Note: Descriptions are shown in the official language in which they were submitted.
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This application is a divisional of Canadian
Patent Application 297,609 filed February 23, 1978.
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Background of the Invention: ~
.~
In liquid chromatography it has been a problem to
- 5 provide means to inject discrete liquid samples into a liquid
chromatograph column with a minimum of dilution of "peak- :~
spreading" as it is called in the chromatographic art. Appli- :
cant set out to provide an apparatus useful in the injection to - .
i an l.c. column sequence of a large number of liquid samples.
Such sequential testing apparatus is known to be useful in
such testing procedures as quality control testing in the
pharmaceutical industry and the like.
In general, the schematic injection scheme selected
by the Applicant is that disclosed in U.S. Patent 3,916,692
to ~brahamS.
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Applicant, in adapting that scheme to a reciprocating sampling
conduit adapted to enter a series of sample containers en-
countered a number of design problems, the most critical of
which was the sealing oE the outlet of the reciprocating
5 sample conduit into the liquid chromatographic flow circuit. -
It is to be understood that in the chromatographic pro¢esses
being discussed, fluids are handled at pressures of 5000
psig and even higher. ;-
As will be described below, the particular
apparatus constructed to meet the various problems meets,
and even surpasses, the prior standard of performance
established by the apparatus descri~ed in U.S. Patent 3,916,692.
In liquid chromatography and numerous other analyti-
cal procedures in the chemical and medical arts, it is
desirable to have a large number of samples handled sequenti-
ally on the same apparatus. In such cases, a conduit, often
a hypodermic needle or the like, is dipped into a series o
different samples. In such situations, there is an increased
danger of cross-sample contamination because of sample from
an earlier operation being dipped into a second operakion.
Ik has been a problem in the art to provide a
drip-proof, conduit-cleaning procedure which can be rapidly
used without slowing the sample ~eeding procedure. As w:ill be
described below, Applicant has, for the f.irst time, achieved
such a drip proof, contamination avoiding, conduit cleaning
means. This apparatus is particularly valuable in conjunc-
tion wlth automatic liquid sampling apparatus in liquid
chromatography.
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Summary of the invention: -
' Therefore, it is a principal aspect o the inven-
tion to provide an improved injector valve mechanism for use
in feeding of discrete samples of liquid to analytical appar- -
atus, especially to liquid chromatographic apparatus. It
is a particular aspect of the invention to provide such
apparatus adapted for automatic operation.
Another aspect of the invention is to provide a
liquid sample injector and valve mechanism of the type which
is provided with a self-cleaning sample conduit.
Still another aspect of the invention is to provide
liquid sampling apparatus which comprises an automatically
cleaned, non-drip reciprocating sample needle and means to
discharge the needle,directly into a sample loop withou~ any
substantial leakage of the sample around the conduit even
at pressures o the order of 5000 psig.
Another aspect of the invention is to provide,a
novel seal means to facilitate the sealing of the opening o
the reciprocating conduit within the injector-sample flow
~0 circuit.
'~ Further aspects of the invention include providing
the individual novel and improved seal means and wash means
described above and also providing ~he novel processes by
which all of the above-mentioned injector valves, washing
means, and seal means are operated and constructed.
Other aspects o~ the invention will be o~vious to
those skilled in the art on their r~ading o this invention.
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Moreover, it should be noted that, in the realisa-
tion of the aforesaid aspects, an injector was constructed ;~
which actually outper~orms the best previous injecto'rs in
terms of the precision with which samples are discharged
from the injector into a liquid chromatograph or other analyti-
cal devices. In chromatography, this precision results in
sharper resolution of peaks representing various chemical
compounds.
The above aspects have been substantially achieved,
with respect to the injector valve, by the construction of
a novel apparatus.
Accordingly, this invention provides apparatus for
washing a sampling conduit comprising
(a) a housing in relation to which said sampling
conduit moves up and down, said housing comprising porous
wiping means in snug contact with said needle;
(b) means to distribute a supply of wash liquid
to said needle through said porous wiping means;
(c) means to move air through said porous wiping
means at a position below said wash-liquid supply means;
and
td) mean9 to remova aid air ~rom 9aid washing
means at a position below said wash-liquid supply means.
This invention further provides a process for washing
a liquid sampling conduit comprising the steps of
(a) maintaining the liquid-wetted exterior of
said conduit in snug contact with a relativaly soft porous
mass;
(b) reciprocating said conduit in relation $o
said mass;
(cl supplying a cleaning liquid to said surface
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through one portion of said mass and
(d) pulling air through a second and lower portion
of said mass; said air preventing leakage of any solvent
from said porous mass.
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Illustrative Embodiments of the Invention: ~
.
