Liquid purification or separation – With means to add treating material – Chromatography
Reexamination Certificate
2001-06-01
2004-01-20
Therkorn, Ernest G. (Department: 1723)
Liquid purification or separation
With means to add treating material
Chromatography
C210S656000, C096S101000
Reexamination Certificate
active
06679989
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present application relates generally to the field of guard columns for high-pressure liquid chromatography (HPLC) devices. Guard columns are generally used to protect HPLC columns from physical or chemical contamination.
2. Description of the Related Art
High-pressure liquid chromatography (HPLC) is a process used for separating one or more compounds from a chemical mixture. The HPLC process consists of passing the mixture through a stationary packing material, under the influence of a high-pressure transport liquid, and separating the compounds by selective affinity, sieving, absorption or partition. The packing is typically housed within a thru-bored section of a body of a column and is typically held in place by frits at either end of the body.
FIG. 1
illustrates a typical HPLC apparatus
10
according to the related art wherein a chemical mixture is injected into the HPLC apparatus
10
through an injection apparatus
300
. The mixture first passes through the frits
120
,
140
and packing
115
of a guard column
30
. Then, the mixture is “funneled” through a narrow opening of a capillary connector
40
that is located between the guard column
30
and an HPLC column
20
. From that point, the mixture flows through the frits
180
,
200
and packing
170
of the HPLC column
20
and the components of the mixture can then travel through an exit apparatus
340
after which they can be measured, collected, redirected or disposed of.
The typical HPLC apparatus
10
illustrated in
FIG. 1
shows the guard column
30
contained within a housing
45
and held in place by a threaded top end fitting
310
. The top end fitting
310
is screwed onto an end of the housing
45
. Because of the extreme pressures sometimes used to conduct HPLC processes (e.g., pressures up to and above 6,000 pounds per square inch (psi)), the top end fitting
310
is typically screwed to the housing
45
using wrenches or other methods of supplying high torque.
The injection apparatus
300
through which the mixture enters the HPLC apparatus
10
is sheathed within the top end fitting
310
. A small region of the top end fitting
310
can form a top end fitting pathway
12
through which the mixture travels before flowing into the guard column
30
.
The guard column
30
is positioned between the top end fitting
310
and the housing
45
. To prevent leaks, a guard column top seal
90
is placed between the guard column
30
and the top end fitting
310
and a guard column bottom seal
70
is placed between the guard column
30
and the housing
45
.
The guard column
30
is removable and replaceable. To remove the guard column
30
, the top end fitting
310
is unscrewed from the housing
45
and the guard column
30
is pulled out. The guard column
30
can then be inspected and, if necessary, replaced. An advantage of a replaceable guard column
30
is that the HPLC column
20
, which is substantially more expensive than the guard column
30
, does not have to be replaced as often, if ever. The guard column
30
traps impurities or particulates in the sample mixture or in the transport liquid before the impurities or particulates can reach the HPLC column
20
and thereby extends the operable lifetime of the HPLC column
20
.
The capillary connector
40
can be a piece of tubing or other device that connects the guard column
30
to the HPLC column
20
. It is, according to
FIG. 1
, held in place by a top capillary fitting
22
and a bottom capillary fitting
23
.
The capillary connector
40
abruptly changes the cross-sectional area of the path of the mixture by forcing the mixture to flow from the thru-bore section of the guard column
30
to the relatively narrow opening of the capillary connector
40
. Then, the mixture passes through a relatively large thru-bore section of the HPLC column
20
. The sudden changes in the cross-sectional area of the flow path disrupt the flow of the mixture, cause unwanted mixing and blending of the mixture, and lower the capability of the HPLC column
20
to separate compounds from the mixture (i.e., causes band-spreading).
An improvement to the HPLC apparatus
10
design depicted in
FIG. 1
exists in the related art. This improvement eliminates the capillary connector
40
by making the guard column
30
“integral” to the HPLC column
20
.
FIG. 2
illustrates such an alternative HPLC apparatus
10
, according to the related art, wherein a chemical mixture is injected into the HPLC apparatus
10
through an injection apparatus
300
. The mixture first passes through the frits
120
,
140
and packing
115
of a guard column
30
that sits in a guard column housing
45
. Then, the mixture is “funneled” through a narrow opening that is located on the exit end of the guard column housing
45
. From that point, the mixture flows through the frits
180
,
200
and packing
170
of the HPLC column
20
and the components of the mixture can then travel through an exit apparatus
340
, after which they can be measured, collected, redirected or disposed of.
The components of the HPLC apparatus
10
illustrated in
FIG. 2
are contained within an assembly comprised of an externally threaded bottom end fitting
360
and an internally threaded top end fitting
310
. This assembly is held in place by engaging two upper grommets
350
that fit into an upper groove
380
that is machined into the outer wall of the HPLC column
20
. Because of the extreme pressures sometimes used to conduct HPLC processes (e.g., pressures up to and above 6,000 psi), the top end fitting
310
and the bottom end fitting
360
are typically screwed together using wrenches or other methods of supplying high torque.
The injection apparatus
300
through which the mixture enters the HPLC apparatus
10
is sheathed within the top end fitting
310
. A small region of the top end fitting
310
can form a pathway
12
through which the mixture travels before flowing into the guard column
30
.
The guard column
30
is enclosed in a guard column housing
45
and positioned between the top end fitting
310
and the HPLC column
20
. To prevent leaks, a guard column top seal
90
is placed in the guard column housing
45
above the top end of the guard column
30
. This guard column top seal
90
mates with the exit end of the top end fitting
310
to form a leak-tight seal. An HPLC column top seal
100
is placed inside the HPLC column
20
to mate with the exit end of the guard column housing
45
to form a leak-tight seal.
The guard column
30
and the guard column housing
45
are removable and replaceable. To remove the guard column
30
and the guard column housing
45
, the internally threaded top end fitting
310
is unscrewed from the externally threaded bottom end fitting
360
and the guard column
30
and the guard column housing
45
are pulled out. The guard column
30
can then be inspected and, if necessary, the guard column
30
and the guard column housing
45
can be replaced.
The guard column housing
45
abruptly changes the cross-sectional area of the path of the mixture by forcing the mixture to flow from the thru-bore section of the guard column
30
to the relatively narrow exit opening
42
of the guard column housing
45
. Then, the mixture passes through a relatively large thru-bore section of the HPLC column
20
. The sudden changes in the cross-sectional area of the flow path disrupt the flow of the mixture, cause unwanted mixing and blending of the mixture, and lower the capability of the HPLC column
20
to separate compounds from the mixture (i.e., causes band-spreading).
Below the guard column housing
45
is the HPLC column top seal
100
that is placed inside the top of the HPLC column
20
. An HPLC column bottom seal
110
is placed between the HPLC column
20
and an exit fitting
375
that sheathes the exit apparatus
340
. The exit fitting
375
, when screwed onto a lower HPLC column fitting
365
, holds the exit fitting
375
and the HPLC column
20
together with the use of two lower grommets
385
that
Machamer Clyde
Willis Frank
Agilent Technologie,s Inc.
Therkorn Ernest G.
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