JP5779038B2 - Volatile organic matter detector and volatile organic matter detection method - Google Patents

Description

  The present invention relates to a volatile organic substance detector and a volatile organic substance detection method for detecting a volatile organic substance contained in an object to be measured, in particular, by ionizing the volatile organic substance and determining the size of the diffusion constant. The present invention relates to a volatile organic substance detector and a volatile organic substance detection method capable of specifying the type of volatile organic substance contained in an object.

  Conventionally, in order to measure the concentration of a volatile organic substance or the like contained in a measurement object, a volatile organic substance detector such as a Photo Ionization Detector (hereinafter referred to as PID) has been used. The principle of measurement of this PID is to induce volatile organic matter to be measured in an apparatus in which a pair of application electrodes are arranged, and to irradiate short wavelength UV to ionize the volatile organic matter, etc. The detection current having a correlation with the concentration is measured by capturing with the application electrode, and the concentration of the volatile organic substance or the like is measured by converting the current value into the concentration.

  As shown in FIG. 9 as an example, the PID 50 applies a voltage to the detection chamber 52 into which volatile organic substances or the like are introduced and discharged, a pair of electrodes 54 provided in the detection chamber 52, and the electrode 54. Applying circuit 56, UV lamp unit 58 for irradiating the measurement fluid (FL) in detection chamber 54 with UV, measurement circuit 60 for measuring the current flowing through electrode 54, and further, from the current value, volatile organic substances, etc. The computer 62 includes a calculation device 62 that performs a calculation for conversion into a concentration.

  In this conventional PID, a single-component volatile organic substance or the like is introduced into the detection chamber 52 and discharged from the detection chamber 52 after UV irradiation by the UV lamp unit 58. The introduced volatile organic matter or the like is ionized by UV irradiated from the UV lamp unit 58 provided on the side wall portion of the detection chamber 52, and a voltage provided in the detection chamber 52 is applied to the ions or electrons. By being attracted to and captured by the electrode 54, a current is generated in the circuit.

  Then, this current is measured by the measurement circuit 60, and further, the calculation device 62 multiplies the current value by a coefficient for each substance (a substance such as a volatile organic substance to be measured), thereby obtaining a volatile organic substance or the like. Is output. Since such PID is sensitive to many volatile organic substances as in the other detectors and detection methods described above, it is an effective means for measuring volatile organic substances, and the apparatus itself is also large. Therefore, it is possible to easily measure volatile organic substances and the like, which is very useful.

However, the conventional PID needs to input the name of the substance such as the volatile organic substance to be measured before measuring the concentration of the volatile organic substance, as in the case of the simple measurement method such as the semiconductor sensor and the catalytic combustion type sensor. was there. Therefore, for example, Patent Document 1 discloses a photoionization detection method in which sample components are detected by irradiating a sample to be detected with UV generated by gas discharge and measuring an ionization current of the sample to be detected. A photoionization detection method is disclosed, wherein the discharge gas is selected from He, Ne, Ar, Xe or H ₂ and the UV energy is changed to provide selectivity to the detection component. According to this technique, the detection component can be made selective from the ionization potential of the fluid to be measured by changing the wavelength of UV irradiated to the fluid to be measured.

  Another photoionization detector has a configuration as described in Patent Document 2, for example. That is, as shown as an example in FIG. 10, the gas in the LA lamp 70 is excited at high frequency by the excitation electrode 72, and the generated vacuum ultraviolet ray UV is irradiated to the measurement target gas, thereby ionizing volatile organic substances in the air. Then, the ion current is detected by the detection electrode 74 and the concentration of the gas is calculated.

  Furthermore, a technique for identifying the type of the substance to be measured from the diffusion constant of the substance to be measured is also known. For example, volatile organic substances are often liquids under standard conditions. First, place the volatile organic substances (liquid) in a small container (diffusion tube) with a long neck and place it in a container of constant temperature and pressure. The diffusion rate and the diffusion constant are obtained by diluting the diffusing component with a diluting gas and measuring the change in weight for each time after a sufficiently long time under certain generation conditions. The diffusion rate varies depending on the length, thickness, and temperature of the neck of the diffusion tube.

  For example, Patent Document 3 discloses a technique for calculating a gas diffusion coefficient from the induction period of gas that has permeated from one side of the film-like polymer material to the other side. In addition, there is also a technique of obtaining the mass of volatile organic substances or the like by so-called TOFMS (time-of-flight mass spectrometry).

Japanese Patent Laid-Open No. 10-307123 JP 2002-148240 A JP 2001-272390 A

  However, the configuration of the technique disclosed in Patent Document 1 has a complicated configuration and a large apparatus because the irradiation wavelength is changed by using a plurality of UV emission gases. Moreover, the data obtained are values of ion currents due to wavelengths unique to some UV lamps, and the substance cannot be specified only from the values.

