FR2618348A1 - Improved apparatus for liquid phase chromatography - Google Patents

Abstract

Improved apparatus for liquid phase chromatography, of the kind comprising a cartridge which encloses a charge of adsorbent material in pulverulent form, which is housed in a tubular column and through which passes a solvent into which the mixture to be analysed or prepared has been injected. This apparatus is characterised in that its cartridge 9 of adsorbent material 10 is freely immersed in a tubular column 1 filled with a liquid under pressure 8, that this cartridge 9 receives the mixture to be analysed or prepared at a pressure close to that of the said liquid 8, at one of its ends 11 and from outside the column 1, and that it is closed at its other end by a plunger 12 through which an outlet conduit 16 passes, connecting the downstream part of the cartridge 9 to the outside of the column 1. Application to liquid phase chromatography.

Description

 The present invention relates to an improved apparatus for liquid chromatography, of the type comprising a cartridge which contains a charge of adsorbent material in powder form, which is housed in a tubular column, and which is traversed by a solvent into which has been injected the mixture to be analyzed or prepared.

 Such a cartridge is described in French patent application No. 86.15724 of November 13, 1986, and, according to the latter, its outside diameter is substantially equal to the inside diameter of the column, while the charge of adsorbent material in powder or suspension therein. is enclosed between two porous disc-shaped plates, one of which can be actuated by a jack in order to compress the load.

 This device produces excellent results, but, nevertheless, it still has some drawbacks, among which it should be mentioned that the compression of the load of adsorbent material takes place only in the axial direction and that it is necessary to give very large dimensions. specific to the various components of the device.

 Also, the purpose of the present invention is to provide a liquid chromatography apparatus which overcomes the various drawbacks mentioned above, and, in particular, which provides three-dimensional compression of the adsorbent load, its cartridge also admitting larger dimensional tolerances and lower mechanical strength.

 Another object of the invention is to provide a device which is less expensive and simpler, but also reliable, than those belonging to the prior art.

 According to the invention, these aims, and others which will appear subsequently, are achieved thanks to a liquid chromatography apparatus of the kind specified above which is characterized by the fact that its cartridge of adsorbent material is freely submerged in a tubular column filled with a liquid under pressure, that this cartridge receives the mixture to be analyzed or to be prepared under a pressure greater than or equal to that of the liquid in question, at one of its ends and from outside the column, and that it is closed at its other end by a piston crossed by an outlet pipe which connects the downstream part of the cartridge to the outside of the column.

 In this regard, it should be noted immediately that the expression "freely submerged" used above means that the cartridge of adsorbent material has an outside diameter significantly smaller than the inside diameter of the column, so that it can "float" in the latter. Of course, it is nevertheless possible to provide, if need be, some form of material securing between the cartridge and the column which contains it, of which a practical example will be described later.

 However, if we call P and p, respectively, the pressure of the mixture to be analyzed or to be prepared at the inlet and the outlet of the cartridge of the apparatus, the pressure difference (P - p) is equal at the pressure drop Pc in the cartridge in question, and this value is relatively large, since the outlet of the cartridge is generally vented. As the pressure of the fluid contained in the column, outside the cartridge, is in all points substantially equal to P, it is clear that the piston closing the cartridge on the outlet side of the mixture to be analyzed or to be prepared is subjected at a differential pressure equal to (P - p), or even at the pressure drop Pc, which can reach approximately 100 bars.

 It can therefore be seen that, thanks to the arrangements according to the present invention, the piston is moved automatically towards the inside of the cartridge without the need to call on an external jack. In addition, the compression produced here is triaxial, and it is exerted both in the radial direction.

 It should be noted here that, since the cartridge of the device according to the invention floats in a fluid under a pressure close to that of the liquid which it contains, it is not necessary to give it dimensions very precise. On the other hand, and for the same reason, its walls can be made of a thinner material than previously and its mechanical production is simpler.

Finally, the cartridge of the apparatus according to the invention can be embedded in any chromatography column of any diameter, if this diameter is greater than that of the cartridge, without it being necessary to provide cartridges of diameter substantially equal to inside diameter of the column
As has been said above, the pressure of the fluid outside the cartridge is substantially equal to the inlet pressure of the mixture to be analyzed or to be prepared, which, it should be remembered, was previously injected in an appropriate solvent, In fact , it is sufficient, for obvious reasons, that this external pressure is higher than the value (r - p) by a value sufficient for the piston of the cartridge to be subjected to a suitable differential pressure.

