WO2016052589A1

WO2016052589A1 - Electrophoresis apparatus, electrophoresis method, and concentration/separation/analysis method using electrophoresis method

Info

Publication number: WO2016052589A1
Application number: PCT/JP2015/077677
Authority: WO
Inventors: 岸本　忠史
Original assignee: 国立大学法人大阪大学
Priority date: 2014-10-03
Filing date: 2015-09-30
Publication date: 2016-04-07
Also published as: JP2016075537A; JP6425958B2

Abstract

Provided is a concentration/separation/analysis technique with which it is possible to perform concentration and separation stably and efficiently using the MCCCE method. The present invention is an electrophoresis apparatus for concentrating/separating or analyzing ions of a substance to be concentrated/separated or analyzed by moving the ions along a migration path on which an electric field has been applied. In the electrophoresis apparatus, multiple migration paths are provided in a high thermal conductivity insulator and the electrophoresis apparatus is provided with a countercurrent-generating means for generating a flow that has a uniform speed distribution and is in the direction opposite to the ion migration direction at a speed corresponding to the ion migration speed in the solution in the migration paths. The present invention is an electrophoresis apparatus, wherein the countercurrent-generating means generates a flow that has a uniform speed distribution and is in the direction opposite to the ion migration direction at a speed corresponding to the ion migration speed by applying pulses to the solution in the migration paths for a prescribed time and at a prescribed interval.

Description

Electrophoresis apparatus, electrophoresis method and concentration / separation / analysis method using electrophoresis method

The present invention relates to an electrophoresis apparatus, an electrophoresis method, and a concentration / separation / analysis method using the electrophoresis method, in particular, an electrophoresis apparatus, electrophoresis method, and electrophoresis suitable for concentration / separation / analysis of isotope elements. The present invention relates to a concentration / separation / analysis method using electrophoresis.

In recent years, isotopes of various elements are used in various fields such as nuclear chemistry and biochemistry.

As a method for concentrating and separating isotope elements, a centrifugal separation method has been mainly used conventionally.

However, since enrichment / separation of isotope elements using this centrifugation method requires a gas containing the element to be enriched / separated, an isotope such as Ca (calcium) without a gaseous compound. It cannot be used for concentration / separation.

Thus, mass spectrometry is employed in the case of concentrating and separating isotopes from elements that do not have gaseous compounds. In this method, atoms are ionized in a vacuum, accelerated as an ion beam by an electric field, and bent and bent in a magnetic field, using the difference in curvature due to the mass difference of the isotopes to concentrate and separate isotopes. Although most elements can be concentrated, a large amount of electric power is consumed for the concentration, which is costly and very expensive. For example, ⁴⁸ Ca concentrated to 90% or more generally has a price exceeding 10 million yen per gram.

Therefore, various methods for concentrating and separating isotopes at low cost from Ca and the like in which no gaseous compound is present have been studied.

As an example, it has been studied to enrich and separate isotopes using the difference in chemical reaction rate caused by isotopes, but this method has a problem that applicable elements are limited.

However, methods other than mass spectrometry have been limited to a small amount of concentration / separation at the laboratory level, and it has not yet been possible to efficiently concentrate and separate large amounts of practical amounts.

Under such circumstances, it is possible to concentrate and separate isotopes using electrophoresis methods that have been used for separation and analysis of monoatomic ions, proteins, amino acids, etc. It attracts attention from the viewpoint of being a simple method (for example, Patent Documents 1 and 2 and Non-Patent Document 1).

This electrophoresis method utilizes the property that particles (including polymers and proteins) that are charged in a solution move when an electric field is applied to the charged particles in the solution. Is determined by the mobility inherent in the ions (ratio of electric field and velocity), so that each ion can be separated by the product of the difference in mobility and the migration distance.

However, when attempting to enrich isotopes using the conventional electrophoresis method, there were the following problems to be solved.

In other words, in electrophoresis, ions are moved by applying an electric field to the solution, but the difference in mobility between isotopes in monoatomic ions is basically small, so in order to concentrate and separate isotopes. It is necessary to apply a high electric field to increase the migration distance and to increase the difference in movement distance. However, when a large electric current is applied with a high electric field applied, a large Joule heat is generated with the energization, which may cause turbulence such as convection in the solution. Since this turbulent flow disturbs the movement of ions, even if the migration distance is increased, sufficient concentration and separation of isotopes are hindered. Moreover, since turbulence becomes larger when boiling is reached, ions cannot move.

When an electric field is applied without energization, ions move through the electric field, resulting in a charge distribution (pH gradient). This charge distribution itself forms a new electric field, and the electric field originally applied. Therefore, there is also a problem that the movement of ions stops when both electric fields are just balanced.

As a means for solving these problems, a capillary electrophoresis method in which ions are migrated in a capillary having a small diameter (capillary tube) has been proposed. Since a capillary with a small diameter is used, cooling is easy and turbulence is unlikely to occur. However, as long as a capillary with a small diameter is used, it is difficult to increase the amount of isotopes that can be separated at one time, and this is not an industrially practical means.

Therefore, it is possible to condense a large amount of isotopes at once by filling a gel, sponge, ion exchange resin, etc., and suppressing the generation of turbulent flow so that the migration part having a larger diameter has a function of suppressing turbulent flow. Is being considered.

However, even when using an electrophoresis part filled with such gel, sponge, ion exchange resin, etc., considering the generation of Joule heat, there is a limit to the voltage (current) that can be applied. It is not easy to move a long distance in a short time, and it takes a long time to fully concentrate and separate isotopes, so it is not an efficient means.

For example, Non-Patent Document 1 shows an example in which calcium isotopes are separated using an electrophoresis method in which the diameter of the migration part is increased. Here, ⁴⁸ Ca is concentrated from 0.187% of natural abundance to about 30% with respect to ⁴⁰ Ca by moving a voltage of about 1.2 V / cm for 23 m over about 900 hours.

In the above, in order to perform a large amount of migration while suppressing the temperature rise due to Joule heat, the voltage is set as low as about 1.2 V / cm and the current density is set to 0.1 to 0.2 A / cm ² (Joule heat). The temperature is suppressed to about 80 ° C. by the range of 0.1 to 0.2 W / cm ³ . However, even if turbulence is suppressed, the spread of the migration distance due to diffusion is inevitable. For this reason, in order to achieve high enrichment, it is necessary to make the difference in migration distance between isotopes sufficiently larger than the spread of migration distance due to the diffusion described above, which takes a long time of about 900 hours. The distance is migrated.

The moving speed at this time is the moving speed of metal ions (a voltage of 1 kV / cm) in a general capillary electrophoresis method in which a capillary of 0.1 mm in inner diameter is applied with a voltage of about 0.1 to 1 kV / cm to move about 1 m. 1 to 1 / 1,000 compared to 5 mm / s). Further, since the cooling water is passed around, the diameter of the entire migration part is several centimeters.

In contrast to such a conventional electrophoresis method, the present inventor concentrates and separates a large amount of isotopes by using a migration medium provided with a plurality of migration paths (hereinafter also referred to as “multi-channel”). A multi-channel counter-current electrophoresis method (MCCCE: Multi-Channel Counter Current Electrophoresis) was proposed (Patent Document 3).

This MCCCE method uses a simple electrophoresis method to efficiently concentrate, separate, and analyze a large amount of the isotopes, even if they have small mobility differences, in a short time. This is a technique developed for the first time by the present inventor as an electrophoretic method.

Specifically, the MCCCE method is an electrophoresis method that performs concentration, separation, or analysis by moving ions of a substance to be concentrated, separated, or analyzed along the migration path, and applies a high electric field. While improving the efficiency by shortening the migration distance and the time required for migration, the insulator with high thermal conductivity provided with the migration path efficiently removes the large Joule heat generated with high electric field A large number of ions are concentrated and separated by enabling effective heat removal by using many migration paths.

And in this MCCCE method, the solution is made to flow in the direction opposite to the direction in which ions move in the electric field (countercurrent). By making the counter-current velocity almost the same as the ion velocity (electrophoretic velocity), it is possible to achieve substantially long-distance migration in a short migration path and improve the efficiency of concentration, separation, and analysis. ing.

JP 2002-79059 A JP 2010-29797 A JP 2014-97463 A

According to the above-described MCCCE method, the present inventor can perform concentration / separation with much higher efficiency than the conventional method, but the high efficiency of concentration / separation by the MCCCE method may not be sufficiently exhibited, and the stability is improved. I found out there was a problem.

Therefore, an object of the present invention is to provide a concentration / separation / analysis technique that can stably perform concentration / separation with high efficiency using the MCCCE method described above.

1. MCCCE Method Developed by the Inventor Before describing the present invention, the MCCCE method developed by the present inventor as a technique related to the present invention will be specifically described.

The first technique related to the MCCCE method related to the present invention is as follows:
An electrophoresis apparatus for concentrating, separating or analyzing ions of a substance to be concentrated, separated or analyzed by moving along an electrophoresis path to which an electric field is applied,
The electrophoresis apparatus is characterized in that a plurality of the migration paths are provided in an insulator having high thermal conductivity.