  Further, in the technique disclosed in Patent Document 2, it is possible to measure the concentration of volatile organic matter from the detected current, but since the diffusion constant cannot be calculated, the type of volatile organic matter to be measured, etc. The problem that cannot be identified has arisen.

  Furthermore, it is useful to use a conventional technique for obtaining a diffusion constant capable of specifying the type of a volatile organic substance or the like to be measured. However, the technique is complicated and inconvenient and disclosed in Patent Document 3. Similar to technology, it is considered difficult to obtain a diffusion constant in real time at a site such as a factory where components contained in the air are problematic. Moreover, although the measurement by the TOFMS is a very useful measurement method, the apparatus becomes large, and since it must be measured in a vacuum, continuous measurement is impossible, and It has been pointed out that it is not suitable for on-site measurement because of the high cost of equipment installation.

  The problem to be solved by the present invention is to cope with the above-mentioned problem, and the size of the diffusion constant, which is an important property of the volatile organic substance, together with the concentration of the volatile organic substance with a simple configuration and a small apparatus. Is to provide a volatile organic substance detector and a volatile organic substance detection method. In addition, since the type of volatile organic matter can be specified from the size of the diffusion constant, the sensitivity of the volatile organic matter detector can be corrected based on the type of volatile organic matter, and the volatile organic matter detection It is to provide a method.

In order to solve the above-described problems, the present invention takes the following technical means.
That is, the invention according to claim 1 is an ionization energy supply means for supplying ionization energy to the volatile organic matter in order to ionize the volatile organic matter, and at least one pair of ions for detecting the ionized ions. A voltage applying means capable of reversing a voltage polarity for applying a predetermined voltage to the ion detecting electrode; a current measuring means for measuring a current value flowing through the ion detecting electrode; and a voltage applied by the voltage applying means. A diffusion constant calculating means for calculating a diffusion constant of the volatile organic substance from a current ratio based on a current value before and after the voltage polarity reversal measured by the current measuring means when the polarity is reversed, and the ionization energy The supply means supplies the ionization energy between the ion detection electrodes and in a range biased to one of the ion detection electrodes. By provided earthenware pots, between the ion detection electrode, the ionization energy is volatile organics detector, wherein a resulting range not supplied.

  The invention described in claim 2 is the volatile organic substance detector according to claim 1, wherein the ionization energy supply means is a UV irradiation means for irradiating the volatile organic substance with UV, and the volatile organic substance. One of an ionizing radiation emitting unit that emits ionizing radiation and a corona discharge unit that causes corona discharge to the volatile organic substance is provided.

  Furthermore, the invention described in claim 3 is the volatile organic substance detector according to claim 1 or 2, wherein the information display means displays information relating to the volatile organic substance based on the diffusion constant calculated by the diffusion constant calculation means. Concentration calculating means for calculating the concentration of the volatile organic substance based on information on the volatile organic substance based on the diffusion constant calculated by the diffusion constant calculating means and the current value measured by the current measuring means; When the information on the volatile organic substance can be corrected and the information on the volatile organic substance is corrected, information on the volatile organic substance based on the diffusion constant approximated within a predetermined range is listed and displayed on the information display means. In addition, the information on the volatile organic matter is selected from the listed and displayed information, and the concentration calculating means And information regarding the selected volatile organics from the current value of the current measurement means is measured, it is characterized by having an information modifying means for calculating the concentration of the volatile organic again.

According to a fourth aspect of the present invention, the ionization energy is supplied to the volatile organic material to ionize the volatile organic material, and at least one of the ions ionized by the ionization step is applied with a predetermined voltage. An ion detection step of detecting with a pair of ion detection electrodes; a current value measurement step of measuring a current value flowing through the ion detection electrode; and reversing the polarity of the voltage applied to the ion detection electrode. And obtaining a current ratio from a current value flowing through the ion detection electrode before and after the inversion, and calculating a diffusion constant of the volatile organic substance from the current ratio, and the ionization step includes the step of By supplying the ionization energy between the ion detection electrodes and within a range biased to one of the ion detection electrodes, Between the electrodes for detection, with causes range the ionization energy is not supplied, a volatile organic detection method and supplying the ionizing energy to said volatile organics.

  And invention of Claim 5 is a volatile organic substance detection method of Claim 4, Comprising: The information display process which displays the information regarding the volatile organic substance based on the diffusion constant calculated in the said diffusion constant calculation process, The concentration calculation step for calculating the concentration of the volatile organic matter from the information on the volatile organic matter based on the calculated diffusion constant and the current value measured by the current value measurement step, and the volatile property displayed by the information display step A correction reception step for receiving correction of information on organic matter, and when the information on volatile organic matter is corrected by the correction reception step, information on the volatile organic matter after correction and the current value measured by the current value measurement step And an information correction step of calculating the concentration of the volatile organic substance again.

