Abstract:
An object of the present invention is to prevent a variation in heat dissipating effect of a capillary between a holder part and an oven, to improve reproducibility of migration time, and to reduce a variation of migration time among capillaries in a single electrophoresis run. A cylindrical wall is formed in an upper part of a septa that covers a container holding a solution, and the cylindrical wall surrounds a capillary hole through which a capillary penetrates. Accordingly, the capillary is prevented from being directly affected by wind generated between the septa and the oven.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese application JP 2008-31275 filed on Feb. 13, 2008, the content of which is hereby incorporated by reference into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a capillary electrophoresis device that separates and analyzes a sample, such as nucleic acid and protein, by electrophoresis. 
         [0004]    2. Description of the Related Art 
         [0005]    A solution, such as a sample, an assay, a buffer, or a rinse, which is used in a capillary electrophoresis device, is held in a container sealed by a septa. A capillary is filled with a separation medium, and the separation medium comes in contact with a liquid inside of the container through a hole formed in the septa. When a high voltage is applied to the capillary for carrying out electrophoresis, the separation medium filled inside of the capillary generates heat due to the generation of Joule heat, and the capability of separating a sample is decreased due to heat diffusion. Conventionally, in order to prevent the generation of heat in a separation medium and maintain a constant temperature of the separation medium, the capillary is put through inside of an oven having a temperature control mechanism. The technique is described in Japanese Unexamined Patent Application Publication No. 2006-276039. 
       SUMMARY OF THE INVENTION 
       [0006]    Since a holder part that stores a solution, such as an assay, a buffer and a rinse, is attached to and detached from the capillary by the use of an auto sampler, the holder part is installed outside of the oven. Meanwhile, a region between the holder part and the oven is affected by wind circulating inside of the device by a cooling fan. Accordingly, it has been revealed that, when the temperature and the speed of the wind are not uniform, reproducibility of migration time is deteriorated, and a variation of migration time among multiple capillaries in a single electrophoresis run is increased. 
         [0007]    An object of the present invention is to provide a capillary electrophoresis device in which a capillary between a holder part and an oven is not affected by air circulating inside of the device. 
         [0008]    In the present invention, it is configured so that airflow circulating inside of a device may not directly blow onto a capillary electrode that is located outside of an oven. As an example, the present invention includes: a container that houses a sample or an electrolytic solution, and has an opening in an upper part thereof, and a septa having a capillary hole through which a capillary electrode projecting from a load header penetrates, the septa covering the upper part opening of the container. The septa has in an upper part thereof a structure that surrounds the capillary electrode so that air circulating inside of the device does not directly blow onto the capillary electrode. 
         [0009]    According to the present invention, air circulating inside of the device does not directly blow onto the capillary (capillary electrode) on the side of a sample injection end; therefore, a variation of migration time among multiple capillaries and deterioration in reproducibility can be prevented. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic view of a capillary electrophoresis device. 
           [0011]      FIG. 2  is an explanatory view of a structure of a commonly-used holder part used in a capillary electrophoresis device. 
           [0012]      FIG. 3  is a view illustrating an assembly state of the holder part. 
           [0013]      FIG. 4  is a view illustrating the relationship between a capillary electrode and a conventional holder part. 
           [0014]      FIG. 5  is a view illustrating a state in which air circulating inside of the device goes by a capillary between the conventional holder part and an oven. 
           [0015]      FIG. 6  is a view illustrating an example of a result of migration of DNA fragments. 
           [0016]      FIG. 7  is a view illustrating superimposed results of electrophoresis with 16 capillaries in the case where the conventional solution holder is used. 
           [0017]      FIGS. 8A and 8B  are frame views of a septa according to the present invention. 
           [0018]      FIG. 9  is a view illustrating the relationship between capillary electrodes and the holder part of the present invention. 
           [0019]      FIG. 10  is a view illustrating the relationship between a septa provided with a cylindrical wall and an oven. 
           [0020]      FIG. 11  is a view illustrating superimposed results of electrophoresis with 16 capillaries measured by the device of the present invention. 
           [0021]      FIGS. 12A and 12B  are views illustrating another example of a septa of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]      FIG. 1  is a schematic view of a capillary electrophoresis device. A capillary electrophoresis device  100  includes: a capillary array  102  containing a single or multiple capillaries  101 ; a pump mechanism  103  for injection of a polymer to the capillary  101 ; a detector  104  that irradiates a sample inside of the capillary  101  with light and detects fluorescence from the sample; a high-voltage power supply  105  for applying a high voltage to the capillary  101 ; an oven  106  for maintaining a main part of the capillary  101  at a constant temperature; and an auto sampler  107  for transferring a container holding a sample, a solution, or the like. 
         [0023]    The capillary  101  is an exchangeable member, and is exchanged when a different measurement technique is adopted or when damage or quality deterioration is observed in the capillary  101 . The capillary  101  is composed of a glass tube having an inside diameter in a range from several tens to several hundreds of microns and an outside diameter of several hundreds of microns, and is coated on a surface thereof with polyimide. Inside of the capillary  101  is filled with a separation medium for causing migration time difference during electrophoresis. As for the separation medium, there are both a liquid medium and an illiquid medium, and a liquid polymer is used in the present example. 
