JP4332625B2 - Standard gas generator with continuous atomizing mechanism for trace liquid - Google Patents

Description

  The present invention relates to a trace liquid continuous atomizer and a standard gas generator using the same, and in particular, a continuous mist of a trace amount solution in which an organic compound that is liquid at room temperature or a hardly volatile compound such as agricultural chemical that is solid at room temperature is dissolved. The present invention relates to a gas generator and a standard gas generator using the same.

  For pesticides suspected of endocrine disrupting effects, there is little evidence to scientifically prove their effects. In order to evaluate them scientifically, it is necessary to appropriately collect and maintain information related to actual exposure routes, exposure amounts and health effects in humans and wildlife. In recent years, many pesticides have been detected in polar regions far from the areas where pesticides are used, and interest in widespread diffusion of pesticides via the atmosphere has increased, making it necessary to clarify the dynamics via the atmosphere. Yes. For this purpose, continuous monitoring of the concentration of pesticides in the general atmospheric environment, grasping the actual state of the concentration of pesticides, analyzing concentration fluctuations and factors of variation, and examining the sampling period to obtain representative concentration data, etc. Needed.

When analyzing these pesticides in the atmosphere, the amount of the pesticides is extremely small, so various high-sensitivity analyzers are used. For quantitative or qualitative analysis using such analyzers, In order to increase the reliability of the results, a reference standard sample is required. Currently, as a method for obtaining a standard gas by generating a volatile gas from a liquid standard sample, for example, as suggested in the following Patent Documents 1 and 2,
(1) Permeation tube method (2) Diffusion tube method and the like are often used.

  In the permeation tube method (1), when a liquid sample is enclosed in a tube having a porous tube wall and placed in a constant temperature bath, and a dilution gas is circulated around it, the vaporized gas in the tube This is a method of obtaining a standard gas having a target concentration by ventilating a dilute gas at a constant flow rate. In the diffusion tube method (2), a liquid sample is enclosed in a container (diffusion tube) having a thin tube at the top, and this diffusion tube is placed in a constant temperature bath, and the tip of the thin tube is placed. When the diluting gas is circulated so as to cross, the evaporation diffusion rate of the liquid sample in the diffusion tube becomes constant, and this is a method for obtaining the target standard gas by ventilating the diluting gas at a constant flow rate.

  According to these permeation tube methods or diffusion tube methods, the permeation rate or evaporation diffusion rate of the liquid sample can be made constant by maintaining the temperature of the thermostat at a constant temperature and controlling the flow rate of the dilution gas. Therefore, a standard gas with a constant concentration can be easily generated. The permeation rate or evaporation diffusion rate in these permeation tube methods or diffusion tube methods can be measured by measuring the weight loss per unit time of the permeation tube or diffusion tube. Generating a standard gas requires a very complicated operation, and further has a drawback that the standard gas concentration cannot be monitored in real time.

  In addition, since the permeation tube method or diffusion tube method is a method for directly vaporizing a liquid sample, it can be applied to a liquid sample with a relatively high vapor pressure, but it is semi-volatile or hardly volatile. It cannot be applied to a substance or a liquid sample in which a solid sample is dissolved. In general, the degree of volatility of an organic compound is classified into four types as shown in Table 1 according to the vapor pressure at room temperature. In this specification, the degree of volatility is shown in Table 1. Follow the indicated classification.

  Among the pesticides, those having a high vapor pressure include methyl bromide, chloropicrin, cis-1,3-dichloropropene, trans-1,3-dichloropropene, methyl isothiocyanate, methyl iodide, which are used in so-called soil disinfection. There are soil smoke agents such as propargyl bromide, etc., but these vapor pressures are classified as highly volatile organic compounds or volatile organic compounds as shown in Table 2. Those having high volatility are classified into semi-volatile organic compounds such as 2,2-dichloroethenyldimethylphosphate (DDVP, insecticide) and molinate (S-ethylazepan-1-carbothioate, herbicide). However, these are rather exceptional and other pesticides are of a class with low vapor pressure, even if they are substantially semi-volatile organic compounds. It belongs to Luo nonvolatile organic compound. Therefore, since many of the substances suspected of having endocrine disrupting effects are classified from semi-volatile organic compounds to hardly volatile organic compounds, standard gas preparation methods including these substances have been established. Not.