  According to the volatile organic substance detector and the volatile organic substance detection method according to the present invention, the size of the diffusion constant effective for specifying the type of the volatile organic substance is obtained based on the value of the current flowing through the detection electrode that detects ions. Can do. It is also possible to estimate volatile organic substances from the diffusion constant. Furthermore, since it is possible to obtain not only the concentration of volatile organic substances but also the diffusion constant, for example, it is easy to obtain information on ventilation guidelines for factories and the like. Furthermore, since the volatile organic substance detector itself does not require a complicated configuration, it can be used as a simple and small-sized one.

It is the schematic diagram which showed an example of the structure of the detector in 1st Embodiment of the volatile organic substance detector which concerns on this invention. It is an example figure which showed the detection process in 1st Embodiment of the volatile organic substance detection method which concerns on this invention. It is a schematic diagram which shows the arrangement | positioning of an electrode, the UV irradiation position, and the application condition of a voltage for demonstrating the theory of the diffusion constant calculation of the volatile organic substance in 1st Embodiment of the volatile organic substance detection method which concerns on this invention. It is the graph which showed the experimental result of the relationship between the applied voltage and ion current at the time of detecting toluene (20 ppm) which is volatile organic substance in 1st Embodiment of the volatile organic substance detector which concerns on this invention. The experimental result of the relationship between the concentration of volatile organic matter (toluene) at each applied voltage and the ionic current when toluene, which is a volatile organic matter, is detected in the first embodiment of the volatile organic matter detector according to the present invention. It is the shown graph. It is the graph which showed the experimental result of the relationship between positive / negative ion current ratio and a diffusion constant at the time of detecting volatile organic substance (20 ppm) in 1st Embodiment of the volatile organic substance detector which concerns on this invention. It is the schematic diagram which showed an example of the structure of the detector in 2nd Embodiment of the volatile organic substance detector which concerns on this invention. It is an example figure which showed the detection process in 2nd Embodiment of the volatile organic substance detection method which concerns on this invention. It is the schematic diagram which showed an example of the structure of the conventional PID. It is the schematic diagram which showed an example of the structure of the conventional photoionization detector.

Hereinafter, a first embodiment of a volatile organic substance detector and a volatile organic substance detection method according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of the configuration of the detector in the first embodiment of the volatile organic substance detector according to the present invention, and FIG. 2 is a first diagram of the volatile bill detector detecting method according to the present invention. It is an example figure which showed the detection process in embodiment. Further, 10 is a volatile organic substance detector, 12 is an ion detection chamber, 14 is a UV lamp, 16 is a UV lamp light emitting unit, 18 UV lamp excitation circuit, 20 is an ion detection electrode, 22 is a voltage applying means, and 24 is a current value measurement. Means 26 denotes a diffusion constant calculating means.

  First, as shown in FIG. 1, the volatile organic substance detector 10 has an ion detection chamber 12 into which a volatile organic substance to be measured flows, and the ion detection chamber 12 has a volatile organic substance on its inner wall. A UV lamp light-emitting unit 16 of a UV lamp 14 (ionization energy supply means) that supplies ionization energy to is connected. The UV lamp 14 is connected to a UV lamp excitation circuit 18 that excites the UV lamp. In the figure, the volatile organic substance to be measured flows from the left to the right in the ion detection chamber 12 in the representation of the figure, but actually flows from the back side to the near side in the figure. It is configured to let you.

  In the ion detection chamber 12, a pair of ion detection electrodes 20 for capturing ions of volatile organic substances ionized by ionization energy are provided. As the ion detection electrode 20, a SUS (stainless steel) electrode, a gold electrode, a platinum electrode, a copper electrode, or the like can be used. However, since copper has a good reactivity, the electrode surface is likely to be deteriorated. It is preferable to use a gold electrode or a platinum electrode.

  In the present embodiment, as shown in FIG. 1, the UV lamp 14 and the UV lamp light emitting unit 16 supply ionization energy between the electrodes of the ion detection electrode 20 and in a range biased to one ion detection electrode 20. By being provided at the position, a range in which no ionization energy is supplied between the electrodes of the ion detection electrode 20 is generated. In the experiment described later, the ion detection electrode 20 in the ion detection chamber 12 has a vertical length of 16 mm, a horizontal length of 6 mm, a thickness of 1 mm, and a distance between the electrodes of 8.5 mm. The volatile organic substance detector 10 is used.

  Furthermore, since the UV lamp light-emitting part 16 of the UV lamp 14 (manufactured by Heraeus Co., Ltd., PKR106, outer diameter 12.6 mm, 10.6 eV) has a circular shape, the shape of the UV lamp light-emitting part 16 is in the electrode direction. A light-shielding cover (manufactured by GL Sciences Inc.) is attached so that it is a rectangle of 3 mm and a direction perpendicular to it (direction in which volatile organic substances flow in) 8 mm, and the range in which no ionization energy is supplied is about 5.5 mm in the electrode direction It is supposed to be. Note that a volatile organic substance detector 10 configured such that the distance between the electrodes is 8.5 mm or more and the range in which ionization energy is not supplied is 5.5 mm or more in the electrode direction may be used (between the electrodes). When the distance is increased, it is preferable to increase the range in which ionization energy is not supplied).

