JP2012058111A - Sampling bag and sampling method of floating fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sampling bag and sampling method of floating fine particles for precisely analyzing/measuring floating fine particles in atmosphere gas.SOLUTION: The sampling bag includes a sampling bag body comprising an insulator, an introduction/output comprising an insulator attached to the sampling bag body, and a needle electrode which is provided so that its tip is located at a central part of the sampling body and is connectable to a power source. While the atmosphere gas containing floating fine particles of grain diameter equal to or smaller than 2.5 μm is sampled in the sampling bag, the power source is connected to the needle electrode, voltage equal to or larger than 3 kV is applied to generate corona discharge, and static electricity of the floating fine particles is removed.

Description

  The present invention relates to a floating particulate collection bag and a collection method for collecting fine particles floating in an atmospheric gas and using them for various analyzes and measurements.

  Fine particles suspended in the atmosphere (hereinafter referred to as “atmosphere gas”) such as the atmosphere or factory are concerned about various effects on the human body. From this viewpoint, various standards have been established for regulating suspended particles. In order to satisfy these standards, a technique for analyzing and measuring the properties of suspended particulates is required, and various techniques have been developed so far.

  As a method for measuring the weight of suspended fine particles in various atmospheric gases, there are a method for analyzing scattered light generated by irradiating continuously introduced fine particles with laser light, and collecting fine particles on a filter to obtain β A method of irradiating a line and analyzing from the attenuation rate is common. In particular, since the former can stably measure the weight, a measuring apparatus is also commercially available (for example, Thermo SHARP5030) and widely used.

  As an elemental analysis method for suspended particulates, suspended particulates in atmospheric gas are collected on a filter for a certain period of time, and the collected particulates are scanned using a scanning electron microscope (SEM), electron beam microanalysis (EPMA), or laser emission. A method of analyzing component elements and their amounts by performing analysis using spectroscopic analysis, secondary ion mass spectrometry (SIMS), or the like, or analysis by chemical treatment is known.

  In addition, as a method for continuously elemental analysis of suspended fine particles in an atmospheric gas, a method (Patent Document 1) in which suspended fine particles are introduced into a high frequency inductively coupled plasma mass spectrometer (ICP-MS) has been reported. ing. In addition, the suspended fine particles taken into the vacuum via a capillary or the like are ionized by irradiating laser in a pulsed manner and using a time-of-flight mass spectrometer (TOF-MS) (Patent Document 2, Non-Patent Document 1). A method of analyzing by analysis, luminescence analysis or mass spectrometry (Patent Document 3) has been reported. These analysis methods can obtain average element information of thousands to hundreds of thousands of suspended particles in a short time.

  In any of the above-mentioned methods, the suspended particles are directly collected and analyzed / measured at the site, and once the suspended particles are aspirated and collected in the collection bag using a suction pump, etc. Analysis and measurement may be performed by supplying fine particles in the collection bag to a certain analysis / measurement device. In particular, the latter method using a collection bag must be used in places where it is difficult to bring in an analysis / measurement device, such as in a poor environment such as a high temperature environment or a low temperature environment, or in a high place. However, the method using the collection bag has the following problems.

  Particles having a particle size of several tens of μm or more naturally settle over time due to gravity. For this reason, if the settled fine particles adhere to or accumulate on the inner wall of the collection bag, it is difficult to collect the total amount of fine particles from the collection bag, and the accuracy of the analysis and measurement of the fine particles using the collection bag is not good.

  On the other hand, PM2.5 (fine particles with a particle size of 2.5 μm or less suspended in the atmospheric gas) that has been attracting attention in recent years is estimated to be semipermanently suspended in the atmospheric gas. There is no problem of the natural sedimentation described above, and it is considered that the analysis and measurement of fine particles using a collection bag can be performed with high accuracy.