Japanese Patent Laying-Open No. 2003-315216 (Claims, FIG. 1) Japanese Patent Laying-Open No. 2001-228062 (Claims, FIG. 2)

  In view of the problems of the prior art as described above, the present inventors are semi-volatile or hardly volatile substances, or liquid samples in which solid samples are dissolved (hereinafter, these are collectively referred to as “non-volatile substances”). As a result of various investigations on the method of adjusting the standard gas including the above)), it is difficult to directly vaporize these hardly volatile substances, so there is no other way to include them in the standard gas in the form of mist or mist. Then, the application of a nebulizer or an ultrasonic atomizer generally used as an atomizing means was examined. However, with these known atomizing means, the amount of atomization per unit time is too large, and it is difficult to obtain a standard gas with a very small concentration for measuring the concentration of agricultural chemicals in the air as it is. For example, in the case of a normal ultrasonic atomizer, if the supply amount of the liquid sample is decreased, a so-called empty state is obtained, and the oscillation characteristics of the ultrasonic vibrator are deteriorated and damaged. In addition, there is a problem that when the applied voltage is lowered and driven with a current smaller than the rated current in order to avoid deterioration and damage of the ultrasonic transducer, atomization cannot be effectively performed.

  Therefore, the present inventors have conducted various studies on means capable of atomizing a trace amount of hardly volatile substances using an ultrasonic atomizer, and as a result, effectively combined an ultrasonic vibrator and a porous member. The standard that includes a very small amount of hardly volatile substances can be effectively atomized even if the voltage applied to the ultrasonic transducer is lowered and driven at a current smaller than the rated current. The present inventors have found that gas can be obtained and have completed the present invention.

That is, the object of the present invention is to provide a standard gas by an atomization mechanism capable of continuously atomizing a liquid sample in which a hardly volatile substance such as an organic compound that is liquid at room temperature and a solid agricultural chemical is dissolved at room temperature. It is to provide a generator .

The above object of the present invention can be achieved by the following constitution. That is, the invention of the standard gas generator according to claim 1 of the present application is
An ultrasonic transducer disposed in a thermostat;
A porous member disposed on the surface of the ultrasonic transducer;
A liquid sample supply pipe having one end disposed between the ultrasonic transducer and the porous member and the other end extending outside the thermostat;
A trace liquid continuous supply device connected to the other end of the liquid sample supply pipe;
A carrier gas supply pipe connected to the thermostat;
A standard gas discharge pipe connected to the thermostat;
It is characterized by having.

  In this case, as the liquid sample supply tube, a stainless steel syringe needle or a fluororesin tube having an outer diameter of 0.1 mm and an inner diameter of about 0.02 mm or less can be used. The micro liquid sample continuous supply apparatus can use a well-known micro-syringe that can be electrically controlled. Furthermore, as the ultrasonic vibrator, a commercially available one for liquid sample atomization can be appropriately selected and used, but a small one is preferable. This ultrasonic transducer is preferably driven at a current lower than the rated current by lowering the applied voltage so as not to be damaged when a so-called empty state is obtained when no liquid sample is supplied.

In addition, the invention according to claim 2 of the present application is the standard gas generator according to claim 1, wherein the porous member is a film-like member formed of a metal member, a ceramic, or a polymer material. It is characterized by. These materials can be appropriately selected and used as long as they are not corroded by the atomized liquid sample, but in the case of metal members, those made of stainless steel, in the case of ceramic materials, alumina and zirconia materials, In the case of a polymer material, a fluororesin is preferable because it can be applied to various liquid samples. These materials can be used even in the case of a mesh or a sintered porous member.

The invention according to claim 3 of the present application is the standard gas generator according to claim 1 or 2, wherein the pore diameter of the porous member is large on the contact surface side with the ultrasonic transducer, and the opposite surface thereof. The side is small. In this case, the pore diameter of the porous member may be appropriately selected in consideration of the type of liquid sample to be atomized, the required particle diameter of the atomized particles, and the like. The smaller the hole diameter, the smaller the particle size of the resulting atomized liquid sample.

