JP4478773B2 - Sensor for detecting bad smell of sulfide with high sensitivity - Google Patents

Description

  The present invention relates to a sulfide measuring method and a measuring apparatus capable of detecting sulfide contained in a gas with high sensitivity.

  Various substances are known as malodorous substances recognized as unpleasant odors by human olfaction. Typical malodorous substances in living environments such as homes include ammonia, sulfides, organic acids, aldehydes, and the like. Many of these are also designated as specific malodorous substances in the Malodor Control Law.

  Sulfide is a general term for sulfur (S) and compounds in which elements on the positive side of sulfur are bound. For example, methyl mercaptan, methyl sulfide, hydrogen sulfide and the like are applicable. Sulfide is the most familiar malodorous substance known as a causative agent of bad breath (methyl mercaptan) or as a rotten odor of food or one of odor components of feces and urn (hydrogen sulfide). In addition, some sulfides are not only substances that cause malodors, but also substances that are harmful to humans at high concentrations. For example, hydrogen sulfide is irritating to mucous membranes in humans at a concentration of 50 ppm (Parts Per Million = 1 / 1,000,000) or more, and is lethal at concentrations of 1000 ppm or more.

For the above reasons, it is considered that knowing the concentration of sulfide in the environment is important in securing and maintaining a comfortable and safe living environment and working environment. Therefore, various sulfide measuring devices have been commercially available, and methods for detecting sulfides and sulfur represented by Patent Documents 1 to 3 and inventions of devices or sensors are disclosed.
JP-A-7-43358 JP 2000-325790 A JP2006-23256 JP 2001-255296 A Supervised by Yukichi Ishiguro (1997), latest deodorization technology collection, NTS. J. et al. Christopher Love, L. A. Estroff, J.M. K. Kriebel, R.A. G. Nuzzo, G.M. M.M. Whitesides (2005) Self-Assembled Monolayers of Thiolates on Metals as a Form of Nanotechnology, Chemical Review, 105: 1103-1169. Nagata Kazuhiro, Handa Hiroshi (1998) Experiments on real-time analysis of biological material interactions, Springer Fairlake Tokyo. Toyoi Moriizumi, Takamichi Nakamoto, (1997) Sensor Engineering, Shosodo.

  However, when the conventional general-purpose sulfide measuring device including the above-described invention is used, most of them have a detection limit of 0.05 ppm of sulfide concentration, and even if it is a relatively high sensitivity device, 1 ppb (Parts Per Billion = 1 billionth) was the limit. However, the detection limit of the concentration of sulfide by human olfaction is said to be about 100 ppt in the case of methyl mercaptan, for example (Parts Per Trilion = 1/1 trillion) (Non-Patent Document 1). It surpasses that of sulfide measuring equipment. That is, there is a problem that the conventional sulfide measuring instrument for general use may not be able to detect a sulfide having a concentration that can be detected by humans.

  The problem to be solved by the present invention is to develop an ultrasensitive sulfide measuring method comparable to human sulfide detection sensitivity, and to develop a general-purpose sulfide measuring device using the method, and solve the above problems. It is.

  In order to solve the above-mentioned problems, the present inventors have developed a measurement method that dramatically increases the detection sensitivity of sulfides present in gas by utilizing the high adsorptivity to sulfides of metals. In addition, we succeeded in obtaining highly accurate and stable measurement results by using a metal filter. The following invention described in the present application has been completed based on such research and development, and is provided as means for solving the above problems.

  In the first invention, the sulfide in the measurement gas is removed by a metal filter, the sulfide removal step to make the sulfide-removed gas, the sulfide-removed gas is brought into contact with the surface of the metal body, and the surface polarization control method is used. A background measurement step for measuring the degree of adsorption of molecules in the sulfide-removed gas to the metal body surface, and a sulfide-removed incomplete gas that does not remove sulfide in the measurement gas is brought into contact with the metal body surface, thereby surface polarization. A total gas measurement step of measuring the degree of adsorption of molecules in the sulfide-removed gas by the control method on the surface of the metal body, and a degree of adsorption of molecules in the sulfide-removed gas measured by the total gas measurement step; Sulfidation comprising: a sulfide quantification step for quantifying sulfide contained in the measurement gas from the difference between the degree of adsorption of molecules in the sulfide-removed gas measured by the background measurement step To provide a measurement method.

  2nd invention provides the sulfide measuring method as described in said 1st invention which replaced with the said surface polarization control method and used the surface plasmon resonance measuring method.

  3rd invention provides the sulfide measuring method as described in said 1st invention which replaced with the said surface polarization control method and used the quartz-crystal vibrator micro balance method.

  A fourth invention is an apparatus for measuring sulfides contained in the air, and introduces a measurement gas into a measurement unit described later, and removes sulfides in the measurement gas arranged in the introduction pipe. A metal filter part that can be inserted and removed, a measurement part that contacts the gas introduced from the introduction pipe with the surface of the metal body, and measures the degree of adsorption of molecules in the gas onto the metal body surface, and the metal filter part Sulfide measurement comprising: a calculation unit that quantifies the sulfide contained in the measurement gas from the difference between the measurement result of the introduced gas and the measurement result of the gas introduced without passing through the metal filter unit Providing equipment.

  A fifth invention is the sulfide measuring device according to the fourth invention, wherein the measurement unit has surface polarization control means for detecting the degree of adsorption of molecules in the gas on the metal body surface by a surface polarization control method. provide.

  A sixth invention is the sulfide measuring device according to the fourth invention, wherein the measurement unit has SPR measurement means for detecting the degree of adsorption of molecules in the gas on the surface of the metal body by a surface plasmon resonance measurement method. provide.

  According to a seventh aspect, in the sulfide measurement according to the fourth aspect, the measurement unit has QCM measurement means for detecting the degree of adsorption of molecules in the gas on the surface of the metal body by a quartz crystal microbalance measurement method. Providing equipment.

  An eighth invention is an apparatus for measuring sulfides contained in the air, and includes a first introduction pipe for introducing a measurement gas into the first measurement section described later, and a measurement gas disposed in the first introduction pipe. A metal filter part for removing the sulfides of the gas, a gas introduced from the first introduction pipe is brought into contact with the surface of the metal body, a first measurement part for measuring the degree of adsorption of the gas molecules on the metal body surface, The second introduction tube for introducing the measurement gas into the second measurement section to be described later, and the gas introduced from the second introduction tube are brought into contact with the metal body surface as they are, and the degree of adsorption of molecules in the gas to the metal body surface is determined. Sulfidation having a second measurement part to be measured, a common calculation part for quantifying sulfide contained in the measurement gas from the difference between the measurement result of the first measurement part and the measurement result of the second measurement part An object measuring device is provided.

  A ninth invention is the eighth invention, wherein the first measurement unit and the second measurement unit have surface polarization control means for detecting the degree of adsorption of molecules in the gas on the metal body surface by a surface polarization control method. A sulfide measuring apparatus as described is provided.

  A tenth aspect of the present invention is the sulfurization according to the eighth aspect, wherein the first measurement unit and the second measurement unit have SPR measurement means for detecting sulfide adsorbed on the surface of the metal body by a surface plasmon resonance measurement method. An object measuring device is provided.

  The eleventh invention is the eighth invention, wherein the first measurement unit and the second measurement unit have QCM measurement means for detecting sulfide adsorbed on the surface of the metal body by a quartz crystal microbalance measurement method. A sulfide measuring apparatus is provided.

  According to the sulfide measuring method of the present invention, detection is possible even if the concentration of sulfide is several to several tens of ppt. Thereby, it is possible to provide a sulfide measuring apparatus having a detection sensitivity comparable to or exceeding the sulfide detection sensitivity by human olfaction.

  The best mode for carrying out each invention will be described below with reference to the drawings. However, the present invention is not limited to these embodiments, and can be carried out in various modes without departing from the scope of the invention.

  The first embodiment mainly relates to claims 1 to 3. The second embodiment mainly relates to claims 4 to 7. Further, the third embodiment mainly relates to claims 8 to 11.

<< Embodiment 1 >>

<Embodiment 1: Overview>
The first embodiment relates to a sulfide measurement method. The sulfide measuring method of the present embodiment is a method that utilizes the property that sulfides have high adsorptivity to metals. That is, in the method of this embodiment, first, a sulfide-removed gas obtained by removing sulfides contained in a measurement gas by a metal filter and a sulfide-removed incomplete gas that is not subjected to the treatment are respectively contained in molecules. Is measured by a surface polarization control method, a surface plasmon resonance measurement method, or a quartz resonator microbalance method. And it is the method of quantifying the sulfide in measurement gas from the difference of the measured value of said two gas. According to the sulfide measuring method of this embodiment, sulfide in the air can be detected at a level comparable to or exceeding the human olfactory detection sensitivity.

