Abstract:
A fitting device for a tubular column having an exterior flange at one of its ends is disclosed. The device includes a fitting composed of (i) a piston for insertion into the end of the column adjacent the flange, (ii) an enlarged-diameter member having a contact surface for contacting the flanged end of the column when the piston is fully inserted into the column, and (iii) a circumferential seal encircling the piston for providing a fluid-tight seal between the piston and interior end region of the column, when the piston is inserted into the column. A clamp in the device is received on the column by sliding from the end of the column opposite said flange, for engaging the column flange and the fitting&#39;s enlarged-diameter member, to secure the fitting to the column flange, with the piston inserted into the tubular column, thus to maintain said seal when fluid is forced through the fitting by application of pressure to fluid within the column.

Description:
[0001]     This application claims priority to U.S. provisional patent application No. 60/665,182 filed on Mar. 25, 2005, which is incorporated herein in its entirety by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a column fitting device, such as a fitting device designed for use in flash chromatography, and to a packed chromatography column and to a sample loading column employing the fitting device.  
       BACKGROUND OF THE INVENTION  
       [0003]     Flash chromatograph is widely used for chromatographic separation of chemical or biochemical materials. In a typical flash-chromatography application, the column is prepared by equipping the downstream end of the column with a downstream fitting and frit, packing the column with a suitable separation matrix material, and sealing the top or upstream end of the column with a sealed fitting capable of supporting the internal pressures applied to the column during operation, e.g., 25-150 psi. Typically the column is formed of a polymeric material, e.g., polyethylene, which can withstand the expected internal pressures, and which is sufficiently transparent to allow the contents of the column to be viewed. The upstream fitting typically includes a sealed piston or plug which is inserted into the upper end of the column.  
         [0004]     To date, various methods for attaching the upper fitting to the column have been proposed. One approach has been to glue the fitting plug to the interior wall of the column, using, for example, fast-setting cyanoacrylic glues capable of bonding to polymer surfaces. To date, however, there is no glue available that is capable of forming a strong and reliable bond to the smooth-polymer walls of the column. In addition to complicating the dismantling and replacement of the column, if that becomes necessary, this approach also introduces a potential source of chemical incompatibility and contamination.  
         [0005]     Another approach has been to heat-weld the fitting plug to the column, once the plug is placed in the column, relying on the formation of a fused-polymer weld between the two. This approach requires special heating equipment and is unavailable where the packed column material is susceptible to heat damage.  
         [0006]     A third approach employs a metal cage with a screw-on cap for immobilizing the column and the upstream fitting during column operation. In addition to the inconvenience and expense of the metal cage, the cage itself blocks easy viewing of the column and its contents.  
         [0007]     There is thus a need for a column fitting that can be placed on a chromatography column, is capable of withstanding internal column pressures of between, typically, 50 psi to up to 150 psi or more, and which does not suffer from the prior-art disadvantages or limitations noted above.  
       SUMMARY OF THE INVENTION  
       [0008]     The invention includes, in one aspect, a fitting device for a tubular column having an exterior flange at one of its ends. The device includes a fitting composed of (i) a piston adapted to be inserted into the end of the column adjacent the column flange, (ii) an enlarged-diameter member having a contact surface adapted to contact the column flange when the piston is fully inserted into the column, and (iii) a circumferential seal encircling said piston, adapted to provide a fluid-tight seal between the piston and interior end region of the column, when the piston is inserted into the column. The piston provides a fluid passageway for communicating the interior of the column with an exterior port. A clamp in the device is received on the column by sliding from the end of the column opposite the column flange, and engages the column flange and the fitting&#39;s enlarged-diameter member, to secure the fitting to the column flange, with the piston inserted into the column, to maintain the seal when fluid is forced through the fitting by application of pressure to fluid within the column.  
         [0009]     In one general embodiment, the fitting&#39;s enlarged diameter member includes an external threaded portion, and the clamp includes a threaded sleeve for engaging the threaded portion and a reduced-diameter lip for engaging the column flange when the sleeve is threaded on the fitting. The piston may be moved axially to a desired insertion position by tightening the threaded sleeve. Where the column is deformable in the region of the seal when pressure is applied to fluid in the column, the reduced-diameter lip of the clamp may encircle the column in the region of the seal, limiting the amount of column deformation that can occur in the region of the seal.  