Furthermore, the invention according to claim 4 of the present application is the standard gas generator according to any one of claims 1 to 3, wherein the porous member is a porous member having an opening at the center. The ultrasonic transducer is pressed and fixed by a fixing means . The porous member may be pressed and fixed with a spring, or may be pressed and fixed by screwing a rigid fixing member.

The invention according to claim 5 of the present application is characterized in that, in the standard gas generator according to claim 1 , the carrier gas supply pipe includes air supply means and filter means.

The invention according to claim 6 of the present application is characterized in that, in the standard gas generator according to claim 1 , a heating means is provided in the exhaust pipe for the standard gas.

By providing the above configuration, the present invention has the following excellent effects. That is, according to the standard gas generator of claim 1 of the present application, the porous member is disposed on the surface of the ultrasonic vibrator, and the trace liquid continuous supply device is provided between the porous member and the ultrasonic vibrator. Since the liquid sample is supplied more continuously, even if the applied voltage to the ultrasonic transducer is reduced to a voltage that does not cause damage even if it is in a so-called empty state, it cannot be atomized in the conventional example. If the target substance is a liquid sample, it can be diluted as it is or diluted with a solvent, and if it is a solid, it can be dissolved in a suitable solvent. Various samples, not only those but also semi-volatile and hardly volatile, can be atomized easily, efficiently and continuously. The target substance is liquid by maintaining the flow rate of the liquid sample, the flow rate of the carrier gas, and the temperature of the thermostatic chamber that are continuously supplied from the micro-liquid continuous supply device supplying the liquid sample at a predetermined flow rate. In the case of a sample, it is diluted as it is or in a solvent, and in the case of a solid, it is dissolved in an appropriate solvent, so that not only a highly volatile and volatile material but also a variety of semi-volatile and hardly volatile materials can be used. A liquid sample can be easily and efficiently atomized continuously to obtain a standard gas containing an atomized liquid sample having a constant concentration. In this case, the atomized liquid sample concentration in the standard gas is uniquely determined in real time according to the flow rate of the supplied liquid sample, the flow rate of the carrier gas, and the temperature of the thermostat because the atomization efficiency is substantially close to 100%. be able to.

Further, according to the standard gas generator according to claim 2 of the present application, since the multi-hole member is a film-like light-weight and simple construction, without causing substantial change of the oscillation characteristics of the ultrasonic transducer, supplied Since a small amount of the liquid sample can be atomized continuously and efficiently, a standard gas with almost no concentration fluctuation can be obtained.

Further, according to the standard gas generator according to claim 3 of the present application, the pore size of multi-hole members, large contact surface of the ultrasonic vibrator. Thus the opposite side is smaller, Since the ultrasonic wave generated from the ultrasonic transducer converges as it proceeds from the large pore side of the porous member to the small surface side, the ultrasonic energy is efficiently supplied to the liquid sample, so the particle size is small. Since the atomized particles are obtained, the atomized particles are less likely to condense in the middle of the pipe, and a standard gas with little concentration fluctuation can be obtained.

According to the standard gas generator of claim 4 of the present application, the porous member can be easily fixed to the surface of the ultrasonic vibrator with a simple configuration, and the liquid supply pipe does not move simultaneously. Can be fixed in place. In addition, since the periphery of the porous member is pressed and fixed toward the surface of the ultrasonic transducer, the liquid sample continuously supplied through the liquid sample supply tube can be removed from the side surface of the porous member. It does not leak and can be atomized efficiently.

Moreover, according to the standard gas generator of Claim 5 of this application, cheap air can be used as carrier gas, and according to the standard gas generator of Claim 6 of this application It becomes possible to vaporize the liquid sample itself or the solvent in the vaporized liquid sample, to reduce the particle diameter of the atomized particles, and to reduce condensation of the atomized particles.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. 1 is a diagram showing an outline of the standard gas generator of the present invention, and FIG. 2 is a partially enlarged sectional view of FIG.