 According to an advantageous embodiment of the apparatus according to the present invention, the pressure of the fluid external to the cartridge is strictly equal to the pressure of supply of the mixture since this external fluid consists of part of the solvent under pressure in which the mixture is injected, this part being taken upstream or downstream of the injection of the mixture to be analyzed or to be prepared. This avoids using an external fluid source, which significantly simplifies installation and reduces the cost.

 In the first case, and the fact that, conventionally, a solvent circuit connects the apparatus to a solvent tank via a pump and a device for injecting the mixture to be analyzed or 9 To prepare, it suffices to lead into the column, outside the cartridge, a branch connected to the solvent circuit between its pump and its injection device.

 In the other case, the part of the column located outside the cartridge is in direct communication with the supply of mixture to be analyzed or to be prepared, so that it is the solvent before being added with this. mixture which serves as external fluid.

 Preferably, this direct communication is achieved thanks to the fact that a sintered plug is fixed by welding between the head of the cartridge and the underside of the column cover, and that the supply of solvent arrives at the top of this plug to flow, on the one hand, towards the space formed between the column and the cartridge, and, on the other hand, towards the interior of the latter.

 According to one of its embodiments, the column according to the present invention contains several cartridges of the kind specified above connected in series by pipes.

In this case, the phenomenon explained above for a single cartridge is reproduced in the same way for the following ones, the piston of which is obviously subjected to a differential pressure equal to the pressure drop from the entry into the first cartridge.

 In all cases, and so that the pistons of the cartridge or cartridges can move freely in the axial direction, it is necessary that at least some of the tubes present are deformable, for example by making them of a flexible plastic material and by giving the shape of a serpentine or an S.

The description which follows, and which has no limiting character, will make it possible to understand clearly how the present invention can be put into practice. It should be read against the accompanying drawings, among which:
- Figure 1 shows a schematic axial sectional view of an apparatus according to the invention comprising two chromatography cartridges; and
- The f-igure 2 shows, also in schematic axial section view, the head of such an apparatus according to another embodiment.

 In what follows, it will be assumed that the liquid chromatography apparatus according to the invention is in the vertical position of use, as shown in the figures, which gives all their meaning to expressions such as "superior" or " below".

That said, and as can be seen in FIG. 1, this device comprises a column l closed at its upper part by a cover 2 which is held in place by a fixing shown diagrammatically at 3 and which is crossed axially by a mixture inlet 4 to analyze or prepare injected beforehand in a solvent under pressure. This inlet 4 is supplied from a solvent tank not shown by means of a pipe 5 comprising a pump 6 followed downstream of a mixture injection device 7
Column 1 contains a pressurized liquid 8 in which one or more cartridges are embedded, two of which, 9 and 9 ′, have been shown in FIG. 1, their identical members being designated by the same reference, but with an apostrophe for those of the lower cartridge 9 '.

 The cartridges 9 and 9 ′ are filled with a powdery adsorbent material 10, solid or in suspension, which is confined between a fixed head 11 and a lower piston 12.

These members are respectively crossed by an inlet 13 and by an outlet 14 for the mixture to be analyzed or to be prepared.

 The inlet 4 of this mixture is connected by a tube 15 to the inlet 13 of the upper cartridge 9, and the outlet 14 of the latter is connected to the head 11 'of the lower cartridge 9' by a tube 16. Finally , the outlet 14 'of this cartridge 9' is. connected by a tube 17 to the outlet 18 of the device.

Preferably, the pipes 15, 16 and 17 are made of a flexible plastic material, and. they have the shape of a coil or an "S", which allows the free movement of the pistons 12 and 12 '
However, one, or even two, could be replaced by a fixed tube. As for the walls of the cartridges 9 and 9 ', they can be made of thin sheet metal.

 Finally, a bypass 19 is connected to the pipe 5 for supplying pressurized solvent between the pump 6 and the device 7 for injecting the mixture to be analyzed or to be prepared. It emerges in column 1, outside the cartridges. 9 and 9 'and, as has been said above, it follows that the pressurized fluid 8 of column 1 consists of the pure pressurized solvent into which the mixture to be analyzed or prepared is then injected at 7 .

