EP1154826A1

EP1154826A1 - End piece for monolithic chromatography columns

Info

Publication number: EP1154826A1
Application number: EP00906225A
Authority: EP
Inventors: Günter Hauke; Günther Sättler; Dieter Lubda; Edith Dicks; Willi Neuroth; Karin Cabrera; Alexander Kraus
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 1999-02-09
Filing date: 2000-01-26
Publication date: 2001-11-21
Also published as: WO2000047304A1; JP2002536651A; DE19905117A1

Abstract

The invention relates to encased monolithic sorbents on the basis of porous moulded parts. The lateral area of said monolithic sorbent is encased in a liquid-tight manner by a pressure-proof casing made, for example, of a plastic material and a filter unit is integrated into the casing for low dead-volume, centered sample introduction. According to the invention the filter unit is pressed on to the monolithic sorbent by a snug-fitting, moulded end piece. The invention also relates to the integration of a precolumn, the use of the monolithic sorbent provided for by the invention in a chromatography column and the use of such a monolithic sorbent for the chromatographic separation of at least two substances.

Description

End piece for monolithic chromatography columns

The invention relates to mounting devices for monolithic sorbents.

For the production of conventional chromatography columns with particulate

Sorbents are filled in a stainless steel or plastic tube with precisely fitting ends. It is achieved that the sorbent bed lies tightly against the shell of the column and the particles are homogeneously distributed over the entire cross section of the column. For this reason, an ideal sample application should be carried out with columns filled with particulate sorbents over the entire cross-section of the column. If, as is disclosed in WO 94/19 687 and WO 95/03 256, particulate is replaced by monolithic sorbents, the problem arises of sealing the jacket of the sorbent in a liquid-tight and pressure-stable manner. This is the only way to ensure that the sample and eluent are transported exclusively through the sorbent.

Various options for the liquid-tight sheathing of monolithic sorbents are disclosed in DE 197 26164. This includes, for example, a casing with pressure-stable plastics such as PEEK (polyether ether ketone). The jacketed monolithic sorbents disclosed in DE 197 26164 are flush with the jacket. The ends are sealed with a flat filter unit for sealing. When using monolithic sorbents coated in this way, it was found that the separation performance and, in particular, peak symmetry appear to be in need of improvement.

The object is therefore to improve the columns with monolithic sorbents known from DE 197 26164 with regard to separation performance and peak symmetry. The improvement is achieved by redesigning the end regions of the casing of the monolithic sorbents in accordance with the present invention.

The invention relates to a separating device comprising a monolithic sorbent based on porous shaped bodies and a liquid-tight casing, a recess for the insertion of a sealing filter element in the end regions into the casing being incorporated in the end regions.

A preferred embodiment of the separating device according to the invention is a sheathing consisting of a composite material made of PEEK and glass or carbon fibers.

The invention further relates to an invention

Separating device, whereby a guard column with filter units is integrated into the column construction on both sides via an intermediate piece.

A preferred embodiment is a separating device according to the invention, the ends of the separating device being provided with end pieces for sealing and supplying liquid.

The invention furthermore relates to the use of the coated monolithic sorbents for the chromatographic separation of at least two substances.

Figure 1 shows the upper end region of a monolithic sorbent coated according to the invention. Figure 2 shows a corresponding construction with an integrated guard column. Figure 3 shows a further embodiment of a sorbent coated according to the invention.

The lower end region of the coated monolithic sorbents is preferably in each case designed to correspond to the upper one.

Figure 4 shows chromatograms of separations performed on a column before and after stress tests.

Monolithic sorbents are generally known from the literature; These include, above all, porous ceramic shaped bodies, as are disclosed in WO 94/19 687 and in WO 95/03 256. The term monolithic sorbents also encompasses molded articles made of polymers, as described by F. Svec and J.M. Frechet (1992) Anal. Chem. 64, pages 820-822, and by S. Hjerten et al. (1989) J.

Chromatogr. 473, pages 273-275. Monolithic sorbents based on porous shaped bodies which have interconnected macropores and mesopores in the walls of the macropores are particularly preferred, the diameter of the macropores having a median value greater than 100 nm and the diameter of the mesopores having a median value of 2 and 100 nm.

Monolithic sorbents therefore consist of materials as are used for particulate sorbents. In many cases (eg Si0 ₂ ) these sorbents can easily be used for chromatographic separations. However, the base supports are derivatized more frequently in order to improve the separation properties; additional groups are introduced, which are grouped under the name separation effectors. Separation effectors and methods for their introduction into the base support are known in principle to the person skilled in the art and can be found, for example, in DE 197 26164 and the literature cited therein.

According to the invention, the term monolithic sorbent is understood to mean both a porous base body and a porous base body derivatized with separation effectors.

To coat monolithic sorbents, as described in WO 94/19 687, materials such as Teflon, PTFE or FEP can first be shrunk on as a thin tube and then with a pressure-resistant coating in a tube with synthetic resin, e.g. cast in an epoxy or polyimine resin, or sintered in with a plastic. An additional covering with a composite material with a reinforcement made of glass or carbon fibers is also suitable for pressing the inner covering tightly against the monolithic sorbent.

