JP5172442B2 - Ammonia measuring device, ammonia measuring device, chlorine measuring device and chlorine measuring device - Google Patents

Description

  The present invention relates to an ammonia measuring element, an ammonia measuring apparatus, an ammonia measuring method, a chlorine measuring element, a chlorine measuring apparatus, and a chlorine measuring method.

  Ammonia is one of the substances indispensable for producing various materials. This is particularly important in the chemical industry because it is the most basic nitrogen source for compound production. Although it is a substance with a wide range of use in this way, it has chemical properties that are highly toxic and irritating to the mucous membranes of animals such as humans. In addition, it is treated as a malodorous substance in the low concentration range, and is listed as a representative substance of specific malodorous substances by the Malodor Control Law. For example, a trace amount of ammonia in indoor air is known to cause discoloration and deterioration of cultural properties displayed in art museums or museums. Also, in the manufacturing process of products such as semiconductors, it is known that the yield of products is affected due to factors that deteriorate semiconductor elements. In addition, in recent years, in medical institutions, nursing homes, etc., there has been an increasing problem that ammonia generated from patient excrement etc. deteriorates the indoor environment of the living space. Therefore, the request | requirement of exchanging excrement etc. at a suitable timing is increasing.

  In addition, in the air, there is a characteristic of explosion when the ammonia content is 16 to 25% and the temperature becomes high.

  As such, there are dangerous chemical properties such as toxicity and explosiveness, so the handling must be careful. Therefore, a new ammonia measuring method capable of measuring a range from a low concentration to a high concentration is required.

  In general, electrochemical analyzers such as gas chromatographs, semiconducting gas sensors that support catalysts using electrochemical reactions, and neutralization reactions between ammonia and phosphoric acid are used to measure ammonia concentration. There is a detector using a gas detector tube.

  By the way, in recent years, a measuring method using quartz or the like, which is a kind of piezoelectric body, as a sensor has attracted attention. This measurement method utilizes the fact that when a substance adheres to the surface of a crystal or the surface of an electrode formed with the crystal in between, the frequency characteristics of the crystal change due to a change in its mass. By utilizing this property, a sensor that detects and measures the attachment of a very small amount of substance has been realized, which is called a QCM sensor (quartz crystal sensor). In addition, a film having selectivity for the adhesion property of a substance is formed on the surface of the QCM sensor to detect or measure a specific substance (for example, see Patent Documents 1 to 5). .

  As a method for measuring ammonia using a quartz vibrator sensor, a method is known in which a sensing film formed on an electrode surface is used as a sensing element (see Patent Document 6). Patent Document 6 also proposes a method for measuring the ammonia concentration by performing a correction operation for excluding the influence of temperature and humidity by an arithmetic circuit based on the result of measurement with a general temperature and humidity element. Yes.

Similarly, chlorine gas is a gas having a characteristic odor at normal temperature and pressure, and has chemical properties such as toxicity to living organisms and corrosion properties to metal materials. In particular, since it has a strong bleaching action and a bactericidal action, it is generally used as a bleaching agent for pulp and clothing and as a bactericidal agent for tap water and the like. In particular, it is a very dangerous gas for the human body, so when used in general environments such as sterilization and bleaching, it is often used as another chemical substance such as low concentration sodium hypochlorite. . As an apparatus for measuring the chlorine gas concentration, there are generally an electrochemical analyzer represented by a gas chromatograph, a detector using a gas detector tube, and the like.
JP 2001-153777 A (released on June 8, 2001) JP 2005-189076 A (published July 14, 2005) JP 2005-189133 A (published July 14, 2005) JP 2000-275157 A (released on October 6, 2000) JP 2004-226177 A (released on August 12, 2004) Registered Utility Model No. 3094415 (registered on March 19, 2003)

  However, although measurement with an analyzer represented by the gas chromatograph method, etc. can be performed with high sensitivity, the apparatus itself is very expensive, and it is necessary to analyze it by a skilled person who has expertise in analysis when using it. There is. Therefore, it is difficult to handle easily at the measurement site such as the living space described above. In addition, since the apparatus is large, it is not easy to carry, and it is difficult to measure freely anytime and anywhere.

  For semiconductor gas sensors, it is difficult to measure a wide measurement range from a low concentration to a high concentration due to the detection principle. In particular, in the high concentration range, the catalyst on the detection element is poisoned and deteriorates.

  Gas detector tubes have been used at factory sites and the like, but have a problem of low detection sensitivity. In addition, since the measurement range is determined by the length of the reactive agent in the detection tube, there is a limitation on the dynamic range. Furthermore, in the case of measuring ammonia, it is easily affected by gases such as carbon dioxide and amines.

  In the case of ammonia, the apparatus described in Patent Document 6 cannot perform highly sensitive measurement. That is, in this apparatus, measurement is performed by adsorbing ammonia on the sensitive film, but the adsorbed ammonia is easily detached from the sensitive film. That is, since the adsorption / desorption reaction is highly reversible, the ammonia once adsorbed is immediately desorbed. Therefore, it is impossible to measure low concentration of ammonia.

  Of the measurement methods using a quartz resonator, the methods (Patent Documents 1 to 5) that use the organic film or polymer film described above as a detection film are not disclosed for measuring ammonia. . In addition, since adsorption reactions (mainly physical adsorption) occur even in gases and moisture (water molecules) contained in measurement objects other than ammonia, it is easy to be affected by gases other than ammonia, and high-sensitivity measurement can be realized. difficult. Depending on the detection film, the detection characteristics may be deteriorated by poisoning with ammonia.

  Moreover, about the subject of the prior art regarding the ammonia measurement described here, it is the same also about the measurement of chlorine. As described above, devices for measuring the chlorine gas concentration include analyzers such as gas chromatographs, detectors using gas detector tubes, and the like. However, there is no principle or device that can easily measure low-concentration chlorine gas.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a measuring element that measures ammonia with high sensitivity and ease, or an element that measures chlorine, and a measuring apparatus and measuring method using the measuring element. It is to provide.

