Method And Device For Introducing Samples Into A Chromatographic Column

Abstract

A method and apparatus for carrying out liquid chromatography. A plurality of cartridges are transported sequentially into fluid communication with the column. Each cartridge contains a solid porous sorption material retained between perforated plates. Immediately before moving into the location where the cartridge is in communication with the column, the cartridge is clamped in a fluid circuit and deaeration of the sorption material is carried out by pumping a liquid through the cartridge. After deaeration of the porous material, eluent liquid is pumped through the cartridge and into the column and the danger of the inclusion of air bubbles in the stream is eliminated.

Description

My invention relates to a method for introducing samples into chromatographic columns and it also relates to a device for carrying out said method.

In one known method and device the samples to be analyzed, for example mixtures of amino acids, are introduced before being analyzed into individual cartridges wherein they are held by sorption on a small amount of an ion exchanger gripped between two porous plates. This method has the disadvantage that the samples to be analyzed are bonded to the ion exchanger mostly in dried form, particularly if the samples are introduced into the respective cartridges as early as for example one month prior to the analysis. A relatively large amount of air is contained either in microscopic holes between ion exchanger grains or other microscopic spaces in the cartridge and when the liquid eluent flows through the cartridge, the air is entrained in the liquid stream which flows into the chromatographic column. This is not too harmful in analytical processes of medium effectivity in which one analysis may last about two hours. But in highly effective modern methods this disadvantage becomes damaging substantially reducing the total efficiency of the method and device.

It is a general object of my invention to eliminate the air bubbles from the eluent stream.

In accordance with the invention each of the cartridges, the contents of which are to be treated in an analytical process, is freed of an undesirable quantity of air before being put into a position in which the sample is transposed from the cartridge into the chromatographic column. To free the cartridge of air it is introduced into a hydraulic circuit close to the place at which the sample is to be transposed from the cartridge into the chromatographic column. In this position a suitable liquid is pumped through it either permanently or temporarily. This liquid fills up all spaces which heretofor have been occupied by air or by a gas.

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

FIG. 1 illustrates substantially in section an embodiment of my new device;

FIG. 2 shows a sectional view of a detail of FIG. 1;

FIG. 3 is a partial top view of a transportation disc for the cartridges; and

FIG. 4 is a schematic view of one modified form of the pump and conduit apparatus of FIG. 1; and

FIG. 5 is a schematic view of another modified form of the pump and conduit apparatus of FIG. 1.

In the following specification the reference numerals 1 and 2 used for the cartridges also indicate their working positions later referred to; otherwise all reference numerals in all figures identify the same or equivalent elements.

The cartridges 1, 2 are transposed stepwise by a carrier 3 such as a transportation disc which turns step-by-step in the direction of arrow 4 and which also liftably frees cartridges 1, 2 from the positions shown in FIG. 1 where they are clamped between the pressure bodies 10 and 18 and the discharge channels 13 and 19', respectively. Each of the cartridges 1, 2 is provided with a longitudinally extending central boring which contains a certain amount of for example a cation exchange resin 5 held between plates 6 and 7 made from a porous material.

In this position cartridge 1 by means of sealing rings 11, 12 is tightly clamped between the spring-loaded pressure body 10 actuated by pressure element 9 and the mouth of channel 13 leading the eluent into column 8 through channel 24 in the rotary valve member 14. Another channel 25 in said valve member 14 connects pipe 15 with duct 15' and guides the elution solution from pump 14' through conduits 16,17 into the cartridge 1 from where said solution continues through ducts 13 and 24 into column 8.

Prior to transposing a cartridge from position 2 into position 1 and to the performance of the analysis the cartridge 2 is clamped similar to cartridge 1 between the pressure body 18 and the mouth of duct 19' and liquid of proper qualities is pumped from container 23 by pump 22 through conduits 21, 20 into and through cartridge 2 into conduits 19',19 leading into waste. Thereby any gaseous content is removed from cartridge 2 before it is moved into position 1 and before analysis is performed. During such deaeration the liquid fed by pump 22 need not be accurately dosed and pump 22 may be of any proper type such as a peristaltic pump because the hydraulic resistances of cartridges 1, 2 or of their porous charge 5 and of the porous plates 6, 7 are very small.

It is important that the sample bonded by sorption or otherwise to the carrier material in the cartridge is not carried away from the cartridge even to a small extent. This can be achieved by filling the cartridges with a small quantity for example of the same cation exchange resin with which the columns are also filled. The liquid used for expelling air or gas forms for example a citrate or another buffer which is substantially identical with elution buffers intended not only to carry the sample into the column but also to perform chromatography in the column. One difference is that the pH value is so low that no untolerable quantity of the sample will be carried away into waste when the liquid flows through the cartridge, and the entire quantity of the sample remains bonded to the material in the cartridge.

FIG. 2 illustrates the rotary valve member 14 turned approximately by 60.degree. clockwise to directly connect the pipe 15 through the channel 25 in the rotary valve member 14 with column 8; the eluent is thus fed directly into the column 8 and the cartridges 1, 2 can be freely manipulated as they are not introduced into the hydraulic circuit between pump 14' and column 8.

