Refillable column for chromatography at elevated pressure

A refillable column for chromatography at elevated pressure is described comprised of a cylinder connected on both ends to a coupling having internal threads and an annular shoulder at the internal terminus of the threads. A plug having external threads is disposed in said coupling and sealed against the shoulder of the coupling. An axial hole communicates between the top and bottom of the plug. The column can be packed, emptied and repacked repeatedly.

BACKGROUND OF THE INVENTION 
Field of the Invention 
This invention relates to a novel refillable column for chromatography at 
elevated pressure. More specifically, this invention comprises a device 
which can be repeatedly packed with a chromatographic material, emptied of 
such material when it is exhausted, or it is desired to employ a different 
material, and repacked with a fresh adsorbent by one of ordinary skill in 
the chromatographic art. 
Prior Art 
The process known as chromatography is old in the chemistry art. It is a 
means for separating chemical compounds, especially closely related ones, 
by allowing a solution of a mixture to seep through, or along, an 
adsorbent medium so that each compound becomes adsorbed in a separate 
layer, section, or portion of the adsorbent. 
The chromatographic art has evolved steadily and, at times, dramatically 
from the early process known as open column chromatography to the highly 
sophisticated and useful chromatographic processes at elevated pressure 
commonly utilized today. Chromatography under pressure aids in the 
definitive separation of minute quantities of very closely related 
chemical compounds. In some instances pressure as great, or greater, than 
100 atmospheres are employed in the process. For example, the analysis of 
blood to identify metabolites of physiologically active agents, which may 
be present in quantities measured in parts per billion, is often carried 
out at pressures of 1500 to 2000 psig, or higher. 
A large number of highly refined adsorbents are available for use in high 
pressure chromatography. One, and not infrequently, a plurality of 
adsorbents is packed into a column providing a bed of adsorbent material 
having a length, or depth, several times greater than its cross-section 
(generally, diameter). The fluid mixture (solution) of the compounds 
desired to be separated is slowly percolated through the adsorbent bed. 
The pressure on the adsorbent bed can range from one to many atmospheres. 
The pressure can be varied by applying pressure, as with a pump, at the 
inlet to the column and restricting the rate of flow at the outlet from 
the column. 
All sorts and varieties of columns for chromatography at elevated pressure, 
both packed with adsorbent and unpacked, are commercially available. Many 
of the pre-packed columns are not reuseable. Once the adsorbent has been 
exhausted (or poisoned) the column is no longer useful and must be 
replaced. Moreover, when a different adsorbent is desired, or needed, an 
entirely new column must be employed. 
Some of the unpacked columns available commerically which can be packed by 
the user become single application columns once they are packed because 
they cannot be emptied and repacked because of their design. 
Some of the refillable columns for chromatography at elevated pressure 
which are available are so designed that skilled hands are required to 
achieve an effective seal after the column has been repacked. Consequently 
the emptying and repacking of such columns is slow, cumbersome and 
expensive because of the level of skill required to satisfactorily 
accomplish the refilling operation. 
Accordingly, it is an objective of this invention to provide a refillable 
column for chromatography at elevated pressure that can be readily 
emptied, repacked with the same or different adsorbent and resealed 
positively against pressure leaks with a minimum of time and skill. 
SUMMARY 
Now it has been discovered that a positively resealable refillable column 
for chromatography at elevated pressure can be comprised of a cylinder 
having a length to diameter ratio of 2:1 or more connected at each end to 
a coupling having internal threads and an annular shoulder at the internal 
terminus of the threads with a plug having external threads mated to the 
internal threads of the coupling disposed therein, said plug also having a 
depending extension adapted to contact the annular shoulder of the 
coupling achieving a seal therewith and an axial hole communicating 
between the bottom and top of the plug.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following detailed description of the embodiments of this invention, 
reference is made to the accompanying drawings. 
