JP3639123B2 - Nitrogen dioxide gas detection method, nitrogen dioxide gas detection element, and nitrogen dioxide gas detection device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nitrogen dioxide gas detection method, a nitrogen dioxide gas detection element, and a nitrogen dioxide gas detection device using the same.
[0002]
[Prior art]
Currently SO₂, NO_xThe impact on the environment is a problem. SO₂, NO_xIs generated by the combustion of fossil fuels and causes acid rain and photochemical smog. In Japan, for example, nitrogen dioxide (NO₂ ) Environmental standards are set for concentrations, and gas concentrations are measured at various monitoring stations using automatic measurement methods. As an environmental standard, the average value per day per hour is approximately 60 ppb or less.
[0003]
These gas concentration measuring devices can measure a very small amount of gas of several ppb, but are expensive and require maintenance. In addition, in the case of automatic measurement, there are many restrictions such as enormous expenses such as electric power and the necessity of securing a power source and an installation location. However, in order to accurately conduct gas concentration distribution surveys and global environmental impact assessments, it is necessary to monitor the environment on a nationwide scale with more observation points. For this reason, it is conceivable to use gas sensors or simple measurement methods (or monitoring devices) that are inexpensive, small and easy to use.
[0004]
Currently, a wide range of developments such as semiconductor gas sensors, solid electrolyte gas sensors, electrochemical gas sensors, and quartz oscillation gas sensors are underway. However, these were developed to evaluate the response in a short time, and few were developed for monitoring that requires data accumulation. Further, since the detection sensitivity is about 1 ppm, the concentration of the actual environment (for example, NO_xHowever, about 10 ppb) cannot be dealt with. In many cases, the influence of other gases cannot be ignored.
The method using the detector tube type gas measuring device was also developed for the purpose of measuring in a short time on the spot, and it is difficult to use it cumulatively. Furthermore, there are problems such as that the measurer has to go to the site, and individual differences occur when reading colors. In many cases, interference or other interference of other gases becomes a problem.
[0005]
As a simple measurement method, air is taken in by a pump and NO._xGas is collected directly in a sampling bag (direct collection method), collected with a solid adsorbent (solid collection method), or collected in an absorbent (liquid collection method), and the collected gas is gas chromatographed. The analysis method is generally used.
However, both methods require transportation of peripheral devices such as pumps as well as samples. The direct collection method is difficult to accumulate due to the limited size of the sampling bag. The solid collection method and the liquid collection method have a problem that a process for detecting the collected gas is necessary.
[0006]
As a simple monitoring method that does not require suction or the like, the use of a passive sampler for environmental measurement has attracted attention. NO_xExamples of passive samplers for use include a nitrate plate method and a triethanolamine (TEA) badge method. The effects of wind speed, temperature, and humidity are examined, and quantitativeness is examined. On the other hand, the measurement after sampling is generally performed by washing the sample into a solution and analyzing the sample by ion chromatography or absorptiometry. However, these samplers have a problem in that it takes time and effort to wash them before they are collected and analyzed.
[0007]
As a technique for solving the above problems, after reacting nitrogen dioxide gas with the detection agent adsorbed in the pores of the porous body, which is a transparent matrix adsorbent, the visible UV absorption spectrum of the transmission is obtained by a spectrophotometer. There has been proposed a nitrogen dioxide gas detection method characterized by measuring and detecting the amount of nitrogen dioxide gas. However, in this detection method, since a highly reactive agent is used as a detection agent, a side reaction occurs, and the sensitivity in the visible UV absorption spectrum of the reaction product with the target nitrogen dioxide gas does not increase, and There is a problem that the side reaction product interferes with the visible UV absorption spectrum and sufficient accuracy cannot be obtained.
[0008]
[Problems to be solved by the invention]
To summarize the above, conventionally, if nitrogen dioxide gas is to be detected with high accuracy in the order of ppb in accordance with the environmental standard value, an expensive and large-scale apparatus configuration is required, and it takes time and effort to easily remove nitrogen dioxide gas. There was a problem that could not be detected.
[0009]
The present invention has been made to solve the above-described problems, and an object thereof is to make it possible to detect nitrogen dioxide gas more easily and accurately.
[0010]
[Means for Solving the Problems]
In the method for detecting nitrogen dioxide gas according to the present invention, first, a diazotizing reagent that reacts with nitrite ions to form a diazo compound, a coupling reagent that couples with a diazo compound to form an azo dye, and an acid mixture are firstly transparentized. A sensing element arranged in a hole of a porous body is prepared. Next, the light transmittance of the sensing element is measured to obtain the first transmittance. Next, this sensing element is exposed to the gas to be measured for a predetermined time. Next, after that, the light transmittance of the sensing element is measured to obtain the second transmittance. The nitrogen dioxide gas in the gas to be measured is detected from the difference between the first transmittance and the second transmittance.