<Embodiment 1: Configuration>
FIG. 1 is an example of a flowchart of each step of the sulfide measuring method in the present embodiment. As shown in this figure, the sulfide measuring method of this embodiment includes a sulfide removed gas measuring step (S0101) for measuring a gas from which sulfide is removed, and a total gas measuring step for measuring a gas from which sulfide is not removed. (S0102) and a sulfide determination step (S0103) for obtaining a difference between the measurement values obtained in the two steps. Hereinafter, each process will be described.

  ((Sulfide-removed gas measurement process))

  The “sulfide-removed gas measurement step” (S0101) is a step of measuring the degree of adsorption of molecules contained in the gas on the metal body surface after obtaining the sulfide-removed gas from the measurement gas. The sulfide-removed gas measurement step can be further subdivided into a sulfide removal step (S0104) and a subsequent background measurement step (S0105). Hereinafter, these two steps will be described.

  (Sulfide removal process)

      I. Definition

  The “sulfide removal step” (S0104) is a step of removing sulfide in the measurement gas with a metal filter to obtain a sulfide-removed gas.

  “Measurement gas” refers to a gas to be measured by the sulfide measurement method of the present embodiment.

  The “sulfide” is as described in the “background art”. The sulfide referred to in the present application refers to those in a gaseous state or an aerosol state at ordinary temperature. This is because the present application is a method or apparatus for measuring airborne sulfides. Examples of the sulfide in a gaseous state or an aerosol state at normal temperature include methyl mercaptan, hydrogen sulfide, methyl sulfide, and methyl disulfide.

  The “metal filter” refers to a metal filter, a filter whose surface is entirely or partially made of metal, or a filter made of a metal salt capable of adsorbing sulfide.

  “Sulfide-removed gas” refers to a gas obtained by passing through the metal filter and from which sulfide contained in the measurement gas has been removed.

      II. About the purpose of each process and each component

  The purpose of the sulfide removal step is to obtain a sulfide-removed gas from which sulfide has been removed from the measurement gas. Sulfides have a high adsorptivity to metals. Therefore, in the sulfide removal step, utilizing the property, the measurement gas is passed through a metal filter to adsorb and remove sulfides in the measurement gas, thereby achieving the object.

  The metal type of the metal filter is not particularly limited. This is because the sulfide is known to have high adsorptivity to any metal as described above. For example, the adsorption energy of thiol (mercaptan: R-SH, R is an alkyl group), which is one of sulfides, and gold (Au) is said to be 209 kJ / mol (Non-patent Document 2).

  The metal filter does not have to be made entirely of metal, but may be in a state where metal atoms are exposed on the filter surface. This is because the metal filter adsorbs sulfides in the passing measurement gas on its surface. Therefore, it suffices if all or part of the surface of the filter is covered with metal. For example, the case where the core part is polyvinyl chloride and the metal is vapor-deposited on the surface is mentioned. The metal filter may be in the form of a metal salt that can adsorb sulfide.

  The metal filter preferably has a large metal surface area. For example, a wool-like structure of metal fibers, a multi-layer structure of metal films made of metal fibers, or a particulate structure can be used. This is because the measurement gas passing through the metal filter can sufficiently contact the metal surface.

  In order for the metal filter to sufficiently adsorb the sulfide contained in the measurement gas, it is only necessary to have a predetermined surface area. As an example, when the sulfide concentration in the measurement gas is 0.1 ppm or less, it passes through the surface area of a metal filter in which steel wool (diameter of about 100 μm) is filled in a tube having a diameter of 1 cm and a length of 2 cm. Almost 100% of sulfides in the gas can be adsorbed. However, if it is expected that the concentration of sulfide in the measurement gas is as high as 100 ppm, there is a possibility that a sufficient amount of sulfide cannot be adsorbed by the metal surface area of the metal filter. In such a case, the metal surface area may be increased, or the measurement gas may be repeatedly passed through the metal filter several times.

  By the way, in the gas of general living environment like indoor air, the substance which has the adsorptivity to a metal other than sulfide can exist. However, it is rare that a substance comparable to the metal adsorption power of sulfide exists. Examples of general substances having metal adsorptivity other than sulfides present in gas include ammonia and hydrocarbons (alcohols, methane). These substances can be present in a relatively high concentration in the measurement gas, but their adsorption power for metals is very weak compared to that of sulfides. For example, the gold (Au) adsorption energy of methane is 6.28 kJ / mol. This is only about 1/33 of the adsorptive power of the aforementioned mercaptan. Therefore, even if a large amount of a metal-adsorbing substance other than sulfide is present in the measurement gas, they are only slightly adsorbed by the metal filter, and most pass through the metal filter. On the other hand, most of the sulfide is adsorbed by the metal filter even if only a very small amount is present in the measurement gas. Therefore, the sulfide-removed gas can be understood as a gas from which almost all sulfides contained in the measurement gas and a part of metal adsorbing substances other than sulfides have been removed. However, in a special environment such as a chemical factory, there is a possibility that a high metal-adsorbing substance comparable to sulfide exists at a high concentration. In the measurement gas under such a special environment, most of the sulfide and the metal adsorbing substance other than the sulfide are removed by the metal filter. In this case, an error that cannot be ignored may occur in the measurement value only by the measurement method of the present embodiment. Therefore, when measuring a gas in such a special environment, high-precision sulfide measurement is insufficient only with the method of this embodiment, and combined use with a gas chromatography method and other general-purpose gas sensor measurement methods is not possible. Necessary.

  (Background measurement process)

      I. Definition

  The “background measurement step” (S0105) is a method in which the sulfide-removed gas obtained in the sulfide removal step is brought into contact with the surface of a metal body, and the surface polarization control method, surface plasmon resonance measurement method, or quartz crystal micro This is a step of measuring the degree of adsorption of molecules in the sulfide-removed gas on the surface of the metal body by a balance method.

  The “metal body” means a molecule that adsorbs a molecule having an adsorptivity to a metal in a gas on the surface, and at least the surface thereof is composed of a metal. The metal body corresponds to a sensor unit for detecting sulfides and the like contained in the measurement gas in the present embodiment.

  “Contacting the sulfide-removed gas with the surface of the metal body” means not only causing the gas to directly contact the surface of the metal body, but also causing molecules contained in the gas to react widely on the surface of the metal body. Therefore, the contact with the gas may be indirect. For example, after the sulfide-removed gas is passed through the liquid and molecules contained in the gas are dissolved or taken into the liquid, the liquid may be brought into direct contact with the surface of the metal body.

  “Molecules in the sulfide-removed gas” refer to molecules of various substances contained in the sulfide-removed gas.

  The “degree of adsorption of molecules in the sulfide-removed gas to the metal body surface” refers to the degree of binding of molecules contained in the sulfide-removed gas to the metal body surface. The degree of coupling is expressed as a measurement value obtained by a surface polarization control method, a surface plasmon resonance measurement method, or a quartz crystal microbalance method. The surface polarization control method, surface plasmon resonance measurement method, and quartz crystal microbalance method will be described later.

      II. Purpose and configuration

  The purpose of the background measurement process is to obtain a reference value for the measurement gas. In the background measurement step, the sulfide-removed gas obtained in the sulfide removal step is brought into contact with the metal surface, and the degree of adsorption of molecules contained in the gas is measured. The measured value is used as a reference value for the measurement gas.

  As described above, in the sulfide-removed gas obtained through the metal filter, there are metal adsorbing substances other than sulfides that are not adsorbed by the metal filter. Such a substance is adsorbed by contacting the metal body. As described above, since the metal adsorption power of these substances is very weak, even if a large amount is present in the sulfide-removed gas, only a very small amount is adsorbed on the metal body. However, it cannot be denied that these substances cause measurement errors in measuring sulfides. Therefore, in the background measurement step, this problem is solved by measuring the sulfide-removed gas in order to take into account substances that can be adsorbed to metal bodies other than sulfide, and using the measured value as a reference value.

  The function of the metal body is to adsorb molecules contained in the sulfide-removed gas and the sulfide-removed incomplete gas described later on the metal surface. The degree of molecules adsorbed on the surface of the metal body is measured by any one of the measurement methods of surface polarization control method, surface plasmon resonance measurement method, and quartz crystal microbalance method described later.

  The shape of the metal body may be a rod shape, a plate shape, a thin film shape, a wire shape, or the like, but which shape is determined by the measurement method. For example, when measurement is performed using the surface plasmon resonance measurement method or the quartz crystal microbalance method, the metal body is preferably formed into a thin film in terms of the measurement structure. However, when the measurement is performed using the surface polarization control method, the metal body may have any shape of a rod shape, a plate shape, a thin film shape, or a wire shape.