One embodiment of the instant invention is a refillable column for 
chromatography at elevated pressure depicted in FIGS. 1-4. Such a device 
is comprised of: (a) a cylinder having a first and a second end with a 
length exceeding the diameter by a factor of 2 or more. Such a cylinder is 
connected at each end to a coupling having internal threads, preferably 
machine, of an inside diameter greater than that of said cylinder at the 
point of connection between said coupling and said cylinder and 
additionally having an annular shoulder disposed at the internal terminus 
of said threads. (b) A resilient plug having external threads, preferably 
machine, adapted to mate with the internal threads of the coupling is 
disposed therein. The plug has an inwardly tapered extension depending 
from said threads which is adapted to contact and cooperate with the 
annular shoulder of said coupling and form a seal therewith. The extension 
also has an inwardly and upwardly tapered bottom. The plug also has an 
axial bore with internal threads, preferably machine, disposed in the end 
opposite said extension and an axially disposed hole communicating between 
the bottom of said bore and the bottom of said extension. And, (c) a 
bushing having external threads, preferably machine, adapted to engage the 
internal threads of said bore is disposed therein. The bushing has an 
axial hole communicating between the top thereof and the axial hole in 
said plug. A tubular extension of said axial hole adapted to receive a 
flexible tube is connected to the top of said bushing. 
Referring to FIG. 1, there is seen a refillable column for chromatography 
at elevated pressure of this invention with a safety shroud 6 in place. 
The safety shroud constitutes no part of the instant invention and will 
not be discussed further. Those skilled in the art recognize the purpose 
such a shroud 6 serves. 
The cylinder which holds the chromatographic material is shown as 1. In 
this rendering the cylinder is shown as having a body several times the 
diameter of the couplings 2 connected to both ends thereof. In this case 
the cylinder tapers gradually from the body thereof into the connections 
with the couplings 2. In most cases the body of the cylinder 1 will have a 
diameter greater than the diameter of the couplings 2. This is so because 
the rate of flow through the chromatographic material is relatively slow 
and does not require a large inlet and outlet to accomodate the fluid 
flow. However, the cylinder 1 need not be greater in diameter than the 
couplings 2. But there is generally no useful purpose served by having a 
cylinder of a lesser diameter than the couplings because the volume of the 
column can be better controlled by adjusting the length to the diameter to 
achieve the volume desired to contain the quantity of chromatographic 
material needed for the separation of the various compound in the solution 
passing through the column. For all practical purpose the length of the 
cylinder should exceed the diameter by a factor of 2, or more. 
At the bottom of FIG. 1 and in FIG. 2 it is shown that both the outside and 
inside diameters of the couplings 2 are greater than the cylinder 1. This 
is an essential element of the construction which is discussed more 
throughly later. 
In FIG. 1 there is a knurled nut shown which is a part of resilient plug 3. 
The knurling is for convenience only in installing and removing plug 3 
from coupling 2. A bushing 4 with a tubular extension 5 is shown disposed 
in plug 3. It is to be noted that in FIG. 1, both ends of the cylinder are 
identical. This is a convenient construction. But identical construction 
as to size is of no consequence in the invention. However, both ends of 
the cylinder do have couplings, plugs and bushings of similar construction 
so that the same condition obtain and the same purpose is achieved. 
FIG. 2 clearly shows the crux of the instant invention. Coupling 2 has an 
annular shoulder 15 just above the point of connection with the cylinder. 
This annular shoulder 15 serves as a seat which is contacted by the 
extension 16 of plug 3 which depends below the external threads 8 shown in 
FIG. 3. The coupling 2 has internal threads 12 which mate with the 
external threads 8 of the plug 3. When plug 3 is disposed in coupling 2 
and tightened down so that the extension 16 of plug 3 contacts the annular 
shoulder 15 of coupling 2 a pressure tight seal is formed. 
In order to obtain the pressure tight seal the angles 9 and 10 shown on 
plug 3 in FIG. 3 aid in effecting the seal. The extension 16 depending 
from the terminus of the external threads 8 or plug 3 is preferably 
tapered inwardly at an angle 10 of from about 1.degree. to about 
15.degree.. This allows the extension 16 to clear the inside wall of the 
coupling below the annular shoulder 15 thereof and establish a firmly 
sealed contact therewith. The inwardly and upwardly tapers of the bottom 
of plug 3, angle 9, provides yield for the compression of the extension of 
plug 3 as the bottom is tightened against the annular shoulder 15 of 
coupling 2. Angle 9 should preferably be from about 5.degree. to about 
25.degree. to achieve the needed yield. Those skilled in the art will 
recognize that the greater the diameter of the extension of plug 3 the 
greater the taper of angle 9, for a shallow angle 9 coupled with a 
substantial diameter will reduce the yield of the resident plug and make 
the establishment of a tight seal more difficult. 
