Patent Publication Number: US-2009230045-A1

Title: Column and cartridge column using the same

Description:
TECHNICAL FIELD 
     The present invention relates to columns that are used for chromatography and cartridge columns including the same. 
     BACKGROUND ART 
     Recently, for chromatography columns, those formed using monolithic porous bodies made of, for example, porous silica have been proposed instead of powdered separation members. A column proposed as such a column is made using an inorganic porous body (separation member) formed by a sol-gel method (see, for instance, JP 6 (1994)-265534 A and JP 7 (1995)-41374 A). The columns made using monolithic inorganic porous bodies have properties such as high separation performance, small variations in separation characteristics, and excellent stability. These porous bodies can be used for high-precision analyses and high-speed DNA separation. 
     A column including a porous body around which is protected with a circular cylinder including a heat shrinkable tube and a thermoplastic resin layer is proposed as one of the columns formed using monolithic porous bodies (see JP 10 (1998)-197508 A). 
     However, in the case of a column formed using a heat shrinkable tube, when a porous body has a concave portion at the surface thereof, the concave portion cannot be filled with the heat shrinkable tube and thereby the concave portion may form a gap. Furthermore, a gap may be generated between the porous body and the heat shrinkable tube due to pressure applied in use. These gaps cannot be repaired once they are generated. They may be enlarged further or respective gaps may be joined together. When a long gap is formed, the material to be separated may pass not through not the porous body but the gap and thereby separation may not be carried out with high precision in some cases. This problem is particularly noticeable when using a plurality of columnar porous bodies arranged in series. Furthermore, inorganic porous bodies formed by the sol-gel method may include minute unevenness at the surface thereof. In that case, the above-mentioned problem also is noticeable. 
     DISCLOSURE OF INVENTION 
     The present invention is intended to provide a highly reliable column including a vitreous porous body used as a separation member, and a cartridge column including the same. 
     In order to achieve the aforementioned object, a column of the present invention is one that is used for chromatography and includes a tube and at least one columnar separation member disposed inside the tube. The separation member is a vitreous porous body, and the tube is an elastomer tube. 
     In the column of the present invention, the separation member is held with an elastomer tube having rubber-like elasticity. Accordingly, even when the separation member has an uneven surface or has variations in size, gaps can be prevented from being formed between the separation member and the elastomer tube. 
     Moreover, a cartridge column of the present invention is one that includes a column used for chromatography and a housing for holding the column. The column includes a tube and at least one columnar separation member disposed inside the tube. The separation member is a vitreous porous body, and the tube is an elastomer tube. 
     In the cartridge column of the present invention, since the elastomer tube is disposed between the separation member and the housing, the elastomer tube and the separation member are in close contact with each other. As a result, material to be separated can be prevented from passing through outside the separation member. 
     In this specification, the term “tube” embraces structures having short lengths in the central axis direction, i.e. those with ring shapes. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view showing an example of the column according to the present invention. 
         FIG. 2A  is a cross-sectional view showing an example of the elastomer tube, and  FIG. 2B  is a cross-sectional view showing an example of the separation member. 
         FIG. 3  is a cross-sectional view showing an example of the cartridge column according to the present invention. 
         FIG. 4  is an exploded perspective view showing a part of the cartridge column as shown in  FIG. 3 . 
         FIG. 5  is a cross-sectional view showing the state, in use, of the cartridge column as shown in  FIG. 3 . 
         FIG. 6A  is a top view showing another example of the column according to the present invention, and  FIG. 6B  is a cross-sectional view thereof.  FIG. 6C  is a top view showing still another example of the column according to the present invention, and  FIG. 6D  is a cross-sectional view thereof. 
         FIG. 7  is a cross-sectional view showing another example of the cartridge column according to the present invention. 
         FIG. 8A  is an exploded perspective view showing an example of the holder to be used for a cartridge column of the present invention,  FIG. 8B  is an exploded perspective view showing another example of the holder to be used for a cartridge column of the present invention, and  FIG. 8C  is a perspective view of the holder shown in  FIG. 8B  that has been assembled. 
         FIG. 9  is a cross-sectional view showing still another example of the cartridge column according to the present invention. 
         FIG. 10  is a cross-sectional view showing the shape of the elastomer tube used in Example. 
         FIGS. 11A and 11B  each are a chromatogram obtained by using a cartridge column of the present invention. 
         FIG. 12  is an exploded perspective view showing an example of the cartridge column according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention are described. In the following descriptions, the present invention may be described using specific examples but is not limited to the specific examples described below. 
     [Column] 
     The column of the present invention is one used for chromatography and includes a tube and at least one columnar separation member (a carrier for separation) disposed inside the tube. The separation member is a vitreous porous body. The tube is an elastomer tube. The elastomer tube generally has a cylindrical shape. 
     The elastomer tube is formed of a material with rubber-like elasticity. A typical example of the elastomer is rubber, and the elastomer tube can be a rubber tube. In the following description, the term “elastomer” can be read to denote “rubber”. 
     It is preferable that the elastomer tube be formed with a material having a high chemical resistance, depending on the material to be separated. 