Japanese Patent Laid-Open No. 10-288601 JP-A-10-288602 JP 2006-071492 A Japanese Patent Laid-Open No. 2005-147861 JP-A-2005-283212 JP 2007-127427 A

E.Gard et.al., Ana1.Chem.69, p.4083 1997

  However, as a result of examination by the present inventor, even when suspended particles having a particle size of 2.5 μm or less, the suspended particles are analyzed and analyzed as the elapsed time from collection into a collection bag to use for analysis / measurement increases. It has been found that the measured value may decrease and an accurate value may not be obtained. This was presumed to be caused by static electricity generated by the collected floating particles colliding with each other in the collection bag or colliding with the inner wall of the collection bag. That is, the floating particles charged by the static electricity generated in this way are adsorbed on the inner wall of the collection bag, or the particles adhere to each other and become larger, settle, adsorb and deposit on the inner wall, and remain in the bag as they are. As a result, the amount of fine particles used for analysis / measurement is considered to decrease. In particular, many of the commercially available collection bags use vinyl-based or polyester-based materials, and the collection bags themselves have a property of being easily charged with static electricity, which is considered to promote the above-described phenomenon.

  Therefore, in order to solve the above problem, it is conceivable to perform electrification removal (hereinafter, also referred to as charge removal) of the suspended fine particles collected in the collection bag. A technique using corona discharge has been developed as a charge removal technique, and commercially available products include SJ-H and SJ-F series manufactured by Keyence Corporation. This technology removes static electricity by blowing air ionized by corona discharge onto an object (for example, an industrially produced resin sheet, film, semiconductor wafer, etc.), and is effective for stable production of products. It is used as a means. However, this technique is difficult to apply to the charge removal of suspended particulates in the collection bag targeted by the present invention.

  The present invention has been made in view of the above-described circumstances, and provides a floating particulate collection bag and a collection method that can accurately analyze and measure suspended particulate in an atmospheric gas. It is an object of the present invention to provide a floating particulate collection bag and a collection method that can accurately analyze and measure suspended particulates by eliminating static electricity from electrostatically charged suspended particulates in the bag.

  Although not a charge removal technique, Patent Documents 4 to 6 disclose a technique for efficiently collecting floating particles using static electricity. However, these techniques are to collect fine particles by charging them and attracting them to a dust collecting electrode or a collection plate, and are not a reference for the present invention for the purpose of removing static particles from the collection bags.

  As a result of diligent studies to solve the above problems, the present inventor has developed a corona discharge inside the collection bag to prevent atmospheric particles collected in the collection bag from adsorbing to the inner wall of the bag. The present invention has been completed by conceiving that the static electricity generated by the collision of fine particles may be removed by this ionized atmospheric gas.

That is, the present invention has the following features in order to solve the above problems.
[1] A collection bag of floating fine particles for collecting floating fine particles having a particle diameter of 2.5 μm or less contained in an atmospheric gas, the collection bag body made of an insulator collecting the atmospheric gas containing the floating fine particles, An inlet / discharge port made of an insulator for introducing and releasing the atmospheric gas containing the suspended fine particles into and from the collection bag body, and a tip is located at the center of the collection bag body, and is connected to a power source. A collection bag of suspended fine particles, characterized by comprising needle-shaped electrodes configured to be possible.
[2] A collection bag main body made of an insulating material, an introduction / discharge port made of an insulating material attached to the collection bag main body, and a tip positioned at the center of the collection bag main body, connected to a power source A floating particulate collection method for collecting an atmospheric gas containing suspended particulates having a particle diameter of 2.5 μm or less using a suspended particulate collection bag comprising a needle-shaped electrode configured to be possible, the collection bag body In addition, while collecting atmospheric gas containing suspended fine particles having a particle size of 2.5 μm or less, the power supply is connected to the needle-like electrode and a voltage of 3 kV or more is applied to generate a corona discharge. A method for collecting airborne particles, which comprises removing static electricity from airborne particles.

  In the present invention, “floating fine particles having a particle diameter of 2.5 μm or less” means that the aerodynamic diameter (the diameter of a virtual water droplet that exhibits the same behavior in the air as the target particles) is 2.5 μm or less. It is a floating fine particle.

  According to the present invention, it is possible to remove static electricity generated when airborne particles collide with the inner wall of the bag or particles collide with each other while airborne particles are collected in the collection bag. Therefore, almost all the fine particles can be supplied to the analysis / measurement device without adsorbing and remaining on the inner wall of the bag, and the analysis / measurement of the floating fine particles can be performed with high accuracy.

It is a figure which shows the collection bag of floating particulates concerning embodiment of this invention. It is a systematic diagram for supplying suspended particulates in a collection bag to an analysis and measurement device. It is a figure which shows the result of having analyzed the component of the floating particulates extract | collected by the collection bag concerning an Example. It is a figure which shows the result of having analyzed the component of the floating particulates extract | collected by the collection bag concerning a comparative example.

