Apparatus for pressurizing a removable chromatography cartridge

Chromatography apparatus including an enclosure having a pressurizable chamber sized to removably receive a chromatography cartridge therein and an opening to the chamber, and a cap that closes the opening and has a flow passage for directing a sample to be analyzed to the cartridge, the cap having a sharp protruding member that surrounds the flow opening and makes sealable engagement with the cartridge by digging into the cartridge.

BACKGROUND OF THE INVENTION 
The invention relates to apparatus used to pressurize a removable 
chromatography cartridge. 
In chromatographic procedures, a stationary phase such as a surface active 
powder is contained in a chromatography column. A mobile phase consisting 
of a carrier fluid and a sample of chemical to be identified, analyzed, or 
purified is passed through the column. Different components of the sample 
pass through the column at different rates and are thereby separated from 
each other, leaving the column at different times. 
Voids in the stationary phase that may have resulted during shipping and 
other nonuniform packing conditions can deleteriously affect the operation 
of a chromatography column and the accuracy of the results. It is known to 
compress flexible-walled columns in order to close voids and provide 
uniform packing of the stationary phase. E.g., in U.S. Pat. No. 4,250,035, 
a chromatography column is made of polytetrafluoroethylene (PTFE) tubing 
sealed at the ends with porous frits. In one embodiment, the column is 
placed within a chamber that is pressurized to compress the deformable 
walls of the column and the stationary phase therein. This provides a 
uniform packing of the stationary phase and promotes the accuracy of the 
chromatography column. 
It is also known to make a chromatography cartridge from polyethylene, or 
like material, and to mount the cartridge in a pressurizable compression 
module assembly having an outer cylindrical body and an end cap that has 
an O-ring around its outer surface for providing a seal with the end of 
the cartridge. The O-ring is made of resilient, flexible material, so as 
to provide a good seal, and is chemically-resistant, to reduce interaction 
with the mobile phase chemicals. Nevertheless, this O-ring may shrink or 
swell, leach compounds into the column or absorb the sample. 
SUMMARY OF THE INVENTION 
The invention features, in general, chromatography apparatus that includes 
an enclosure having a pressurizable chamber for receiving a chromatography 
cartridge therein and a cap for closing an opening to the enclosure. The 
cap has a sealing structure for mating with the enclosure and providing a 
seal to the enclosure around the opening. The cap also has a flow passage 
for directing a sample to be analyzed to the cartridge therein. The cap 
also has a sharp protruding member that surrounds the flow passage, is 
inside of the cap sealing structure, and is directed toward the chamber 
for making sealable engagement with the cartridge by digging into the 
cartridge. The sharp protruding member provides a reliable, long-lasting 
sealing structure that can be repeatedly used to make seals with removable 
chromatography cartridges without employing an O-ring, which can wear in 
use and will need to be replaced at significant expense. 
In preferred embodiments, the apparatus has a mechanism to force the sharp 
protruding member into the wall of the cartridge. This mechanism can be 
provided by camming surfaces on the enclosure and the cap and a V-band 
that engages both camming surfaces and brings the enclosure and cap 
together as the band is tightened. The chromatography cartridge has a 
porous frit in a recess therein, and the cap has a plug portion sized to 
contact the frit. The sharp protruding member is preferably angular in 
section with two converging lines meeting at a point, the lines making an 
angle of between 20.degree. and 120.degree. (most preferably, between 
50.degree. and 90.degree.). The protruding member preferably extends 
between 0.03" and 0.15" (most preferably between 0.05" and 0.10"). The 
enclosure preferably is cylindrical and has a pressure inlet for 
connecting to a source of pressurized liquid and a pressure relief valve. 
Other advantages and features of the invention will be apparent from the 
description of the preferred embodiment thereof and from the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the figures, chromatography apparatus 10 includes outer barrel 
12, end caps 14, 16, and removable chromatography cartridge 18 within 
barrel 12 and between end caps 14, 16. Barrel 12 has pressure relief valve 
20 in an opening to inner chamber 22. Barrel 12 acts as an enclosure for 
receiving and pressurizing cartridge 18 therein. 