FIG. 3 shows a conventional transportation disc 3 supporting a plurality of cartridges 1, 2 arranged in two concentric placements. This arrangement is advantageous for automatic introduction of samples into more than one column.

In accordance with conventional practice, the disc 3 rotates at predetermined time intervals to advance the cartridges from one position to the next. Thus, the cartridges are unclamped by raising the clamping heads 10 and 18, while raising the disc 3 to engage the collar at the upper end of each cartridge 1 and 2. In this manner, the cartridges are disengaged from the conduits 17 and 13; and the conduits 21 and 19' and are free to move from the position indicated at 2 in FIG. 1 to the position indicated at 1 in FIG. 1. The cartridge previously in the position indicated 1 advances toward the right, as viewed in FIG. 1 and as indicated by the arrow 4. The cartridges are thus transported step by step into and out of engagement with the clamping heads 10 and 18. When the cartridges 1 and 2 are in the position shown in FIG. 1, the pump 22 draws liquid from the container 23 for deaeration.

During deaeration the cartridge in position 2 is being completely filled with liquid by pump 22 from container 23. Excess liquid passes out of the cartridge 2 through the conduit 19' to waste. After release of the cartridge from this position 2 and during its transposition into position 1, that is approximately for one or two seconds, no liquid flows therethrough because of the hydraulic resistances of the cartridge charge 5 and of the porous plates 6, 7.

The valve 14 is in the position shown in FIG. 2 while the cartridge is being transported from one position to the other. The pump 14' operates continuously and the eluent liquid flows through the conduit 15 and through the valve passage 25 to the column 8. When the cartridge is clamped in position, as shown in FIG. 1, the valve 14 is rotated to the position shown in FIG. 1 to conduct eluent through the passage 17, through the cartridge containing the sample, and into the column 8. The valve 14 is then returned to the position shown in FIG. 1 to stop the flow of eluent liquid to the cartridge, thereby allowing the cartridge to be transported by the disc 3. The deaerating step that is performed at FIG. 2 and the elution step that is performed at position 1 occur substantially simultaneously.

It would not be harmful if an air bubble would form under the pressure body 10 when the cartridge is again gripped in position 1. At a low rate of flow this air bubble would not be carried down by the stream and any sudden change in the flow would be entirely negligible; the danger of transposition of many small bubbles from the cartridge into the column is completely eliminated even in the form of foam. In very effective chromatographic processes for example lasting less than one hour a transposition of a larger amount of gas into the column would be a factor which considerably reduces the separating power of the column.

FIG. 4 shows a modified form of the pump and apparatus at the pump and conduit apparatus of FIG. 1. The liquid container 23a supplies liquid to the pump 22a and a valve 24a selectively controls flow through the conduit 21a which corresponds to the conduit 21 in FIG. 1, or with the waste conduit 19a, corresponding to the waste conduit 19 in FIG. 1. Similarly, FIG. 5 discloses a pump 22b for supplying liquid from a container 23b to the conduit 21b or 19b, as controlled by the operation of the valves 26 and 27.

Claims

I claim:

1. A method for introducing liquid samples into a chromatrographic column in the absence of air bubbles comprising: adsorbing a quantity of a sample liquid on a porous material within a cartridge, connecting said cartridge in a first fluid circuit, pumping a first liquid stream through said cartridge, subsequently disconnecting said cartridge from said first circuit and connecting said cartridge with a second fluid circuit, and pumping a second liquid stream through said cartridge and into said column, whereby said first liquid stream deaerates said cartridge.

2. The method according to claim 1 wherein said porous material is substantially identical with porous material contained in said column, said sample is substantially insoluble in said first liquid, whereby the first liquid deaerates the cartridge without disturbing the bond between the sample and said porous material.

3. A method for introducing liquid samples into a chromatographic column in the absence of air bubbles comprising: adsorbing a quantity of a sample liquid on a porous material within a cartridge, supporting a plurality of said cartridges for sequential movement through a first position and through a second position, pumping a first liquid stream through said cartridge at said first position, and subsequently pumping a second liquid stream through said cartridge at said second position and into said column, whereby said first liquid stream deaerates said cartridge.

4. The method according to claim 3 wherein said material in said cartridge is substantially identical with material contained in said column, and said first liquid is substantially identical with said second liquid.

5. Apparatus for introducing samples into a chromatographic column comprising: a plurality of cartridges, means mounting said cartridges for sequential movement between a deaerating position and a sample introduction porition, first means for pumping liquid through said cartridge while in said deaerating position to displace air from the interior of said cartridge, and second means for pumping eluent liquid through said cartridge while in said sample introduction position, said eluent pumping means including a conduit communicating between said cartridge and said chromatographic column while said cartridge is in said sample introducing position.

6. The apparatus according to claim 5 wherein said first liquid pumping means and said eluent pumping means are operable simultaneously for deaerating one of said cartridges while a preceding cartridge in said sample introducing position is receiving elution liquid and a sample is being carried from said preceding cartridge into said column.

7. The apparatus according to claim 5 including means for clamping said cartridges in said deaerating position and in said sample introduction position, said clamping means including fluid passages in fluid circuits with said first and second pumping means, respectively and sealing means between said clamping means and said cartridge, whereby said cartridges are effectively transported from one position to the other and connected in the respective fluid pumping circuits.