U.S. patent application number 12/699765 was filed with the patent office on 2010-05-27 for multiple segment chromatography assembly for packing a chromatography column.
This patent application is currently assigned to Phenomenex, Inc.. Invention is credited to Tivadar Farkas, Romaine R. Maiefski, Peter C. Rahn, Emmet E. Welch.
Application Number | 20100126921 12/699765 |
Document ID | / |
Family ID | 37829805 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100126921 |
Kind Code |
A1 |
Rahn; Peter C. ; et
al. |
May 27, 2010 |
MULTIPLE SEGMENT CHROMATOGRAPHY ASSEMBLY FOR PACKING A
CHROMATOGRAPHY COLUMN
Abstract
A slurry chamber is fastened to and held in coaxial alignment
with a chromatography column by a V-band. One end of the column has
an end cap and fit. A slurry of fluid and chromatographic media is
placed in the column and chamber. A piston is forced through the
chamber and into the column by a hydraulic ram to expel the fluid
and form a media bed in the column. The slurry chamber is removed,
and a split end cap is fastened to the column. A threaded recess in
the split end cap receives a split, threaded collet. The collet is
tightened until it pushes against the piston with the same force as
the ram, at which point the ram is released and the column removed
for use.
Inventors: |
Rahn; Peter C.; (Richmond,
VA) ; Maiefski; Romaine R.; (Oceanside, CA) ;
Farkas; Tivadar; (Harbor City, CA) ; Welch; Emmet
E.; (Aliso Viejo, CA) |
Correspondence
Address: |
STETINA BRUNDA GARRED & BRUCKER
75 ENTERPRISE, SUITE 250
ALISO VIEJO
CA
92656
US
|
Assignee: |
Phenomenex, Inc.
Torrance
CA
|
Family ID: |
37829805 |
Appl. No.: |
12/699765 |
Filed: |
February 3, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11257655 |
Oct 25, 2005 |
7674383 |
|
|
12699765 |
|
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|
|
Current U.S.
Class: |
210/198.2 |
Current CPC
Class: |
G01N 30/6021 20130101;
B01D 15/22 20130101; G01N 2030/522 20130101; B01D 15/22 20130101;
B01D 15/206 20130101; G01N 30/603 20130101; G01N 2030/565 20130101;
B01D 15/22 20130101; G01N 30/6021 20130101; B01D 15/206 20130101;
G01N 30/56 20130101; G01N 30/603 20130101 |
Class at
Publication: |
210/198.2 |
International
Class: |
B01D 15/08 20060101
B01D015/08 |
Claims
1-31. (canceled)
32. A multiple segment chromatography assembly for preparing a
chromatography column, the assembly comprising: a slurry chamber
having first and second open ends, the chamber having walls
defining an inner cylinder of diameter D; a chromatography column
having first and second opposing ends and an end cap over the
second end, the second end of the slurry chamber being removably
attachable to the first end of the column, the column having walls
defining an inner cylinder of diameter D; an annular seal placed
between the column and the chamber for providing a fluidic seal
therebetween; a V-band clamp encircling the seal and cooperating
with at least one of recesses or protrusions in the exterior of the
chamber and column to hold the chamber and column in coaxial
alignment; a piston traversable through the slurry chamber and into
the column to provide axial compression during packing of the
column.
33. The assembly of claim 32, further comprising a chamfer on an
interior edge of the first end of the column.
34. The assembly of claim 32, further comprising a chamfer on an
interior edge of the first end of the slurry chamber.
35. The assembly of claim 32, further comprising a slurry of fluid
and chromatographic media in the chamber and column.
36. The assembly of claim 35, wherein the piston is in one of the
chamber or column, the piston having at least one seal interposed
between the piston and the cylindrical wall of the chamber or
column in which the piston is located.
37. The assembly of claim 35, wherein the piston is in the column,
the piston having a frit with a first diameter about diameter D and
having a second, smaller diameter.
38. The assembly of claim 32, wherein the piston has traversed the
slurry chamber and has passed into the column to apply a packing
pressure to chromatographic media in the column, with the V-band
clamp being released while the piston maintains the packing
pressure on the media.
39. The assembly of claim 32, further comprising a ram applying a
force on the piston sufficient to push the piston and a
chromatographic slurry through the slurry chamber and into the
column and to maintain a positive packing pressure on the media in
the column when the slurry chamber is removed.
40. The assembly of claim 32, further comprising chromatographic
media in the slurry chamber and column; and and a force applying
mechanism configured to apply a force on the piston sufficient to
push the piston and chromatographic media through the slurry
chamber and into the column and to maintain a packing pressure on
the media in the column.
41. The assembly of claim 40, further comprising a clamshell
mechanism configured to fasten the piston to the column when the
piston is inside the column and exerting a packing pressure on the
media in the column.
42. A multiple segment chromatography assembly for preparing a
chromatography column, the assembly comprising: a slurry chamber
having first and second open ends, the chamber having walls
defining an inner cylinder of diameter D; a chromatography column
having first and second opposing ends and an end cap over the
second end, the second end of the slurry chamber being removably
attachable to the first end of the column, the column having walls
defining an inner cylinder of diameter D, the slurry chamber being
a separate part from and separable from the chromatography column;
annular seal means between the column and the chamber for providing
a fluidic seal therebetween; piston means passing through the
slurry chamber and at least partially into the column for
compressing a slurry bed in the column during use of the assembly;
releasable clamp means for holding the chamber and column in
coaxial alignment during packing of the column as at least a
portion of the piston moves into the column during packing and for
releasing the slurry chamber for removal from the column.
43. The assembly of claim 42, further comprising means for locking
the piston to the column to maintain the piston position during and
after removal of the slurry chamber.
44. The assembly of claim 43, further comprising means for
adjusting the position of the piston to adjust the force on the
chromatography media in the column during use of the assembly.
45. The assembly of claim 42, further comprising chromatographic
media in the column which has passed through the slurry chamber and
into the column; and means for maintaining the position of the
piston in the column without substantially releasing the pressure
exerted by the piston on the media in the column during and after
removal of the slurry chamber.
Description
BACKGROUND OF THE INVENTION
[0001] This application relates to a method apparatus for packing
tubular columns with particles, such as packing HPLC columns with
media.
[0002] Liquid Chromatography is a method for the separation of
compounds from a mixture by encouraging a different distribution
between the solid particles in the stationary phase of a column and
the liquid phase that is passed through the column. The column
packing material needs to be well packed and uniformly packed to
provide a consistent surface for the separations to occur.
Depending on the individual compounds affinity for the column
packing material compared to the affinity for the liquid passing
through the column determines the difference in time that the
compounds reside inside the column. After the compounds exit the
column, they are either detected (analytical liquid chromatography)
or the compounds are individually collected (preparative liquid
chromatography). For the chromatographic separations to be carried
out efficiently the column packing material bed must be uniformly
and densely dispersed in the column with no channels or voids or
stratification of the media that would create re-mixing of the
separated compounds.
[0003] To achieve this high performance, liquid chromatography
columns are generally formed by dispersing or suspending the
spherical or irregular chromatographic particles in a suitable
solvent creating a slurry. The slurry is placed inside the column
tube and the particles are settled to form the column bed by
exerting a force onto or through the slurry. This force causes the
particles to sediment or "pack" into the column tube. During the
packing process, the slurry solvent evacuates through a porous disk
called a "frit" which is sufficiently porous to allow liquid to
evacuate, but retain the chromatographic particles. As the slurry
solvent is evacuated, the chromatographic particles are compressed
into a uniform and dense "bed", and the column is then ready for
use.
[0004] Compressing or packing the column bed is achieved by one of
two methods. One common technique of forming chromatographic beds
is to produce a slurry inside the column and then using high
solvent flow through the column to push the particles towards the
outlet of the column. To produce these columns using the slurry
technique, the chromatographic column is open at the top during the
packing process and this end is attached to one end of a slurry
chamber. The chromatographic media slurry fills the slurry chamber
and the column tube. The outlet end of the column holds the frit
that retains the chromatographic media but permits the liquid to
exit the column. The inlet end of the slurry chamber is attached to
a high pressure, high volume pump that forces a liquid through the
chamber. The high flow liquid forces the particles to migrate
towards the exit of the column and the chromatographic media is
slowly compressed into a uniform and dense bed.
