JP2005189146A - Volatile sulfide sensor and detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simplified sensor system for detecting and discriminating a volatile sulfide (VSC) having a low concentration under the ppm order. <P>SOLUTION: This volatile sulfide sensor is equipped with a steam saturation vessel 3 into which a gas sample is introduced and wherein a saturated vapor pressure is maintained at a prescribed temperature, a measuring system 9 maintained at a higher temperature than the prescribed temperature, a sensor cell 6 provided in the measuring system and formed by arraying sensor elements 5 equipped respectively with an organic adsorption film, and a means for guiding the gas sample acquiring the saturated vapor pressure from the steam saturation vessel into the measuring system, to thereby impart thereto a relative humidity, and thereafter measuring a resonance frequency of the sensor elements. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  It is an object of the present invention to detect and discriminate sub-ppm level volatile sulfides in air with non-constant humidity in a volatile sulfide sensor and detection method, and more particularly a sensor for monitoring gas composition fluctuations. And the application to identify the mixing ratio of volatile sulfide, which is an important indicator for periodontal disease diagnosis.

  Volatile sulfur compound (VSC) is a component that is generated in large quantities in biogas processes, sludge treatment, landfill work, pulp industry, and livestock industry. Is a component.

  Conventionally, volatile sulfides of ppm or more can be detected by an electrochemical sensor and used. However, even if the concentration level of VSC is less than or equal to ppm, there are many substances that feel bad odor, and reports of bad odor damage to surrounding residents due to VSC leaking from facilities and the like are increasing. In exhaled breath, VSC is produced by degradation of methionine and cysteine, which are amino acids contained in cells and saliva proteins removed from the oral mucosa, and food residues, and by anaerobic bacteria in the oral cavity and plaque. Exists.

  Due to the recent increase in etiquette awareness, the number of people who are sensitive to bad breath has increased, and it is felt that bad breath is seen at a VSC concentration of 200 to 500 ppb. Therefore, there is a need for a technique for monitoring sub-ppm level VSC. Furthermore, even at the level that ordinary humans and dentists judge “no bad breath”, the number of self-odor patients who think that they have bad breath is increasing. Severe self-odor patients are mentally serious, and treatment that is psychologically alleviated by measuring their bad breath objectively and on a daily basis is effective. Thus, there is a need for a sensor technology that can easily detect a low concentration VSC at a sub-ppm level.

  Furthermore, the low-concentration VSC component contained in exhaled breath and the content ratio thereof are related to periodontitis. Periodontal disease is a serious disease that can cause loss of teeth as it progresses, and the maintenance of "healthy teeth" is closely related to Quality of Life. Hereditary periodontal disease also exists, and recently, with the change in Japanese dietary habits, the problem of an increase in the number of young periodontal disease patients as well as the elderly has emerged. However, periodontal disease is a disease that is difficult to detect at an early stage because it progresses chronically without subjective symptoms.

  On the other hand, it is known that the component of VSC produced by bacteria in the oral cavity is related to the progress of periodontal disease. As an apparatus for discriminating and detecting a sub-ppm level VSC component in exhaled breath, a gas chromatograph which is an analyzer has been conventionally used. In the measurement of components in exhaled breath, which is a sample with high humidity, in general, the exhaled air is once held in an adsorbent or cooled and concentrated, and after pre-treatment that takes time and effort, such as releasing moisture by dry gas purging, heating is performed. It is qualitatively and quantitatively determined by introducing the component to be measured into the chromatographic column after separation and detecting it with a detector.

As described above, since the VSC component having a low expiratory concentration is measured using an expensive and large gas chromatograph and a person having specialized knowledge requires measurement time, it is difficult to apply clinically. Therefore, a bad breath diagnosis device (Patent Document 1: Japanese Patent Application No. 13-52602 “Periodontal Diagnosis Device”) in which semiconductor sensor elements are arrayed and data processing by sensor signal neural network is combined has been proposed. Since the semiconductor-type sensor element does not have VSC type discrimination capability, the above-mentioned apparatus is statistically classified into a periodontal disease patient group or a healthy group using the sensor response to human breath as an index. Classify into: Therefore, the performance of the apparatus greatly depends on the quality and number of human groups sampled in advance, and is not directly related to the content ratio of the VSC component which is a periodontal disease progression index.
Japanese Patent Application No. 13-52602 "Diagnosis device for periodontal disease"

  An object of the present invention is to provide a simple sensor system that detects and identifies VSC having a low concentration of ppm or less. Since the humidity adjustment mechanism is incorporated, it is possible to measure a breath sample with a relative humidity as high as about 90% as it is, and since it has a configuration in which sensor elements having gas selectivity are arrayed, the concentration of sub ppm level A volatile sulfide sensor having a function of identifying a VSC component and a volatile sulfide detection method can be provided.

