JPH08261942A - Detecting material, detecting method, and detecting device for acidic gas - Google Patents

Abstract

PURPOSE: To provide a detecting method for an acidic gas adapable to a dry gas with high sensitivity and capable of making continuous measurement by forming a pigment matrix composite film containing fluorescence indicator methyl calcein, and measuring the fluorescence change quantity of an indicator generated when a sample gas is brought into contact with the film. CONSTITUTION: An indicator and a binder polymer are dissolved in a common solvent and mixed as a solution as the means to contain the indicator in a pigment matrix composite film. A polymer (PVP) of vinyl pyrrolidone (VP) and its copolymer are preferably used for the binder polymer. Methyl calcein (MC) having good reactivity with a sample gas and a large change quantity is used for the indicator. An optical wave guide made of quartz fibers 3 and coated with a pigment matrix composite film 2 containing MC in PVP is put in a measuring cell 1. The sample gas is introduced into a gas passage 8 in the cell 1 from a gas inlet 6, measuring light is fed from a light source section 4, and the change of the fluorescence quantity is measured by a light reception section 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detecting material which can be used for detecting acid gas with high sensitivity, a detecting method and a detecting device using the same, and more particularly to a very low concentration hydrogen halide gas and nitrogen. The present invention relates to a detection material containing a fluorescent indicator methylcalcein capable of detecting an acid gas such as an oxide gas or a sulfur compound gas, or a detection method or a detection device using the detection material.

[0002]

2. Description of the Related Art Combustion exhaust gas and exhaust gas from various manufacturing industries contain hydrogen chloride gas, nitrogen oxide (NO ₃ , NO ₂ ) gas, sulfurous acid gas, acid gas such as hydrogen sulfide gas and hydrogen fluoride gas. However, it is necessary to prevent these acidic gas components from being released into the atmosphere. Particularly, from the semiconductor manufacturing process, acidic gas such as hydrogen chloride gas or hydrogen fluoride gas is discharged and treated by various abatement devices. The concentration of these acidic gases is often a low concentration below the ppm level. If it is possible to easily measure the concentration of the raw gas and the processing gas of the abatement device, it will be useful for the operation control of the manufacturing device and the abatement device and the indirect detection of metal corrosion. In addition, in the water treatment, a sterilization treatment with a chlorine-based chemical is performed, and as a side effect, hydrogen chloride gas or the like remains in water or the atmosphere. Since these residual gases are harmful to humans and living organisms, suffocation accidents sometimes occur in water pipe pits and the like. Therefore, it is highly necessary to measure these residual gases as a safety measure.

Conventionally, various means have been proposed to detect harmful gas contained in a gas such as air. Unlike the case of detecting the dissolved component in the liquid, the detection of the gas component in the gas is relatively difficult and the measurement with high accuracy is difficult. Commonly used detection means include (i) gas chromatography, (ii) potentiostatic electrolysis method, (iii) detection tube method, and (iv) detection tape method. Its structure and characteristics are as follows. (I) Gas chromatography Gas chromatography (GC) has good measurement accuracy,
The device is large, it takes a long time to operate, continuous measurement is not possible, and the device is expensive. (Ii) Potential electrolysis method The sensitivity is around ppm. Due to the use of the electrolytic solution for the electrolysis, it takes time and labor to replenish the electrolytic solution. Also,
It is necessary to perform sensitivity correction work due to changes in the electrolyte concentration,
The measurement accuracy is not so good. (iii) Method using a detection tube A detection material in which a substance such as a pH test agent that changes color when reacted with a component to be detected is carried on a carrier made of silica gel or the like is housed in a glass tube. One of the openings is open, and the gas to be detected comes into contact with the detection material. It is disposable and its sensitivity is around ppm. Continuous measurement is not possible. When a detection tube using silica gel as a carrier is used to detect acid gas, the solubility of acid gas in water is extremely high, so even if the concentration of external gas decreases, acid gas does not diffuse from the silica gel to the outside. ,
The color change reaction occurs irreversibly. It is therefore an irreversible sensor and a disposable measurement method. The dry gas cannot be used because the water content in the silica gel evaporates and the solution no longer exists, making measurement impossible. (Iv) Method using a detection tape This detection tape is a tape-shaped carrier carrying a detection substance, and like the above-mentioned detection beads, the reaction is irreversible. Not applicable to gas. In addition, there are disadvantages that the tape consumption is high and the cost is high.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves various drawbacks of conventional measuring methods, provides a detecting means which has high sensitivity, can be applied to dry gas, can be easily measured, and can be continuously measured. Is an issue.

[0005]

The above-mentioned object of the present invention is to prepare a dye matrix composite film containing a fluorescent indicator methylcalcein, and to cause an amount of change in the indicator fluorescence when a test gas is brought into contact with the film. And a high-sensitivity detection material for measuring the concentration of an acidic gas, or a detection method or a detection apparatus using the same.

That is, (1) an acid gas detecting material comprising a dye matrix composite film containing a fluorescent indicator methylcalcein in an organic polymer. (2) The acid gas detection material as described in (1) above, which is provided with a dye matrix composite film in which a fluorescent indicator methylcalcein is contained in a vinylpyrrolidone polymer or copolymer. (3) The film surface of the acid gas detection material according to (1) is exposed to a test gas under light irradiation, and a change in fluorescence intensity generated from the film surface is detected to measure the test gas concentration. A method for detecting acid gas, which is characterized in that (4) In the flow cell provided with the inlet and outlet of the test gas,
An optical path made of a light-transmissive substance containing at least a part of the acid gas detecting material described in (1) is provided, and a light source section and a light receiving section are provided in the optical path, which occurs with a change in the concentration of the test gas. An acid gas detection device characterized by measuring a change in fluorescence intensity of a dye matrix composite film. Is. Further, (5) the acid gas detection device according to (3) above is used to detect the acid gas concentration in the process gas of the exhaust gas purification device, and based on the output, the operating conditions of the exhaust gas treatment process or the exchange of the adsorbent. It becomes possible to provide an acidic gas exclusion method characterized by carrying out an operation.

In the present invention, the indicator is preferably a "fluorescent indicator" which has a characteristic that the reactivity with the test gas is better than the "absorption indicator" and the amount of change is large. Among the “fluorescent indicators”, methylcalcein (hereinafter abbreviated as MC) has particularly excellent characteristics. MC is a compound represented by the following chemical formula (I). Chemical formula (I)

[0008]

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Further, the binder polymer for forming the dye matrix composite film does not have a function of interacting with the indicator to change the amount of fluorescence, and can form a transparent film. If there is no particular limitation. When a strongly acidic polymer such as Nafion or a strongly alkaline polymer such as polyamine is used,
Since it is feared that the response and sensitivity of the sensor will become extremely poor, it is better not to use it. In addition, since the above-mentioned indicator is used by being attached as a film on a carrier as described later, a binder polymer that forms a film with good adhesion to the carrier is preferable.

As a means for incorporating the indicator in the dye matrix composite membrane, the indicator does not necessarily have to be a solution. However, it is preferable to mix the indicator and the binder polymer as a solution in which a common solvent is dissolved. When the indicator is present in the powder state in the dye matrix composite film, light is scattered on the surface of the powder, and the scattered light reduces the measurement accuracy, the reproducibility of the measurement result deteriorates, and the return of the indicator state after the measurement deteriorates. Not preferable. However, it is good when the indicator is not completely dispersed in the molecule but is dispersed in an extremely fine state. In this sense, it may be dispersed and mixed in the binder polymer solution in an extremely finely dispersed state to form a suspension. However, in controlling the concentration of the indicator contained in the film, it is easier to control the mixture of both as a solution. Therefore, as the most preferable binder polymer, when considering the controllability of the concentration of the indicator contained in the composite film, the film-forming property, the adhesion to the carrier, the hygroscopicity of the composite film, etc., the polymerization of vinylpyrrolidone The thing and its copolymer are good. Vinylpyrrolidone (hereinafter abbreviated as VP) is a compound represented by the following chemical formula (II),
The polymer polyvinylpyrrolidone is abbreviated as PVP hereinafter. Chemical formula (II)