[0005] The slurry technique requires high-pressure pumps to provide
the liquid flow until the bed is packed, which may take as long as
one hour. This relatively long packing time at high flow
significantly increases cost of the final column due to large
volume of solvent required, and reduces manufacturing throughput.
Once the chromatographic bed is formed, the packed column tube is
removed from the slurry chamber and a permanent end fitting is
placed onto the column. Another major disadvantage with this high
pressure high flow rate slurry packing technique is that the
chromatographic media is subjected to very high pressures during
the packing process to form the compressed chromatographic bed but
this pressure must be released when the column is removed from the
slurry chamber. When the pressure is removed from the column, the
compacted chromatographic media decompresses or relaxes and the
chromatographic bed expands and can move within the column tube. To
close the column, the excess media is removed from the top of the
column and another frit and end cap is placed onto the column tube
to prevent anymore shifting or expansion of the packed bed. The bed
shift and subsequent removal of the excess media causes a variable
and somewhat reduced bed density, particularly at the head of the
column. This variation and reduction in bed density creates
performance problems such as settling or voiding of the bed,
particularly when the column is operated under high flow rates.
This phenomenon is most pronounced on columns that have a
relatively low aspect ratio (length/internal diameter) of <25.
Currently users in high throughput, high volume preparative
applications experience reduced lifetimes with columns prepared
using this slurry technique, especially when the column lengths are
short due to the lower density beds.
[0006] An alternative technique to packing a column is the use of
axial compression, as generally described in U.S. Pat. No.
5,893,971. However, most chromatographic columns packed by axial
compression are integrated into a single system which includes both
the column and the packing apparatus. The column itself is not
removable from the system itself, meaning the column is operated as
part of the system. Also, the column tube is only partially filled
with chromatographic media as most of the tube volume is used as a
slurry chamber. Furthermore, as the packing system and column are
integrated into a single unit, cost and complexity are also
higher.
[0007] A newer variation of axial compression packing is described
in U.S. Pat. Nos. 5,951,873 and 6,036,755. The column can be
removed from the packing system by incorporating a removable
spring-rod and piston that maintain active pressure on the column
bed. But even this system requires a relatively long column tube,
even if the desired bed length may be only 1/3 to 1/4 that of the
overall column length. The reason for this is that a significant
portion of the overall column tube length is required simply to
accommodate the uncompressed slurry prior to compression and/or the
spring assembly. Thus the design suffers from long and sometime
very heavy column assemblies that are inconvenient, impractical and
difficult for operators to use in a typical laboratory or
purification lab.
[0008] These designs are especially impractical in high-throughput
purification laboratories where 4-8 columns may be run in parallel,
and/or where space is limited. Furthermore, the high cost of the
column hardware of this longer and more complex design limits their
acceptance in high use or high-throughput environments as they
become too costly to operate in large numbers.
[0009] Yet another disadvantage of some axial packed columns is
that the frit diameter is much smaller than the column diameter.
This reduced diameter is due to the space required for a seal or
seal assembly that presses against the column wall to prevent
leaking of solvent or media when high pressures are applied to the
column during axial compression. This reduced diameter leaves an
unused area of the column near the outer walls where the frit does
not cover the chromatographic bed and the sample is not applied to
this area. With short bed columns the distribution of the sample
across the entire surface is critical since the bed length is very
short and the sample needs to be quickly and uniformly dispensed
across the surface. In slurry packed columns the frit diameter is
generally equal to or greater than the column diameter.
[0010] Therefore, there is a need for more compact, disposable
column designs that can be produced by axial compression packing
methods and components to improve lifetime and not be cumbersome
for the chemist to use.
SUMMARY
[0011] A slurry chamber (tube) is fastened to and held in coaxial
alignment with a chromatography column by a V-band. One end of the
column has an end cap, and fit. A slurry of fluid and
chromatographic media is placed in the column and slurry chamber. A
piston abuts a stepped diameter frit, with the piston and frit
forced through the chamber and into the column by a hydraulic ram
to expel the fluid and form a media bed in the column. The slurry
chamber is removed, and a split end cap or split retainer are
positioned around the column and held in place by a sleeve (1 piece
or 2 piece). A threaded recess in the split end cap or split
retainer receives a threaded collet. The collet is tightened until
it pushes against the piston with the same force as the ram, at
which point the ram is released and the column removed for use. The
frit preferably has a seal interposed between a smaller diameter of
the frit and the adjacent column wall. Likewise, the piston has a
stepped diameter, with a seal interposed between a smaller diameter
of the piston and the adjacent column wall, with the smaller
diameter preferably abutting the frit.
[0012] One aspect of the present invention relates to an improved
method for the formation of economical and robust liquid
chromatography columns by axial compression. Another aspect of this
invention relates to a method for removing the slurry chamber while
maintaining axial compression on the bed resulting in a column that
is compressed but shorter and less complex than traditional axial
packed columns while maintaining the flexibility to accommodate bed
length variation. A further aspect of this invention significantly
reduces the amount of solvent and production time required to pack
the column bed compared to the slurry packing technique.
[0013] There is advantageously provided a removable
slurry/pre-compression chamber. A segmented column or chamber
assembly is used that includes a first segment, which is a slurry
pre-compression chamber, and a second segment, which is the column
chamber. The first segment serves as a slurry and pre-compression
chamber to accommodate the chromatographic slurry prior to packing,
and during the initial stages of compression. A piston driven by a
piston rod or piston sleeve assembly moves the piston towards the
fixed end of the column chamber (second segment). The piston itself
passes through the first segment and enters the second segment. The
piston travels a short distance into the second segment until the
media has been adequately compressed to form a stationary bed. The
design allows the slurry pre-compression chamber (first segment) to
be removed while the piston rod or piston sleeve applies force to
the piston to maintain the bed compression. A securing mechanism
can then be attached to secure the piston in place, allowing the
piston rod to be detached from the piston and removed. The ability
to pack by axial compression, and then remove the slurry chamber
while keeping the piston in place provides very desirable
advantages.
[0014] The design also advantageously allows for small variations
in final column bed length. A bed compression screw and a V-band
clamp design provide fine adjustment of the piston position based
on the final bed height achieved when the media is packed into the
column. This ability to accommodate variable bed heights ensures
that a set compression force can be maintained while accommodating
variations (preferably small variations) in the amount of media
packed in a column. A variation of up to about one inch (25 mm) in
bed height is believed achievable with a given column length.
[0015] A two-stepped, hat shaped frit design is also advantageously
provided. The frit design increases the amount of the column bed
surface area covered by frit allowing quicker dispersion of the
sample across the column bed. Older axial compression designs use a
piston seal to engage the column wall and the fit was smaller in
diameter than the column bed. The older design leaves an area
between piston assembly and the wall that was not available for
separations. The two-stepped, hat-shaped fit design is very useful
for short bed length columns where the sample must be dispersed
across the media as quickly as possible. This frit design is also
believed to provide advantages for longer length columns.
[0016] There is also provided a mechanism and method for
maintaining axial compression on the column bed while the slurry
chamber is removed and replaced by a bed compression mechanism,
such as a screw. Advantageously, the column bed is not allowed to
relax or expand after packing. The compacted bed is compressed once
during the packing process and this pressure is maintained when the
inlet end fitting is attached. This avoids the need for springs to
maintain the bed compression.
[0017] In one aspect of this, invention there is provided a
portable tubular chromatography column having a tubular body with
an inner diameter with first and second ends covered by first and
second end caps, respectively. The column has a bed of
chromatographic media placed between a first and second frit all
located inside the body. A piston abuts the first frit and exerts a
predetermined pressure on the bed. An adjustable locking mechanism
has a support fastened to the body and has a threaded adjuster
interposed between the support and the piston such that rotation of
the threaded adjuster increases or decreases the force the piston
exerts on the bed.
[0018] In a further variation of this above described embodiment
the support clamps to an exterior of the body, and preferably forms
a V-band clamp. Further, the threaded adjuster optionally comprises
a collet having one end abutting the piston. Advantageously, the
collet has multiple lead threads, with two leads being preferred.
