JP2008232796A - Formaldehyde detection element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure simply and highly accurately formaldehyde included in the air. <P>SOLUTION: Detection agent solution 101 having the whole quantity of 50 ml acquired by dissolving ammonium acetate 7.5 g, acetic acid 0.15 ml, and acetylacetone 0.1 ml as β-diketone into water, is prepared in a container 102, and a porous body 103 which is a porous glass having an average hole diameter of 4 mm is dipped thereinto for 24 hours. After impregnating the detection agent solution into holes of the porous body 103 in this way, the porous body 103 into which the detection agent is impregnated is air-dried, and left as it is and dried for 24 hours in a nitrogen gas flow, to thereby prepare this detection element (formaldehyde detection element) 103a. The detection agent comprising β-diketone, an ammonium salt, and an acid constituting the ammonium salt is introduced into the detection element 103a, and the detection agent is carried in the porous holes of the detection element 103a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sensing element that detects formaldehyde present in air.

  Formaldehyde is a problem as one of the causative substances for indoor environmental pollution. Formaldehyde is emitted from the building materials and furniture used in newly built houses into the room and is considered to be one of the causes of sick house syndrome for people with chemical sensitivity.

  For this reason, for example, a detection tape (refer to Patent Document 1) or a detection paper (refer to Patent Document 2) that easily measures the concentration of formaldehyde in the air has been proposed in order to trigger indoor ventilation. For example, in the technique of Patent Document 1, a hydrochloride salt of hydroxylamine and a hydrogen ion concentration indicator having a discoloration region in an acidic region are developed on a porous carrier to form a formaldehyde detection tape. According to this detection tape, it is possible to detect several ppm of formaldehyde remaining in the air after disinfection using formaldehyde in a high humidity region where the relative humidity is 80% or more.

  In the technique of Patent Document 2, formaldehyde detection paper is developed by developing a hydrogen ion concentration indicator such as methyl yellow, methyl orange, benzyl orange, and tropeoline and hydroxylamine sulfate on a porous carrier. According to this detection paper, it is possible to detect 0.3 to 4 ppm of formaldehyde in a 30% relative humidity environment.

  There is also a measurement method for detecting 0.04-10 ppm formaldehyde by using a filter wetted with an alkaline aqueous solution of 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (Patent Document). 3). According to this method, 0.04-10 ppm formaldehyde can be detected.

  Further, a base material (adsorbent) containing silica gel is impregnated with a coloring solution containing XD-XA01 (4-amino-4-phenylbut-3-en-2-one) and a buffer solution such as phosphoric acid. There is also a formaldehyde detection material constituted by volatilizing the solvent (see Non-Patent Document 1). According to this detection material, 0.05 to 0.7 ppm of formaldehyde can be detected.

Japanese Patent Application Laid-Open No. 07-055792 Japanese Patent Application Laid-Open No. 07-229889 JP 2003-247899 A Y. Suzuki, et al. "Portable Sick House Syndrome Gas Monitoring System Based on Novel Colorimetric Reagents for the Highly Selective and Sensitive Detection of Formaldehyde", Environ. Sci. Technol., 2003, 37, 5695-5700.

  However, the conventional measurement technique described above has a problem that formaldehyde contained in air (atmosphere) cannot be measured with high accuracy and simply as described below. First, the detection tape of Patent Document 1 has a disadvantage that the measurement conditions are largely restricted because the use environment is limited to high humidity. In addition, the detection paper of Patent Document 2 has a disadvantage that it is impossible to measure the environmental standard value of 0.08 ppm. Further, the method of Patent Document 3 has a disadvantage that a step of wetting the filter with a solution is included immediately before the measurement.

  Further, in the detection material of Non-Patent Document 1, since the base material is opaque, it is necessary to measure reflected light in order to measure the color change of the detection material, and there is a disadvantage that the accuracy is not sufficient. In addition, there is a disadvantage that electric power is required to increase the amount of air passed per unit time using a pump or the like in order to improve accuracy.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to measure formaldehyde contained in air with high accuracy and ease.