         [0010]     In another general embodiment, the piston is intended to be fully inserted into the column to a position at which the fitting&#39;s contact surface is in contact with the column flange. Here the clamp may include a snap-on, polymeric ring having an inner annular groove dimensioned to receive the column flange and enlarged-diameter member therein, when the ring is pressed over the column flange, and while engaging the enlarged-diameter structure. The clamps&#39; inner annular groove is defined by a pair of annular ridges, one of which may be beveled to accommodate annular deformation of the ring as it is being forced over the fitting&#39;s enlarged-diameter member, and the other of which is dimensioned to engage the column flange. The exposed, fluid-contact surface of the piston may have a plurality of recessed channels formed therein for distributing fluid from the fitting over the cross-sectional area of the column. Alternatively, or in addition, this surface may be conically recessed for carrying fluid from the fitting into the column.  
         [0011]     In another aspect, the invention includes a column assembly for use in flash chromatography and the like. The assembly includes a chromatographic column having an exterior flange at its upstream end and a tapered downstream end region, a chromatography medium filling the column, a fitting sealed in the column&#39;s downstream end and providing a fluid passageway for liquid flow out of the column, and a fitting device of the type described above sealing the upstream end of the column. In particular, the fitting device in the assembly may include a snap-on clamp for securing the fitting to the column.  
         [0012]     The downstream end region of the column may be threaded, and the downstream fitting may have a threaded body threadedly attached to the column end region. The body may define an interior-facing well containing a frit therein for supporting the chromatography medium at the column&#39;s downstream end. Alternatively or in addition, the downstream fitting may have (i) a stem extending from the downstream end of the fitting body and adapted for friction-fit coupling to a coupling receptacle in a second flow device, and (ii) a cap rotatably mounted on the body adapted to rotatably engage a threaded portion of such receptacle, to lock the coupling stem within such receptacle.  
         [0013]     In still another aspect, the invention includes a method of preparing a column of the type having a having an exterior flange at its upstream end and a downstream end region sealed with a downstream fitting, for use in flash chromatography. The method includes the steps of (a) adding a chromatography matrix material to the column to a level in the column within a given distance from the upstream end of the column, (b) positioning in the upstream end of the column, a fitting having (i) a piston insertable into the column end, (ii) a circumferential seal encircling said piston, for providing a fluid-tight seal between the piston and interior end region of the column, and (iii) an external threaded enlarged-diameter member opposite the piston, (c) engaging the threaded enlarged-diameter member with a threaded sleeve having a reduced-diameter lip for engaging the column flange when the sleeve is threaded on said fitting, and (d) tightening the sleeve on the fitting until the piston is brought into contact with the matrix material or into contact with a frit placed between the matrix material and the plug.  
         [0014]     Also disclosed is a fitting/coupling device for a chromatography column or the like having a downstream threaded end region or socket. The device includes (i) a threaded body for threaded attachment to the column end region, where the body defines an interior-facing well, (ii) a frit contained within the well and designed for supporting the chromatography medium in the column, (iii) a coupling stem extending from the downstream end of the body for friction-fit coupling to a coupling receptacle in a flow device, and (iv) a cap rotatably mounted on the body for rotatably engaging a threaded portion of the coupling receptacle, to lock the coupling stem within such receptacle.  
         [0015]     These and other objects and features of the invention will be more fully understood when the following detailed description is read in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIGS. 1A and 1B  are cross-sectional views showing the upper end portion of a chromatography column and steps in attaching a fitting device constructed according to one embodiment of the invention to the column end;  
         [0017]      FIG. 2  additionally shows a lower end portion of the same column shown in  FIG. 1 , having a lower-end fitting/coupling device constructed according to another aspect of the invention; and  
         [0018]      FIGS. 3A-3C  are cross-sectional views showing the upper end portion of a chromatography column and steps in attaching a fitting device constructed according to a second embodiment of the invention to the column end;  FIG. 3C  additionally shows attachment of an upstream column to the upper end region of the first column employing a lower-end column fitting/coupling device like that shown in  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     The present invention relates to fittings designed for sealing the ends of a pressurized column, for example, a column used for flash chromatography, and capable of withstanding operating pressures typically in the pressure range 25-150 psi or higher, e.g., up to about 200 psi. In one aspect of the invention, described in section A, the fitting is designed to cap an end of the column, and typically the upper end, which terminates in an end-flange. In a second aspect of the invention, described in Section B, a fitting/coupler is described that is designed to cap the lower, threaded out-flow end of a column.  
