JP2011247611A - Gas measurement method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of Rayleigh scattering due to the humidity of a measurement environment in the measurement of formaldehyde by a detection element carrying a detecting agent with a transparent porous body as a carrier by a simpler configuration.SOLUTION: A linear-relationship-for-correction setting part 104 obtains a linear relationship for correction corresponding to absorbance for correction measured by an absorbance measurement part 103 from a calibration curve for correction stored in a calibration curve storage part 101. For instance, when an inclination for correction corresponding to the absorbance for correction is acquired from the calibration curve for correction and the section of the axis of the absorbance when the straight line of the acquired inclination passes through the point of the reciprocal of the fourth power of a first wavelength and the absorbance for correction, the linear relationship for correction is obtained. The linear relationship for correction indicates the relationship of a wavelength and absorption by Rayleigh scattering.

Description

  The present invention relates to a gas measuring method and apparatus for measuring formaldehyde as a gaseous air pollutant or indoor environmental pollutant having a high environmental risk.

  Formaldehyde may be contained in newly built houses and furniture, and is a cause of indoor environmental pollution. For people with chemical sensitivity, formaldehyde is considered one of the causes of sick house syndrome.

  For this reason, for example, in order to control indoor ventilation, a simple device that easily measures the concentration of formaldehyde has been proposed. For example, a technique has been proposed in which a filter is wetted with an alkaline aqueous solution of 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole and 0.04-10 ppm of formaldehyde is detected (Non-Patent Document). 1). However, this technique includes a step of wetting the filter with the solution immediately before the measurement, which hinders the convenience of the measurement. Moreover, in the said technique, since the detection sensitivity of formaldehyde is not enough, in order to measure in a short time, a pump is needed, and the enlargement of the apparatus is caused.

  In addition, there is a technique for detecting 0.05-0.7 ppm formaldehyde by developing 4-amino-4-phenyl-3-en-2-one and a buffer solution on a base material containing silica gel (non-patent document). Reference 2). However, in this measurement technique, since the base material is opaque, it is necessary to measure reflected light in order to measure a change in the color of the substrate, and accuracy (detection sensitivity) is not sufficient. In addition, in order to increase the amount of air to be passed per unit time for the purpose of improving accuracy, a pump is necessary, which also increases the size of the apparatus.

  In addition, a simple formaldehyde analysis set (MDS-100) for detecting formaldehyde having a detection limit of 2 ppb using a diffusion scrubber using an alkaline aqueous solution of 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole It is sold by Gastec Co., Ltd. (see Non-Patent Document 3). This device required handling of the solution and a pump for passing air through the diffusion scrubber.

  In view of the situation as described above, the inventors have proposed a method for measuring formaldehyde with high sensitivity without using a pump or the like and without handling an aqueous solution or the like (see Non-Patent Document 4). . In this measurement, formaldehyde detection glass using porous glass is used. However, since this measurement technique performs optical measurement using porous glass, if humidity changes during measurement, Rayleigh scattering occurs due to adsorption and desorption of water in the porous glass, resulting in accurate measurement. There is a problem that a high formaldehyde concentration is not required.

  In order to solve this Rayleigh scattering problem, a technique for correcting the deviation in absorbance due to the occurrence of Rayleigh scattering from the absorbance of each of the three wavelengths transmitted through the detection glass, using light of three different wavelengths, Inventors have proposed (refer patent document 1).

JP 2010-091279 A

K. Kawamura, et al., "Development of a novel hand-held formaldehyde gas sensor for the rapid detection of sick building syndrome", Sensors and Actuators, B 105, pp.495-501, 2005. 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., Vol. 37, No. 24, pp. 5695 -5700, 2003. http://www.gastec.co.jp/whatsnew/new_products.htm Y.Y.Maruo, et al., "Development of formaldehyde sensing element using porous glass impregnated with β-diketone", Talanta, vol.74, pp.1141-1147, 2008.

  However, the above-described technique has a problem that the configuration of the apparatus becomes complicated, such as requiring three wavelengths as a light source and a configuration for processing light of three wavelengths.