  In order to solve the above problems, a volatile sulfide sensor according to the present invention includes a water vapor saturation tank in which a gas sample is introduced and maintained at a saturated vapor pressure at a predetermined temperature, and a measurement maintained at a temperature higher than the predetermined temperature. System, a sensor cell provided in the measurement system and arrayed with a sensor element having an organic adsorption film, and the gas sample having a saturated vapor pressure in the water vapor saturation tank is introduced into the measurement system, And a means for measuring the resonance frequency of the sensor element after the relative humidity is reached.

  In the volatile sulfide detection method according to the present invention, an arrayed sensor element using an organic adsorption film is held in an atmosphere in which temperature and relative humidity are fixed, a sample gas is set to the temperature and relative humidity, The gas molecules are identified by using the difference in solubility of the sample gas component in the adsorption layer composed of two phases of the film molecules of the organic adsorption film and the adsorbed water component.

  Volatile sulfide that combines a sensor element made with a plasma organic thin film formed by sputtering using an organic solid material with an excellent organic gas concentrating function as a starting material and a humidity control mechanism based on the two-temperature method A sensor was developed. Further, as a sensor element array to be incorporated into the volatile sulfide sensor, a sensor array in which a plasma organic thin film having different selectivity to gas molecules belonging to VSC is combined is developed, and an identification method using the same Developed.

  It differs from the prior art in that VSC of ppm or less can be detected and identified only by an operation of introducing a gas sample into the sensor without a pretreatment process or complicated apparatus operation. Furthermore, a conventional sensor using an organic adsorption film controls the concentration of the adsorbed water component on the surface of the organic adsorbent film, and uses a system consisting of two phases of an organic film and an adsorbed water component as a gas adsorption layer. Is different.

  A sensor capable of detecting VSC, which is the main cause of bad breath of oral origin, from a concentration of ppm or less and correlating with the degree of progression of periodontal disease and producing a concentration ratio of methyl mercaptan and hydrogen sulfide was prepared. Since the product of the present invention has a humidity adjusting function, a sample in a high humidity state such as exhaled breath or other environmental samples can be introduced as it is and measured.

  By using the product of the present invention, the progress of periodontal disease and the malodor concentration in exhaled breath can be easily measured from the exhaled breath. Furthermore, since it is possible to identify a low-concentration VSC that is difficult to judge by human olfaction, it is expected that it will be possible to find an early periodontal disease patient. In addition, since it is a device that can be measured simply by sampling the breath into a bag and introducing or blowing it in, a daily check of a person with a periodontal disease gene, or the resistance of the whole body weakens like an inpatient Therefore, it is possible to easily check at the bedside about a person who is likely to have periodontal disease.

  The organic adsorption film can change the solubility at the molecular level by controlling the molecular structure of the film. Therefore, it is a sensor material suitable for organic gas identification with higher accuracy than a semiconductor or a metal-added semiconductor material used as a gas sensor material. Among organic adsorption films, plasma organic thin films synthesized with organic solid materials as starting materials have a large adsorption area and the mobility of the polymer main chain, so the ability to concentrate and distinguish low molecular weight volatile substances Is excellent. Therefore, it is a material capable of producing a highly sensitive gas sensor element.

  Plasma organic thin films produced from raw materials having a variety of different molecular structures can have different molecular selectivity by selecting the raw materials. On the other hand, when measuring samples with varying humidity, such as in an actual environment, or samples with high humidity, such as exhaled air, the plasma organic thin film also adsorbs water in the atmosphere, which is used to adsorb water molecules. There is a problem that the corresponding sensor response becomes a noise component. Therefore, as a conventional method for removing noise due to water components in the atmosphere, a method using an adsorbent and a dry purge, which has been used in an analysis using a gas chromatograph, is generally used.

