Abstract:
A chromatography column includes a tubular member with an inlet end and a slidable porous member that bounds a chromatography media. The porous member is spaced sufficiently from the inlet end to define a receiving region.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. patent application Ser. No. 09/137,278, filed Aug. 20, 1998, now U.S. Pat. No. 6,139,733, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to introducing a sample into a chromatography column. 
     Liquid chromatography is a technique for separating the individual compounds that exist in a subject sample. In employing the technique, the subject sample is carried in a liquid, called a mobile phase. The mobile phase carrying the subject sample is caused to migrate through a media, called a stationary phase. Different compounds will have differing rates of migration through the media, which effects the separation of the components in the subject sample. Liquid chromatography is commonly performed with reusable columns or with disposable cartridges, both of which are usually cylindrical, in which the media bed is bounded axially by porous plates, or plates containing defined flow paths, through which the mobile phase will flow. (See U.S. Pat. No. 4,250,035 to McDonald et al. and U.S. Pat. No. 5,601,708 to Leavesley) 
     When chemists optimize liquid chromatographic separations conditions, they may need to dissolve the sample mixture in a dissolution solvent which may be nonideal for elution. This can result in poor separation and poor recovery of desired components. 
     One solution to this problem is to pre-absorb the sample onto a media prior to chromatography. This involves dissolving the sample mixture in a suitable solvent and adding an amount of a dry media (usually similar to the media being used for the separation) to this solution. The dissolution solvent is then evaporated off, usually using a rotary evaporator, leaving the sample mixture dry, and absorbed to the media. The pre-absorbed media is then placed at the head of a pre-packed glass, metal or plastic chromatography column, and the optimized chromatographic solvent would flow through the pre-absorbed media and then through the column of separation media. This method has the potential hazard of the operator coming into contact with the dry powdery media both before and after the addition of the sample. This method also can lead to poor separations and recovery. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention features, in general, a chromatography sample module including a flow-through member having an inlet and an outlet and chromatography media within the flow-through member. A sample is added to the media, and the module, with the sample carried therein, can then be connected to a separation column. 
     Preferably the chromatography sample module is a tubular member that is sized to fit within the end of a chromatography column that is used for separation of the sample contained on the media in the module. Alternatively, the module can be connected to the chromatography separation column by a flow line. The sample in the dissolution solvent can be added to the sample module, and then the dissolution solvent can be evaporated. Alternatively, the sample in the dissolution solvent can be added to the sample module as a liquid without evaporation. 
     In another aspect the invention features a rack of sample modules arranged in an array. 
     Embodiments of the invention may include one or more of the following advantages. The samples can be easily introduced into separation columns. Various solvents can be used for separation and dissolution of the sample, permitting optimization of the separation procedure. Samples are easily preprocessed, and the operator is not exposed to the media before or after adding the sample. A large number of samples can be prepared for processing at one time, facilitating the carrying out of multiple separations at one time. 
     Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of a chromatography system according to the invention. 
     FIG. 2 is a vertical sectional view of a chromatography sample module used in the FIG. 1 system. 
     FIG. 3 is a plan view of a rack containing a plurality of the FIG. 2 sample modules in an array. 
     FIG. 4 is an elevation of the FIG. 3 rack and modules. 
     FIG. 5 is a vertical sectional view showing the FIG. 2 sample module in position between a sealing head and a chromatography column used in the FIG. 1 system prior to assembly. 
     FIG. 6 is a vertical sectional view showing the FIG. 5 components in an assembled and sealed state. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, there is shown chromatography system  10  which includes a source of solvent  12 , pump  14 , sample module  16 , liquid chromatography column  18 , and sample collection vessel  20 . In this system, the sample to be analyzed is preabsorbed onto media in sample module  16  prior to pumping solvent into module  16  and into chromatography column  18  to perform the separation procedure. 
     Referring to FIG. 2, it is seen that sample module  16  includes cylindrical plastic tube  22 , porous plates  24 ,  26  (made of inert plastic porous frits), and chromatography media  28  (only partially shown in the figures) between porous plates  24 ,  26 . 
     As appears from FIGS. 5 and 6, sample module  16  is designed to fit within chromatography column  18  at the entrance thereof and to be sealably connected to the sealing head. Tube  22  is designed to fit within column  18  with minimal space between the two; in particular, there is 0.000″ to 0.010″ of radial clearance. 
     Sample module  16  can be filled with media that is the same as or is different from the media of chromatography column  18 . The sample is dissolved in the required solvent and added to the top of sample module  16 , where it is drawn into the media by capillary action. This dissolution solvent is then removed by placing sample module  16  in a vacuum chamber. Heat may also be applied. 