  As a result of intensive studies to solve the above problems, the present inventor makes the metal and ammonia react by causing a metal that forms a compound with ammonia to exist on the surface of the electrode provided on the piezoelectric body. Focusing on the fact that the mass characteristics change and, as a result, the frequency characteristics change, the present inventors have found a measuring element, a measuring apparatus, and a measuring method using them that can measure the ammonia concentration. In addition, in the measurement based on the presence or absence of the formation of a compound with a metal, the irreversibility is high compared to a mechanism in which ammonia is immediately adsorbed as in Patent Document 6, and high sensitivity is obtained even with a low concentration of ammonia. As a result, the present invention was completed.

  Furthermore, as a result of intensive studies to solve the above-mentioned problems, the present inventor allows the metal and chlorine to react by causing a metal that forms chlorine and a compound to exist on the surface of the electrode provided on the piezoelectric body. Attention has been paid to the fact that a change in mass occurs, resulting in a change in frequency characteristics, and a measuring element capable of measuring the chlorine concentration with high sensitivity has been found and the present invention has been completed.

  That is, the present invention includes the following inventions.

  The ammonia measuring element according to the present invention includes a piezoelectric body and electrodes disposed on both sides of the piezoelectric body, and a metal that forms a compound with ammonia exists on the surface of the electrode.

  Furthermore, in the ammonia measuring element according to the present invention, the electrode is formed by coating the surface of the electrode with a metal that forms a compound with ammonia or a metal that forms a compound with ammonia. It is more preferable.

  Furthermore, in the ammonia measuring element according to the present invention, the surface of the electrode is more preferably mirror-finished.

  Furthermore, in the ammonia measuring element according to the present invention, the metal is more preferably molybdenum.

  An ammonia measuring device according to the present invention includes the above ammonia measuring element, and a frequency measuring device that measures the frequency of the ammonia measuring element generated when the surface of the electrode forms a compound with ammonia. It is characterized by that.

  Furthermore, the ammonia measuring device according to the present invention further includes a humidity measuring element that measures only humidity without being affected by ammonia, and the humidity measuring element is installed on both sides of the piezoelectric body and the piezoelectric body. More preferably, an electrode is provided, and chromium oxide or chromium oxide supporting platinum particles is present on the surface of the electrode.

  Furthermore, in the ammonia measuring apparatus according to the present invention, when two or more kinds of known gases having different concentrations of ammonia come into contact with the ammonia measuring element, the ammonia is measured by the frequency measuring apparatus to form a compound. Calculating means for obtaining the relationship between the ammonia concentration and the oscillation frequency from the frequency of the ammonia measuring element, the storage means for storing the relationship, the relationship referenced from the storage means, and the gas to be measured for the ammonia concentration It is more preferable to comprise ammonia concentration calculating means for calculating the ammonia concentration in the gas to be measured based on the frequency measured by the frequency measuring device when contacting the ammonia measuring element.

  The chlorine measuring element according to the present invention includes a piezoelectric body and electrodes installed on both sides of the piezoelectric body, and a metal that forms chlorine and a compound is present on the surface of the electrode. Yes.

  Furthermore, in the chlorine measuring element according to the present invention, the electrode is formed by coating the surface of the electrode with a metal that forms a compound with chlorine or a metal that forms a compound with chlorine. It is more preferable.

  Furthermore, in the chlorine measuring element according to the present invention, the metal is more preferably molybdenum.

  A chlorine measuring device according to the present invention includes the above chlorine measuring device, and a frequency measuring device that measures the frequency of the chlorine measuring device generated when the surface of the electrode forms a compound with chlorine. It is characterized by that.

  Furthermore, in the chlorine measuring device according to the present invention, when two or more kinds of known gases having different chlorine concentrations are in contact with the chlorine measuring element, the chlorine forms a compound that is measured by the frequency measuring device. Calculating means for obtaining the relationship between the chlorine concentration and the oscillation frequency from the frequency of the chlorine measuring element, the storage means for storing the relationship, the relationship referenced from the storage means, and the gas to be measured for the chlorine concentration It is more preferable to include a chlorine concentration calculating unit that calculates the chlorine concentration in the gas to be measured based on the frequency measured by the frequency measuring device when it contacts the chlorine measuring element.

  The chlorine measuring method according to the present invention is characterized by including a chlorine measuring step of measuring the resonance frequency by bringing the gas to be measured into contact with the chlorine measuring element.

  As described above, the ammonia measuring element according to the present invention includes a piezoelectric body and electrodes disposed on both sides of the piezoelectric body, and a metal that forms a compound with ammonia exists on the surface of the electrode. The chlorine measuring element according to the present invention includes a piezoelectric body and electrodes disposed on both sides of the piezoelectric body, and a metal that forms chlorine and a compound exists on the surface of the electrode. Therefore, there is an effect that ammonia or chlorine can be measured with high sensitivity and ease.

  Further, in the ammonia measuring element according to the present invention and the chlorine measuring element according to the present invention, since the weight change on the electrode is quantified in the form of frequency change, the measurement value generated for each analyst is read. There is an additional effect that the error can be significantly reduced. In particular, in the form using a crystal resonator, the crystal resonator is a general-purpose product that is used in electrical equipment and the like, and there is also an effect that it is possible to manufacture a portable and small-sized measuring instrument.

  Hereinafter, the present invention will be described in detail.

<1. Ammonia Measuring Element According to the Present Invention>
An ammonia measuring element according to the present invention includes a piezoelectric body and electrodes disposed on both sides of the piezoelectric body, and a metal that forms a compound with ammonia exists on the surface of the electrode.

  In this specification, “a metal that forms a compound with ammonia” means that when it comes into contact with ammonia, it contains at least nitrogen atoms derived from ammonia molecules, hydrogen atoms, and metal elements as constituent elements, and each constituent element is a physical method. Means a metal that forms a compound that cannot be separated any more, and does not mean a metal that only adsorbs and desorbs with ammonia.