  Metal species frequently used as metal thin films and electrodes are determined by the method for measuring molecules adsorbed on the surface of the metal body. For example, gold (Au) or silver (Ag) is generally used for the metal thin film of the surface plasmon resonance measurement method, and gold (Au) is generally used for the electrode of the crystal resonator microbalance method. However, the sulfide that is the measurement object of the present embodiment has very high adsorptivity for any metal as described above. Therefore, it is not necessary to be trapped by commonly used metal species, and any metal species may be used. However, depending on the metal type, corrosion may proceed due to a bond such as sulfide. Use of such a metal species on the surface of the metal body is not so preferable for accurate measurement of sulfide. In particular, when the purpose is to reuse a metal body, the degree of progress of corrosion increases as the number of uses increases, which is inconvenient. Therefore, it is preferable that the metal species constituting the surface of the metal body is a highly stable noble metal that does not easily corrode against sulfide bonds. Desirably, the metal species constituting the surface of the metal body is composed of gold (Au) or platinum (Pt).

  The metal body surface may not be chemically modified with an antibody or a functional group. This is because the sulfide measurement method of the present embodiment is characterized by adsorbing substances such as sulfide that can be directly bonded on the surface of the metal body and measuring those substances.

  The metal body should not be in contact with the outside air until it is brought into contact with the sulfide-removed gas or the sulfide-removed gas that is the gas to be measured. This is because molecules other than those contained in the gas to be measured are not adsorbed on the surface of the metal body before measurement. As a method for preventing the surface of the metal body from coming into contact with the outside air, for example, a method for isolating the metal body from the outside air by providing a sealable air chamber in the measurement unit where the metal body is disposed as described in Embodiment 2 can be mentioned. In order to keep the surface of the metal body clean when the metal body is installed in the air chamber, the metal body should be installed in a clean room or after being installed in the air chamber by heat from a laser or the like. What is necessary is just to clean the surface. The air chamber is evacuated using a vacuum pump or the like connected to the air chamber until a sulfide-removed gas or a sulfide-removed gas is introduced, or a predetermined gas cylinder or the like is installed from a gas cylinder. Gas may be filled into the air chamber via the gas introduction pipe. The predetermined gas refers to a gas that does not react directly with a metal, such as an inert gas. However, when the base atmosphere is air such as room air, the above-described strictness is not required for the metal body. In that case, the metal body may be installed in the air chamber in the atmosphere, and the air chamber may be filled with the air. The metal adsorbing substance contained in the atmosphere can be bonded to the surface of the metal body, but the response value at that time may be based, that is, 0 value.

  Hereinafter, the surface polarization control method, the surface plasmon resonance measurement method, or the crystal resonator microbalance method will be described. Any one of these three measurement methods may be used in the background measurement step, but these may be used in combination in order to quantify the sulfide more accurately and with high accuracy.

  A. Measurement method of molecules adsorbed on metal surface using surface polarization control method

  The “surface polarization control method” is a measurement method for extracting information on a substance adsorbed on an electrode by dynamically controlling the surface polarization of one electrode surface using an electrochemical impedance measurement method. That is, the measurement method can determine the substance adsorbed on the electrode from the electrochemical impedance pattern of each electrode potential.

(1) Measurement conditions, etc. In the surface polarization control method, three electrodes of a working electrode, a reference electrode, and a counter electrode are used as in the conventional electrochemical impedance measurement method. The working electrode corresponds to the metal body of the present embodiment, and is an electrode necessary for measuring the electrode potential and calculating the electrochemical impedance. The reference electrode is an electrode necessary for measuring or controlling the potential of the working electrode. The counter electrode is an electrode for energization with the working electrode. The reference electrode and the counter electrode have an auxiliary function for the metal body in the present embodiment. These electrodes are immersed in a reference solution that is an electrolyte when measuring the electrode potential.

  The electrochemical impedance is calculated from a voltage value between the working electrode and the reference electrode and a current value supplied between the working electrode and the counter electrode to obtain the voltage. In order to control the voltage between the working electrode and the reference electrode, a potentiostat or the like is generally used.

  In the surface polarization control method, the electrochemical impedance when a voltage is applied to the working electrode at a predetermined frequency at each stage while the electrode potential is swept in multiple steps within a predetermined range by immersing the electrode in a reference solution. calculate. Although the “predetermined range” is not limited, it is usually performed within a range of ± 1V. “Multi-stage” means that the selected predetermined range is the step width of the isobaric potential. The step width is normally 0.05V, but is not limited to this value. Moreover, time for measuring electrochemical impedance at each step is required. This time width is usually in the range of 0.001 second to 10 seconds. “Sweep” refers to dynamically controlling the electrode potential. In order to perform the sweep, the potentiostat is controlled using an oscillator or the like. Sweep can be performed either in the positive direction in which the electrode potential is increased or in the reverse direction in which the electrode potential is decreased. At the time of electrochemical impedance measurement, the step width and the time width can be appropriately changed in each direction. The voltage applied to the working electrode may be in the range of 100 mHz to 100 kHz in terms of AC frequency, and the AC amplitude may be in the range of 0.1 mV to 1 V. Note that the impedance of the reference solution is measured under the assumption that it converges to 0 at a frequency where the impedance of the electrode is high. For example, the impedance obtained when a voltage having an AC frequency of 1 kHz and an amplitude of about 0.01 mV is applied may be the impedance of the solution.

(2) Polishing the electrode It is preferable to remove impurities by polishing the metal surface before measurement. This is because the adhesion of impurities to the metal surface causes an undesired current to flow during potential measurement, and a desired measurement value cannot be obtained. In particular, when the working electrode is reused, it is desirable to perform the pretreatment. Polishing may be performed in accordance with a method generally used in electrochemical measurement. For example, after polishing for 5 seconds with a 0.1 μm diameter alumina abrasive, ultrasonically clean with distilled water, and further blow-clean the surface with nitrogen gas.

(3) Pre-scan It is preferable to perform pre-scan before the start of measurement in order to stabilize the impedance of the electrode. The pre-scan may be swept at a high speed several times in the reference solution. The number of pre-scans is usually in the range of 10 to 30 times. The electrode voltage range is set to be 1.1 to 1.5 times wider than the measurement range. This is for performing electrochemical cleaning of the electrode surface. In addition, since the sweep is performed at high speed, the potential step width of each step is made lower than that at the time of measurement. For example, if the measurement time is 0.05V, it may be performed at 0.02V.

(4) Method for adsorbing molecules on the surface of the working electrode There are the following two methods for adsorbing molecules contained in the gas to be measured to the working electrode.

  The first method is a method in which a working electrode is directly brought into contact with a gas to act. In this method, the working electrode is exposed to a gas to be measured, and molecules in the gas are adsorbed on the electrode surface. The exposure time is usually from several seconds to 10 minutes. Thereafter, the working electrode is immersed in a reference solution, and the electrochemical impedance at the working electrode is measured. This method is based on the fact that the adsorption can be maintained even when the sulfide adsorbed on the surface of the metal body in the gas phase is transferred into the liquid phase. Note that the reference electrode and the counter electrode may be immersed in a standard solution in advance.

  The second method is a method in which molecules contained in a gas act on a working electrode in a reference solution. In this method, a gas is once passed through a reference solution, and molecules contained in the gas are dissolved or taken into the reference solution. Subsequently, the three electrodes are immersed in the reference solution to adsorb the molecules taken in the reference solution onto the surface of the working electrode. Thereafter, the electrochemical impedance at the working electrode is measured. In addition, the method of melt | dissolving or taking in the molecule | numerator contained in gas in a reference | standard solution is not specifically limited. For example, a method of passively taking in the reference solution from the liquid surface by simply contacting the gas, a method of inserting a tube into the reference solution and discharging the gas in a bubble form from the tube, and taking in the reference solution and the gas. The method of taking in by stirring is mentioned.

(5) Pre-measurement Before starting the measurement, pre-measurement may be performed using a gas that does not contain a metal-adsorbing molecule. This is for stabilizing the impedance of the electrode with respect to the gas not containing the metal-adsorbing molecule. The “gas not containing metal-adsorbing molecules” corresponds to, for example, an inert gas. It is preferable to repeat the polishing of the electrode of (2) and the pre-measurement until the electrochemical impedance obtained by the pre-measurement is stabilized at about ± 20Ω.

(6) Sample measurement After performing the procedures (1) to (5) as necessary, the measurement target gas is allowed to act on the working electrode to measure electrochemical impedance. The measurement may be carried out according to the measurement conditions of (1) above, and the method for adsorbing molecules onto the surface of the working electrode may be performed using any of the methods of (4) above.

  The electrochemical impedance method is a known technique, and the surface polarization control method is also a known method disclosed in Patent Document 4. Therefore, the surface polarization control method used in the present embodiment may basically be performed according to the method described in Patent Document 4.

  B. Method for measuring molecules adsorbed on metal surfaces using surface plasmon resonance measurement

  “Surface plasmon resonance measurement method” is also called SPR method (surface plasmon resonance method), which utilizes the fact that the resonance angle of the surface plasmon resonance phenomenon varies depending on the refractive index of the adsorbate on the metal thin film surface. This is a method for measuring the adsorbate with high sensitivity. The surface plasmon resonance phenomenon is a phenomenon in which the intensity of reflected light is attenuated with a change in the incident angle of laser light on a metal thin film. The angle at which the reflected light intensity is attenuated most is called the resonance angle.