         [0000]     A. Fitting for a Flanged Column End  
         [0020]      FIGS. 1A-1C  illustrate in cross section, the upper end region  12  of a column  10  adapted to receive the fitting of the invention, for sealing the end of the column for fluid operating pressures in the fluid-pressure range of between about 25-200 psi, and typically a fluid-operating range suitable for flash chromatography, e.g., 25-150 psi. Column  10  includes a cylindrical wall portion  14  extending along most of the column length, and which terminates at its upper end in an annular flange  16 . At its lower end, the column has a curved tapered end region  18  which terminates in a threaded socket  20 . Column  10  may be a glass, plastic or metal column, typically a transparent plastic column, such as one formed of polyethylene, polypropylene, or the like. The column dimensions may vary widely, from small columns having inner diameters of a 5-10 mm, and column volumes of 50-150 ml, to large columns having inner diameters of up to 5-10 cm, and volumes of one to several liters. Such columns are widely available commercially, such as listed in the Thomas Register Directory, and accessed at the Register website: 
        http://www.thomasregisterdirectory.com/laboratory equipment supplies/chromat ography columns 0044633 1.html.          
         [0022]     The column may be packed with a suitable chromatography or other packing material, such as silica gel, as indicated at  15  in the figures. The packing material, in turn, may be covered by a frit or filter  17  which separates the packing material from the upper end region of the column and acts to keep the upper surface of the chromatographic material relatively undisturbed during column operation, as fluid is being introduced into the column.  
         [0023]     The upper end of the column is sealed with a fitting device  21  constructed according to a first embodiment of the invention. Device  21  includes a fitting  22  having a plug or piston  24  which is dimensioned to be snugly inserted into the column&#39;s flanged end, as shown. A channel  28  formed in the piston provides a fluid passageway for introducing fluid, e.g., liquid into the column through the fitting. Passageway  28  communicates at its upper end with a receptacle  30  designed for receiving the male stem of a fluid connector through which fluid may be supplied to the column. The lower surface of the piston in the figures has a shallow conical taper, as seen, to provide a fluid-flow space  25  between the piston and filter  17 , thus to distribute fluid from the passageway evenly over the surface of the frit. Alternatively, or in addition, the lower piston surface can be formed with a plurality of grooves which radiate outwardly from the lower end of passageway  28  at angularly spaced intervals, for purposes of distributing fluid from the fitting evenly over the frit.  
         [0024]     An O-ring seal  36  held in an annular groove  34  in the piston makes a fluid-tight seal between the piston and interior end region of the column when the piston is inserted into the column, as can be appreciated from the figures. The fitting also includes an annular flange or enlarged-diameter member  32  formed integrally with the piston and having a contact surface  33  which is pressed against the column flange in its operative, sealing position, as shown in  FIG. 2 . The fitting is preferably formed as an integral unit of a polymer (plastic) such as nylon, teflon, delrin, polyvinyl, polyethylene or the like, preferably formed by single-piece molding according to well-known methods.  
         [0025]     For clamping the fitting to the column, the fitting device includes a snap-on ring or clamp  38  designed to lock the column and fitting flanges together, as shown in  FIG. 2 . As seen in the figures, the clamp has a pair of annular ridges or flanges  40 ,  42  ( FIG. 1B ) that define an inner groove  44  dimensioned to receive the column and fitting flanges, when the clamp is placed in its operative condition shown in  FIG. 2 . The upper surface of ridge  42  is beveled, as shown, to facilitate outward deformation of the ridge as it is moved over flange  32  in the fitting. Clamp  38  is preferably formed by single-piece molding of a rigid, slightly deformable plastic, such as the plastic used in forming fitting  22 .  