  In the present invention, a metal that forms a compound with ammonia is present on the electrode surface. Thus, when ammonia is contained in the measurement target gas, the ammonia and the metal form a compound. This can be measured with higher sensitivity than the method of measuring ammonia by adsorption / desorption as in Patent Document 6. In other words, when reversibility is high like adsorption / desorption, ammonia is frequently adsorbed and desorbed on the electrode surface, so even if a small amount of ammonia is adsorbed, it is immediately desorbed from the electrode surface. End up. Therefore, it is difficult to measure a low concentration. On the other hand, in the present invention, a compound is formed. The formation of the compound is less reversible than the adsorption / desorption, that is, once the compound is formed, ammonia is rarely released immediately. This point is particularly remarkable in molybdenum described later. Therefore, ammonia accumulates on the electrode surface. Therefore, even if ammonia in the gas to be measured has a low concentration, it can be detected with high sensitivity.

[1-1. Piezoelectric material
Specific examples of the piezoelectric body included in the ammonia measuring element according to the present invention are not particularly limited, but include quartz, zinc oxide, Rochelle salt (potassium tartrate-sodium tartrate), lead zirconate titanate, lithium niobate, lithium tantalate, Examples thereof include lithium tetraborate, langasite, aluminum nitride, tourmaline, and polyvinylidene fluoride. Among these, quartz having excellent performance with respect to frequency accuracy and stability is preferable.

  There are various cut types of quartz, and the temperature dependence differs depending on the cut type. Specific examples of the crystal cut type that the ammonia measuring element according to the present invention includes as a piezoelectric body include, but are not limited to, AT cut, DT cut, SL cut, XY cut, CT cut, BT cut, and the like. Among them, an AT-cut quartz that is hardly affected by temperature at −20 ° C. to 60 ° C. is preferable.

  The resonance frequency of quartz is determined by the outer shape. For example, a frequency band of several MHz to several tens of MHz, and as an AT-cut thickness-slip-shaped quartz crystal, a rod-shaped artificial quartz crystal is cut into a plate at a predetermined angle with respect to the crystal axis, and a round plate, a rectangle, a strip A crystal piece such as the above may be used. In such AT-cut quartz, the resonance frequency is determined by the thickness of the quartz piece. Therefore, the plate surface of the crystal piece may be polished according to the desired resonance frequency.

  Further, as a similar element, there is a SAW device (surface acoustic wave element), which can be used instead of the quartz exemplified here.

  In addition, in the method of measuring weight change using a crystal resonator, it is known that the amount of change in the oscillation frequency proportional to the weight change increases by increasing the fundamental oscillation frequency of the crystal resonator due to the measurement principle. ing. Therefore, for high-sensitivity measurement, a fundamental oscillation frequency (for example, a 30 MHz crystal resonator) that is higher than the fundamental oscillation frequency (9 MHz crystal resonator) of the crystal resonator used in the embodiments described later. A thing may be used.

[1-2. electrode〕
As an electrode with which the ammonia measuring element which concerns on this invention is equipped, the metal which forms a compound with ammonia should just exist on the surface. Due to the presence of a metal that forms a compound with ammonia on the surface of the piezoelectric body, when ammonia to be measured comes into contact with the electrode, the ammonia chemically reacts with the metal and changes in mass (increases). Since the frequency characteristics of the quartz crystal resonator change proportionally, it is possible to easily determine ammonia in a short time by measuring this frequency. Moreover, since it is not necessary to use the sensitive film | membrane used by the method of patent document 6, the influence of humidity can be suppressed.

  The method for forming the electrode on the piezoelectric body is not particularly limited as long as a conventionally known method can be arbitrarily adopted. For example, a known means such as vacuum deposition or sputtering may be used to form excitation electrodes on the opposite surfaces, and the excitation electrodes may be led to both side edges. According to these methods, a homogeneous and dense thin film can be formed.

  Then, sandwiched between the distal ends of a pair of terminals provided at the base portion on both side edges of the piezoelectric body with a fixed holding member, and a conductive adhesive or the like is applied and fixed thereto, and mechanically It is preferable to hold and electrically connect the excitation electrode and the terminal.

  The thickness of the electrode formed on the piezoelectric body may be, for example, 5 to 500 nm, and preferably 50 to 400 nm. In addition, the size (area) of the electrode with respect to the piezoelectric plate may be arbitrary as long as the measurement does not hinder the measurement, but the diameter is preferably 1 to 10 mm, more preferably 2 to 7 mm.

  The electrode included in the ammonia measuring element according to the present invention is only required to have a metal that forms a compound with ammonia on the surface. The metal and another metal may be mixed so that a metal that forms a compound with ammonia exists on the surface, or the surface of the electrode made of another metal is coated with a metal that forms a compound with ammonia. The electrode itself may be composed of a metal that forms a compound with ammonia. When the electrode itself is made of a metal that forms an ammonia compound, a thin film of chromium, nickel, titanium, or the like may be provided between the piezoelectric body and the electrode in order to improve adhesion.

  In order to construct the electrode itself with a metal that forms a compound with ammonia, it is preferable to carry out according to the above-described method. In order to coat the electrode surface with ammonia or a metal that forms a compound with chlorine, a known method such as vapor deposition or sputtering may be used.

  By the way, alkali metal such as sodium can be used as a metal that forms a compound with ammonia, but it is unstable under general environment (normal temperature and normal pressure). It is preferable to use molybdenum.

Specifically, molybdenum combines with ammonia to form an ammonium paramolybdate {(NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O} compound. In other words, in the ammonia measuring element according to the present invention, when molybdenum is used as the metal that forms a compound with ammonia, the mass change is caused by the reaction between molybdenum and ammonia, and as a result, the change in frequency characteristics is detected. Therefore, the ammonia concentration can be measured.