The principle of the surface plasmon resonance measurement method will be described with reference to FIG. (A) of this figure is an example of a structure of the surface plasmon resonance means explained in full detail in Embodiment 2. FIG. When the light source (0903) is irradiated with light (0908) from the light source (0903) onto the back surface of the metal thin film (0902) deposited on the prism (0905) or on a glass plate (not shown), the light is totally reflected and simultaneously reflected on the metal thin film. An evanescent wave (not shown) is generated. At this time, surface plasmons (not shown) are generated on the metal thin film surface side. When the wave number and frequency of the evanescent wave and the surface plasmon coincide with each other, photon energy is consumed to excite the electrons of the surface plasmon by resonance. Therefore, when the incident angle of light is changed, a phenomenon occurs in which reflected light attenuates at a certain incident angle. As described above, the incident angle when the reflectance, which is the ratio of the reflected light intensity to the incident light intensity, is minimum is called the resonance angle, and this angle is influenced by the interaction between the substances generated on the surface of the metal thin film. An example of the change in the resonance angle will be described with reference to FIG. The presence or absence of adsorption of a substance on the surface of the metal thin film can be grasped as a change in the resonance angle θ before and after that. For example, when the resonant angle of the state not adsorbed anything gold thin film surface and theta _0, resonant angle in the state adsorbed molecules of the metal adsorbing the metal thin film including a sulfide on the surface theta ₁ To change. In this case, it is possible to measure how many molecules the metal thin film has adsorbed on the surface by observing the change in the value of Δθ which is the difference between θ ₁ and θ ₀ .

    (1) Pretreatment

  A normal SPR measurement method is performed on molecules adsorbed on a metal thin film in a liquid phase. Therefore, a treatment for mixing the sulfide-removed gas or the sulfide-removed gas and the carrier solution is performed before the measurement. This is because the metal-adsorbing molecules contained in the gas are dissolved or taken into the carrier solution. The carrier solution may be water or the like.

  The mixing method is not particularly limited as long as the metal-adsorbing molecules contained in the gas can be sufficiently dissolved or taken into the carrier solution. For example, as shown in FIG. 9 (a), one end of the introduction tube is immersed in the carrier solution, and the gas introduced into the measurement unit is passed through the carrier solution as bubbles from the introduction tube end. Examples thereof include a method, a method of stirring the gas and the carrier solution, and a method of passively taking in the gas from the liquid surface by bringing the carrier solution into contact with the gas.

(2) Measurement conditions, etc. (when using an SPR measurement device that assumes measurement in the liquid phase)
-SPR measuring device: A commercially available device can be used. An SPR measuring device employing a flow system is convenient.
-The measurement temperature is 25 ° C. ± 1 ° C., and the amount of carrier solution introduced is in the range of 50 μl to 400 μl. When using a model employing a flow system, the flow rate and the distribution time may be appropriately determined according to the amount of introduction. For example, if 200 μl is to be introduced, it may flow for about 14 minutes at a flow rate of 15 μl / min. However, the above is an example, and the numerical value is not limited thereto.
Note that SPR measurement may be performed according to a manual attached to the SPR measurement device.

  The surface plasmon resonance measurement method is a known method, and the surface plasmon resonance measurement method used in the present embodiment may be performed according to the method described in Non-Patent Document 3.

  C. Measurement method of molecules adsorbed on metal surface using quartz crystal microbalance

  The “quartz crystal microbalance method” is also called QCM method (quartz crystal microbalance method). When a substance adsorbed on the surface of an electrode attached to the crystal resonator is adsorbed, the resonance frequency of the crystal resonator decreases according to its mass. This is a mass measurement method that makes use of the phenomenon that causes a very small amount of adsorbate to be captured quantitatively based on the amount of change in resonance frequency.

  The mass measurement of the adsorbate in the QCM method is performed based on the Sauerbrey equation. According to this method, the mass of the substance adsorbed on the electrode at the monoatomic layer level can be measured at the nanogram level.

  The crystal resonator microbalance method is a known method, and the crystal resonator microbalance method used in the present embodiment may be performed in accordance with the method described in Non-Patent Document 4.

  ((Total gas measurement process))

      I. Definition

  The “total gas measurement process” (S0102) is a method in which a sulfide removal incomplete gas is brought into contact with the surface of a metal body, and sulfide removal is not performed by a surface polarization control method, a surface plasmon resonance measurement method, or a quartz crystal microbalance method. This is a step of measuring the degree of adsorption of molecules in the finished gas to the surface of the metal body.

  The “sulfide removal incomplete gas” is a measurement gas that has not undergone the sulfide removal step. That is, this means the measurement gas itself. However, this is not the case when a pre-measurement process other than the sulfide removal process using the metal filter of the present embodiment is performed separately.

  “To make the sulfide removal incomplete gas contact the metal body surface” means that the gas (in this case, the sulfide removal incomplete gas) is directly touched to the metal body surface as in the case of the background measurement step. Instead, it means that molecules contained in a gas are reacted on the surface of the metal body.

  The “degree of adsorption of molecules in the sulfide-removed gas on the metal body surface” refers to the degree of binding of molecules contained in the sulfide-removed gas to the metal body surface. The degree of coupling is expressed as a measurement value obtained by a surface polarization control method, a surface plasmon resonance measurement method, or a quartz crystal microbalance method.

      II. Purpose and configuration

  The purpose of the total gas measurement step is to measure the degree of adsorption of the molecules contained in the sulfide removal-incomplete gas on the surface of the metal body as a measured value. In the total gas measurement step, a sulfide removal-incomplete gas is brought into contact with the metal body surface, and the degree of adsorption of molecules that can be adsorbed on the metal body surface contained in the gas is measured.

  Unlike the sulfide-removed gas, the sulfide-removed incomplete gas is not subjected to the removal treatment for sulfide. That is, in the gas, there can be sulfides and substances having metal adsorptivity other than sulfides. As described in the sulfide removal process, in a gas in a general living environment, a substance comparable to the metal adsorption energy of sulfide is rare. Accordingly, even if a large amount of a substance having metal adsorptivity other than sulfide exists in the incomplete sulfide removal gas, only a small amount is adsorbed on the metal body. On the other hand, most of the sulfide is adsorbed to the metal body even if only a very small amount is present in the measurement gas. Therefore, in the total gas measurement process, measurement is performed on substances adsorbed on metal bodies, that is, most sulfides contained in unsulphided gas and substances having metal adsorptivity other than a small part of sulfides. A value can be obtained.

  The process contents of the total gas measurement process and the background measurement process are basically the same except for one difference. The said difference is the gas made to contact the metal body surface used as the object of a measurement. That is, both steps are processed under the same conditions except that the gas brought into contact with the metal body surface in the total gas measurement step is not sulfide-removed gas but sulfide-removed gas. For example, the same measurement method and the same measurement conditions are used except for the gas to be measured for the method for measuring the degree of adsorption of molecules on the surface of the metal body.

  ((Sulphide determination process))

      I. Definition

  “Sulphide determination step” (S0103) means the degree of adsorption of molecules in the sulfide removal-incomplete gas measured by the total gas measurement step, and the molecule in the sulfide-removed gas measured by the background measurement step. This is a step of quantifying the sulfide contained in the measurement gas from the difference from the degree of adsorption.

      II. Purpose and configuration

  The purpose of the sulfide determination step is to determine the amount of sulfide contained in the measurement gas. The quantification may be either a relative amount or an absolute amount of sulfide.

  A method for quantifying sulfide in the measurement gas in the sulfide quantification step will be described below. First, the measured value representing the degree of adsorption of molecules in the sulfide-removed gas obtained in the background measurement step is “V0”, and represents the degree of adsorption of molecules in the sulfide-unfinished gas obtained in the total gas measurement. The measured value is represented by “V1”. Here, “V0” can be understood as a response value to a metal adsorbing substance other than sulfide contained in the sulfide-removed gas, that is, a metal adsorbing substance other than sulfide not adsorbed on the metal filter. it can. Further, “V1” can be understood as a response value to sulfides contained in the sulfide incomplete gas and metal adsorbing substances other than sulfides. By the way, metal adsorbing substances other than sulfides present in gases in a general living environment have a very weak adsorptivity to metals, so that even if they are present in large quantities, they are only slightly adsorbed to metals. Just as you did. Therefore, the response value due to the metal adsorbent other than sulfide in the sulfide-removed gas and the response value due to metal adsorbent other than sulfide in the sulfide-removed gas are both very small. It can be understood that there is almost no difference. Therefore, the sulfide contained in the measurement gas can be quantified by obtaining the difference value between V0 and V1 (hereinafter referred to as “Vx”).

