Abstract:
A flash chromatography apparatus which provides an improved apparatus for large and medium commercial scale flash chromatography columns. More particularly, the invention relates to a flash chromatography column and cartridge system for positioning and ease of loading and unloading of stationary phase agent in the flash chromatography column. The flash chromatography column further provides flow distributors to support the stationary phase and permit plug flow through the column. The apparatus of the present is modular and can be disposed in any configuration to reduce maintenance cost and downtime in a commercial installation. Flash chromatography is widely used for purification of low molecular weight organic compounds and products of organic synthetic reactions.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention is generally concerned with an improved apparatus for use in large and medium commercial scale flash chromatography columns. More particularly, the invention relates to a flash chromatography column and cartridge system for positioning and ease of loading and unloading of stationary phase agent in the flash chromatography column. The flash chromatography column further provides flow distributors to support the stationary phase and permit plug flow. The apparatus of the present is modular and can be disposed in any configuration to reduce maintenance cost and downtime in a commercial installation. 
       BACKGROUND 
       [0002]    Chromatography is a technique used to, among other things, separate component elements of a starting material. Within the general field of chromatography, there are several types. Supercritical fluid chromatography (SFC) is a high pressure, reverse-phase method that typically operates above the critical point of the mobile phase fluid, and offers significant speed advantage and resolution over traditional techniques such as high performance liquid chromatography (HPLC). SFC employs carbon dioxide or another compressible fluid as a mobile phase, sometimes with a co-solvent, to perform a chromatographic separation. SFC has a wide range of applicability and typically uses small particle sizes of 3-20 microns for column packing material and is for analytical to preparative scale applications because of the lower pressure drop. In HPLC applications pressure at the top of the column typically reaches up to 1000 psi but pressure at the bottom is reduced to ambient pressure, creating a significant pressure drop. 
         [0003]    Liquid chromatography (LC) applies to a cruder, lower pressure, lower performance technique for simple separations. Flash chromatography is a form of adsorptive chromatography and is subset of LC that uses a very simple, porous stationary phase with particle sizes nearer to 100 microns often in a disposable cartridge, or column. Because the particles in the packing material are larger and often irregular, the columns are much cheaper and are considered disposable. Pressure at the top of the column in flash chromatography applications is typically up to 100 psi and dropping down to ambient at the bottom of the column. Still (U.S. Pat. No. 4,293,422) describes a method of adsorptive chromatography in which the mobile phase is first admitted into a space above an adsorbent bed of silica gel, then pushed through the bed with gas pressure. Once the space is cleared, the mobile phase with dissolved compounds for analysis is admitted, and it too is pushed into the bed, displacing the earlier charge of neat mobile phase. Then in a third step, a second charge of neat mobile phase forces the solution through the bed, causing fractionation of the solute. A subsequent disclosure by Andrews (U.S. Pat. No. 4,591,442) describes a similar device, the main difference being in the placement of the liquid holding space. Both disclosures focus on mechanical design and methods for achieving flash chromatography at relatively low pressure. More recently, Ritacco (US App. 2003/0102266) describes a convenient polymer-encased cartridge for use as a single ended flash chromatography column. Anzar (WO/2004-051257, US App. 2005/0287062) describes another type of pre-filled cartridge for flash chromatography. Common features of all of these disclosures are (1) an emphasis on instrumental convenience, and (2) the use of an adsorptive bed that allows for fast, although imprecise, separation of solutes. The disclosures also emphasize gas and liquid chromatography applications of low to moderate pressure. 
         [0004]    The majority of all separations in flash chromatography use a normal phase technique with solvents such as methanol, ethanol, hexane, and heptane and occasionally the reverse phase technique with water and acetonitrile. Chemists buy thousands of flash chromatography systems per year to use primarily as a simple, repeatable normal phase purification technique. Because of the vast number of flash chromatography systems in medicinal chemistry laboratories in pharmaceutical research environments, users, insurers, regulators and environmentalists are growing increasingly concerned with the vast amount of toxic waste solvent generated at these sites. Given the obvious problems associated with unsafe, toxic, flammable solvents, a new simple, normal phase technique must be found that is fast and uses less toxic solvents. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides an opportunity to carry out flash chromatography in a flash chromatography process with medium to large size samples. The apparatus of the present invention can support an adsorbent capacity of from about 10 to about 50 kilograms of adsorbent (more preferably, the adsorbent capacity ranges from about 25 to about 50 kilograms) in a chamber which can be pressurized to operate over an operating pressure range of from about 100 psia (pounds per square inch absolute) (7.82 atm) to about 150 psia (11.23 atm). The amount of the adsorbent in the apparatus can be disposed within the apparatus by means of inert spacers. The modular design permits either a single apparatus or an apparatus having multiple chambers to be arranged for convenient maintenance operation. 