Due to the great pressure stability of the materials reinforced with glass or carbon fibers, in particular PEEK, these materials can also be used for direct sheathing of the monolithic sorbents. In addition, such materials can contain other additives, such as inorganic oxides.

This type of direct sheathing with glass or carbon fiber reinforced composite materials shows particular stability even at high pressure during a chromatographic separation. These advantages can also be transferred to columns and jackets of other geometries, as are disclosed, for example, in DE 197 26164.

Another possibility of producing monolithic sorbents coated in this way is to apply the plastic onto the ceramic rod. extrude. The ceramic rod is fed through a crosshead parallel to the extrusion of a hose. The freshly extruded tube encloses (hot) the ceramic rod and is additionally pressed onto the ceramic rod, for example by a pressing device. It is also possible to heat a preformed hose instead of one

Produce tubing by extrusion. This mechanical pressing and the additional sintering during cooling result in a tight jacket. It is also possible to insert the ceramic rod into a prefabricated tube, the inside diameter of which is slightly larger than the outside diameter of the ceramic rod, and then the

To heat plastic so that the hose can be pulled off to the final diameter and thereby tightly encloses the ceramic rod.

In a further variant, the plastic jacket is produced by flame spraying or single or multiple shrinking.

Working methods and parameters are familiar to the person skilled in plastics processing or can be optimized using customary methods.

In principle, it is also possible to use the latter variants of the casing after a previous first casing with e.g. a shrink tube or similar non-pressure-stable material.

To use the pressure-resistant coated monolithic sorbent as a chromatography column, the column must be provided with end pieces for connecting eluent inlets and outlets. In addition, there should be the option of installing filter units and guard columns. In the case of monolithic chromatography columns, a filter element on the two end pieces of the column is theoretically not necessary. However, it is still preferred to protect the column head from mechanical To protect destruction. The filter element also serves as a filtration medium for the eluent.

The quality of a chromatographic column is determined by the separation performance and peak symmetry.

The separation performance of a chromatography column results from the number

N of theoretical floors per meter column (N / m).

The symmetry value Q is ideally Q = 1.

In the case of tailing, the symmetry values shift into the range Q> 0, in the case of fronting to Q <0.

Figure 1 shows a monolithic sorbent coated with the filter insert according to the invention; the top half is shown. The monolithic sorbent (1) is encased in a liquid-tight manner by the plastic jacket (2). The sheathing (2) consisting of a polymer, preferably PEEK, does not end flush with the monolithic sorbent, but extends beyond the monolithic sorbent, whereby a recess can be created. The protrusion is between approximately 1 mm and, depending on the diameter of the monolithic sorbent, up to approximately 1 cm and above. The recess can preferably be produced by milling out the monolithic sorbent or other methods of material removal known to the person skilled in the art. In addition to milling out the monolithic sorbent, the cutout can preferably be enlarged by removing material on the inside of the casing. In the same way, the cutouts according to the invention can be formed by the temporary installation of shaping elements during the sheathing. A filter element (3) is inserted sealingly into the recess. The filter element (3) typically consists of a filter (3a) and a sealing insert (3b) The filter, which is directly on the monolithic

Sorbent is preferably made of metal or other common Materials. The sealing insert is preferably made of Teflon or PFA (perfluoroalkoxy copolymer) and can be inserted into the recess with a precise fit. In one possible embodiment, it narrows conically towards the filter (Figure 1); another embodiment is shown in Figure 3. According to the invention, the sealing filter element (3) can also consist (not shown in the figure) of a porous plastic material which has both filtering and sealing properties, so that the filter element does not consist of a filter and sealing insert, but only of a workpiece. The sealing filter element is pressed onto the monolithic sorbent by adding an appropriately shaped end piece (5) and enables an effective seal. The end piece (5) is shaped in such a way that it fits snugly into the filter unit and the eluent inlet (7) hits the center of the filter. The end pieces according to the invention consist of polymers or preferably of metal. They are glued on, shrunk on, fixed using a cartridge holder, or preferably screwed on using an external thread with a screw cap (6).

Figure 2 shows a separation device according to the invention with an integrated guard column.

The sealing filter unit (3) with filter (3a) and teflon seal (3b) is fitted into the casing (2) of the monolithic sorbent (1). According to the invention, the sealing filter unit can also be made in one piece from a material that has both filtering and sealing properties (not shown in the figure). On the sealing

An intermediate piece (8) made of metal or plastic, preferably PEEK, with a central eluent inlet (9) is placed on the filter element. This is shaped in accordance with the end piece (5) such that it can be inserted into the filter device with a low dead volume. The guard column consists of the sorbent (10), which is surrounded by a jacket (11) in which the filter units (12) according to the invention are integrated on both sides. This turns the guard column into a separation column towards the intermediate piece pressed and fixed to the opposite side by an end piece (5) according to the invention. The end piece (5) is preferably pressed against the plastic jacket (2) and the filter unit (12) by a screw cap (13) adapted to the dimensions of the guard column.