Vx may be obtained by either of the following formulas 1 or 2, but when using a calibration curve described later or when obtaining the relative amounts of sulfides contained in a plurality of measurement gases, the same formula is used. Use the value found below.
Vx = V1-V0 (Equation 1)
Vx = V0-V1 (Equation 2)
Vx corresponds to the index of sulfide in the measurement gas. Furthermore, when the concentration of sulfide in the measurement gas is quantified, a sulfide concentration corresponding to Vx may be obtained from a predetermined calibration curve. It should be noted that the calibration curve is obtained by measuring the standard difference value measured for a measurement gas containing a plurality of known concentrations of sulfides and the concentration of sulfides at that time by the same method as that used for obtaining the Vx. Made from relationships.

  The sulfide determination step can also be executed as a program (sulfide determination program) for causing a computer such as a computer to execute the series of determination methods. In this case, the sulfide determination step is executed by the program on the computer. The program can be recorded on a recording medium readable by a computer.

<Embodiment 1: Processing flow>
The processing flow of this embodiment has three patterns shown in FIGS. In any case, it is composed of three steps of a sulfide-removed gas measurement step (S0101 / S0202 / S0301), a total gas measurement step (S0102 / S0201 / S0302), and a sulfide determination step (S0103 / S0203 / S0303). Yes. Further, the sulfide-removed gas measurement step further includes a sulfide removal step (S0104 / S0204 / S0304) and a subsequent background measurement step (S0105 / S0205 / S0305). Hereinafter, each pattern will be described.

  The first pattern is a process flow pattern shown in FIG. In this pattern, first, the sulfide-removed gas measurement step (S0101) is performed, then the total gas measurement step (S0102) is performed, and finally the sulfide determination step (S0103) is performed.

  The second pattern is a process flow pattern shown in FIG. In this pattern, first, the total gas measurement step (S0201) is performed. Next, a sulfide removed gas measurement step (S0202) is performed, and finally a sulfide determination step (S0203) is performed.

  The third pattern is a process flow pattern shown in FIG. In this pattern, the sulfide-removed gas measurement step (S0301) and the total gas measurement step (S0302) are independent of each other. Either of these steps may be performed first or at the same time. Finally, a sulfide determination step (S0303) is performed.

  Measurement of sulfide in the air by the sulfide measurement method of the present embodiment can be achieved by any of the above processing flows.

  By the way, the sulfide-removed gas measurement step (S0101 / S0202 / S0301) is intended to obtain a measurement reference value in order to quantify the sulfide in the measurement gas with high sensitivity. However, depending on the measurement gas, it may not be necessary to obtain the measurement reference value. For example, it is apparent that there is no metal-adsorbing substance other than sulfide in the measurement gas, and there is a case where only the concentration of sulfide in the gas is measured. Therefore, only when there is no need to obtain the measurement reference value of the measurement gas, the sulfide-removed gas measurement step can be omitted in any of the above patterns.

<Embodiment 1: Effect>
According to the sulfide measuring method of the present embodiment, it is possible to detect even if the concentration of sulfide in the air is several ppt to several tens of ppt as in the examples described later. This is a value comparable to or exceeding the limit of detection of sulfide by human olfaction.

<< Embodiment 2 >>

<Embodiment 2: Overview>
The present embodiment relates to a sulfide measuring apparatus using the sulfide measuring method of the first embodiment. According to the sulfide measuring apparatus of the present embodiment, a sulfide measuring apparatus having a detection sensitivity comparable to or exceeding the sulfide detection sensitivity by human olfaction can be provided.

<Embodiment 2: Configuration>
FIG. 4 is an example of a configuration diagram of the sulfide measuring apparatus in the present embodiment. As shown in this figure, the sulfide measuring apparatus of this embodiment is an apparatus for measuring sulfide contained in the air, and includes an introduction pipe (0401), a metal filter part (0402), a measuring part (0403), And a calculation unit (0404). Hereinafter, each component requirement will be described in detail.

    (Introduction pipe)

  The “introducing tube” (0401) is configured to introduce a measurement gas into a measurement unit described later.

  As for the material of the introduction pipe, at least when the sulfide removal-incomplete gas is introduced into the measurement unit, the portion in direct contact with the gas needs to be made of a material other than metal. This is because, when a metal is used, sulfide contained in the measurement gas is adsorbed in the process of passing through the introduction pipe. Examples of the material of the introduction pipe include fluororesin, metal having at least the inner wall surface covered with a synthetic resin such as fluororesin, and glass (preferably tempered glass or an outer wall surface covered with a synthetic resin). .

  The length of the introduction pipe and the inner diameter of the pipe are appropriately determined according to the size of the sulfide measuring device (particularly the measuring section) in which it is placed, the place where the sulfide measuring device is used, and the like. For example, in the case of an installation-type sulfide measuring device intended to measure indoor air sulfide, the length is such that a metal filter section described later can be arranged, and the inner diameter is several cm. The introduction pipe may be used. In addition, if it is a portable sulfide measuring device intended to measure sulfide in the local air, such as when measuring the inside of a drain pipe, it is long enough to reach the location to be measured In addition, a small diameter introduction pipe having an inner diameter of 1 cm or less may be used. Furthermore, the inner diameter of the inlet tube need not be constant. For example, a part of the introduction pipe may be enlarged to form an air chamber. Such a structure is convenient when the inside of the air chamber is filled with a metal filter to form a metal filter portion.

  The function of the introduction pipe is to isolate the measurement gas from other gases and guide it to the measurement unit. Moreover, it is providing the place which processes with respect to measurement gas in the meantime. The introduction pipe of this embodiment can provide a field for obtaining a sulfide-removed gas by arranging a metal filter portion.

  One or two introduction pipes for introducing the measurement gas into one measurement unit are sufficient, but there is no particular limitation. For example, there may be three or more in order to introduce a necessary amount of measurement gas into the measurement unit in a short time.

  The introduction tube may be detachable. As an example of the detachable introduction pipe, there is a screw-screw type introduction pipe as shown in FIG. (A) shows a state in which the introduction pipe on which the metal filter part is arranged is screwed into the measurement part, and (b) shows a state in which the introduction pipe is removed. According to such a configuration, the metal filter portion can be inserted and removed together with the introduction tube, which is convenient.

  The introduction pipe may have a valve disposed therein, a valve control means for controlling opening and closing of the valve, and the like. The valve maintains the airtightness of the air chamber in the measurement unit described later, or permits introduction of gas only from a predetermined introduction pipe when it has a plurality of introduction pipes, and inflow of gas from other introduction pipes It has a function of shielding. The opening and closing of the valve by the valve control means can be executed by a computer such as a computer. Such control can be realized by executing a valve opening / closing program recorded in advance in the computer.

    (Metal filter part)

  The “metal filter unit” (0402) is configured to have the metal filter of the first embodiment for removing sulfides in the measurement gas. A metal filter part is a part which performs the sulfide removal process of Embodiment 1.

  The metal filter portion is disposed so as to be insertable / removable into / from the introduction tube. As used herein, “insertable / removable” means not only that the metal filter portion (0501) is mounted in one introduction pipe (a) or removed from the introduction pipe (b) as shown in FIG. It means that a gas passing through the metal filter part (sulfide-removed gas) and a gas not passing through (sulfide-removed gas) can be obtained separately. For example, as shown in FIG. 6, when the introduction pipe in which the metal filter part (0601) is arranged is detachable from the measurement part, or as shown in FIG. 7, the introduction pipe (0701) having the metal filter part This includes a case where a plurality of introduction pipes (0705) which are not provided are arranged in the measurement unit.

  A plurality of metal filter portions may be arranged in one introduction pipe as long as they are arranged so that they can be inserted into and removed from the introduction pipe. It is because the sulfide in the measurement gas can be more reliably removed by arranging a plurality of them. In this case, each metal filter part arrange | positioned at one introduction pipe does not necessarily need to be the same. This is because the removal rate of sulfide in the measurement gas can be increased by combining the introduction pipes with different types of metal filters.

  As shown in FIG. 5, it is convenient to automatically switch the mounting of the metal filter portion to the introduction pipe or the mounting of the connecting introduction pipe instead of removing the metal filter portion. The metal filter part may further have a metal filter attachment / detachment control means for controlling such switching. The attachment / detachment of the metal filter by the metal filter attachment / detachment control means can also be executed by a computer such as a computer. For example, this can be realized by the CPU of the computer sequentially executing a sulfide measurement program recorded in advance in a nonvolatile memory.

  (Measurement part)

  The “measuring unit” (0403) includes a measurement cell (0406) in which a metal body (0405) serving as a means for detecting molecules in a gas is disposed, and an adsorbed molecule measuring means (0407) for measuring molecules adsorbed on the surface of the metal body. ). The measurement unit is a unit that performs the background measurement process and the total gas measurement process of the first embodiment.