  The present invention has been made in order to solve the above-described problems, and has a simpler configuration and a measurement environment in the measurement of formaldehyde by a detection element that supports a detection agent with a transparent porous body as a carrier. The object is to solve the problem of Rayleigh scattering due to humidity.

  The gas measuring method according to the present invention comprises a detection element comprising a transparent porous body in which a detection agent that reacts with formaldehyde to change absorption in the visible region is carried in a hole, at least one of which is Rayleigh scattering in different moisture holding states. The first step of measuring the absorbance in the measurement wavelength range of 500 to 800 nm in two states where the occurrence of the first and second absorbance changes is obtained, the first absorbance change and the second absorbance change, 500 A second step for determining the first slope of the first straight line and the second slope of the second straight line showing the relationship between the inverse of the fourth power of the measured wavelength of .about.800 nm, and a selection from the range of 500 to 800 nm. A calibration curve for correction indicating the relationship between the first absorbance and the first slope of the first absorbance change at the first wavelength and the second absorbance and the second slope of the second absorbance change at the first wavelength is obtained. The initial absorbance of the measurement detection element comprising a transparent porous body in which the detection agent is supported in the pores and not exposed to the atmosphere containing formaldehyde is reacted with formaldehyde. A fourth step of measuring at the second wavelength absorbed by the detection agent, a measurement absorbance measured at the second wavelength of the measurement sensing element exposed to the atmosphere to be measured, and a correction absorbance measured at the first wavelength are obtained. A fifth step, a sixth step for obtaining a correction linear relationship corresponding to the correction absorbance from the correction calibration curve, and a seventh step for obtaining a correction value consisting of absorption due to Rayleigh scattering at the second wavelength from the correction linear relationship; The eighth step of obtaining a corrected measurement absorbance obtained by subtracting the correction value from the measured absorbance and the difference between the corrected measurement absorbance and the initial absorbance are included in the atmosphere to be measured. At least a ninth step for determining the concentration of rumaldehyde, wherein the absorption in the visible region where the detection agent changes upon reaction with formaldehyde is in a range smaller than 500 nm, and the second wavelength is a wavelength in the visible region smaller than 500 nm. It is what I did.

  In the gas measurement method, the detection agent is selected from the group consisting of acetylacetone, 1-phenyl-1,3-butanedione, and 1,3-diphenyl-1,3-propanedione, a β-diketone, ammonium acetate, and acetic acid. As long as it contains.

  Further, the gas measuring device according to the present invention comprises a sensing element comprising a transparent porous body in which pores are loaded with a detecting agent that reacts with formaldehyde to change absorption in the visible region, and at least one of them is in a different moisture holding state. First absorbance change and second absorbance change obtained by measuring absorbance in the measurement wavelength range of 500 to 800 nm in two states where Rayleigh scattering occurs, and the inverse of the fourth power of the measurement wavelength of 500 to 800 nm. The first absorbance of the first absorbance change at the first wavelength selected from the range of 500 to 800 nm is obtained by obtaining the first slope of the first straight line and the second slope of the second straight line showing the relationship between Calibration curve storage unit storing a calibration curve for correction obtained by obtaining the relationship between the second slope of the first absorbance and the second absorbance of the second absorbance change at the first wavelength and the second slope, and detection Agent A measuring detector composed of a transparent porous material carried in the pores, a measured absorbance measured at a second wavelength absorbed by the detecting agent that has reacted with formaldehyde on the measuring detector exposed to the atmosphere to be measured, and An absorbance measuring means for measuring the absorbance for correction measured at the first wavelength and a correction for obtaining a correction linear relationship corresponding to the absorbance for correction measured by the absorbance measuring means from the calibration curve stored in the calibration curve storage unit A straight line relation setting means, a correction value calculating means for obtaining a correction value comprising absorption due to Rayleigh scattering at the second wavelength from the straight line relation for correction obtained by the straight line relation setting means for correction, and a correction value calculating means The corrected measurement absorbance calculation means for obtaining the corrected measurement absorbance obtained by subtracting the correction value from the measured absorbance, and the absorbance measurement means are exposed to the measurement target atmosphere measured at the second wavelength. Concentration calculating means for obtaining the concentration of formaldehyde contained in the atmosphere to be measured by the difference between the initial absorbance of the non-measuring sensing element and the corrected measured absorbance; and a light source that outputs light of the first wavelength and the second wavelength The absorption in the visible region, which changes when the detection agent reacts with formaldehyde, is in a range smaller than 500 nm, and the second wavelength is a wavelength in the visible region smaller than 500 nm.