         [0006]    In one embodiment, the invention is a modular apparatus for performing flash chromatography. The apparatus comprises a chamber comprising a cylindrical shell, a proximal and a distal annular ring, a proximal and a distal cover plate, a flash chromatographic cartridge, a gasket, a pair of pivot shafts, and a stationary horizontal base. The cylindrical shell has a proximal end and a distal end. The cylindrical shell encloses a hollow cylindrical interior, has outer surface and an interior surface, a centerline and a midpoint along the centerline. The proximal annular ring and a distal annular ring are each sealingly disposed at the proximal end and at the distal end of the cylindrical shell, respectively. Each annular ring has an upper surface, a hinge and a plurality of mounting clamps distributed uniformly about each annular ring. The upper surface has a raised ring. Both the proximal cover plate and a distal cover plate, each have a center, an outer side, an underside, and a nozzle. The underside of each cover plate has disposed thereon a registration channel, a sealing channel concentric with the registration channel, and a plurality of radial flow distribution channels extending radially from a distribution hub at the center and extending toward the registration channel. Each raised ring on the proximal and distal annular rings is adapted to be disposed in the registration channel when each cover plate is in a closed position. Each cover plate is removably disposed on the annular ring at the distal end and at the proximal end of the cylindrical shell and rigidly attached to said hinge to properly register the cover plate on the annular ring and to permit the cover plate to be sealingly disposed on the annular ring and secured by the plurality of mounting clamps. Each nozzle is in fluid communication with the hollow cylindrical interior. A flash chromatographic cartridge is disposed in the hollow cylindrical interior. The flash chromatographic cartridge having a proximal end and a distal end comprises a cylindrical cartridge shell, a first and second porous frit plate and a porous support plate. The cylindrical cartridge shell encloses a hollow cartridge interior. The first porous frit plate is sealingly disposed toward the proximal end and a second porous frit plate is sealingly disposed toward the distal end of the cylindrical cartridge shell. Each porous support plate is disposed over the respective frit plate and rigidly attached to the cylindrical cartridge shell toward the proximal and distal ends such that at least a portion of the cylindrical shell extends beyond the porous support plate to provide a raised proximal ring and a raised distal ring adapted to be positioned within the sealing channel of each cover plate adjacent to the cylindrical shell when each cover plate is in the closed position. A stationary phase adsorbent is disposed in the hollow cartridge interior such that the stationary phase adsorbent is in fluid communication with the hollow cylindrical interior. The gasket is disposed in the sealing channel of each cover plate to provide a seal between each annual ring and each cover plate and between the cylindrical cartridge shell and each cover plate. A pair of pivot shafts is rigidly disposed on the outer surface of the cylindrical shell at the midpoint and extending outwardly from the outer surface along a line at right angles to the centerline. A stationary horizontal base has a pair of upright members. Each of the upright members extends above the stationary horizontal base at a 90 degree angle relative to the stationary horizontal base and terminates in a bearing which is adapted to receive the pair of pivot shafts. The cylindrical shell can be positioned vertically or horizontally relative to the stationary horizontal base. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic representation of a preferred embodiment of the modular apparatus of the present invention showing a chamber and a modular base. 
           [0008]      FIG. 2   a  is a cross-sectional view of the chamber of one embodiment of the invention. 
           [0009]      FIG. 2   b  is a top view of the chamber of one embodiment of the invention. 
           [0010]      FIG. 2   c  is a bottom view of the cover plate of one embodiment of the invention. 
           [0011]      FIG. 2   d  is a cross-sectional view of the cover plate of one embodiment of the invention. 
           [0012]      FIG. 2   e  is a detail view of a corner of the chamber at Section BB of one embodiment of the invention. 
           [0013]      FIG. 3   a  is a top view of one embodiment of the modular base of the invention. 
           [0014]      FIG. 3   b  is a front view of one embodiment of the modular base of the invention. 