     After sample module  16  has dried, it can be placed directly inside separation column  18  so that the lower porous plate  26  is an in intimate contact with the surface of the separation media or with a porous plate within the separation column on top of the separation media. 
     Alternatively, sample module  16  can be placed in a remote tube connected by a solvent line. Alternatively, the sample can be dissolved in a separation solvent or a weaker solvent), and added to module  16 . The wet module can then be loaded into the column or into a remote tube. 
     Examples of the types of complex samples where this technique has particularly advantageous use include synthetic organic reaction mixtures and natural product extracts, (e.g., from fermentation broths or plants). These samples often need to be dissolved in a solvent not compatible with the optimized separation solvent. Solvents are organized according to their “solvent strength,” where hexanes have a value close to zero, and methanol has a value of 0.95. Optimized separation eluents often have a lower solvent strength; e.g., hexane:ethylacetate 1:1 has a solvent strength of 0.295. If the sample needs to be dissolved in a strong solvent such as methanol, there will be a solvent strength difference of 0.655 seen initially after loading the sample onto the column, and this will impair the separation of the sample. If the sample dissolved in methanol is instead preadsorbed to the media in the sample module and dried, the sample will not face this impairment during separation. 
     Referring to FIGS. 3 and 4, sample modules  16  can be supplied in racks  32 , and a whole rack of sample modules  16  can be efficiently prepared at one time rather than one at a time. 
     FIGS. 5 and 6 show the placement of a module  16  in a column  18  and the sealing of the module  16  and column  18  to a sealing head used to deliver solvent. Sealing head  110  has first head piece  112 , second head piece  124 , intermediate head piece  128 , and first and second annular elastomeric sealing members  134 ,  136 . 
     First head piece  112  has body  114  with longitudinal axis  116 . First head piece  112  has outwardly extending shoulder  118 , and contact face  120 . Part of contact face  120  has a slightly conical shape or other concavity. First head piece  112  defines flow path  122  along axis  116 . 
     Body  114  of first head piece  112  fits slidably through central openings in second head piece  124 , intermediate head piece  128 , and first and second elastomeric sealing members  134 ,  136 . 
     Second head piece  124  has outwardly extending compression member  146 . Intermediate head piece  128  has narrow portion  148  distal from second head piece  124 . 
     First elastomeric sealing member  134  is adjacent to both shoulder  118  and narrow portion  148  of intermediate head piece  128 . Second elastomeric sealing member  136  is adjacent to both intermediate head piece  128  and second head piece  124 . 
     The outer diameter of tube  22  of sample module  16  is sized so that tube  22  fits into column  18 . The inner diameter of tube  22  is sized so that it may slidably receive shoulder  118 , first elastomeric sealing member  134 , and narrow portion  148  of intermediate head piece  128 . 
     Intermediate head piece  128 , second elastomeric sealing member  136 , and second head piece  124  are sized to fit slidably into column  18 , having chamfered edges  140 , filled with chromatography separation media  142 , which is bounded axially by porous plates  144 . 
     Referring to FIG. 6 seals are formed with the apparatus by inserting sample module  16  into column  18  so that second porous plate  26  abuts first porous plate  144 . Referring to FIG. 5, sealing head  110  is then inserted into column  18  and tube  22  of sample module  16 , so that shoulder  118 , first elastomeric sealing member  134 , and narrow portion  148  are within tube  22 , and contact face  120  abuts porous plate  24 . Sealing head  110  extends far enough into column  18  so that second elastomeric sealing member  136  opposes the inner surface of column  18 . 
     Downward compressive force applied to outwardly extending compression member  146  causes second head piece  124  to slide relative to first head piece  112  and transmits compressive force to second elastomeric sealing member  136 , intermediate head piece  128 , first elastomeric sealing member  134 , shoulder  118 , porous plate  24 , sample module media  28 , porous plate  26 , porous plate  144 , and separation media bed  142 . The compressive force causes first and second elastomeric sealing members  134 ,  136  to expand radially so that first elastomeric sealing member  134  forms a seal with tube  22 , and second elastomeric sealing member  136  forms a seal with column  18 . 
     The seals are released by relaxing or removing the downward force to second head piece  124 , thereby reducing the compressive force on the components of sealing head  110  and reducing the radial expansion of elastomeric sealing members  134 ,  136 . 
     Preferably, tube  22  and column  18  are made of high-density polyethylene. However, the columns may be constructed of other materials, including glass or stainless steel. Preferably, elastomeric sealing members are made of a fluorocarbon polymer, such as that sold under the trade name CHEMRAZ. 
     Other embodiments of the invention are within the scope of the following claims.