United States Patent 3585862

A device for introducing liquid samples into a liquid chromatographic column which includes provision for alternatively utilizing a series of cartridges into which samples have been previously deposited or a sample valving arrangement of a conventional type having a capillary loop by which samples may be introduced "on the spot." This is accomplished by providing an alternative passage member or fitting substituted in place of the cartridge providing connections for the capillary loop samples.

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International Classes:
G01N30/20; G01N30/24; (IPC1-7): G01H1/00
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Primary Examiner:
Swisher, Clement S.
I claim

1. In a device for introducing samples into a chromotographic column of the type having an inlet conduit means and outlet conduit means spaced-apart from each other, means for moving a plurality of casings containing samples to be analyzed sequentially into and out of the space between said inlet and outlet conduit means, thereby allowing eluent fluid to pass from said inlet conduit means through said sample casings to wash at least a portion of the sample into said outlet conduit means which is connected with a chromotographic column, the improvement comprising:

2. The apparatus according to claim 1 wherein said inlet and outlet means include means for selectively clamping said casings and said passage member between said inlet means and outlet means, and including valve means for selectively conducting fluid under pressure alternately to said inlet means and said capillary means.

3. The apparatus according to claim 2 wherein said passage member and said casings are removably received in openings in a movable disc, said passage member being substantially interchangeable with said casings in said disc openings.

The invention relates to a device for introducing samples into a chromatographic column.

A device is known for introducing samples automatically or semiautomatically into a chromatographic column from one or several containers holding in a capillary the sample to be analyzed and sectionalized into adjacent liquidal columns for example by one or several bubble pistons. In a known embodiment of such device the individual sample containers are successively connected by valve means into a hydraulic circuit leading to the chromatographic column either directly or through a pump. This type of apparatus is described in U.S. Patent No. 3,401,564.

Another device is known for introducing samples into a chromatographic column successively from more than one cartridge in which the individual samples are bonded for example by sorption on a small quantity of a porous possibly loose material such as an ion exchanger used as a separating charge of the chromatographic column. The samples are placed beforehand into a number of cartridge-shaped casings which are clamped for example between two porous plates. Samples held in this manner in the cartridge-shaped container may be practically kept for any time in a wet or dry condition. For transferring the samples from any such casing into the chromatographic column the casing is tightly supported between a pressure head and a frame body provided with a capillary duct leading to the chromatographic column. The pressure head is provided with another duct connected to a pump which forces an eluent to flow therethrough and through the casing into the column. The eluent carries along with it the sample held by sorption on the charge of the casing and introduces it into the chromatographic column. Desorption is achieved by suitable physical-chemical properties of the eluent. As the dimensions of the individual casings are small, a number of casings containing samples intended for progressive analyses can be prearranged on a suitable conveyor. The individual cartridges are replaced from their operating position in the following manner: a cartridge containing a just analyzed sample is released from any connection by lifting the pressure head, then the conveyor means lifts to a certain extent all cartridges placed on it and frees them from any contact, and in this lifted condition the conveyor means is moved, that is shifted or rotated to bring the next nearest cartridge into the abandoned operating position between the pressure head and the duct leading to the chromatographic column. The conveyor means is then lower and a new cartridge is brought into the operating position thus securing close hydraulic communication between the central duct in the pressure head and the cartridge, and also a close communication between the lower end of the cartridge and a continuing capillary duct leading to the chromatographic column. This type of sample introducing device is described in U.S. Pat. No. 3,487,678 and No. 3,527,101. A substantial disadvantage of this method resides in the fact that it is difficult to transfer the sample located between two or more small bubble pistons from the cartridge to the chromatographic column. In majority of cases a considerable amount of irregular bubbles is produced which do not uniformly separate the sample form adjacent parts of the liquidal column.