           [0015]      FIG. 3   c  is a side view of one embodiment of the modular base of the invention. 
           [0016]      FIG. 4  is an isometric view of one embodiment of a multiple module apparatus of the invention. 
           [0017]      FIG. 5  is a cross-sectional view of one embodiment of a stationary phase adsorbent cartridge of the invention. 
           [0018]      FIG. 6  is a top view of one embodiment of a support plate disposed in the stationary phase adsorbent cartridge of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Flash chromatography is useful for rapid, preparative separations with moderate resolution. Flash chromatography is widely used for purification of low molecular weight organic compounds and products of organic synthetic reactions. Such organic compounds can include proteins, oligosaccharides, DNA molecules and virus particles. Modern flash techniques include the use of convenient disposable flash cartridges instead of glass columns. Flash purification systems allow users to speed up the purification process for quicker results and higher throughput. Flash chromatography does provide the resolution or reproducibility of HPLC; it is a technique that is employed to improve the purity of samples to an acceptable level or prepare samples for further purification. 
         [0020]    As used herein in the specification and claims, including as used in the examples and unless otherwise expressly specified, all numbers may be read as if prefaced by the word “about”, even if the term does not expressly appear. Also, any numerical range recited herein is intended to include all sub-ranges subsumed therein. 
         [0021]    Referring to  FIG. 1 , a modular flash chromatographic apparatus is shown for performing flash chromatography separation. The modular flash chromatographic apparatus includes a chamber  10  and a modular base  40 . 
         [0022]    Referring to  FIGS. 2   a ,  2   b ,  2   c ,  2   d  and  2   e , the chamber  10  includes a cylindrical shell  5  having a proximal end A and a distal end B. The cylindrical shell  5  encloses a hollow cylindrical interior  2  and has outer surface  12  and an interior surface  14 . The cylindrical shell  5  has a centerline  16  and a midpoint  18  along the centerline. A proximal annular ring  20  is sealingly disposed at the proximal end A and a distal annular ring  20 ′ is sealingly disposed at the distal end B of the cylindrical shell  5 . Each annular ring has a hinge  26  (or  26 ′) and a plurality of mounting clamps  30  (or  30 ′) distributed uniformly about the annular ring ( 20  or  20 ′). There are two identical circular cover plates ( 24 ,  24 ′) removably disposed at the proximal and the distal ends of the cylindrical shell  5 . A first cover plate  24  which has an input nozzle  28  in the center, is removably disposed on the proximal annular ring  20 , and a second cover plate  22 ′ which has an outlet nozzle  28 ′ is removably disposed on the distal annular ring  24 ′. A weep nozzle  34  is disposed near the distal end of the cylindrical shell in fluid communication with the hollow cylindrical interior  2  to provide for the draining of any fluid from the chamber prior to servicing the chamber or removing a stationary phase adsorbent cartridge (See  FIG. 5 ). The weep nozzle  34  on the hollow cylinder can be used for providing radial nitrogen pressure to the stationary adsorbent cartridge which results in better sealing of the stationary adsorbent cartridge in the chamber  10 . The first and second cover plates  24  are mirror images of each other and include a nozzle  28  in the center of each cover plate, and a concentric registration channel  36 , a concentric sealing channel  35 , and a plurality of radial flow distribution channels  8  extending radially from a distribution hub  21  toward the registration channel disposed on an underside of each cover plate  24  (See  FIG. 2   e  for details of the cover plate). A gasket or o-ring  22  is disposed in the sealing channel  35 . The sealing channel  35  is adapted to accommodate an end portion of the cylindrical shell  5  and a portion of the cylindrical outer wall  120  of the stationary adsorbent cartridge  100  (See  FIG. 5 ) when in the closed or sealed position, wherein the end portion of the cylindrical shell and the cylindrical outer wall  120  of the stationary adsorbent cartridge  100  are in contact with the gasket  22  in the sealing channel  35 . The first cover plate  24  is rigidly attached to the hinge  26  to properly register and seat the first cover plate  24  on the proximal annular ring  20  and to permit the first cover plate  24  to be sealingly disposed on the proximal annular ring  20  and secured by the plurality of mounting clamps  30 . The annular ring includes a raised ring  38  adapted to be disposed in the registration channel  36  when the cover plate  24  is in the closed or sealed position relative to the annular ring  20 . Similarly, the second cover plate  24 ′ is rigidly attached to the hinge  26 ′ to properly register and seat the second cover plate  24 ′ on the distal annular ring  20 ′ and to permit the second cover plate  24 ′ to be sealingly disposed on the distal annular ring  20 ′ when in the closed or sealed position. Each cover plate is secured to each annular ring by a plurality of mounting clamps  30  and  30 ′. Each clamp has a clamp assembly for connecting and disconnecting the registered cover plates to the annular rings. Typically, the clamp assembly has a pair of clamp segments ( 30  upper and  31  lower as shown in  FIG. 2   b ) and at least one cam, spring or threaded shaft (not shown) in operable engagement with the clamp segments. The clamp segments are movable between a closed position to engage the cover plates and an open position to disengage from the cover plates. At least one or a pair of handles  29  are optionally disposed on the outer side of the cover plates to facilitate the movement of the chamber between a vertical and a horizontal position and to provide stability in opening or closing the cover plate. The gaskets  22  and  22 ′ are in the form of o-rings which can be composed of VITON resin, a fluoroelastomer resin (available from E. I. du Pont de Nemours and Company, Wilmington, Del.), Teflon, a polytetrafluoroethylene PTFE (available from E. I. du Pont de Nemours and Company, Wilmington, Del.), chlorinated polyethylene (CPE), and asbestos. A gasket comprising a silicon encapsulate with PTFE is preferred. The inlet nozzle and the outlet nozzles are in fluid communication with the hollow cylindrical interior  2 . A pair of pivot shafts  38  are rigidly disposed on the outer surface  12  of the cylindrical shell  5  at the midpoint  18 . A pivot positioning wheel  3  is disposed on at least one of the pivot shafts for the manual movement of the chamber from a vertical position to a horizontal position. The pivot shafts  38  extend outwardly from the outer surface  12  along a line at a right angle to the centerline  16 . The chamber  10  is supported by a modular base  40  in a manner which permits the chamber  10  to be rotated between a vertical position and a horizontal position. The orientation of the hinge ( 26  and  26 ′) is in line with the pivot shafts to permit the cover plate ( 24  or  24 ′) to be opened on a horizontal plane relative to the stationary horizontal base. Preferably, the chamber comprises materials selected from the group consisting of stainless steel, corrosion resistant alloy, metals having a fluoropolymer coating, and mixtures thereof. More preferably, the chamber comprises stainless steel or corrosion resistant steel. 
         [0023]    With reference to  FIG. 2   c , an underside view of a cover plate  24  or  24 ′ is shown. The following description applies to the cover plate at both the distal and the proximal ends of the cylinder  10 . The cover plate  24  includes a registration channel  36  adapted to receive the registration ring  38  on the annular ring  20 , a sealing channel  35  adapted to receive the proximal or distal end of the cylindrical shell  5  and a portion cylindrical outer wall  120  of the stationary adsorbent cartridge. The underside of each cover plate  24  includes a plurality of radial flow distribution channels  8  extending radially from a distribution hub  21 . The hinge  26  is shown rigidly disposed on the cover plate. 
         [0024]    With reference to  FIG. 2   d , a cross-sectional view of the cover plate at section AA in  FIG. 2   c  is shown. The nozzle  28  is shown extending through the cover plate  24  in fluid communication with the distribution hub  21 . The registration channel  36  and the sealing channel are shown in relation to the hinge  26  and the nozzle  28 . 
         [0025]    With reference to  FIG. 2   e  which is a schematic drawing showing the detail of the proximal and distal ends of the cylindrical shell  5  at Section BB of  FIG. 2   a  and provides details on the annular ring and cover plate to show how the seal and registration of the cover plate and annular ring achieve a seal and engage both the cylindrical shell and the cylindrical outer wall  120  of the stationary adsorbent cartridge within the sealing channel  35 . Proper registration of the cover plate is maintained by hinge  26  and the a raised ring  38  adapted to be disposed in the registration channel  36  when the cover plate  24  is in the closed or sealed position. When the stationary adsorbent cartridge is inside the cylindrical shell  5 , the cylindrical outer wall is adjacent to the interior surface  14  of the cylindrical shell  5 . The portion of the cylindrical outer wall  120  of the stationary adsorbent cartridge extending beyond the porous support plate  114  and the frit plate  110  extends into the sealing channel  35 . The distribution hub  21  disposed on the underside of each cover plate  24  is shown for reference purposes. 