  However, such a method for removing a water component in a sample has a risk of removing even a gas component to be analyzed or altering it. Therefore, in the present invention, the humidity environment in the sensor cell equipped with the sensor element is made constant, the state of the adsorbed water component on the surface of the organic film is made steady, and the adsorbing layer in gas sensing is a two-phase of the plasma organic thin film and the adsorbed water component The method used as a system was used.

The temperature and relative humidity of the sample introduced into the sensor cell including the sensor element having the plasma organic thin film as an adsorption film and the sensor cell are adjusted by the two-temperature method. In the two-temperature method, when air saturated with water vapor in a water vapor saturation tank having a constant temperature T ₀ is introduced into a thermostatic tank maintained at a temperature satisfying T> T ₀ , the relative humidity U is expressed by the following Eq1. Is being used.

U = (e _T0 / e _T1 ) × 100... Eq1
_{However, e T0,} e _T is the saturation vapor pressure of the temperature _{T 0} and _{T 1,} respectively. Further, the saturated water vapor pressure e _s depending on the temperature can be generally obtained by the following Goff-Gratch equation (Eq2).

_{Log (e s /1013.25) w =} 1.089830 × 10 (1-T tr /T)-5.25937(T/T tr) + 7.34872 × 10 -5 [1-10 (-9.16193 ^{) (1-T / Ttr)} ] + 1.10955 × 10 ⁻³ [10 ^{4.00990 (1-T / Ttr)} −1] −2.2195034... Eq2
However, T _tr is the triple point temperature of water (273.16 K), and T is the gas temperature. Eq2 uses a coefficient corresponding to ITS-90.

  The gas sample passes through the water vapor saturation tank and the heat exchange coil, so that it has the same temperature and relative humidity as the air in the sensor cell, and is introduced into the sensor cell. Therefore, the humidity fluctuation of the sample outside the sensor does not affect the humidity in the sensor cell and the state of the adsorbed water component on the plasma organic thin film.

  The adsorption layer in the sensor element in the sensor cell is composed of two phases of a plasma organic thin film and an adsorbed water component, and the two phases are in a steady state because the temperature and humidity are constant. Next, when a gas sample is introduced, this gas component dissolves into a system consisting of two phases of an organic film and an adsorbed water component. There are gas molecules adsorbed on the layer and gas molecules that are difficult to adsorb, and the gas molecules to be analyzed are each selected. A sensor system in which a sensor array in which a plurality of sensor elements having a plasma organic thin film having selectivity with respect to the type of VSC component is combined is manufactured, and a mixed gas component is discriminated from each sensor response signal from the sensor array. To construct.

An example of the volatile sulfide sensor which is the product of the present invention will be described with reference to FIG. The flow of the gas sample of the present invention having a humidity adjustment mechanism by the two-temperature method is indicated by an arrow 15 in FIG. The gas sample is introduced from the sample gas inlet 1 into the water vapor saturation tank 3 which is kept at a temperature T ₀ by the temperature control means 7 with a Peltier element. Water (liquid) 2 is provided in the water vapor saturation tank 3, and this water is kept at a temperature T ₀ by a temperature control means 7 with a Peltier element.

Next, the sample gas is introduced into a thermostat 9 held at a constant temperature higher than that of the water vapor saturation tank 3, passes through the heat exchange coil 4 in the thermostat (measurement system) 9, and the temperature in the thermostat 9. It is heated to (measurement temperature) _{T 1.} A sensor element 5, the temperature of the gas sample when it reaches the sensor cell 6 which is held in the measurement temperature T ₁ of Peltier element with a temperature controller 7 is allowed to warm to T _1, the gas sample relative humidity as determined by Eq1 It becomes. The gas sample is sucked by the pump 11 attached downstream of the sensor cell 6, and the flow rate of the sample gas is controlled by the flow rate control valve 8 and exhausted 12.

  The frequency of the gas sample is measured by a frequency measuring circuit 17 and analyzed by a personal computer 19. In the figure, 13 is a thermocouple for measuring the temperature in the water vapor saturation tank 3 and the thermostat 9, 9 is a humidity sensor, 10 is information on the thermocouple 13, etc. A control board 18 for controlling the heat exchange coil 4 and the temperature control means 7 is a power source.

