JPS6396535A - Method and device for measuring volatile component - Google Patents

Abstract

PURPOSE:To measure the concentration of a volatile component in a solution to be inspected, by sampling by carrier gas, the volatile component in the solution to be inspected, and measuring the concentration of the volatile component in the carrier gas. CONSTITUTION:Carrier gas flows downward through the inside of an inner pipe 1, its flow is turned back in a low part 3 and the flow is changed upward between an outer pipe 4 and the inner pipe 1, becomes the same temperature as that of a solution to be inspected 6 by a heat exchanging action of a foaming metal 5, its temperature further rises and a volatile component in the solution to be inspected 6 is brought to sampling through a porous polyethylene fluoride film 7 and placed in the carrier gas. The carrier gas on which ethyl alcohol is placed further ascends and warmed slightly in order to prevent a dew fall by a stainless steel pipe 9 containing a heater, and exhausted from an exhaust port 11 through an alcohol gas sensor 10. In the inside of the inner pipe 1, a temperature sensor 13 is installed, and a measuring wire 14 is drawn out through the inside of the inner pipe 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for measuring the concentration of volatile components in a sample liquid such as an aqueous solution, and in particular to a method and apparatus for measuring the concentration of volatile components in a sample liquid such as an aqueous solution. The present invention relates to a volatile component sampling device that indirectly determines the volatile component concentration in an aqueous solution by placing a volatile component gas on the carrier gas and measuring the volatile component gas concentration on the carrier gas.

Bika standing leg fish Conventionally, this field has had the following problems.

Unless the surface area of the gas-permeable membrane was made sufficiently large, it took a long time for the volatile component gas concentration on the carrier gas to stabilize.

In addition, unreproducible data was sometimes obtained for unknown reasons.

For this reason, the overall size of the sampling device has increased, and it has been necessary to make the device more compact.

``Skin development'' The present invention solves the above problems.

In the present invention, a carrier gas for sampling volatile components in a test liquid is adjusted to near the temperature of the test liquid outside the sampling area, and then the volatile components are sampled with this carrier gas. Provided is a method for measuring the concentration of a volatile component in a test liquid by measuring the concentration of the volatile component.

Preferably, the ambient temperature of the gas sensor is maintained at a temperature close to that of the test liquid outside the sampling section.

It is also possible to measure the temperature of the gas sampling section and functionally correct the output value of the volatile component by the gas sensor using the measured temperature value and display or use it.

Furthermore, the present invention uses a hydrophobic porous membrane that uses heat exchange to adjust the temperature of the carrier gas to around the temperature of the sample liquid near the sampling part, and samples volatile components in the sample liquid using the carrier gas flowing inside. The present invention provides an apparatus for measuring volatile component concentration, which includes a sampling section and a gas sensor for measuring volatile component concentration in carrier gas.

The present invention is characterized in that a heat exchange section is provided at a sampling site for volatile components using a hydrophobic porous membrane, and sampling is performed using a carrier gas while maintaining a temperature close to that of the sample liquid outside the sampling device. This is a sampling device for volatile components.

This sampling device includes the following preferred embodiments.

Gold Vf1it fiber or foam metal is used as the heat exchanger.

The hydrophobic porous membrane is made of porous polyfluorinated ethylene resin or porous tetrafluorinated propylene copolymer resin.

The hydrophobic porosity is tube-shaped.

Carrier gas flows down from the top of the inner tube of the double tube, ascends through the heat exchange section inside the outer tube from the folding point at the bottom, and is then sampled for volatile components in the hydrophobic porous membrane tube that forms part of the outer tube. Do this.

Carrier gas flows down from the upper part of the outer tube of the double tube, flows down through the upper heat exchange section, and then gas sampling of volatile components is performed in the hydrophobic polyfilm tube that forms part of the outer tube. Raise the inner tube further and perform sampling.

A portion of the inner tube of the double tube corresponding to the hydrophobic porous membrane tube is protruded, a temperature sensor is installed inside the protrusion, and the lead wire of the temperature sensor is pulled out through the inner upper part of the inner tube for gas sampling of volatile components. Measure the temperature of the sampling section.

Install a heater inside or outside the outer pipe of the double pipe.

A heater covered with a metal tube with an outer diameter of 2 mm or less is used.

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

The experiment was conducted using the apparatus shown in FIG. 1 is air (flow rate 200 cc/min) as a carrier gas, and 2 is a sampling tube made of porous polyfluorinated ethylene with four fingers as a gas permeable membrane.

