JP2007139733A - Microchannel scrubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and inexpensive gas collector for measuring an extremely low concentration of gas on real time. <P>SOLUTION: A microchannel of honeycomb structure is formed to fix a hydrophobic gas permeable membrane thereon. The gas permeable membrane is fixed in a process of polymerization solidification, when using a poly-dimethyl siloxiane (PDMS) as a base material for preparing the microchannel. A very thin liquid layer is formed over a wide area by forming not a simple microchannel but honeycomb type one. The absorption efficiency of the gas is enhanced thereby to collection-enriching a gas component in the absorption liquid layer even in a sort absorption time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention collects a very small amount of components present in the air and is related to measurement continuously or intermittently, and provides simple and highly sensitive measurement in fields such as environmental science and medical diagnosis. is there.

Conventional technology

In conventional wet gas analysis, a method is used in which a sample gas is introduced into an absorption solution installed in an impinger by aeration. This method is also defined by JIS. This method may be used when the target component is contained at a high concentration as in the case of exhaust gas. However, when the component in the atmosphere is examined, a long time collection is required. However, ideally it is desirable to collect in a short time or perform a continuous analysis. Therefore, a so-called gasket-type flat gas collecting device in which a gasket is cut out to form an absorption liquid flow path and covered with a gas-permeable material is often used. For example, there is an example such as Non-Patent Document 1. In addition, as in Patent Document 1, a gas collector in which the channel is covered with a silicone film has also been reported.
Japanese Patent Application No. 2003-045742 Micro gas collector Analytical Chemistry, 74, 5890 (2002)

When a trace gas component contained in the atmosphere or the like is analyzed by a wet method, a sample gas is passed through an impinger and collected in an absorbing solution, and then a reaction product is measured. In this case, in order to obtain a concentration sufficient for measurement in the absorbing solution, it has been necessary to collect for a long time. In addition, since a large-scale device is required for the measurement, it is difficult to analyze it on site.

In order to solve these problems, there is a gasket type gas collector. Here, in order to further increase the sensitivity, it was necessary to reduce the thickness of the gasket. This is because the concentration of the analyte after absorption is inversely proportional to the thickness of the liquid layer. However, it is not realistic to prepare gaskets of arbitrary thickness, and there are limits to the gasket materials that can be obtained to reduce the thickness.

Another problem with thinning the liquid layer is that it is difficult to keep this thickness constant. If the substrate or the gas permeable material is bent even a little, the thickness of the liquid layer changes. In some cases, the substrate and the permeable material are in close contact with each other, and the absorbing liquid may not flow.

In order to solve such a problem, a device for taking gas into a narrow groove, that is, a microchannel has been devised (Japanese Patent Application No. 2003-045742). However, in order to obtain an effective absorption area, it is necessary to lengthen the channel. there were. Therefore, the flow resistance is large and it is difficult to flow the absorption liquid, and the required flow rate of the absorption liquid is as small as about 2 microliters per minute. In addition, the area of contact with the gas-liquid was insufficient with respect to the total area of the gas collection surface, about 5%.

A microchannel having a honeycomb structure was formed on the surface of a plate made of polydimethylsiloxane (PDMS) to provide a place for storing the absorbing liquid. A hydrophobic membrane is fixed on the microchannel. An absorbing solution or absorbing reaction solution is allowed to flow through the microchannel, an air sample is introduced outside the hydrophobic membrane, and the target component is taken in through the hydrophobic membrane.

An ultrathin liquid layer can be obtained with a certain thickness by the microchannel of the honeycomb structure. In addition, the gas absorption area can be increased. The absorption reaction liquid spreads uniformly on the absorption surface while repeating the branching and collection of the liquid according to the grooves of the honeycomb. Even if there is a defect somewhere in the channel, the absorption reaction solution flows around the channel around the channel, so there is little influence on the overall characteristics.

Since gas is collected with high efficiency, extremely low concentration gas can be measured in real time or in a short time. Also, the absorption reaction solution can be easily supplied with a flow rate of the absorption reaction solution of 10 to 100 microliters per minute.

Since a base material made of PDMS is used for the microchannel, the gas permeable membrane can be fixed in the process of PDMS polymerization and solidification. Therefore, it can be fixed without using an adhesive. An example of fixing using an adhesive has also been reported, but in this case, the adhesive flows into the channel and greatly affects the microchannel of the microstructure.

Hydrogen sulfide and sulfur dioxide were taken into a microchannel gas collector with a honeycomb structure, and then both gases were detected with a microdetector. In the case of hydrogen sulfide, a fluorescein mercury acetate solution was used, and fluorescence of fluorescein mercury acetate was measured downstream. On the other hand, sulfur dioxide was calculated from conductivity detection. An example of the response is shown in FIG.

It is a schematic representation of a gas permeable membrane attached to a honeycomb microchannel. FIG. 1 shows an example in which hydrogen sulfide and sulfur dioxide are simultaneously measured using a gas collector. It can be seen that hydrogen sulfide reduces the fluorescence signal of fluorescein mercury acetate and sulfur dioxide increases the conductivity signal. A sufficient response is obtained even in the order of ppb.

Explanation of symbols

1 Gas-permeable membrane 2 Microchannel 3 Microchannel block 4 Absorption liquid inlet 5 Absorption liquid outlet

Claims (11)

Microchannel 2 characterized in that the contact area with the gas-liquid is 30% or more with respect to the total area of the gas collecting surface, block 3 on which microchannel 2 is provided, and microchannel 2 And a gas permeable membrane 1 having a thickness of 30 μm or less provided on the micro gas collector. The micro gas collector according to claim 1, wherein the micro channel (2) is formed in a honeycomb shape. The micro gas collector according to claim 1 or 2, wherein the flow path of the microchannel 2 has a depth of 10 to 200 µm and a width of 40 to 1000 µm. The block 3 is a resin block such as polydimethylsiloxane, polysilicone, acrylic resin, polyvinyl chloride resin, or fluororesin, or an inorganic substrate such as quartz, glass, silicon, or alumina. The micro gas collector of 1-3. The micro gas collector according to claim 1, wherein the permeable membrane is a porous Teflon membrane. 6. The micro gas collector according to claim 1, wherein the permeable membrane is a single membrane fixed to the block. The micro gas collector according to claim 1, wherein the permeable membrane is fixed to the block by a thermal bonding method. 2. The substrate for forming a permeable membrane, wherein the surface is previously treated with fluorinated silane in order to peel the permeable membrane from the substrate after bonding the permeable membrane and the block. The micro gas collector according to -7. A gas analysis method characterized by flowing an absorption solution or an absorption reaction solution into the microchannel according to claim 1 and taking in a target component of an air sample through a permeable membrane. 10. A gas analysis method according to claim 9, wherein the air sample is hydrogen sulfide and the absorption reaction solution is alkaline fluorescein mercury acetate. 10. A gas analysis method according to claim 9, wherein the atmospheric sample is sulfur dioxide, and the absorption reaction solution is a slightly sulfuric acid acidic hydrogen peroxide solution.

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