As a result of this configuration, when the sensing element is exposed to an atmosphere in which nitrogen dioxide gas exists, nitrite ions and diazotizing reagent due to the nitrogen dioxide gas adsorbed in the pores of the sensing element are diazotized to produce a diazo compound, The diazo compound and the coupling reagent are coupled to produce an azo dye. Therefore, since the sensing element is colored and a difference occurs between the first transmittance and the second transmittance, nitrogen dioxide gas can be detected by this.
[0011]
Further, the nitrogen dioxide gas sensing element of the present invention comprises a transparent porous body, a diazotization reagent that is disposed in the pores of the porous body and reacts with nitrite ions to generate a diazo compound, and a pore of the porous body A coupling reagent that is arranged together with a diazotizing reagent to couple with a diazo compound to produce an azo dye, and an acid that is arranged with a diazotizing reagent in the pores of the porous body.
As a result of this configuration, when nitrogen dioxide gas enters the nitrogen dioxide gas detection element and adsorbs nitrogen dioxide, the resulting nitrite ions react with the diazotization reagent to produce a diazo compound. And this and a coupling reagent couple | bond together and an azo pigment | dye is produced | generated, Therefore The state which colored the detection element of nitrogen dioxide gas will be in it.
[0012]
  The nitrogen dioxide gas detection device according to the present invention includes a light emitting portion that emits light, and an electric signal corresponding to the amount of light received by the light receiving surface, the light receiving surface being disposed opposite the light emitting surface of the light emitting portion. At least a light detection unit that outputs light, a detection element disposed between the light emission unit and the light detection unit, and an electric meter that measures the state of the electrical signal output by the light detection unit. A porous body, a diazotizing reagent that is arranged in the pores of the porous body and reacts with nitrite ions to form a diazo compound, and a diazotizing reagent that is placed in the pores of the porous body together with the diazo compound. Consists of a coupling reagent that produces azo dyes and an acid that is placed in the pores of the porous body together with the diazotizing reagentThen, nitrogen dioxide gas in the gas to be measured is detected by measuring the transmittance of the light transmitted through the sensing element.I tried to do it.
  As a result of this configuration, when nitrogen dioxide gas enters the pores of the sensing element and nitrogen dioxide is adsorbed, the resulting nitrite ions react with the diazotization reagent to produce a diazo compound. Since the coupling reagent couples to produce an azo dye, the sensing element is colored. On the other hand, since the light emitted from the light emitting part is incident on the light detecting part via the sensing element, the change in the color of the sensing element is measured by the electric meter as the change in the electrical signal output from the light detecting part. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
Embodiment 1
First, nitrogen dioxide (NO) in the first embodiment of the present invention.₂) A gas detection method will be described. First, a method for producing a nitrogen dioxide gas sensing element will be described. As shown in FIG. 1A, an aromatic amine sulfanilic acid (SA) as a diazotizing reagent and N, N as a coupling reagent. -A detection agent solution 101 in which dimethylnaphthylamine (N, N-dimehtylnaphthylamine: DMNA) is dissolved in a mixed solution of water and ethanol is prepared in a container 102. Here, the concentration of sulfanilic acid was 0.02 mol / l.
[0014]
Next, as shown in FIG. 1 (b), a porous body 103, which is porous glass having an average pore diameter of 4 nm, was immersed in the detection agent solution 101. As the porous body 103, Vycor 7930 manufactured by Corning was used. This Vycor 7930 has an average pore diameter of 4 nm. In addition, the porous body 103 had a chip size of 8 (mm) × 8 (mm) and a thickness of 1 (mm).
Further, this Vycor 7930 is borosilicate glass, and when heated, the alkali component and other components centering on silicon are separated, and acid treatment is performed in this state to elute the alkali component, It is a thing. As described above, since the acid treatment is performed in the manufacturing process, the inside of the pores of the Vycor 7930 is an acidic environment. That is, the acid is present in advance.
[0015]
In addition, when the inside of the hole of a porous body is not in an acidic state, what is necessary is just to make it the state which the acid existed by making the inside of a hole into an acidic environment by acid cleaning etc. beforehand. And at this time, the porous body should just be pH1, for example. Note that a porous body made of an organic polymer may be used as the transparent porous body.
The porous body 103 shown above is immersed in the detection agent solution 101 for 2 hours, impregnated with the detection agent solution in the pores of the porous body 103, and then air-dried, and as shown in FIG. The sensing element 103a is produced by leaving it to stand for half a day in a nitrogen gas stream and drying. Although the sensing element is plate-shaped here, it is not limited to this and may be formed in a fiber shape.
[0016]
Next, a method for detecting nitrogen dioxide gas using the sensing element 103a will be described. First, as shown in FIG. 1 (d), the absorbance in the thickness direction of the sensing element 103a is measured. In FIG. 1D, I₀Is the incident signal light intensity, and I is the transmitted light intensity.
Next, as shown in FIG. 1E, for example, the sensing element 103a is exposed to the air 104 to be detected in which nitrogen dioxide having a concentration of 300 ppb exists for about 3 hours. Then, the sensing element 103a is taken out from the air 104 to be detected, and the absorbance in the thickness direction of the sensing element 103a is measured again as shown in FIG. 1 (f).
[0017]
The results of the two absorbance measurements (absorbance analysis) are shown in FIG. The transmitted light measurement wavelength of 350 nm or less is not measured due to the absorption of the porous glass (Vycor 7930) constituting the sensing element itself. In FIG. 2, the measurement result of the absorbance before exposure to the air to be detected is indicated by a broken line, and the measurement result of the absorbance after exposure is indicated by a solid line.
First, in both the solid line and the broken line, the absorption that seems to be absorption of water is in the vicinity of wavelengths of 1350 nm and 1900 nm. This absorption varied depending on the humidity of the air to be detected and the leaving time of the sensing element. Therefore, in the method for detecting nitrogen dioxide gas using the sensing element of the first embodiment, the effective measurement wavelength range is determined to be 350 to 1000 nm.
[0018]
And a big change is seen between a continuous line and a broken line in wavelength 400-600 nm especially 530 nm vicinity. That is, in the measurement of the absorbance after exposure to the detection target air, absorption at a wavelength of 530 nm appears. Therefore, a new substance having light absorption with a wavelength of 530 nm is generated in the sensing element by exposure to the detection target air. And this production | generation substance can be estimated to be the azo pigment | dye produced | generated by coupling N, N- dimethyl naphthylamine to the diazo compound produced | generated by the reaction of sulfanilic acid and nitrite ion. Nitrogen dioxide turns into nitrite ions when dissolved in water. Moreover, since the absorption peak which newly appeared is one, it can confirm that the other side reaction has not occurred.
[0019]
As described above, the sensing element that is a porous body is first a transparent matrix adsorbent having a plurality of holes 301 having an average pore diameter of 20 nm or less, for example, as shown in FIG. A diazotization reagent and a coupling reagent are disposed together with an acid in the hole 301 of the detection element (porous body) 302. When such a porous body is exposed to the air, the moisture in the air is actually adsorbed in the pores to form a thin water film. As a result, a thin film 303 of an aqueous solution (detection agent solution) in which a diazotization reagent, a coupling reagent, and an acid are dissolved is formed on the inner wall of the hole 301 of the detection element 302 that is a porous body. Yes.
Then, the nitrogen dioxide molecules 304 that have entered the hole 301 encounter them and cause the following two reactions.
[0020]
First, as shown in FIG. 3B, nitrite ions 311 generated by dissolving nitrogen dioxide in water and sulfanilic acid 312 which is a diazotization reagent react (diazotization), and diazo compound 313 is obtained. Is generated.
The diazo compound 313 and the coupling reagent N, N-dimethylnaphthylamine 314 are coupled to produce an azo compound (coupling compound) 315. Here, azo compounds (azo dyes) generally have light absorption in any wavelength region within 200 to 2000 nm. For example, the azo compound 315 shown in FIG. 3C is known to have an absorption wavelength in the vicinity of 500 to 550 nm. This agrees with the result shown in FIG.
[0021]
Therefore, for example, if the absorption spectrum is measured with a spectrophotometer (absorptiometer), the azo compound can be detected (quantified).
In the diazotization, an aromatic primary amine (ArNH) is used in the presence of 2 equivalents or more of acid.₂) And nitrite ion (NO)₂ ^-) Reacts with the diazo compound (ArN)₂ ⁺) Is a reaction to make. For this reason, the above-described reaction basically does not occur except for nitrogen dioxide gas. Here, this reaction is ArNH₂+ NO₂ ^-+ 2H⁺→ ArN₂ ⁺+ 2H₂Since the reaction is 0, theoretically, 2 equivalents of acid are required. That is, as described above, it is necessary to dispose (carry) the diazotization reagent and the coupling reagent together with the necessary amount of acid in the pores of the porous body. The above-described reaction can occur even in the gas phase. However, as described above, since there can be no moisture in an actual environment, a thin film of water is substantially formed in the hole of the sensing element. And the above-described reaction will occur in the aqueous solution.
[0022]
And as above-mentioned, nitrogen dioxide gas can be indirectly measured by measuring the azo compound produced | generated as a result by nitrogen dioxide gas adsorb | sucking by light absorption. Here, for example, if the porous body is made of a material that transmits light in the light absorption wavelength region of the azo compound, the adsorbed nitrogen dioxide can be obtained by measuring the light absorption characteristics of the porous body adsorbed with nitrogen dioxide gas. Gas can be detected.
[0023]
In the first embodiment, as described above, the measurement results are obtained by exposing the sensing element to air having a nitrogen dioxide concentration of 300 ppb for 3 hours. As a result of the measurement of absorbance, as shown in FIG. 2, the change in absorbance at a wavelength of 530 nm is as high as about 0.1, and highly sensitive sub-ppm level nitrogen dioxide gas can be detected. The measurement can be performed simply by placing the sensing element of the first embodiment in the thin film measurement holder of the absorptiometer. And if the relationship between the difference in absorbance and the concentration is obtained, the ppb level can be quantified.
The change in absorbance at the maximum absorption wavelength per exposure amount (concentration (ppb) × exposure time (hour)) was determined as a sensitivity index. In the case of the first embodiment (FIG. 2), the absorbance change when exposed to 300 ppb nitrogen dioxide gas for 3 hours is 0.1, and the sensitivity index is 1.1 × 10 6.^-Fourppb^-1・ Hr^-1Thus, a very high sensitivity was obtained.
[0024]
By the way, as the diazotizing reagent, for example, an aromatic compound such as benzene, naphthalene, or biphenyl or a heteroaromatic compound such as thiophene or thiazole, which has a primary amino group or an acetamide group may be used. Further, as a coupling reagent, an aromatic compound such as benzene, naphthalene, biphenyl or a heteroaromatic compound such as thiophene or thiazole, which has an amino group (1 to 3), an alkoxy group, or a hydroxyl group may be used. Good.
[0025]
Further, as described above, as a method for introducing the diazotization reagent and the coupling reagent into the pores of the porous body, as described above, both the impregnation of the porous body as a solution, introduction into the pores and drying, There is a method of vapor-depositing and introducing it into the hole, and a method of melting and introducing both into the hole. In these cases, an acid environment may be obtained by introducing an acid into the pores of the porous body in advance. In addition, there is a method in which both are used alone or mixed with other compounds and introduced into the pores when a porous body is produced by the sol-gel method.
As described above, according to the first embodiment, since the sensing element including the diazotization reagent and the coupling reagent is used in the pores of the porous body, the adsorption area of the nitrogen dioxide gas to be detected increases. In addition, the sensitivity and the storage capacity can be increased as compared with the conventional method.
[0026]
Further, since the porous body constituting the sensing element has a high transmittance in the wavelength region of approximately 400 to 1000 nm, nitrogen dioxide is adsorbed to the sensing element by measuring the transmittance of the sensing element. Thus, the change in absorbance due to the azo dye produced can be measured. That is, according to the first embodiment, if the absorbance of the sensing element is measured before and after exposing the sensing element to the air to be detected, the nitrogen dioxide gas adsorbed on the sensing element can be detected. Nitrogen dioxide gas can be easily detected. In the measurement of absorbance, it is only necessary to see a change in a single peak, so measurement is easy.
Further, according to the sensing element in the first embodiment, as shown in FIG. 4, when the nitrogen dioxide gas concentration in the air to be measured increases, the light transmittance at a predetermined wavelength of the sensing element decreases. Go. The predetermined wavelength is approximately 530 nm here.
[0027]
As described above, according to the first embodiment, since the nitrogen dioxide gas can be detected by this optical change using a small sensing element, the nitrogen dioxide gas can be detected very easily and accurately. It has the effect.
Here, in the case where the porous body constituting the detection element is made of glass (borosilicate glass), the average pore diameter is set to 20 nm or less, thereby measuring the transmission spectrum in the visible UV wavelength region (wavelength 200 to 2000 nm). In the visible light region (350 to 800 nm), light was transmitted.
However, when the average pore diameter was larger than that, a sharp decrease in transmittance was observed in the visible region.
[0028]
The above results are shown in FIG. In FIG. 5, the dotted line indicates the transmittance of quartz glass, the alternate long and short dash line indicates the transmittance of a porous body made of borosilicate glass having a pore diameter of 2.5 nm, and the solid line indicates the transmittance of Vycor 7930 used in the first embodiment described above. The broken line shows the transmittance of a porous body made of borosilicate glass having a pore diameter of 20 nm. In addition, the sample shown with a dashed-dotted line and a broken line is a product made from a Geltec company (GELTECH). In all cases, the thickness in the transmittance measuring direction was 1 mm.
Therefore, the porous body described above should have an average pore diameter of 20 nm or less. Moreover, a transparent porous body is used in the visible light region of 350 to 800 nm. By the way, in Embodiment 1 mentioned above, the specific surface area of a porous body is 100 m per 1 g.²That's it.
[0029]
Embodiment 2
Next explained is the second embodiment of the invention.
First, a method for producing a sensing element for nitrogen dioxide gas in Embodiment 2 will be described. Sulfanilamide (SFA) as a diazotization reagent, N, N-dimethylnaphthylamine (DMNA) as a coupling reagent, and ethanol A detection agent solution dissolved in the mixed solution is prepared. Here, the concentration of sulfanilamide was 0.02 mol / l, and the concentration of N, N-dimethylnaphthylamine was 0.005 mol / l.
[0030]
Next, a porous body having an average pore diameter of 4 nm was immersed in the detection agent solution. As this porous body, Vycor 7930 made by Corning was used as in the first embodiment. This Vycor 7930 has an average pore diameter of 4 nm. The porous body had a chip size of 8 (mm) × 8 (mm) and a thickness of 1 (mm).
Then, the porous body is immersed in the detection agent solution for 2 hours, impregnated with the detection agent solution in the pores of the porous body, then air-dried, and left to dry in a nitrogen gas stream for half a day. Thus, the sensing element of the second embodiment was produced.
[0031]
FIG. 6 shows absorption spectra before and after exposing the sensing element of the second embodiment to the air to be measured. The broken line shows the state before exposure. The solid line shows the result after exposing the sensing element of the second embodiment for 3 hours in air containing nitrogen dioxide gas having a concentration of 300 ppb.
As apparent from FIG. 6, only one new absorption peak appears in the solid line near the wavelength of 530 nm. This absorption near 530 nm is considered to be due to the azo dye formed as a result of coupling of a diazo compound obtained by diazotizing sulfanilamide and N, N-dimethylnaphthylamine. And the change of the absorbance is as high as about 0.1, and it was found that high-sensitivity ppb level nitrogen dioxide gas can be detected even by detecting nitrogen dioxide gas using the sensing element of the second embodiment. .
Similar to the first embodiment, the sensitivity index for the second embodiment (FIG. 6) is 1.3 × 10 4.^-Fourppb^-1・ Hr^-1It can be seen that very high sensitivity was obtained.
[0032]
Embodiment 3
Next explained is the third embodiment of the invention.
First, a method for producing a sensing element for nitrogen dioxide gas in Embodiment 3 will be described. Acetanilide (AA) as a diazotizing reagent, N, N-dimethylnaphthylamine (DMNA) as a coupling reagent, and ethanol are mixed. A detection agent solution dissolved in the solution is prepared. Here, the concentration of acetanilide (AA) was 0.02 mol / l, and the concentration of N, N-dimethylnaphthylamine was 0.005 mol / l.
Next, a porous body having an average pore diameter of 4 nm was immersed in the detection agent solution. As this porous body, as in the first and second embodiments, Vycor 7930 manufactured by Corning was used. This Vycor 7930 has an average pore diameter of 4 nm. The porous body had a chip size of 8 (mm) × 8 (mm) and a thickness of 1 (mm).
[0033]
Then, the porous body is immersed in the detection agent solution for 2 hours, impregnated with the detection agent solution in the pores of the porous body, then air-dried, and left to dry in a nitrogen gas stream for half a day. Thus, the sensing element of Embodiment 3 was produced.
FIG. 7 shows absorption spectra before and after exposing the sensing element of Embodiment 3 to the air to be measured. The broken line shows the state before exposure. The solid line shows the result after the detection element of Embodiment 3 was exposed to air containing nitrogen dioxide gas having a concentration of 300 ppb for 3 hours.
In the third embodiment, as shown in FIG. 7, new absorption appears in the vicinity of the wavelength of 460 nm on the solid line. Although this absorbance is about 0.03, it is possible to detect ppb level nitrogen dioxide gas with sufficiently high sensitivity.
Similar to the first and second embodiments, the sensitivity index for the third embodiment (FIG. 7) is 3.3 × 10.^-Fiveppb^-1・ Hr^-1It became.
[0034]
Embodiment 4
Next explained is the fourth embodiment of the invention.
First, a method for producing a nitrogen dioxide gas sensing element according to the fourth embodiment will be described.
First, 0.0428 g of N, N-dimethyl-1-naphthylamine (DMNA) was taken as a coupling reagent in an Erlenmeyer flask, and 100 ml of ethanol was added to dissolve it to prepare a solution of about 0.0025 mol / l. .
In another Erlenmeyer flask, 0.6888 g of sulfanilamide was taken as a diazotization reagent, and 100 ml of ethanol was added thereto and dissolved to prepare a solution of about 0.04 mol / l.
[0035]
Next, 10 ml of each of these solutions was taken and mixed to prepare a detection agent solution. This detection agent solution was transferred to a petri dish, and a porous body having an average pore diameter of 4 nm was immersed therein for about 2 hours, and this porous body was impregnated with the detection agent solution. As this porous body, as in the first to third embodiments, Vycor 7930 made by Corning was used. This Vycor 7930 has an average pore diameter of 4 nm. The porous body had a chip size of 8 (mm) × 8 (mm) and a thickness of 1 (mm).