3 is an aqueous solution containing 10% ethyl alcohol as a test liquid, and the temperature is 30°C.

4 is a catalytic combustion type alcohol gas sensor using platinum.

Alcohol vapor is added when the carrier gas passes through the sampling tube 2, and is measured by the alcohol gas sensor 4.

Figure 2 shows the output (5) of the alcohol gas sensor (hereinafter referred to as gas sensor) and the time to reach a stable output (6) with the effective surface area of the sampling tube in Figure 1 and 2 on the horizontal axis.
) is shown on the α axis.

FIG. 3 is a graph using the apparatus shown in FIG. 1, using a 10% alcohol aqueous solution as the test liquid, with temperature on the horizontal axis and the output of the gas sensor (FIG. 1, 4) on the orange axis.

It can be seen that the larger the area, the closer the output value to the effective surface area in FIG. 25 is to the equilibrium vapor pressure of the alcohol aqueous solution. If the effective surface area is small compared to the carrier gas flow rate, the alcohol vapor will be diluted with the carrier gas, resulting in low output. However, as shown in FIG. 2 and 6, when the effective surface area becomes small, it takes a long time to reach a stable output value, which is a problem and is also an inconvenience for downsizing the device.

As a result of various considerations and experiments regarding this problem, the second
The cause as shown in Figure 6 is that when alcohol vapor evaporates into the carrier gas at the polyfluoroethylene resin interface, it absorbs the heat of vaporization, lowering the temperature of the carrier gas and the temperature of the sample liquid around the sampling device. It turns out that it takes a long time to reach i.

This phenomenon is caused by the fact that the output of the gas sensor is almost proportional to the temperature, as shown in FIG. 3, so it can be fully understood that a drop in temperature impairs the stability of the output of the gas sensor.

Furthermore, when the carrier gas goes from the sampling tube in Figure 1 to the gas sensor 4, if the temperature drops below the temperature of the sampling tube or the liquid to be tested in 3, condensation of water or alcohol vapor will occur. It was found that this makes the output of the gas sensor unstable.

The present invention is an attempt to solve these problems as described above by using a sampling device with a double tube structure having a heat exchange section using foamed metal or metal fibers as a particularly preferable means. . Examples are shown below.

Fig. 4 is a diagram showing an embodiment of the sampling device of the present invention. 1 is an inner tube, and the carrier gas flows downward inside 2, and at the bottom of 3, the flow is turned around and flows upward between the outer tube 4 and the inner tube 1, and the heat exchange of the foamed metal 5 takes place. As a result, the temperature becomes the same as that of the test liquid 6, and the temperature rises further to sample the volatile components (ethyl alcohol in this case) in the test wave 6 through the porous polyfluorinated ethylene resin film 7, and then the carrier gas Place it inside.

Foamed metal 8 is also used here.

The carrier gas carrying ethyl alcohol vapor further rises, is lightly warmed by a stainless steel pipe 9 with a built-in heater to prevent rEv3, and is exhausted from 11 through an alcohol gas sensor 10. In this case, if the metal tube straight rod of the heater is 2 mm or more, internal processing will be difficult, so it needs to be 21 mm or less. Incidentally, a portion 12 of the inner tube 1 protrudes to form a porous polyfluorinated ethylene mMB of 7.
A temperature sensor 13 is installed inside the film and is in contact with the film, and this measuring line 14 is drawn out through the inside of the inner tube 1 and is drawn out from an inlet 16 different from the inlet of the carrier gas 15.

Note that 17 is an outlet for the heater tube. Naturally, the outlets of these wires and tubes have a sealed structure. With such a structure, temperature fluctuations during gas sampling can be suppressed, and a stable sensor with faster response can be obtained.

5 is a diagram showing an embodiment of the present invention. Similar to FIG. 4, the carrier gas 15 flows down on the outside to bring it to the same temperature as the test liquid 6 through heat exchange in step 4, and then the volatile gas is sampled with the sampling film 7 at the bottom. The gas rises through the interior of the inner tube 1 and reaches the alcohol gas detector 10.

Although this structure is more compact than the first embodiment, it has the disadvantage that the temperature sensor cannot be drawn out through the inner tube before sampling the volatile gas. This is because these extraction glands and their plastic coverings are present in volatile gases.
This is because, due to the adsorption of gas onto the material, the fast response of gas sampling is inhibited by the buffering effect of adsorption and desorption.

Figure 6 shows the sampling device of Example 3, which is almost the same as Figure 4, but after sampling the gas onto the carrier gas 15, the 18 gas detection elements are covered with foam metal. , which measures gas immediately on the spot.