  The formaldehyde detection element according to the present invention includes a porous body made of glass, and a detection agent made of β-diketone, ammonium salt, and an acid constituting the ammonium salt disposed in the pores of the porous body. Is. When formaldehyde penetrates into the pores of the formaldehyde detector element, ammonia and β-diketone generated from the ammonium salt placed in the pores react with formaldehyde, producing a reaction product with light absorption characteristics in the visible light range. The

  In the formaldehyde sensing element, the β-diketone is acetylacetone, the ammonium salt is ammonium acetate, and the acid is acetic acid. The β-diketone is benzoylacetone. Β-diketone is dibenzoylmethane. The porous body may have a pore diameter of 20 nm or less.

  As described above, according to the present invention, the detection agent comprising β-diketone, ammonium salt, and acid constituting this ammonium salt is provided (arranged) in the pores of the porous body made of glass. Therefore, it is possible to obtain an excellent effect that formaldehyde contained in the air can be easily measured with high accuracy.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Embodiment 1]
First, the formaldehyde detection element in Embodiment 1 of this invention is demonstrated with the preparation methods of a detection element. First, a method for producing a formaldehyde detection element will be described. As shown in FIG. 1 (a), 7.5 g of ammonium acetate, 0.15 ml of acetic acid, and 0.1 ml of acetylacetone as a β-diketone are dissolved in water to make a total amount. 50 ml of the detection agent solution 101 is prepared in the container 102.

  Next, as shown in FIG. 1 (b), a porous body 103, which is porous glass having an average pore diameter of 4 nm, is immersed in the detection agent solution 101. The porous body 103 is, for example, Vycor # 7930 manufactured by Corning. Vycor # 7930 is a porous body having a plurality of pores with an average pore diameter of 4 nm. The porous body 103 has a chip size of 8 (mm) × 8 (mm) and a thickness of 1 (mm), for example. The porous body 103 preferably has an average pore diameter of 20 nm or less. Although the sensing element 103a is plate-shaped here, it is not limited to this and may be formed in a fiber shape.

In the case where the porous body 103 is made of glass (borosilicate glass), the average pore diameter is set to 20 nm or less, so that in the measurement of the transmission spectrum in the visible UV wavelength region (wavelength 200 to 2000 nm), the visible light region (350 to At 800 nm), light is transmitted. However, it has been found that when the average pore diameter increases beyond 20 nm, a sharp decrease in transmittance is observed in the visible region (Japanese Patent No. 3639123). Thus, the porous body should have an average pore diameter of 20 nm or less. The specific surface area of the porous body 103 in the present embodiment is 100 m ² or more per 1 g. The porous body 103 is not limited to porous glass, and may be made of a transparent (translucent) material that does not react with the detection agent (detection solution) to be supported.

  After the porous body 103 described above is immersed in the detection agent solution 101 for 24 hours and the pores of the porous body 103 are impregnated with the detection agent solution, the porous body 103 impregnated with the detection agent is air-dried, and FIG. As shown, the detector element (formaldehyde detector element) 103a is produced by leaving it in a nitrogen gas stream for 24 hours to dry. Therefore, the detection element 103a is introduced with a detection agent composed of β-diketone, ammonium salt, and an acid constituting the ammonium salt, and the detection agent is supported in the porous pores of the detection element 103a. It becomes. In Example 1, acetylacetone is used as the β-diketone, and ammonium salt and acetic acid are used as the ammonium salt and the acid constituting the ammonium salt.

  According to the thus configured sensing element 103a, when formaldehyde penetrates into the hole, ammonia generated from the ammonium salt disposed in the hole reacts with β-diketone (acetylacetone), and in the visible light range. A reaction product with light absorption properties is produced. As a result, as described below, it is considered that the absorbance of the sensing element changes after measuring formaldehyde.

Next, the formaldehyde detection method using the sensing element 103a will be described. First, the absorbance in the thickness direction of the sensing element 103a is measured. For example, as shown in FIG. 1 (d), the intensity I of the transmitted light that transmits the incident light having the light intensity I ₀ is measured, and the absorbance (= log ₁₀ (I ₀ / I)) is obtained from these.

  Next, as shown in FIG. 1E, for example, the sensing element 103a is exposed to the air 104 to be measured in which formaldehyde having a concentration of 250 ppb is present for 1 hour. This exposure is performed at room temperature (about 20 ° C.). Thereafter, the measured sensing element 103b is taken out from the air 104 to be measured, and the absorbance in the thickness direction of the measured sensing element 103b is measured again as shown in FIG. 1 (f).