When the output of the relative humidity sensor 16 installed after the pump 11 of the sensor cell 6 is monitored when T _{0 is set} to 50 ° C. and T _{1 is set} to 20 ° C., the room air (relative humidity 97 %) Was introduced into the volatile sulfide sensor according to the present invention, no clear noise response was observed in the plasma organic thin film sensor element 5.

  In the present invention, the gas sample passes through the water vapor saturation tank 3 before reaching the sensor cell 6. In order to investigate whether the saturated water vapor present in this part affects the gas sample itself, for the same person's exhalation sample, prepare samples before and after introduction to the sensor (that is, the exhalation sample recollected from the exhaust 12), The hydrogen sulfide and methyl mercaptan concentrations contained were analyzed by gas chromatography. As a result, it was confirmed that both the original breath sample and the breath sample collected after the introduction of the volatile sulfide sensor (the sensor is not provided in the sensor cell) contain 90 ppb hydrogen sulfide and 2 ppb or less methyl mercaptan. It was shown that hydrogen sulfide having solubility in water can be measured by the volatile sulfide sensor according to the present invention.

  The plasma organic thin film uses D-phenylalanine (D-Phe), polyethylene (PE), and polychlorotrifluoroethylene (PCTFE) as target materials, and a quartz resonator (AT cut, fundamental vibration frequency 9 MHz) as a substrate, and high-frequency sputtering. It was produced by the method. The sensor element array using the plasma organic thin film shows a response to VSC at a sub ppm level and shows a different response for each type.

  A 100 ppb hydrogen sulfide diluted with dry air and a 30 ppb methyl mercaptan sample were introduced into the sensor at a flow rate of 180 to 200 mL min-1 to determine basic response characteristics. In the time change of the response of the D-Phe membrane sensor and the PE membrane sensor (FIG. 2), as the time elapses after the VSC sample is introduced at the time of ↑ (upward arrow), the D-Phe membrane sensor and the PE membrane sensor The tendency that the resonance frequency change response per unit time increases is shown.

  This indicates that multilayer adsorption occurs when hydrogen sulfide and methyl mercaptan are adsorbed on the D-Phe film and the PE film. Further, the magnitude Δf of the sensor response at the same time after the start of the adsorption measurement is Δf (D-Phe membrane sensor)> Δf (PE membrane sensor) for hydrogen sulfide, whereas Δf when measuring methyl mercaptan. (D-Phe film sensor) <Δf (PE film sensor).

  Thus, the D-Phe film sensor and PE film sensor produced by the plasma process have different affinity for hydrogen sulfide and methyl mercaptan, which have a difference of one hydrogen and one methyl group in the molecular structure. Have the ability.

  Further, the sensor element can be repeatedly used by performing a return process for desorbing the gas component from the sensor element. At time ↓ (downward arrow) in FIG. 2, introduction of the reference gas, that is, air not containing VSC, into the sensor system is started. Although the hydrogen sulfide and methyl mercaptan gas components are strongly adsorbed to the plasma organic thin film and sensor components, the sensor response does not tend to increase even when a reference gas is flowed, but from the D-Phe film and PE film. No sudden decrease in sensor response due to desorption is confirmed. Therefore, by increasing the temperature of the thermostatic chamber 9 and promoting the desorption of the adsorbed hydrogen sulfide or methyl mercaptan from the film, the sensor recovery process can be shortened.

  Next, sensor response characteristics when the relative humidity in the sensor cell is controlled to 30% are shown. Under humidity control, the surface of the D-Phe film and PE film is a stable system in which a certain amount of water is adsorbed. The response to the hydrogen sulfide and methyl mercaptan mixed gas in FIGS. 3 and 4 is based on Langmuir type adsorption, which is different from FIG. 2A measured in dry air for both the D-Phe membrane sensor and the PE membrane sensor. A sensor response curve is obtained.

  However, when the hydrogen sulfide concentration is high (FIG. 3, [methyl mercaptan concentration] / [hydrogen sulfide concentration] = 0.16), Δf (D-Phe film sensor)> Δf (PE film) Sensor), when the methyl mercaptan concentration is high (FIG. 4, [methyl mercaptan concentration] / [hydrogen sulfide concentration] = 6), Δf (D-Phe film sensor) <Δf (PE film sensor). According to the results. Therefore, the crystal oscillator type sensor using the plasma organic thin film has a function of concentrating VSC gas molecules and discriminating them at the molecular level even in a state where the adsorbed water component is retained.