     The elastomer tube can be formed of, for instance, fluororubber or can be formed of silicone rubber or petroleum synthetic rubber. Examples of the petroleum synthetic rubber include nitrile rubber (NBR), styrene-butadiene copolymer rubber (SBR), acrylic rubber (ACM), chloroprene rubber (CR), ethylene-propylene rubber (EP), and isobutylene-isoprene copolymer rubber (IIR). The fluorinated elastomer (for example, fluororubber) is preferable due to its high chemical resistance and heat resistance. Examples of the fluororubber include vinylidene fluoride rubber, tetrafluoroethylene-propylene rubber, and tetrafluoroethylene-perfluoromethyl vinyl ether rubber (FFKM). Another example of the fluorinated elastomer is perfluoroelastomer. Among these materials, perfluoroelastomer and FFKM are preferable due to their high chemical resistance and heat resistance. 
     When the elastomer tube is excessively thin, the properties of elastomer cannot be exhibited sufficiently. Accordingly, it is preferable that the thickness t of a part of the elastomer tube in which the separation member is housed be at least a certain thickness. In one example, the thickness t of the elastomer tube in the normal state (the state where no external force is applied) can be at least 0.1 mm (for example, at least 0.5 mm, or at least 2.5 mm in the case of an example). The thickness t can be 20 mm or less, for example. However, the upper limit of the thickness t is not particularly limited and can be in the range of 0.01 to 1 times the diameter of the separation member, for example. 
     Although the preferable hardness of the elastomer tube also depends on the thickness t of the elastomer tube, it can be in the range of A/20 to A/100 (for example, in the range of A/40 to A/90) or D/60 or lower in terms of hardness measured with the durometer-type hardness tester (JIS-K-6253), for example. 
     An example of the elastomer tube has a thickness tin the range of 2 mm to 4 mm and a hardness (JIS-K-6253) in the range of A/50 to A/80. 
     The elastomer tube needs to have a high elasticity. It therefore is not possible to use tubes formed of resins with no rubber-like elasticity, such as Teflon (registered trademark) and polyetheretherketone (PEEK). 
     The column of the present invention can be monolithic in such a manner that the separation member and the elastomer tube cannot be detached. In this case, the length of the separation member and that of the elastomer tube generally are set to be substantially equal to each other. This column can be formed by applying liquid elastomer to the outer periphery of the separation member and then curing it, for example. Examples of typical liquid elastomer include fluorinated rubber and silicone rubber. 
     In the column of the present invention, the separation member can be disposed detachably inside the elastomer tube. When the separation member is detachable, the separation ability of the column can be set freely by arbitrarily changing the type or number of the separation members to be disposed inside the elastomer tube. Furthermore, when the performance of the separation member has deteriorated due to use, it is possible to replace the separation member alone. When the number of the separation members is to be decreased, a cylindrical spacer can be disposed inside the elastomer tube in place of the separation member. 
     The column of the present invention can have a configuration in which a plurality of separation members can be disposed inside one elastomer tube. In this case, the length of one separation member (the length in the central axis direction of a columnar separation member) generally is at most half the length of the elastomer tube (the length in the central axis direction of the tube). The number of separation members that can be disposed inside one elastomer tube can be, for example, at least two, at least three, or at least four. The upper limit thereof is not particularly determined but it can be ten or less or five or less. When a plurality of separation members are disposed inside a column, all the separation members can be vitreous porous bodies or separation members other than vitreous porous bodies can be included. 
     Furthermore, it also is possible to employ a configuration in which only one separation member can be disposed inside one elastomer tube. In this case, the length of the separation member generally is more than 0.5 times but not more than 1 times the length of the elastomer tube. 
     The separation member of the column according to the present invention is different from powdered separation members and is a monolithic separation member having a columnar shape (including a disk shape). A typical shape of the separation member is a cylindrical column whose cross-sectional shape is a perfect circle. In the separation member, however, the cross-sectional shape does not need to be a perfect circle and the end face does not need to be a planar surface. For instance, the end face can be a curved surface. Moreover, the cross-sectional shape of the separation member according to the present invention can be a rounded shape obtained by rounding the corners of a quadrangle. 
     In another aspect, the column of the present invention includes a separation member with a pillar shape (including a disc shape) and an elastomer tube that houses the separation member. This elastomer tube is provided with a through hole for housing the separation member, and the cross-sectional shape of the through hole is identical to that of the separation member or a circular shape. 
     The separation member is a vitreous porous body (substantially an inorganic porous body, including, for example, glass and glass ceramics). It can be a vitreous porous body formed using the sol-gel method, specifically a porous gel obtained by using the sol-gel method or a porous body obtained by heat-treating the gel. For instance, a vitreous porous body can be used that is formed by a known sol-gel method using metal alkoxide (for example, alkoxysilane) or metal halide as a starting material. The separation member also can be a vitreous porous body that contains an organic component and can be formed using, as one of the starting materials, metal halide or metal alkoxide including an organic group bonded thereto. 
     This vitreous porous body can have a modified surface so as to have improved separation ability. For example, a functional group or an organic molecule can be bonded to the surface of the vitreous porous body (including the case where an organic molecule with a functional group is bonded). The functional group or the organic molecule for modifying the surface of the vitreous porous body can be selected according to the separation ability to be required. For them, known groups or molecules that are used for separation members can be used including, for example, a hexyl group, an octyl group, other alkyl groups, octadecylsilane, an octadecyl group, a phenyl group, a trimethylsilyl group, a cyano group, and an amino group. 