  FIG. 2 shows the results of the two absorbance measurements (absorbance analysis) described above. The absorption with a transmitted light measurement wavelength of 350 nm or less is 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 measurement target air is shown by a broken line, and the measurement result of the absorbance after exposure is shown by a solid line. As shown in FIG. 2, there is a large difference between the solid line and the broken line in the wavelength range of 350 to 500 nm with the wavelength of about 407 nm as the center.

  As shown in FIG. 2, in the measurement of the absorbance of the detection element 103b (solid line) after the detection element 103a is exposed to air containing formaldehyde, the absorption around a wavelength of about 407 nm is increased. Therefore, measurement of formaldehyde can be measured and quantified by measuring the change in light absorption in the formaldehyde detector in this embodiment and observing the change in color. For example, the change in light absorption can be detected by measuring the transmittance of light from a purple light emitting diode (center wavelength 405 nm).

  Next, a measurement example using the formaldehyde detection element in this embodiment will be described. For example, the formaldehyde detection element of this embodiment is exposed to sample air produced in a formaldehyde concentration range of 7 to 250 ppb for 1 hour. In this exposure, wind of 0.2 to 0.5 m / s due to the sample air was applied to the sensing element. When the relationship between the difference in transmitted absorbance at a wavelength of 407 nm and the formaldehyde concentration in the sample air before and after the exposure is examined, it is as shown in FIG. 3 and is exposed to the sample air having a high formaldehyde concentration. The more the detection element, the greater the difference in absorbance. Moreover, even if the formaldehyde density | concentration is 7ppb and a very low density | concentration, it is detected, and it turns out that detection of formaldehyde is possible with high sensitivity.

  In addition, the formaldehyde detector of the present embodiment is exposed to each sample air produced at a formaldehyde concentration of 7, 20, and 70 ppb for 1 hour and 2 hours. Even in this exposure, 0.2 to 0.5 m / s of sample air was applied to the sensing element. When the relationship between the difference in transmission absorbance at a wavelength of 407 nm and the formaldehyde concentration in the sample air before and after this exposure was examined, it was as shown in FIG. 4, and in any concentration of sample air, The longer the exposure time, the greater the difference in absorbance.

  As described above, according to the formaldehyde detector in the first embodiment, a porous body that is light-transmissive porous glass is used as a substrate, and acetylacetone, ammonium acetate, and acetic acid are contained in the plurality of holes. Since the detection agent is loaded, it is possible to accurately measure a very small amount of formaldehyde at a ppb level contained in the air. In addition, as described with reference to FIG. 4, the longer the measurement time, the greater the change in absorbance is measured. Therefore, the present sensing element can measure the concentration accumulated over time, and is less than ppb. A trace amount of formaldehyde can also be measured.

  As a measuring apparatus using the formaldehyde detection element in the present embodiment described above, for example, the detection element is disposed between a violet light emitting diode having a center wavelength of emitted light of 405 nm and a photodetector, and transmitted through the detection element. A configuration in which light can be detected by a photodetector, and a change in absorbance of the detection element is output by processing an output signal from the photodetector. With such a simple apparatus configuration, the above-mentioned trace amount of formaldehyde can be easily measured.

[Embodiment 2]
Next, the formaldehyde detection element in Embodiment 2 of this invention is demonstrated with the preparation methods of a detection element. First, a method for manufacturing a formaldehyde detection element will be described. The following description will be made with reference to FIGS. 1A to 1F as in the first embodiment. First, as shown in FIG. 1 (a), 0.157 g of 1-phenyl-1,3-butanedione (benzoylacetone: 1-phenyl-1,3-Butanedione) was dissolved in 50 ml of ethanol, and acetic acid was added to this solution. A detection agent solution 101 is prepared in a container 102 by adding 7.5 g of ammonium, 0.15 ml of acetic acid, and water to a total volume of 60 ml.