Figure 3 shows another possible embodiment of the separation device according to the invention. Monolithic sorbent (1), casing (2) and screw cap (6) are designed according to the separating device shown in Figure 1. The filter element (3) consisting of a filter (3a) and a sealing insert (3b), on the other hand, has another embodiment. The sealing insert (3b) is cylindrical. Accordingly, the end piece (5) is cylindrical, so that it can be inserted with a precise fit in the sealing element. Due to the cylindrical design of the sealing element and the end piece, the radial pressure is applied to the when the end piece is inserted

Jacket (2) reduced. This embodiment is particularly suitable for less stable sheathing, for example made of PEEK. In the case of mechanically more stable materials, such as fiber-reinforced PEEK, both the embodiment shown in FIG. 1 with a conical sealing element and the embodiment shown in FIG. 3 can be used. The embodiment shown in Figure 1 is particularly suitable for metal sheaths.

According to the sealing element and end piece shown in Figure 3, guard columns with a cylindrical shape can also be used

Sealing elements can be integrated into the separating devices according to the invention.

The dimensions of the components of the invention mentioned, such as the length or diameter of the columns, correspond to those which are customary for similar constructions in the field of particulate sorbents. Even without further explanations, it is assumed that a person skilled in the art can use the above description in the broadest scope. The preferred embodiments and examples are therefore only to be regarded as descriptive, in no way as in any way limiting in any way.

The full disclosure of all applications, patents, and publications listed above and below are incorporated by reference into this application.

Examples

In both examples were for the invention

Separators tapered sealing elements used.

example 1

Comparison of monolithic chromatography columns with regard to separation performance (N / m) and peak symmetry (Q).

In each case 11 columns with a monolithic sorbent with a length of 10 cm and a diameter of 4.6 mm were compared. According to the state of the art as disclosed in DE 197 26164, the columns of group A do not have an incorporated filter element, but are flush with the casing. The columns of group B contain a filter element which is worked into a recess according to the invention. Conditions: eluent acetonitrile / water 60/40 (v / v) flow 2 ml / min

Detection UV 254 nm room temperature feed substance anthracene

Group B

N / m Q

9624 1.39

10566 1.21

10440 1.50

94240 1.37

110800 1.26

110000 1.37

114800 1.24

85960 1.20

80550 1.08

95340 1.06

101 140 1.44

99920 1.28

0 = average value

The comparison of the values of groups A and B shows a strong improvement in the symmetry values and a significantly better separation performance when using the separation device according to the invention. Example 2

Representation of separation performance and pressure stability of chromatography columns with glass fiber reinforced PEEK sheathing

A monolithic column with a length of 10 cm and a diameter of 4.6 mm was encased with glass fiber reinforced PEEK and tested in a reversed phase (RP) system with regard to its separating performance after continuous exposure to high pressure. The column was first used under normal RP conditions, then loaded with methanol / water 40/60 (v / v) with a flow of 7 ml / min for 18 h at 22 ° C. in a long-term test. The corresponding back pressure was 215 bar. It was then chromatographed again under normal RP conditions.

RP conditions:

Eluent acetonitrile / water 60/40 (v / v)

Flow 2 ml / min detection UV 254 nm

Room temperature feed substance anthracene (last peak)

The chromatograms of the two separations are shown in Figure 4. Chromatogram a) shows a separation before the stress test, chromatogram b) a separation after the permanent stress. Chromatographic values for anthracene:

The same values for peak symmetry and separation performance are obtained before and after the stress test. This shows a great mechanical stability of the casing. Would be by the high

Mechanical instability occurred under pressure, channels would have formed between the monolithic sorbent and the casing.

This channel formation manifests itself in a reduction in the symmetry values, since in addition to the tailing that occurs before the load

Fronting would be generated. This observation is not made when using glass fiber reinforced sheathing.

Claims

Expectations

1. Separating device comprising a monolithic sorbent (1) based on porous moldings, a liquid-tight casing (2) and a sealingly inserted filter element (3), characterized in that at least one end region is designed such that the monolithic sorbent (1) is shorter than the casing (2) and thus forms a cavity into which the filter element (3) is inserted in a sealing manner.

2. Separating device according to claim 1, characterized in that the liquid-tight jacket consists of a composite material made of PEEK and glass or carbon fibers.

3. Separating device according to claim 1 or 2, wherein in addition a guard column (10, 11) with filter units (12) is integrated on both sides via an intermediate piece (8).

4. Separating device according to claims 1-3, wherein the ends of the separating device with end pieces (5) for sealing and

Hydration are provided.

5. Use of a coated monolithic sorbent according to claims 1-4 in a chromatographic column.

6. Use of a coated monolithic sorbent according to claims 1-4 in the chromatographic separation of at least two substances.