     A typical example of the vitreous porous body is a porous body whose main component (at least 50 mass %) is silicon oxide, for example, porous silica glass. However, it also can be a vitreous porous body (inorganic porous body) containing an oxide other than silicon oxide or a vitreous porous body (inorganic porous body) whose main component is an oxide other than silicon oxide. The monolithic gel (vitreous porous body) formed by the sol-gel method is preferable because it allows the porosity or pore diameter to be controlled relatively easily and has small variations in separation ability. 
     The separation member to be used can be a commercially available vitreous porous body. It also can be formed by using a known sol-gel method. For instance, it can be formed by the methods described in JP 6 (1994)-265534 A and JP 7 (1995)-41374 A. These methods allow columnar porous silica glass (porous silica gel) to be formed. 
     The separation member to be used can be one including both through holes with relatively large diameters and fine pores with small pore diameters. For instance, it can be a vitreous porous body that can be produced by the production method described in JP 6 (1994)-265534 A, specifically a vitreous porous body including a number of through holes with diameters of 500 nm to several tens of micrometers (for example, 30 μm) and a number of fine pores with diameters of 5 nm to 100 nm. The total volume of the fine pores of this vitreous porous body is in the range of, for example, 0.001 m 3 /kg to 0.01 m 3 /kg (1 m 3 /t to 10 m 3 /t). 
     The separation ability of the vitreous porous body (separation member) varies depending on, for example, the diameter of the pores, porosity, and specific surface area of the porous body. Accordingly, those values are controlled depending on the separation ability to be required. They can be controlled by changing the conditions for producing the porous body, particularly the conditions employed in the sol-gel method. 
     [Example of Column] 
     A column in which a plurality of separation members are disposed detachably inside an elastomer tube is described as an example of the column according to the present invention. 
       FIG. 1  shows a cross-sectional view of an example of the column according to the present invention. A column  10  shown in  FIG. 1  includes an elastomer tube  11  and three columnar separation members  12  disposed inside the elastomer tube  11 . The separation members  12  are pressed into the through hole of the elastomer tube  11  to be disposed inside the elastomer tube  11 . Therefore the separation members  12  can be removed easily from the elastomer tube  11 . The cross-sectional view of the elastomer tube  11  is shown in  FIG. 2A  and that of a separation member  12  is shown in  FIG. 2B . 
     The example shown in  FIG. 1  is an example in which three separation members  12  are disposed inside the elastomer tube  11 , but the present invention is not limited thereto. The number of the separation members  12  to be disposed inside the elastomer tube  11  can be one or two or more. The separation ability of the column can be varied by changing the number of the separation members  12  to be disposed inside the elastomer tube  11 . The elastomer tube  11  can be varied in length according to the number of the separation members  12  to be used. Furthermore, when the elastomer tube is too long with respect to the total length of the separation members  12 , a cylindrical spacer can be disposed inside the elastomer tube  11 . 
     When a plurality of separation members  12  are disposed inside the elastomer tube  11 , the separation members  12  to be disposed can be of the same type, or a plurality of types with different separation abilities. The column of the present invention is different from the conventional columns, in which separation members are held by a heat shrinkable tube, in that users can select the number and type of the separation members  12  easily according to the intended use. In the column of the present invention, however, the elastomer tube  11  and the separation members  12  can be fixed to each other beforehand. 
       FIG. 1  shows the elastomer tube  11  with a through hole having a uniform diameter, but the through hole does not need to have a uniform diameter. For example, the through hole of the elastomer tube  11  can be formed of a combination of a through hole for housing the separation members  12  and a smaller through hole for not housing the separation members  12  but passing material to be separated therethrough (see  FIG. 10 ). 
     The sum of the lengths L 2  of the separation members  12  (see  FIG. 2B ) generally is shorter than the length L 1  of the elastomer tube  11  in the normal state. For instance, when three separation members  12  are disposed inside an elastomer tube  11 , the length L 1  is longer than three times the length L 2 . For example, the length of the elastomer tube  11  can be longer by 0 mm to 5 mm (in an example, 0.2 mm to 4 mm) than the sum of the lengths of the separation members  12 . When the length of the through hole for housing the separation members  12  is set to be longer than the sum of the lengths of the separation members  12 , the whole body of the separation members  12  is disposed inside the through hole of the elastomer tube  11 . That is, the end faces of the separation members  12  are disposed on the inner sides of the through hole of the elastomer tube  11  with respect to the end faces of the elastomer tube  11 . 
     In the elastomer tube  11 , the inner diameter d 1  (mm) of the part where the separation members  12  are housed is approximately identical to the diameter D 2  (mm) of the separation members  12  (see  FIGS. 2A and 2B ). Generally, a relationship (d 1 −1.0)≦D 2 ≦(d 1 +1.0) holds, for example, (d 1 −0.3)≦D 2 ≦(d 1 +0.3), and for instance, (d 1 −0.1)≦D 2 ≦d 1 . 
     In the case of D 2 &gt;d 1 , the separation members  12  can be placed inside the elastomer tube  11 , with the through hole of the elastomer tube  11  being stretched. In this case, by merely placing the separation members  12  inside the elastomer tube  11 , the outer peripheral surfaces of the separation members  12  can be in close contact with the inner peripheral surface of the elastomer tube  11 . 