  Subsequently, voltage application means 22 that can apply a predetermined voltage to the ion detection electrode 20 is connected to the ion detection electrode 20, and similarly, a current value measurement means 24 is also connected. The voltage application means 22 is configured to measure the value of the current flowing through the ion detection electrode 20 when a voltage is applied.

  The voltage application means 22 is configured to be able to reverse the voltage polarity, and based on the current ratio of the current value flowing through the ion detection electrode 20 measured by the current measurement means 24 before and after the voltage polarity inversion, A diffusion constant calculating means 26 capable of calculating the diffusion constant of the volatile organic substance is connected to the current value measuring means 24. The type of the volatile organic substance specified by the calculated diffusion constant is displayed by display means (not shown) connected to the diffusion constant calculation means 26.

  In addition, the concentration of the volatile organic substance to be measured can also be calculated based on the value of the current flowing through the ion detection electrode 20 measured by the current value measuring unit 24. As the calculation method, for example, in the case of toluene, data shown as an example in FIGS. 4 and 5 obtained in advance by experiments is accumulated in a storage device (not shown), and calculation is performed using the data. Is.

  Furthermore, for example, when a gas to be measured contains a plurality of types of volatile organic substances, the calculated diffusion constant is calculated as an average value of the plurality of types of volatile organic substances. If an average value is displayed, it will be useful as a guideline for ventilation. Moreover, you may display with the density | concentration of the calculated volatile organic substance.

  In this embodiment, the ionization energy is supplied to the volatile organic substance by a UV lamp. However, this may be configured to irradiate the volatile organic substance with ionizing radiation, or corona is applied to the volatile organic substance. It is good also as a structure which causes discharge.

  Next, the flow of the volatile organic substance detection method in the present embodiment will be described. As shown in FIG. 2, first, UV is irradiated from a UV lamp (ionization energy supply) to the volatile organic substance to be measured that has flowed into the ion detection chamber to ionize the volatile organic substance.

  Subsequently, each ionized ion is captured by an ion detection electrode to which a predetermined voltage is applied. Then, since ions or electrons are trapped by the ion detection electrode and a current flows through the ion detection electrode, the value of the current is measured by a current value measuring device.

  Next, once the current value is measured by the current value measuring device, the polarity of the voltage applied to the ion detection electrode is reversed. If it does so, the ion ionized by UV irradiation will move to the other electrode, and will be captured again. Then, since a current flows through the ion detection electrode, the value of this current is measured again by the current value measuring instrument.

  The UV irradiation range is between the ion detection electrodes and is a range biased to one of the ion detection electrodes. Therefore, the current values measured before and after inversion are different from each other. Become. Then, the calculation device for calculating the diffusion constant obtains the current ratio from the measured current values before and after inversion, calculates the diffusion constant of the volatile organic substance to be measured from the current ratio, and calculates the calculated diffusion constant. The type of volatile organic matter can be specified from the above. In addition, the type of the volatile organic substance specified by the calculated diffusion constant is displayed by a display unit provided in the calculation apparatus.

  In addition, based on the current value measured by the current value measuring device, the concentration of the volatile organic substance to be measured can also be calculated. The calculation method is, for example, toluene as described above. Then, data shown as an example in FIGS. 4 and 5 obtained by experiments in advance is stored in a storage device, and calculation is performed using the data. Furthermore, for example, when the gas to be measured contains a plurality of types of volatile organic substances, the calculated diffusion constant is the average value of the plurality of types of volatile organic substances, and this average value is displayed on the display means. If it is displayed, it becomes possible to obtain useful information as a guideline for ventilation in factories and the like.

(Volatile organic substance detection theory)
Hereinafter, the theory of calculating the diffusion constant of the volatile organic substance to be measured by the configuration of the volatile organic substance detector and the volatile organic substance detection method will be described in more detail.

  When ionization energy hν is supplied by irradiating UV to a volatile organic substance, generation of ions and recombination thereof occur. The reaction in the atmosphere can be expressed by the following formula.

For example, when light emitted from a krypton discharge (10.6 eV, wavelength 117 nm) is irradiated onto toluene which is a volatile organic substance, the toluene emits electrons and becomes a cation. Note that the mean free path until electrons collide with oxygen is about 2 μm. In the UV irradiation region, cations, electrons, and anions exist in an overlapping manner. However, k ₄ >> k ₃ holds for ions that are adsorbed by oxygen and move by an electric field. In the case of photoionization in the atmosphere, volatile organic matter becomes a cation and oxygen becomes an anion. When an electric field is applied, each ion drifts.