In this application and accompanying drawings there
is shown and described a preferred embodiment of the invention
and suggested various alternatives and modifications thereof,
but it is to be understood that these are not intended to be
exhaustive and that other changes and modi-fications can be
made within the scope of the invention. These suggestions
herein are selected and included for purposes of illustration
in order that others skilled in the art will more fully
understand the invention and the principles thereof and will
be able to modify it and embody it in a variety of forms,
each as may be best suited in the condition of a particular
case.
In the Drawin~s:
Figure 1 is a novel injectox valve assembly con-
structed to facilitate automatic sample injection.
Figure 2 is a detailed elevation, partly in section,
of that portion of the injector valve at which (a) the sampl-
ing conduit is jointed to the fluid flow pattern of the rest
of the injector and (b) the sampling condult is automatically
washed.
Figure 3 is a plan view o~ the r~sln part o~ a
wiper seal shown in Figure 2.
Figure 4 is a section of the stressing insert used
with, and forming part of the seal shown in Figure 3.
Figure 5 is a schematic explanation of the function
of wiperseals shown in Figure 3.
Figure 6 illustrates a sampling conduit useful
with the present invention.
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Referring now to Figure 1, it is seen that injec-
tor valve assembly 10 comprises a number of connections to
various conduits as is generally known in the liquid chromato-
graphic art. Thus, conduit 12 runs from a pump (not shown)
supplying a carrier solvent into the injector valve assembly
10 and, in a first mode of operation~ cummunicates with an
outlet conduit 14 and proceeds into a chromatographic column
(not shown). To do this, the liquid must proceed through
needle-valving block 20, best seen in Figure 2. Block 20
comprises an inlet port 22 and an outlet port 24 communicating
with conduits 12 and 14, respectively. A sampling conduit
means, a modified hypodermic needle 26 is adapted for recipro-
cating vertical movement in block 20. When the needle is in
its lowered position, there is an annular space 26(a) about
the needle around which fluid can flow from conduit 22 to
24, When the needle is raised the lower portion thereof, i.e.
portion 27, is a plug means which effectively seals the fluid
with lower seal 70.
In the first mode of operations, a valve 16 in
conduit 18 is closed. When valve 16 is open~d to ~stabllsh
the sample in~ection mode, most liquid from the pump will
leave conduit 12 and Elow thxough condul-t 18, and conduLt 19,
into extensible. tubing l9(a) and thence to needle 26, to
port 24, conduit 14 and to the chromatographic column.
Figure 6 shows needle 26 with its outlet port 28
preferably in register with the port 24. The bottom
portion 27 of the needle is solid and forms no part of the
needle conduit.
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Referring again to Fi~ure 1, it is seen that the
connection means 40 of needle 26 to conduit l9(a) is formed
within a steel insert block 42 which, in turn, is carried in
an aluminum piston 44. Piston 44 is air operated. The piston
44 moves in a cylindrical housing 30 having a top housing
plate 32 and lower housing plates 34 and 36. The lower plates
34 and 36 have a central channel 60 which also continues into
- block 20 and in which sampling conduit 26 reciprocates. Air
to raise the piston 44 (and, of course, needle 26 connec~ed
thereto) enters conduit 46; air to lower the piston enters
conduit 48. These air connections are connected to a pneu-
matic control system which is not shown because it forms no
part of the invention as claimed herein and because those
skilled in the art can readily manufacture and adapt such
systems to meet their particular requirements. The piston
is provided with lip seals at 50 and 52. Travel of the piston
can be adjusted by modifying the vertical position of a
stop bar 54 with positioning nut 56. As indicated above, the
ideal position is such that port 28 from needle 26 is in
register with port 24.
Connection 40 comprises ferrules on each of needle
26 and conduit tubing l9(a). These form a butt connection
utili~ing fittings already well known in the ~hromatography
art.
Figures 2 through 5 all illustrate an important
sealing structure on which the combination of simplicity and
high-pre~sure capability of the invention depends. At
positions just above and below that point in needle channel
60 to which conduit 28 can be raised in order to communicate
with port 24 it is necessary to have an efficacious seal
means that will be able to handle pressures to 5000 -
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6000 psig, will be able to do so without binding of the
needle 26, and will be able to do so for a prolonged period
of time without replacement. In this connection, it should
be understood that the apparatus of the invention is intended
to be utilized in analytical work wherein it handles,
routinely, samples as small as 5 microliters or smaller.
Moreover, it must be realized that the chemical sensitivity
of the analytical process being used is such that most
organic materials of construction cannot be utilized because
of chemical contaminants which would be leached therefrom. ;~;
Thus the problem faced by the Inventor combined a rare
combination of hydraulic, chemical and mechanical restraints.