     On the other hand, in the case of D 2 &lt;d 1 , it becomes easy to place the separation members  12  inside the elastomer tube  11 . Since a tube with rubber-like elasticity is used for the column of the present invention, the thickness t of the tube can be increased and the inner diameter d 1  of the elastomer tube  11  can be reduced by compressing the tube inside the housing to be described later. Accordingly, even in the case of D 2 &lt;d 1  in the normal state, the outer peripheral surfaces of the separation members  12  and the inner peripheral surface of the elastomer tube  11  can be brought into close contact with each other inside the housing. 
     [Cartridge Column] 
     Hereinafter, a cartridge column of the present invention is described. The cartridge column of the present invention includes a column that is used for chromatography and a housing for holding the column. The column is that of the present invention described in this specification. As described above, the column includes a tube and at least one columnar separation member disposed inside the tube. The separation member is a vitreous porous body, and the tube is an elastomer tube. 
     In the cartridge column of the present invention, the separation member is held with a tube having rubber-like elasticity. Accordingly, even when the separation member has a concave portion at the surface thereof, the concave portion can be prevented from forming a gap. Furthermore, even when a gap is formed between the elastomer tube and the separation member due to high pressure applied to the column when chromatography is carried out, the gap is reduced in size due to the rubber elasticity. Accordingly, the cartridge column of the present invention can particularly prevent the material to be separated from leaking through a gap present around the separation member. 
     The material used for the housing is not particularly limited and the housing can be formed of a material with suitable strength. The housing can be formed of, for example, a material with an R scale of at least 15 in terms of Rockwell hardness (ASTMD785). Examples of the material for the housing include nylon, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyester, polyphenylene oxide (PPO), acryl, polypropylene (PP), ABS resin, polyetheretherketone (PEEK), fluororesin, silicone resin, and resins containing various fillers mixed therein. A part or the whole of the housing can be formed of metal. 
     In the cartridge column of the present invention, the housing can hold the column while pressing the two end faces of the elastomer tube. This can prevent a gap from being formed between the elastomer tube and the separation member. Furthermore, the housing can hold the column while pressing the two end faces and outer peripheral surface of the elastomer tube. 
     In the cartridge column of the present invention, the elastomer tube can be compressed in the direction of the central axis thereof in the housing. The elastomer tube compressed in the direction of the central axis has a smaller inner diameter than that in the normal state. As a result, a closer contact between the tube and the separation member is achieved. The compressible length of the elastomer tube in the housing can be 0.1% to 50% (for example, 1.5% to 25%) of the length of the elastomer tube in the normal state. 
     In the cartridge column of the present invention, the sum of the lengths of the separation members (lengths in the central axis direction of the separation members) disposed inside the elastomer tube can be shorter than the length of the elastomer tube (the length in the central axis direction of the elastomer tube). In this configuration, it is possible to reduce the inner diameter of the elastomer tube by compressing the elastomer tube in the central axis direction thereof. The length obtained by subtracting the sum of the lengths of the separation members disposed inside the elastomer tube from the length of the elastomer tube can be 0.1% to 50% (for instance, 1.5% to 25%) of the length of the elastomer tube in the normal state. 
     Even if the sum of the lengths of the separation members is longer than the length of the elastomer tube, when the end faces alone of the elastomer tube can be pressed by, for example, using O-rings or using a suitable shape of the housing, it is possible to compress the elastomer tube. 
     In the cartridge column of the present invention, the housing can include a holding member in which a columnar hole into which a tube fits is formed, and a pressing surface that presses the end faces of the tube protruding from the holding member against the holding member side. The depth of the columnar hole is less than the length of the tube. 
     In the cartridge column of the present invention, a plurality of columns can be disposed inside the housing. 
     In the cartridge column of the present invention, the housing can include a cylindrical holder in which the column is disposed and the holder can be divided. The use of a holder that can be divided in the longitudinal direction allows a column (elastomer tube) to be disposed easily inside the holder even when the column is long. 
     In the cartridge column of the present invention, the housing can include pressing members that can move to press the end faces of the elastomer tube, and the pressing members can move without rotating with respect to the end faces of the elastomer tube. Since the pressing members are provided so as to be able to move without rotating with respect to the end faces of the elastomer tube, the elastomer tube is not rotated to be twisted when the column is placed inside the housing. Therefore the separation members disposed inside the elastomer tube can be prevented from being damaged. In such a configuration, for example, the housing further can include a rotation preventing means for preventing the pressing members from rotating with respect to the end faces of the elastomer tube when the pressing members are moved. For instance, when the housing includes a holder for housing a column inside thereof, the rotation preventing means can be formed of an engaging part provided for each pressing member and an engaging part provided for the holder. When the configuration in which the engaging part of the pressing member and that of the holder are engaged with each other is employed, it prevents the pressing members from rotating with respect to the holder and therefore the pressing members can move without rotating with respect to the elastomer tube. 
     [Example of Cartridge Column] 
       FIG. 3  shows a cross-sectional view of an example of the cartridge column according to the present invention. A cartridge column  30  shown in  FIG. 3  includes a column  10  and a housing  40 . The column  10  is the one shown in  FIG. 1 . The housing  40  includes a holder  41 , two caps  42 , and filters  43 .  FIG. 4  shows a perspective view of the cap  42 , separation members  12 , an elastomer tube  11 , and the holder  41 . The filters  43  are used for removing impurities such as suspended matters. The filters  43  can be omitted depending on the conditions. 