In a further variation the support comprises a split end cap that
is clamped to the body. The split end cap can optionally enclose
one end of the tube or chamber and is optionally held together by
an encircling structure. Preferably the split end cap has a
threaded recess therein to receive the adjustable fastener. The
recess also preferably has multiple lead threads. Further, the
collet preferably has a wrenching surface.
[0019] In further variations, the frit extends to adjacent the
inner diameter of the column body with no seal interposed between
the frit and the column wall. The frit preferably has a first
diameter about the same as but slightly smaller than the inner wall
with no seal interposed between the frit and the inner wall.
Advantageously, the frit has first and second concentric diameters
with the diameter of the frit abutting the media being the first
diameter and being larger than the second diameter. The piston
preferably has at least one seal interposed between the piston and
the inner wall with at least one seal selected to provide a seal at
fluid pressures of several thousand psi. Moreover, a portion of the
piston preferably extends outside an end of the tubular body.
[0020] In a further aspect of this invention, a new fit is
provided. The fit is preferably, but optionally for use with a
chromatography column having a tubular body with a cylindrical
interior having a first diameter. The frit has a first cylindrical
portion having a diameter about the same as but slightly smaller
than the first diameter of the column. The frit has a second
cylindrical portion having a smaller diameter, with the first and
second portions being concentric. In further variations the frit is
integrally and unitarily formed from a single piece of material, or
alternatively the frit is formed from two abutting frits of
different diameter.
[0021] In a further aspect of this invention there is provided a
method for packing a tubular chromatographic column having a first
and second opposing ends defining a first length and having an end
cap on the first end of the column. The column has an interior
diameter. The method includes abutting a slurry chamber to the
second end of the column and coaxially with the column and forming
a fluid tight seal between the slurry chamber and the second end of
the column. A slurry is placed in the column tube and slurry
chamber, with the slurry containing fluid and chromatographic
media. A piston is placed in the slurry chamber, with the piston
having seals interposed between the piston and the slurry chamber
and a frit interposed between the piston and the slurry. The piston
is advanced through the slurry chamber and at least part way into
the column. Advancement of the piston is stopped when the media in
the slurry forms a bed that is compacted to a desired pressure or
length.
[0022] In a preferred form, the method includes locking the piston
to the column. More preferably the method includes removing the
slurry chamber and locking the piston to the column without
releasing the pressure on the bed. Advantageously, the frit
comprises a stepped disk having first and second concentric and
different diameters with a larger diameter abutting the slurry.
More preferably, a seal is interposed between the smaller diameter
and the inner diameter of the column and no seal is interposed
between the larger diameter and the inner diameter of the column.
Further, a chamfer is preferably formed on an interior edge of the
second end of the column, although the chamfer is optional and can
especially be omitted if the mating parts are sufficiently
concentric.
[0023] In a further preferred variation, the method includes
removing the slurry chamber while maintaining the position of the
piston and placing two parts of a split end cap over the second end
of the column, where the end caps each have a portion of a threaded
recess formed therein. A split, threaded collet or split piston
retaining ring with a threaded recess is fastened to the second end
of the column. An outside collar is placed over the piston
retaining ring and fastened in place. Finally, the threaded collet
is advanced in the recess until the collet holds the piston in
place.
[0024] In a preferably variation on this later preferred method,
advancing the piston comprises placing a hydraulic ram in contact
with a shoulder on the piston and advancing the hydraulic ram. The
slurry chamber can be removed from the column with the ram in
place, after which the piston is locked in place, with the ram
position being maintained until the slurry chamber is removed from
contact with the column and until the piston is locked in place.
After completion of packing and locking the piston in place, the
column is removed from the ram, and the outlet in the first and
second ends of the column are plugged. In further variations of the
above methods, forming the fluid tight seal includes placing a
V-band clamp over the juncture of the slurry chamber and the
column. The locking step also can include placing a V-band clamp
around the second end of the column.
[0025] In a further aspect of this invention, a multiple segment
chromatography assembly is provided. The assembly includes a slurry
chamber having a first and second open end, the chamber having
walls defining an inner cylinder of diameter D, and a
chromatography column having an first and second opposing ends and
an end cap over the second end. The second end of the slurry
chamber abuts the first end of the column. The column has walls
defining an inner cylinder of diameter D. An annular seal is placed
in a recess formed in part in an exterior surface of the first end
of the column and formed in part by an exterior surface of the
second end of the chamber. A V-band clamp encircles the seal and
cooperates with at least one of recesses or protrusions in the
exterior of the chamber and column to hold the chamber and column
in coaxial alignment.
[0026] In further variations of this apparatus a chamfer is formed
on an interior edge of the first end of the column. Preferably a
chamfer is also formed on an interior edge of the first end of the
slurry chamber. A slurry of fluid and chromatographic media is
placed in the chamber and column. A piston is placed in one of the
chamber or column. The piston has at least one seal interposed
between the piston and the cylindrical wall of the chamber or
column in which the piston is located. Preferably, the piston
extends at least part way into the column and the piston has a frit
with a first diameter about diameter D and having a second, smaller
diameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] These and other advantages and features of the invention
will be better appreciated in view of the following drawings and
descriptions in which like numbers refer to like parts throughout,
and in which:
[0028] FIG. 1 is a sectional view taken along 1-1 of FIG. 2;
[0029] FIG. 2 is a plan side view of a chromatography column;
[0030] FIG. 3a is a cross sectional view of one embodiment of a
piston and fit;
[0031] FIG. 3b is a cross-sectional view of a second embodiment of
a piston and frit show in the piston and frit of FIG. 1;
[0032] FIG. 3c is an exploded perspective view showing a piston and
frit of FIGS. 1 and 3b;
[0033] FIG. 4 is a partial sectional view illustrating the piston
of FIG. 3b in a packed column;
[0034] FIG. 5 is a sectional view showing the configuration of a
column of FIG. 1 held in a chuck and a recessed support plate
before the packing of the column;
[0035] FIG. 6 is a graph showing how pressure on a bed of media
increases as it is dynamically and hydraulically packed using the
column of FIGS. 1 and 9;
[0036] FIG. 7 is a sectional view taken along 7-7 of FIG. 8;
[0037] FIG. 8 is a perspective view of a column of a further
embodiment;
[0038] FIGS. 9a and 9b are a sectional view and an enlarged portion
of that sectional view showing column and slurry chamber of FIGS.
7-8 held by a V-band;
[0039] FIG. 10 is a sectional view of a column of FIG. 8 packed
with media and held by a piston locked in position;
[0040] FIG. 11 is sectional view showing the configuration of a
column of FIGS. 7 and 9 held in a recessed support plate before the
packing of the column;
[0041] FIG. 12 is sectional view taken along 12-12 of FIG. 13;
[0042] FIG. 13 is an exploded perspective view of a further
embodiment of a locking mechanism for the column of FIG. 10;
[0043] FIG. 14a is a plan view of a further embodiment of a packed
column;
[0044] FIG. 14b is a sectional view taken along 14b-14b of FIG.
14a;
[0045] FIG. 15 is an exploded perspective view of a further
embodiment for locking the piston to the column;
[0046] FIG. 16 is a sectional view taken along 16-17 of FIG.
17;
[0047] FIG. 17 is a side plan view of the column of FIG. 15;
and
[0048] FIG. 18 is a side plan view of a press holding the assembly
of FIG. 9a before the media is packed.
DETAILED DESCRIPTION
[0049] Two primary embodiments are shown, with the first embodiment
using a single-piece, longer body and the second embodiment using a
two-piece, segmented body.
[0050] Referring to FIGS. 1-4, a chromatography column 20 is
provided having a tubular body 22 that is preferably cylindrical
and has opposing ends 21a, 21b. A downstream end cap 24 is fastened
over a first, downstream end 21a, preferably the downstream or
outlet end. The end cap 24 preferably, but optionally, is
cup-shaped and has a generally flat end with a tubular skirt having
interior threads that mate with exterior threads on the outside of
the body 22 to fasten the end cap 24 to the body. An outlet 26 is
formed in the generally flat end of the cap 24 and a threaded plug
28 engages mating threads on the outlet passage to releasably block
the outlet 26.