  Next, as shown in FIG. 1 (b), a porous body 103, which is porous glass having an average pore diameter of 4 nm, is immersed in the detection agent solution 101. The porous body 103 is, for example, Vycor # 7930 manufactured by Corning. Vycor # 7930 is a porous body having a plurality of pores with an average pore diameter of 4 nm. The porous body 103 has a chip size of 8 (mm) × 8 (mm) and a thickness of 1 (mm), for example. The porous body 103 preferably has an average pore diameter of 20 nm or less.

  After the porous body 103 described above is immersed in the detection agent solution 101 for 24 hours and the pores of the porous body 103 are impregnated with the detection agent solution, the porous body 103 impregnated with the detection agent is air-dried, and FIG. As shown, the detector element (formaldehyde detector element) 103a is produced by leaving it in a nitrogen gas stream for 24 hours to dry. Therefore, the detection element 103a is introduced with a detection agent composed of β-diketone, ammonium salt, and an acid constituting the ammonium salt, and the detection agent is supported in the porous pores of the detection element 103a. It becomes. In the second embodiment, benzoylacetone is used as the β-diketone, and ammonium acetate and acetic acid are used as the ammonium salt and the acid constituting the ammonium salt.

  According to the thus configured sensing element 103a, when formaldehyde enters the hole, ammonia produced from the ammonium salt disposed in the hole reacts with β-diketone (benzoylacetone), and the visible light region. To produce a reaction product having light absorption characteristics. As a result, as described below, it is considered that the absorbance of the sensing element changes after measuring formaldehyde.

Next, the formaldehyde detection method using the sensing element 103a will be described. First, the absorbance in the thickness direction of the sensing element 103a is measured. For example, as shown in FIG. 1 (d), the intensity I of the transmitted light that transmits the incident light having the light intensity I ₀ is measured, and the absorbance (= log ₁₀ (I ₀ / I)) is obtained from these.

  Next, as shown in FIG. 1E, for example, the sensing element 103a is exposed to the air 104 to be measured in which formaldehyde having a concentration of 250 ppb is present for 24 hours. This exposure is performed at room temperature (about 20 ° C.). Thereafter, the measured sensing element 103b is taken out from the air 104 to be measured, and the absorbance in the thickness direction of the measured sensing element 103b is measured again as shown in FIG. 1 (f).

  FIG. 5 shows the results of the two absorbance measurements (absorbance analysis) described above. The absorption with a transmitted light measurement wavelength of 350 nm or less is the absorption of the porous glass (Vycor # 7930) constituting the sensing element itself. In FIG. 5, the measurement result of the absorbance before exposure (exposure) to the air to be measured is shown by a broken line, and the measurement result of the absorbance after exposure is shown by a solid line. As shown in FIG. 5, there is a large difference between the solid line and the broken line in the wavelength range of 350 to 500 nm centering on the wavelength of about 417 nm.

  As shown in FIG. 5, in the measurement of the absorbance of the sensing element 103b after exposure of the sensing element 103a to air containing formaldehyde (solid line), the absorption around the wavelength of 417 nm is increased. Therefore, measurement of formaldehyde can be measured and quantified by measuring the change in light absorption in the formaldehyde detector in Embodiment 2 and observing the change in color. For example, the change in light absorption can be detected by measuring the transmittance of light from a purple light emitting diode (center wavelength 405 nm).

  Next, a measurement example using the formaldehyde detection element in the second embodiment will be described. For example, the formaldehyde detection element of the second embodiment is exposed to sample air prepared in a formaldehyde concentration range of 7 to 150 ppb for 24 hours. This exposure was performed in the absence of wind from the sample air. When the relationship between the difference in transmitted absorbance at a wavelength of 417 nm and the formaldehyde concentration in the sample air before and after this exposure is examined, it is as shown in FIG. 6 and is exposed to the sample air having a high formaldehyde concentration. The more the detection element, the greater the difference in absorbance. Moreover, even if the formaldehyde density | concentration is 7ppb and a very low density | concentration, it is detected, and it turns out that detection of formaldehyde is possible with high sensitivity.

  As described above, according to the formaldehyde detector in the second embodiment, a porous body that is light-transmitting porous glass is used as a substrate, and benzoylacetone, ammonium acetate, and acetic acid are contained in the plurality of holes. Since the detection agent containing it is carried, it is possible to accurately measure a very small amount of formaldehyde at a ppb level contained in the air.