  The concentration ratio of hydrogen sulfide and methyl mercaptan, which are VSCs during expiration, has a correlation with the depth of the periodontal pocket, which is a diagnostic indicator of the degree of progression of periodontal disease. When the concentration of methyl mercaptan is 1/6 or less of the hydrogen sulfide concentration, in periodontal disease diagnosis, the periodontal pocket depth is 3 mm or less, and it is judged as mild periodontal disease. On the other hand, when methyl mercaptan is 3 times or more of the hydrogen sulfide concentration, there is a possibility of suffering from moderately advanced periodontal disease, and when it is 6 times or more, it may be severe. For this reason, a sensor system that can determine the concentration ratio of hydrogen sulfide and methyl mercaptan is desired.

  Therefore, FIG. 4 shows the result of measuring the response to the mixed gas sample in which the ratio of the concentration of methyl mercaptan and hydrogen sulfide was 1: 6 (that is, [methyl mercaptan concentration] / [hydrogen sulfide concentration] to 0.16). . The total concentration of VSC is about 300 ppb, which is equivalent to the hydrogen sulfide concentration in FIG. 3, and is comparable to the concentration judged to be “with bad breath”. The magnitude of the resonance frequency response is much smaller than the response to hydrogen sulfide, and the response of the D-Phe film sensor is about 1/10. The response curve trend for the mixed sample is different from that for the sample containing only hydrogen sulfide, and is similar to that for measuring hydrogen sulfide and methyl mercaptan in a dry air environment. A response curve is obtained.

  From this result, methyl mercaptan is adsorbed on the PE film and D-Phe film in a competitive manner with water molecules. Focusing on the magnitude of the response of the different sensor elements, the magnitude of the sensor response Δf at the same time for a sample in which methyl mercaptan and hydrogen sulfide are mixed at a ratio of 1: 6 is Δf (D-Phe film sensor) <Δf This is a tendency similar to the response to methyl mercaptan in measurement under dry air. Thus, it is shown that the sensor element using the plasma organic thin film has molecular selectivity in the state where the adsorbed water component is retained.

  Therefore, the magnitude of the sensor response when the mixing ratio of methyl mercaptan and hydrogen sulfide was changed was compared. Here, after the start of the adsorption measurement, the response widths at 15 minutes and 30 minutes are compared. When sampling exhalation and introducing it into a sensor system, there are bags called odor bags or Tedlar bags as a simple sampling device to be used. These capacities are generally 3 to 10 L, and the flow rate in this sensor system is 180 to 200 mL min-1, so that the measurement time by sampling corresponds to 15 to 30 minutes. Therefore, the magnitudes of responses at 15 minutes and 30 minutes were compared in FIG. The total concentration of VSC is 300 ppb. When the mixing ratio of methyl mercaptan and hydrogen sulfide is different, it is confirmed that the response pattern of the sensor array is different.

  Comparing the cases where [methyl mercaptan concentration] / [hydrogen sulfide concentration], which are mild and severe in periodontal disease diagnosis, are 0.16 and 6, the ratio of the magnitude of the response of the D-Phe film sensor and the PE film sensor is different. . Further, when the [methyl mercaptan concentration] / [hydrogen sulfide concentration] is compared between 1 and 6, the response of the PE film sensor and the response of the PCTFE film sensor having water repellency characteristics are compared. The ratio of magnitude to the response is different. However, the PCTFE membrane sensor hardly responded to methyl mercaptan in a dry air environment. The negative response width of the PCTFE membrane sensor tends to decrease as the mixing ratio of methyl mercaptan increases, indicating the characteristics of the sample gas component.

  As described above, it was confirmed that a sensor array composed of a D-Phe film sensor, a PE film sensor, and a PCTFE film sensor can obtain a response corresponding to the mixing ratio of methyl mercaptan and hydrogen sulfide, which is an index for periodontal disease diagnosis. It was.