  Next, the theory for calculating the diffusion constant of the volatile organic substance to be measured will be described with reference to FIG. First, in general, the resistance value R when an ion having an ion density n and mobility μ moves through the space of the cross-sectional area S by a distance l is expressed by the following equation.

Here, when the positive ion mobility is μ ₊ , the movement distance is l ₊ , the negative ion mobility is μ ₋ , and the movement distance is l ₋ , the ion density n and the cross-sectional area S are the same. The resistance value R _± when both are connected in series is expressed by the following equation.

When the polarity of the voltage applied to the electrodes is reversed, in the case of state 1 shown in FIG. 3, l ₊ = d ₁ , l ₋ = d ₂ , and in state 2, l ₊ = d ₂ , l ₋ = the d _1. When the resistance value of the UV irradiation region having the thickness d ₀ is R ₀ , the resistance value R _{T1 in the} state ₁ and the resistance value R _{T2 in the} state 2 are respectively expressed by the following equations.

When the measurement target is aromatic, for example, the cation mobility μ ₊ is smaller than the anion oxygen ion mobility μ ₋ , and if d ₂ > d _{1 as} shown in FIG. _T1 < _RT2 , and the value is determined from the mobility, the electrode arrangement, the UV irradiation position, and the like. Therefore, the mobility of the ionized substance can be determined from the change in the current flowing through the electrode when the potential applied to the electrode is changed. Since the mobility μ ₋ of oxygen ions, which are anions, is known in magnitude, the mobility μ ₊ of ions of volatile organic substances that are cations can be discriminated.

In addition, when the electrode 1 in FIG. 3 is placed in the UV irradiation region and R _{0 is set} to 0, a current I ₊ that applies rate -V to the electrode 2 to mainly control the movement of cations, and the electrode 2 The magnitude of the cation mobility with respect to the anion mobility can be approximated by the following equation from the ratio of the current I ₋ where the anion movement is mainly rate-determined by applying + V to the negative electrode. In the air, since the anion is an oxygen molecule, if one known volatile organic substance is detected, a constant of the following formula is obtained.

Furthermore, regarding the ions in the gas, since the relationship of the following equation is established between the diffusion constant D and the mobility μ, that is, if the mobility μ ₊ of the volatile organic ions can be determined. The value of the diffusion constant of the volatile organic substance to be measured can be calculated, and the type of the volatile organic substance to be measured is specified from the calculated diffusion constant.

(Experiment 1)
Next, in the first embodiment of the volatile organic substance detector according to the present invention, an experiment was conducted to clarify the relationship between the applied voltage and the ionic current when toluene (20 ppm), which is a volatile organic substance, was detected. Will be described. FIG. 4 is a graph showing experimental results of the relationship between applied voltage and ion current when toluene (20 ppm), which is a volatile organic substance, is used in the first embodiment of the volatile organic substance detector according to the present invention. .

  In this experiment, a UV lamp light-emitting surface is connected to the inner wall of an ion detection chamber to which an ion detection electrode is fixed, and a measurement sample is adjusted by a calibration gas adjustment device (PD-1B-2 manufactured by Gastec Co., Ltd.). The single 20 ppm toluene gas was allowed to flow into the ion detection chamber at a flow rate of about 45 mm / s. In addition, the ammeter which measures the electric current which flows into the electrode for ion detection used DSM-8104 by Hioki Electric Co., Ltd. Moreover, the applied voltage used the voltage source which can change the value.

  As shown in the graph of FIG. 4, when the measurement target is 20 ppm of toluene, if the applied voltage is 10V, the ion current is around 1.E-09A, and if it is 100V, around 1.E-08A, If it is 1000V, it turns out that the value of 1.E-07A vicinity is measured. By storing the data obtained by this experiment in a storage device or the like, the concentration of the volatile organic substance can be calculated from the measured current value.

(Experiment 2)
Subsequently, in the first embodiment of the volatile organic matter detector according to the present invention, the relationship between the concentration of toluene at each applied voltage and the ionic current when toluene is detected as the volatile organic matter is clarified. The experiment will be described. FIG. 5 shows the relationship between the concentration of volatile organic matter (toluene) at each applied voltage and the ionic current when toluene, which is a volatile organic matter, is detected in the first embodiment of the volatile organic matter detector according to the present invention. It is the graph which showed the experimental result of.

  In this experiment, a UV lamp light-emitting surface is connected to the inner wall of an ion detection chamber to which an ion detection electrode is fixed, and a measurement sample is adjusted by a calibration gas adjustment device (PD-1B-2 manufactured by Gastec Co., Ltd.). A single gas having an arbitrary concentration of 0 to 150 ppm of toluene is introduced into the ion detection chamber at a flow rate of about 45 mm / s. The ammeter for measuring the current flowing through the electrode for ion detection uses DSM-8104 manufactured by Hioki Electric Co., Ltd., and the applied voltage uses a voltage source whose value can be changed. Voltages of 1V, 10V and 100V were applied.