 In the enlarged partial view of FIG. 2, we find the column 1 and its cover 2 with its fasteners 3, as well as its inlet 4 of mixture to be analyzed or to be prepared, and it contains the pressurized fluid 8 in which the cartridge 9 filled with adsorbent material 10.

 In this embodiment, the head 11 of this cartridge 9 is in two parts 11a and 11b which are assembled with the interposition of an O-ring 20, and it ends towards the inside of the cartridge by a porous plate 21 which serves to standardize in the radial direction the distribution of the mixture to be analyzed or to be prepared; it is provided on its periphery with an O-ring seal 22.

The outer part 11a of the head 11 is fixed to the underside of the cover 2 of the column 1 by means of a porous plug 23 of sintered material which is welded, at its upper part, to the cover 2 and, at its lower part, on the head 11. The inlet 4 of mixture to be analyzed or prepared opens at its base in the porous plug 23, so that the mixture flows, on the one hand, into column 1 , outside the cartridge 9 <arrows
F), and, on the other hand, in the latter by a channel 24 which passes through its head 11. As a result, as has been said above, the fluid 8 contained in column 9 consists of the solvent which comes from the pump 6 through the line 5 and into which has already been injected at 7 the mixture to be analyzed or to be prepared. Of course, the solvent bypass 19 of FIG. 1 is useless in this case, and it has been eliminated .

 Without departing from the scope of the present invention, it would be possible to make various modifications to the embodiments which have just been described. Thus, for example, the tubing 17 (see FIG. 1) which leaves the base of the floating cartridge 9 or of all the floating cartridges mounted in series, 9 and 9 ′, could leave column 1, no longer by its bottom as shown in 18 in Figure 1, but by its cover 2. Of course, this variant can be applied both in the ace of the embodiment shown in Figure 1 and in that of the form Figure 2.

 Finally, the liquid 8 contained in column 1 which bathes the floating cartridge or cartridges could be different from the solvent intended for the mixture to be analyzed or to be prepared.

Claims (7)

- CLAIMS 1. Improved apparatus for liquid chromatography, of the type comprising a cartridge which contains a charge of adsorbent material in powder form, which is housed in a tubular column, and which is traversed by a solvent into which the mixture has been injected. analyze or prepare, characterized in that its cartridge (9) of adsorbent material (10) is freely immersed in a tubular column (l) filled with a pressurized liquid (8>), that this cartridge (9) receives the mixture to be analyzed or to be prepared under a pressure greater than or equal to that of said liquid (8), at one of its ends (ll) and from outside the column (l), and that it is closed at its other end by a piston (12) crossed by an outlet pipe (16) which - connects the downstream part of the cartridge (9) outside the column (1). 2. Apparatus according to claim 1, characterized in that said pressurized fluid <8) consists of part of the pressurized solvent into which said mixture to be analyzed or to be injected, this part being taken upstream or downstream injection of the mixture to be analyzed or prepared. 3. Apparatus according to claim 2, characterized in that a solvent circuit <5) connects its inlet (4) to a solvent tank via a pump <6) and a device (7 ) for the injection of said mixture to be analyzed or to be prepared, and that a bypass (l9) connected to said conduit <5) opens into said column (l), outside of said cartridge (5). 4. Apparatus according to claim 2, characterized in that the interior of said column (l) is in direct communication with the supply (4) of mixture to be analyzed or to be prepared 5. Apparatus according to claim 4, characterized in that the communication between the interior of said column (l) and said inlet (4> of mixing takes place by means of a plug <23) made of sintered material which is welded, on the one hand, to the head of said cartridge <5), and on the other hand, to the underside of the cover (2) of the column (l), said solvent arriving at the top of this plug (23 > to flow, on the one hand, towards the space formed between the #wall of the column (1) and the cartridge (5), and, on the other hand, towards the inside of this cartridge (5) .  6. Apparatus according to any one of claims 1 to 5, characterized in that said column <1> contains several cartridges (5, 5 ') connected in series by pipes (15, 16, 17). 7. Apparatus according to claim 6, characterized in that at least one of said tubes (15, 16, 17) is made of a flexible plastic material and has the shape of a coil, an "S" or of a loop.