  The “measurement cell” (0406) is a field for bringing a gas into contact with the surface of the metal body and simultaneously detecting a molecule adsorbed on the surface of the metal body. In addition to the gas chamber holding the gas and the metal body, it is composed of liquids such as various necessary detectors and necessary reference solutions according to the adsorbed molecule measuring means.

  “Adsorbed molecule measuring means” (0407) is a means for measuring the degree of adsorption of molecules adsorbed on the surface of a metal body. Specific examples include surface polarization control means, SPR measurement means, QCM measurement means, or a combination thereof, which will be described later. However, any means capable of measuring the degree of adsorption may be used, and the means is not limited to these means.

  The function of the measurement unit is to measure the degree of adsorption of molecules on the surface of the metal body after the gas introduced from the introduction tube is brought into direct or indirect contact with the surface of the metal body.

  The introduction of the gas into the air chamber is preferably performed by an active method in order to introduce it quickly and reliably. In addition, the metal filter part can be an obstacle to gas introduction into the measurement part, but this problem can be solved if gas is actively introduced. As a method for actively introducing gas, for example, a method of blowing gas into the air chamber using a blower arranged in an introduction pipe, a vacuum means or a pump means (hereinafter referred to as “vacuum means” or the like). A method of using the negative pressure inside the air chamber by using it is mentioned. In the latter case, the air pressure in the air chamber may be adjusted using a pressure adjusting device such as a regulator. For example, by causing a computer to execute a program for introducing and evacuating gas in the air chamber, and controlling the operation of the vacuum means and regulator by the computer, the air pressure in the air chamber is adjusted and the measurement process is performed. Intake and deaeration into the air chamber can be executed.

  Hereinafter, surface polarization control means, SPR measurement means, and QCM measurement means, which are examples of adsorbed molecule measurement means in the measurement unit, will be described.

      A. Surface polarization control means

  The “surface polarization control means” is configured to detect the degree of adsorption of molecules in the gas on the metal body surface by a surface polarization control method.

  The configuration of the surface polarization control means is the same as that of the apparatus disclosed in Patent Document 4. That is, it has a configuration in which a known electrochemical impedance measuring device and an oscillator are combined to sequentially shift the potential value of the working electrode to a plurality of values. More specifically, as shown in FIG. 8, the surface polarization control means includes an electrode device (0801), a current controller (0802), a transition controller (0803), and an electrochemical impedance analyzer (0804). It consists of and.

    The electrode device (0801) includes a working electrode (0805), a reference electrode (0806), and a counter electrode (0807), which are three electrodes used for so-called electrochemical measurement. Of these, the working electrode (0805) corresponds to the substantial metal body of the present embodiment, but the reference electrode and the counter electrode are also necessary for obtaining chemical impedance, and can be understood as an auxiliary metal body. The metal species of each electrode need not be the same. For example, in one electrode device, the working electrode may be gold (Au), the reference electrode may be a silver-silver chloride electrode (Ag / AgCl) immersed in a saturated KCl solution, and the counter electrode may be platinum black (Pt-Pt). Absent. Further, the potential measurement of this measuring means is performed in the liquid phase. Therefore, the electrode device requires a reference solution (0808) in which at least three electrodes can be immersed during potential measurement. The reference solution may be an electrolytic solution, and for example, a 100 mM KCl solution can be used. FIG. 8 shows a method in which the working electrode is exposed to the gas phase and then immersed in a reference solution indicated by an arrow. However, as described in the first embodiment, the working electrode is used before the measurement. You may be in the state immersed in.

    The current controller (0802) has a function of flowing a current necessary for setting the electrode potential of the working electrode with respect to the reference electrode of the electrode device to a predetermined potential value. A specific example is a potentiostat. The current controller has its current output controlled by the next transition controller (0803).

    The transition controller (0803) has a function of controlling the current controller in order to sequentially shift the potential value to a plurality of values. A specific example is an oscillator. The sequential transition of the potential value to a desired value can be realized by executing a potential value transition program installed in the transition controller. If a desired potential value is input in advance, the program can be executed so as to control the current controller according to the plurality of input potential values.

    The electrochemical impedance analyzer (0804) has a function of calculating an electrochemical impedance from a current value that flows for each of the plurality of potential values. A specific example is a computer such as a computer. The electrochemical impedance analyzer is preinstalled with an electrochemical impedance calculation program for calculating electrochemical impedance from the acquired current value. The measured value of the electrochemical impedance calculated for each potential value is sent to a calculation unit described later. The electrochemical impedance analyzer and the measurement unit may be the same computer.

      B. SPR measurement means

  The “SPR measurement means” is configured to detect the degree of adsorption of molecules in a gas on the surface of a metal body by a surface plasmon resonance measurement method.

  The basic configuration of the SPR measurement means is the same as that of a known SPR measurement device. Specifically, as shown in FIG. 9A described in the first embodiment, a mixing chamber (0901), a metal thin film (0902), a light source (0903) such as a laser, a photodetector (0904), and the necessary A prism (0905), an SPR analyzer (0906), and the like are included.

    The mixing chamber (0901) is configured to mix the gas introduced into the measurement unit with the SPR measurement liquid and dissolve or take in molecules such as sulfides contained in the gas in the carrier solution (0907). .

    The metal thin film (0902) corresponds to the metal body of this embodiment. As described above, when the SPR measurement method is used, it is desirable that the metal body is a thin film. The metal thin film only needs to have a thickness of several nm to several tens of nm. Note that one of the metal thin film surfaces is configured so that the carrier solution treated in the mixing chamber (0901) can come into contact therewith.

    The light source (0903) has a function for emitting light to the surface opposite to the surface where the metal thin film is in contact with the carrier solution. Usually, a laser or LED is used. At this time, in order to control the incident angle of the light from the light source to the surface of the metal thin film, a reflection plate or the like may be provided.

    The photodetector (0904) is a device that detects reflected light that is incident from the light source and reflected by the surface of the metal thin film. Usually, a (photo) diode array detector or the like is used.

    The prism (0905) may be used as necessary for the SPR measurement means to be used.

    The SPR analyzer (0906) has a function of calculating the reflectance based on the incident light intensity of the light source and the reflected light intensity detected by the photodetector, and the incident angle (resonance angle) of light that causes SPR. . A specific example is a computer such as a computer. The SPR analyzer is preinstalled with an SPR calculation program for calculating reflectivity and resonance angle. The calculated measurement value is sent to a calculation unit described later. As in the case of the electrochemical impedance analyzer, the SPR analyzer and the calculation unit may be the same computer.

      C. QCM measurement means

  The “QCM measuring means” is configured to detect the degree of adsorption of molecules in the gas on the surface of the metal body by a quartz crystal microbalance measuring method.

  The basic configuration of the QCM measuring unit is the same as that of a known QCM measuring device. Specifically, as shown in FIG. 10, a crystal resonator (1001), a current controller (1002), a transition controller (1003), a frequency measuring device (1004), a QCM analyzer (1005), an auxiliary electrode ( 1006).

    The crystal unit (1001) is composed of a crystal body and a metal electrode deposited on the surface thereof. The crystal unit corresponds to the metal body of the QCM measuring unit. Molecules in the gas are adsorbed on the metal electrode.

    The current controller (1002) has a function of flowing a necessary current to the crystal resonator. A specific example is a potentiostat. The current controller has its current output controlled by the next transition controller (1003).

    The transition controller (1003) has a function of controlling the current value applied to the metal electrode of the crystal resonator in order to shift the frequency of the crystal resonator to a plurality of values. A specific example is an oscillator. The transition of the applied current value to a desired value can be realized by executing a current value transition program installed in the transition controller. If a desired current value is input in advance, the program can be executed to control the current controller in accordance with the plurality of input potential values.

    The frequency measuring device (1004) has a function of measuring a frequency obtained from a crystal resonator.

    The QCM analyzer (1005) has a function of calculating a change in oscillation frequency obtained from the crystal resonator. A specific example is a computer such as a computer. The QCM analyzer is preinstalled with a calculation program such as mass for calculating a frequency change amount, a mass change amount, and the like. The calculated measurement value is sent to a calculation unit described later. As in the case of the electrochemical impedance analyzer and the SPR analyzer, the QCM analyzer and the calculation unit may be the same computer.

    The auxiliary electrode (1006) is an electrode for flowing current between the metal electrode of the crystal resonator. Energization is performed in a solution (1007) such as an electrolytic solution.

  (Calculation section)

  “Calculation unit” (0404) is included in the measurement gas from the difference between the measurement result of the gas introduced through the metal filter unit and the measurement result of the gas introduced without going through the metal filter unit. It is configured to quantify sulfides. The calculation unit corresponds to a computer such as a computer. The process of quantifying sulfide in the calculation unit can be realized by the following. First, the sulfide determination program described in the sulfide determination step of the first embodiment is installed in a nonvolatile memory or the like. Next, it can be realized by the CPU calling the program onto the main memory and sequentially executing instructions according to the program.