     Generally, the holder  41  and caps  42  each are formed of a hard material such as metal or resin (for instance, fluororesin). The holder  41  has a cylindrical shape and is provided with a thread groove formed at its inner peripheral surface. 
     The caps (holding members)  42  each are provided with a columnar portion  42   a  with a thread formed to engage with the thread groove of the holder  41 . The columnar portion  42   a  has a columnar hole  42   h  formed therein. The filters  43  each is disposed on the bottom surface  42   b  of the columnar hole  42   h . Furthermore, an O-ring can be disposed around the filter  43 . An O-ring that is used often is formed of resin with high chemical resistance, such as fluororesin and silicone resin. 
     The elastomer tube  11  of the column  10  is fitted into the hole  42   h . The bottom surface  42   b  (including the surface of the filter  43 ) of the hole  42   h  serves as a pressing surface for pressing the end face  11   e  of the elastomer tube  11  toward the middle of the elastomer tube  11 . In other words, in this example, one of the two caps  42  serves as the holding member and the bottom surface  42   b  of the hole  42   h  provided for the other cap serves as the pressing surface. Moreover, the side wall  42   s  of the hole  42   h  serves as a surface for pressing the outer peripheral surface  11   p  of the elastomer tube  11 . 
     Furthermore, the cap  42  includes a feed port  42   e  formed therein, through which material to be separated is fed. In the feed port  42   e , a thread groove is formed. The material to be separated reaches the separation member  12  through the filter  43  from the feed port  42   e.    
     The inner diameter Dh (mm) of the hole  42   h  is approximately equal to the outer diameter D 1  of the elastomer tube  11  in the normal state (see  FIG. 2A ). Generally, the relationship Dh−2.0≦D 1 ≦Dh+2.0 holds, for example, the relationship Dh−1.0≦D 1 &lt;Dh holds. Even if the relationship D 1 &lt;Dh holds in the normal state, the thickness t of the elastomer tube  11  increases in use and therefore the outer diameter D 1  of the elastomer tube  11  increases to allow the outer peripheral surface of the elastomer tube  11  to be in close contact with the side wall of the hole  42   h.    
     In the cartridge column  30 , the distance between the two pressing surfaces (bottom surfaces  42   b ) that press the two end faces of the elastomer tube  11  is set to be shorter than the length L 1  of the elastomer tube  11 , so that the elastomer tube  11  is compressed. Accordingly, the cartridge column  30  is configured so that the distance between the two pressing surfaces can be set to be shorter than the length L 1 . 
     In the cartridge column  30  shown in  FIG. 3 , the depth Lh (mm) of the hole  42   h  is less than the half the length L 1  (mm) of the elastomer tube  11 . For example, the relationship 2Lh−5.0≦L 1 &lt;2Lh may hold. In the case where the depth Lh is less than the half the length L 1 , when the caps  42  are screwed into the holder  41  and thereby the distance between the bottom surfaces of the holes  42   h  of the two caps  42  becomes equal to the length L 1 , a gap is present between the two caps  42  (see  FIG. 5 ). When the caps  42  further are screwed into the holder  41  so as to reduce the gap, the length L 1  of the elastomer tube  11  is reduced and the thickness t is increased. Therefore as the caps  42  are screwed into the holder  41 , the wall surfaces of the holes  42   h  and the outer peripheral surface of the elastomer tube  11  as well as the inner peripheral surface of the elastomer tube  11  and the outer peripheral surfaces of the separation members  12  are brought into close contact with each other with strong force, respectively. Similarly, the bottom surfaces  42   b  of the holes  42   h  and the end faces  11   e  of the elastomer tube  11  also are brought into close contact with each other with strong force, respectively. As described above, in the cartridge column of the present invention, the caps  42  are screwed into the holder  41  and thereby the material to be separated can be prevented from passing through, for example, between the elastomer tube  11  and the separation members  12 . 
     The housing  40  does not need to hold the whole outer peripheral surface of the elastomer tube  11  but can hold a part thereof. For instance, as shown in  FIG. 5 , there is no problem even when the part of the outer peripheral surface located in the middle of the elastomer tube  11  is not held. 
     The method of shortening the distance between the two pressing surfaces that press the two end faces of the elastomer tube  11  is not particularly limited. The housing used for the cartridge column of the present invention can have various shapes and configurations, as long as it has a configuration that allows the column to be held while pressing the two end faces (preferably, also the outer peripheral surface) of the elastomer tube. For instance, the elastomer tube  11  can be compressed with one cap  42  alone, with one end of the holder  41  serving as a pressing surface having a through hole formed therein. 
     [Other Examples of Column and Cartridge Column] 
     Hereinafter, an example of the column in which only one separation member is disposed detachably inside one elastomer tube is described as a column of the present invention.  FIG. 6A  shows a top view of the example of the column and  FIG. 6B  shows a cross-sectional view at line VIb-VIb shown in  FIG. 6A . 
