the nitrogen gas flowing in the opposite direction (from right to left in FIG. 1) before the flow cell. Carried to 28.
[0028]
The air stored in the tank 33 is adjusted to an appropriate flow rate by the third flow rate controller 34, and after the unwanted components that cause measurement disturbance are removed by the activated carbon filter 35, the measurement gas that flows into the flow cell 28. It is mixed in. Since the oxygen gas is contained in the air, the oxygen gas flows into the flow cell 28 together with the odor component, the oxygen gas molecules are adsorbed on the sensitive film made of the metal oxide semiconductor, and oxidized between the odor component molecules. Causes a reduction reaction. As a result, the conductivity of the odor sensor 29 changes, and the electrical resistance between the electrodes changes. A detection signal due to this resistance change is sent to the signal processing unit 40.
[0029]
During the measurement period, the six-way valve 21 and the flow cell 28 and the flow path connecting them are maintained at a constant temperature (for example, about 40 ° C.) slightly higher than the room temperature by the temperature adjusting unit 37. As a result, it is possible to reduce the influence of the odor sensor 29 due to fluctuations in the ambient temperature, and it is possible to prevent the high-boiling-point compound from adhering to the inner wall of the flow path and the like so that the detection sensitivity is not stable.
[0030]
(V) Cleaning of the odor sensor If the odor component adsorbed by the adsorbent of the collection tube 22 is sufficiently removed as described above, the control unit 38 again causes the hexagonal valve 21 to be shown by a broken line in FIG. It switches to the connection state shown, and raises the temperature of the thermostat 36 to a predetermined temperature by the temperature control part 37. As a result, clean nitrogen gas flows through the flow cell 28. When the temperature of the odor sensor 29 rises, the odor components and other impurities adsorbed on the sensitive film are easily separated and are exhausted from the exhaust port 30 on the nitrogen gas. As a result, the sensitive film of the odor sensor 29 is recovered, and the odor component can be detected again.
[0031]
The above description is for the normal condition and the deep note condition. However, in the case of the top note condition, the above-mentioned process (iii) “replacement of gas in the collection tube” is omitted. That is, the moisture of the sample (exhaled breath) in the collection tube 22 is maintained as it is, but since the moisture has been broken through, the amount is constant. Further, in the process of (iv) “introducing the sample into the odor sensor”, when the sample is sent to the flow cell 28, the heater 23 is not heated, and the sample containing the odor component and moisture is detached from the adsorbent only by nitrogen gas. Let
[0032]
The measured value of each component measured by the odor sensor 29 is sent to the odor separation processing unit 42 and the odor index calculation unit 43 via the A / D converter 41. The processing performed in the signal processing unit 40 including these will be described with reference to the flowchart of FIG.
[0033]
First, the sample introduced as described above is measured, and six channel detection outputs from the six odor sensors 29 are acquired (step S1). Since each of the six odor sensors 29 has different selectivity and response characteristics, for example, a large detection output can be obtained from a certain odor sensor with respect to a certain odor component, and from other odor sensors at all. It is possible that a detection output cannot be obtained.
[0034]
FIG. 3 is an example of a radar graph showing the distribution of the detection output of each odor sensor (channel). In general, when the outputs of all sensors increase, it is considered that the intensity has increased with the same odor quality. If the ratio of sensor outputs changes, it is determined that the quality has changed. A plurality of such odor categories and typical (typical) radar graph patterns are obtained by experiments and stored in a memory built in the odor classification processing unit 42 of the signal processing unit 40.
[0035]
At the time of sample measurement, the odor separation processing unit 42 receives the 6-channel detection output converted into a digital signal by the A / D conversion unit 41, creates a radar graph as described above, and most of the stored patterns Check for similarities. Based on the result, the category of the odor of the sample is determined (step S2). When it is clear that the sample is limited to a certain kind of smell such as bad breath, the determination of the category of this smell can be omitted.
[0036]
After that, the odor index calculating unit 43 calculates the odor index P by the following equation using the classification result of the odor category and the 6-channel detection output (step S3).
P = a · S1 + b · S2 + c · S3 + d · S4 + e · S5 + f · S6 + g
Here, Sn is the detection output of the nth (n = 1 to 6) channel, and a to g are coefficients.
[0037]
The coefficients a to g in the above formula use different values for each category of odor, but when the sample is limited to bad breath, constant values are used. The coefficients a to g are obtained in advance by experiment for each category of odor and are stored in a memory built in the odor index calculating unit 43. The calculated odor index P is displayed on the display unit 39 (step S4).