  In the present invention, a needle electrode is attached to the collection bag, and a high voltage is applied to the needle electrode to generate a corona discharge from the tip. And while collecting the atmospheric gas containing the suspended fine particles in the collection bag, corona discharge is generated from the tip of the needle electrode to ionize the atmospheric gas in the bag, and the ionized atmospheric gas in the bag Since the static electricity of the suspended particles is removed, it is possible to prevent the suspended particles from aggregating or adhering to the inner wall of the bag due to the static electricity.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a collection bag for suspended particles according to the present invention. In FIG. 1, reference numeral 1 denotes a collection bag, which includes a collection bag main body (sometimes referred to as a bag main body) 2, an introduction / discharge port 3, and a needle electrode 4. The collection bag body 2 is made of an insulating material such as a fluorine-based resin (for example, FEP) or a polyester-based resin (for example, PET), and may have any shape as long as the atmospheric gas can be collected inside. The size (capacity) is not particularly specified, but is preferably about 1000 liters or less in consideration of convenience such as carrying. The thickness is not particularly specified as long as it has a thickness that does not cause dielectric breakdown when a voltage is applied. The introduction / discharge port 3 is attached so as to penetrate the inside and outside of the collection bag main body 2, and the material thereof needs to be an insulating material such as a resin like the bag main body 2. The needle electrode 4 is made of Cu, Pt or the like, and is attached so that the tip thereof is located at the center of the collection bag body 2. By doing in this way, charge removal of floating particulates can be performed efficiently.

  Reference numeral 5 denotes a power source such as a battery, and reference numeral 6 denotes a ground (earth), which can be connected to and disconnected from the needle electrode 4. The power source 5 applies a high voltage to the needle electrode 4 and may use either a DC power source or an AC power source. However, the AC power source is more preferable because it can remove both positive and negative charges at once. The capacity of the power source 5 needs to be 3 KV or more in order to stably generate corona discharge. The upper limit is not particularly defined, but if it is too high, it is preferable to set it to 10 kV or less practically because the bag body 2 breaks down or the power source itself becomes large.

  Next, a method for collecting atmospheric gas containing suspended fine particles using the collection bag 1 will be described. The collection bag 1 is brought into the site where the measurement target atmospheric gas is present, and the atmospheric gas is sucked and collected. At the time of collection, a suction pump (not shown) is attached to the introduction / discharge port 3, and atmospheric gas is taken into the inside of the collection bag body 2 together with the suspended fine particles by this suction pump. After completion of the suction, the suction pump is removed from the introduction / discharge port 3, and a cap (not shown) is put on and sealed. Next, the power source 5 is connected to the needle electrode 4 and a voltage of 3 kV or more is applied to the needle electrode 4 to generate a corona discharge from the tip.

  When corona discharge occurs, the atmospheric gas present around the needle electrode 4 is ionized to become ions. Static electricity generated in the fine particles by collision of the suspended fine particles trapped in the bag main body 2 with each other or with the inner wall of the bag main body 2 is removed by the ionized atmospheric gas. Therefore, in the case of fine particles having a particle size of 2.5 μm or less, they do not adhere to the inner wall of the bag body due to static electricity and continue to float in the bag body. In order to reliably remove static electricity, it is necessary to continue the corona discharge from the collection of the atmospheric gas in the collection bag to the supply of the atmospheric gas to the analysis / measurement device.

  Under a certain environment, a suction pump is attached to the inlet / outlet 3 (material: vinyl fluoride resin, diameter: 8 mmφ) of the collection bag 1, and the atmosphere is collected by the suction pump (volume: 20 liters, material: foot). (Vinyl chloride resin, thickness: 20 μm) 2 was sucked and collected and sealed to prepare a sample. Next, a power source 5 (AC 5 kV) was connected to the needle electrode 4 to continuously generate corona discharge from the needle electrode 4. The collection bag 1 in this state was connected to an ICP-MS (high frequency inductively coupled plasma mass spectrometer), and after disconnecting from the power source 5, the air in the bag was supplied to the analyzer. Supply to ICP-MS was performed 5 times at intervals, and the analysis was performed each time. In addition, when aspirating the air, the sample was classified into suspended fine particles having a particle size of 2.5 μm or less (sample A) with a cascade impactor (manufactured by Tokyo Direc Co., Ltd.), and the sample was aspirated as it was without classification. Two types (Sample B) were prepared.