         [0026]     In operation, the lower end of the column is sealed with a downstream fitting, and the column is packed with a suitable material, such as silica gel to a level close to the top of the column, then covered with a frit, as shown. The position of the frit is preferably such that it is contacted by the lower surface of the fitting in its fully assembled condition, as seen in  FIG. 2 .  
         [0027]     After filling the column, fitting  22  is inserted into the column, as shown in  FIG. 1A , until the fitting flange&#39;s contact surface  33  is pressed against the column flange, as seen in  FIG. 2 . As noted above, the column packing height is preferably such that the fitting, when fully inserted in the column, contacts the upper surface of filter  17 . Clamp  38 , which is placed over the column&#39;s lower end, is now moved upwardly ion the column until it makes contact with the fitting flange. With continued upward movement of the ring, this contact acts to deform the upper rim of the clamp ( FIG. 1B ), allowing it to slip over the fitting flange until both column and fitting flanges are snugly received within the clamp&#39;s inner annular groove, as seen in  FIG. 2 . The clamp thus holds the fitting at the fully inserted position within the column, maintaining the O-ring seal between the fitting and column when fluid is introduced into the column under pressure through the fitting.  
         [0028]     In another aspect, the invention includes a column assembly  50  for flash chromatography and the like which includes the fully assembled column shown in  FIG. 2 . The assembly includes a chromatographic column  10  having an exterior flange  16  at its upstream end and a tapered downstream end region  18  terminating at a threaded downstream receptacle  20  in which a downstream fitting/coupler device  100  (detailed in Section B below) is threadedly received. The column is filled with a chromatographic separation material  15 , and capped at its upstream end, by fitting device  21  just described. This assembly is preferably preassembled for customer use, where the packing material is supplied either in dried or wet form, and the column is ready for use simply by introducing a suitable wash or conditioning medium through the column.  
         [0029]      FIGS. 3A-3C  illustrate a fitting device  64  constructed according to a second embodiment of the invention. Shown in the figures is the upper end portion of a flash chromatography column  66  having an upper-end flange  68 , as described above for column  10 . The column may be packed with a chromatography material  71  and covered by a frit or filter  70  also as described above. Unlike the fitting device described above, device  64  can be clamped in the column end at a variable plug depth, providing more flexibility in the height of the packing material, and also providing a means of applying pressure to the top of the packing material, for packing purposes.  
         [0030]     Fitting device  64  includes a fitting  70  composed of a plug  72  dimensioned to be inserted snugly into the column bore, and an enlarged-diameter member  74  forming a contact surface or shelf  76  which, by contact with the column flange, limits the extent to which the plug can be inserted into the column bore. The enlarged-diameter member is threaded at  78  above contact surface  76  for a purpose to be described. A bore  77  formed through the fitting provides a passageway in the fitting between an upper fitting socket  80  and the lower end of the fitting in the figures. As seen in  FIG. 3B and 3C , fitting socket  80  is designed to accept the male end of a connector  82 .  
         [0031]     The lower-end surface of plug  72  may be tapered, as shown, or grooved, to distribute liquid supplied through the fitting over the entire surface of filter  70 , as described above for fitting device  10 . Also as described above, an O-ring seal  84  carried in an annular groove  86  adjacent the lower end of the plug provides a seal for fitting within the column.  
         [0032]     The fitting device includes a clamp  90  for clamping the fitting to the column. In the present embodiment, the clamp takes the form of a threaded sleeve  92  whose internal threads  94  engage threads  78  on the fitting&#39;s enlarged-diameter portion, for screwing the clamp on the fitting with rotation of the clamp. A lower annulus or flange  96  in the clamp provides a shelf  98  that engages the lower surface of the column flange, as shown in  FIG. 3C , to lock the fitting to the clamp at a selected plug depth within the column. Flange  96  also provides column-wall support in the region of the fitting seal, serving to limit the extent of column deformation that can occur in the region of the seal as a result to fluid pressure within the column.  