  In the present invention, in a form in which molybdenum is used as a metal that forms a compound with ammonia, it is difficult to form a compound with oxygen, nitrogen, carbon dioxide, and ethanol. Therefore, the amount of adsorption by the electrode having molybdenum on the surface is very small with respect to oxygen, nitrogen and other gases existing in normal environments (residential spaces, factory sites, etc.) and concentration ranges. In other words, it can be said that the selectivity for ammonia is very high in a normal environment. In addition, the reaction between molybdenum and ammonia rapidly proceeds to form a compound even if the amount of ammonia is small, so that the ammonia concentration can be measured sensitively and easily.

  Incidentally, molybdenum is an effective metal not only for ammonia measurement but also for chlorine measurement. When ammonia is measured in the above normal environment, there is almost no environment coexisting with chlorine, so there is almost no influence of chlorine when measuring ammonia. Similarly, it can be said that ammonia is hardly affected when measuring chlorine. In addition, it is considered that detecting chlorine at the time of ammonia measurement is not a big problem from the viewpoint of gas management safety. This is because even when chlorine is actually detected when measuring ammonia, the user can perform safety management by checking the gas based on the measured value, and can recognize chlorine gas leaks, etc. .

  Moreover, in patent document 6, gas other than ammonia and chlorine may be detected. However, correspondence to gases other than the measurement target gas is not disclosed. From this, it can be said that the embodiment in which molybdenum is used as the metal in the present invention is a method in which ammonia has a higher selectivity than the prior art.

  In addition, the electrode of the ammonia measuring element according to the present invention contains other components (organic component, metal salt, etc.) within a range not impairing the effects of the present invention, in addition to the metal that forms a compound with ammonia. There is no problem.

  Moreover, it is preferable that the surface of an electrode is mirror-finished. The influence of humidity can be reduced. Although it does not specifically limit as the precision of mirror surface processing, It is more preferable to carry out mirror surface processing of the surface roughness to 0.06 micrometer or less. The lower limit is not particularly limited, and the lower the roughness, the better. When the element surface is in a mirror state, the physical adsorption of water molecules (water) is significantly lower than the general electrode surface state. As a result, even if the target gas contains moisture, the influence of moisture (humidity) can be reduced and the ammonia concentration can be measured. For example, as described in Examples described later, the influence of water can be suppressed to 1/7.

<2. Ammonia Measuring Device According to the Present Invention>
An ammonia measuring apparatus according to the present invention includes an ammonia measuring element and a frequency measuring apparatus that measures the frequency of the ammonia measuring element generated when the surface of the electrode forms a compound with ammonia.

  In order to suppress the influence of humidity as much as possible, a humidity measuring element may be provided as a reference element in addition to mirroring the electrode surface as described above. Examples of the humidity measuring element include a humidity sensor using a polymer film or ceramic as a known element, but it is preferable to further include a humidity measuring element that measures only humidity without being affected by ammonia. An example of a more preferable humidity measuring element is a humidity measuring element that includes a piezoelectric body and electrodes disposed on both sides of the piezoelectric body, and chromium oxide or chromium oxide carrying platinum particles is present on the surface of the electrode. is there. By further providing a humidity measuring element, the influence of humidity can be corrected, and measurement with a reduced influence of humidity can be performed.

  In the case where the humidity measurement element is made of chromium oxide carrying platinum particles, the specific configuration thereof is not particularly limited. For example, the amount of platinum particles supported by chromium oxide is not particularly limited. For example, 10000 ng of platinum particles, preferably 1000 to 15000 ng (per one side) are supported on a chromium oxide electrode having a diameter of 5 mm and a thickness of about 500 nm. It is good to let them. In this case, since platinum does not react with ammonia, correction with higher sensitivity and higher accuracy is possible. Moreover, although it does not specifically limit as a method to carry | support a platinum particle on chromium oxide, What is necessary is just to use easy methods, such as electroplating.

  By correcting the humidity in this way, it can be detected with higher sensitivity. That is, when the humidity is high, ammonia is taken into water molecules and then contacts the electrode surface. Compared with the reaction between gaseous ammonia and metal, the reactivity between the aqueous ammonia solution (water molecules incorporating ammonia) and the metal is high. On the other hand, it can be said that this is easily affected by humidity and a measurement error is likely to occur, but the humidity measurement element can remove the influence of humidity. Therefore, highly sensitive measurement is possible without being affected by humidity.

  In Patent Document 6, a general known humidity detecting element is used to correct the influence in order to remove the influence of humidity. However, the effect of the humidity sensing element on ammonia gas is not shown, and it cannot be said that effective correction is necessarily performed. Therefore, it can be said that the present invention realizes highly sensitive measurement by utilizing the humidity well compared with the prior art.

  An embodiment of an ammonia measuring apparatus according to the present invention will be described with reference to FIG. FIG. 1 is a diagram schematically showing a configuration of an ammonia measuring apparatus 1 according to the present embodiment.

  The ammonia measuring apparatus 1 includes a detection unit 2, a frequency measuring device 3, a calculation unit (calculation unit / ammonia concentration calculation unit) 4, and a storage unit (storage unit) 5.

  The detection unit 2 includes an ammonia measuring element 2a and a humidity measuring element 2b.

  The ammonia measuring element 2a is a crystal resonator for measuring ammonia, and an electrode is formed so as to sandwich the crystal, and molybdenum is present on the surface of the electrode. In addition, the aspect of the ammonia measuring element 2a with which the ammonia measuring apparatus which concerns on this invention is provided is not limited to this, What is contained in the category of the ammonia measuring element which concerns on this invention mentioned above.

  The humidity measuring element 2b is a crystal resonator for measuring humidity, and an electrode is formed so as to sandwich the crystal, and chromium oxide is present on the surface of the electrode. In addition, the aspect of the humidity measuring element 2b with which the ammonia measuring device which concerns on this invention is provided is not limited to this, What is contained in the category of the humidity measuring element with which the ammonia measuring device which concerns on this invention mentioned above is provided.