The movement distance of ions is determined by velocity × time, but ions move further by diffusion and turbulence. Among these, the spread of the movement distance due to the turbulent flow can be suppressed by controlling the diameter of the migration path, but the spread due to diffusion cannot be suppressed.

For this reason, in order to efficiently concentrate and separate ions, the electric field applied in electrophoresis is increased, and the difference in travel distance between the target ion and other ions is determined by the travel distance by diffusion. It is necessary to separate them clearly so as to be larger than the spread of.

However, since the movement of ions in the migration path becomes a current, Joule heat corresponding to the power given by the product of the voltage applied to the electric field is generated. As described above, the generation of Joule heat raises the temperature of the aqueous solution and causes the generation of new turbulence in the ions. Therefore, heat is removed so that the temperature can be maintained within an appropriate range, and the generation of this turbulence is prevented. It is necessary to suppress it.

In the electrophoresis method before the MCCCE method, for example, by using an ultrafine capillary of about 0.1 mmφ as the migration path, the ion movement distance is suppressed from spreading by turbulent flow. Since this cylindrical capillary has a large surface area relative to its volume, it is possible to effectively remove heat from the surroundings. However, when removing heat, it is necessary to provide a large cooling space around the capillary. For example, in the case of a capillary having a diameter of about 0.1 mmφ, it is necessary to provide a cooling space with a diameter of several centimeters around the capillary, and the migration path itself (capillary) is disconnected from the cross-sectional area of the entire electrophoresis apparatus including the cooling space. The area ratio is as small as 10 ⁻⁴ to 10 ⁻⁵ . For this reason, it is inevitable that the arrangement of a large number of capillaries for the purpose of mass concentration, separation, and analysis cannot be applied as a practical method because the size of the electrophoresis apparatus is inevitably increased. It was.

According to the present technology, an insulator having a high thermal conductivity is employed as a medium (electrophoresis medium) for providing a migration path, and a plurality of migration paths for migrating an ionic aqueous solution are provided in the migration medium. Therefore, even if a large amount of ion aqueous solution is migrated, the generation of turbulent flow can be sufficiently suppressed, and a sufficiently large difference in travel distance can be created in a short time, improving the efficiency of concentration, separation, and analysis. It can be improved dramatically.

That is, by using a migration medium provided with a plurality of migration paths (hereinafter also referred to as “multi-channel”), a large amount of aqueous ionic solution can be migrated, so that a large amount of concentration / separation / analysis is performed. be able to.

And since an insulator with high thermal conductivity is used as the migration medium, even when a high electric field is applied to a plurality of migration paths, the generated Joule heat is efficiently removed through the migration medium with high thermal conductivity. Therefore, generation of turbulent flow can be sufficiently suppressed, and efficient concentration, separation, and analysis can be performed in a short time.

In addition, because heat can be efficiently removed in this way, the diameter of the migration path can be increased to the limit where turbulent flow is expected, and a larger amount of concentration, separation, and analysis can be performed. Can do.

As a result, as described above, the efficiency of concentration / separation / analysis can be drastically improved, and isotopes can be concentrated / separated / analyzed at low cost even in the absence of gaseous compounds such as Ca. Can be provided.

Furthermore, even if a plurality of migration paths are provided in a migration medium with high thermal conductivity, efficient heat removal is performed, so that the ratio of the cross-sectional area of the migration path to the cross-sectional area of the entire migration medium can be reduced. The electrophoresis apparatus can be made compact.

In addition, the electrophoresis apparatus according to the present technology should be used not only for concentration / separation / analysis of isotopes as described above, but also for concentration / separation / analysis of monoatomic ions, proteins, amino acids, etc., as in the past. You can also.

In the present technology, “high thermal conductivity” means that the ions can move in the aqueous solution without any trouble, specifically, the boiling point of water (100 ° C.). This means the thermal conductivity that can remove heat so that turbulent flow that affects the concentration, separation, and analysis of ions can be maintained at a temperature that does not generate in the aqueous solution. It is appropriately selected according to the diameter, interval, number and the like.

The second technique related to the MCCCE method related to the present invention is:
The electrophoretic device according to the first technique, wherein the electrophoretic medium provided with the electrophoretic path has a thermal conductivity of 30 W / mK or more.

As described above, as the migration medium in the MCCCE method, even if a plurality of migration paths are provided, the heat can be effectively removed so as to keep the temperature rise at 100 ° C. or less, and the high thermal conductivity does not cause turbulence. An electrophoretic medium made of an insulator is used, and specifically, an electrophoretic medium made of an insulator having a thermal conductivity of 30 W / mK or more, more preferably 50 W / mK or more, which is about 100 times larger than that of a normal insulator. Are preferably used. In addition, as long as it is high thermal conductivity, the upper limit of thermal conductivity is not particularly limited, but considering cost and the like, it is preferable to set the upper limit to about 300 W / mK practically.

By using a migration medium made of an insulator having such a high thermal conductivity, even if a plurality of migration paths having a diameter larger than that of a conventional capillary are provided, heat can be effectively removed so as to keep the temperature rise at 100 ° C. or less. Does not cause turbulence. Specifically, for example, the diameter can be increased to 0.5 mmφ, and the cross-sectional area can be increased to about 25 times compared to capillary electrophoresis using an ultrafine tube having a diameter of about 0.1 mmφ. The amount of electrophoresis can be dramatically increased.

Examples of such an insulating material having a high thermal conductivity, particularly an insulating material having a thermal conductivity of 50 W / mK or more, include BN, AlN, diamond, and the like.

The third technique related to the MCCCE method related to the present invention is as follows:
In the electrophoresis medium, a plurality of migration paths having a diameter of 0.5 mmφ or less are arranged at equal intervals so that the ratio of the total cross-sectional area of the migration path to the cross-sectional area of the entire migration medium is 10 ⁻² to 10 ^−1. The electrophoretic device according to the second technique, which is characterized in that:

By using an electrophoretic medium having a high thermal conductivity, as described above, an electrophoretic path having a diameter larger than that of a conventional capillary can be provided. Furthermore, by providing a plurality of such electrophoretic paths (multi-channel) Can remove heat more effectively. Specifically, the ratio of the total cross-sectional area of the migration path to the cross-sectional area of the entire migration medium is increased by 2 to 4 digits from 10 ⁻⁵ to 10 ⁻⁴ to 10 ⁻² to 10 ⁻¹ in the capillary electrophoresis method. can do. In addition, since it can be considered that the cross section of the electrophoresis apparatus is substantially occupied by the electrophoresis medium, the “cross sectional area of the entire electrophoresis medium” may be considered as the “cross sectional area of the entire electrophoresis apparatus”. When the ratio of the cross-sectional area of the entire electrophoresis medium is the same, it is preferable to provide many narrow diameter migration paths. Considering problems such as work strength, an appropriate diameter migration path is provided. It is preferable to provide it in the ratio of the cross-sectional area of the whole suitable electrophoresis medium.

As a result, a sufficient amount of electrophoresis can be performed while downsizing the apparatus. The diameter of the migration path provided and the area ratio can be set as appropriate according to the thermal conductivity of the migration medium and the shape of the migration path. The plurality of migration paths are preferably arranged at equal intervals so as not to cause heat bias in the migration medium. Further, when a plurality of migration paths are arranged at equal intervals, it is possible to easily evaluate the power that can be input.

The fourth technique related to the MCCCE method related to the present invention is:
Furthermore, the solution in the migration path is provided with countercurrent generating means for generating a flow in a direction opposite to the ion migration direction at a speed corresponding to the ion migration speed. The electrophoresis apparatus according to any one of the techniques 3 to 3.

By causing a reverse flow (countercurrent) corresponding to the ion migration speed to act on the solution in the migration path, the movement distance of ions can be suppressed. Can secure a long migration distance, and even an isotope with a small difference in migration distance can be sufficiently concentrated, separated and analyzed. In addition, the electrophoretic device can be further miniaturized.

The fifth technique related to the MCCCE method related to the present invention is as follows:
An electrophoresis method for concentrating, separating or analyzing ions of a substance to be concentrated, separated or analyzed by moving along an electrophoresis path to which an electric field is applied,
In the electrophoresis method, the ions are moved, concentrated, separated, or analyzed by applying an electric field to the plurality of migration paths provided in an insulator having high thermal conductivity.

As described above, by providing a plurality of migration paths in a migration medium having high thermal conductivity (multi-channeling), an electric field close to a general electric field used in conventional capillary electrophoresis, specifically 100 V / cm. Even when the above electric field is applied, heat can be effectively removed while sufficiently suppressing the occurrence of turbulent flow, so that a large amount of aqueous ionic solution can be efficiently concentrated, separated and analyzed in a short time.

Here, under the conditions for obtaining a constant separation, the electric field height is proportional to the inverse of the square root of the time required for concentration, separation, and analysis, and the migration distance is given by the product of the electric field height and time. By making it n times higher, the time required for concentration / separation / analysis can be shortened to 1 / n ² and the migration distance required for concentration / separation / analysis can be shortened to 1 / n. Concentration, separation, and analysis.