         [0033]     In operation, column  66  is equipped with a lower column fitting (similar to that shown in  FIG. 2 ), then packed with a column material to a height close to the upper end of the column and capped with a filter  70 . The fitting plug is now inserted into the column, as shown in  FIG. 3A  and clamp  96  is moved by sliding it from the lower end of the column up to a position, shown in  FIG. 3B , where the clamp can be screwed onto the fitting body.  
         [0034]     As can be appreciated from  FIGS. 3B and 3C , as the clamp is tightened, and with the clamp flange engaging the column flange, the lower surface of the fitting plug is drawn into the column bore until it makes contact with the filter  70  in the column. Thus, the fitting device allows for the preparation of a packed column by (a) adding a chromatography matrix material to the column to a level in the column within a given distance from the upstream end of the column, and moving the plug of a column fitting by clamp tightening until the plug is brought into contact with the matrix material or into contact with a frit placed between the matrix material and the plug. The fitting device described is easily removed from a spent column, and reusable with a freshly packed column.  
         [0000]     B. Fitting for a Threaded Column Socket  
         [0035]     In another aspect, the invention includes a fitting/coupling device  100  seen in the lower part of  FIG. 2 , where the device serves as the downstream fitting for column  10  and in the upper part of  FIG. 3C , where the device serves as the downstream fitting for a second column and attached to column  10  through connector  82 .  
         [0036]     With reference first to  FIG. 2 , device  100  is formed of a body  106  having a threaded region  107  whose threads engage the threaded receptacle forming the lower end of column  10 . Body  106  has a central bore  108  which extends from an upstream cavity or well  112  formed in the body to a downstream stem  110  that is designed for engaging a fluid connector, such as connector  82  shown in  FIG. 3C . The fitting is sealed in receptacle  20  by an O-ring seal  114  contained in an annular groove  116  formed in body portion  106 . The lower portion of the body is radially enlarged at  118  and includes an annular groove  120  formed therein.  
         [0037]     Well  112  formed at the upstream end of bore  108  is dimensioned to receive a filter or frit  119  therein. This frit serves as the lower filter support for packing material in the column, as seen in the figures, and obviates the needs for a separate filter normally used in to support column material in such a chromatography column. The filter thus adds the convenience for a packing operation, and also places the chromatography media directly against the lower frit, eliminating a gap between the filter and fitting at which mixing of separated sample components can occur.  
         [0038]     Mounted on the lower portion of the body, for free rotation thereon, is a cap  122 , which has an interior annular projection  124  confined within groove  120 , allowing the cap to rotate freely on the lower end of body  106  while being held thereon. The cap has a threaded region  126  ( FIG. 2 ) which engages a threaded projection on a fluid connector, such as connector  82  ( FIG. 3C ), to tighten the connector to the fitting device, by rotation of the cap. This feature allows a connector to be locked to or released from the fitting without having to disturb the position of the fitting in the column. This feature permits coupling a sample introduction column to a chromatography column. This feature also permits the coupling to two chromatography columns in order to obtain greater solute resolution and sample loading capacity. Additionally, it permits coupling different types of chromatography columns to enable mixed mode separations.  
         [0039]     Fitting  100  is preferably formed of a rigid plastic, such as a polyvinyl, or polypropylene plastic, e.g., by injection molding. The cap is formed separately and pressed onto body  106 .  
         [0040]     From the foregoing, it can be appreciated how various objects and features of the invention are met. The fitting device of the invention is easy to attach to a column by mechanical attachment, is simple in construction, and provides a seal capable of withstanding pressure of up to 150 psi in flash chromatographic and related operations. In two of the embodiments described herein, the device is designed for snap-on assembly of a disposable, prepacked column. In another embodiment, the device is reusable and allows for user packing and column assembly by adjusting the position of the fitting plug to match the height of the column packing material.  
         [0041]     The fitting coupler of the invention simplifies column assembly and packing by providing a lower frit that is carried on the fitting itself. The coupler/fitting is further designed for easy locking to and release from fluid couplers.  
         [0042]     While the invention has been described with respect to particular embodiments and applications, it will be appreciated how various modifications and changes may be made without departing from the invention.