  In the gas measuring device, the detection agent is a β-diketone selected from acetylacetone, 1-phenyl-1,3-butanedione, and 1,3-diphenyl-1,3-propanedione, ammonium acetate, and acetic acid. As long as it contains.

  As described above, according to the present invention, since the measurement is performed using the calibration curve for correction, the detection of formaldehyde by the detection element supporting the detection agent with a transparent porous body as a carrier with a simpler configuration. In the measurement, an excellent effect is obtained that the problem of Rayleigh scattering due to the humidity of the measurement environment can be solved.

FIG. 1 is a configuration diagram showing a configuration of a gas measuring device according to an embodiment of the present invention. FIG. 2 is a flowchart for explaining a gas measurement method according to the embodiment of the present invention. FIG. 3 is a characteristic diagram showing the results of measuring the absorbance (absorption spectrum) of the sensing element under different humidity changes. FIG. 4 is a characteristic diagram showing a linear relationship obtained by obtaining the inverse relationship between the absorbance and the fourth power of the wavelength from 500 nm to 700 nm from the respective measurement results shown in FIG. FIG. 5 is a graph showing an example of a calibration curve for correction. FIG. 6 is a configuration diagram illustrating a configuration example of a measurement apparatus that measures absorbance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a configuration of a gas measuring device according to an embodiment of the present invention. This gas measurement apparatus includes a calibration curve storage unit 101, a measurement sensing element 102, an absorbance measurement unit 103, a correction linear relationship setting unit 104, a correction value calculation unit 105, a correction measurement absorbance calculation unit 106, a concentration calculation unit 107, and A light source 108 is provided.

  The calibration curve storage unit 101 stores a calibration curve for correction obtained as follows. First, a detection element comprising a transparent porous body in which a detection agent that reacts with formaldehyde to change absorption in the visible region is carried in the pores, at least one of which is subjected to Rayleigh scattering in at least one moisture retention state. The 1st which shows the relationship between the 1st absorbance change and the 2nd absorbance change obtained by measuring the absorbance in the measurement wavelength range of 500 to 800 nm in the state and the inverse of the fourth power of the measurement wavelength of 500 to 800 nm The first slope of the straight line and the second slope of the second straight line are obtained. Next, the relationship between the first absorbance and the first slope of the first absorbance change at the first wavelength selected from the range of 500 to 800 nm, and the second absorbance and the second slope of the second absorbance change at the first wavelength. To obtain a calibration curve for correction.

  The measurement detection element 102 is the same as the detection element used for obtaining the correction calibration curve described above, and is composed of a transparent porous body in which the detection agent described above is carried in the pores. The detection element for measurement 102 is composed of, for example, a porous body made of Vycor (registered trademark) glass manufactured by Corning, and a detection agent disposed inside the pores of the porous body. The porous body is, for example, Vycor # 7930. Vycor # 7930 has a plurality of pores with an average pore diameter of 4 nm. Further, the porous body may have a chip size of 8 (mm) × 8 (mm) and a thickness of 1 (mm), for example. The detection agent includes β-diketone selected from acetylacetone, 1-phenyl-1,3-butanedione, and 1,3-diphenyl-1,3-propanedione, ammonium acetate, and acetic acid. I just need it. Note that the detection agent contains moisture adsorbed in the pores due to the presence of atmospheric humidity.

  The absorbance measurement unit 103 measures the measurement absorbance measured at the second wavelength and the correction absorbance measured at the first wavelength described above for the measurement sensing element 102 exposed to the measurement target atmosphere. The second wavelength is a wavelength absorbed by the detection agent that has reacted with formaldehyde. Here, the absorption in the visible region, which is changed by the detection agent reacting with formaldehyde, is in a range smaller than 500 nm, and the second wavelength described above is a wavelength in the visible region smaller than 500 nm.