In this case, there is an advantage that the entire device including the gas sensor can be made smaller, but at present, small sensors made of semiconductors, for example, that can be embedded in the sampling device have insufficient measurement accuracy and reproducibility. I don't have good sex. In addition, the necessary force is required to push the gas detection element 18 deep enough to the height of the test liquid 6 and to make the ambient temperature of the gas detection element 18 constant. be. This makes the characteristics of the gas detection element extremely stable.

In these measurements, the temperature of the test liquid is measured and the output of the gas sensor is corrected functionally. Simply dividing by the temperature expressed in 4 degrees Celsius is very effective in stably displaying the concentration of the test liquid.

FIG. 7 shows a comparison between using and not using function correction. The horizontal axis is the time axis and the vertical axis is the output. 1 is temperature,
2 is the output of the sensor without correction, and 3 is the value when corrected by division. It can be seen that fluctuations caused by temperature are kept fairly low, and the accuracy is improved overall.

The foam metal described above may be replaced with metal fiber. Also, the porous polyfluorinated ethylene resin can be replaced with a porous polyfluorinated propylene resin.

As described above, the volatile component sampling gas sensor according to the present invention provides a sampling gas sensor with more stable performance, and will greatly contribute to the fermentation industry, the sake brewing industry, and others.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 show experimental means according to the present invention and their experimental results. FIG. 4, FIG. 5, and FIG. 6 are diagrams explaining each embodiment of the present invention. FIG. 7 is a diagram showing the stability of output when temperature is corrected. Ml Figure (Yaichipotqm/←Yukuzu/l;' rffM5 Kuchitomo 6 (2)

Claims (1)

[Claims] 1) A carrier gas for sampling volatile components in a test liquid is adjusted to near the temperature of the test liquid outside the sampling area, and then the volatile components are sampled with this carrier gas. , a method of measuring the concentration of volatile components in a test liquid by measuring the concentration of volatile components in a carrier gas. 2) The method according to claim 1, characterized in that the ambient temperature of the gas sensor is maintained at a temperature close to that of the test liquid outside the sampling section. 3) The temperature of the gas sampling section is measured, and the output value of a volatile component by a gas sensor is functionally corrected by the measured temperature value and displayed or used. the method of. 4) A heat exchange part that adjusts the temperature of the carrier gas to around the temperature of the test liquid near the sampling part, and a sampling part that is made of a hydrophobic porous membrane that samples volatile components in the test liquid using the carrier gas flowing inside. and a gas sensor that measures the concentration of volatile components in a carrier gas. 5) A volatile component characterized in that a heat exchange part is provided at the volatile component sampling site using a hydrophobic porous membrane, and sampling is performed using a carrier gas while maintaining a temperature close to that of the liquid to be exposed outside the sampling device. sampling equipment. 6) The volatile component sampling device according to claim 6, characterized in that metal fibers or foamed metal are used as the heat exchange part. 7) The volatile component sampling device according to claim 6, wherein the hydrophobic porous membrane is made of porous polyfluoroethylene resin or porous tetrafluoropropylene copolymer resin. 8) The volatile component sampling device according to claim 6, wherein the hydrophobic porous membrane is tube-shaped. 9) Carrier gas flows down from the upper part of the inner tube of the double tube, ascends through the heat exchange section inside the outer tube from the folding point at the bottom, and is further removed from the volatile components in the hydrophobic porous membrane tube that forms part of the outer tube. 7. The volatile component sampling device according to claim 6, which performs gas sampling. 10) Let the carrier gas flow down from the upper part of the outer pipe of the double pipe,
A patent claim characterized in that gas sampling of volatile components is carried out in a hydrophobic porous membrane tube that flows down the upper heat exchange part and forms a part of the outer tube, and then ascends up the inner tube from the turning point at the bottom. A volatile component sampling device according to scope 6. 11) A portion of the inner tube of the double tube that corresponds to the hydrophobic porous membrane tube is protruded, a temperature sensor is installed inside the protrusion, and the lead wire of the temperature sensor is pulled out through the inner upper part of the inner tube to collect the volatile component gas. 11. The volatile component sampling device according to claim 10, which performs sampling and temperature measurement of the sampling section. 12) The volatile component sampling device according to claim 10, characterized in that a heater is installed inside or outside the outer tube of the double tube. 13) The volatile component sampling device according to claim 12, which uses a heater covered with a metal tube having an outer diameter of 2 mm or less.