  The frequency measuring device 3 measures the resonance frequency of the ammonia measuring element 2a according to an increase in weight due to ammonia and a metal present on the electrode surface of the measuring element 2a forming a compound with ammonia. The frequency measuring device 3 also measures the resonance frequency of the humidity measuring element 2b according to an increase in weight due to adsorption of moisture in the gas to be measured without forming a compound with ammonia. . A conventionally known frequency measuring device may be used as the frequency measuring device 3.

  The frequency measuring device 3 is connected to the ammonia measuring element 2 a and the humidity measuring element 2 b, and is also connected to the calculation unit 4 and the storage unit 5 via the calculation unit 4.

  The calculation unit 4 obtains the relationship between the ammonia concentration and the oscillation frequency from the resonance frequency of the ammonia measuring element 2a. The calculation unit 4 outputs the relationship to the storage unit 5. Further, the calculation unit 4 receives the resonance frequency when the gas to be measured comes into contact with the ammonia measuring element 2a from the frequency measuring device 3, and calculates the ammonia concentration in the gas to be measured from the resonance frequency and the above relationship. It is also what is calculated. That is, the calculation unit 4 has both functions of calculation means and ammonia concentration calculation means provided in the ammonia measuring device according to the present invention. The form of the ammonia measuring apparatus according to the present invention is not limited to this, and a calculation unit that functions as a calculation unit and a calculation unit that functions as an ammonia concentration calculation unit may be provided independently. The specific configuration of the calculation unit 4 is not particularly limited, and a conventionally known computer or the like may be used.

  Further, the calculation unit 4 includes means for inputting the ammonia concentration of the gas to be introduced when two or more kinds of known gases having different ammonia concentrations, which will be described later, are introduced into the ammonia measuring device 1.

  The storage unit 5 stores the relationship output from the calculation unit 4. In the present embodiment, the storage unit 5 is externally attached to the calculation unit 4 as shown in FIG. 1, but the storage unit included in the ammonia measuring apparatus according to the present invention is a calculation unit or an ammonia concentration calculation unit. It may be built in or external. In addition, a specific aspect of the calculation means is not particularly limited as long as it can store data related to the above relationship, and may be configured by, for example, a RAM (Random Access Memory) or an HDD (Hard Disk Drive).

  Next, a method for using the ammonia measuring apparatus 1 will be described.

  First, two or more known gases having different ammonia concentrations are brought into contact with the ammonia measuring element 2a, and the frequency measuring device 3 measures the resonance frequency of the ammonia measuring element 2a due to the formation of a compound by ammonia.

  Next, the calculation unit 4 obtains a relationship between the ammonia concentration and the resonance frequency from the resonance frequency received from the frequency measuring device 3 and the ammonia concentrations of the two or more kinds of gases input in advance. Specifically, the two or more kinds of gases are introduced into the detection unit 2 and brought into contact with the ammonia measuring element 2a. At this time, the ammonia concentration of the gas to be introduced is input to the calculation unit 4. Further, the calculation unit 4 calculates and removes only the frequency change corresponding to the humidity effect measured through the humidity measuring element 2b. Thereby, the calculation part 4 can grasp | ascertain at least 2 frequency corresponding to ammonia concentration from which the influence of humidity was removed. Then, the relationship between the ammonia concentration and the frequency can be obtained from these two points. Next, the above relationship is output to the storage unit 5. What is necessary is just to memorize | store the said relationship as a relational expression, for example.

  Next, when the gas to be measured comes into contact with the ammonia measuring element 2a and the humidity measuring element 2b, the frequency measuring device 3 sends the frequency of each element to be measured to the calculating unit 4. The calculation unit 4 refers to the relationship between the ammonia concentration and the frequency from the storage unit 4 and calculates the ammonia concentration in the gas to be measured.

<3. Ammonia Measurement Method According to the Present Invention>
The ammonia measuring method according to the present invention may include an ammonia measuring step of measuring the resonance frequency by bringing the gas to be measured into contact with the ammonia measuring element according to the present invention.

  As a specific method of the ammonia measuring step, there is no particular limitation as long as the gas to be measured is brought into contact with the ammonia measuring element according to the present invention. The temperature and pressure when the gas is brought into contact with the ammonia measuring element are not particularly limited, and may be performed at normal temperature and normal pressure. In a form in which molybdenum is used as a metal forming a compound with ammonia, normal temperature (20 to 40 ° C., preferably 20 to 25 ° C.), normal pressure (0.95 to 1.05 atm, preferably normal atmospheric pressure). ) Is preferable. Molybdenum suitably forms a compound with ammonia at room temperature and normal pressure, so that ammonia can be easily detected.

  Furthermore, in order to correct the influence of humidity, it is preferable to include a humidity measurement step of measuring the influence of humidity using a humidity measuring element that measures only humidity without being affected by ammonia. More preferably, a humidity measuring element having a piezoelectric body and electrodes installed on both sides of the piezoelectric body and having chromium oxide or chromium oxide carrying platinum particles on the surface of the electrode is used to control the influence of humidity. What is necessary is just to include the humidity measurement process to measure.

  The ammonia measuring method according to the present invention can be suitably realized by using the above-described ammonia measuring apparatus according to the present invention.

<4. Chlorine measuring element according to the present invention>
The chlorine measuring element according to the present invention comprises a piezoelectric body and electrodes disposed on both sides of the piezoelectric body, and a metal that forms chlorine and a compound is present on the surface of the electrode.

  In the present specification, “a metal that forms a compound with chlorine” means at least a nitrogen atom derived from a chlorine molecule, a hydrogen atom, and a metal element as constituent elements when contacted with chlorine, and each constituent element is a physical method. Means a metal that forms a compound that cannot be separated any more, and does not mean a metal that only adsorbs and desorbs with chlorine.

[4-1. Piezoelectric material
Regarding the piezoelectric body provided in the chlorine measuring element according to the present invention, the description in the section [1-1] can be applied mutatis mutandis.