  In FIG. 2, the systematic diagram by a present Example for using the suspended fine particle in a collection bag for ICP-MS is shown. When the fine particles in the collection bag are directly supplied to the ICP-MS, the air in the bag is also supplied at the same time, the plasma in the ICP-MS is extinguished, and analysis becomes impossible. Therefore, in this example, the collection bag 1 was connected to a gas exchanger 10 (manufactured by Sumitomo Seika Co., Ltd.), and the atmosphere in the collection bag was replaced with Ar gas 11. The substituted atmosphere was discharged as exhaust 12. In the figure, reference numeral 13 denotes Ar gas as an aspirator gas. By supplying the aspirator gas 13, the atmosphere in the collection bag 1 is sucked into the gas exchanger 10. Further, Ar gas containing Cr fine particles was supplied as the standard gas 14 on the entrance side of the ICP-MS 16. Reference numeral 15 denotes Ar gas as the carrier gas 15. By using the standard gas, it is possible to obtain the ion intensity ratio between the element contained in the fine particles to be analyzed and Cr in the standard gas, thereby reducing the effect of ICP-MS drift (time-dependent change). Can be removed. In addition, when the element to be analyzed in the fine particles to be analyzed is Cr, an element other than Cr, for example, a standard gas containing Mo may be used.

  FIG. 3 shows the analysis results. Al (mass number 27), K (mass number 39), and Fe (mass number 57), which are representative of the elements constituting the suspended fine particles, are shown. The horizontal axis represents time (Hr), and the vertical axis represents the ratio of ionic strength of each element to Cr (mass number 53). Sample A classified to a particle size of 2.5 μm or less obtained a stable ionic strength ratio regardless of the elapsed time, and the effect of the present invention was confirmed. On the other hand, Sample B that was not classified showed a tendency that the ionic strength ratio decreased with time. This is because even if static elimination is performed by corona discharge, fine particles with a particle size exceeding 2.5 μm naturally settle with time and adhere to and accumulate on the inner wall of the collection bag, and these adhered and deposited fine particles remain in the bag as they are. This is presumably because it is not introduced into ICP-MS.

  Next, as a comparative example, FIG. 4 shows the result of analysis by the same method as described above without performing neutralization by corona discharge. In both the sample A subjected to the classification treatment and the sample B not subjected to the classification treatment, the ionic strength ratio tended to decrease with time. This is considered to be caused by the fact that coarse particles in the fine particles settle with time and fine particles having a particle size of 2.5 μm or less adhere to the inner wall of the bag due to static electricity. When comparing the sample B in FIG. 4 and the sample B in FIG. 3, it can be seen that the latter is less likely to decrease. Also from this point, the effect of removing static electricity by corona discharge of the present invention can be confirmed.

DESCRIPTION OF SYMBOLS 1 Sampling bag 2 Sampling bag main body 3 Inlet / discharge port 4 Needle electrode 5 Power supply 6 Grounding (earth)
10 Gas exchanger 11 Ar gas 12 Exhaust (atmosphere)
13 Aspirator gas (Ar gas)
14 Standard gas (Ar gas + Cr particles)
15 Carrier gas (Ar gas)
16 High frequency inductively coupled plasma mass spectrometer (ICP-MS)

Claims (2)

  A floating particulate collection bag for collecting suspended fine particles having a particle size of 2.5 μm or less contained in an atmospheric gas, the collection bag body made of an insulator for collecting the atmospheric gas containing the suspended fine particles, and the suspended particulate An introduction / discharge port made of an insulating material for introducing and releasing an atmospheric gas containing the gas into the collection bag body, and a tip is located at the center of the collection bag body, and can be connected to a power source. A collection bag of suspended fine particles, characterized by comprising: A collection bag body made of an insulator, an introduction / discharge port made of an insulator attached to the collection bag body, and a tip positioned at the center of the collection bag body so that it can be connected to a power source A floating particulate collection method for collecting an atmospheric gas containing suspended particulates having a particle diameter of 2.5 μm or less using a suspended particulate collection bag comprising a needle-shaped electrode, wherein While collecting atmospheric gas containing suspended fine particles having a diameter of 2.5 μm or less, the power source is connected to the needle-like electrode and a voltage of 3 kV or more is applied to generate a corona discharge. A method for collecting airborne particles, characterized by removing static electricity.

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