  As shown in FIGS. 1 and 2, the standard gas generator 10 of the present invention includes a thermostatic bath 11, an ultrasonic vibrator 12, a porous member 13, a trace liquid sample continuous supply device 14, a filter 15, and a heating device 16. Have. The thermostat 11 is preferably made of a water-repellent fluororesin at least on the inside so that the atomized liquid does not condense and adhere to the inside. The filter 15 is for filtering and purifying carrier gas such as air from an external air source (not shown) and inert gas from a gas cylinder. The filter 15 is passed through a carrier gas pipe 18 and the carrier in the thermostatic chamber 11. Connected to the gas inlet 19. Further, the inlet end of the heating device 16 is connected to the standard gas outlet 21 of the constant temperature bath 11 through the outlet pipe 20, and a standard gas having a predetermined concentration is obtained from the outlet end 22 of the heating device 16. Yes. The heating means of the heating device 16 is not shown.

  The ultrasonic transducer 12 in the thermostat 11 is placed on a fluororesin base 17 and connected to a driving device (not shown). In addition, the porous member 13 is placed on the surface of the ultrasonic transducer 12, and one end 24 of the liquid sample supply tube 23 is located at a substantially central portion between the ultrasonic transducer 12 and the porous member 13. ing. The periphery of the porous member 13 is fixed by a porous member fixing means 26 made of a fluororesin having an opening 25 at the center, and the center is pressed and fixed to the spring 27. At the boundary between the opening 25 at the center of the porous member fixing means 26 and the porous member 13, a cone-shaped member 28 made of a fluororesin having a large opening at the top is disposed. The upper end of the member 28 is fixed by an upper fixing member 29 made of a fluororesin. The porous member fixing means 26 fixes the porous member 13 and also serves as a fixing means for the liquid sample supply tube 23. Both the porous member fixing means 26 and the upper fixing member 29 are screwed (not shown). It is firmly fixed to the base 17 by such means.

  The liquid sample supply tube 23 is preferably made of stainless steel or fluororesin because it hardly reacts with various liquid samples. The pore diameter varies depending on the flow rate of the supplied liquid sample. To obtain a very low concentration standard gas for use in measuring the concentration of agricultural chemicals in the air, the outer diameter is about 0.1 mm and the inner diameter is about 0.02 mm. It is good to use the extra fine tube. If necessary, a finer tube having a thinner outer diameter or inner diameter can also be used.

  The trace liquid sample continuous supply device 14 includes, for example, a well-known syringe pump 30, and the other end of the liquid sample supply pipe 23 is connected to the discharge port 31 of the syringe pump 30. The syringe pump 30 has a feed rate controlled by a driving device (not shown), and a liquid sample is disposed at a predetermined flow rate through the liquid sample supply tube 23 in the thermostatic chamber 11 and the porous member 13. It is designed to supply during The liquid supply speed of the syringe pump 30 can be set by a combination of the size of the syringe pump to be used and the feed speed of the syringe pump 30. For example, in the case of a small-sized one that is generally commercially available, it can be set from a minimum of 0.001 μl / min to a maximum of 10 ml / min.

  As shown in FIG. 3 in an enlarged manner, the porous member 13 has a hole diameter on the surface in contact with the ultrasonic transducer 12 as L1 and an opening on the surface opposite to the ultrasonic transducer 13 as L2. , L1 >> L2. With such a configuration, since the ultrasonic wave generated from the ultrasonic vibrator 13 is converged while reaching the surface opposite to the ultrasonic vibrator, the fine atomized particles are improved in order to improve the atomization efficiency. Is obtained. These numerical values of the hole diameters L1 and L2 and the film thickness W are not critical, but for example, L1 = 50 μm, L2 = 5 μm, and W = 50 μm can be used. The material of the porous member can be selected and used as long as it is not corroded by the atomized liquid sample. However, the metal member is made of stainless steel, and the ceramic material is alumina or zirconia. However, in the case of a polymer material, a fluororesin is preferable because it can be applied to various liquid samples. These materials can be used even in the case of a mesh or a sintered porous member.

Of the standard gas generator 10, at least the ultrasonic transducer 12, the porous member 13, the liquid sample supply tube 23 having one end disposed between the ultrasonic transducer 12 and the porous member 13, and the The trace liquid sample continuous supply apparatus 14 connected to the other end of the liquid sample supply pipe 23 constitutes the trace liquid atomization apparatus A of the present invention.
Below, the specific result which measured the various characteristics of said standard gas generator 10 is shown.