     A column  10   a  shown in  FIG. 6A  includes an elastomer tube  11  and a separation member  12  disposed in the elastomer tube  11 . The elastomer tube  11  and the separation member  12  are identical to those described above. In this example, however, the length L 1  (see  FIG. 2A ) of the elastomer tube  11  is approximately equal to the length L 2  (see  FIG. 2B ) of the separation member  12  or is slightly longer than the length L 2 . 
       FIG. 7  shows an exploded cross-sectional view of an example of the cartridge column formed using the column  10   a . A cartridge column  70  shown in  FIG. 7  includes a column  10   a  and a housing for holding the column  10   a . The housing is provided with a cylindrical holder  71 , two caps  72  that are screwed into ends of the holder  71 , and two O-rings  73 . At least one column  10   a  is disposed inside the holder  71 . At least one column  10   a  and at least one spacer can be disposed inside the holder  71 . In this case, the outer diameter of the spacer is approximately equal to the outer diameter of the elastomer tube  11 , and a through hole is formed in the center portion of the spacer. 
     The holder  71  has a thread groove formed at its inner peripheral surface. The inner diameter of the holder  71  is approximately equal to or slightly larger than the outer diameter of the column  10   a.    
     Each cap  72  has a through hole  72   h  formed to pass material to be separated. The cap  72  is provided with a columnar portion  72   a  with a thread formed to engage with the thread groove of the holder  71 . An annular groove where the O-ring  73  is to be disposed is formed at the end face of each columnar portion  72   a . The O-ring  73  and the end face  11   e  of the elastomer tube  11  are in contact with each other through the annular portion having a diameter that is at least the inner diameter d 1  but is not larger than the outer diameter D 1  of the elastomer tube  11 . Accordingly, when the caps  72  are screwed into the holder  71  to allow the O-rings  73  to press the two end faces  11   e  of the elastomer tube  11 , material to be separated can be prevented from leaking at the place of the O-rings  73  and between adjacent elastomer tubes  11 . 
     The volume of the region (for example, the through hole  72   h ) where materials to be separated pass through without being separated in each cap is preferably as small as possible. Generally, the diameter of the through hole  72   h  is 0.1 mm to 1.0 mm (for example, 0.2 mm to 0.5 mm). 
     The through hole (the through hole of each cap) can flare out at the end facing the separation member so that the material to be separated permeates throughout the separation member. The length of the portion flaring out is generally 0.1 mm to 1.0 mm (for instance, 0.2 mm to 0.5 mm). The grooves in the caps and holder are formed generally at a pitch of 2 mm or less (for example, 1.5 mm or less). 
     When there is a gap between the outer diameter of the elastomer tube  11  and the inner diameter of the holder  71 , a spacer can be used for filling the gap.  FIG. 6C  shows a top view of the column  10   a  provided with such a spacer, and  FIG. 6D  shows a cross-sectional view at line VId-VId shown in  FIG. 6C . The spacer  61  is disposed around the outer peripheral part of the column  10   a . The inner diameter of the spacer  61  is approximately equal to the outer diameter of the elastomer tube  11 . 
     [Another Example of Cartridge Column] 
     Hereinafter, an example of the cartridge column in which the outer peripheral surface of the elastomer tube  11  is held by a dividable holder is described as a cartridge column of the present invention.  FIG. 8A  shows an exploded perspective view of an example of the holder for the cartridge column  80 .  FIG. 8B  shows an exploded perspective view of another example of the holder, and  FIG. 8C  shows a perspective view of the holder shown in  FIG. 8B  that has been assembled. 
     A holder  81  shown in  FIG. 8A  and a holder  85  shown in  FIG. 8B  each are divided at a cross section along the central axis of the cylindrical holder. The two divided holders can be fixed to each other by a fixing means. 
     The holder  81  shown in  FIG. 8A  is composed of a holder  82  and a holder  83 . The holder  82  has protrusions  82   a  to serve as a fixing means, with the protrusions  82   a  being provided with hook portions. The holder  83  includes holes  83   a  formed to serve as a fixing means and the holes  83   a  catch the protrusions  82   a . The holder  82  and the holder  83  are fixed together, with the protrusions  82   a  being caught by the holes  83   a . Thus a cylindrical holder  81  is formed. The holder  81  has a thread formed at its outer peripheral surface. 
     The holder  85  shown in  FIG. 8B  is composed of a holder  86  and a holder  87 . The holder  86  includes protrusions  86   a  to serve as a fixing means. The holder  87  includes holes  87   a  to serve as a fixing means, with the holes  87   a  corresponding to the protrusions  86   a . The holder  86  and the holder  87  are fixed together, with the protrusions  86   a  being inserted in the holes  87   a . In the holder  86  shown in  FIG. 8B , a plurality of protrusions  86   a  are formed asymmetrically with respect to the central axis. Such a configuration can prevent the holders from being assembled with each of the holders being placed in the wrong directions. As shown in  FIG. 8C , a flat notch  87   b  is formed in a part of the holder  87 . Although it is not shown in the drawings, an identical notch also is formed in the holder  86 . The holders can be fixed together by holding the notches with spanners when the caps are tightened or loosened. 
       FIG. 9  shows an exploded sectional view of the cartridge column  80  including the holder  81 . The cartridge column  80  includes a holder  81  (holders  82  and  83 ), a column  10  disposed inside the holder  81 , and two caps  84 . The column is the column of the present invention described above and includes the elastomer tube  11  and separation members  12 . 