[0051] A first frit 30 is placed in or over the first end 21a and
held in place by the first end cap 24. A cup-shaped frit holder 32
is preferably, but optionally interposed between the first frit 30
and the first end cap 24. The fit holder 32 has a generally flat
end with a two-stepped skirt forming a first, smaller diameter
recess 34 into which the frit nests during use, and forming a
second, larger diameter recess 36 which receives a stepped end 21a
of the body 22. A lip on the distal portion of end 21a abuts a
shoulder formed between the different diameters of the recesses 34,
36 to form a seal, with the larger diameter recess 36 overlapping
the stepped end 21a to form a further seal. The end cap 24 holds
the frit holder 32 and frit 30 in place and in sealing engagement
with the first end 21a of body 22. The fit holder 32 has an outlet
aligned with outlet 26.
[0052] The interior of the tubular body 22 preferably has a
cylindrical cavity 38 within which slides a piston 38 has a
downstream end that preferably, but optionally, abuts a second frit
42. Between the frits 30, 42 is a media 44 typically forming a
stationary phase for chromatographic analysis. The media typically
comprises silica or polymer particles coated with various chemicals
suitable for chromatographic analysis.
[0053] The piston 40 is urged against the frit 42 and media 44 by
piston sleeve 46 that in turn is held in place by second end cap 48
and thrust washer 50 as described in more detail below. The column
20 has a longitudinal axis 52 that preferably extends through the
center of the piston 40. As used herein, the downstream end or
direction refers to a direction along axis 52 as used during
packing, and in the illustrated embodiments that direction is from
the end cap 48 toward the end cap 24, and the upstream direction is
opposite thereto. In actual use the mobile phase preferably passes
in the same direction, but it can pass through the column in either
direction so upstream and downstream could be reversed during
actual use.
[0054] Referring to FIGS. 1 and 3b-3c, the piston 40 and second
frit 42 are described. The downstream end of piston 40 has a wall
54 extending downstream toward the downstream end cap 24 and along
the longitudinal axis 48. The wall 54 forms a cylindrical recess
sized to receive a portion of frit 42. The frit 42 is generally
hat-shaped having a first disk shaped portion forming flange 56
with a circular periphery slightly smaller than the inner diameter
of the walls 38, preferably about 0.001 inches smaller in diameter.
The disk-shaped flange 56 extends radially outward from the axis 48
beyond a smaller diameter cylindrical boss 58 located on the
upstream side of the flange 56. The fit 42 thus comprises the
flange 56 and boss 58, which are preferably formed with internal
passageways to distribute fluid evenly across the downstream face
of flange 56.
[0055] The recess formed by wall 54 on the piston 40 receives the
cylindrical boss 58, with the downstream end of the wall 54
preferably abutting the flange 56 of the frit 42.
[0056] A first seal 60 is preferably, but optionally interposed
between the exterior of the wall 54 and the adjacent inner wall 38
of the body 22. The first seal 60 advantageously has a rectangular
cross-section with its longer dimension along the longitudinal axis
52 and with a downstream end of the seal 60 preferably abutting the
flange 56. The first seal 56 is preferably an elastomer or polymer
such as polyethylene or polypropylene or polytetrafluoroethylene or
rubber. A St. Gobain #450151883 seal is believed suitable. The
first seal helps restrict media 44 and liquid from passing between
the piston 42 and inner wall 38.
[0057] An optional second seal 62 abuts the upstream end of the
first seal 60. The second seal 62 is preferably an elastomer seal,
located in a corresponding groove 64 in the piston 40. The second
seal 62 is preferably an elastomer or polymer such as polyethylene
or polypropylene or polytetrafluoroethylene or rubber. The second
seal 62 could be an O-ring seal. The second seal 62 helps keep the
first seal 60 from moving upstream along axis 52. It may also
optionally help seal against media 44 and liquid passing between
the piston 40 and inner wall 38.
[0058] A wear ring 66 is located between two axially spaced flanges
68a, 68b on piston 40. The ring 66 also optionally provides a
further sealing surface. The flanges 68a, 68b extend radially
outward from axis 52 to form a circular periphery slightly smaller
than the inner diameter of interior wall 38. The wear ring 66
preferably has a rectangular cross section, and has an axial length
abutting the inner wall 38 sufficient to reduce rocking of the
piston within the cylindrical wall 38 as the piston 40 moves along
the axis 52. Wear ring 66 could be polyethylene or polypropylene or
polytetrafluorethylene. It could have an O-ring configuration, or
other configurations.
[0059] A shoulder 69 is formed on the upstream end of the piston 40
with an upstream boss 70 of smaller dimension extending upstream.
The shoulder 69 is preferably a continuous annular surface facing
upstream but intermittent surfaces could be used. The boss 70
preferably has a cylindrical exterior with threads thereon. A fluid
passage 72 extends through the piston 40, preferably coincident
with axis 52. The fluid passage 72 has a downstream end in fluid
communication with frit 42, and preferably opens onto boss 58 of
fit 42.
[0060] The wall 54 forms a recess having a top or upstream surface
71 that is generally orthogonal to the longitudinal axis 52.
Preferably, however, as seen in the figure, the surface 71 is
slightly inclined upstream and toward the longitudinal axis to form
a shallow conical recess between the surface 71 and the adjacent
frit 42. This conical space avoids clogging in the event the sample
contains some particulates, and it also helps spread the sample
over the frit. An inclination angle of about 3.degree. is believed
suitable to form t his conical space.
[0061] The piston sleeve 46 preferably comprises a tubular shaft
having a downstream end configured to abut shoulder 69, with an
interior sized to fit over the boss 70. Preferably, but optionally,
the interior on the downstream end of the piston sleeve 46 is
threaded and configured to threadingly engage threads on boss 70. A
shoulder 75 on an upstream portion of piston sleeve 46 abuts one of
the end cap 48 or the thrust washer 50. The thrust washer 50 is
preferably a relatively thick stainless steel in order to maintain
the position of the piston accurately. The piston sleeve 46
preferably extends through an opening 76 in the end portion of
upstream end cap 48. A tube 78 extends through the piston sleeve
46, preferably coincident with axis 52. An upstream end 78a of the
tube 78 is adapted to be placed in fluid communication with
chromatography equipment to introduce a mobile phase into the
column 20. A downstream end 78b of the tube 78 is configured to
fasten to be placed in fluid communication with the upstream end of
piston 40 and its fluid passage 72. A cap 80 blocks the inlet end
78a.
[0062] A detent 82 is placed adjacent the upstream end of the
piston sleeve 46. A circular recess extending around the outer
periphery of the piston sleeve 46 is believed suitable to form
detent 82. The upstream end of the piston sleeve 46 forms a driving
surface 84, or if desired an additional driving shoulder is formed
on the piston sleeve 46 facing upstream to serve the purpose of the
driving surface 84 as described later. The locking surface 75 is
formed in the sleeve 46. Preferably the locking surface 75 takes
the form of a shoulder on the sleeve, and more preferably comprises
an annular shoulder rather than intermittent surfaces.
[0063] The upstream end 21a of the body 22 is preferably formed
with a chamfer 86 on the inside of the body 22 and angled outward
from longitudinal axis 52. The chamfer 86 extends to the flattened
or rounded lip of the body 22 which faces upstream.
[0064] Referring to FIGS. 1 and 5, the packing of the column 20 is
described. The downstream end cap 24 is placed on body 20 to hold
the downstream fit 30 in place. The column 20 is placed in a holder
with the upstream end 21a being open rather than covered.
Preferably, but optionally, the column 20 is placed in a chuck 87
which is tightened to abut the body 22 and hold the column so the
centerline 52 aligns with the centerline of the chuck. A three part
chuck 87 is preferred. The downstream end of cap 24 can abut a
support surface 88 as shown, or the chuck 87 can grip the body 22
sufficiently for the following packing.