  Response features were extracted from the sensor response curve, and a database for identifying the mixture ratio of methyl mercaptan and hydrogen sulfide was created. Measure the sensor response to mixed samples of hydrogen sulfide and methyl mercaptan with different total concentrations and mixing ratios, extract the time change rate of each sensor response (that is, the slope of the response curve) as a response feature, and based on the response feature Principal component analysis was performed.

  By treating the curve and difference of the sensor response as described above numerically, the mixture ratio of the mixed gases having different total concentrations is identified from the sensor response. Therefore, the sensor response to the mixed sample of hydrogen sulfide and methyl mercaptan having different total concentrations and mixing ratios is measured, and in the sensor responses obtained by measuring these mixed samples, the D-Phe film sensor, PE film sensor, PCTFE film sensor The time change rate of each response (that is, the slope of the response curve) was used as the numerical value of the response characteristic.

That is, the time change rate of the response of the D-Phe film sensor, the PE film sensor, and the PCTFE film sensor with respect to the total concentration c1 at the mixing ratio m1 is expressed as τ _D-Phe (m1c1), τ _PE (m1c1), τ _PCTFE ( m1c1), a mixed sample of hydrogen sulfide and methyl mercaptan with a total concentration c1 and a mixing ratio m1 corresponds to a sensor response characterized by these three numerical values. For another mixed sample with a mixing ratio of m2 and a total concentration of c2, the response is expressed as a combination of τ _D-Phe (m2c2), τ _PE (m2c2), τ _PCTFE (m2c2), and other numerical values. Become. When a certain relationship exists between the combination of these numerical values and the mixing ratios m1 and m2, these relationships are defined in advance. This is a database in the odor sensor. When a mixed sample with an unknown mixing ratio and total concentration is measured, the numerical set that is a feature extracted from the sensor response to the unknown sample is compared with the database, and the unknown sample is close to the sample at which mixing ratio. Determine if it has a value.

  Therefore, the numerical set to be stored in the database must represent the mixing ratio difference. That is, the correlation with the mixing ratio of the numerical value set represents the discrimination performance of the odor sensor.

  Therefore, the mixed sample was actually measured, a numerical set that is a response feature amount obtained from the sensor response at that time was obtained, and then the relationship between the numerical set and the mixing ratio was obtained. The mixing ratio and concentration of the measured samples are as follows. [Methyl mercaptan concentration] / [hydrogen sulfide concentration] is 6, the total concentration is 72 ppb, 110 ppb, 140 ppb, [methyl mercaptan concentration] / [hydrogen sulfide concentration] is 1, and the total concentration is 44 ppb, 88 ppb, When [methyl mercaptan concentration] / [hydrogen sulfide concentration] is 0.16, the total concentration is 52 ppb, 98 ppb, 140 ppb. This total concentration level ranges from “no bad breath” to a sensitive person who feels “a bad breath” a little according to the human sense of smell.

  The relationship with the mixing ratio of the numerical sets obtained by actual measurement can be determined from the dispersion of the Euclidean distance between the numerical sets. A method for visually expressing this is principal component analysis.

  Principal component analysis is a general numerical analysis method for obtaining a numerical axis that maximizes the variance due to the Euclidean distance between numerical sets. FIG. 6 shows a set of numerical values obtained from actual measurement values, with the axis having the largest variance as the principal component 1 and the axis with the next largest variance as the principal component 2, each axis serving as an axis. In FIG. 6, the shape of the plot represents the value of [methyl mercaptan concentration] / [hydrogen sulfide concentration] of the mixed gas sample, and also shows a plot for each total concentration of methyl mercaptan and hydrogen sulfide. The plot of ○ is [methyl mercaptan concentration] / [hydrogen sulfide concentration] is 6, the total concentration is 72 ppb, 110 ppb, 140 ppb, and □ is [methyl mercaptan concentration] / [hydrogen sulfide concentration] is 1 and the total concentration is 44 ppb, 88 ppb, and ● indicate the total concentrations of 52 ppb, 98 ppb, and 140 ppb when [methyl mercaptan concentration] / [hydrogen sulfide concentration] is 0.16. Plots with different shapes are circled and exist in different areas. Thus, the relationship between the numerical set obtained from the sensor response and the [methyl mercaptan concentration] / [hydrogen sulfide concentration] ratio can be formed on the map obtained by principal component analysis. It was shown that the sensor array has a sensitivity and a function capable of obtaining an index for periodontal disease diagnosis from bad breath having a VSC concentration of sub ppm level.