Nevertheless, the problem has been successfully solved by
utilization of combination of seals 70 comprising a sleevQ
72 formed of a fluorocarbon-based material. It is desirable
that the fluoroçarbon be reinforced; otherwise shredding
or peeling of the seal may result. Advantageously, the
material will have tensile and compressive strengths exceed-
ing 1600 and 1200 psi respectively. A suitable material
is well known in the art and sold under the trade designation
RULON J (Trade Mark) by Dixon Corporation. Stress rings 74 may be
separate pieces as illustrated for the highest and lowest
rings of Figure ~ herein. Indeed, in the case of the rings
nearer the ports 22 and 2~, it is des~rable to fabxicate the
stressing rings into block 20.
Figure 3 shows the sleeve 72 of seal 70. It has an
outside diameter of 0.152 indhes and an inside diameter of
0.059 inches (when used with a needle of a 0.057 inch outside
diameter). These diameters are concentric within 0.003 inches.
It is to be noted that the sleeve does not comprise any
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indentation as it is fabricated. In the illustrated embodiment
of the invention, sleeve 72 is 0.120 inches long and is formed
of a resin (as opposed to glass or asbestos) reinforced.
This material has superior functional characteristics when
compared to most reinforced halogenated polymer resins. It
is also characterized by a minimum tensile strength of 2000
psi and a compressive strength of about 1430 psi.
Figure 4 illustrates the stressing ring. In the
illustrated embodiment of the invention, it comprises a sleeve-
deforming surface 80 bevelled to a 90 angle, has a bore of
O.0165 inch diameter, and an outside diameter of 0.151 inches.
The flat side wall 82 is 0.05 inches long.
Figure 5 is a highly schematic diagram o~ a portion
of sleeve 72 of seal 70 showing how strain applied to sleeve
72 through rings 74 cause the seal to push out at 86 tend-
ing to seal against needle 26. As will be seen in Figure 2,
this pressure is achieved as the result of compression
between washer housing 88 wherein an extension 90 is threaded
into block 20 to bear on the bottom most seal ring 74 which,
in turn, pushes the lower seal 70 against a portion 92 o
block 20. Similarly, the uppermost o seals 70 is com-
pressed downwardly by a positioning ~leeve 94 which, like ex-
tengion 90 i8 arranged concentrically with needle 26.
It is to be noted that in normal liquid chromato-
graphia procedures, there is usually no problem in cleaning
the ln~erior conduit sampling needle 26. After a sample has
been sucked into needle 26 by a suction syringe 100, and the
needle has been pneumatically raised to its proper discharge
point, i.e. with orifice 28 facing outlet conduit 24; then
valve 102 is closed, valve 16 is opened and most solvent
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flow goes through conduits 18 and 19, l9ta), etc. This
flow not only sweeps the sample into chromatographic column
but it also continues for a sufficient time thereafter to
assure that no substantial sample contamination remains in
the needle. Such a delay is normally inherent in the nature
of column chromatography.
AS illustrated in Figure 2, applicant has under-
taken to provide a novel, dripless, sample-conduit washing
means 110.
Washer 110 comprises a solvent supply reservoir
112 and a vacuum source 114, both shown schematically on
Figure 2. Within washer housing 88, is a bore 89 through
which needle 26 moves vertically during operation of the
sample injector. About bore 89 are mounted two highly porous
plugs 116 and 118 of a sintered material, e.g. polypropylene,
polytetra~luoroethylene, or the like. The plugs have pores of
about 20 to 40 microns in size. These are separated by a
spacer member 120. They are snug against the needle, but
without constricting its vertical movement. Although the
operation of the washer may be timed manually, it is desirable
that it be automated to (1) supply solvent to plug 116
when the needle i8 down and (2) apply a vacuum to plug 118
when thc needle i9 up.
WasherllO, therefore, provide~ means via plug 116
to wet the needle while it is depressed and wipe the needle
with solvent as the needle rises. Any excess solvent ~lows
through the annular space 121 between spacers 116 and 118
- and is distributed within lower plug 118 and carried away
in an air stream pulled upwardly through plug 118 and towards
vacuum source 114. This procedure avoids any dripping of
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3 ~37~7~
solvent from the washer. Plug 118 also forms means to wipe
the needle as it moves upwardly ouk of the sample bottle.
It will be apparent to those skilled in the art that
the drawings are schematic. For example, the conduits used
in liquid chromatography are generally smaller than those shown.
Moreover, to simplify the drawingsj the fittings have been
omitted as at ports 22 and 24. However, such fittings are
well known in the art and form no inventive aspect of the
present disclosure.
There is substantial advantage in having the
orifice 28 of needle 26 directly face port 24. However, such
relative placement of orifice and port substantially reduce
- the risk of a premature loss of meniscus liquid from the face
of the orifice before the intentional sample outflow from
the sampling conduit.
It is also to be understood that the following claims
are intended to cover all of the generic and specific features
of the invention herein described and all statements of the
scope of the invention which might be said to fall therebetween.
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