     Each cap  84  has a cylindrical concave part  84   h  formed therein. The concave part  84   h  has a thread groove that engages with the thread of the holder  81  and is formed at the inner peripheral surface thereof. When the column  10  is disposed inside the holder  81  and both the ends of the holder  81  are tightened with the caps  84 , both the ends of the elastomer tube  11  are pressed by the bottom surfaces  84   b  of the concave parts  84   h  and thereby the elastomer tube  11  and the bottom surfaces  84   b  are brought into close contact with each other. Thus, the material to be separated can be prevented from leaking as in the case of the cartridge column  30 . 
     In the cartridge column  80 , since the holder  81  can be divided, the column can be set inside the holder  81  easily even when the elastomer tube  11  is long or a plurality of columns are used. This cartridge column is particularly effective when the column to be disposed inside the holder has a length (when a plurality of columns are disposed, the sum of the lengths of the columns) of at least 40 mm (for example, at least 90 mm). 
     [Another Example of Cartridge Column] 
     Hereinafter, an example of the cartridge column in which pressing members are provided to be able to move to press the end faces of the elastomer tube and can move without rotating with respect to the end faces of the elastomer tube is described as a cartridge column of the present invention.  FIG. 12  shows an exploded perspective view of the cartridge column  120 . 
     This cartridge column  120  includes a column  10  and a housing. The column  10  is the column of the present invention described above and includes an elastomer tube  11  and separation members  12  (see  FIG. 1 ). The housing includes a cylindrical holder  121 , inside of which the column  10  is disposed, first caps  122   a  that are fitted into ends of the holder  121 , and second caps  123  screwed into the ends of the holder  121  from the outer sides of the first caps  122 . The housing further includes a spacer  124  disposed between the holder  121  and the column  10 , and O-rings  125  disposed between the first caps  122  and the column  10 . When the inner diameter of the holder  121  is approximately equal to or slightly larger than the outer diameter of the column  10 , the spacer  124  is not required to be provided. 
     The holder  121  has a thread formed at its outer peripheral surface. The inner diameter of the holder  121  is approximately equal to or slightly larger than the outer diameter of the spacer  124 . The holder  121  includes protrusions  121   a  to serve as a rotation preventing means at both ends thereof. 
     Each of the first caps  122  is provided with a columnar insertion part  122   b  that is inserted into the holder  121 . An annular groove where the O-ring  125  is to be disposed is formed at the end face of each insertion part  122   b . The O-ring  125  is disposed in the groove. The first caps  122  and the O-rings  125  can move to press the end faces of the elastomer tube. When the first caps  122  and the second caps  123  are attached to the holder  121 , the first caps  122  and the O-rings  125  move to press the end faces of the elastomer tube, and thereby the end faces are pressed. In other words, the first caps  122  and the O-rings  125  serve as pressing members. Furthermore, the first caps  122  each are provided with notches  122   a  to serve as a rotation preventing means. The notches  122   a  are formed so as to engage with the protrusions  121   a  of the holder  121  when the first caps  122  are fitted into the holder  121 . When the protrusions  121   a  and the notches  122   a  are engaged with each other, the first caps  122  are prevented from rotating with respect to the holder  121 . Accordingly, the first caps can be prevented from rotating with respect to the end faces of the elastomer tube disposed inside the holder  121 . This prevents the elastomer tube from rotating inside the holder  121  and being twisted along the longitudinal direction when the second caps  123  are to be screwed to the holder  121 . Therefore, damage to the separation members disposed inside the elastomer tube can be prevented. The first caps  122  each also include a feed port  122   c  formed therein, through which material to be separated is fed. 
     The second caps  123  each have a columnar concave part  123   a  formed therein and include a through hole  123   b  formed at the bottom surface thereof. The through holes  123   b  serve to feed material to be separated into the feed ports  122   c  of the first caps  122 . The concave parts  123   a  each have a thread groove that is formed at the inner peripheral surface thereof and engages with the thread of the holder  121 . With the second caps  123  having been attached to the holder  121 , the head portions of the first caps  122  are housed in the concave parts  123   a.    
     The first caps  122  are fitted to the ends of the holder  121 , and the second caps  123  are then screwed into the holder  121  from the outer sides of the first caps  122 . Accordingly, the end faces of the elastomer tube and the first caps  122  as well as the O-rings  125  come into close contact with each other, and thereby material to be separated can be prevented from leaking as in the case of the cartridge column  70  shown in  FIG. 7 . 
     The pressing members provided for the housing of the cartridge column according to the present invention are not limited to the aforementioned examples. They can have any configurations as long as they are members that can move to press the end faces of the elastomer tube and are provided to be able to move without rotating with respect to the end faces of the elastomer tube. Furthermore, the rotation preventing means also is not limited to the example described above. It also can have any configuration as long as it is a means that can prevent the pressing members from rotating with respect to the end faces of the elastomer tube when the pressing members move. For instance, converse to the example shown in  FIG. 12 , protrusions can be provided for the first caps  122  and notches can be provided for the holder  121 . Moreover, it also is possible that, for instance, engaging parts such as protrusions or grooves are provided as rotation preventing means for the insertion parts  122   b  of the first caps  122  and engage with engaging parts formed as rotation preventing means inside the holder  121  when the engaging parts of the insertion parts  122   b  are inserted into the holder  121 . 