  As described above, the calculation unit may be the same computer as the electrochemical impedance analyzer, the SPR analyzer, or the QCM analyzer. In other words, the calculation unit and any one of the analyzers may be processed by one computer.

  The quantitative value of the sulfide in the measurement gas calculated by the calculation unit is output to a display device for display with images, prints, sounds, and the like. For example, the display device corresponds to a display device for images, a printer for printing, and a speaker for audio.

<Embodiment 2: Effect>
According to this embodiment, a sulfide measuring device having a detection sensitivity of the order of several ppt to several tens of ppt can be provided. This detection sensitivity is comparable to or exceeding the detection sensitivity of human olfactory sulfide. Therefore, by using the sulfide measuring apparatus of the present embodiment, it becomes possible to find at least the cause of bad odor due to sulfide.

<< Embodiment 3 >>

<Embodiment 3: Overview>
The present embodiment relates to a sulfide measuring apparatus using the sulfide measuring method of the first embodiment. The measurement principle of the measurement apparatus of the present embodiment and the basic configuration of the apparatus are the same as in the second embodiment. The most characteristic feature of this embodiment and the difference from the second embodiment is that it has two measuring units. Each measuring unit measures a sulfide-removed gas and a sulfide-removed incomplete gas separately. As a result, it is possible to simultaneously measure a sulfide-removed gas and a sulfide-removed incomplete gas with respect to one measurement gas. Therefore, the sulfidation in the measurement gas can be performed in a shorter time than the measurement apparatus of the second embodiment. You can measure things.

<Embodiment 3: Configuration>
FIG. 11 shows an example of the configuration of the sulfide measuring apparatus in the present embodiment. As shown in this figure, the sulfide measuring apparatus of the present embodiment is an apparatus for measuring sulfide contained in the air, and includes a first introduction pipe (1101), a metal filter part (1102), and a first measuring part. (1103), a second introduction pipe (1104), a second measurement unit (1105), and a common calculation unit (1106). Each component will be specifically described below.

  The “first introduction pipe” (1101) is configured to introduce a measurement gas into a first measurement unit described later. The basic configuration and function of the first introduction pipe are the same as those of the introduction pipe (0401) of the second embodiment. The difference from the introduction pipe (0401) of the second embodiment is that the first introduction pipe always has the metal filter portion. That is, the first introduction pipe can be said to be a pipe for introducing a gas from which sulfide has been removed.

  The “metal filter part” (1102) of the present embodiment is arranged in the first introduction pipe and is configured to remove sulfides in the measurement gas. The basic configuration and function of the metal filter unit are the same as those of the metal filter (0402) of the second embodiment. However, the metal filter part of this embodiment is arrange | positioned only at a 1st inlet tube as mentioned above, and is not arrange | positioned at the 2nd inlet tube mentioned later. Further, as described above, it is always arranged in the first introduction pipe, and is different from the configuration of the metal filter portion of the second embodiment in that it cannot be inserted or removed.

  The “first measurement unit” (1103) is configured to measure the degree of adsorption of gas molecules on the metal body surface by bringing the gas introduced from the first introduction pipe into contact with the metal body surface. The basic configuration and function of the first measurement unit are the same as those of the measurement unit (0403) of the second embodiment. The difference from the measurement unit of the second embodiment is that the gas introduced into the first measurement unit is only the gas introduced from the first introduction pipe, that is, the sulfide-removed gas, and the metal adsorption contained in the gas. It is to measure the degree of adsorption of sex molecules. The metal body of the first measurement unit is disposed in an air chamber isolated from other gases at least during gas measurement. This is to prevent other gases from being mixed into the sulfide-removed gas.

  The “second introduction pipe” (1104) is configured to introduce the measurement gas into the second measurement section described later. The basic configuration and function of the second introduction pipe are the same as those of the introduction pipe (0401) and the first introduction pipe of the second embodiment. The difference from them is that the second introduction pipe does not have a metal filter part. That is, it can be said that the second introduction pipe is an introduction pipe for introducing a gas whose sulfide has not been removed. The second introduction tube may be detachable.

The “second measuring unit” (1105) is configured to measure the degree of adsorption of molecules in the gas to the metal body surface by bringing the gas introduced from the second introduction pipe into contact with the metal body surface as it is. Yes. “As is” means that no treatment for removing the sulfide is performed.
The basic configuration and functions of the second measurement unit are the same as those of the measurement unit (0403) and the first measurement unit (1103) of the second embodiment. The difference between the measurement unit of Embodiment 2 and the first measurement unit is that the gas introduced into the second measurement unit is only the gas introduced from the second introduction pipe, that is, the sulfide removal-incomplete gas, It is to measure the degree of adsorption of metal adsorbing molecules contained in the gas. In addition, when the analyzer (for example, SPR analyzer) which comprises a 1st measurement part and a 2nd measurement part can process two or more measurement data simultaneously and independently, said 1st measurement part and 1st The analyzers of the two measuring units may be integrated.

  The “common calculation unit” (1106) is configured to quantify the sulfide contained in the measurement gas from the difference between the measurement result of the first measurement unit and the measurement result of the second measurement unit. . The basic configuration and functions of the common calculation unit are the same as those of the calculation unit (0404) of the second embodiment. The common calculation unit is a measurement obtained from the first measurement unit and the second measurement unit, whereas the calculation unit of the second embodiment quantifies sulfide based on the measurement value obtained from one measurement unit. The difference is that the sulfide is quantified based on the value. That is, in this embodiment, even if it has several measurement parts, it is comprised so that the measured value obtained from them may be processed by one calculation part (common calculation part).

  As described above, in the present embodiment, the sulfide-removed gas and the sulfide-removed incomplete gas are carried out in independent parts from taking in the measurement gas and measuring the degree of molecular adsorption on the metal surface. This is different from the second embodiment. In the present embodiment, the degree of adsorption of the molecules contained in the two gases to the surface of the metal body can be measured simultaneously in parallel. Further, unlike Embodiment 2, it is not necessary to clean or replace the surface of the metal body of the measurement unit after measuring one gas. Therefore, the time required to measure two gases is shorter than that in the second embodiment. Therefore, when it is necessary to measure the sulfide concentration in a short time, the sulfide measuring apparatus of this embodiment is convenient.

<Embodiment 3: Effect>
According to the sulfide measuring apparatus of the present embodiment, sulfide in the measurement gas can be measured in a shorter measurement time than the sulfide measuring apparatus of the second embodiment.

<< Measurement of sulfides in the air >>
The present invention will be specifically described with reference to the following examples. This example shows that a known concentration of sulfide is measured using the sulfide measurement method of Embodiment 1, and that response is possible even when the sulfide concentration is at the ppt level. In addition, a present Example is only illustrated and Embodiment 1 is not limited at all by this Example.

<Method>
In this example, a case where a surface polarization control method is used as an example of a method for measuring the degree of adsorption of molecules in a gas to the surface of a metal body will be described.

  A. Equipment and equipment used for measurement

(A) Electrode
-Working electrode: 3 mm diameter gold (Au) electrode rod
Reference electrode: Silver / silver chloride electrode immersed in a saturated KCl solution (Ag / AgCl)
・ Counter electrode: 0.5mm diameter platinum wire
Reference solution: 100 mM KCl solution

      A solution obtained by immersing the three electrodes in a container containing a reference solution is used. Each electrode is connected to a potentiostat during measurement by wiring.

(B) Measuring instruments and equipment
· Potentiostat + oscillator (AutoLab PGSTAT12: ECHO CHEMIE)
・ About 1g of steel wool in a 200ml container that can be sealed (A air chamber)
-Containers of the same type as above, without steel wool (B air chamber)

B. Electrochemical impedance measurement conditions
・ Measurement range of electrode potential: 0.2V to 0.8V (for measurement)
: 0.22V to 0.88V (for pre-scan)
-Potential step width: 0.1 V (for measurement)
0.02V (for pre-scan)
・ Measurement time for each step: 0.05 seconds
・ Applied voltage: AC frequency 45 Hz, amplitude 0.01 mV (for total impedance)
AC frequency 1kHz, amplitude 0.01mV (for solution impedance)
The electrode impedance is the total impedance minus the solution impedance

C. Preparation of measurement gas In this example, laboratory air was used as a base. That is, laboratory air was collected and mixed with hydrogen sulfide (H ₂ S) at 1 ppm. Next, the measurement gas of 1 ppm was diluted 10 times with the room air to obtain a measurement gas having a concentration of 100 ppb. Thereafter, the measurement gas having a concentration of 1 ppt was prepared while diluting 10 times with the room air.

  D. Measurement procedure

  1. The electrode was polished and cleaned. As a polishing method, the electrode was polished with an alumina abrasive having a diameter of 0.1 μm for 5 seconds, and then the electrode surface was blown with nitrogen gas and cleaned.

  2. In order to perform the pre-measurement, the working electrode was exposed to a B air chamber filled with laboratory air for 4 minutes, and then transferred to a reference solution to measure the electrode impedance. The measurement conditions for the total impedance and the solution impedance were the same as those described in (2) “Measurement for electrochemical impedance”. Polishing / cleaning and pre-measurement were repeated until the electrode impedance in the pre-measurement was stabilized at about ± 20Ω.

  A measurement gas containing 3.1 ppm of sulfide was filled into the A gas chamber and the B gas chamber through fluororesin tubes. The treatment in the A chamber corresponds to the sulfide removal step of the first embodiment.

  4). The working electrode was exposed to the A chamber for 4 minutes. At this time, the working electrode was not in contact with the steel wool. Subsequently, the electrode impedance was measured by moving into a reference solution. The measurement conditions for the total impedance and the solution impedance were the same as in the above two steps. This step corresponds to the background measurement step of the first embodiment.

  5. The working electrode was polished and washed in the same manner as in the first step, and then pre-measurement was performed again in the same manner as in the second step.

  6). The working electrode was exposed to the B chamber for 4 minutes. Subsequently, the electrode impedance was measured by moving into a reference solution. The measurement conditions for the total impedance and the solution impedance were the same as in the above two steps. This step corresponds to the total gas measurement step of the first embodiment.

  7). The difference of the value of the electrode impedance obtained by the said 4 process and 6 processes was computed. This step corresponds to the sulfide determination step of the first embodiment.

  8. Measurement gases containing 100 ppb, 10 ppb, 1 ppb, 100 ppt, 10 ppt, and 1 ppt of sulfide were similarly performed in the procedure from the above-mentioned 2 steps to 7 steps.

<Result>
12 to 14 show measurement results according to this example. FIG. 12 shows the change in electrochemical impedance for each electrode potential when measuring the sulfide-removed gas at each sulfide concentration, and FIG. 13 shows the sulfide-removed gas by the above method. That is, FIG. 12 corresponds to the measurement result in the sulfide-removed gas measurement process, and FIG. 13 corresponds to the measurement result in the total gas measurement process. The horizontal axis represents the sulfide concentration (ppt) in the measurement gas (known in the present example), and the vertical axis represents the electrochemical impedance (Ω). Incidentally, the electrochemical impedance shown here, the real part of the impedance (ReZ), based on the imaginary part ^(IMZ), shows a value obtained as an absolute value of the square root of ReZ ² + ImZ 2. Therefore, when the amount of sulfide is quantified, it is necessary to obtain the difference between the corresponding measurement values in FIGS. FIG. 14 shows the difference. This figure shows values obtained by subtracting the corresponding values in FIG. 12 from the measured values in FIG. 13. As can be seen from FIG. 14, it is found that the concentration increases in a concentration-dependent manner at about 10 ppt or more.

  As described above, it was proved by the sulfide measurement method of Embodiment 1 that a response can be obtained even when the sulfide concentration is at the ppt level. Therefore, by using the method of Embodiment 1 for the sulfide measuring apparatus described in Embodiments 2 and 3, it is possible to provide an apparatus capable of measuring sulfide contained in an arbitrary measurement gas from 1 ppt to several tens of ppt. .

Flow of processing of sulfide measurement method in embodiment 1 (1) Process flow of sulfide measurement method in embodiment 1 (2) Process flow of sulfide measurement method in embodiment 1 (3) Conceptual diagram of the configuration of the sulfide measuring apparatus in the second embodiment Conceptual diagram of the configuration of the metal filter part that can be inserted and removed (1) (a) A state in which the metal filter part is mounted in one introduction pipe (b) A state in which the metal filter part is removed from the introduction pipe Conceptual diagram of the structure of the metal filter part that can be inserted and removed (2) (a) The state where the introduction pipe on which the metal filter part is arranged is screwed into the measuring part and attached (b) The state where the whole introduction pipe is removed Conceptual diagram of the structure of the metal filter part that can be inserted and removed (3) When multiple introduction pipes are arranged in the measurement part Conceptual diagram of configuration of surface polarization control means Conceptual diagram of configuration of SPR measurement means Conceptual diagram of the configuration of the QCM measurement means The conceptual diagram of the structure of the sulfide measuring apparatus in Embodiment 3. The figure which shows the result of an Example (1) Electrochemical impedance when measuring sulfide-removed gas by the surface polarization control method The figure which shows the result of an Example (2) Electrochemical impedance when measuring the sulfide incomplete gas by the surface polarization control method Diagram showing the quantitative value of sulfide in the measurement gas

Explanation of symbols

0401, 0501, 0601, 0701, 0809, 1009: Introduction pipes 0402, 0502, 0602, 0702: Metal filter part 0503 Part of the introduction pipe not having a metal filter part 0403: Measurement part 0404: Calculation part 0603, 0703: Part of measurement unit 0405, 0604, 0704: Metal bodies 0605, 0707, 0810, 1008: Necessary exhaust pipe 0705: Introduction pipe without metal filter 0706: Valve 0406: Measurement cell 0407: Means for measuring adsorbed molecules

Claims (11)

The sulfide removal step of removing sulfide in the measurement gas with a metal filter to make sulfide-removed gas,
A background measurement step in which the sulfide-removed gas is brought into contact with the surface of the metal body, and the degree of adsorption of the molecules in the sulfide-removed gas on the surface of the metal body is measured by a surface polarization control method;
Total gas for measuring the degree of adsorption of molecules in the sulfide-unfinished gas on the metal body surface by contacting the surface of the metal body with the sulfide-unfinished gas that does not remove the sulfide in the measurement gas by the surface polarization control method Measuring process;
From the difference between the degree of adsorption of molecules in the sulfide-removed gas measured by the total gas measurement process and the degree of adsorption of molecules in the sulfide-removed gas measured by the background measurement process in the measurement gas A sulfide quantification process for quantifying sulfides contained in
A method for measuring sulfide.   The sulfide measuring method according to claim 1, wherein a surface plasmon resonance measuring method is used instead of the surface polarization controlling method.   The sulfide measuring method according to claim 1, wherein a quartz resonator microbalance method is used instead of the surface polarization control method. An apparatus for measuring sulfides contained in the air,
An introduction pipe for introducing the measurement gas into the measurement section described later,
An insertable / removable metal filter part disposed in the introduction pipe for removing sulfides in the measurement gas;
A measurement unit for contacting the gas introduced from the introduction tube with the surface of the metal body, and measuring the degree of adsorption of the molecules in the gas to the surface of the metal body;
A calculation unit for quantifying the sulfide contained in the measurement gas from the difference between the measurement result of the gas introduced through the metal filter unit and the measurement result of the gas introduced without going through the metal filter unit; ,
A sulfide measuring device having The measuring unit is
The sulfide measuring device according to claim 4, further comprising a surface polarization control means for detecting the degree of adsorption of molecules in the gas on the surface of the metal body by a surface polarization control method. The measuring unit is
The sulfide measuring apparatus according to claim 4, further comprising an SPR measuring unit that detects the degree of adsorption of molecules in the gas on the surface of the metal body by a surface plasmon resonance measurement method. The measuring unit is
The sulfide measuring apparatus according to claim 4, further comprising a QCM measuring unit that detects a degree of adsorption of molecules in the gas on the surface of the metal body by a quartz crystal microbalance measuring method. An apparatus for measuring sulfides contained in the air,
A first introduction pipe for introducing a measurement gas into the first measurement section described later;
A metal filter portion disposed in the first introduction pipe for removing sulfides in the measurement gas;
A first measuring unit for contacting the gas introduced from the first introduction pipe with the surface of the metal body, and measuring the degree of adsorption of the gas molecules on the surface of the metal body;
A second introduction pipe for introducing the measurement gas into the second measurement section described later;
A gas that is introduced from the second introduction tube is brought into contact with the surface of the metal body as it is, and a second measurement unit that measures the degree of adsorption of the molecules in the gas onto the surface of the metal body;
A common calculation unit that quantifies the sulfide contained in the measurement gas from the difference between the measurement result of the first measurement unit and the measurement result of the second measurement unit;
A sulfide measuring device having The first measuring unit and the second measuring unit are
9. The sulfide measuring apparatus according to claim 8, further comprising a surface polarization control means for detecting the degree of adsorption of molecules in the gas on the surface of the metal body by a surface polarization control method. The first measuring unit and the second measuring unit are
9. The sulfide measuring device according to claim 8, further comprising an SPR measuring means for detecting the sulfide adsorbed on the surface of the metal body by a surface plasmon resonance measurement method. The first measuring unit and the second measuring unit are
9. The sulfide measuring apparatus according to claim 8, further comprising a QCM measuring means for detecting the sulfide adsorbed on the surface of the metal body by a quartz crystal microbalance measuring method.

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