  The correction linear relationship setting unit 104 obtains a correction linear relationship corresponding to the correction absorbance measured by the absorbance measurement unit 103 from the calibration curve stored in the calibration curve storage unit 101.

  The correction value calculation unit 105 obtains a correction value made up of absorption by Rayleigh scattering at the second wavelength from the correction linear relationship obtained by the correction linear relationship setting unit 104.

  The corrected measurement absorbance calculation unit 106 obtains a corrected measurement absorbance obtained by subtracting the correction value calculated by the correction value calculation unit 105 from the measurement absorbance.

  The concentration calculation unit 107 is included in the measurement target atmosphere due to the difference between the initial absorbance of the measurement detection element that is not exposed to the measurement target atmosphere measured by the absorbance measurement unit 103 at the second wavelength and the corrected measurement absorbance. Find the concentration of formaldehyde.

  The light source 108 outputs light having at least a first wavelength and a second wavelength.

  Next, the gas measurement method in this Embodiment is demonstrated using the flowchart of FIG.

  First, in step S201, at least one of the detection elements made of a transparent porous body in which the detection agent that reacts with formaldehyde and changes in absorption in the visible region is supported in the pores is subjected to Rayleigh scattering in different moisture holding states. In the two states, the absorbance is measured in the measurement wavelength range of 500 to 800 nm to obtain the first absorbance change and the second absorbance change.

  Next, in step S202, the first slope and the second straight line of the first straight line indicating the relationship between the first and second light absorbance changes and the inverse of the fourth power of the measurement wavelength of 500 to 800 nm. Is obtained.

  Next, in step S203, the first absorbance and the first slope of the first absorbance change at the first wavelength selected from the range of 500 to 800 nm, and the second absorbance and the second absorbance of the second absorbance change at the first wavelength. A calibration curve for correction indicating the relationship with the slope is obtained. The calibration curve obtained in this way is stored in the calibration curve storage unit 101.

  Next, in step S204, the initial absorbance of the measurement detection element 102 made of a transparent porous body in which the detection agent is supported in the pores and not exposed to the atmosphere containing formaldehyde is defined as formaldehyde. Measured at the second wavelength absorbed by the reacted detector. This measurement can be performed using, for example, the gas measurement device described above.

  Next, in step S205, the measurement absorbance measured at the second wavelength and the correction absorbance measured at the first wavelength are obtained for the measurement sensing element 102 exposed to the measurement target atmosphere. For example, the absorbance for correction is obtained by measuring the light of the first wavelength emitted from the light source 108 and transmitted through the measurement detection element 102 with the absorbance measurement unit 103. In addition, measurement light absorbance is obtained by measuring the light of the second wavelength emitted from the light source 108 and transmitted through the measurement sensing element 102 by the absorbance measurement unit 103.

  Next, in step S206, a correction linear relationship corresponding to the correction absorbance is obtained from the correction calibration curve. The correction linear relationship setting unit 104 obtains a correction linear relationship corresponding to the correction absorbance measured by the absorbance measurement unit 103 from the calibration curve stored in the calibration curve storage unit 101. For example, the correction slope corresponding to the correction absorbance is obtained from the correction amount calibration curve, and the absorbance axis when the straight line of the obtained slope passes through the point of the inverse of the fourth power of the first wavelength and the correction absorbance is obtained. If the intercept is obtained, the correction linear relationship is obtained. This linear relationship for correction indicates the relationship between wavelength and absorption due to Rayleigh scattering.

  Next, in step S207, a correction value comprising absorption due to Rayleigh scattering at the second wavelength is obtained from the correction linear relationship. The correction value calculation unit 105 obtains a correction value composed of absorption due to Rayleigh scattering at the second wavelength from the correction linear relationship obtained by the correction linear relationship setting unit 104.