  As shown in the graph of FIG. 5, when the applied voltage is 1V, 10V, and 100V, the increase rate of the value of the ionic current increases until the concentration of toluene is close to 20 ppm, and thereafter, it gradually increases. I understand. Then, by storing the data obtained by this experiment in a storage device or the like, the concentration of the volatile organic substance can be calculated from the measured current value.

(Experiment 3)
Next, in the first embodiment of the volatile organic substance detector according to the present invention, the positive / negative ion current ratio when each volatile organic substance (p-xylene, toluene, benzene) having a concentration of 20 ppm is detected as a single gas, An experiment for clarifying the relationship between the diffusion constants will be described. FIG. 6 shows an experiment of the relationship between the positive / negative ion current ratio (by applied voltage ± 100 V) and the diffusion constant when volatile organic matter (20 ppm) is detected in the first embodiment of the volatile organic matter detector according to the present invention. It is the graph which showed the result.

  First, when P-xylene is detected, the value of ion current ratio can be calculated around 0.88. And since the diffusion constant of P-xylene is around 0.07, the corresponding points are plotted. Subsequently, when toluene is detected, a value around 0.92 can be calculated as the ion current ratio. Since the diffusion constant of toluene is around 0.085, the corresponding points are plotted.

  Furthermore, when benzene is detected, the ion current ratio can be calculated as a value around 0.95. Since the diffusion constant of benzene is around 0.09, the corresponding points are plotted. By connecting these plots, one function shown in the graph is derived. When a volatile organic substance having a concentration of 20 ppm is detected, if the ionic current ratio is calculated, the volatile organic substance The diffusion constant can be derived to some extent, that is, it leads to the identification of the type of volatile organic matter. In addition, if experiments using other concentrations are performed and these data are accumulated, volatile organic substances can be detected with higher accuracy.

Next, a second embodiment of the volatile organic substance detector and the volatile organic substance detection method according to the present invention will be described with reference to the drawings.
FIG. 7 is a schematic diagram showing an example of the configuration of the detector in the second embodiment of the volatile organic substance detector according to the present invention, and FIG. 8 shows the second embodiment of the volatile organic substance detection method according to the present invention. It is an example figure which showed the detection process in a form. Further, 10 is a volatile organic substance detector, 12 is an ion detection chamber, 14 is a UV lamp, 16 is a UV lamp light emitting unit, 18 UV lamp excitation circuit, 20 is an ion detection electrode, 22 is a voltage applying means, and 24 is a current value measurement. Means 26, diffusion constant calculation means 28, information display means 28, density calculation means 30, and information correction means 32.

  First, as shown in FIG. 7, the volatile organic substance detector 10 has an ion detection chamber 12 into which a volatile organic substance to be measured flows, and the ion detection chamber 12 has a volatile organic substance on its inner wall. A UV lamp light emitting unit 16 of a UV lamp 14 for supplying ionization energy is connected. The UV lamp 14 is connected to a UV lamp excitation circuit 18 that excites the UV lamp. In the figure, the volatile organic substance to be measured flows from the left to the right in the ion detection chamber 12 in the representation of the figure, but actually flows from the back side to the near side in the figure. It is configured to let you.

  The ion detection chamber 12 is provided with a pair of ion detection electrodes 20 for capturing ions of volatile organic substances ionized by ionization energy. As the ion detection electrode 20, a SUS (stainless steel) electrode, a gold electrode, a platinum electrode, a copper electrode, or the like can be used. However, since copper has a good reactivity, the electrode surface is likely to be deteriorated. It is preferable to use a gold electrode or a platinum electrode.

  In the present embodiment, as shown in FIG. 7, the UV lamp light emitting unit 16 is provided between the electrodes of the ion detection electrodes 20 and at a position for supplying ionization energy to a range biased to one of the ion detection electrodes 20. Therefore, a range in which ionization energy is not supplied between the electrodes of the ion detection electrode 20 is formed. In the detection of volatile organic substances, the ion detection electrode 20 in the ion detection chamber 12 has a vertical length of 16 mm, a horizontal length of 6 mm, and a thickness of 1 mm, as in the first embodiment. The volatile organic substance detector 10 having a distance between the electrodes of 8.5 mm is used.

  Furthermore, since the UV lamp light-emitting part 16 of the UV lamp 14 (manufactured by Heraeus Co., Ltd., PKR106, outer diameter 12.6 mm, 10.6 eV) has a circular shape, the shape of the UV lamp light-emitting part 16 is in the electrode direction. A light-shielding cover (manufactured by GL Sciences Inc.) is attached so as to be a rectangle of 3 mm and a direction perpendicular to it (direction in which volatile organic substances flow in) 8 mm, and the range in which no ionization energy is supplied is 5.5 mm in the electrode direction. It shall be of the order. Note that a volatile organic substance detector 10 configured such that the distance between the electrodes is 8.5 mm or more and the range in which ionization energy is not supplied is 5.5 mm or more in the electrode direction may be used (between the electrodes). When the distance is increased, it is preferable to increase the range in which ionization energy is not supplied).