         [0026]    With reference to  FIGS. 3   a ,  3   b  and  3   c , a stationary horizontal base  40  comprising a pair of side members  48 , a front and back member  49  disposed at right angles to the side members  48  forming a rectangular frame, a plurality of legs  50  extending below the frame and terminating in a foot  52 , and a pair of upright members  44 . Each of the upright members extend above the frame at a 90 degree angle relative to the frame and terminating in a bearing assembly  42  adapted to support the chamber and to receive the pair of pivot shafts  32  (See  FIGS. 2   a  and  2   b ). The bearing assembly  42  includes a bearing surface  54  to permit the rotation of the chamber about the midpoint and a locking assembly  56  to lock the chamber in any position between vertical and horizontal with respect to the frame and the stationary horizontal base. The locking mechanism may be any device known to those skilled in the art for restraining the movement of the chamber with respect to the stationary horizontal base. Such locking mechanisms may include but are not limited to clamps, springs, thumb screws, levers and the like. The stationary horizontal base  40  can be constructed of materials selected from the group consisting of stainless steel, corrosion resistant alloy, metals having a fluoropolymer coating, and mixtures thereof. 
         [0027]    Referring to  FIG. 4 , a multi-chamber installation is shown wherein 4 chambers  10  are supported as described hereinabove on a multi-chamber base  60 . Each of the 4 chambers can be independently positioned between vertical and horizontal alignment for loading, unloading and maintenance from either the proximal or the distal end of the chamber. One embodiment of a multi-chamber apparatus for performing flash chromatography of the present invention comprises two or more of the modular apparatus disposed adjacent one to another. The multi-chamber apparatus can have any number of chambers supported by a multi-chamber base. Preferably, the multi-chamber apparatus for performing flash chromatography of the present invention comprises from 2, 3, 4, 5, 6, 7 or 8 chambers. 
         [0028]    Referring to  FIG. 5 , a stationary phase adsorbent cartridge  100  is shown. The stationary phase adsorbent cartridge  100  is adapted to be removably disposed within the hollow cylindrical interior  2  of the chamber  10  (See FIG.  2   a ). The stationary phase adsorbent cartridge  100  has a cylindrical outer wall  120  and includes a first porous frit plate  110  sealingly disposed at the proximal end and a second porous frit plate  112  sealingly disposed at the distal end defining a hollow cartridge interior  116 . A porous support plate  114  is disposed over the frit plate  110  on the distal end and at the proximal end to support the weight of the stationary phase adsorbent disposed in the hollow cartridge interior  116  and to provide structural stability to the stationary phase adsorbent cartridge  100 . The frit plates  110  are made of high density polyethylene, HDPE, having a 35 micron pore size (depth filters) to prevent particles from entering the adsorbent cartridge. The porous support plate  114  is a perforated plate disposed at the proximal and distal ends of the cartridge to enhance the flow distribution through the cartridge. The porous support plate  114  can be made of high density polyethylene. A stationary phase adsorbent is disposed in the hollow cartridge interior  116 . Additional spacers (not shown) may be disposed in the hollow cartridge when the stationary phase adsorbent does not completely fill the cartridge interior. A portion of the cylindrical outer wall  120  extends beyond the porous support plate forming a raised proximal ring  122  and a raised distal ring  124 . The raised proximal ring and the raised distal ring optionally may chamfered where they contact the gasket. The raised proximal ring  122  is positioned within the sealing channel  35  of the proximal cover plate and the raised distal ring is positioned within the sealing channel of the distal cover plate when the cartridge is disposed in the chamber. When the stationary phase adsorbent cartridge  100  is disposed in the hollow cylindrical interior  2  of the chamber, the stationary phase adsorbent is in fluid communication with the hollow cylindrical interior  2  and the inlet and outlet nozzles  28  and  28 ′. The cylindrical outer wall  120  can be composed of polypropylene piping and is available in many different SDR Ratings. SDR 07 (230 psi) SDR 11 (150 psi/10.5 atmospheres), SDR 17 (88 psi/6.2 atmospheres), and SDR 33 (47 psi/3.3 atmospheres). A cylindrical outer wall comprising SDR 33 polypropylene pipe is preferred. The SDR or “Standard Dimension Ratio” is used by many pipe manufacturers as a method of rating pressure piping. SDR is a ratio of pipe diameter to wall thickness. The diameter of the cartridge may be of any size, but preferably between about 25 cm to 40 cm, more preferably between about 30 to 36 cm. 