All these methods and devices are inconvenient from the point of view of achieving the lowest possible depreciation of the concentration gradient when transferring the sample into the chromatographic column. The substantially reduce the separating efficiency of the liquidal column due to the fact that an unsuitable quantity of air enters the loose charge of the liquidal column and becomes the cause of an irregular flow of the eluent, thus disturbing one of the main conditions for securing the most steep concentration gradient.

It is substantially possible to achieve the most steep concentration gradient when transferring a sample from a dosing device into a chromatographic column by placing the sample between two or more small bubbles while being transported to such column. No difficulties arise from the use of even a longer or wider pipe through which the sample is led. Bubble pistons prove to be a very effective means for preventing undesirable mixing between the individual sections of the liquidal column moving through its capillary. The bubbles may be so small that no difficulties arise from the presence of a very small quantity of gas which they introduce into the column, more particularly in cases where the eluent and the sample both pass through a closure with a porous body. Here the bubbles become fragmented and the resulting very small parts do not interfere any longer becoming quickly dissolved in the adjacent liquid. This exceptionally advantageous method of transferring a sample into column cannot be used, for practical purposes, in a method where the sample is caught beforehand in the loose charge of the cartridge and led therefrom into the column by the stream of the liquid. The sample containing cartridges are placed here in larger number in conveyor means performing either a linear or a rotational movement.

Laboratory practice makes usually two different demands on analyzers of for example, amino acids:

In current analyses a certain degree of depreciation is tolerated which is caused by transposing the samples in the above-described manner, that is from loose charges of the individual cartridges to the chromatographic column. Such type of analysis has the advantage of readily permitting automation.

The second required demand made on the analyses is to achieve maximum separation efficiency of the analyzer even in semiautomatic cycles.

It is a general object of the invention to avoid the said and other disadvantages of the known devices.

According to my invention at least one cartridgelike casing holding samples intended for treatment is replaced by a passage member at a place where the sample is transferred into the chromatographic column, the capillary outlet of the passage member being tightly connected to the capillary duct leading to the column. This permits the alternative use of the two previously mentioned sampling systems in a single device.

The invention will be best understood from the following specification when read with the accompanying drawing in which

FIGS. 1 and 2 illustrate substantially in sectional views two embodiments, respectively, of a device in accordance with the invention, and

The same reference numerals indicate the same or equivalent elements in both figures.

According to FIG. 1 a plurality of known exchangeable cartridgelike casings 1 is located in a transportation means such as shiftable disc 2' each casing 1 provided with a duct 1' holding a sample. One casing 1 is replaced by a passage member 2 outwardly shaped substantial identical with the casing 1. The passage member 2 is shown in a position where the sample can be transferred from a capillary duct 15 therein into the column 20 the pressure head 3 and the sealing rings 25, 25' securing the receiver 2 in a hydraulic circuit leading to the column 20. A pump 4 forces eluent through pipe 5, duct 6, the cranked duct 9 in rotary valve 8 thin the frame body 7 and through the adjoining pipe 10 into the three-way valve 11. This valve 11 in the position shown in FIG. 1 permits the eluent to flow through pipe 12 over a known adjustable loop dosing device 13 into pipe 14 and into L-shaped duct 15 in passage member 2. The pressure of adjusting screw 3' upon pressure head 3 secures in view of pressure rings 25, 25' a tight connection between duct 15 and duct 16 from where the eluent flows through the adjustable duct 17 of valve 8 into the supply duct 19 leading to column 20.

In the illustrated position of the three-way valve 11 the pipe 21 leading to the cranked duct 22 in the pressure head 3 is disconnected from pump 4. In normal analyses the sample is transferred from the above-mentioned individual cartridges 1 which are progressively placed into the shown operative position above duct 16 and is carried by the stream of the eluent flowing through duct 22 and cartridge 1 over the ducts 16, 17 and 19 to column 20; for this effect the three-way valve 11 is turned in clockwise direction through 90° causing a hydraulic connection between pump 4 and pipe 21 disconnecting however pipe 12 and the loop dosing device 13.