  Subsequently, voltage application means 22 that can apply a predetermined voltage to the ion detection electrode 20 is connected to the ion detection electrode 20, and similarly, a current value measurement means 24 is also connected. The voltage application means 22 is configured to measure the value of the current flowing through the ion detection electrode 20 when a voltage is applied.

  The voltage application means 22 is configured to be able to reverse the voltage polarity. From the current ratio of the current value flowing through the ion detection electrode 20 measured by the current measurement means 24 before and after the voltage polarity inversion, A diffusion constant calculating means 26 capable of calculating the diffusion constant of the volatile organic substance to be measured is connected to the ion detection electrode 20 together with the current value measuring means 24.

  As shown in the figure, the diffusion constant calculation means 26 is provided with an information display means 28, a concentration calculation means 30, and an information correction means 32. First, the information display means 28 is provided with the diffusion constant calculation means 26. Information on the identified volatile organics is displayed. Then, the concentration calculation means 30 can calculate the concentration of the volatile organic substance from the information of the volatile organic substance specified by the diffusion constant calculation means 26 and the current value measured by the current value measurement means 24. It has become.

  Further, when the information of the volatile organic substance displayed on the information display means 28 is wrong, the information can be corrected by the information correction means 32. When the information of the volatile organic substance is corrected by the information correcting unit 32 (for example, “NO” is selected), information on the volatile organic substance based on the diffusion constant that is approximated within a predetermined range with the calculated diffusion constant is information. A configuration is adopted in which selection is made on the display means 28, and further, selection of information on an arbitrary volatile organic substance is received from the listed and displayed information.

  And when the information regarding a volatile organic substance is selected, the information correction means 32 will make the density | concentration calculation means 30 calculate the density | concentration of a volatile organic substance again based on the information regarding this selected volatile organic substance. It has become. Since it is such a structure, the sensitivity correction | amendment of a volatile organic substance detection method can also be performed now. The concentration of the volatile organic substance may be calculated in advance by storing data in which the concentration of the volatile organic substance and the ion current are stored in advance, or the concentration may be calculated by multiplying by a predetermined coefficient. Anyway.

  In addition, for example, when the gas to be measured is made up of a plurality of types of volatile organic substances, the calculated diffusion constant is an average value of the plurality of types of volatile organic substances, so information on the volatile organic substances displayed on the display device If is wrong, it can be useful to detect the need for ventilation.

  In this embodiment, the ionization energy is supplied to the volatile organic substance by a UV lamp. However, this may be configured to irradiate the volatile organic substance with ionizing radiation, or corona is applied to the volatile organic substance. It is good also as a structure which causes discharge.

  Next, the flow of the volatile organic substance detection method in the present embodiment will be described. As shown in FIG. 8, first, UV is irradiated from a UV lamp (ionization energy supply) to the volatile organic substance that is the measurement target that has flowed into the ion detection chamber, and the volatile organic substance is ionized.

  Subsequently, each ionized ion is captured by an ion detection electrode to which a predetermined voltage is applied. Then, since ions or electrons are trapped by the ion detection electrode and a current flows through the ion detection electrode, the value of the current is measured by a current value measuring device.

  Next, once the current value is measured by the current value measuring device, the polarity of the voltage applied to the ion detection electrode is reversed. If it does so, the ion ionized by UV irradiation will move to the electrode for ion detection of the other side, and will be captured again. Then, since a current flows through the ion detection electrode, the value of this current is measured again by the current value measuring instrument.

  The UV irradiation range is between the ion detection electrodes and is a range biased to one of the ion detection electrodes. Therefore, the current values measured before and after inversion are different from each other. Become. Then, the calculation device obtains the current ratio from the measured current values before and after inversion, calculates the diffusion constant of the volatile organic substance to be measured from the current ratio, and classifies the volatile organic substance from the calculated diffusion constant. Can be specified.

  Subsequently, the type of volatile organic substance (information on the volatile organic substance) specified from the diffusion constant is displayed on the display device. Therefore, the user who performs the measurement can read from the display device what the measured volatile organic matter is. When the type of the volatile organic substance displayed on the display device is the same as the expected type, the user selects, for example, “YES” to further increase the calculated concentration of the volatile organic substance. Is displayed. For example, in the case of toluene, the concentration calculation method is such that data shown as an example in FIGS. 4 and 5 obtained by experiments in advance is stored in a storage device and calculated using the data.

  In addition, when the type of the volatile organic substance displayed on the display device is different from the assumed type, the user can use the means for correcting the type of the volatile organic substance on the calculation device to display the displayed volatile organic substance. It can be corrected to the type of volatile organic matter that was supposed to be the type of volatile organic matter.