[0011]

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The MC is soluble in water or N, N-dimethylformamide. Examples of polymers soluble in water or N, N-dimethylformamide include, for example, polymers of VP and copolymers thereof, polymers of methyl vinyl ether and copolymers thereof; dihydroxy; Copolymers of substituted acrylamides such as ethyl acrylamide and hydroxyethyl acrylamide with acrylic acid esters; vinyl acetate polymers, and partial saponification products of the copolymers; gelatin, modified gelatin, starch, hydroxyethyl cellulose, methyl cellulose, etc. You can list the following. In addition, as described above, when the indicator is dispersed and mixed in an organic polymer solution in an extremely finely dispersed state to form a suspension, and the suspension is formed into a film and dried to form a dye matrix composite film. Hydrophobic organic polymers can also be used.

The optical path referred to in (4) above means a path through which light rays can pass, and does not necessarily require a physical structure such as an optical fiber or a light guide tube, and may be a simple space.
Therefore, the change in fluorescence amount can be measured by transmitted light or reflected light, that is, by any photometric method regardless of the direction of the excitation light and the emission direction of the fluorescence.

[0014]

The operation of the present invention is as follows. This indicator M
C changes the emitted light amount of fluorescence depending on the acidity / basicity of the atmosphere. The acidic gas in the measurement gas is adsorbed and dissolved in the detection material to change the acidity / basicity of the dye matrix composite film, thereby causing a change in the amount of fluorescence emitted by the indicator. The amount of the acidic gas that changes the acidity / basicity of the dye matrix composite film of the detection material is proportional to the concentration of the acidic gas in the measurement gas. Therefore, if an appropriate matrix composition is selected in advance, Sensitive materials with high sensitivity can be created.

A preferred example of the method for producing the dye matrix composite film is as follows. As the indicator, MC was selected from among "fluorescent indicators", which are characterized by better reactivity with the test gas and larger changes than "absorption indicators". Fluorescent indicators having other chemical structures were also examined, but the prescribed sensitivity was not obtained. Calcein is an indicator having a structure similar to that of MC, but it is hardly soluble in a solvent and has poor film-forming properties, and cannot be used as a sensor. The mixing ratio of the indicator and the polymer can be adjusted to the target detection sensitivity. If the test gas is at the ppm level, a molar ratio of MC / polymer (constituent monomer) of about 1/10 to 1/1000 is appropriate.

The liquid containing the MC in the form of a solution or suspension is coated on a suitable carrier, dried and fixed. As the carrier, an optical fiber core, an optical fiber cross section, a white plate (ceramic such as alumina, plastic such as acrylic, etc.), paper and the like are preferable. The drying conditions are
It may be left in the air at room temperature for several hours, but if it is slightly depressurized at about 40 ° C., it will be dried in several minutes, and reproducibility is also good. The fixing method is usually coating and drying as described above, but PVP may be bound to a substrate such as polyethylene or polypropylene by radical polymerization and the like may be impregnated with MC. Also, on PMMA optical fiber or film,
It is also possible to bind PVP by radical polymerization or the like and impregnate MC therein.

