Chromatography column

A chromatography column adapted for high pressure chromatography is characterized by a tubular membrane separating a glass tube from the pressurized area between the glass tube and a pressure tube adapted to receive a pressurizing fluid. Changing of the glass tube is facilitated by annular seals at each end of the glass tube against which an adjustable threaded plug, fitted in one of a pair of screw caps fitted on each end of the pressure tube, exerts sealing pressure.

BACKGROUND OF THE INVENTION 
This invention relates to a column adapted for high pressure liquid 
chromatography of the type having a glass column adapted to be filled with 
the sorbent and which is surrounded concentrically, with an intermediate 
space being maintained therebetween, by a pressure tube. 
Such columns are known, for example, from German Utility Model No. 
7,146,039, German Offenlegungsschrift No. 2,329,286 and German 
Auslegeschrift No. 2,524,751. In these known columns, the intermediate 
space between the glass column and the pressure tube is filled with the 
eluent, as the pressure liquid, used for the chromatographic separation by 
connecting the intermediate space to the eluent feed, so that the pressure 
acting externally on the glass column is the same as or greater than that 
inside the column and the glass column thus cannot explode from the 
pressure of the eluent. 
It has been proposed to seal off the intermediate space from the ends of 
the column so that the eluent contained in the intermediate space cannot 
mix with the eluent entering at the top of the column. In German 
Offenlegungsschrift No. 2,329,286, this is achieved by sealing off the 
ends of the column from the intermediate space with O-rings, which has the 
disadvantage that the glass column must be matched precisely to the length 
of the pressure tube, with minimum tolerance. 
It is thus proposed in German Auslegeschrift No. 2,524,751 to seal off the 
glass column from the intermediate space with a seal of the stuffing box 
type, whereby even relatively large differences in length of the glass 
column can be tolerated. Polytetrafluoroethylene seals are used as the 
stuffing box-type seals. Although these seals are resistant towards the 
eluent present in the intermediate space, they have a relatively low 
elasticity, so that the diameter tolerances of the glass column to be 
compensated by the seals are small. These stuffing box-type 
circumferential seals also make it very difficult to change the glass 
column. More specifically, in order to change the column, the screws at 
both ends of the pressure tube must be undone and at least one of the two 
such seals, which have been pressed firmly onto the glass tube, must be 
removed so that the glass column can be pulled out of the pressure tube. A 
further disadvantage of this construction is that a free space must be 
provided between the end of the column and the screw connection of the 
pressure tube in order to compensate for length variations in the glass 
column. This means that the column is not firmly clamped in the 
longitudinal direction, so that leaks in the inflow and outflow 
capillaries, which necessarily fit in only relatively loosely, can very 
easily result. 
It is an object of this invention to prove a column for high pressure 
liquid chromatography which uses simple head seals which permits easy 
change of the glass column and which permits the use of glass columns with 
relatively large variations both with respect to diameter and with respect 
to length, and in particular, which employs seals for the glass column 
which do not come into contact with the pressure fluid. Other objects will 
be apparent to those skilled in the art. 
SUMMARY OF THE INVENTION 
According to this invention, there is provided a chromatographic column 
adapted for high pressure liquid chromatography comprising a glass tube 
open at both ends and positioned axially within a pressure tube having an 
internal diameter larger than the external diameter of the glass tube so 
as to provide a circumferential intermediate space therebetween and having 
an aperature in the wall thereof to provide communication between the 
intermediate space and a source of a pressurizing fluid when the column is 
connected therewith; a pair of removable screw caps threadably mounted on 
respective ends of the pressure tube, each having an aperature therein 
communicating with respective ends of the glass tube and providing an 
inlet and outlet, respectively, for chromatography eluent; and sealing 
means for sealing the open ends of the glass column from the intermediate 
space, which column is characterized by the sealing means comprising a 
flexible tubular shaped membrane positioned in the intermediate space and 
extending the length of the glass tube so as to provide a sleeve therefor 
which separates the glass tube from the pressurizing fluid.