  First, using the standard gas generator 10 shown in FIG. 1, the atomization characteristics of pure water having hydrogen ion binding property and large polarity and surface tension as a blank test were measured. The filter 15 is used to remove particulate matter and gaseous matter from the outside air and capture the particulate matter with reference to the results of a preliminary experiment using pesticides for the purpose of using the outside air as a carrier gas. A collection quartz fiber filter paper (PALLFLEX PRODUCTS CORP. 2500QAT-UP) was used and polyurethane foam was selected for the collection of gaseous substances. Moreover, the temperature distribution in the heating device 16 was controlled at 100 ° C., and the particle size distribution measurement of the nebulized particles of pure water contained in the standard gas obtained from the thermostat 11 was performed. A laser particle size spectrometer (manufactured by TOPAS PRODUCTS, LAP320) was used for the particle size distribution measurement.

  Initially, the rated current was supplied by using the vibrator 12 having an ultrasonic frequency of 2.4 MHz alone. However, the atomization of the trace amount liquid sample was observed to deteriorate the oscillation characteristics, and the central atomized particle diameter was 3 μm. It was large and inappropriate. Therefore, the current supplied to the ultrasonic transducer 12 is reduced below the rated current, and the porous member 13 made of alumina (L1 = 50 μm, L2 = 5 μm, W = 50 μm, see FIG. 3) is used. The surface was pressed against the surface of the ultrasonic vibrator 12 by force, and pure water was supplied between the porous member 13 and the ultrasonic vibrator 12 at a rate of 20 μl / min. It was confirmed that such a configuration can prevent the ultrasonic vibrator 12 from being damaged and obtain good atomization characteristics. The particle size distribution of the obtained atomized particles is shown in FIG. 4 together with the particle size distribution when a commercially available nebulizer is used.

  As is clear from the results shown in FIG. 4, when a commercially available nebulizer is used, the particle diameter of the atomized particles of pure water is as large as about 5 μm and has a wide particle size distribution ranging from 0 to 15 μm. However, when the standard gas generator 10 of the present invention is used, it can be confirmed that the atomized particle diameter of the pure water obtained is a fine particle or gas of 3 μm or less, and the atomization efficiency is substantial. 100%. From the results shown in FIG. 4, it was confirmed that the apparatus shown in FIG. 1 can be used as a good standard gas generator.

  The same apparatus as the standard gas generator 10 used in Example 1 was used under the same conditions, and the concentration of the NaCl aqueous solution was changed to pure water as the liquid sample, and the concentration of the NaCl aqueous solution was 0.875 mass%, 1.75 mass%, and 3.50 mass. % And the atomization characteristics were measured. The particle size distribution of the atomized particles of the obtained NaCl aqueous solution is shown in FIG.

  From the results shown in FIG. 5, in the system using the NaCl aqueous solution, NaCl is formed as a nucleus to generate a fine aerosol, and the film drop (<1 μm) has priority over the jet drop (1 to 5 μm). Was generated. The particle size distribution of the aerosol changes depending on the NaCl concentration, and this change in the particle size distribution is considered to depend on the viscosity of the solution. The atomization efficiency was substantially 100% because there was no unatomized residue. From the results shown in FIG. 5, it was confirmed that the apparatus shown in FIG. 1 can be used as a good standard gas generator.

As Example 3, it is often used as an agricultural chemical (1) thiobencalb
(2) Fentrothion
(3) fenobcarb
(4) simetryn
Using the standard gas generator used in Example 1, the atomization efficiency of the standard gas generator was measured by analyzing the obtained standard gas with an analyzer.