  Next, in step S208, a corrected measured absorbance obtained by subtracting the correction value from the measured absorbance is obtained. The corrected measurement absorbance calculation unit 106 obtains a corrected measurement absorbance obtained by subtracting the correction value calculated by the correction value calculation unit 105 from the measurement absorbance.

  Finally, in step S209, the concentration of formaldehyde contained in the atmosphere to be measured is obtained from the difference between the corrected measured absorbance and the initial absorbance. The concentration calculation unit 107 is included in the measurement target atmosphere due to the difference between the initial absorbance of the measurement sensing element that is not exposed to the measurement target atmosphere measured by the absorbance measurement unit 103 at the second wavelength and the corrected measurement absorbance. Find the concentration of formaldehyde.

  According to this embodiment described above, the light source may have two wavelengths, and the configuration for processing the two wavelengths is sufficient, so that the configuration of the apparatus can be further simplified and the measurement can be performed easily. Become.

  Next, the measurement principle of this embodiment will be described in more detail. The inventors have already found that the influence of Rayleigh scattering in a porous material can be evaluated from a linear relationship established between the absorbance of two wavelengths selected from 500 nm to 700 nm and a quarter of the wavelength. (See Patent Document 1). However, in this case, in addition to the optical measurement for evaluating the influence of Rayleigh scattering, a change in absorbance between 400 and 500 nm due to the reaction between formaldehyde and the detection agent is also measured, which is necessary for the measurement. The wavelength of light becomes as many as three.

  In contrast, as a result of intensive studies by the inventors, it has been found that the slope of the linear relationship described above is expressed as a function of this absorbance when the absorbance at one wavelength selected from 500 nm to 700 nm is measured. It was.

  The relationship between the slope of the linear relationship and the absorbance described above will be described using an example. First, the detection element to be used will be described.

  50 ml of ethanol is added to 0.157 g of 1-phenyl-1,3-butanedione to dissolve, and 7.5 g of ammonium acetate, 0.15 ml of acetic acid and water are added to this solution to form 60 ml of a detection agent solution. A porous glass (Corning Vycor porous glass # 3970) having an average pore diameter of 4 nm is immersed in this detection agent solution, and this is treated for 24 hours, thereby impregnating the detection agent solution into the pores of the porous glass. Next, the porous glass impregnated with the detection agent solution is dried in dry nitrogen for 24 hours to form a detection element.

  When the absorbance (absorption spectrum) of this sensing element is measured, as shown by the curve in FIG. 3A, it has an absorption characteristic having absorption in the ultraviolet region. FIG. 3 is a characteristic diagram showing the results of measuring the absorbance (absorption spectrum) of the sensing element under different humidity changes.

  Next, when the sensing element having the above-described configuration is left in a room with high humidity (80%) in an atmosphere containing formaldehyde for 8 hours and exposed to room air, immediately after measuring the absorption spectrum, ( c) is obtained. Further, when the absorption spectrum is measured after leaving this sensing element in an atmosphere (air) containing no formaldehyde and having a humidity of 45% for 30 minutes to obtain an absorption spectrum, (e) in FIG. 3 is obtained. Further, when the absorption spectrum is measured after the detection element is left to stand for 30 minutes in air containing no formaldehyde and dried at 45% humidity, (f) in FIG. 3 is obtained.

  Furthermore, when this detection element is left to stand in air containing no formaldehyde for 2 minutes and dried for 30 minutes, the absorption spectrum is measured and (d) in FIG. 3 is obtained. Further, when the absorption spectrum is measured after the detection element is left to stand for 30 minutes in air containing no formaldehyde and dried at a humidity of 2%, (b) in FIG. 3 is obtained.

  As shown in (b), (c), (d), (e), and (f) of FIG. 3, absorption having a peak near 410 nm (415 nm) and absorption in which the absorbance gradually decreases from 500 nm to 800 nm. Is measured. These are the results of measuring the absorption spectrum of the sensing element under different humidity changes.

  The absorption from 500 nm to 800 nm of (b), (c), (d), (e), and (f) in FIG. 3 changes the amount of moisture (humidity) in the porous glass constituting the sensing element. This is due to Rayleigh scattering generated. These are the results of measuring the absorbance in the measurement wavelength range of 500 to 800 nm in a state where Rayleigh scattering occurs in different moisture retention states.