The bore 11 is shown clearly in FIG. 3. The axial hole 17 communicates 
between the bottom of plug 3 and the bottom of bore 11 is plug 3. 
Bushing 4 is shown in FIG. 2 disposed in bore 11. The internal threads in 
bore 11 are shown as 13 and the external threads of bushing 4 are shown as 
14. Extending upwardly from bushing 4 and communicating with axial hole 18 
in bushing 4 is a tube 5 adopted to receive a flexible connection. 
The complete assembly shown in FIG. 2 depicts the axial hole 17 in plug 3, 
the axial hole 18 in bushing 4 and the hole in tube 5 in alignment and 
communicating between an external inlet and the interior of the cylinder 
of the refillable column for chromatography at elevated pressure of this 
invention. 
FIG. 4 is a blown up section from FIG. 1 showing the top portion of the 
column 1 and shroud 6. A split collar 7 holds the shroud around column 1. 
The interior opening in the split collar reposes on the outside diameter 
of the annular collar of coupling 2 and the shroud 6 is held on the split 
collar 7 by an internal flange with an outside diameter slightly less than 
the inside diameter of the shroud. The shroud is clamped to a laboratory 
support to hold column 1 in a vertical altitude. 
In another embodiment of this invention all of the elements are the same as 
those described above except that no bushing 4 is utilized and instead of 
a bore 11 in plug 3, the axial hole 17 therein is continued to the top 
thereof and communicates with a tubular extension such as 5 shown on 
bushing 4. Column 1 is connected to couplings 2 which in turn have 
modified plugs 3 disposed therein. 
The benefit achieved by the refillable column for chromatography at 
elevated pressure of the instant invention lies in the fact that the 
column can be refilled repeatedly with a chromatographic material, such as 
finely ground attapulgite, silica gel, montmorrilnite, kaolin, and the 
like. There is no need to discard the entire column when the 
chromatographic material contained therein is exhausted. A tight seal is 
easily and routinely obtained after refilling. 
Ordinarily, the cylinder will be a transparent material such as glass. 
This, however, is not a requirement. Other materials of construction can 
be utilized, such as polyacrylic, polymethacrylic, polycarbonate and other 
synthetic polymeric material. Generally, opaque metals are not preferred 
because there is no way to visually determine the zones of adsorbancy. 
The refillable columns for chromatography at elevated pressure detailed 
above are prepared for use by placing in one end a filter material 
designed to hold the chromatographic material, such as glass wool, 
asbestos, felt, paper, and the like. Then a slurry of the desired 
chromatographic material is slowly introduced into the other end of column 
and as the vehicle drains from the open lower end of the column, the bed 
of chromatographic material is slowly built up until the desired quantity 
of material is contained in the column. The plugs, and bushings if they 
are used, are inserted in the couplings and tightened to effect a pressure 
tight seal. The bed of chromatographic material is then conditioned in a 
manner known to those skilled in the art and appropriate for the use to 
which the column is to be put. Such a refillable column for chromatography 
at elevated pressure is useful for running chromatographic separation at 
pressures from about 1 to about 400 psig depending on the diameter of the 
cylinder, the material of construction of the cylinder, and the other 
parts which constitute the column. Those skilled in the art will recognize 
the maximum safe pressure to which a particular sized column constructed 
of a particular material can be operated. 
The resilient material from which the plugs can be made include such 
diverse polymeric substances as polytetrafluoroethane, 
polychlorofluoroethane, polyethylene, polypropylene, nylon, modified 
acrylic and methacrylic polymers, and the like. Preferred for its 
inertness is polytetrafluoroethane. However, those skilled in the art will 
recognize the degree of inertness required by the character of the 
chromatographic separation contemplated and can select other materials of 
equal utility where adequate chemical inertness is present. 
The bushing can be constructed of any material suitable for withstanding 
the pressure employed, and the solvent system utilized. The plastic 
materials noted in the paragraph above as well as such metals as brass, 
monel, stainless steel, and the like can be used. Care must be exercised 
in installing the bushing in the resilient plug to effect a solid seal 
between the bottom of the bushing and the bottom of the bore in the plug. 
The preferred construction of the coupling and the cylinder is of glass. 
When such a construction is utilized a coupling available in commerce can 
be connected to the cylinder of the column by drawing the end of the 
cylinder to the same outside diameter as that of the coupling and joining 
the two pieces together by a simple glass blowing procedure, a procedure 
well known to those skilled in the art.