2. MCCCE Method According to the Present Invention The present inventor has examined the cause of the failure to perform concentration and separation stably and with high efficiency in the MCCCE method described above, and a solution to that.

Specifically, in order to find out the conditions under which concentration and separation can be performed stably and with high efficiency, the present inventor conducted a number of experiments with various combinations of experimental parameters and improved facilities and parts. And made changes.

As a result, the reason why concentration / separation could not be performed stably with high efficiency was the countercurrent generation method. It turned out that it is necessary to control.

That is, to achieve high-efficiency concentration / separation, it is necessary to suppress the velocity dispersion of ions that hinders the separation. In the conventional MCCCE method described above, it was devised that the movement distance of ions produced by the difference in mobility due to isotopes is larger than the velocity dispersion due to thermal motion of ions, but the velocity dispersion due to countercurrent becomes very large As a result, it was found that concentration and separation could not be performed stably and with high efficiency.

Specifically, since the electric field is almost uniform in the thin migration path surrounded by the insulator, the ion migration speed by the electric field is also almost uniform. For this reason, if the counter-current that cancels the ion migration speed and shortens the distance of ion movement does not flow at a constant speed, the ions that migrate will be dispersed in velocity, and can be concentrated and separated stably with high efficiency. I can't do it.

However, the liquid flow in the narrow path is usually a laminar flow called Hagen-Poiseuille flow. In this Hagen-Poiseuille flow, the velocity distribution is a quadratic function as a function of the distance from the center, so the countercurrent velocity has a large position dependency in the migration path, and countercurrent velocity dispersion occurs. To do. As a result, it was found that velocity dispersion occurred in the migrating ions, and concentration and separation could not be performed stably and with high efficiency.

In other words, there was a case where concentration / separation could be performed with high efficiency in the conventional experiment because of the influence of the countercurrent generation means used at that time. It was found that the concentration and separation could not be performed with high efficiency due to the position dependence of the countercurrent velocity when other common countercurrent generation means were used. It was.

Therefore, if the present inventor can eliminate the position dependence of the flow of the liquid in the narrow migration path, that is, the countercurrent velocity, velocity dispersion will not occur in the migrating ions, and high efficiency will be achieved. It was considered that concentration and separation could be stably achieved, and as a result of experiments, this was confirmed and the present invention was completed.

That is, the invention described in claim 1
An electrophoresis apparatus for concentrating, separating or analyzing ions of a substance to be concentrated, separated or analyzed by moving along an electrophoresis path to which an electric field is applied,
A plurality of the migration paths are provided in an insulator having high thermal conductivity,
Furthermore, countercurrent generating means is provided in the solution in the migration path for generating a flow having a uniform velocity distribution at a speed corresponding to the migration speed of the ions and in a direction opposite to the ion migration direction. This is an electrophoretic device.

And as such a countercurrent generation means, a means for adding pulsation to the countercurrent such as a tubing pump, or a part having a large diameter and a part having a small diameter are alternately formed in the electrophoresis path to wave the electrophoresis path itself. It has been found that the means for forming the shape is effective.

In other words, by providing these means, it is possible to flatten the forefront of countercurrent flowing in the migration path, so that there is no position dependence of the countercurrent velocity, and higher efficiency. Concentration / separation can be achieved. At this time, it is necessary to prevent the countercurrent from becoming turbulent.

The inventions according to claims 2 to 4 are based on the above findings,
The invention described in claim 2
The counter-current generating means pulsates the solution in the migration path at a predetermined interval for a predetermined time, so that the counter-current generating means has a speed corresponding to the ion migration speed and in a direction opposite to the ion migration direction. The electrophoretic device according to claim 1, wherein the electrophoretic device is a countercurrent generating unit that generates a flow having a uniform velocity distribution.

The invention according to claim 3
The counter-current generating means uses a tubing pump to pulsate the solution in the migration path at a predetermined interval for a predetermined time, so that the ion migration direction at a speed corresponding to the ion migration speed. 3. The electrophoretic device according to claim 2, wherein the electrophoretic device is a countercurrent generating means for generating a flow having a uniform velocity distribution in the opposite direction.

The invention according to claim 4
The countercurrent generation means alternately forms large diameter portions and small portions in the migration path and forms the migration path in a wavy shape, thereby at a speed corresponding to the migration speed of the ions, 2. The electrophoretic device according to claim 1, wherein the electrophoretic device is a countercurrent generating means for generating a flow having a uniform velocity distribution in a direction opposite to the ion migration direction.

The invention described in claim 5
An electrophoresis method for concentrating, separating or analyzing ions of a substance to be concentrated, separated or analyzed by moving along an electrophoresis path to which an electric field is applied,
By applying an electric field to the migration path provided in a plurality of insulators with high thermal conductivity, the ions are moved,
In the electrophoresis method, a flow having a uniform velocity distribution is generated in the solution in the migration path at a speed corresponding to the migration speed of the ions in a direction opposite to the migration direction of the ions.

Multiple migration paths are provided in the migration medium with high thermal conductivity (multi-channel), and there is no position dependency in the opposite direction to the ion migration direction at a speed corresponding to the ion migration speed in the migration path. By producing a flow having a uniform velocity distribution, concentration and separation can be stably performed with high efficiency.

The invention described in claim 6
6. The electrophoresis method according to claim 5, wherein the substance to be concentrated, separated or analyzed is an isotope element.

The above electrophoresis method uses a multi-channel electrophoretic medium, and furthermore, the ion electrophoretic velocity has a uniform velocity distribution due to a constant velocity countercurrent without position dependency in the electrophoretic path. A sufficient distance can be migrated in a shorter time, and even isotopes with small mobility differences can be migrated a sufficient distance in a shorter time and concentrated and separated stably and efficiently. It can be performed.

The invention described in claim 7
The isotopes is an electrophoresis method according to claim 6, characterized in that the ^{48 Ca.}

The electrophoresis method described above is an isotope that has been attracting attention in recent years because it can be stably concentrated and separated with high efficiency even if it is an isotope with a small difference in mobility. Can be preferably applied to enrichment, separation, and analysis of calcium isotopes in the absence of gaseous compounds that cannot be employed, and provides ⁴⁸ Ca in a large amount at a lower cost than separation by mass spectrometry. be able to.

The invention according to claim 8 provides:
A concentration / separation / analysis method comprising concentrating / separating / analyzing ions of a target substance using the electrophoresis method according to claim 5.

These electrophoresis methods enable stable migration and concentration with a large amount of ions in a shorter time and a stable separation with high efficiency. Can be concentrated, separated and analyzed efficiently.

According to the present invention, it is possible to provide a concentration / separation / analysis technique that can stably perform concentration / separation with high efficiency using the MCCCE method.

1 is a longitudinal sectional view schematically showing an electrophoresis apparatus according to an embodiment of the present invention. It is a top view of the electrophoresis medium of the electrophoresis apparatus concerning one embodiment of the present invention. It is a longitudinal cross-sectional view which shows typically the migration path of the electrophoresis apparatus which concerns on other embodiment of this invention. It is a figure which shows typically the electrophoresis apparatus in basic embodiment of MCCCE method.

[1] Basic embodiment of the MCCCE method Before describing the embodiment of the present invention, the basic embodiment of the MCCCE method developed by the present inventor will be specifically described.

1. Basic Embodiment of MCCCE Method (1) Configuration of Electrophoresis Device FIG. 4 is a diagram schematically showing the electrophoresis device in the basic embodiment of the MCCCE method, and (a) shows the electrophoresis device. Sectional drawing seen from the front, (b) is a front view of the electrophoresis medium provided in the said electrophoresis apparatus. In FIG. 4, 101 is a container, 102 is a migration unit, 103 is an anode plate, 104 is a cathode plate, 105 is a migration medium, 106 is a countercurrent generation unit, 107 is a migration path (channel), 108 is a multichannel unit, 109 Is an anode side stirring unit, and 110 is a cathode side stirring unit.

The container 101 is a cylindrical container having a substantially circular longitudinal section and closed at both ends, and the container 101 is filled with an aqueous solution containing ions of a substance to be concentrated, separated, and analyzed. An anode plate 103 serving as a + electrode and a cathode plate 104 serving as a − electrode are arranged at predetermined intervals with the electrophoresis medium 105 interposed therebetween. The container 101 is preferably formed using an insulator material having high thermal conductivity from the viewpoint of more effectively removing heat from the electrophoresis medium 105, but in consideration of cost and effect. Set as appropriate. In this embodiment, acrylic resin is used.

An anode side stirring unit 109 is provided between the anode plate 103 and the migration medium 105, and a cathode side stirring unit 110 is provided between the cathode plate 104 and the migration medium 105. A migration unit 102 is formed between the first and second computers 104.