The above is the method for measuring bad breath by the odor measuring apparatus of FIG.
[0038]
Measurement by gas chromatograph (GC) was performed under the following conditions. Have the subject breathe with the nose only for 30 seconds with the mouth closed, and then collect 10 ml of air in the mouth with a gas tight syringe. Three kinds of VSCs were measured as hydrogen sulfide (H ₂ S), methyl mercaptan (MESH), and dimethyl sulfide (DMS). These measured concentrations were used as comparison data with other methods after logarithmic conversion. The reason why logarithmic transformation was performed was that preliminary experiments revealed that the correlation with the sensory evaluation value was relatively high compared to the case where logarithmic transformation was not performed.
[0039]
The sensory test was performed under the following conditions. As in the case of the odor measuring apparatus, the subject's breath was collected by breathing through the nose with the mouth closed for 30 seconds, and then breathing into the odor bag of a predetermined volume. The sampled samples were evaluated by 4 panelists with numerical values of 0 to 5, and the average value of the evaluation values of 4 samples for one sample was used as the sensory evaluation value of the sample.
[0040]
These three kinds of tests (5 kinds including three kinds of test methods of the odor measuring apparatus) were performed on the breath samples of 41 subjects, and the results were compared. FIG. 4 is a graph comparing the results of GC with the results of sensory evaluation. The horizontal axis is the sensory evaluation value of each sample (average value of four people), and the vertical axis is a regression equation calculated from the measurement results of three types of VSC components H ₂ S, MESH, and DMS, and the equation is used. The sensory evaluation prediction value of each sample is calculated. The correlation coefficient between the two is not so high as 0.401, and the GC predicted value tends to vary as the sensory evaluation value increases.
[0041]
FIG. 5 is a graph comparing the results of the odor measuring apparatus with the results of sensory evaluation. The horizontal axis is the sensory evaluation value (average value of four people) of each sample, and the vertical axis is the value predicted for the sensory evaluation of each sample by the prediction formula similarly created from the measurement result by the top note condition of the odor measuring device. is there. This one shows a fairly high correlation with a correlation coefficient of 0.718. That is, it was confirmed that the measurement of bad breath by the method according to the present invention (top note condition) relatively well coincided with the sensory evaluation value.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an odor measuring apparatus used for carrying out the present invention.
FIG. 2 is a flowchart showing a procedure for calculating an odor index by the odor measuring apparatus.
FIG. 3 is an example of a radar graph showing a distribution of detection output of each odor sensor (channel) of the odor measuring apparatus.
FIG. 4 is a graph comparing a sensory evaluation predicted value by a gas chromatograph with an actual sensory evaluation result.
FIG. 5 is a graph comparing a sensory evaluation prediction value calculated using a result of measuring a sample with an odor measuring apparatus (top note condition) and an actual sensory evaluation result.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Constant pressure valve 12 ... 1st nitrogen gas flow path 13 ... 1st flow control part 14 ... Molecular sieve filter 15 ... 2nd nitrogen gas flow path 16 ... 2nd flow control part 17 ... Molecular sieve filter 18 ... Sample inlet 19 ... Membrane Filter 22 ... Collection tube 23 ... Heater 28 ... Flow cell 29 ... Odor sensor

Claims (3)

Odor component collection material having a predetermined moisture collection capacity, sample introduction means for passing a gas sample through the odor component collection material, heating means for heating the odor component collection material, and odor component collection In the odor measuring method using an odor measuring device comprising means for feeding a dry inert gas to a material, and an analysis unit for measuring a component separated from the odor component collecting material by feeding the inert gas There,
When measuring a gas sample containing moisture and odor components, after a predetermined amount of the gas sample is passed through the odor component adsorbent, drying without performing heating of the odor component collecting member by said heating means the inert gas is disengaged to said gas sample from said odor component collecting material by feeding to the odor component collecting material sent to the analysis unit, odor measuring method characterized by performing the measurement in the analytical section . 2. The odor measuring method according to claim 1, wherein the gas sample containing moisture and odor components is exhaled air, and the bad breath in the exhaled air is measured. It is the smell measuring method of Claim 1 or 2, Comprising: The quantity of the gas sample passed through the said smell component collection material is more than the water collection capacity | capacitance of this smell component collection material, and the moisture content contained there An odor measuring method characterized by comprising:

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