[0065] A predetermined amount of media 44 is placed in a beaker and
mixed with a fluid to form a slurry. The slurry is preferably
sonicated to remove air and further mix the media 44 and fluid. The
slurry is then poured into the inside of the body 22. The flask is
rinsed with the fluid, preferably twice, and the fluid poured into
the body 22 in order to ensure all the media is placed into the
body 22. Additional fluid is added, if needed to fill the fluid
level to the chamfer 86. It is undesirable to force air through the
column, so the fluid level is high enough to avoid air entrapment
or a release valve is provided. Alternatively, the slurry could be
pumped from a tube or other filling methods could be used. The
outlet passage 26 is preferably not blocked at this stage so fluid
can exit through the outlet 26 under the force of gravity.
[0066] The piston 40 is placed onto the piston sleeve 46 so the end
of the sleeve abuts the piston shoulder 69. Preferably mating
threads on boss 70 engage mating threads on the inside of sleeve 46
to form a threaded engagement that prevents relative axial movement
of the sleeve and piston. Advantageously a metal cap is placed over
the end of sleeve 46 to block fluid flow out of the upstream end
78a of tube 78. The hat-shaped frit 42 is placed in the piston, and
the upstream end cap 48 and thrust washer 50 are placed on the
piston sleeve 46. As desired, a locking mechanism can also be
placed over the piston sleeve 46.
[0067] The piston sleeve 46 is placed into a press 90. The press 90
preferably, but optionally comprises a hydraulic ram and will be
described as such. The detent 82 can engage a mating releasable
detent pin in the press 90 to hold the piston sleeve 46 in place,
along with any locking mechanism and piston 40 attached to the
sleeve. The piston sleeve 46 is positioned in the ram 90 such that
the longitudinal axis of the sleeve coincides with the longitudinal
axis 52 of the body 22.
[0068] The ram 90 then advances the piston into open end of the
body 22, with the chamfer 86 helping to guide the mating parts and
accommodate slight misalignments. Preferably a slight amount of
excess fluid is forced over the chamfered lip 86 in order to ensure
no air is entrapped between the fit 42 and the fluid. The
advancement of the ram 90 and piston 40 is slow during this initial
engagement portion. The ram 90 advances the piston 40 into the body
22 until the wear ring 66 abuts the interior wall 38 at which point
the speed of the ram can increase if desired. The advancing piston
40 forces fluid out the outlet passage 26 while the frit 30 retains
the media inside the body 22. When the fluid is largely expelled
from the body 22 the piston 40 compresses the media 44 at which
point the pressure rapidly increases.
[0069] The ram 90 advances the piston 40 until a desired pressure
is reached at which point movement of the piston 40 is halted. At
that point the fluid is largely pressed out through passage 26 and
the media 44 is compacted to form a stationary phase for a desired
use, preferably for chromatographic analysis. The relative movement
of the piston 40 and shaft 46 relative to the body 22 is then
fixed. This is preferably, but optionally achieved by moving thrust
washer 50 until it abuts locking shoulder 75, or if no thrust
washer is used, the cap 48 is advanced until a portion of the cap
abuts the locking surface 75. Preferably, but optionally, the
locking shoulder 75 extends adjacent the opening 76 in the cap 48,
so that the thrust washer 50 does not have a significant
unsupported or free length extending between the cap 58 and the
shoulder 75. The cap 48 has interior threads engaging mating
threads on the outside upstream end of the body 22. The length of
the sleeve 46 and location of the locking shoulder 75 are selected
relative to the length of body 22 and location of these mating
threads so that the threads can urge and thrust washer 50 along
axis 52 to abut the locking surface 75.
[0070] The cap 48 is tightened until it causes thrust washer 50 to
push against shoulder 75 and sleeve 46 to further compact media 44.
A linear movement gauge 92 in communication with the ram 90 shows a
slight increase in piston movement. The linear movements 92 can
preferably, but optionally, read movement to the second or third
decimal point. When the media 44 is further compacted a slight
amount of 0.01 or 0.001 or preferably 0.0001 on the linear movement
gauge, then the ram 90 is released and the cap 48, thrust washer
and locking surface 75 hold the sleeve 46 and piston 40 in place.
The column 20 is removed from the chuck 87. The plug 28 blocks the
outlet passage 26. The metal cap on the upstream end 78a is removed
if desired, and replaced with a plastic cap and/or union. The
packed cartridge is then suitable for shipping and/or use. A force
gauge could also be used instead of or in addition to a linear
movement gauge.
[0071] Referring to FIG. 6, an illustrative graph of the pressure
exerted by ram 90 on the left vertical graph, versus the position
of piston 40 shown on the horizontal graph. The piston movement is
represented in time. As the piston 40 expels the excess fluid from
the body 22 and outlet 26, the pressure on ram 90 increases fairly
linearly as the media 44 is compacted and the fluid being forced
through the bed experiences increased flow resistance. When the
fluid is largely expelled through outlet 26 the pressure increases
significantly as further motion of the piston 40 compacts the media
44 in the remaining fluid. If the pressure increase too much the
media 40 will deform or it will crush and form fines, each of which
decreases flow through the media bed 44. The desired compaction
pressure will vary with the particular media being used. The
movement of piston 40 is stopped when the pressure reaches a
desired pressure.
[0072] This first embodiment achieves a uniform hydraulic packing
of the media 44 by piston 40 which is desirable for uniform flow of
mobile phases passing through the stationary bed formed by the
compacted media 44. But this embodiment requires a long body 22 and
a long sleeve 46 which make the end column heavy, and which
requires more material than desired. The body 22, sleeve, end caps
24, 48 are made of metal, typically stainless steel, and that
material is not only heavy, but expensive. It is thus desirable to
reduce the length of body 22 and eliminate, if possible, piston
sleeve 46.
[0073] Referring to FIGS. 7-10, a second embodiment is described
which uses the same piston 40 described above, but which uses a
segmented body 122. For parts that are not changed the part numbers
are not altered and are the description is not repeated.
[0074] The body 122 is formed of two parts, a removable, upstream
tube 122a and a remaining downstream tube 122b. Both parts 122a,
122b are used for packing while removable tube 122a is removed for
use, as described later in more detail. The upstream tube 122a
forms a slurry chamber, while the downstream tube 122b forms the
column. Tubes 122a, 122b are releasably joined by a removable,
V-Band clamp. An optional wrenching surface 133 can be provided on
the outside of body 122.
[0075] The slurry tube 122b has a length sufficient to hold the
desired slurry media 44 prior to the media being packed.
Preferably, but optionally, the length is also sufficient to
accommodate at least a portion of piston 40. The upstream end 124
of column 122b is configured to seal against the downstream end 126
of slurry chamber 122a. The seal is designed to withstand the
hydraulic packing pressures, which typically range from 2000-6000
psi, but which can be larger or smaller depending on the particular
column and media. The seal is preferably a face seal between the
abutting faces of the bodies 122a, 122b. But the seal could be an
axial seal extending along the length of longitudinal axis 52, or
it could be both a face seal and an axial seal.
[0076] One illustrated seal is described. The mating ends of bodies
122a, 122b each have a wall 128a, 128b on the inside of the tubular
body 122a, 122b extending parallel to axis 52. Each wall 128a, 128b
forms a short cylinder. Each wall 128a, 128b also forms a recess
132a, 132b on the exterior of the wall. When the ends of the walls
128a, 128b abut each other, the recesses 132a, 132b face each other
and form a single annular recess that is large enough to
accommodate a ring seal, such as an O-ring seal for O-ring 134. The
interior corner of wall 128b has a chamfer 130. Adjacent each
recess 132a, 132b, and located away from the respective wall 128a,
128b, is a tapered recess 135a, 135b. Each tapered recess has a
trapezoidal cross-section.
[0077] When the ends 128a, 128b abut each other, a V-band clamp 136
engages the recesses 135 to hold the parts 122a, 122b together. The
V-Band clamp has two semi-circular or clamshell segments 136a,
136b, each of which has two projections 140a, 140b with tapered
sides configured to mate with one of the recesses 135a, 135b. The
clamshells segments 136a, 136b are fastened together, for example
by threaded fasteners 142 such as screws, with the projections
140a, 140b wedging into the mating recesses 134a, 134b to fasten
the segments 122a, 122b together. The seal 134 maintains a fluid
tight seal alone, or in cooperation with the V-band clamp 136. The
V-band clamp 136 also maintains the slurry chamber 122a and column
122b in coaxial alignment.