Here, when Rayleigh scattering occurs, a linear relationship is established between the absorbance and the inverse of the fourth power of the wavelength. Based on this, when the inverse relationship between the absorbance and the fourth power of the wavelength is obtained from 500 nm to 700 nm from each measurement result within the measured range, (a), (b), (c), (d ), (E), (f), in any measurement result, a linear relationship is established between 1 / (wavelength) ^1/4 and absorbance in the range of 500 to 700 nm. I understand.

  Among the results described above, for example, when the relationship between the absorbance at 525 nm and the slope of each straight line is obtained, it can be seen that a linear relationship is established between the slope of the above straight line and the absorbance as shown in FIG. .

From the above results, if the linear relationship (correction calibration curve) between the slope of the straight line and the absorbance described above is obtained in advance, for example, by measuring the absorbance at 525 nm, the “1/1 / The slope of the “linear relationship between (wavelength) ^1/4 and absorbance” is known. If the slope of the “linear relationship between 1 / (wavelength) ^1/4 and absorbance” is known, the increase in absorbance due to Rayleigh scattering at the absorbance at a wavelength of 414 nm can be calculated.

  For example, the absorbance at a wavelength of 411 nm in the spectra shown by the curves (a), (b), (c), (d), (e), and (f) shown in FIG. As a result, absorption of the detection agent and absorption due to Rayleigh scattering are included. Therefore, as described above, the formaldehyde concentration in the measurement indicated by each curve can be calculated by subtracting the increase in Rayleigh scattering obtained from the measurement result of the absorbance at 525 nm and the calibration curve for correction shown in FIG.

  Incidentally, the measurement of absorbance may be performed by using, for example, a measuring apparatus illustrated in FIG. This measuring apparatus first has a light emitting diode 602 with a wavelength of 415 nm, a light emitting diode 603 with a wavelength of 525 nm, a first light sensor 604, a detection element 605, a half mirror 606, a second light sensor 607, and a processing on a surface plate 601. A partial housing 608 is provided.

  The light emitting diode 602 and the light emitting diode 603 are supported and fixed on the surface plate 601 by the light source support portion 611. The first optical sensor 604 is supported and fixed on the surface plate 601 by the sensor support unit 612. The sensor support unit 612 is connected to the processing unit housing 608 via the connection unit 609. The second optical sensor 607 is fixed to the sensor holding unit 613, and the sensor holding unit 613 is fixed to the distal end portion of the support beam 614 fixed to the processing unit housing 608. The second optical sensor 607 is disposed inside the support beam 614 and connected to the processing unit casing 608 via a connection unit (not shown).

  The second optical sensor 607 is disposed at a position where the light from the light emitting diode 602 and the light emitting diode 603 reaches through the half mirror 606. The second photosensor 607 is provided at a location where the light from the light emitting diode 602 and the light emitting diode 603 is reflected by the half mirror 606. The detection element 605 is disposed between the half mirror 606 and the first optical sensor 604.

  In this measuring apparatus, light from the light emitting diode 602 and the light emitting diode 603 first enters the half mirror 606, a part of which is transmitted and reaches the first optical sensor 604, and the other part is reflected. It reaches the second optical sensor 607. Here, the sensitivity of each sensor is adjusted so that the light intensities received by both the first optical sensor 604 and the second optical sensor 607 match without arranging the detection element 605. When the sensing element 605 is arranged in such a state and the intensity of the light source light is measured by each sensor, the light intensity detected by the second light sensor 607 and the light intensity detected by the first light sensor 604 are measured. Thus, the absorbance of the sensing element 605 can be measured.

  Further, if the light intensity measurement described above is performed with only the light emitting diode 602 turned on, the absorbance at a wavelength of 415 nm can be measured. Further, if the light intensity measurement described above is performed with only the light emitting diode 603 turned on, the absorbance at a wavelength of 525 nm can be measured.