As shown in the drawing, a glass column 1 is separated by a flexible 
membrane 2 from a pressure tube 3. An intermediate space 4 is provided 
between the pressure tube 3 and the flexible membrane. The ends of the 
pressure tube are threaded and fitted with a pair of screw caps 5 and 6 
(union or cap nuts). The lower screw cap 6 has a threaded annular bore 6a 
into which a screw stopper 7 is fitted. The upper screw cap 5 and the 
screw stopper 7 are provided with outflow 8 and inflow 9 capillaries, 
respectively. It should be noted, however, that the direction of flow can 
be chosen freely, so that capillary 8 can be used as inflow and capillary 
9 as outflow as well. Pressure tube 3 is provided with a connection 
fitting 10 for connecting the tube to a source of pressure fluid (not 
shown). The ends 1a and 1b of the glass tube 1 are sealed against the 
inner surface of upper screw cap 5 and the inner surface of screw stopper 
7 by a pair of resilient annular seals 11 and 12. Fitted in annular seals 
11 and 12 are a pair of glass frits 13 and 14 adapted to retain the 
chromatography medium (not shown) when the glass tube is filled therewith. 
The flexible membrane 2 separates completely the glass column 1 from the 
pressure medium when it is introduced through connection fittings 10 so 
that no adverse effect can be manifested by the pressure medium against 
the seals 11 and 12. 
The annular shoulder end portions 15 and 16 of flexible membrane 2 are 
clamped between the ends of the pressure tube 3 and screw caps 5 and 6. In 
order to facilitate easy replacement of the glass column 1, at least one 
of the union nuts is provided with a threaded bore 6a of a larger diameter 
than the external diameter of the glass tube 1, into which a screw stopper 
7 is threaded. 
In order to obtain a tighter seal, the ends 1a and 1b of the glass column 1 
are preferably ground flat. The arrangement of the screw stopper 7 in the 
screw cap 6 also permits relatively large variations in length in the 
glass column 1, which variations are compensated for by the amount that 
screw stopper 7 is screwed into union cap 6. 
In operation, membrane 2 is fitted into pressure tube 3 and the annular 
shoulders 15 and 16 of the end portions of membrane 2 are clamped to the 
respective ends of pressure tube 3 by screw caps 5 and 6. 
The ends 1a and 1b of glass tube 1 are fitted with annular seals 11 and 12 
and a glass frit 13 or 14 is positioned in one of the seals. The glass 
tube is filled with chromatography sorbent (not shown) and the other of 
glass frit 13 or 14 is then fitted into the other annular seal 11 or 12. 
The filled glass tube 1 is then inserted into pressure tube 1 through the 
annular bore 6a in screw cap 6. Screw stopper 7 is then threaded into 
screw cap 6 until sealing pressure is exerted against annular seals 11 and 
12. 
Any fluid which can be forced through the connecting nozzle 10 can be used 
to compensate for or exceed the pressure existing inside the glass column 
1 and thus prevent glass column 1 from exploding from the pressure of the 
chromatography eluent therein. The eluent used for the chromatographic 
separation can be used for this purpose by connecting a conventional 
T-joint connecting the source of the eluent to the feed capillary 9 and 
the connection fitting 10. However, a fluid different from that used for 
the chromatographic separation, such as air, water, oil or a similar 
medium, compressed to the required pressure, is preferably used. If air or 
water is used as the pressure fluid, the flexible membrane 2 can be made 
of virtually any type of elastic rubber. On the other hand, if the 
particular eluent used for the chromatography is employed at the pressure 
medium, the flexible membrane 2 is preferably made of a more inert 
material, such as polytetrafluoroethylene. Although this material has only 
a relatively low flexibility, it is nevertheless sufficient to provide the 
requisite seal between the ends of pressure tube 3 and screw caps 5 and 6. 
To conduct a chromatographic separation in the column, the chromatography 
fluid is supplied to inlet aperture 9 and the pressure fluid is supplied 
to connection fitting 10 at a pressure which is at least the same as the 
internal pressure in the glass tube 1. The operating pressures employed 
depend largely on the strength of pressure tube 3 and can be up to several 
hundred bars. 
Since only a single pressure tube 3, which can be formed of stainless steel 
or chrome plated brass, is required for each diameter of glass tube 1, the 
user can stock economically a large number of glass tubes 1 filled with 
the same or different chromatography media, for the most diverse 
chromatographic separation problems with relatively little financial 
expenditure, and can insert them into the pressure tube 3 when required in 
an extremely short time. 
To change the glass tube 1 for another like tube, it is necessary only to 
remove screw stopper 7 and not screw caps 5 and 6, which hold the flexible 
membrane 2 is position. After removing glass tube 1 and inserting another 
filled glass tube, screw stopper 7 is merely screwed in again until the 
seals 11 and 12 between the glass tube 1 and cap 5 and screw stopper 7 are 
pressed into a sealing fit. 
From the foregoing description, one skilled in the art can easily ascertain 
the essential characteristics of this invention, and without departing 
from the spirit and scope thereof, can make various changes and 
modifications of the invention to adapt it to various usages and 
conditions.