  As a measuring apparatus using the formaldehyde detection element in the second embodiment described above, for example, the detection element is arranged between a purple light-emitting diode having a center wavelength of emitted light of 405 nm and a photodetector. A configuration may be adopted in which the transmitted light can be detected by a photodetector, and the output signal from the photodetector is processed to output a change in absorbance of the detection element. With such a simple apparatus configuration, the above-mentioned trace amount of formaldehyde can be easily measured.

[Embodiment 3]
Next, the formaldehyde detection element in Embodiment 3 of this invention is demonstrated with the preparation methods of a detection element. First, a method for manufacturing a formaldehyde detection element will be described. The following description will be made with reference to FIGS. 1A to 1F as in the first embodiment. First, as shown in FIG. 1 (a), 0.217 g of 1,3-diphenyl-1,3-propanedione (dibenzoylmethane: 1,3-diphenyl-1,3-propanedione) was dissolved in 50 ml of ethanol. Then, 7.5 g of ammonium acetate, 0.15 ml of acetic acid, and water are added to this solution to prepare a detection agent solution 101 with a total volume of 60 ml in the container 102.

  Next, as shown in FIG. 1 (b), a porous body 103, which is porous glass having an average pore diameter of 4 nm, is immersed in the detection agent solution 101. The porous body 103 is, for example, Vycor # 7930 manufactured by Corning, as in the above-described embodiment. The porous body 103 is immersed in the detection agent solution 101 for 24 hours, and the pores of the porous body 103 are impregnated with the detection agent solution, and then the porous body 103 impregnated with the detection agent is air-dried, as shown in FIG. As described above, the sensing element (formaldehyde sensing element) 103a is produced by leaving it in a nitrogen gas stream for 24 hours to dry.

  Therefore, the detection element 103a is introduced with a detection agent comprising β-diketone, an ammonium salt, and an acid constituting the ammonium salt, and the detection agent is supported in the porous pores of the detection element 103a. It becomes. In Embodiment 3, dibenzoylmethane is used as the β-diketone, and ammonium acetate and acetic acid are used as the ammonium salt and the acid constituting the ammonium salt.

  According to the thus configured sensing element 103a, when formaldehyde penetrates into the hole, ammonia produced from the ammonium salt disposed in the hole reacts with β-diketone (dibenzoylmethane) to produce visible light. A reaction product with light absorption properties in the region is produced. As a result, as described below, it is considered that the absorbance of the sensing element changes after measuring formaldehyde.

Next, a method for detecting formaldehyde using the sensing element 103a will be described. First, the absorbance in the thickness direction of the sensing element 103a is measured. For example, as shown in FIG. 1 (d), the intensity I of the transmitted light that transmits the incident light having the light intensity I ₀ is measured, and the absorbance (= log ₁₀ (I ₀ / I)) is obtained from these.

  Next, as shown in FIG. 1E, for example, the sensing element 103a is exposed to the air 104 to be measured in which formaldehyde having a concentration of 150 ppb is present for 24 hours. This exposure is performed at room temperature (about 20 ° C.). Thereafter, the measured sensing element 103b is taken out from the air 104 to be measured, and the absorbance in the thickness direction of the measured sensing element 103b is measured again as shown in FIG. 1 (f).

  FIG. 7 shows the results of the two absorbance measurements (absorbance analysis) described above. The absorption with a transmitted light measurement wavelength of 350 nm or less is the absorption of the porous glass (Vycor # 7930) constituting the sensing element itself. In FIG. 7, the measurement result of the absorbance before exposure (exposure) to the air to be measured is indicated by a broken line, and the measurement result of the absorbance after exposure is indicated by a solid line. As shown in FIG. 7, there is a large difference between the solid line and the broken line in the wavelength range of 350 to 500 nm with a wavelength of about 425 nm as the center.

  As shown in FIG. 7, in the measurement of the absorbance of the sensing element 103b (solid line) after the sensing element 103a is exposed to air containing formaldehyde, the absorption around a wavelength of about 425 nm is increased. Accordingly, measurement of formaldehyde can be measured and quantified by measuring the change in light absorption in the formaldehyde detector in Embodiment 3 and observing the change in color. For example, the change in light absorption can be detected by measuring the transmittance of light from a purple light emitting diode (center wavelength 405 nm).