[4-2. electrode〕
As an electrode with which the chlorine measuring element which concerns on this invention is equipped, the metal which forms a compound with chlorine should just exist on the surface. When there is a metal that forms a compound with chlorine on the surface of the piezoelectric body, when the electrode comes into contact with the chlorine to be measured, the chlorine chemically reacts with the metal and changes in mass (increases). Since the frequency characteristics of the quartz crystal resonator change proportionally, chlorine can be determined easily in a short time by measuring this frequency. Moreover, since it is not necessary to use the sensitive film | membrane used by the method of patent document 6, it can detect with high sensitivity.

  Regarding the method of forming an electrode on the piezoelectric body and the mode of the electrode, the description in [1-2] above can be applied mutatis mutandis.

  As a metal which forms a compound with chlorine, copper, magnesium, molybdenum etc. are mentioned, for example. Among these, molybdenum is preferable because there are very few substances that react in a general environment. Molybdenum is hardly affected by moisture, ethanol, oxygen, and the like, which have been obstructing the measurement of chlorine in conventional apparatuses, and are difficult to form a compound. In other words, in the chlorine measuring element according to the present invention, when molybdenum is used as a metal that forms a compound with chlorine, molybdenum reacts with chlorine to become molybdenum pentachloride, which changes in mass (increases) and is proportional to the change. Since the change of the frequency characteristic is detected, the chlorine concentration can be measured. In addition, the reaction between molybdenum and chlorine proceeds rapidly even when the amount of chlorine is small, and since the influence of humidity is further suppressed, it proceeds even under high humidity conditions, and the chlorine concentration is sensitive. And can be measured easily. In addition, the electrode of the chlorine element according to the present invention contains other components (organic components, metal salts, etc.) within the range not impairing the effects of the present invention, in addition to the metal forming the compound with chlorine. There is no problem. Moreover, it is preferable that the surface of an electrode is mirror-finished. Regarding the mirror finishing, the description in the above section [1-2] can be applied.

<5. Chlorine measuring device and chlorine measuring method>
The chlorine measuring device according to the present invention comprises the chlorine measuring device according to the present invention, and a frequency measuring device for measuring the frequency of the chlorine measuring device generated when the surface of the electrode forms a compound with chlorine. That's fine.

  In addition, when two or more known gases having different chlorine concentrations contact the chlorine measuring element, the frequency of the chlorine measuring element measured by the frequency measuring device when the chlorine forms a compound. From the calculation means for obtaining the relationship between the chlorine concentration and the oscillation frequency, the storage means for storing the relationship, the relationship referenced from the storage means, and the gas to be measured for the chlorine concentration is in contact with the chlorine measuring element It is preferable that the apparatus further comprises chlorine concentration calculating means for calculating a chlorine concentration in the measurement target gas based on the frequency measured by the frequency measuring device.

  The description of each means of the chlorine measuring device according to the present invention can be applied to the description of the ammonia measuring device according to the present invention. In other words, the chlorine measuring device according to the present invention is obtained by replacing the ammonia measuring element included in the ammonia measuring device according to the present invention with the chlorine measuring device according to the present invention. Reference may be made to the description of the corresponding means.

  Moreover, the chlorine measuring method according to the present invention may include a chlorine measuring step of measuring the resonance frequency by bringing the gas to be measured into contact with the chlorine measuring element according to the present invention. About description of a chlorine measurement process, description of the above-mentioned ammonia measurement process can apply mutatis mutandis. That is, preferable temperature conditions and pressure conditions are the same as those in the ammonia measurement step.

  As a specific method of the chlorine measuring step, the measuring object may be brought into contact with the chlorine measuring element according to the present invention, and is not particularly limited.

  The chlorine measuring method according to the present invention can be suitably realized by using the chlorine measuring device according to the present invention.

<6. Application of the present invention>
The ammonia measuring element according to the present invention can measure the concentration of ammonia gas with high sensitivity and ease. Further, according to the chlorine measuring element according to the present invention, the concentration of chlorine gas can be measured with high sensitivity and ease.

  Furthermore, in the ammonia measuring element according to the present invention and the chlorine measuring element according to the present invention, since the weight change on the electrode is quantified in the form of frequency change, the measurement value generated for each analyst is read. The error can be remarkably reduced. In particular, in the form using a crystal resonator, it is a general-purpose product that is used in electrical equipment etc. if it is a crystal resonator that does not contain a metal that forms a compound with ammonia and a metal that forms a compound with chlorine on the electrode surface. It is possible to produce a portable and small-sized measuring instrument.

  From the above, it can be used for measurement of management concentration in the field environment such as chemical industry factory, measurement of bad odor in the environment of living space, management measurement in museums and museums, and indoor environment measurement in hospitals and nursing homes. . In particular, it can be used for an early detection system for excrement of a care patient whose demand is expected to increase in the future.

  Examples will be shown below, and the embodiments of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention. Moreover, all the literatures described in this specification are used as reference.

[Example 1]
The configuration of the apparatus (experimental apparatus 10) used in this example will be described with reference to FIG. In this example, measurement was performed by putting ammonia water of an arbitrary concentration as a reagent in a closed bottle in a laboratory and generating vaporized ammonia of an arbitrary constant concentration by air.

  The experimental apparatus 10 used in this example includes a thermostatic device 11, a compressor 12, a filter 14 with a dehumidifying agent, an oscillation frequency measuring device 19, and flow meters 13a and 13b. In addition, the thermostatic device 11 includes a sealed bottle 15, a mixing unit (T-shaped tube) 16, a QCM measuring unit 17, and a gas detection tube 18. The gas detection tube 18 is used for calibration and is connected to the QCM measurement unit 17. The gas detector tube was manufactured by Gastec Corporation, No. 3La was used. An experiment may be performed by a suction method using a suction pump instead of the compressor 12.