[0078] The removable slurry chamber 122a has an upstream end 124
with a chamfer 86 on the inside of the lip on the end of the
chamber.
[0079] Referring to FIGS. 9a, 9b and 11, when assembled the initial
use is similar to that of the first embodiment of FIG. 5. The
slurry chamber 122a and column 122b are joined by a V-band 136. The
downstream end cap 24 is placed on column 122b to hold the
downstream frit 30 in place. The joined slurry chamber 122a and
column 122b are placed in a holder with the upstream end of the
upstream tube 122a being open rather than covered. Preferably, but
optionally, the joined chamber 122a and column 122b are placed in
.a chuck 87 (FIG. 5) or a recess 174 in support 88 which holds the
joined columns so the centerline 52 aligns with the centerline of
the chuck. The downstream end of cap 24 can abut a support surface
88 as shown, or if the chuck 87 alone is used it can grip the
joined bodies 122a, 122b sufficiently for the following packing. It
is preferably to abut the column against support 88.
[0080] A predetermined amount of media 44 is placed in a beaker and
mixed with a fluid to form a slurry. The slurry is preferably
sonicated to remove air and further mix the media 44 and fluid. The
slurry is then poured into the opening of the slurry chamber 122a.
The slurry chamber 122a serves the purpose of a removable,
pre-compression chamber in this second embodiment. The flask is
rinsed with the fluid, preferably twice, and the fluid poured into
the slurry chamber 122a in order to ensure all the media is placed
into the joined bodies 122a, 122b. Additional fluid is added, if
needed to fill the fluid level to the chamfer 86 on the slurry
chamber 122a. It is undesirable to force air through the column, so
the fluid level is high enough to avoid air entrapment or a release
valve is provided. The outlet passage 26 is preferably not blocked
at this stage so fluid can exit through the outlet 26 under the
force of gravity.
[0081] The piston 40 is placed onto the piston sleeve 46 so the end
of the sleeve abuts the shoulder 69 on piston 40. Preferably mating
threads on boss 70 engage mating threads on the inside of sleeve 46
to form a threaded engagement that prevents relative axial movement
of the sleeve and piston. Advantageously a metal cap is placed over
the end of sleeve 46 to block fluid flow out of the upstream end
78a of tube 78. The hat-shaped frit 42 is placed in the piston, and
the upstream end cap 48 and thrust washer 50 are placed on the
piston sleeve 46. As desired, a locking mechanism is placed on the
sleeve 46. The piston sleeve 46 placed into a press 90 (FIG. 18).
The detent 82 can engage a mating releasable detent pin in the
press 90 to hold the piston sleeve 46 in place, along with any
locking mechanism and piston 40 connected to the sleeve 46. The
piston sleeve 46 is positioned in the ram 90 such that the
longitudinal axis of the sleeve coincides with the longitudinal
axis 52 of the body 22.
[0082] The ram 90 (FIGS. 5 and 18) then advances the piston into
open end of the body 122a, with the chamfer 86 helping to guide the
mating parts and accommodate slight misalignments. The advancement
of the ram 90 and piston 40 is slow during this initial engagement
portion. Preferably the movement of the piston 40 is paused before
the first seal 60 engages the body 122a in order to verify
alignment. Preferably a slight amount of excess fluid is forced
over the chamfered lip 86 in order to ensure no air is entrapped
between the frit 42 and the fluid.
[0083] The ram 90 advances the piston 40 into the joined bodies
122a, 122b. The pressure increases linearly, and slowly while the
piston 40 is in the upstream slurry chamber 122a because there is
enough fluid that the media 44 has not yet been compacted into a
stationary bed. The tubular chamber 122a thus effectively forms a
pre-compression chamber. The chamfer 130 on wall 128b at the
juncture of the bodies 122a, 122b helps avoid the catching the
seals 60, 62 and sealing wear ring 66. The chamfer 130 is
preferably small, because media 44 can collect in the chamfer.
[0084] The advancing piston 40 forces fluid out the outlet passage
26 while the frit 30 retains the media inside the downstream body
122b. When the fluid is largely expelled from the downstream column
122b the piston 40 begins to compress the media 44 at which point
the pressure rapidly increases as indicated by FIG. 6.
[0085] The ram 90 advances the piston 40 until a desired pressure
is reached at which point movement of the piston 40 is halted and
maintained in position. At that point the fluid is largely pressed
out through passage 26 and the media 44 is compacted to form a bed
of stationary phase for a desired use, preferably for
chromatographic analysis. At this point the packed tube could be
used for chromatographic analysis, but the ram 90 would have to
maintain the pressure, and that is undesirable as it restricts
mobility of the packed column 122b and restricts use of ram 90.
[0086] The length of the downstream column 122b is selected so that
the media 44 and preferably, but optionally, at least a portion of
the piston 40 is in the column 122b. Advantageously the seals 60
and 62 engage the wall 38 of the column 122, and preferably the
wear ring 66 also engages the wall of the column, so a substantial
portion of the piston is in the column 122b. The V-band 136 is then
released so the removable slurry chamber 122a can be moved out of
contact with the column 122b, while the piston is fastened to the
column 122b and while the pressure on the media 44 is maintained by
sleeve 46 and ram 90. The pre-compression chamber formed by slurry
chamber 122a is thus removable and does not form a portion of the
final assembled column 20 in this embodiment.
[0087] The piston 40 can be fastened to the column 122b various
ways. Conceptually the preferred mechanisms involve clam-shell or
split-ring devices which engage a flange or recess on the column
122b and also engage part of the piston 40 in order to prevent
relative movement of the piston 40 relative to the column 122b. One
way locking the piston in place relative to column 122b is shown in
FIG. 10. The piston 40 is pressed at least part way into the column
122b, preferably with the wear ring 66 and ridges 68a, 68b abutting
the inner. wall 38 of the column 122b. A locking collet 144 is
placed around a portion of the piston 40, preferably abutting the
upstream ridge 78a. The collet 144 acts as a piston compression
screw. Advantageously, but optionally, the exterior of the collet
144 has a threaded portion 146 and a wrenching surface 144 is also
provided, preferably on the upstream end of the collet. The collet
144 thus advantageously comprises a cylindrical tube having threads
on an outer surface, with the tube being split--preferably along a
longitudinal axis of the column 122b. A two-piece locking sleeve
150 then encloses a portion of the locking collet 144 and the
column 122b. The locking sleeve 150 serves as a piston retainer and
may be referred to as such. Preferably, but optionally, the locking
sleeve 150 is a clam-shell or split-ring configuration having a
protrusion 152 configured to mate with recess 135b in the column
122b. Optionally, the locking sleeve 150 is preferably configured
to mate with the exterior profile of upstream end of column 122b.
Further, the locking sleeve 150 optionally has a threaded portion
154 located to threadingly engage threads 146 on collet 144. The
threads 146, 154 are preferably, but optionally, multiple lead
threads, with double lead threads being preferred. The collet 144
can be threaded into the recess 154 before or after the split
locking sleeve 150 is joined together.
[0088] In use, after the upstream slurry tube or slurry chamber
122a is removed by sliding it up the piston sleeve 46. The two
halves of the locking sleeve 150 are then fastened together, as for
example, by threaded fasteners such as screws through holes 156 in
the locking sleeve 150. Alternatively, a hoop fastener encircling
the exterior of the sleeve 150 could be used, such as a hose clamp,
a wire, a ring, or a cylinder could be used.
[0089] After the two parts forming locking sleeve 150 are joined,
the collet 144 is then threadingly advanced or tightened in the
sleeve 150 until the downstream end of collet 144 pushes against
the ridge 78a on piston 40, and slightly increases the force
detected by ram 90. The ram is then removed from engagement with
shoulder 69, with the collet 144 and locking sleeve 150 maintaining
substantially the same preload as provided by the ram 90. The
packed column 122b is then removed from the chuck 87 ore recess
174, the downstream end plugged with plug 28 (FIG. 1), and the
metal cap on the upstream end is replaced, as desired.