As shown in FIG. 4B, the migration medium 105 is provided with a large number of migration paths 107 having a circular cross-sectional shape (multichannel), and ions move through the migration path 107. The diameter of the migration path 107 can be increased to 0.5 mmφ, and in this embodiment, as described above, the migration with respect to the cross-sectional area of the entire migration medium is considered in consideration of problems such as work strength. Although they are arranged at equal intervals so that the ratio of the total cross-sectional area of the path 107 is 0.03, it can be increased to about 0.1. In the present embodiment, a copper tube (not shown) is wound to cool the electrophoresis medium 105, and water is cooled through it.

There is no particular condition, but it is generally set to several centimeters.

The electrophoresis medium 105 is an insulating material having a high thermal conductivity, preferably a material having a thermal conductivity of 30 W / mK or higher, more preferably 50 W / mK or higher, such as BN. Since the migration medium 105 is formed using a material having such a high thermal conductivity, the same migration path 107 as that of the plurality of migration paths 107 having a diameter larger than that of capillary electrophoresis using an ultrafine tube having a diameter of about 0.1 mmφ is used. Even when a high electric field is applied, the generated Joule heat can be sufficiently removed, and the occurrence of turbulent flow in the migration path 107 is suppressed.

In addition, it is preferable that the electrophoretic device is further provided with a countercurrent generating unit 106 as shown in FIG. By providing a countercurrent generation unit 106 and causing a countercurrent (countercurrent) corresponding to the ion migration speed to act, the ion movement distance is suppressed, and a substantially long migration distance is reduced by the short-distance migration path 107. Since it can ensure, it can concentrate and isolate | separate, without enlarging an electrophoresis apparatus, and is preferable.

(2) Isotope enrichment / separation / analysis Next, isotope enrichment / separation / analysis using the above-described electrophoresis apparatus will be described.

First, the container 101 is filled with an aqueous solution containing ions of the target isotope, for example, an aqueous solution of Ca ions containing ⁴⁸ Ca.

Next, a predetermined voltage is applied between the anode plate 103 and the cathode plate 104 to form an electric field. A preferable electric field is 100 V / cm or more, which is an electric field of approximately the same level as that in capillary electrophoresis.

Such a large electric field can be applied because, as described above, the migration path 107 is provided in the migration medium 105 having a high thermal conductivity, so that the generated Joule heat can be sufficiently removed. This is because the generation of turbulent flow in the path 107 is suppressed.

By forming an electric field, cations migrate to the cathode plate 104 side and anions migrate to the anode plate 103 side in the migration path 107.

At this time, since isotopes having different masses have different moving velocities, it is possible to concentrate and separate isotopes having different masses by migrating a sufficient distance.

In the present embodiment, as described above, even when a high electric field is applied to the electrophoresis path 107 having a larger diameter compared to the conventional capillary electrophoresis method, the generated Joule heat is sufficiently removed to suppress the generation of turbulent flow. Therefore, a large amount of aqueous solution can be efficiently concentrated, separated and analyzed.

In addition, in the above, when a flow (countercurrent) opposite to the cation is applied, as indicated by an arrow in FIG. Since the substantial movement speed of the cation is very small, the length of the migration path 107 is

In contrast, the actual migration distance can be greatly extended.

As described above, since isotopes having different masses have different moving velocities, when the countercurrent velocity is set in the middle, the average velocity becomes 0, and the isotopes having a low moving velocity are shown in FIG. ), The isotopes with a fast moving speed are collected on the anode side on the left side in FIG. 4 (a), so that isotopes with different masses can be concentrated, separated, and analyzed more efficiently. Can do.

2. Next, the theoretical consideration of the electrophoresis method using the MCCCE method developed by the present inventor will be described with reference to FIG.

(1) Basic concept As described above, the concentration / separation / analysis of ions by electrophoresis is performed by applying an electric field to the migration path 107 and the difference in ion mobility is sufficient for concentration / separation / analysis. It can be achieved by migrating ions until a difference in distance is created, but in order to concentrate, separate, and analyze in large quantities in a short time, it creates a difference in travel distance greater than the spread due to diffusion, It is necessary to appropriately remove Joule heat corresponding to the electric power given by the product of the voltage.

(2) Specific Measures When a thin migration path is used, it is possible to prevent the ion movement distance from further spreading due to turbulence. Moreover, since the surface area with respect to the volume is large, heat can be effectively removed from the surroundings. However, as described above, since the effective cross-sectional area usable for electrophoresis is small, it is not suitable for the concentration (separation) of a large amount of ions.

Therefore, the present inventor pays attention to two methods: a method of increasing the efficiency of ion concentration (separation) and a method of removing generated Joule heat,
A) By providing the narrow migration path (channel) 107 in the migration medium 105 made of an insulator having a high thermal conductivity, the generation of turbulent flow is suppressed and the generated Joule heat is effectively removed.
(B) A large amount of separation is possible by performing multi-channeling in which the number of migration paths (channels) 107 is increased.
C) Optimize the shape and arrangement of each migration path (channel) 107 from the viewpoint of heat removal, and improve the separation efficiency per electric power by increasing the electric field.
Therefore, we thought that the efficiency of concentration, separation, and analysis could be dramatically improved.

Such an electrophoresis method is a multi-channel counter-current electrophoresis method (MCCCE: Multi-Channel Counter Current Electrophoresis), and the basic concept of the MCCCE method will be described below.

(3) Multi-channel countercurrent electrophoresis (a) the cross-sectional area of the basic equation loading medium 105 _{S A,} the sum of the opening cross-sectional area of the multi-channel portion 108 and _{S MC.} The voltage is applied at the electrode. At this time, the basic equations are Poisson's equation (1.1), charge conservation law (1.2), and Ohm's law (1.3) that give the relationship between charge density and potential. It is expressed as follows. V is a potential, ρ is a charge density,

Is the current density, Δ is the Laplace operator, ∇ is the Nabla differential operator, ε is the dielectric constant of the aqueous solution, and κ is the electrical conductivity of the aqueous solution (ionic aqueous solution).

(B) Actual relational expression In this embodiment, since a steady state is considered, the time differentiation is zero. Further, since the aqueous solution moving in the migration path 107 is a conductor, the charge distribution ρ is also zero. As a result, the current density in the above equation (1.2) is

It becomes. When this is applied to the boundary between the stirring unit (the anode side stirring unit 109 and the cathode side stirring unit 110) and the multichannel unit 108, the current flowing in and the current flowing out are the same.

Because

Thus, the current density in the multichannel unit 108 is expressed by the following equation (2.1). In addition, in Formula (2.1), as for a subscript, A represents a stirring part and MC represents a multichannel part.

It becomes.

Suppose that the electrical conductivity (κ) is constant regardless of the location, the electric field is similar to the current density according to Ohm's law (1.3).

There is a relationship.

The relationship between the voltage V _A of the voltage V _MC and agitating portion applied with the voltage V and multi-channel section between the electrodes, the sum of the length of the agitating portion anode side and the cathode side, i.e.,

Using

It can be expressed as. Here, the opening cross-sectional area S _MC of the multi-channel unit 108 much smaller compared to the cross-sectional area S _A of the migration path, i.e.,

Therefore, the electric field in the multichannel part 108 is sufficiently larger than that of the stirring part, that is,

It becomes. As a result, when most of the voltage is applied to the multi-channel portion 108, Joule heat is almost generated in the migration path 107.

(C) Power consumption in the migration path Power generated in the migration path 107 of the multichannel unit 108, that is, Joule heat

Is the product of current and voltage, ie

Is obtained by volume integration in the migration path 107.

It can be expressed as. In obtaining the final expression of the above expression (2.3),

and

The approximation of was used.

The electric power between the electrodes is substantially given by IV of the product of the current and the voltage between the electrodes. From the above formula (2.3), in the case of the electric power in the migration path 107 of the multichannel unit 108, it is consumed by the stirring unit. Power to be used, ie

You can see that it is only decreasing.

(D) Time required for electric field and separation (a) Electrophoretic velocity, electric field, and electric power The ion migrating electrophoretic velocity by the electric field is given by the product of mobility and electric field. The electrical conductivity of the salt solution is given by the mobility and concentration of the cation and anion.

For example, in the case of a CaCl ₂ solution, the migration speed of Ca ions is 0.59 mm / s / [100 V / cm], and the migration speed of Cl ions is 0.77 mm / s / [100 V / cm].

It is also known that even if the elements are the same, the mobility differs depending on the isotope (for example, ⁴⁰ Ca and ⁴⁸ Ca). In order to perform concentration, separation, and analysis using this small difference, long-distance electrophoresis is required.

(B) Diffusion The isotope separation efficiency by electrophoresis and the target ion separation efficiency are given in relation to diffusion. Even if there is a difference between the isotopes in the migration distance by electrophoresis, the separation efficiency will not increase unless the difference is larger than the spread of the movement distance by diffusion. Here, the diffusion reflects that ions in the solution move in a random direction by thermal motion.

The spread of the position after a certain time (t seconds) is given by a Gaussian function, and the width (σ) representing the spread is expressed by the following equation (3.1) using the diffusion coefficient D and the time t, Proportional to the square root of time.

In the case of the aforementioned CaCl ₂ solution, the diffusion coefficient of Ca ions in water is 7.9 × 10 ⁻¹⁰ [m ² / s] at room temperature. The specific value of σ is, for example, 0.039 mm for 1 second and 3.9 mm for 10000 seconds.

Actually, in addition to this, the turbulent flow in the migration path and the location dependence of the migration speed cause further diffusion, and the contribution is often not negligible, but it can be suppressed in principle by devising the device.

In order to achieve sufficient concentration, separation, and analysis, it is necessary to realize a condition in which the difference in isotope migration distance is sufficiently larger than the above-mentioned σ.

(C) Electric field and separation efficiency Since the migration distance by the electric field can be expressed by the mobility μ and the electric field E, the distance moved at time t

Can be expressed as in the following formula (3.2).

As described above, since the mobility varies depending on the isotope, for example, the difference between ⁴⁰ Ca and ⁴⁸ Ca.

Of migration distance produced by

Is sufficiently larger than the expression (3.1) indicating the spread of the distance due to diffusion, that is, if the condition of the following expression (3.3) can be satisfied, separation is possible.

When the above formula (3.3) is corrected to the relationship between the electric field and time when both sides are equal, it can be expressed as the following formula (3.4) or (3.5).

In the above formula, since D and Δμ are constants determined by the type and concentration of the solution, the electric field E is given by the reciprocal of the square root of time. That is, if the electric field is increased by n times, the time required for the separation is shortened by 1 / n ² , and the migration distance given by the product of the electric field and time in Equation (3.2) is 1 / n.

As described above, in Non-Patent Document 1, electrophoresis corresponding to 23 m is performed in 900 hours by capillary electrophoresis, and a concentration of 30% is achieved. At this time, it is presumed that the electric field was 1.2 V / cm from the migration speed of Ca.

In the case of capillary electrophoresis, an electric field of several hundreds V / cm is common. For example, when the electric field is increased 100 times, the time for obtaining the same separation is 1/10000, and the migration distance is 1/100, which is large. It is possible to improve efficiency.

However, since the electric power per unit volume given by the equation (2.3) is 10000 times proportional to the square of the voltage, it is important to control the generated Joule heat. Capillary electrophoresis removes the high Joule heat per unit volume associated with high voltage by cooling around the ultrafine tube with water, and is used for analyzing small samples. However, it is not suitable for mass concentration (separation).

(D) Electric power required for electric field and separation As described above, when the electric field (voltage per unit length) is increased n times, the electric power per unit volume / time is increased by n ² times. Since 1 / n ² and the migration distance may be 1 / n, the volume to which the electric field is applied is also approximately 1 / n. As a result, the total energy (power x time) input to concentrate, separate, and analyze a certain amount can be reduced to almost 1 / n, so that the electric field is increased under the condition that the input power is constant. It can be seen that the separation efficiency can be improved overall.

(E) power to become n ² times when the radiation and multichannel (b) power and the heat radiating electric field and n times is used as it is heating the aqueous solution becomes Joule heat. In capillary electrophoresis, this heat is removed by cooling the surroundings with cooling water, but the diameter of the capillary is as thin as about 0.1 mm for cooling, and a cooling space of several centimeters is required around it. The ratio of the cross-sectional area of the migration path in the entire cross-sectional area is as small as 10 ⁻⁴ to 10 ⁻⁵ .

In this embodiment mode, a large number of migration paths (channels) are provided in a migration medium manufactured using a substance having high thermal conductivity in order to increase the migration amount. This makes it possible to increase the ratio of the cross-sectional area of the migration path from 10 ⁻¹ to 10 ⁻² while effectively performing the cooling, as described below.

(B) Multi-channel parameters One channel length with radius r

It is thought that heat escapes from the side surface of the channel in contact with the aqueous solution. The amount of heat that moves per unit time and unit area when there is a temperature gradient, that is, the heat removal amount J [W / m ² ], is given by the following equation (4.1). Note that λ is a thermal conductivity and is a value specific to a substance, and gradT is a temperature gradient.

As mentioned above, since heat removal is performed from the side of the channel, the area is

Can be expressed as The subscript c means one channel, but the length is the same in any of the plurality of channels.

It is.

On the other hand, the power P _c generated in each channel can be obtained by multiplying the power density ρ _c in the channel by the volume, and can be expressed by the following equations (4.2) and (4.3).

Here, since the electric power (P _C ) generated in the solution in the channel is balanced with the power escaping from the side surface area (J × side area) in the steady state, J is expressed by the following equation (4.4). The relationship shown can be obtained.

From the equation (4.1), it can be seen that the amount of heat removed is proportional to λ when the temperature gradient gradT is constant. The λ of a resin tube used in capillary electrophoresis is about 0.5. However, in the electrophoresis medium used in this embodiment, for example, when BN is used, the crystal is 2000, and the sintered ceramic is also used. Since it is possible to easily obtain λ of about 50, it is possible to increase J from 100 times to several thousand times.

(C) Cooling of the multi-channel region As described above, in the capillary electrophoresis method, an ultrafine tube of about 0.1 mmφ is often used. On the other hand, since BN of the migration medium of the present embodiment is 100 times larger than that of BN, it is possible to set the power density or the radius larger than the formula (4.4) (so as not to cause turbulent flow). It becomes. Simply, the radius r can be increased in proportion to the square root of λ from the equations (4.1) and (4.4).

For example, when the thickness of the migration path (channel) is about 0.5 mmφ, the cross-sectional area increases 25 times, and the number of migration can be further increased by installing more channels (multi-channel). In this case, each channel serves as a heat source. However, since many channels are provided in the migration path medium, it can be considered that the heat sources exist uniformly.

Therefore, in the following, heat removal is evaluated when the multichannel region is circular. The multi-channel region and an inner radius R _MC, the position of the radius R _C is that in contact with the cooling system, the amount of heat escaping from the side can be expressed as the following equation (4.5). Incidentally, the power density [rho _P is obtained by dividing the total power generated in each channel by the volume of the multi-channel electrophoresis medium, it is the average power density.

Here, since the temperature gradient is only in the radial direction, equation (4.1) is

Which can be expressed as

Is integrated from r = _Rc to r = 0, the temperature T of the aqueous solution can be obtained as shown in the following equation (4.6). Incidentally, T _C is the temperature of the cooling system around.

If this T is sufficiently lower than 100 ° C., the generation of turbulent flow can be suppressed.

For example, in FIG. 4B, using an electrophoresis medium with R _MC = 2 cm, R _C = 4 cm, and λ = 63, the power density is 1.2 × 10 6 when trying to suppress the temperature rise to 50 ° C. ⁷ [W / m ³ ] (12 [W / cm ³ ]) is obtained, and 12 W can be charged per 1 cc of water. Comparing this with the power density in the case of Non-Patent Document 1, it can be seen that in Non-Patent Document 1 it is about 0.1 W per cc, and by applying the present invention, it can be seen that power can be input almost 100 times larger.

At this time, the maximum temperature gradient is 2000 ° C./m (2 ° C./mm) at the position of r = R _MC and changes by 20 ° C. at 1 cm.

In the electrophoresis medium (multi-channel medium) used here, 0.5 mmφ holes (migration paths) are provided every 2.5 mm, and the total cross-sectional area of the channel is 3.14 of the cross-sectional area of the entire electrophoresis medium. % (3.14 × 10 ⁻² ). From the viewpoint of suppressing the temperature rise, there is no problem even if the arrangement density of the migration path is increased and the total ratio of the cross-sectional areas of the channels exceeds 10 ^−1. In consideration of the above, it is preferable that the ratio of the total cross-sectional area of the channel is 10 ⁻² to 10 ⁻¹ (1 to 10%).

[2] Embodiment of the MCCCE method according to the present invention As described above, in order to achieve high-efficiency concentration / separation in the MCCCE method, a difference in mobility due to isotopes is generated from velocity dispersion due to thermal motion of ions. It is necessary to increase the moving distance of ions, and countercurrent is generated as a means for this.

However, in the conventional MCCCE method, the velocity dispersion due to counterflow becomes very large, and there are cases where concentration and separation cannot be performed stably and with high efficiency.

If the efficiency of concentration / separation is not sufficiently high as a result of the investigation, the countercurrent in the narrow migration path is a laminar flow called Hagen-Poiseuille flow, and the countercurrent velocity in the migration path is It was found that velocity dispersion occurred with a large position dependency.

Therefore, in the MCCCE method according to the present invention, countercurrent generating means for generating a flow with a uniform velocity distribution that does not become laminar flow and has no position dependency in the migration path is provided, thereby stably and highly efficiently. Concentrating and separating.

Hereinafter, embodiments of the above-described MCCCE method according to the present invention will be specifically described.

1. Electrophoresis Device The inventor newly created an electrophoretic device as shown in FIG. 1 as an electrophoretic device according to the present embodiment in conducting an experiment for carrying out the present invention. In this embodiment, ⁴⁸ Ca contained in a calcium chloride solution (CaCl ₂ solution) was concentrated using this electrophoresis apparatus.

In FIG. 1, 1 is an electrophoresis apparatus, 11 is a case, and 12 is an electrophoresis medium. In the figure, A is the inlet of the CaCl ₂ solution, B is the outlet of the CaCl ₂ solution, C is the inlet of the hydrochloric acid solution, D is the outlet of the hydrochloric acid solution, E is the cathode, F is the anode, and G is the cation. H is an exchange membrane, and H is a flow path of cooling water provided to cool the electrophoresis medium 12.

The case 11 is made of acrylic resin having an outer shape of 80 mmφ (diameter) × 130 mm (height), and the inside is formed to 40 mmφ, and the electrophoresis medium 12 is disposed. The migration medium 12 is a BN (boron nitride) plate having a thickness of 10 mm, and a total of 69 holes of 0.8 mmφ are formed at intervals of 4 mm to form each channel 13 (see FIG. 2).

In the above description, the diameter of the channel 13 is 0.8 mmφ which is slightly larger than the channel diameter (about 0.5 mmφ) of the apparatus shown in FIG. Up to about 1 mmφ can be enlarged without problems.

In addition, it is preferable that a BN plate having a thickness of about 5 mm in which a hole having a diameter of about 2 mmφ is formed at a position overlapping the channel of the electrophoresis medium 12 is stacked below the electrophoresis medium 12. Thereby, the flow of the solution in the electrophoresis medium 12 can be stabilized, and generation | occurrence | production of a turbulent flow can be prevented reliably.

Using this electrophoresis apparatus 1, first, a CaCl ₂ solution is introduced from the inlet A. Ca ions in the solution flowing in from the inflow port A migrate from the top to the bottom in the figure by an electric field formed by applying a voltage to the cathode E and the anode F. At this time, the speed at which Ca ions in the solution migrate and the speed of the solution flow (counterflow) from the bottom to the top are adjusted so as to be in a substantially balanced state.

In this way, the relative Ca ion migration speed becomes very small by generating a countercurrent that is a reverse flow at the same speed as the Ca ion migration speed to be concentrated and separated, Even with a very short migration path of 10 mm, the actual migration distance can be greatly extended.

And the Ca ion to migrate flows downward through each channel formed in the electrophoresis medium 12, and after passing through the cation exchange membrane G freely, when it reaches the cathode E, it receives electrons and becomes neutral, Ca adheres to the cathode E. The anion Cl ions generated together with Ca ions migrate toward the anode F at a very high speed due to the upward electric field and the flow of the solution.

At this time, when solutions containing isotopes having different masses such as ⁴⁸ Ca and ⁴⁰ Ca migrate, the migration speed of each isotope is different. Therefore, the countercurrent speed is set in the middle and the average migration speed is set to zero. By doing so, it is possible to collect isotopes having a low migration speed on the anode F side and to collect fast isotopes on the cathode E side. As a result, it is possible to concentrate isotope having a slow mass and a large mass, that is, ⁴⁸ Ca, concentrated on the anode F side, taken out from the outlet B, and separated.

In this embodiment, the hydrochloric acid solution is circulated from the inlet C and from the outlet D to circulate the hydrochloric acid solution. This is performed for the purpose of preventing deterioration of conduction of the cathode E accompanying the adhesion of Ca by dissolving Ca adhering to the cathode E in a hydrochloric acid solution.

As the electrophoresis medium 12 (multi-channel electrophoresis medium), as described above, a BN (boron nitride) plate that is an insulator and has high thermal conductivity is preferably used. The thermal conductivity of the BN plate used in the present embodiment is 63 [W / (mK)], which is almost 100 times higher than that of water or a general insulator.

2. Problems that can be solved by the basic mode of the MCCCE method The MCCCE method according to the present embodiment can perform concentration and separation with extremely high efficiency as in the basic mode of the MCCCE method described above. This point partially overlaps with the contents already described in the basic form of the MCCCE method described above, but will be described in detail below.

(1) Efficiency of concentration / separation / analysis As explained in the basic form of the MCCCE method described above, the MCCCE method generates a migration speed larger than the spread of ions by diffusion by applying a high electric field to the migration path. Thus, it is possible to efficiently concentrate, separate and analyze a large amount of ions. That is, efficient concentration / separation is related to the migration speed caused by the electric field applied to the migration path.

(A) Migration Speed, Electric Field, and Power Here, the migration speed of ions will be described. As described above, the ion migration speed is given by the product of mobility and electric field. In a salt solution, the mobility and concentration of cations and anions give electrical conductivity. For example, in the case of a CaCl ₂ solution, the mobility of Ca ions is 0.59 mm / s / [100 V / cm], and the mobility of Cl ions is 0.77 mm / s / [100 V / cm].

At this time, even if the elements are the same, for example, in the case of isotopes such as ⁴⁰ Ca and ⁴⁸ Ca, the mobility of each ion is small but different. Normally, electrophoresis uses this small difference in mobility to concentrate (separate) isotopes, but if the mobility is small, the isotope is concentrated and separated by increasing the migration distance. Requires long-distance migration.

(B) Diffusion As described above, the isotope enrichment efficiency by electrophoresis is determined by the relationship with the spread of ion migration distance by diffusion. For this reason, the difference in migration distance between isotopes is required to be larger than the spread of migration distance due to diffusion.

The spread of the migration distance due to diffusion can be obtained by a Gaussian function, and the width (σ) representing the spread of the migration distance is calculated using the diffusion coefficient D and time.

Can be calculated. The diffusion coefficient of Ca ions in water obtained by this equation is 7.9 × 10 ⁻¹⁰ [m ² / s] at room temperature. The specific value of the migration distance spread (σ) at this time is, for example, 0.039 mm in 1 second and 3.9 mm in 10,000 seconds.

Actually, in addition to the spread of ion migration distance due to diffusion as described above, turbulence generated in the migration path and the location dependence of the migration speed may cause further diffusion, so the effect cannot often be ignored. However, these can be suppressed in principle by devising the configuration of the apparatus. For this reason, in order to perform concentration and separation with high efficiency, it is necessary to set the electric field and power conditions so that the difference in the isotope migration distance is sufficiently larger than the value of the ion migration distance spread due to this diffusion. There is.

(C) Electric field and separation efficiency As described above, concentration / separation can be performed with high efficiency by widening the difference in migration distance between isotopes in a short time. Therefore, in this embodiment, effective concentration (separation) is performed by setting a high electric field and widening the difference in migration distance between isotopes in a short time. The mobility differs depending on the isotope. For example, the difference in mobility between ⁴⁰ Ca and ⁴⁸ Ca.

Of migration distance produced by

However, separation is possible if it is sufficiently larger than the value of the spread of ion migration distance due to diffusion. That is,

Or

It can be expressed as. From these equations, it can be seen that if the electric field is increased by n times, the time required for separation is shortened by 1 / n ² , and the migration distance given by the product of the electric field and time is 1 / n, It can be seen that the device can be made compact.

(2) Generation of Joule Heat However, as described above, since the movement of ions in the migration path becomes an electric current, Joule heat corresponding to the electric power given by the product of the voltage is generated. Since the temperature of the solution rises due to the generation of the Joule heat, it is necessary to remove the heat so that the temperature can be maintained within an appropriate range.

Since the electrophoresis apparatus according to the present embodiment uses an electrophoresis medium composed of a material having high thermal conductivity, as in the basic form of the MCCCE method described above, Joule heat generated with a high electric field is generated. Heat can be effectively removed.

(A) Electric power and heat dissipation In this embodiment, as described above, BN plate having water conductivity of 63 [W / (mK)] or almost 100 times higher than that of a general insulator is migrated. Used as a medium. At this time, when the temperature rise in the migration path (channel) formed on the BN plate is compared with the temperature rise at the center of the BN plate, the migration medium is adjusted so that the temperature rise in each channel is lower. It is preferable to be configured.

Here, the temperature distribution in the BN plate is the heat conduction equation under the boundary condition that Joule heat is uniformly generated in the solution in the channel and the temperature around the BN plate is kept constant by cooling. Can be obtained by solving In this embodiment, the temperature rise around the center of the BN plate is set to be 1.1 times the temperature rise at the center of each channel.

(B) Cooling of the multi-channel region In order to operate the electrophoretic apparatus stably, it is necessary that the temperature is sufficiently lower than 100 degrees in any part of the apparatus. If the diameter of the channel is reduced and the number of channels is increased, the area of the migration path (channel area × number of channels) is the same and the upper limit temperature is the same, so there is room for increasing the efficiency of the entire apparatus. . However, the improvement in the efficiency of the entire apparatus is only a little less than twice, and on the other hand, a high level of work accuracy is required to reduce the diameter of the channel. The same size as the basic form of the MCCCE method.

Concentration and separation can be performed with extremely high efficiency by appropriately controlling each of the conditions described above.

3. As described above, in order to achieve high-efficiency concentration / separation in the MCCCE method as described above, the movement distance of ions generated by the difference in mobility due to isotopes is greater than the velocity dispersion due to thermal motion of ions. It is necessary to make it large, and countercurrent is generated as the means.

Therefore, in this embodiment, countercurrent (uniform countercurrent) without velocity dispersion is used. Thereby, ions can migrate uniformly in the narrow channel, and high-efficiency concentration / separation can be stably achieved. This will be specifically described below.

(1) Hagen-Poiseuille flow The velocity dispersion in the counterflow is caused by the fact that the countercurrent forms a laminar flow in the narrow channel (channel). In other words, when the countercurrent constantly flows through the thin migratory path, the countercurrent that flows is a laminar flow that satisfies the boundary condition that the flow velocity is zero on the wall surface. This laminar flow is known as the Hagen-Poiseuille flow. When a migration path is provided in a cylindrical shape as in this embodiment, the velocity (ν) of the liquid (countercurrent) flowing through it is a radius from the center. As a quadratic function of r,

From this equation, it can be seen that the counterflow that has become the Hagen-Poiseuille flow has a position dependency that the flow velocity at the wall surface is 0 and the flow velocity at the center is the highest. In the above equation, the average speed is ν ₀ and the center speed is 2ν ₀ . A is the radius of the migration path.

Whether or not the countercurrent flowing through the migration path becomes such a laminar flow is characterized by the Reynolds number. Reynolds number (Re)

Given in. In the above equation, U is the countercurrent flow velocity, L is the radius of the cylindrical migration path, and ν is the kinematic viscosity coefficient. In this embodiment, when the flow velocity U is 0.6 mm / s and the radius L is 0.8 mm, the kinematic viscosity coefficient ν of water is 1 × 10 ⁻⁶ m ² / s, so the Reynolds number is 0.5. It becomes. Usually, it is said that when the Reynolds number is less than 2000, a laminar flow is generated. In the MCCCE method in which Re is smaller than 1, a laminar flow (Hagen-Poiseuille flow) always occurs.

In such a Hagen-Poiseuille flow, the dispersion σ _ν of the velocity distribution can be obtained by the following equation, and it can be seen that a velocity dispersion of 33% occurs.

This value is much larger than the difference in velocity due to the difference in mobility between isotopes, that is, a few percent of the velocity distribution of migrating ions. Therefore, in order to stably achieve high-efficiency concentration / separation. Thus, it is understood that it is necessary to generate a position-independent countercurrent (uniform countercurrent) in which the counterflow velocity dispersion is sufficiently suppressed.

And the countercurrent should not be turbulent in nature. As described above, the turbulent flow returns the ions concentrated and separated by the electric field to the mixed state again.

(2) Realization of Uniform Counterflow The present inventor has found that the following two methods can be preferably employed for the above-described method for generating a countercurrent (uniform countercurrent) having no position dependency.

(A) Formation of pulsating flow The first method is a method of forming a pulsating flow by adding pulsation to a countercurrent flow. As described above, the Hagen-Poiseuille flow appears when the Reynolds number is small and constantly flows, and generates a velocity distribution in which the center is high speed and the periphery is low speed. Therefore, by adding pulsation to the countercurrent flow to form the pulsation flow, a countercurrent flow that is not the Hagen-Poiseuille flow is formed. As a result, a velocity distribution with a high speed at the center and a low velocity at the periphery does not occur, and a countercurrent (uniform countercurrent) with a uniform velocity distribution without position dependency can be generated.

It is preferable to employ a tubing pump for liquid feeding as the means for realizing the simplest addition of such pulsation.

The inventor started an experiment using a tubing pump, but changed to a plunger pump when the concentration was three times as great as the tubing pump was used. In other words, the voltage stabilizes when the flow rate is stable, but the tubing pump digitally determines the flow rate because it is difficult to accurately reproduce the flow rate due to the change in the flow rate due to the deformation of the tube over time. It was changed to a plunger pump that can be determined and expected to be reproduced accurately.

However, when a plunger pump was used, even if the relationship between the flow rate and the voltage was set in the same manner, no significant difference appeared in the concentration, and effective concentration could not be confirmed. Specifically, as long as the plunger pump is used, the effect of improving the concentration is at most 10%, and it must be said that there is no effect when compared with a value that is three times that of the tubing pump.

Even if a tubing pump or plunger pump is used with the same relationship between the flow rate and voltage, the fact that such a large difference is generated indicates that the tubing pump has an important meaning. It was found that it is important to create intermittent pulsations with a pump.

The reason why counter-current (uniform counter-current) is generated by forming a pulsating flow using a tubing pump is that the tubing pump is a laminar flow whose center speed is faster after sending it all at once. It seems to be because it is changed to a uniform flow by waiting.

However, even when a tubing pump is used, if the pulse interval is shortened to increase the flow rate by increasing the pulsation speed, the effect of concentration is lost because it approaches a continuous flow. Specifically, the effect of concentration disappeared by increasing the speed of pulsation by 2.5 times.

As described above, since the tubing pump cannot control the average flow rate, pulsation interval, and fluctuation range independently, it is desirable to incorporate an independent pulsation system as an effective method only in a limited case.

(B) Waveform-shaped migration path The second method is a method in which the migration path itself is formed in a waved shape by alternately forming large diameter portions and small portions in the migration path. Specifically, as shown in FIG. 3, a migration path (channel) 15 in which large portions 15 a and small portions 15 b are alternately repeated in the longitudinal direction is formed on the migration medium 14.

As a specific example, each migration path is created with a 20 mm-thick BN plate by alternately repeating a hole of 0.8 mm and 2 mm diameter every 5 mm for a thickness of 20 mm. The large part and the small part form an electrophoresis path that is alternately repeated in the longitudinal direction.

In the case of this migration path 15, even when a plunger pump that creates a smooth flow is used, a concentration of 1.4 times can be obtained.

In the formation of the pulsating flow and the formation of the wavy shape of the migration path, the average flow rate of the pulsating flow solution, the pulsation interval, the fluctuation range, and the thick part for making the migration path wavy The thickness and length of each small part is related to the physical properties of the solution to be concentrated / separated so that the countercurrent flow rate is balanced with the migration speed, laminar flow is maintained, and uniform countercurrent is formed. It is determined accordingly.

Hereinafter, the present invention will be described in more detail with reference to specific examples. In this embodiment, ⁴⁸ Ca is concentrated and separated by generating a countercurrent using a tubing pump.

Using the electrophoresis apparatus shown in FIG. 1, ⁴⁸ Ca was concentrated and separated using a CaCl ₂ solution.

At this time, in order to show the effectiveness of the MCCCE method, a countercurrent flow velocity of 0.72 mm / s is applied by applying an electric field (120 V / cm) exceeding the electric field (about 100 V / cm) in capillary electrophoresis (CE). Set. This flow rate corresponds to an inflow rate of 1.5 cc / min, and this liquid feed (inflow) was performed using a tubing pump (SMP-23AS manufactured by ASONE).

Since the liquid feeding by the tubing pump is performed with a pulse of about once every 3 seconds, the countercurrent is 2.2 mm / pulse (0.72 mm / s × 3 seconds / pulse) and proceeds as a pulsating flow. However, this flow rate has an error of about 10% because it is difficult to accurately measure with a tubing pump and there is a problem of generation of bubbles, which will be described later.

Of the voltage applied between the electrodes, the voltage applied between the front and back surfaces of a 10 mm thick BN plate forms an electric field in the migration path, but approximately 80% of the voltage is BN based on the voltage of the probe in the vicinity and simple calculation. It can be estimated that it is in the migration path of the plate.

In this embodiment, the countercurrent velocity is set to be constant, and the electric field is changed to see how the electric field movement speed changes the concentration with respect to the constant countercurrent velocity. It was.

When a voltage is applied, a current is generated, and the product electric power is generated in the migration path as Joule heat. The current varies with the concentration of the solution even in the same electric field. Here, the concentration of the CaCl ₂ solution was 0.01 N (0.01 mol / liter). For example, under the condition of 170 V, the current varies with time but is typically 200 mA, and the power in the BN plate was calculated to be 27 W (= 170 V × 80% × 200 mA). Based on this, the power density was determined to be 80 W / cc since the volume of the migration path in the BN plate was 0.34 cc.

This power density indicates that if the heat is not removed, power that increases in temperature by about 20 degrees per second can be input to the migration path. In the calculation, the temperature rise in each migration path having a diameter of 0.8 mm is 5.3 degrees, and the temperature rise in a radius of 20 mm is 6 degrees. Therefore, the overall temperature rise is 11 degrees, and the migration path can be called a channel. It can be seen that this temperature rise is suppressed sufficiently low by the size of γ and the high thermal conductivity of BN.

If the number is made smaller and the number is increased, the total temperature rise in the migration path is determined by the temperature rise of BN, and the maximum power that can be input at the same upper limit temperature can be increased. However, the room for improvement is about 1.8 times that after improvement by nearly two digits, and there is little merit in making many thin migration paths that are difficult to work. As described above, the temperature increase due to the Joule heat generated in this embodiment is calculated to be about 10 degrees, so the concentration has a margin of about 5 times, but first, confirmation of the concentration is important first, so it is safe. The experiment was conducted at a concentration at which the temperature could be controlled.

It can be said that the biggest problem in operating the above electrophoresis apparatus is the generation of bubbles. Bubbles are generated at the electrode. If the bubbles block the migration path of the BN plate, the countercurrent speed changes and the relationship with the voltage is broken.

Specifically, in the upper anode F, it is considered that a gas mainly mixed with oxygen to some extent is generated, but this does not cause a problem because it escapes from the outlet B.

On the other hand, hydrogen is mainly generated at the lower cathode E. This needs to be solved because the area of the effective migration path is reduced by masking the migration path of the BN plate. Therefore, when an ion exchange membrane G was installed and a device was added to incline it to remove bubbles, the gas (bubbles) generated from the electrodes could be solved.

However, gas was also generated above and below the BN plate. In order to solve this problem, the gas dissolved in the solution was sucked with a vacuum pump. Although there was a temporary improvement, the foam could not be completely removed.

Therefore, when the apparatus was placed horizontally to remove the gas, the gas could be extracted without blocking the migration path of the BN plate. However, although the purpose of degassing could be achieved, as long as it was placed horizontally, the effect of concentration could not be confirmed. As long as it is placed vertically, the condition that the heavy solution is on the lower side always holds, but if it is placed horizontally, convection due to a difference in concentration or temperature will occur, eliminating the effect of concentration. It is thought that it has stopped.

I tried to put the device in order to remove various other gases, but what worked was an intermediate measure that tilted a little. Specifically, when the tilted BN plate is viewed from the side, the diagonal line is not inclined more than the horizontal line, and when the bubbles grow out to a certain extent, the relationship between the voltage and the countercurrent velocity is somewhat. It became stable. However, a change of about 10% was inevitable.

Table 1 shows the concentration / separation results obtained when the voltage was changed while the flow rate of 1.5 cc / m was fixed. The evaluation of the concentration is performed by measuring the isotope ratio of the solution accumulated in about 1 hour using an apparatus having a lower space of 25 cc and an upper side of 44 cc. In principle, it is thought that the concentration starts from almost the same value at first, and the concentration increases with time.

Here, the abundance ratio α (48/43) between ⁴⁸ Ca and ⁴³ Ca was measured. Although it is preferable to evaluate the ratio α (48/40) between ⁴⁸ Ca and ⁴⁰ Ca as performance for evaluating how much concentration the apparatus has achieved, in this experiment, an ICP mass spectrometer was used as a mass spectrometer. ⁴⁰ Ca is masked by ⁴⁰ Ar because argon gas is used for the ion source, and ⁴⁰ Ca cannot be measured. Therefore, in order to convert the concentration of ⁴⁸ Ca and ⁴³ Ca to the concentration of ⁴⁸ Ca and ⁴⁰ Ca,
Reference Y. Fujii, et al. , Zeitschrift for Natureshunching AA Journal of Physical Sciences, 40, 8 (1985) 843-848.
Expression showing the relationship in which the mass dependence of the degree of concentration described in is proportional to the mass difference

Table 1 shows the values of α (48/40) obtained using A ₄₃ and A ₄₈ are the abundance ratios of ⁴³ Ca and ⁴⁸ Ca, respectively.

From Table 1, it was found that a large value of 3 times the concentration was obtained in a state where the voltage and the countercurrent velocity were almost balanced. The voltage dependence is also a reasonable result because the maximum value is obtained at the point where the electrophoretic velocity by the electric field is close to the countercurrent velocity.

Since it is known that the mass dependence of the enrichment is almost proportional, when it is converted to the ratio of ⁴⁰ Ca to ⁴⁸ Ca, it becomes 6 times, which is a surprisingly large value. The enrichment obtained in a time of about 1 hour with a 10 mm thick BN plate shows great potential.

In addition, although only the result of 1.5 cc / m is shown here, the measurement is performed in many cases. Originally, the optimal voltage is determined by determining the flow rate, and the concentration is expected to be a certain value, but the actual result is not stable. This is considered to be caused by the fact that the flow rate is substantially changed by about 10% due to the bubbles blocking a part of the migration path in addition to the problem that the flow rate is not stabilized by the above-described tubing pump. However, while complete reproduction is difficult, the tendency to observe good enrichment is consistent.

Specifically, the isotope ratio (A ₄₃ / A ₄₈ ) 0.201 at 170 V shown in Table 1 is the highest so far, but the next highest isotope ratio (A ₄₃ / A ₄₈ ) Although not shown in Table 1, it is 0.26, which is a little smaller than the previous 0.201, but a high enrichment is obtained.

When the counter-current velocity is changed to 1.2 cc / m, the voltage is 150 V and an isotope ratio (A ₄₃ / A ₄₈ ) of 0.28 is obtained. There is a tendency for the voltage to drop and the degree of enrichment to decrease slightly. When this is converted into the degree of concentration, α (48/43) is 2.2 times and α (48/40) is 3.5 times.

In a recent experiment, the present inventor has obtained an isotope ratio (A ₄₃ / A ₄₈ ) of 0.139 at 210 V, although the optimization of the experimental conditions is not sufficient in the measurement with a 20 mm-thick BN plate. . This corresponds to α (48/43) corresponding to 4.4 times and α (48/40) corresponding to 10.6 times. This is the value that the inventor aimed at Ca concentration in the first stage, and it is very significant that this could be achieved by moving a small-sized apparatus as described above in about an hour.

Thus, the technology provided by the present invention is a cost-effective concentration / separation technology, not only the above-described ⁴⁸ Ca concentration / separation, but also a large amount of concentration in basic research although there is no gas compound. Can be preferably applied to the concentration and separation of ¹⁵⁰ Nd (neodymium). In addition, since it can be applied to all elements and compounds that become charged ions in solution, it can also be applied to mass concentration / separation of small amounts of elements, molecules, and polymers analyzed by electrophoresis, Furthermore, it can be applied to the concentration and separation of nuclear fuel and the selection of radioisotopes from radioactive waste.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment. Using the principle of the present invention, various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

1 Electrophoresis device 11

Case

12, 14, 105

Electrophoresis medium

13, 15, 107 Electrophoresis path (channel)
15a A portion having a large migration path 15b A portion having a small migration path 101 Container 102 Migration unit 103 Anode plate 104 Cathode plate 106 Counterflow generation unit 108 Multichannel unit 109 Anode side stirring unit 110 Cathode side stirring unit A CaCl ₂ Solution inlet B CaCl ₂ Solution outlet C Hydrochloric acid solution inlet D Hydrochloric acid solution outlet E Cathode F Anode G Cation exchange membrane H Cooling water flow path

Claims

An electrophoresis apparatus for concentrating, separating or analyzing ions of a substance to be concentrated, separated or analyzed by moving along an electrophoresis path to which an electric field is applied,
A plurality of the migration paths are provided in an insulator having high thermal conductivity,
Furthermore, countercurrent generating means is provided in the solution in the migration path for generating a flow having a uniform velocity distribution at a speed corresponding to the migration speed of the ions and in a direction opposite to the ion migration direction. An electrophoresis apparatus characterized by that.
The counter-current generating means pulsates the solution in the migration path at a predetermined interval for a predetermined time, so that the counter-current generating means has a speed corresponding to the ion migration speed and in a direction opposite to the ion migration direction. 2. The electrophoretic device according to claim 1, wherein the electrophoretic device is a countercurrent generating means for generating a flow having a uniform velocity distribution.
The counter-current generating means uses a tubing pump to pulsate the solution in the migration path at a predetermined interval for a predetermined time, so that the ion migration direction at a speed corresponding to the ion migration speed. The electrophoretic device according to claim 2, wherein the electrophoretic device is a countercurrent generating unit that generates a flow having a uniform velocity distribution in a direction opposite to that of the electrophoretic device.
The countercurrent generation means alternately forms large diameter portions and small portions in the migration path and forms the migration path in a wavy shape, thereby at a speed corresponding to the migration speed of the ions, 2. The electrophoretic device according to claim 1, wherein the electrophoretic device is countercurrent generating means for generating a flow having a uniform velocity distribution in a direction opposite to the direction of ion migration.
An electrophoresis method for concentrating, separating or analyzing ions of a substance to be concentrated, separated or analyzed by moving along an electrophoresis path to which an electric field is applied,
By applying an electric field to the migration path provided in a plurality of insulators with high thermal conductivity, the ions are moved,
An electrophoresis method, wherein a flow having a uniform velocity distribution is generated in a solution in the migration path at a speed corresponding to the migration speed of the ions in a direction opposite to a migration direction of the ions.
6. The electrophoresis method according to claim 5, wherein the substance to be concentrated, separated or analyzed is an isotope element.
The electrophoresis method according to claim 6, wherein the isotope element is 48 Ca.
A concentration / separation / analysis method comprising concentrating / separating / analyzing ions of a target substance using the electrophoresis method according to any one of claims 5 to 7.