  Next, a measurement example using the formaldehyde detection element in the third embodiment will be described. For example, the formaldehyde detection element of the third embodiment is exposed to sample air prepared with a formaldehyde concentration of 7 to 150 ppb for 24 hours. This exposure was performed in the absence of wind from the sample air. When the relationship between the difference in transmitted absorbance at a wavelength of 407 nm and the formaldehyde concentration in the sample air before and after this exposure was examined, it was as shown in FIG. 6 and was exposed to the sample air having a high formaldehyde concentration. The more the detection element, the greater the difference in absorbance. Moreover, even if the formaldehyde density | concentration is 7ppb and a very low density | concentration, it is detected, and it turns out that detection of formaldehyde is possible with high sensitivity.

  As described above, according to the formaldehyde detector in the third embodiment, a porous body that is light-transmitting porous glass is used as a substrate, and dibenzoylmethane, ammonium acetate, and acetic acid are contained in the plurality of holes. Since the detection agent containing is carried, it is possible to accurately measure a very small amount of formaldehyde at the ppb level contained in the air.

  As a measuring apparatus using the formaldehyde detection element in the above-described third embodiment, for example, the detection element is arranged between a purple light-emitting diode having a central wavelength of emitted light of 405 nm and a photodetector, and the detection element is arranged. A configuration may be adopted in which the transmitted light can be detected by a photodetector, and an output signal from the photodetector is processed to output a change in absorbance of the detection element. With such a simple apparatus configuration, the above-mentioned trace amount of formaldehyde can be easily measured.

  Next, detection of formaldehyde in the above-described formaldehyde detection element will be described in more detail. First, it is considered that the change in light absorption in the sensing element using acetylacetone according to Embodiment 1 described above is due to the same result as that of the formation reaction of the colored substance in the so-called formaldehyde detection method called the acetylacetone method. In the acetylacetone method, which is known as a formaldehyde detection method, as well known, a reagent (detection agent) similar to that described above is dissolved in a solution (extract) in which formaldehyde is already dissolved, and the temperature is 40 to 60 ° C. The change in absorbance of the solution is measured (JIS, L1041, pp. 4-6). However, the acetylacetone method requires heating and is not sensitive enough.

  On the other hand, according to the formaldehyde detection element in the present embodiment described above, it is not necessary to dissolve the formaldehyde to be measured in the solution, and detection is possible even at a low temperature of about room temperature. According to the detection element in the present embodiment, since the detection agent is carried in the plurality of pores of the porous glass, the reaction described above from the formaldehyde, acetylacetone, and ammonia that have penetrated into the pores. The reaction in which 3,5-diacetyl-1,4-dihydrolutidine is generated as a product is considered to proceed even at room temperature.

  This is the same when the other β-diketones shown in the second and third embodiments are used. For example, 1- (5-acetyl-2,4-diphenyl-3H, 6H-3-azinyl) ethane-1 is obtained as a reaction product from the gaseous formaldehyde that has penetrated into the pores, benzoylacetone, and ammonia. -One (1- (5-acetyl-2,4-diphenyl-3H, 6H, -3-azinyl) ethane-1-one) is produced. In addition, it is considered that this generation reaction proceeds even at room temperature.

  Here, from the above-mentioned β-diketone and ammonia, 3,5-diacetyl-1,4-dihydrolutidine and 1- (5-acetyl-2,4-diphenyl-3H, 6H-3-azinyl) ethane-1 -In the process of producing lutidines (lutidine form) such as ON, an intermediate product is formed from β-diketone and ammonium acetate (ammonia), and this intermediate product is considered to react with formaldehyde. (Refer nonpatent literature 1).

  For example, in the case of benzoylacetone, first, it reacts with ammonium acetate to produce 4-amino-4-phenyl-3-en-2-one (4-amino-4-phenylbut-3-en-2-one) as an intermediate product. ), And this intermediate product reacts with formaldehyde to produce 1- (5-acetyl-2,4-diphenyl-3H, 6H-3-azinyl) ethane-1-one. . In addition, such a reaction via an intermediate product is unlikely to occur at a temperature of about room temperature in the solution or on the surface of silica gel as shown in Non-Patent Document 1. Conceivable. This is because the acetylacetone method requires heating to about 40 ° C., and as shown in Non-Patent Document 1, 4-amino-4-phenyl-3-ene-2- This is thought to be obvious from the synthesis and purification of substances such as ON.