[0090] The collet 144 provides an axially positionable or
adjustable device that accommodates variation in the position of
the piston 40 along longitudinal axis 52. The collet 144 is
preferably a unitary piece, or it can optionally be split into two
or more pieces. The split locking sleeve 150 provides a radially
locking device that engages the collet radially relative to axis
52, to prevent movement of the collet 144 along the longitudinal
axis 52. By providing a collet 144 and multi-part locking sleeve
150, the ram 90 and piston sleeve 46 can maintain compressive
pressure on the media 44 while the force needed to maintain that
pressure is mechanically transferred to the locking sleeve 150 and
column 122b without substantially releasing the pressure. While a
single piece collet 144 and two-piece sleeve 150 are described,
more than two parts could be used for each or the collet could be
two-parts.
[0091] The wrenching surface 148 on the collet 144 is shown as
being located on a flange that extends radially outward from axis
52 a distance greater than the inner diameter of wall 38 of column
122b. If the wrenching surface 148 is slightly smaller than the
diameter of inner wall 38 of the column 122b, then the collet 144
could fit through the inside of the upstream slurry chamber 122a.
Thus, it is believed possible that a single-piece collet 144 could
be placed on the sleeve 46 and pass through the upstream tube or
chamber 122a to be fastened to the locking sleeve 150 after the
V-band clamp 136 is released.
[0092] Referring to FIGS. 12-13, an alternative locking mechanism
is shown. The column 122b has a downstream end cap 24 and a body
wrenching surface 23 and an upstream end as described above with
recess 135b for receiving a part of the V-band clamp 136. Piston 40
is shown, along with collet 144 which acts as a compression screw.
In this embodiment the locking sleeve 150a has an interior
configured to conform to at least a portion of the exterior of the
upstream end of column 122b, and preferably with a protrusion 152
configured to engage at least the recess 135b in the column 122b.
The end 150a also has a threaded portion 154 configured to engage
threads 146 on the collet 144.
[0093] The exterior of each of the two locking sleeves 150a has a
substantially cylindrical lower portion 158 and a smaller sized
cylindrical upper portion 160. The two halves 150a are fitted to
engage the piston 40 and upstream end of column 122b. A holding
piece 162 is then slipped over the outside of the two pieces 150a
to prevent them from moving radially outward. The holding piece 162
has an interior profile shaped to mate with the exterior profile of
pieces 150a. The holding piece 162 has downstream end that is large
enough to pass over the outside of the lower portion 158, and has
an upstream end large enough to pass over slurry chamber 122a. The
interior of holding piece 162 nests over the exterior of locking
sleeve 150a.
[0094] As the collet 144 is screwed into the threads 154 and is
forced against the shoulder on ridge 78a, the pieces 150a will move
radially outward away from axis 52 so they push against the inside
of holding piece 156. Outward movement of the split ends 150a will
wedge against the holding piece so that frictional engagement
between the locking sleeves 150a and holding piece 162 will
restrain axial movement of parts 150a, 162, with the shoulder
formed by the different diameters of the upper and lower portions
158, 160 also restraining axial movement in one direction. The
holding piece 158 can be placed over the piston sleeve 46 before
the ram 90 pushes the piston 40 into the upstream slurry chamber
122a. After the chamber 122a is disengaged, the holding piece 156
passes over the chamber 122a to be fit over the end pieces 150a and
hold them in place.
[0095] Referring to FIGS. 14a and 14b, a further embodiment is
shown. This embodiment is as generally described above, but has a
two or more piece segmented locking or retaining sleeve 150
surrounding the compression screw or collett 144. The holding piece
162 is also segmented, preferably with two segments. The segments
enclose the collett 144 and the top end 124 of the column 122b to
hold them in relative position. The segments of the holding piece
162 are fastened together by screws, bolts or pins 142.
[0096] This construction eliminates the need to have the sleeve 46
(FIG. 5) remain with the packed column 20, and it eliminates the
need for a tube long enough to accommodate the length of sleeve 46.
The resulting column 20 is shorter, lighter, and simpler, uses less
hardware, and is less expensive. Moreover, the dynamic, hydraulic
packing of media 44 is more accurate and repeatable, the stationary
phase is more uniformly formed, and the bed density is
increased--while avoiding crushing the bed and creating fines. The
column performance is improved.
[0097] Further, the hydraulic packing of media 44 takes
significantly less time to achieve than conventional packing
methods which continuously run slurry through the tube to pack the
tube, by a factor of about 10 to 100 times faster. The tubes 22,
122 can be packed to the desired pressure in less than a minute for
tube diameters of an inch or less and lengths of a few inches or
less.
[0098] Moreover, less media 44 is used, and the media is expensive.
The prior continuous flow (slurry) packing technique can have up to
about 40% of the media remaining in the tube or chamber used with
the packing equipment.
[0099] Still further, the dynamic, hydraulic packing by piston 40
compresses the media 44 to form a stationary bed of compressed
media, and that compressed bed of media is locked into position
without being allowed to relax or expand. The locking of the bed
into the desired compression is achieved in the first embodiment by
locking the piston sleeve 46 into position in order to hold the
piston 40 in position. In the second embodiment the piston 40 is
locked into position and then the piston sleeve 46 is removed. In
both embodiments the pressure exerted by piston 40 on the bed of
media 44 is preferably maintained substantially unchanged. Actually
because the locking mechanism in both instances preferably is
actuated until a piston movement or slight pressure increase is
detected by the ram 90, the locking pressure is preferably slightly
higher, preferably within a fraction of a psi higher, and less
preferably within a few psi or tens of psi higher than of the
packing pressure at which the ram 90 stops moving. Because the
pressure on piston 40 is electronically monitored by the ram 90
(e.g., through strain gauges, pressure transducers, etc.), it is
possible, but not preferable, to lock the piston 40 at a pressure
greater than or less than the pressure at which the ram 90
initially stops the compression.
[0100] Advantageously, no springs are interposed between the piston
and the locking end 48 and locking sleeve 150 which hold the piston
40 and bed of packed media 44 in compression.
[0101] The fits 30, 42 are made of sintered metal, or polymerized
PEEK. The two-diameter frit 42 allows fluid distribution across the
entire stationary phase provided by the packed media 44. The outer
diameter of frit 42 is smaller than the inner diameter of wall 38
to avoid scratching the wall as the fit 42 is moved by press 90 and
piston 40 along the wall. The hat shaped frit 42 allows the frit to
extend across substantially all the interior diameter of the tube
22, 122b, and to extend across the entire stationary bed formed
from media 44. That provides more uniform distribution of the
mobile phase and sample over the media 44, and that is especially
useful when the columns 20 are short. Further, the boss 58 allows a
substantial portion of the frit, about 70-80% to be thickened to
better withstand packing pressures, and provides a thinner
peripheral rim of thinner material. The fit 42 is preferably a
unitary fit formed into the hat-shaped structure at the time of
manufacture. Alternatively, but less preferably, the frit 42 can be
formed from placing a larger diameter frit abutting a narrower
diameter frit. A stainless steel frit 47 having a boss 58 of about
3.5 mm axial thickness, with a flange 56 having about 1.3 mm axial
thickness, for a flange diameter of about 21 mm and a boss diameter
of about 18 mm, is believed suitable for a porosity of about 2
microns. The frit allows passage of a fluid containing substances
in solution to be separated while not allowing solid particles in
the chromatographic medium to pass. Ideally, radial grooves inside
the frit or on an upstream surface of the frit allow the solution
to spread more evenly across the surface of the fit to help more
evenly spread the fluid across the bed of chromatographic media
44.
[0102] The stepped-diameter frit 42 can be made by taking a disk
having the desired maximum thickness and diameter, and then turning
the smaller diameter boss 58. This part can also be molded or
sintered of metal, and possibly of ceramic. Preferably the upstream
side of the boss 58 and the downstream facing side of the flange 56
are porous, with the edges and the annular space between boss 58
and the periphery of the larger flange 56 being substantially
impervious to fluid flow.