In the alternative case when the three-way valve 11 is in the position illustrated in FIG. 1 the eluent flows through the described and shown paths to column 20. While the sample is transferred the loop 23 of the dosing device containing a sample between two or several bubbles is connected into the circuit between pipes 12 and 14. The loop-dosing device 13 is brought into the dosing position in which the loop is part of the hydraulic circuit between pipes 12 and 14 by manually semiautomatically or automatically rotating an outer rotating member for example a lever 24 as indicated by the arrow appended thereto. A clockwise rotation of valve 8 approximately through 60° produces a direct hydraulic connection between ducts 6 and 19 by means of duct 9 as shown in dotted lines, the other ducts being disconnected from the pump 4. This permits replacement at any time individual cartridges 1 of passage member 2 without interrupting the analysis just being carried out in column 20 and without necessitating varying the transflux when the individual cartridges or passage member 2 are being exchanged, or even if the entire transportation disc 2' is being removed.

FIG. 2 illustrates schematically another embodiment of the device in accordance with my invention. Passage member 2 which replaces an individual casing 1 in carrier 2' is provided with two angular ducts 15 and 18, separated from each other. Duct 15 is equivalent with the identically numbered duct of FIG. 1, the only difference being that it may lead into pipe 14 with a smaller angular bend which is advantageous for the transfer of bubble pistons. The second angular duct 18 opens with one leg into the top face of passage member 2 and is tightly joined by a sealing ring 25 to duct 22 in the pressure body 3. This duct 22 is directly connected to eluent pump 4 by the pipe 21. The eluent from duct 22 flows into duct 18 and through pipe 12 to the loop dosing device 13; therefrom the eluent flows through pipe 14 into duct 15, passage member 2, and further on to duct 16 in the frame body 7 tightly joined by sealing ring 25'. In this embodiment frame body 7 does not comprise hydraulic switching means such as valve 8, the duct 16 being directly connected to column 20. The sample is here transferred from the loop 23 of the dosing device to the column 20 in the same manner as in the embodiment of FIG. 1.

The advantage of the embodiment illustrated in FIG. 2 resides in the elimination of the three-way valve 11. The loop dosing device 13 together with the passage member 2 connected thereto may permit to carry out individual analyses with increased separation power by replacing passage member 2 in carrier 2' by a normal cartridge 1.

A conventional cartridge-type machine has a movable disc 2' which is typically in the form of a turntable that supports a plurality of casings 1 containing samples to be analyzed. The casings 1 move sequentially between the movable clamp 3 and the socket in the base 7 of the machine. The passage 16 conducts liquid from the casing to the column 20. Fluid is conducted from the pump 4 through the conduit 21 and through the clamp 3 from which it flows through the interior passage in the casing 1 to transfer the sample into the column. The apparatus of this invention permits the conventional turntable apparatus to be converted for use with a loop dosing device. The passage member 2 has the same shape as the conventional casing 1 so that it is received in one of the openings in the disc 2' . It also has the same length so that it is securely clamped by the member 3 when aligned with the passage 16. The capillary 23 receives a sample to be tested by operation of the dosing device 13. In accordance with conventional practice, the sample is separated by air bubbles, which are shown in dotted lines in the tube 23. The apparatus and technique for introducing the samples into the capillary 23 and for controlling flow into and out of the capillary are well known in the art. The valve 11 controls flow of fluid from the pump 4, and may be a conventional manual valve. Fluid under pressure flows through the conduit 12 to the dosing device 13, or through the conduit 21 to the clamping head 3. If the valve is in the position shown in FIG. 1, samples are introduced into the column from the capillary 23 and when the valve is rotated clockwise 90°, fluid under pressure is introduced into the casing 1 to wash the sample into the column in accordance with conventional techniques.

It is also possible to achieve these effects by placing passage member 2 into its operative position indicated in FIG. 2 after removing the whole carrier 2' . In this case passage member 2 may have a shape different from that of the individual cartridges 1 permitting a more convenient stabilization.