         [0024]    The capillary array  102  is provided at one end thereof with a capillary head  117  arranged and at the other end with a capillary cathode electrode  118  formed. The capillary head  117  is formed by putting an end part of the capillary array  102 , and has a function to connect the pump mechanism  103  and the capillary array  102 . The capillary cathode electrode  118  is in contact with a sample, a solution, and the like. On the side of the capillary cathode electrode  118 , the capillary array  102  is fixed by a load header  115 . The load header  115  has a cathode electrode  114  and a hollow capillary electrode  120  made of metal mounted thereto. There is continuity between the cathode electrode  114  and the capillary electrode  120 . The capillary cathode electrode  118  penetrates through the capillary electrode  120  and projects from a tip thereof. 
         [0025]    The detector  104  is composed of an irradiation system and a detection system. The irradiation system of the detector  104  has a function to irradiate a part in which a polyimide coating is removed in the capillary  101 , that is a detection region, with an exciting light. The detection system has a function to detect fluorescence from a sample in the detection region of the capillary  101 . A sample is analyzed by the light detected by the detection system. 
         [0026]    The pump mechanism  103  is connected to: a syringe  108 ; a block  109 ; a check valve  110 ; a polymer container  111 ; and an anode buffer container  112 . The capillary head  117  is connected to the block  109  so as to connect the capillary  101  and a flow path inside of the block  109 . By operating the syringe  108 , polymer inside of the polymer container  111  is filled or refilled into the capillary  101  through the flow path inside of the block  109 . Refill of polymer inside of the capillary  101  is carried out for every measurement in order to improve measurement performance. 
         [0027]    An anode electrode  113  is arranged in the anode buffer container  112 . The high-voltage power supply  105  applies a high voltage between the anode electrode  113  and the cathode electrode  114 . The oven  106  maintains the temperature of the capillary  101  constant by sandwiching the capillary array  102  in a planar manner with a temperature control board installed with a heat insulating material and a heater. A temperature sensor for feedback is attached to the temperature control board. Meanwhile, by fixing the load header  115  of the capillary array  102  to the oven  106 , a tip of the capillary head  117  can be fixed at a desired position. 
         [0028]    The auto sampler  107  includes three electric motors and a linear guide for moving a motion stage, and is capable of moving the motion stage in three axial directions of up and down, left and right, and front and back. The motion stage can transfer a buffer container, a rinse container, a waste container, and a sample plate to the capillary cathode electrode  118  if required. A cooling fan  119  circulates air inside of the device in order to prevent temperature rise by a heat-generating body, such as the high-voltage power supply  105 . 
         [0029]      FIG. 2  is an exploded assembly view describing a structure of a commonly-used holder part used in a capillary electrophoresis device. The holder part includes: a container  201  for housing a solution; and a septa  202  having a capillary hole  205  through which the capillary  101  penetrates.  FIG. 3  illustrates a state in which the holder part is assembled, and illustrates a state in which multiple capillaries  101  are respectively inserted into the capillary holes  205 . An opening part of the container  201  is sealed by the septa  202  so as to prevent evaporation of the solution. The hollow capillary electrode  120  and the tip part of the capillary  101  mounted therein penetrates through the capillary hole  205  formed in the septa  202 , and is inserted into the container  201  and dipped into a solution inside of the container  201 . 
         [0030]      FIG. 4  and  FIG. 5  are views describing a problem in a holder part of a conventional capillary electrophoresis device.  FIG. 4  is a view illustrating the relationship among the hollow capillary electrodes  120  having the tip of the capillary  101  inserted thereinto, the container  201 , and the septa  202 . The upper opening of the container  201  is sealed by the septa  202 . A capillary hole of the septa  202  is provided to each of the capillary electrodes  120 . By an auto sampler, the container  201  sealed by the septa  202  is positioned below the load header  115  so that the position of the capillary holes of the septa  202  corresponds to the position of the respective capillary electrodes  120 , and then pushed upwardly. As a result, as illustrated in  FIG. 5 , the hollow capillary electrode  120  and the capillary  101  therein penetrate through the capillary hole of the septa  202 , and have the tip part thereof dipped into a solution inside of the container  201 . Then, the container  201  is mounted on the lower side of the load header  115  of the oven  106 . 
         [0031]    At this time, a space is formed between the load header  115  connected to the oven  106  and the septa  202 . This is because it is difficult to make the upper part of the container  201  stick to the load header  115  completely because the container  201  is mechanically pushed upwardly from below by the auto sampler. Meanwhile, the space is created also for an intension to provide a space, between the load header  115  and the septa  202 , into which an instrument used for pushing down the septa  202  is inserted so as to make its detachment from the capillary electrode  120  easier when the container  201  is brought down so as to be detached from the capillary electrode  120 . 