     [Other Examples of Column and Cartridge Column] 
     In the above-mentioned examples of the column, the elastomer tube  11  and the separation members  12  can be formed monolithically so as not to be detached. Such a column can be formed by applying liquid elastomer onto the outer peripheral surfaces of the separation members  12  and drying it (if necessary, further curing it). The elastomer applied to the separation members  12  forms the elastomer tube. Such a column is particularly suitable for the cartridge column shown in  FIG. 7 . In this column, one separation member  12  or more can be disposed in the elastomer tube  11 . 
     In the examples described above, the housing had a columnar outer shape. However, it can have another outer shape, for example, a rectangular columnar shape. 
     In the columns of the present invention, the peripheries of the separation members can be reinforced with other members having no rubber-like elasticity, for example, curable resin (UV curable resin, an adhesive, fluorine resin, and a silicone coating agent), as long as the effects of the present invention can be obtained. Even when the peripheries of the separation members are covered with materials having no rubber-like elasticity, leak can be prevented from occurring between the separation members and, for example, the heat shrinkable tube by covering the peripheries with a rubber tube. 
     EXAMPLES 
     Hereinafter, the present invention is described further in detail using examples. 
     First, an elastomer tube and a housing shown in  FIG. 3  were prepared. The elastomer tube was produced by processing fluororubber (trade name: Fluorine-containing Rubber Sheet, with a hardness of A/78 (Hs80) manufactured by Tigers Polymer Corporation).  FIG. 10  shows a cross-sectional view of the resultant elastomer tube. The elastomer tube  101  shown in  FIG. 10  includes a through hole formed of a through hole  101   h  where a separation member is to be housed and a through hole  101   t  where no separation member is to be housed, with the through hole  101   h  and the through hole  101   t  being connected to each other. The elastomer tube  101  had a total length of 19 mm and an outer diameter D 1  of 8.9 mm. In the elastomer tube  101 , the portion where the separation member was to be housed had a length L 1  of 18.2 mm and an inner diameter d 1  of 3.25 mm, and the through hole  101   t  had an inner diameter d′ of 1 mm. Furthermore, the portion where the separation member was to be housed had a thickness t 1  of 2.83 mm. 
     A monolithic-type silica porous body (MonoFas) available from GL Sciences Inc. can be used for the separation member of the column of the present invention. For instance, a number of through holes whose average diameter is about 15 μm and a number of fine pores whose average diameter is about 10 nm are formed in the monolithic-type silica porous body that is used for a DNA purification kit I (MonoFas) of GL Sciences Inc. In this example, a silica porous body was used that was equivalent to the above-mentioned monolithic-type silica porous body. The length L 2  of one separation member was 2.8 to 3.0 mm, and the diameter D 2  thereof was 3.2 to 3.4 mm. Six separation members that were identical to the one described above were disposed inside the elastomer tube. The sum of the lengths of the six separation members was 18 mm. 
     Each hole (hole  42   h  shown in  FIG. 3 ) of the cap had a depth Lh of 7.5 mm and a diameter Dh of 9 mm. 
     This cartridge column was assembled and liquid chromatography was carried out. A liquid mixture of hexane (98 vol. %) and isopropyl alcohol (2 vol. %) was used for a mobile phase, and the flow rate was 0.5 ml/min or 0.2 ml/min. The material to be separated was a mixture of toluene, 2,6-dinitrotoluene, and 1,2-dinitrobenzene. The material was detected using ultraviolet rays with a wavelength of 210 nm. The detection result obtained at a flow rate of 0.5 ml/min is shown in  FIG. 11A , and that obtained at a flow rate of 0.2 ml/min is shown in  FIG. 11B . As shown in  FIGS. 11A and 11B , the use of the cartridge column of the present invention allowed toluene/2,6-dinitrotoluene and 1,2-dinitrobenzene to be separated and detected. 
     On the other hand, for comparison, a column was produced by placing separation members into a heat shrinkable tube (Penntube (product name), manufactured by Penn &amp; Nitto Corp.) formed of FEP, shrinking the heat shrinkable tube with heat, and inserting them into a tube made of resin. With this column of this comparative example, the liquid chromatography was carried out by the same method as in the above. As a result, a single high peak was observed in the early stage after start of measurement and no peaks other than that were observed. It is believed that this single peak was observed because the mobile phase and material to be measured did not pass through the separation members but leaked in the column. In this manner, leakage occurred and normal measurement was not possible in some cases when the heat shrinkable tube was used. 
     In the above, embodiments of the present invention were described using examples. However, the present invention is not limited to the embodiments described above but is applicable to other embodiments based on the technical idea of the present invention. 
     From another viewpoint, the present invention also is applicable to a column including a columnar (including a disc shape) separation member (which is not limited to a vitreous porous body as long as it has separation ability) and an elastomer tube for housing the separation member. This elastomer tube is provided with a through hole for housing the separation member, and the cross-sectional shape of the through hole is a shape identical to the cross-sectional shape of the separation member or a circular shape. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be used for chromatography. The column and cartridge column of the present invention can be used, for example, for liquid chromatography, gas chromatography, separation analyses, and apparatuses for them. The column and cartridge column of the present invention make it possible to separate various substances, for example, organic compounds such as protein and peptide.