  Further, the above-described calibration curve storage unit 101, correction linear relationship setting unit 104, correction value calculation unit 105, correction measurement absorbance calculation unit 106, and concentration calculation unit 107 are accommodated in the processing unit housing 608.

  A measurement example using the above-described measuring apparatus will be described. First, the following detection agent is manufactured, and the detection element 605 is manufactured using this detection agent. 50 ml of ethanol is added to 0.157 g of 1-phenyl-1,3-butanedione to dissolve, and 7.5 g of ammonium acetate, 0.15 ml of acetic acid and water are added to this solution to make 60 ml to form a detection agent solution. Porous glass (Corning Vycor porous glass # 3970) having a pore diameter of 4 nm is immersed in this detection agent solution, and this is treated for 24 hours, thereby impregnating the detection agent solution into the pores of the porous glass. Next, the porous glass impregnated with the detection agent solution is dried in dry nitrogen for 24 hours to form a detection element 605.

  The above-described sensing element 605 is set in the measuring apparatus shown in FIG. 6, and first, the absorbance (initial absorbance) when the light-emitting diode 602 is turned on is measured before exposure to the measurement target environment. Next, after the measurement apparatus is left in the room to be measured for 8 hours, the absorbance when the light emitting diode 602 is turned on (measured absorbance) and the absorbance when the light emitting diode 603 is turned on (correction absorbance) are measured. Note that using the detection element having the same configuration as the detection element 605, the calibration curve for correction has been prepared in advance by the description in steps S201 to S203 in the flowchart of FIG. It is stored in the storage unit (calibration curve storage unit 101).

  In the above-described measurement, the formaldehyde concentration is calculated as 125 ppb (1 hour average) only from the measurement result of the absorbance when the light emitting diode 602 is turned on. This is a result obtained by subtracting the initial absorbance from the measured absorbance.

  On the other hand, a correction value consisting of absorption at a wavelength of 415 nm due to Rayleigh scattering is obtained from the correction absorbance and the stored calibration curve, and the concentration of formaldehyde is calculated using the corrected absorbance obtained by subtracting the obtained correction value from the measured absorbance. Then, it becomes 95 ppb (1 hour average), and the result which excluded the influence of Rayleigh scattering is obtained.

  As described above, according to the present invention, in the measurement, when two wavelengths are used as the light source, a detection element that carries a detection agent using a transparent porous body as a carrier in a state in which the influence of Rayleigh scattering is eliminated. This makes it possible to measure formaldehyde.

  The present invention is not limited to the embodiments described above, and many combinations and modifications can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the production of a calibration curve for correction, after exposing multiple sensing elements to different humidity environments, each is measured in a lower humidity environment, so that at least one of the different moisture retention states causes Rayleigh scattering. In the two states, the absorbance may be measured in the measurement wavelength range of 500 to 800 nm to obtain the first absorbance change and the second absorbance change.

  In the preparation of the calibration curve for correction described above, the first absorbance change and the second absorbance change may be obtained in the range of 500 to 700 nm, and the first wavelength may be selected from the range of 500 to 700 nm. In the range of 700 to 800 nm, the influence due to Rayleigh scattering is not significant, so that a decrease in accuracy can be suppressed by using the first wavelength selected from the range of 500 to 700 nm.

  DESCRIPTION OF SYMBOLS 101 ... Calibration curve memory | storage part, 102 ... Detection element for measurement, 103 ... Absorbance measurement part, 104 ... Correction linear relationship setting part, 105 ... Correction value calculation part, 106 ... Correction measurement absorbance calculation part, 107 ... Concentration calculation part, 108: Light source.

Claims (4)

A detection element composed of a transparent porous body in which a detection agent that changes absorption in the visible region by reacting with formaldehyde is supported in the pores is in two states in which Rayleigh scattering occurs in at least one of the different moisture retention states. A first step of measuring absorbance in a measurement wavelength range of 500 to 800 nm to obtain a first absorbance change and a second absorbance change;
The first slope of the first straight line and the second slope of the second straight line showing the relationship between the first absorbance change and the second absorbance change, and the inverse of the fourth power of the measurement wavelength of 500 to 800 nm. A second step for determining
The first absorbance and the first slope of the first absorbance change at the first wavelength selected from the range of 500 to 800 nm, and the second absorbance and the second slope of the second absorbance change at the first wavelength, A third step for obtaining a calibration curve for correction indicating the relationship of
The detection agent for measurement comprising the transparent porous body, in which the detection agent is supported in the pores, has an initial absorbance in an initial state that is not exposed to an atmosphere containing formaldehyde, and the detection agent that has reacted with formaldehyde A fourth step of measuring at the second wavelength to absorb;
A fifth step of obtaining a measurement absorbance measured at the second wavelength of the measurement sensing element exposed to the atmosphere to be measured, and a correction absorbance measured at the first wavelength;
A sixth step of obtaining a correction linear relationship corresponding to the correction absorbance from the correction calibration curve;
A seventh step of obtaining a correction value consisting of absorption by Rayleigh scattering at the second wavelength from the correction linear relationship;
An eighth step of obtaining a corrected measured absorbance obtained by subtracting the correction value from the measured absorbance;
And at least a ninth step of determining the concentration of formaldehyde contained in the atmosphere of the measurement object from the difference between the corrected measurement absorbance and the initial absorbance,
Absorption in the visible region where the detection agent reacts with formaldehyde changes in a range smaller than 500 nm, and the second wavelength is a wavelength in the visible region smaller than 500 nm. The gas measurement method according to claim 1,
The detection agent includes a β-diketone selected from acetylacetone, 1-phenyl-1,3-butanedione, and 1,3-diphenyl-1,3-propanedione, ammonium acetate, and acetic acid. Characteristic gas measurement method. A detection element composed of a transparent porous body in which a detection agent that changes absorption in the visible region by reacting with formaldehyde is supported in the pores is in two states in which Rayleigh scattering occurs in at least one of the different moisture retention states. A first absorbance change and a second absorbance change obtained by measuring absorbance in a measurement wavelength range of 500 to 800 nm,
The reciprocal of the fourth power of the measurement wavelength of 500 to 800 nm;
Determining a first slope of a first straight line and a second slope of a second straight line that indicate the relationship between
The first absorbance and the first slope of the first absorbance change at the first wavelength selected from the range of 500 to 800 nm, and the second absorbance and the second slope of the second absorbance change at the first wavelength, A calibration curve storage unit in which a calibration curve for correction obtained by obtaining the relationship is stored;
A sensing element for measurement comprising the transparent porous body with the sensing agent carried in the pores;
Absorbance measuring means for measuring the measurement absorbance measured at the second wavelength absorbed by the detection agent reacted with formaldehyde on the measurement sensing element exposed to the atmosphere to be measured, and the correction absorbance measured at the first wavelength When,
A correction linear relationship setting means for obtaining a correction linear relationship corresponding to the correction absorbance measured by the absorbance measurement means from the correction calibration curve stored in the calibration curve storage unit;
Correction value calculating means for obtaining a correction value consisting of absorption by Rayleigh scattering at the second wavelength from the correction linear relation obtained by the correction linear relation setting means;
Corrected measurement absorbance calculation means for obtaining a corrected measurement absorbance obtained by subtracting the correction value calculated by the correction value calculation means from the measured absorbance;
The absorbance measurement means is included in the measurement target atmosphere due to the difference between the initial absorbance of the measurement sensing element not exposed to the measurement target atmosphere measured at the second wavelength and the corrected measurement absorbance. A concentration calculating means for determining the concentration of formaldehyde;
A light source that outputs light of the first wavelength and the second wavelength,
The gas measuring apparatus according to claim 1, wherein absorption in the visible region that changes when the detection agent reacts with formaldehyde is in a range smaller than 500 nm, and the second wavelength is a wavelength in the visible region smaller than 500 nm. In the gas measuring device according to claim 3,
The detection agent includes a β-diketone selected from acetylacetone, 1-phenyl-1,3-butanedione, and 1,3-diphenyl-1,3-propanedione, ammonium acetate, and acetic acid. Characteristic gas measuring device.

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