  When the type of the volatile organic substance is corrected by the user (for example, “NO” is selected), the type of the volatile organic substance based on the diffusion constant approximated within a predetermined range is calculated on the display device. An enumeration is displayed, from which any type of volatile organic substance can be selected. Then, the concentration of the volatile organic substance is calculated again based on the selected type of the volatile organic substance and the calculated current value, and is displayed on the display device. By adopting such a flow, when a substance having low sensitivity, that is, a substance having high ionization energy is detected, sensitivity correction of the volatile organic substance detector can be performed.

  According to the volatile organic substance detector and the volatile organic substance detection method according to the present invention, the concentration of the volatile organic substance and the size of the diffusion constant which is an important property of the volatile organic substance are determined with a simple configuration and a small device. Since it is possible, it is useful for detecting volatile organic substances that need to be performed in various situations. In addition, since it is possible to specify the type of volatile organic substance from the size of the diffusion constant, the sensitivity of the volatile organic substance detector can be corrected based on the type of volatile organic substance, so that high detection accuracy is required. In this case, it becomes extremely useful.

DESCRIPTION OF SYMBOLS 10 Volatile organic substance detector 12 Ion detection chamber 14 UV lamp 16 UV lamp light emission part 18 UV lamp excitation circuit 20 Ion detection electrode 22 Voltage application means 24 Current value measurement means 26 Diffusion constant calculation means 28 Information display means 30 Concentration calculation means 32 Information correction means

Claims (5)

Ionization energy supply means for supplying ionization energy to the volatile organic matter in order to ionize the volatile organic matter;
At least one pair of ion detection electrodes for detecting the ionized ions;
Voltage application means capable of reversing the voltage polarity for applying a predetermined voltage to the ion detection electrode;
Current measuring means for measuring a current value flowing through the ion detection electrode;
A diffusion constant calculating means for calculating a diffusion constant of the volatile organic substance from a current ratio based on a current value before and after voltage polarity reversal measured by the current measuring means when the voltage polarity is reversed by the voltage applying means;
Have
The ionization energy supply means is provided between the ion detection electrodes so as to supply the ionization energy to a range biased to one ion detection electrode, so that the ionization energy is provided between the ion detection electrodes. Volatile organic matter detector, characterized in that there is a range where no is supplied.   The ionization energy supply means includes a UV irradiation means for irradiating the volatile organic substance with UV, an ionizing radiation emission means for emitting ionizing radiation to the volatile organic substance, and a corona discharge to the volatile organic substance. 2. The volatile organic substance detector according to claim 1, further comprising any one of corona discharge means to be performed. Information display means for displaying information on volatile organic substances based on the diffusion constant calculated by the diffusion constant calculation means;
Concentration calculating means for calculating the concentration of the volatile organic substance based on the information on the volatile organic substance based on the diffusion constant calculated by the diffusion constant calculating means and the current value measured by the current measuring means;
When the information on the volatile organic substance can be corrected, and the information on the volatile organic substance is corrected, the information display means lists information on the volatile organic substance based on a diffusion constant that approximates the diffusion constant within a predetermined range. In addition, the information on the volatile organic matter is selected from the listed and displayed information, and the information on the selected volatile organic matter is measured by the concentration calculating means, and the current measuring means measures Information correction means for again calculating the concentration of the volatile organic substance from the current value,
The volatile organic substance detector according to claim 1 or 2, characterized by comprising: An ionization step of supplying ionization energy to the volatile organic substance and ionizing the volatile organic substance;
An ion detection step of detecting ions ionized by the ionization step with at least one pair of ion detection electrodes to which a predetermined voltage is applied;
A current value measuring step of measuring a current value flowing through the ion detection electrode;
By inverting the polarity of the voltage applied to the ion detection electrode, the current ratio is obtained from the current value flowing through the ion detection electrode before and after the inversion, and the diffusion constant of the volatile organic matter is determined from the current ratio. A diffusion constant calculating step to calculate;
Including
In the ionization process, the ionization energy is supplied between the ion detection electrodes by supplying the ionization energy to a range biased to one of the ion detection electrodes. A volatile organic substance detection method characterized by producing a range that is not supplied and supplying ionization energy to the volatile organic substance. An information display step for displaying information on volatile organic substances based on the diffusion constant calculated in the diffusion constant calculation step;
A concentration calculating step for calculating the concentration of the volatile organic matter from the information on the volatile organic matter based on the calculated diffusion constant and the current value measured by the current value measuring step;
A correction accepting step for accepting correction of information on the volatile organic matter displayed by the information displaying step;
When the information regarding the volatile organic matter is corrected by the correction acceptance step, the information regarding the volatile organic matter is calculated again from the information regarding the corrected volatile organic matter and the current value measured by the current value measurement step. Correction process;
The volatile organic substance detection method according to claim 4, comprising: