Apparatus for preparing a liquid sample

Method and apparatus for preparing a liquid sample for combustion and analysis in an elemental analyzer. In order to avoid damage to the quartz combustion tube and ladle by molten aluminum, the sample is placed in an aluminum foil vial which is crimped and placed in turn in an open ended capsule of nickel or other non-reactive metal. The capsule is then distorted by a novel encapsulator to partially obstruct the open end and retain the liquid sample vial therein during the combustion process.

BACKGROUND OF THE INVENTION 
In U.S. Pat. No. 4,055,259 there is disclosed an apparatus for transporting 
small solid samples into the combustion chamber of an elemental analyzer. 
Analyzers of this type normally combust a sample at a very high 
temperature (1000.degree. C.) in an oxygen atmosphere. The products of 
combustion are then analyzed to detect the presence and amount of 
particular elements, primarily carbon, hydrogen, and nitrogen. As 
disclosed in that patent, solid samples are usually placed within capsules 
of platinum or other non-reactive metals for subsequent combustion. 
When dealing with liquid samples, certain unique problems arise due to the 
fact that the samples, which may be highly volatile, must be sealed and 
contained prior to combustion. Such samples may be successfully contained 
within an aluminum foil vial which is thereafter sealed by crimping. Upon 
exposure to combustion temperatures, the aluminum melts or oxidizes 
releasing the liquid for combustion. The problem, however, is that the 
aluminum must be kept from contact with the quartz tube of the combustion 
chamber or with the quartz ladle which is employed to insert the foil 
vial. This is because the quartz is damaged by the molten aluminum and, 
when this occurs, the only remedy is to replace the quartz. This is 
expensive and results in extended down time of the analyzer. One method 
which has been employed to overcome this problem involves the use of a 
"boat" of non-reactive metal. The boat, however, occasionally tips, 
spilling the sample. 
Accordingly, it is a primary object of the present invention to provide a 
method for preparing a liquid sample which overcomes the disadvantages set 
forth above. Another object of the present invention is to provide an 
apparatus useful in carrying out such method. 
SUMMARY OF THE INVENTION 
The invention comprises a method of preparing a liquid sample for 
introduction into a combustion chamber by providing a substantially 
cylindrical metal foil vial having a closed end and an open end. The 
liquid sample is introduced into the vial which is then crimped at its 
open end. A substantially cylindrical metallic capsule is provided which 
is larger than the foil vial and has a closed end and an open end, the 
closed end defining a small hole to permit gas passage therethrough. The 
foil vial is placed within the capsule with the crimped end of the vial 
near the open end of the capsule. The capsule is then distorted to 
partially obstruct its open end to retain the liquid vial therein. 
In carrying out the method of this invention, there is provided an 
apparatus for forming the end of the cylindrical metal capsule. The 
apparatus includes a base and a vertical post extending upwardly from the 
base and terminating in a capsule supporting end. A capsule containment 
member, which defines a cylindrical passage therethrough, slidably engages 
the post. Means are provided for selectively supporting the containment 
member in either a raised, capsule-enclosing, position or a lowered, 
capsule-releasing, position. A capsule end forming tool is supported by 
the base for vertically reciprocating movement to engage a capsule 
enclosed within the containment member. Means are provided for selectively 
moving the tool into and out of engagement with an enclosed capsule.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
With particular reference to FIG. 1, there is illustrated a metal foil vial 
10 in the process of receiving a liquid sample by means of a syringe S. 
Vial 10 is basically cylindrical and has a closed convex bottom 12 and an 
open top 14. It is quite small and may have, for example, a capacity of 
approximately 3 microliters. After receiving the sample liquid, the vial 
is closed and sealed by means of a crimp 16, as shown in FIG. 2. This may 
be done by a crimping tool of a type well known in the art. As will be 
apparent from FIG. 2, the crimped portion 16 of the vial 10 is longer than 
the diameter of the cylindrical sidewall of the vial. 
There is next provided a capsule 18 as shown in FIG. 3. Capsule 18 is made 
of a substantially non-reactive metal, such as nickel or platinum. It, 
too, is cylindrical but large enough to receive the crimped vial 10 
therein. It has a bottom wall 20 which defines a small, axial gas passage 
22 therethrough. Its upper end 24 is open. Through this upper end, the 
loaded vial 10 is inserted by means of tweezers T. Finally, the upper end 
of the loaded capsule is deformed or "rolled" as shown in FIG. 4 to form 
an encircling shoulder 26 defining an upper opening 28 having too small a 
diameter to permit the crimped vial 10 to pass therethrough. 
The capsule 18, having the loaded vial 10 therein, is loaded into the 
combustion tube of an analyzer instrument in the usual manner, such as, 
for example, as taught in the aforementioned patent. Flushing gas, oxygen, 
and products of combustion are afforded free passage through the length of 
the capsule due to the presence of the gas passage 22 and opening 28. The 
high temperature within the combustion chamber substantially destroys the 
aluminum vial 10 by melting and oxidation but its remains are kept within 
the capsule. The liquid, however, is combusted and its products are swept 
into the analysis portion of the instrument, as is well known to those 
versed in the art. 
The tool which is employed to distort the end of the capsule 18 is 
illustrated in FIGS. 5-12. As may be seen in FIGS. 5 and 6, it comprises a 
substantially horizontal base 30 with a vertically extending column 32 
supporting at its upper end a lever arm 34 by means of a pivot 36. 
Extending outwardly over the base 30 from the column 32 near its upper end 
is a guide 38 which defines a vertical guideway and bearing 40 therein. 
Mounted to, and extending upwardly from, the base 30 is a guide post 42 
axially aligned with the bearing 40 in guide 38. As will be seen in FIG. 
6, the lower end of the guide post 42 extends through a boss 44 in the 
base 30 where it is secured by a nut 46. Guide post 42 is best illustrated 
in FIGS. 8 and 12. As will be seen therein, it includes a turned down 
portion 48, thereby forming upper 50 and lower 52 shoulders. The upper end 
of the post 42 is further reduced to form a pin 54 which, at its uppermost 
end, has a slightly concave surface 56. Post 42 is drilled below the lower 
shoulder 52 to receive a pin 58 which extends diametrically therethrough 
and protrudes on either side of the post 42 as seen in the drawings. 
Surrounding and enclosing the upper end of the post 42 is a substantially 
cylindrical capsule containment member 60. The capsule containment member 
60 is vertically slidable upon the post 42 by means of an axial bore 
having a larger diameter portion 62 which is slidable on the larger 
diameter portions of post 42. An upper, small diameter, portion 64 of the 
bore extends through the upper surface 66 of member 60, where it is 
surrounded by a circular recess 68. 
Extending upwardly from the upper surface 66 on either side of the recess 
68, are a pair of diametrically opposed shoulders 70, 72. The inside 
surfaces of shoulders 70, 72 are curved to form partial cylindrical 
sidewalls extending upwardly from the recess 68. 
Formed in the lower end of the member 60 is a diametrical slot 74 of 
sufficient width to receive the pin 58 therein. Also formed in the bottom 
of the member 60 are a pair of opposed recesses 76, 78, each of which 
extends through a 90.degree. arc on the bottom of member 60 and 
communicates with a different end of the slot 74. The sidewall of the 
member 60 is drilled and tapped to receive a set screw 80 which normally 
extends into the turned down portion 48 of the post 42 to thereby limit 
the vertical movement of the capsule containment member 60. 
Returning now to FIGS. 5 and 6, it will be noted that a link member 82, 
bifurcated at its two ends, is secured by means of a first pivot 84 to 
lever arm 34 and by a second pivot 86 to a vertically depending rod 88 for 
longitudinal movement within the bearing 40 of guide 38. Mounted on the 
lower end of the rod 88 by means of a screw 90 is a capsule forming tool 
92. Tool 92 includes a circumferential flange 94, and a depending 
cylindrical ram 96 positioned to slidably engage the cylindrical inner 
surfaces of shoulders 70, 72 and enter recess 68. The lower, working, 
surface of ram 96 is substantially planar but includes a central recess 98 
of approximately the same diameter as the small diameter bore portion 64 
of member 60. A small air release passage 100 extends upwardly from the 
recess 98. 
Referring back to FIGS. 5 and 6, a compression spring 102 will be seen to 
extend between the guide 38 and the link member 82, thereby tending to 
maintain the lever 34 in its raised position, the upward movement being 
limited by the flange 94 on tool 92. Extending diametrically through ram 
96 and outwardly from opposite sides thereof is a pin 104. 
OPERATION 
The operation of the apparatus of this invention will now be explained with 
particular reference to FIGS. 7-12. 
The capsule containment member 60 is lifted on the post 42 and rotated to 
its raised position shown in FIG. 8, wherein the bottom recesses 76, 78 
rest upon pin 58. In this position, the small diameter bore 64 of the 
containment member 60 extends above the concave surface 56 of pin 54. The 
capsule 18 of FIG. 3 is placed into this bore as shown in FIG. 7 where it 
rests upon concave surface 56 of pin 54. 
Lever arm 34 is then lowered and the ram 96 descends between the shoulders 
70, 72, the ends of pin 104 being positioned intermediate shoulders 70, 
72. The recess 98 engages the upper end of the capsule 18 and crimps it 
inwardly as previously shown in FIG. 4. The lever arm 34 is then released 
and spring 102 retracts ram 96, as shown in FIG. 9. 
In order to release the formed capsule 18, capsule containment member 60 is 
rotated 90.degree. as illustrated in FIG. 10. In this position, the pin 58 
in post 42 is aligned with the ends of slot 74 in member 60. This would 
normally permit the member 60 to return by gravity to the lowered position 
illustrated in FIG. 12. However, the compression of the capsule 18 will 
normally cause it to expand slightly and snugly engage the containment 
member. In order to release the capsule, tool 92 is lowered once again by 
means of the lever arm 34. However, as the containment member has now been 
turned 90.degree., the pin 104 on the tool is now aligned with and engages 
the shoulders 70, 72. This forces the containment member 60 downwardly on 
post 42, as shown in FIG. 12, thereby releasing the capsule 18 which can 
then be removed. 
It is believed that the many advantages of this invention will now be 
apparent to those skilled in the art. It will also be understood that a 
number of variations and modifications may be made therein without 
departing from its spirit and scope. Accordingly, the foregoing 
description is to be construed as illustrative only, rather than limiting. 
This invention is limited only by the scope of the following claims.