The set concentration of each pesticide is set to 5 levels of 0.01 μg / m ³ , 0.1 μg / m ³ , 1.0 μg / m ³ , 10 μg / m ³ and 100 μg / m ³ for collecting particulate matter. After being actually collected by a filter using a polyurethane fiber for collecting a quartz fiber filter paper (PALLFLEX PRODUCTS CORP. 2500QAT-UP) and a gaseous substance, a GC-MS (SIM mode) (gas chromatography mass spectrometer ( The concentration of the pesticide recovered using the selected ion monitor mode)) was measured. The results are shown in FIG. 6 with the horizontal axis as “set pesticide concentration” and the vertical axis as “measured pesticide concentration / set pesticide concentration”. As is clear from the description in FIG. 6, although there are slight variations depending on the type of pesticide, the “measured pesticide concentration / set pesticide concentration” shows a value substantially close to 1, and the atomization efficiency of the pesticide sample is It was confirmed that the value was substantially close to 100%.

For reference, using a low volume air sampler (Partisol Model 2000 Air Sampler, manufactured by R & P) equipped with an impactor that cuts particles with a particle size of 2.5 μm or larger FIG. 7 shows an example in which collection is performed around the surrounding area and the variation of the concentration of the pesticide in the atmosphere is measured. In FIG. 7, the suction flow rate is 16.7 L / min, the sampling time is 24 hrs, and particulate matter and gaseous matter are collected using the same filter as described above, and this filter is pretreated. It is the result of having analyzed using GC-MS (SIM mode). According to this measurement result, since it was close to the generation source, there were some which reached an air concentration of μg / m ³ or more.

  Thus, according to the standard gas generator of the present invention, it is possible to gasify (atomize) a volatile organic substance to a hardly volatile substance, and supply solution concentration, liquid feeding speed, carrier gas ( By appropriately setting the aeration rate of the dilution gas), it has become possible to easily generate a standard gas having an arbitrary concentration continuously for a long period of time. The standard gas generator of the present invention can be applied to confirmation of reliability in atmospheric analysis, study of substance dynamics in the atmospheric environment, chemical substance exposure test, and the like.

It is a figure explaining the outline of the standard gas generator of the present invention. It is a partially expanded sectional view of FIG. It is an expanded sectional view of the porous member of FIG.1 and FIG.2. It is a figure which shows the particle size distribution of the atomized pure water in Example 1, and the particle size distribution of the atomized pure water of a prior art example. 6 is a graph showing the particle size distribution of an atomized NaCl aqueous solution in Example 2. FIG. It is a figure which shows the measurement result of the agrochemical density | concentration in the standard gas containing the atomized pesticide obtained using the standard gas generator of Example 1. FIG. It is a figure showing the result of having monitored the pesticide density | concentration around Agricultural Environment Technology Laboratory paddy field.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Standard gas generator 11 Constant temperature bath 12 Ultrasonic vibrator 13 Porous member 14 Trace liquid sample continuous supply device 15 Filter 16 Heating device 17 Base 18 Carrier gas piping 19 Carrier gas inlet 20 Outlet piping 21 Standard gas outlet 22 Heating device Outlet end 23 of the liquid sample supply tube 24 one end 25 of the liquid sample supply tube 25 opening 26 of the porous member fixing means 27 porous member fixing means 27 spring 28 cone shaped member 29 upper fixing member

Claims (6)

An ultrasonic transducer disposed in a thermostat;
A porous member disposed on the surface of the ultrasonic transducer;
A liquid sample supply pipe having one end disposed between the ultrasonic transducer and the porous member and the other end extending outside the thermostat;
A trace liquid sample continuous supply device connected to the other end of the liquid sample supply pipe and supplying a liquid sample at a predetermined flow rate ;
A carrier gas supply pipe connected to the thermostat;
A standard gas discharge pipe connected to the thermostat;
A standard gas generator characterized by comprising: The standard gas generator according to claim 1 , wherein the porous member is a film member formed of a metal member, ceramics, or a polymer material. 3. The standard gas generator according to claim 1, wherein the pore diameter of the porous member is large on the contact surface side with the ultrasonic transducer and small on the opposite surface side. 4. The said porous member is pressed and fixed to the said ultrasonic transducer | vibrator by the porous member fixing means by which the opening was provided in the center part, The any one of Claims 1-3 characterized by the above-mentioned. Standard gas generator. The standard gas generator according to claim 1 , wherein the carrier gas supply pipe includes an external air supply unit and a filter unit. 2. The standard gas generator according to claim 1 , wherein the standard gas discharge pipe is provided with heating means.

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