The amount of fluorescence discoloration may be measured by the naked eye, but in order to automate it, optical measurement is required. As the light source, white light or monochromatic light may be used as long as it includes light having a wavelength shorter than the fluorescence wavelength (near 510 nm), and a W lamp, a halogen lamp, a laser light, or the like can be used. As the light receiving element, a photodiode, a photomultiplier, a solar cell or the like that can detect a change in the amount of light in the fluorescence wavelength region can be used. As the measurement method, any fluorescence measurement method can be used. FIG. 1 shows an example of a measuring cell used in the measuring method of the present invention which is performed by a transmitted light arrangement method using an optical waveguide, and FIG. 2 shows an example of a detecting device. In the measuring cell shown in FIG. 1, the optical waveguide made of quartz fiber 3 coated with the dye matrix composite film 2 containing MC in PVP is placed in the measuring cell 1, and the gas in the measuring cell 1 is placed. A sample gas (measurement gas) is passed through the passage 8 in a manner of being introduced from the gas inlet 6 and discharged from the gas outlet 7, and the fluorescence wavelength is emitted from the light source unit 4 provided at one end of the optical waveguide while the sample gas is passing. The measuring light including the light of (1) is sent to the optical waveguide, and the change of the fluorescence amount is measured with high sensitivity by the light receiving unit 5 provided at the other end of the optical waveguide. Figure 2
Shows the whole detector. In FIG. 2, 9 is a light source lamp, 10 is a photometric detector, and 11 is a control / analysis personal computer.

Further, FIG. 3 shows another example of the measuring method of the present invention, that is, an example of the detecting device which is performed by the light reflection arrangement method. In FIG. 3, reference numeral 12 is a measuring cell,
The measurement sample coated with the dye matrix composite film 2 containing MC in PVP is placed on the substrate 13 inside, and the sample gas is introduced into the measurement cell 12 from the gas inlet 6 and discharged from the gas outlet 7. While the sample gas is passing, the measuring light including the light of the fluorescence wavelength is projected onto the dye matrix composite film 2 while the sample gas is passing, and the light reflected by the composite film 2 is projected. The light receiving section 14 receives the light, and the photometric detector measures the change in the fluorescence amount. The method of measuring the amount of reflected light is slightly less accurate than the method of measuring the amount of transmitted light.

The sensing material of the present invention can be measured with a dry gas, but its sensitivity increases in the presence of humidity. That is,
When the test gas (nitrogen base, hydrogen chloride gas 5 ppm) was humidified with water vapor and the relative humidity was set to 39%, the transmitted light output was three times that in the case without humidification. The increase in sensitivity is because the polymer matrix itself absorbs water vapor.
Therefore, as a gas detector, it is preferable to provide a hygroscopic means such as a hygroscopic agent column of soda lime or phosphorus pentoxide in the preceding stage of the detector of the present invention for measurement. If a polymer matrix for humidity measurement containing no fluorescent indicator is prepared separately and the outputs of both are measured by simultaneous measurement, the influence of humidity can be offset.

[0020]

EXAMPLES Examples of the acid gas detecting material of the present invention and the acid gas detecting method using the same will be described below.
However, the embodiment of the present invention is not limited to this description. Example 1. (High-sensitivity measurement is possible) The case of detecting about 5 ppm of hydrogen chloride (HCl) as an acidic gas will be described. The method for creating the detection material is as follows. That is, commercially available methylcalcein 1
mg and commercially available PVP 10 mg are dispersed and dissolved in 5 ml of commercially available N, N dimethyl formamide (DMF), and 5 μl of this solution is 1 mm in diameter and 10 in length.
cm of a commercially available quartz fiber was applied to the central part using an injection needle and then dried at room temperature to obtain a sensing element. This sensing element is installed in the measurement cell shown in FIG. 1, white light (tungsten lamp light) is incident from the end of the element by a light guide, and a photodiode with an optical filter (made by Hamamatsu Photonics) is installed at the other end of the element. , Transmitted light (MC fluorescence) was received at a central wavelength of 510 nm. The photodiode was amplified by a self-made amplifier and the amount of received light was quantified. 0-10pp
The measurement results for the gas containing hydrogen chloride gas at a concentration of m are shown in Table 1. It can be seen from Table 1 that the method of the present invention has a linear relationship between the fluorescence amount and the gas concentration, and by using this relationship, it is possible to measure up to 0.5 ppm in this example.