Next, the porous body impregnated with the detection agent solution was taken out from the petri dish and air-dried for 24 hours to evaporate the solvent, thereby obtaining a detection element. The thus produced sensing element was visually colorless and transparent.
[0036]
When this sensing element was exposed to a dry nitrogen atmosphere with a nitrogen dioxide concentration of 200 ppb, its color changed from colorless and transparent to pink when visually observed. As a result of measuring this change with an absorptiometer, a change was observed as shown in FIG. In FIG. 8, the measurement result of the detection element that appeared to be colorless and transparent in the initial stage is indicated by a broken line, and the measurement result of the detection element that has changed to pink is indicated by a solid line. This change was irreversible. Further, when the nitrogen dioxide concentration was changed in the range of 100 ppb to 100 ppm, almost the same spectrum change was observed only with different light absorption intensity.
[0037]
Next, when the sensing element was exposed to the atmosphere (air) having a nitrogen dioxide concentration of 10 ppb, a change as shown in FIG. 9 was observed in the absorbance. In FIG. 9, the measurement result of the sensing element that appeared to be colorless and transparent in the initial stage is indicated by a broken line, and the measurement result after exposure to the specimen air is indicated by a solid line. And this change was also irreversible.
As described above, it is possible to detect nitrogen dioxide gas even using the sensing element in the fourth embodiment, and it is possible to detect nitrogen dioxide gas in the atmosphere.
[0038]
Embodiment 5
The fifth embodiment of the present invention will be described below. Here, a nitrogen dioxide gas detection apparatus using the above-described detection element will be described.
As shown in FIG. 10, this nitrogen dioxide gas detection device irradiates the detection element 1002 with light emitted from a light emitting unit 1001 made of an LED that emits light of a predetermined wavelength, and receives the transmitted light as a light receiving unit. Light is received at 1003. The light receiving unit 1003 photoelectrically converts the received light and outputs a signal current. The conversion amplifier 1004 amplifies the output signal current and performs current-voltage conversion. The A / D conversion unit 1005 converts the voltage signal into a digital signal. The output detection unit 1006 outputs the digital signal as a detection result.
[0039]
Here, the detection element 1002 is, for example, the detection element of the first to fourth embodiments described above. For the light emitting unit 1001, for example, a green LED having an emission wavelength of 530 nm may be used. The light receiving unit 1003 is, for example, a photodiode. As this photodiode, for example, a photodiode sensitive to a wavelength of 190 to 1000 nm may be used. In addition, the light emitting unit 1001 and the light receiving unit 1003 are arranged such that the light emitting part and the light receiving part face each other.
For example, when the detection device using the detection element according to the fourth embodiment detects nitrogen dioxide gas in a dry nitrogen atmosphere having a nitrogen dioxide concentration of 100 ppb to 100 ppm and in the atmosphere (air), the detection element becomes nitrogen dioxide. An output different from the unexposed initial state was obtained.
Thus, according to the fifth embodiment, a nitrogen dioxide gas detection device can be easily configured.
[0040]
Embodiment 6
The sixth embodiment of the present invention will be described below. Below, it demonstrates in detail regarding the detection apparatus of the nitrogen dioxide gas mentioned above. In particular, the configuration of the light emitting unit and the light receiving unit will be described.
In the sixth embodiment, as shown in FIG. 11, an LED 1102 emitting green light having a wavelength of 550 nm and a light receiving surface facing the light emitting surface of the LED 1102 are disposed on a substrate 1101 having a size of about 12 cm × 6 cm. As shown in FIG. This phototransistor has photosensitivity in the wavelength region of 450 to 1100 nm. The LED 1102 and the phototransistor 1103 are supplied with power from two AA batteries 1105 connected in series via a terminal plate 1104.
[0041]
Further, the power supply can be turned on / off by a switch 1106. That is, a circuit is assembled using the terminals of the terminal board 1104. The terminal number 1 is the wiring of the phototransistor 1103, the terminal number 2 is the wiring of the switch 1106, the terminal number 3 is the wiring of the LED 1102, the terminal number 4 is the wiring of the switch 1106 and the battery 1105, and the terminal number 5 is the wiring of the battery 1105. The wirings of the LED 1102 and the phototransistor 1103 are connected to each other.
Resistors 1107 and 1108 are provided so that the output voltage from the phototransistor 1103 is on the order of one digit (V).
[0042]
Then, the sensing element 1110 as described in the first to third embodiments is arranged between the LED 1102 and the phototransistor 1103, and a voltmeter is connected between the terminal number 1 and the terminal number 2 of the terminal board 1104. In this nitrogen dioxide gas detection device, the nitrogen dioxide gas adsorbed on the sensing element 1110 is measured by measuring the voltage.
Thus, according to the sixth embodiment, an accurate nitrogen dioxide gas detection device can be configured in an area of about 12 cm × 6 cm. In addition, since a commercially available battery can be configured as a power source, it becomes possible to detect nitrogen dioxide gas more easily.