[0103] The seal 60, and any additional seals, are sufficiently
fluid tight to sweep any media along the length of the chambers 22,
122a, 122b. The seal 60, and any optional further seals are
configured for the desired packing and operating pressures which
typically range from 1,000-6,000 psi to 10,000 psi and possibly
higher. While specific seal configurations are shown, other seal
configurations, seal arrangements, and seal materials can be used
within the spirit and scope of the present invention.
[0104] The seal between the ends of chamber 122a and tube 122b can
be simplified greatly if the downstream tube 122b is sized so the
maximum pressure increase occurs after the seal 60 or seals 60, 62
and 66 have passed the chamfered 130 on the tube 122b. That
simplifies the construction, assembly and disassembly of the
chamber 122a and tube 122b. The chamfer 130 is preferably formed
only on the downstream tube 122b in order to avoid forcing media
into the joint between chamber 122a and tube 122b as the piston
passes the chamfer 130.
[0105] Referring to FIGS. 9a and 9b, a further embodiment is shown.
An upstream tube or chamber 122a is joined to a downstream tube or
column 122b by a split retainer. The top or upstream end 124 of the
column 122b has a top end recess 135b and the bottom or downstream
end of the upstream tube or chamber 122a has a bottom end recess
135a. A threaded collet or bed compression screw 144 threadingly
engages mating threads on the inside of the upstream end of the
column 122b. The piston 40 (FIG. 13) is urged against the media bed
by the compression screw 144.
[0106] The locking sleeve 150 (FIG. 13 or FIG. 10) has a threaded
upstream end to mate with the exterior threads on bed compression
screw 144 or collet 144. The sleeve 150 has a downstream end
configured to engage the recess 135b, or the rim forming the recess
135b, to restrain axial movement of the sleeve 150. The sleeve 150
thus restrains movement of the collet 144 relative to the column
122b along the longitudinal axis 52. An outer sleeve or holding
piece 162 holds the split sleeve 150 from radial expansion. The
outer sleeve 162 is also a split or clamshell design with the two
or more pieces held together by threaded fasteners 142 extending
through aligned holes in the mating parts of the outer sleeve 162.
The interior of the outer sleeve 162 is configured to generally
conform to the exterior of the split locking sleeve 150 or collet.
The outer sleeve 162 holds the parts of the sleeve 150
together.
[0107] The initial use is as described above wherein a V-band clamp
136 holds the upstream slurry tube 122a and downstream column 122b
in alignment during filling and packing as the piston 40 (not
shown) compresses the media to form a chromatographic bed. The
V-band clamp is removed.
[0108] Referring to FIG. 14, the split collar 150 is then placed
around the column 122b to engage the recess 135b. The split collar
150 serves to retain the piston in place and for ease of
understanding the collar 150 will be referred to as a piston
retainer in describing the operation of FIG. 14. The bed
compression screw or sleeve 144 is then slid down so its threads
engage the threads on the piston retainer 150. The bed compression
screw or sleeve 144 is tightened until the piston is locked in
place. As the bed compression screw is tightened it pushes in an
upward or upstream direction against the piston retainer 150 and
recess 135b. The inclined surfaces on the recess 135b allow the
split piston retainer 150 to move outward from axis 52, and the
outer sleeve 162 restrains that motion, locking everything in
place. The packed column 122b can then be removed from the press
90, and flow through the column blocked by plugs 28 and cap 80.
[0109] Instead of using a split outer sleeve 162 and fasteners 142
to restrain outward expansion of the split piston retainer 150, the
piston retainer could be held together and held in place by wire,
by an encircling ring slid axially over the retainer 150, or by a
cylindrical sleeve slid axially over the retainer 150. The use of
single-piece rings or sleeves is simpler in that it avoids the use
of split parts and fasteners to hold the split parts together. But
the single piece rings or sleeves require they be positioned on the
longitudinal axis 52 before bed compression begins, and that can
complicate arranging all the parts on the axis while still
accommodating compression by the press 90.
[0110] Referring to FIGS. 15-17, a further embodiment is shown. The
downstream end cap 24 has a plurality of flat surfaces 166 and
corners 168 that can be used to align the column 122a for packing
with the press 90. Preferably, but optionally, the split locking
sleeve 150 is elongated to extend along a substantial length of the
column 122a, and for columns shorter than 50 mm a substantial
length is about half or more. For longer columns the length is
shorter and does not comprise a substantial length The locking
sleeve 150 has internal threads 154 configures to engage threads on
the piston compression screw or collet 144. A protrusion 152 mates
with recess 135b in the column 122a to prevent relative axial
motion of the piston retaining sleeve 150 and the column 122a. The
protrusion 152 is preferably shaped to conform with the shape of
recess 135b and more preferably has inclined walls to wedge
radially and form a tight fit that restrains axial motion. The
locking sleeve 150 preferably conforms to the distal end of the
column 122a to provide further engaging surfaces that restrain
relative axial movement between the sleeve 150 and column 122a. The
locking sleeve 150 has a cylindrical exterior along its length,
with a reduced diameter adjacent the threads 154.
[0111] The upstream end cap 48 preferably, but optionally, has
similar flats 166 and corners 168 as does the downstream end cap
24. The upstream end cap 48 forms the holding piece 162 to confine
radial expansion of the split locking sleeve 150. This is achieved
by having an interior recess configured to conform to the exterior
of the locking sleeve 150, or to conform to substantial portions of
that exterior. As illustrated, a number of mating protrusions and
recesses can be used to provide resistance to axial movement of the
locking sleeve 150 relative to the column 122a.
[0112] When the parts of the locking sleeve 150 are positioned to
engage the column 122a, the holding portion 162 is moved axially to
fit over the locking sleeve 150 and prevent radial expansion. As
the collet 144 engages threads 154 and is tightened to abut piston
40, the tightening of the mating threads will cause radial motion
of the locking sleeve 150, which abuts the holding piece 162 to
frictionally lock the parts together.
[0113] Upon suitable tightening of the collet 144, the press 90 is
disengaged and the column 122a removed. An end cover 170 can
optionally be placed over a larger diameter recess in the holding
piece 162 (that forms the end cap 48). The larger diameter recess
allows easier access to the wrenching surface 148 on the collet
144. As desired, suitable plugs or caps are added to block the
fluid flow channels through the packed column 122a.
[0114] The flats 166 and/or corners 168 allow the column 122a to be
placed in a recess 174 (FIG. 11) in support 88 where the recess is
configured to conform to the flats and/or corners, in order to
align the longitudinal axis of the column 122a with the
longitudinal axis of the press 90. That avoids the need for a chuck
87. Any suitable number of flats and/or corners can be used as long
as a suitable alignment is achieved.
[0115] The embodiment of FIGS. 15-17 also has a modified piston 40
as shown in FIGS. 3a and 3b. The boss 70 has no threads, and
instead has a detent groove 172 which mates with a detent pin or
detent ring (not shown) in the piston sleeve 46 to releasably hold
the piston in the press during use. The detent ring and groove 172
are easier to use than mating threads on the piston sleeve 46 and
boss 70 as shown in FIGS. 1 and 3a.
[0116] As used herein, the terms upstream and downstream are
relative to an initial packing orientation for the columns 20, 122.
The relative directions can be referred to as first and second, and
the directions themselves can be reversed, and the parts referred
to can also be reversed. The frits 30, 42 are formed of sintered
metal (stainless steel, titanium or other suitable porous
material).
[0117] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention, which
may be embodied in various forms. Therefore, specific structural
and functional details disclosed herein are not to be interpreted
as limiting, but merely as a basis for the claims and as a
representative basis for teaching one skilled in the art to
variously employ the present invention in virtually any
appropriately detailed structure.
[0118] The above description is given by way of example, and not
limitation. Given the above disclosure, one skilled in the art
could devise variations that are within the scope and spirit of the
invention, including various ways of locking the piston in place
inside the column 20 and various ways to releasably join the slurry
chamber 122a to the column 122b. Further, the various features of
this invention can be used alone, or in varying combinations with
each other and are not intended to be limited to the specific
combination described herein. Thus, the invention is not to be
limited by the illustrated embodiments.
* * * * *