[0021]

[Table 1]

Example 2. Using the same device as in Example 1,
By changing the type of the measurement gas in the same manner, the change (increase) in the amount of fluorescence in the transmitted light depending on the type of gas at a constant gas concentration (acidic gas concentration of 5 ppm) was measured. Table 2 shows the relationship between the type of gas and the change in the amount of fluorescence. From Table 2, it can be seen that the gas concentration of various acidic gases can be measured by the detection method of the present invention.

[0023]

[Table 2]

Example 3. (Interference of coexisting gas components, CO ₂
Others) Using the apparatus of Example 1, 10 pp of nitrogen-based HF gas
Using m as the measurement target, various gas components were made to coexist in addition to the detection component, and the magnitude of interference was examined. The measurement result is the third
It was as in the table. It can be seen from Table 3 that this detection material is not affected by the coexisting gas components.

[0025]

[Table 3]

Example 4. (Measurement with real gas, detector tube, G
(Comparison with C) Gas emitted from semiconductor manufacturing process (HCl 150 p
pm, CO ₂ 1000 ppm, H ₂ 100 ppm, remaining N ₂ ) and gas (HCl 6 ppm, CO ₂ 1000 ppm, H) treated by a detoxifying device (activated carbon adsorption type)
₂ 100 ppm, balance N ₂ ) was measured by the method of the present invention and the conventional method (GC method, detector tube method). The method and apparatus used in the method of the present invention are the same as in the first embodiment. The measurement results are shown in Table 4.

[0027]

[Table 4]

It can be seen that the method of the present invention has a measurement accuracy equivalent to that of GC and has an effect of saving the time and labor required for the measurement. As a result, the processing status of the abatement device can be grasped and the replacement time of the abatement material can be detected, so that the processing will not fail.

[0029]

EFFECTS OF THE INVENTION According to the acid gas detecting material, the detecting method and the detecting device of the present invention, a dye matrix composite film having good adhesiveness and high film strength can be obtained as a film used as the detecting material, and the film can be used in a dry state. Since it can detect acid gas with high sensitivity,
Semiconductor manufacturing equipment It can be used for grasping the situation of exhaust gas, grasping the function of abatement equipment, safety equipment such as laboratories and water facilities, and alarm equipment.

[Brief description of drawings]

FIG. 1 is a side view showing an example of a measuring cell used in a measuring method of the present invention performed by a transmitted light method.

FIG. 2 is a schematic explanatory view showing an example of a detection device of the present invention which uses a transmitted light method.

FIG. 3 is a schematic explanatory view showing an example of a detection device of the present invention which is of a light reflection type.

[Explanation of symbols] 1 measurement cell 2 dye matrix composite film 3 quartz fiber 4 light source section 5 light receiving section 6 gas inlet 7 gas outlet 8 gas passage 9 light source lamp 10 multi-photometric detector 11 personal computer 12 measurement cell 13 substrate 14 light projection Light receiving section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiko Sadaoka 19-11 Dogo, Matsuyama City, Ehime Prefecture

Claims (4)

[Claims] 1. A material for detecting an acidic gas, comprising a dye matrix composite film containing a fluorescent indicator methylcalcein in an organic polymer. 2. The acid gas detection material according to claim 1, further comprising a dye matrix composite film containing a fluorescent indicator methylcalcein in a vinylpyrrolidone polymer or copolymer. 3. A film surface of the acid gas detection material according to claim 1 is exposed to a test gas under light irradiation, and a change in fluorescence intensity generated from the film surface is detected to determine a test gas concentration. A method for detecting acid gas, which comprises measuring. 4. An optical path made of a light-transmitting substance containing at least a part of the acid gas detecting material according to claim 1 is provided in a flow cell provided with an inlet and an outlet for a test gas, and the optical path is provided in the optical path. An apparatus for detecting an acidic gas, comprising a light source section and a light receiving section, and measuring a change in fluorescence intensity of a dye matrix composite film caused by a change in concentration of a test gas.