[0043]
【The invention's effect】
As described above, in the method for detecting nitrogen dioxide gas of the present invention, first, a diazotization reagent that reacts with nitrite ions to produce a diazo compound and a coupling reagent that couples with a diazo compound to produce an azo dye. A sensing element is prepared in which a mixture of acid and acid is disposed in the pores of a transparent porous body. Next, the light transmittance of the sensing element is measured to obtain the first transmittance. Next, this sensing element is exposed to the gas to be measured for a predetermined time. Next, after that, the light transmittance of the sensing element is measured to obtain the second transmittance. The nitrogen dioxide gas in the gas to be measured is detected from the difference between the first transmittance and the second transmittance.
As a result of this configuration, when the sensing element is exposed to an atmosphere in which nitrogen dioxide gas exists, nitrite ions and diazotizing reagent due to the nitrogen dioxide gas adsorbed in the pores of the sensing element are diazotized to produce a diazo compound, The diazo compound and the coupling reagent are coupled to produce an azo dye. Therefore, since the sensing element is colored and a difference occurs between the first transmittance and the second transmittance, nitrogen dioxide gas can be detected by this.
Therefore, it is only necessary to observe the change in color of the sensing element after the sensing element is exposed to the atmosphere to be measured, so that the nitrogen dioxide gas can be detected more easily and accurately than in the conventional method.
[0044]
Further, the nitrogen dioxide gas sensing element of the present invention comprises a transparent porous body, a diazotization reagent that is disposed in the pores of the porous body and reacts with nitrite ions to generate a diazo compound, and a pore of the porous body A coupling reagent which is disposed together with a diazotizing reagent and couples with a diazo compound to produce an azo dye, and an acid which is disposed with a diazotizing reagent in the pores of the porous body.
As a result of this configuration, when nitrogen dioxide gas enters the nitrogen dioxide gas detection element and adsorbs nitrogen dioxide, the resulting nitrite ions react with the diazotization reagent to produce a diazo compound. And this and a coupling reagent couple | bond together and an azo pigment | dye is produced | generated, Therefore The state which colored the detection element of nitrogen dioxide gas will be in it.
Therefore, since this nitrogen dioxide gas sensing element can detect nitrogen dioxide gas by looking at the color change, the use of this nitrogen dioxide gas sensing element makes it easier and more accurate than conventional methods. Nitrogen gas can be detected.
[0045]
Further, the nitrogen dioxide gas detection device of the present invention includes a light emitting unit that emits light, and an electric signal corresponding to the amount of light received by the light receiving surface, the light receiving surface being disposed opposite the light emitting surface of the light emitting unit. At least a light detection unit that outputs light, a detection element disposed between the light emission unit and the light detection unit, and an electric meter that measures the state of the electrical signal output by the light detection unit. A porous body, a diazotization reagent that is disposed in the pores of the porous body and reacts with nitrite ions to form a diazo compound, and is disposed in the pores of the porous body together with the diazotization reagent to couple with the diazo compound. Thus, a coupling reagent for producing an azo dye and an acid arranged together with a diazotizing reagent in the pores of the porous body are used.
As a result of this configuration, when nitrogen dioxide gas enters the pores of the sensing element and nitrogen dioxide is adsorbed, the resulting nitrite ions react with the diazotization reagent to produce a diazo compound. Since the coupling reagent couples to produce an azo dye, the sensing element is colored. On the other hand, since the light emitted from the light emitting part is incident on the light detecting part via the sensing element, the change in the color of the sensing element is measured by the electric meter as the change in the electrical signal output from the light detecting part. .
Therefore, the nitrogen dioxide gas can be detected with high accuracy by arranging this nitrogen dioxide gas detection device in the atmosphere to be measured. Therefore, the nitrogen dioxide gas can be detected more easily and accurately than the conventional method. It becomes like this.
[Brief description of the drawings]
FIG. 1 shows nitrogen dioxide (NO) in the first embodiment of the present invention.₂ ) It is explanatory drawing explaining the detection method of gas.
2 is a characteristic diagram showing measurement results of absorbance twice in the detection method of Example 1. FIG.
FIG. 3 is an explanatory diagram showing a configuration of a sensing element of Example 1 and an explanatory diagram showing a reaction occurring there.
4 is a correlation diagram showing the relationship between nitrogen dioxide concentration and transmittance in the sensing element of Example 1. FIG.
FIG. 5 is a correlation diagram showing a relationship between a porous body made of glass and optical transmittance.
FIG. 6 is a characteristic diagram showing a detection result in the second embodiment of the present invention.
FIG. 7 is a characteristic diagram showing a detection result in the third embodiment of the present invention.
FIG. 8 is a characteristic diagram showing a detection result in the fourth embodiment of the present invention.
FIG. 9 is a characteristic diagram showing another detection result in the fourth embodiment of the present invention.
FIG. 10 is a configuration diagram showing a schematic configuration of a nitrogen dioxide gas detection device according to a fifth embodiment of the present invention.
FIG. 11 is a configuration diagram showing a schematic configuration of a nitrogen dioxide gas detection device according to a sixth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Detection agent solution, 102 ... Container, 103 ... Porous body, 103a ... Detection element, 104 ... Detection target air, 301 ... Hole, 302 ... Detection element (porous body), 303 ... Thin aqueous solution (detection agent solution) Membrane 304 ... nitrogen dioxide molecule.

Claims (7)

Sensing element comprising a diazotizing reagent that reacts with nitrite ions to form a diazo compound, a coupling reagent that couples with the diazo compound to generate an azo dye, and an acid mixture arranged in the pores of a transparent porous body A first step of preparing
A second step of determining the first transmittance by measuring the light transmittance of the sensing element;
A third step of exposing the sensing element to the gas to be measured for a predetermined time;
After the third step, a fourth step of measuring the light transmittance of the sensing element to obtain the second transmittance ;
With
The average pore diameter of the porous body is larger than the diazotization reagent and the coupling reagent can enter, and is 20 nm or less, and the measurement target is determined by the difference between the first transmittance and the second transmittance. A method for detecting nitrogen dioxide gas, comprising detecting nitrogen dioxide gas in the gas. The method for detecting nitrogen dioxide gas according to claim 1,
The diazotizing reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole, and a compound having a primary amino group or an acetamide group,
The coupling reagent is an aromatic compound such as benzene, naphthalene, or biphenyl, or a heteroaromatic compound such as thiophene or thiazole, and is a compound having a primary to tertiary amino group, an alkoxy group, or a hydroxyl group. A method for detecting nitrogen dioxide gas. A transparent porous body,
A diazotization reagent that is disposed in the pores of the porous body and reacts with nitrite ions to form a diazo compound;
A coupling reagent that is disposed in the pores of the porous body together with the diazotizing reagent and coupled with the diazo compound to form an azo dye;
An acid disposed with the diazotization reagent in the pores of the porous body;
With
The average pore diameter of the porous body with the diazotizing reagent and coupling reagents Hairikomeru size or more, in addition, test knowledge elements of nitrogen dioxide gas, characterized in that at 20nm or less. In the sensing element of nitrogen dioxide gas according to claim 3,
The diazotizing reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole, and a compound having a primary amino group or an acetamide group,
The coupling reagent is an aromatic compound such as benzene, naphthalene, or biphenyl, or a heteroaromatic compound such as thiophene or thiazole, and is a compound having a primary to tertiary amino group, an alkoxy group, or a hydroxyl group. A nitrogen dioxide gas sensing element. A light emitting unit that emits light;
A light detection unit that is arranged with a light receiving surface facing the light emitting surface of the light emitting unit and outputs an electrical signal corresponding to the amount of light received by the light receiving surface;
A sensing element disposed between the light emitting unit and the light detecting unit;
An electric meter for measuring a state of an electric signal output from the light detection unit;
Comprising at least
The sensing element includes a transparent porous body, a diazotization reagent that is disposed in the pores of the porous body and reacts with nitrite ions to generate a diazo compound, and the diazotization reagent in the pores of the porous body A coupling reagent arranged to couple with the diazo compound to produce an azo dye, and an acid disposed with the diazotization reagent in the pores of the porous body,
The average pore diameter of the porous body is larger than the diazotization reagent and the coupling reagent can enter, and in addition, is 20 nm or less,
DETECTION DEVICE nitrogen dioxide gas and detecting the nitrogen dioxide gas in the gas of the measurement target by measuring the transmittance of the light transmitted through the sensing element. In DETECTION DEVICE nitrogen dioxide gas according to claim 5,
The diazotizing reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole, and a compound having a primary amino group or an acetamide group,
The coupling reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole, and a compound having a primary to tertiary amino group, an alkoxy group, or a hydroxyl group. detection apparatus of nitrogen dioxide gas which is characterized. In the detection device of nitrogen dioxide gas according to claim 5 or 6,
The light emitting unit is composed of a light emitting diode,
The photodetection unit is composed of a phototransistor,
in addition,
A battery for supplying power to the light emitting diode and the phototransistor;
A switch for turning on and off the power supply from the battery to the light emitting diode and the phototransistor;
A voltmeter as an electric meter connected between the phototransistor and the battery;
A terminal plate having terminals for connecting the light emitting diode, the phototransistor, the battery, the switch, and the voltmeter;
An apparatus for detecting nitrogen dioxide gas, comprising: the light emitting diode, the phototransistor, the battery, the switch, the voltmeter, and a substrate on which the terminal plate is disposed .

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