         [0032]    However, it has been revealed that, when a space is formed between the load header  115  and the septa  202  and the capillary electrode  120  is exposed, air circulating inside of the device  100  by the cooling fan  119  goes through the space, a difference in heat dissipating effect among capillaries occurs due to the temperature of the air gone through, and a variation of migration time in electrophoresis is observed. This is a phenomenon which has never been observed before. 
         [0033]      FIG. 6  illustrates a measurement example when DNA fragments were subjected to electrophoresis in a device having a structure as illustrated in  FIG. 5 , and four peaks were detected.  FIG. 7  is a view illustrating superimposed results of electrophoresis with 16 capillaries fixed to a single load header  115 , and it is observed that the data from 16 capillaries vary in a temporal axis direction. 
         [0034]    Based on the problem recognition described above, the present invention is designed with ingenuity so that, between the load header  115  and the container  201 , the capillary electrode  120  is not exposed to air circulating inside of the device. 
         [0035]      FIGS. 8A and 8B  are a frame view of a septa  401  used in an example of the present invention.  FIG. 8A  is a side view, and  FIG. 8B  is a perspective view. The septa  401  is provided with multiple cylindrical walls  402  each surrounding a capillary hole through which a capillary (capillary electrode) penetrates. The cylindrical wall  402  is in a state being integrated with the main body of the septa  401 , and is composed of a flexible silicone resin having high electric insulation properties. 
         [0036]      FIG. 9  and  FIG. 10  are views each illustrating a holder part of a capillary electrophoresis device to which measures of the present invention are applied.  FIG. 9  is a view illustrating the relationship among the capillary electrodes  120  into which tips of the capillaries  101  are inserted, the container  201 , and the septa  401 . The upper opening of the container  201  is sealed by the septa  401 . The capillary hole of the septa  401  and the cylindrical wall  402  surrounding the capillary hole are provided for each of the capillary electrodes  120 . By an auto sampler, the container  201  covered with the septa  401  is positioned below the load header  115  so that the position of the capillary holes of the septa  401  corresponds to the position of the respective capillary electrodes  120 , and then pushed upwardly. As a result, as illustrated in  FIG. 10 , the hollow capillary electrodes  120  and the capillaries  101  therein penetrate through the capillary holes each surrounded by the cylindrical walls  402  of the septa  401 , and have the tip parts thereof dipped into a solution inside of the container  201 , and then the container  201  is mounted on the lower side of the load header  115  of the oven  106 . 
         [0037]    At this time, a part, which is conventionally exposed in the space between the load header  115  and the septa and exposed to airflow circulating inside of the device, of the capillary electrode is surrounded by the cylindrical wall  402  provided in an upper part of the septa  401 , and is blocked from the airflow circulating the device. Accordingly, even if air circulating inside of the device flows into the space between the load header  115  and the septa  401 , the air does not directly blow onto the capillaries (capillary electrodes). Therefore, heat dissipation among the capillaries  101  constituting the capillary array  102  is uniform, and the migration time is stabilized. 
         [0038]      FIG. 11  is a view illustrating measurement results from when electrophoresis was carried out with 16 capillaries under the same condition as that in  FIG. 7 , using the capillary electrophoresis device using the septa  401  provided with the cylindrical walls  402 . As apprehended from the comparison between  FIG. 11  and  FIG. 7 , by using the septa  401  provided with the cylindrical walls  402 , a variation in migration time among capillaries is improved more than before. 
         [0039]      FIGS. 12A and 12B  are views each illustrating another example of a septa by the present invention.  FIG. 12A  is a side view and  FIG. 12B  is a perspective view. A septa  403  of the present example has a structure in which the whole region provided with multiple capillary holes  405  into which capillaries are to be inserted is surrounded by a cylindrical wall  404 . When a container to which the septa  403  of the present example is attached is mounted to the load header  115 , the space between the load header  115  and the septa  403  is sealed by the cylindrical wall  404 . Accordingly, even if air circulating inside of the device flows into a space between the load header  115  and the septa  404 , the air does not directly blow onto the capillaries (capillary electrodes). Therefore, heat dissipation among capillaries constituting a capillary array is uniform; thus, an effect of stabilizing the migration time can be obtained. 
       EXPLANATION OF REFERENCE NUMERALS 
       [0000]    
       
           101  . . . capillary 
           102  . . . capillary array 
           103  . . . pump mechanism 
           104  . . . detector 
           105  . . . high-voltage power source 
           106  . . . oven 
           107  . . . auto sampler 
           108  . . . syringe 
           109  . . . block 
           110  . . . check valve 
           111  . . . polymer container 
           112  . . . anode buffer container 
           113  . . . anode electrode 
           114  . . . cathode electrode 
           115  . . . load header 
           117  . . . capillary head 
           118  . . . capillary cathode electrode 
           119  . . . cooling fan 
           120  . . . capillary electrode 
           201  . . . container 
           202  . . . septa 
           205  . . . capillary hole 
           401  . . . septa 
           402  . . . cylindrical wall 
           403  . . . septa 
           404  . . . cylindrical wall