At both ends of barrel 12 are outer, annular recesses 24 and flanged ends 
26 having inclined camming surfaces 28. End caps 14, 16 have mating 
flanges 30 with oppositely inclined camming surfaces 32. Flanged ends 26 
also have an axially-directed annular recesses 34 containing sealing rings 
36 therein. V-band 38 has inclined surfaces 40, 42 engaging camming 
surfaces 28, 32, respectively. V-band clamping knob 44 increases the 
tension in V-band 38, and, in so doing, biases end cap 16 axially toward 
barrel 12. 
Chromatography cartridge 18 includes cylinder 46 made of food-grade, 
medium-density polyethylene and has a nominal inner diameter of three 
inches. Stationary phase media 48 is contained within cylinder 46 between 
thin porous frits 50, 52 and thick frits 54, 56, respectively. Frits 50 
and 54 are received within inwardly directed annular recess 58, and frits 
52 and 56 are received within inwardly directed annular recess 60. 
Cylinder 46 extends beyond frits 54, 56 and has diverging, inner conical 
surfaces 62, 64. End caps 14, 16 each have plug portions 66 with outer 
conical surfaces that mate with surfaces 62, 64 of cartridge 18. 
Just outside of plug 66, each flange 30 has sharp protruding member 68 
having a radius equal to the radius at the midsection at the end of the 
wall of cylinder 46. End caps 14, 16 are made of metal, and the ends of 
protruding member 68 are sharp so that they dig into the ends of the 
polyethylene cylinder 46 when force is applied to bring caps 14, 16 toward 
barrel 12 by V-bands 38. Referring to FIG. 3, it is seen that protruding 
member 68 makes a 60.degree. angle in section and protrudes downward from 
surface 70 by 0.060"-0.065". Other angles (e.g., 20.degree. to 
120.degree., preferably 50.degree. to 90.degree.) and distances (e.g. 
0.03" to 0.15", preferably 0.05" to 0.10") could work. End caps 14, 16 
also have flow passages 72, 74 through them. Passage 72 communicates with 
process inlet 76, and flow passage 74 communicates with process outlet 78. 
In use, chromatography cartridge 18 can be installed in barrel 12 and 
easily removed and replaced with another cartridge when it is necessary to 
change to a different or new chromatographic media. A variety of 
stationary phase media may be used in the cartridges. The most commonly 
used are reverse phase, normal phase, ion-exchange, and size-exclusion 
packings. 
When a new cartridge 18 is installed, it is inserted into barrel 12, and 
end caps 14 and 16 are moved into position. V-bands 38 are placed around 
flanged ends 28 and flanges 30 and are tightened with V-band clamping 
knobs 44. As V-bands 38 are tightened, flanged ends 28 and flanges 30 come 
closer together, compressing O-rings 36, and causing protruding members 68 
to dig into the ends of cylinder 46. Because protruding members 68 are 
made of metal, they dig into the softer polyethylene cylinder 46. 
Protruding member 68 and side surface 70 is spaced with respect to the 
bottom of plug portions 66 so that the inner surfaces of plug portions 66 
contact thick frits 54, 56 when flanged ends 28 and flanges 30 have been 
brought together. Protruding sealing member 68 provides a good seal 
between end caps 14, 16 and cylinder 46 without the need for O-rings with 
chemically resistant properties at these locations. 
After cartridge 18 has been installed, chamber 22 is pressurized, via an 
opening not shown on the drawings, and the increased pressure compresses 
the walls of flexible polyethylene cylinder 46, providing uniform packing 
for the stationary phase media therein. A source of sample in a carrier 
liquid is connected to process inlet 76, and liquid leaves enclosure 12 
via process outlet 78. 
Other embodiments of the invention are within the scope of the appended 
claims. E.g., in place of V-band 38, other mechanisms could be used to 
hold end caps 14, 16 in place and bring them together. Also, other 
geometries could be used for protruding member 68.