         [0029]    With reference to  FIG. 6 , a top view of the porous support plate  114  (See  FIG. 5 ). The porous support plate  114  has a plurality of perforations  118  extending through the porous support plate and distributed uniformly about the porous support plate. 
         [0030]    In practice, a flash chromatography process, or flash chromatography, employs a compressible fluid as a mobile phase, to elute the sample containing a compound(s) of interest. More than one compressible fluid can be used, e.g., a mixture. Suitable compressible fluids include, for example, carbon dioxide, water, ammonia, nitrogen, nitrous oxide, methane, ethane, ethylene, propane, butane, n-pentane, benzene, methanol, ethanol, isopropanol, isobutanol, monofluoromethane, trifluoromethane, dimethyl sulfoxide, acetonitrile, hydrofluorocarbons, chlorotrifluoromethane, monofluoromethane, hexafluoroethane, 1,1-difluoroethylene, 1,2-difluoroethylene, toluene, pyridine, cyclohexane, m-cresol, decalin, cyclohexanol, O-xylene, tetralin, aniline, acetylene, chlorotrifluorosilane, xenon, sulfur hexafluoride, propane or a combination thereof. 
         [0031]    A preferred compressible fluid is carbon dioxide, because it is nontoxic, inexpensive and widely available, as long as the sample requiring separation has some solubility in carbon dioxide. 
         [0032]    The mobile phase may also contain a cosolvent, such as an organic solvent. A suitable solvent is chosen based on the polarity of the materials being separated and to increase the solubility of the sample in the compressible fluid. Preferably, the amount of cosolvent is less than 50 wt. %, based on the weight of the compressible fluid and cosolvent mixture combined, more preferably less than 40%, less than 30%, less than 20%, or even less than 10%. It is possible that no cosolvent will be required, although typically at least a small amount is necessary, e.g., about 1-10%, to improve solubility of the sample in the compressible fluid. One skilled in the art can easily select a suitable solvent based on the characteristics of the sample. 
         [0033]    The mobile phase may be comprised of a single mobile phase, or more than one mobile phase, e.g., two or more mobile phases, such as three or four. The composition of the mobile phase or phases is determined by the required solvent strength of the mobile phase. Typically, the more polar the solvent mixture, the more polar the compounds that are separated, as would be understood by one skilled in the art. The compressible fluid and cosolvent can be delivered to the pressurized vessel in a mixed stream or in separate streams, according to the needs of the user. 
         [0034]    The mobile phase is passed through a pressurized vessel containing an adsorption material, the vessel being pressurized to maintain the compressible fluid at the appropriate pressure. In one embodiment, the sample is first loaded into the pressurized vessel before the mobile phase is added, for example, if the sample is very viscous. In another embodiment, the sample can be premixed with the mobile phase, and the mixture is then loaded in the pressurized vessel. In yet another embodiment, the sample is dissolved in a solvent and introduced into the stream of the cosolvent prior to mixing the compressible fluid with the cosolvent. The solvent can be the same as or different from the cosolvent used in the mobile phase. In another embodiment the sample is injected into the mobile phase. 
         [0035]    The present invention in various modes of operation results in rapid equilibration which means that there is very little time required between runs and the next injection can be almost immediately. Unfortunately, in normal phase HPLC, there is significant time spent equilibrating the column before the next run is started. 
         [0036]    Suitable chromatography adsorption materials include silica-based materials, such as silica, silica gel or alumina of regular or irregular shape, and other column packing materials known to those skilled in the art of chromatography. A preferred packing material is silica. 
         [0037]    Typical packing material in standard flash chromatography includes highly porous, irregular particles of sizes greater than 50 microns. Smaller particles can be used in the present invention than in traditional LC, HPLC or flash chromatography because there is a lower pressure drop from the top of the column to the bottom of the column, resulting from a less viscous mobile phase with higher diffusivities. Preferably, the particle size of the adsorption material used in the present invention ranges between about 10 to about 500 microns, more preferably, the particle size of the adsorption material used in the present invention ranges between about 10 to about 200 microns.