  In contrast, on the glass surface in the plurality of pores of the porous glass described above, ammonium acetate and acetic acid, which are ammonium salts from which ammonia is generated, and β-diketone such as acetylacetone are present at a short distance from each other. However, the sense of distance can be freely moved by thermal energy at room temperature. Due to such a special state, the above-described intermediate product is generated even at room temperature. As a result, it is considered that the above-described reaction product is generated even at room temperature.

  In the above description, acetylacetone, benzoylacetone, and dibenzoylmethane are used as β-diketones, but the present invention is not limited to this, and other β-diketones such as dipyrobaylmethane are used. Is the same. In the above description, ammonium acetate and acetic acid are used as the ammonium salt and the acid constituting the ammonium salt. However, the present invention is not limited to this. For example, it goes without saying that the same applies to ammonium phosphate and phosphoric acid, ammonium sulfate and sulfuric acid, ammonium citrate and citric acid and the like.

  In addition, the change in absorbance in the formaldehyde detection element described above can be easily confirmed visually as a change in color. For example, a color chart in which the light absorption intensity in the vicinity of a wavelength of 400 to 450 nm is changed in five stages is prepared. By comparing with this color chart, the color change in each formaldehyde detector element is increased as the evaluation value increases. Is evaluated on a five-point scale, which indicates that the dark was observed. Sample air with a known formaldehyde concentration is prepared in advance and measured, and the measurement result is evaluated with the above color chart, so that a concentration value of formaldehyde is assigned to each of the five colors of the color chart. Thus, if the color of the formaldehyde detection element after the measurement is visually evaluated using the color chart to which the concentration value is assigned, the concentration of formaldehyde in the measured air can be determined.

It is explanatory drawing for demonstrating the formaldehyde detection element in embodiment of this invention. It is a characteristic view which shows the measurement result of the light absorbency twice before and after making formaldehyde into the measuring object in the measurement using the formaldehyde detection element in Embodiment 1. It is a characteristic view which shows the result of the measurement by exposing the formaldehyde detection element of Embodiment 1 to the sample air produced in the density | concentration range of 7-250ppb of formaldehyde for 1 hour. It is a characteristic view which shows the result of the measurement by exposing a formaldehyde detection element to the sample air produced in the density | concentration range of 7-20 ppb for the formaldehyde density | concentration for 1-2 hours. It is a characteristic view which shows the measurement result of the light absorbency twice before and behind which made formaldehyde into the measurement object in the measurement using the formaldehyde detection element in Embodiment 2. It is a characteristic view which shows the result of the measurement by exposing the formaldehyde detection element of Embodiment 2 to the sample air produced in the density | concentration range of 7-150ppb of formaldehyde for 24 hours. It is a characteristic view which shows the measurement result of the light absorbency twice before and after making formaldehyde into the measuring object in the measurement using the formaldehyde detection element in Embodiment 3. It is a characteristic figure which shows the result of the measurement by exposing the formaldehyde detection element of Embodiment 3 to the sample air produced in the density | concentration range of 7-150ppb of formaldehyde for 24 hours.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Detection agent solution, 102 ... Container, 103 ... Porous body, 103a ... Detection element (formaldehyde detection element), 103b ... Detection element after measurement, 104 ... Air to be measured.

Claims (5)

A porous body made of glass;
A formaldehyde detection element comprising: a β-diketone disposed in a hole of the porous body, an ammonium salt, and a detection agent comprising an acid constituting the ammonium salt. The formaldehyde sensing element according to claim 1,
The β-diketone is acetylacetone;
The ammonium salt is ammonium acetate;
The formaldehyde sensing element, wherein the acid is acetic acid. The formaldehyde sensing element according to claim 1,
The formaldehyde detecting element, wherein the β-diketone is benzoylacetone. The formaldehyde sensing element according to claim 1,
The formaldehyde detecting element, wherein the β-diketone is dibenzoylmethane. In the formaldehyde sensing element according to any one of claims 1 to 4,
The porous body has a pore diameter of 20 nm or less.

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