  In the above embodiment, a quartz crystal resonator is used as means for measuring the gas molecule adsorption amount of the sensor element. However, a micro cantilever, a surface acoustic wave waveguide device, or the like can also be used.

  A sensor element having a gas selectivity in which a humidity adjustment mechanism is incorporated and a plasma organic film is formed on the surface of a crystal resonator is arrayed. Detection and identification of low concentration VSC (volatile sulfide) of ppm or less is possible.

The figure which shows a sensor system structure. The figure which shows the sensor response in a dry environment. (A) is hydrogen sulfide and (b) is methyl mercaptan. The figure which shows the sensor response to hydrogen sulfide in relative humidity 30% (20 degreeC) environment. The figure which shows the response to the gas sample made into [methyl mercaptan density | concentration] / [hydrogen sulfide density] = 0.16 in relative humidity 30% (20 degreeC) environment. Comparison of sensor response to mixed gas. The figure which shows the principal component analysis result of mixed gas.

Explanation of symbols

1 Sample gas inlet 2 Water (liquid)
DESCRIPTION OF SYMBOLS 3 Steam saturation tank 4 Heat exchange coil 5 Sensor element 6 Sensor cell 7 Temperature control means 8 Flow control valve 9 Thermostatic chamber 10 Control board 11 Pump 12 Exhaust 13 Thermocouple 14 Electrical wiring 15 Gas flow path 16 Humidity sensor 17 Frequency measurement circuit 18 Power supply 19 Personal computer

Claims (11)

A water vapor saturation tank maintained at a saturated vapor pressure at a predetermined temperature, a gas sample is introduced, a thermostatic tank maintained at a measurement temperature higher than the predetermined temperature, and an organic adsorption film provided in the thermostatic tank. The sensor cell in which the sensor elements are arrayed and the gas sample having a saturated vapor pressure in the water vapor saturation tank are introduced into the thermostatic bath, heated to the measurement temperature to a predetermined relative humidity, And a means for measuring the amount of gas molecule adsorbed on the sensor element. 2. The volatile sulfide sensor according to claim 1, wherein the water vapor saturation tank includes a temperature control means for maintaining the water in the water vapor saturation tank at a predetermined temperature. The thermostat is provided with a heat exchange coil for heating the sample gas introduced from the water vapor saturation tank to have the same temperature as the sensor element in the thermostat and the same relative humidity. The volatile sulfide sensor according to 1 or 2. The volatile sulfide sensor according to any one of claims 1 to 3, wherein the thermostatic chamber includes a temperature control means for maintaining the sensor element at a predetermined temperature. The volatilization according to any one of claims 1 to 4, wherein the sample gas passes through the water vapor saturation bath and the thermostatic bath while being controlled in flow rate by a pump provided outside. Sulfide sensor. 6. The volatile sulfide sensor according to claim 1, wherein a plasma organic thin film formed by a plasma process using an organic solid material is used for the organic adsorption film. The volatile sulfide sensor according to claim 1, wherein the organic adsorption film is any one of D-phenylalanine, polyethylene, and polychlorotrifluoroethylene. The volatile sulfide sensor according to any one of claims 1 to 7, wherein the means for measuring the amount of adsorbed gas molecules is a crystal resonator, a microcantilever, or a surface acoustic wave waveguide device. The arrayed sensor elements using the organic adsorption film are held in an atmosphere in which the temperature and relative humidity are fixed, the sample gas is set to the temperature and relative humidity, and 2 of the molecules of the organic adsorption film and the adsorbed water component. A method for detecting volatile sulfides, wherein gas molecules are identified using a difference in solubility of the sample gas component in an adsorption layer composed of two phases. Passing the sample gas through a water vapor saturation tank maintained at a predetermined temperature, thereby bringing the sample gas into a water saturated state, heating the sample gas, and maintaining the temperature and relative humidity of the sensor element; The volatile sulfide detection method according to claim 9, comprising a step of measuring a gas molecule adsorption amount of the sensor element. 11. The volatilization according to claim 9, wherein the sensor element is formed by forming the organic adsorption film on a crystal resonator, and the gas adsorption amount is detected by measuring a resonance frequency response of the sensor element. To detect functional sulfide.

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