  In general, a gas detection tube is filled with a chemical that chemically reacts with the gas to be measured in a glass tube, and the chemical undergoes a chemical reaction with the gas to be measured and changes color, and is printed on the surface of the gas tube. It is a simple gas concentration meter for reading the length of color change from a scale for reading gas concentration and converting it as gas concentration.

  The quartz crystal used this time is vapor-deposited or sputtered with titanium metal with a diameter of about 5 mm at the center on the front and back of the quartz plate formed as an element, and molybdenum metal with the same diameter is vapor-deposited or sputtered on it. An element prepared by using a known method of forming a film was used. In the case of a quartz resonator, in order to increase the adhesion between the quartz plate and the electrode metal (so as not to be peeled off), a method for forming a base metal and a metal thin film thereon is a known and general method. Yes.

  The thermostat 11 can maintain a constant temperature state. Except for the devices such as the compressor 12 and the oscillation frequency measuring device 19 that can ignore the influence of temperature at the time of the experiment, the experiment was performed in the thermostatic device 11. Air was used as the supply gas. The supply gas may be any gas that does not affect the measurement system, and may be nitrogen, for example.

  The specific experimental method is as follows. First, air was introduced from the compressor 12 through piping and flow meters 13a and 13b. Air was introduced from one pipe into the sealed bottle 15 containing ammonia water. Here, in the sealed bottle 15 containing ammonia water, the saturation concentration depends on the temperature of the thermostatic device 11. Therefore, this vaporized ammonia in a saturated state was introduced into the QCM measurement unit 17 in which a crystal resonator element for performing measurement was installed. Thus, the air was introduced into the QCM measurement unit 17 via the connection pipe through the sealed bottle 15 containing ammonia and containing the vaporized ammonia. Next, a change in weight caused by the formation of a compound by the electrode metal of the crystal resonator and ammonia contained in the air was converted into a change in frequency by the oscillation frequency measuring device 19 and measured.

  In the present embodiment, a quartz vibrator having a molybdenum electrode is used. The crystal used was AT cut, 9 MHz. That is, the indicated value of the gas detection tube 18 was read in order to compare the resonance frequency value due to weight change and the actual ammonia concentration due to the chemical reaction of ammonia with the molybdenum electrode. Reading of the indicated value of the gas detector tube 18 was performed after the experiment was completed or at a timing that does not affect the experiment, such as in the middle of the experiment. Further, the gas detection tube 18 needs to be corrected according to the temperature and the measured flow rate on the measurement principle. This correction is described as handling of the gas detector tube to be used, and is generally known. In general, when the measured temperature is higher than the reference temperature (room temperature level 20 ° C.), the division is lower. There are many examples of multiplication, but since it differs depending on the gas detector tube, it is better to follow the instructions described in the manual attached to the gas detector tube to be used. As for the flow rate, there are many examples of dividing by a specified flow rate ratio when it is large with respect to a specified suction amount (generally 100 ml), and multiplying by a specified flow rate ratio when it is low. It is recommended to follow the instructions described in the manual attached to the gas detector tube to be used. In this example, the gas detector tube used was No. manufactured by Gastec Corporation. Since it was 3 La, correction was performed as necessary according to the instructions described in this product.

  Here, in order to obtain an arbitrary ammonia concentration, a T-shaped tube 16 is installed between the airtight bottle 15 and the QCM measuring unit 17, and the air sent from the other side of the compressor 12 is mixed here. It has an arbitrary concentration. In this case, an arbitrary concentration is obtained by adjusting the flow rates of the flow meters 13a and 13b attached thereto. A similar experiment can be performed by using an external gas cylinder or the like instead of using the compressor 12 so as not to affect the experiment.

  Using the above apparatus and method, 100 μl of a 25% ammonia concentration solution was vaporized, and measurement was performed under the conditions of an experimental temperature of 20 ° C., a humidity of 80% RH, a flow rate of 200 ml, and a reading value of 3 minutes after the start of the measurement time.

  The results are shown in Table 1 below. A similar experiment was conducted using another metal instead of molybdenum. The results are shown in Table 1. The values in Table 1 show the difference in frequency change at a humidity of 80% RH under the condition where the frequency change at a humidity of 80% RH not containing ammonia is obtained and vaporized at an ammonia concentration of 25%.

  As shown in Table 1, when the electrode was formed of a metal other than the molybdenum electrode, the change in the resonance frequency was slight, but when a molybdenum electrode element was used, a detection sensitivity of about 3000 Hz was obtained.

[Example 2]
Using the measurement apparatus described in Example 1, the ammonia concentration is 100 ppm in each humidity condition, the experimental temperature is 20 ° C., the measurement flow rate is 100 ml, and the frequency change value is measured 3 minutes after the start of the measurement. Measurement was performed using a quartz electrode crystal resonator (both had a fundamental oscillation frequency of 9 MHz). The result is shown in FIG. Here, data for moisture only is also shown for comparison. In FIG. 3, the horizontal axis indicates relative humidity (RH), the vertical axis indicates frequency change, the solid line indicates the result using a gas containing ammonia, and the broken line indicates the result using a gas containing only moisture. The circles indicate the results using the molybdenum electrode, and the crosses indicate the results using the chromium oxide electrode.

  As a result of the experiment, the frequency change of the chromium oxide electrode was almost the same regardless of the presence or absence of ammonia. However, when the humidity of the molybdenum electrode exceeded 60% RH, the frequency change with respect to ammonia increased more than the humidity change. On the other hand, a specific frequency change characteristic was shown.

  The reason why humidity is closely related to the reaction between molybdenum and ammonia is related to the form of the compound produced by molybdenum and ammonia, and molybdenum and ammonia react chemically to become ammonium molybdate. Since this compound takes the form of a hydrate, it has been shown that the reaction of molybdenum with ammonia requires water molecules. This is because the presence of water molecules is important not only for the role as a material necessary for the reaction but also for the role of ionizing ammonia.

Example 3
In this example, using the apparatus described in Example 1 equipped with a quartz crystal resonator (basic oscillation frequency 9 MHz) of molybdenum electrode, relative humidity 80% RH, ammonia concentration 0 to 225 ppm, experimental temperature 20 ° C., start of measurement The frequency change value after 5 minutes is read. The result is shown in FIG. FIG. 4 is a diagram showing ammonia measurement results in the present example, in which the horizontal axis indicates ammonia concentration (ppm) and the vertical axis indicates frequency change (Hz).

  As shown in FIG. 4, it can be seen that there is a proportional relationship between the reading value (ammonia concentration) of the gas detector tube and the change in oscillation frequency. From this, ammonia using the chemical reaction between the metal electrode of the crystal resonator and ammonia. It was found that concentration measurement was possible.

Example 4
In this example, the influence of humidity due to the presence or absence of mirror finishing was confirmed.

  Specifically, using a crystal resonator (mirror surface 0.06 μm) whose surface is mirror-finished and a crystal resonator (rough surface 0.6 μm) which is not mirror-finished, air with a relative humidity of 90% RH is used. The difference in frequency variation was measured by the same method as in Example 1 except that. The results are shown in Table 2.

  As shown in Table 2, due to the influence of humidity (water molecules) due to the difference in the electrode surface shape between the mirror surface crystal resonator and the crystal resonator (rough surface), the mirror surface processing crystal resonator 1/7 or less. Thereby, it was shown that it was hard to be influenced by humidity.

Example 5
In this example, the effect of humidity due to the presence or absence of platinum was confirmed.

  Specifically, a crystal resonator including a chromium oxide electrode supporting platinum and a crystal resonator including a chromium oxide electrode not supporting platinum, except that air having a relative humidity of 80% RH is used. The difference in frequency variation was measured by the same method as in Example 1. The results are shown in Table 3.

  As shown in Table 3, as the influence of humidity (water molecules) due to the difference between the quartz vibrator of the chromium oxide electrode and the quartz vibrator of the platinum oxide electrode carrying platinum, when using the electrode carrying platinum, It was shown that it is 5 times more susceptible to humidity than an electrode not carrying platinum.

  The ammonia measuring element, the ammonia measuring device and the ammonia measuring method according to the present invention include a management concentration measurement in a field environment such as a chemical industrial factory, a bad odor measurement in an environment such as a living space, a management measurement in a museum or a museum, a hospital It can be used to measure the indoor environment in nursing homes. In particular, it can be used for an early detection system for excrement of a care patient whose demand is expected to increase in the future.

  In addition, the chlorine measuring element, chlorine measuring apparatus and chlorine measuring method according to the present invention determine the management concentration in a field environment such as a chemical industrial factory, the management concentration measurement in a bleaching / sterilization site, etc., and determine the presence or absence of harmful gases. Can be used for screening equipment.

It is a figure which shows typically the structure of one Embodiment of the ammonia measuring apparatus which concerns on this invention. It is a figure which shows typically the structure of the ammonia measuring apparatus used in Example 1. FIG. It is a figure which shows the ammonia measurement result in Example 2. FIG. It is a figure which shows the ammonia measurement result in Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ammonia measuring device 2 Detection part 2a Ammonia measuring element 2b Humidity measuring element 3 Frequency measuring device 4 Calculation part 5 Memory | storage part

Claims (10)

An ammonia measuring element comprising a piezoelectric body and electrodes disposed on both sides of the piezoelectric body, wherein a metal that forms a compound with ammonia exists on the surface of the electrode, and the metal is molybdenum .   2. The electrode according to claim 1, wherein a surface of the electrode is coated with a metal that forms a compound with ammonia or a metal that forms a compound with ammonia. Ammonia measuring element.   The ammonia measuring element according to claim 1, wherein the surface of the measuring element is mirror-finished. The ammonia measuring element according to any one of claims 1 to 3, and a frequency measuring device for measuring a frequency of the ammonia measuring element generated when the surface of the electrode forms a compound with ammonia. An ammonia measuring device characterized by the above. It is further equipped with a humidity measuring element that measures only humidity without being affected by ammonia,
The humidity measuring element includes a piezoelectric body and electrodes installed on both sides of the piezoelectric body, and chromium oxide or chromium oxide carrying platinum particles is present on the surface of the electrode. The ammonia measuring device according to claim 4. When two or more kinds of known gases having different concentrations of ammonia are in contact with the ammonia measuring element, the frequency of the ammonia measuring element is measured by the frequency measuring device, and the ammonia forms a compound. A calculation means for obtaining the relationship between the ammonia concentration and the oscillation frequency;
Storage means for storing the relationship;
The ammonia concentration in the measurement target gas based on the frequency measured by the frequency measurement device when the measurement target gas of the ammonia concentration is in contact with the relationship referred to from the storage means. Ammonia concentration calculating means for calculating
The ammonia measuring device according to claim 4, comprising: A chlorine measuring element comprising a piezoelectric body and electrodes disposed on both sides of the piezoelectric body, wherein a metal that forms chlorine and a compound is present on the surface of the electrode, and the metal is molybdenum . 8. The electrode according to claim 7, wherein the surface of the electrode is covered with a metal that forms a compound with chlorine or a metal that forms a compound with chlorine. Chlorine measuring element. A chlorine measuring element according to claim 7 or 8, and a frequency measuring device for measuring a frequency of the chlorine measuring element generated when the surface of the electrode forms a compound with chlorine. Chlorine measuring device. When two or more kinds of known gases having different chlorine concentrations come into contact with the chlorine measuring element, the frequency is measured by the frequency measuring device, and from the frequency of the chlorine measuring element by the chlorine forming a compound, A calculation means for obtaining the relationship between the chlorine concentration and the oscillation frequency;
Storage means for storing the relationship;
Based on the frequency measured by the frequency measuring device when the gas to be measured for the chlorine concentration comes into contact with the chlorine measuring element, the chlorine concentration in the gas to be measured is referred to from the storage means Chlorine concentration calculating means for calculating
The chlorine measuring device according to claim 9, comprising:

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