Industry extensively uses chromatography to separate complex substances into their constituent parts. This technique is mainly used as an analytical tool but there is a need for high resolution purification at a process or manufacturing scale. Most chromatography processes use a solid stationary support which can detrimentally retain some of the constituents while others are carried forward with a mobile solvent phase. Countercurrent chromatography (CCC) is a form of liquid-liquid chromatography with no solid support, having the advantage of 100% sample recovery. Furthermore, liquid/solid chromatography is difficult and expensive to scale up to process plant and the principle of purification rarely stays the same, whereas CCC can be linearly scaled from analytical to process plant without any change in the principle of purification.

In CCC, a sample undergoes successive mixing and settling steps between two immiscible solvents, one stationary and the other mobile. These mixing and settling steps occur within a continuous length of tubing wound around a cylinder, which is rotated in planetary motion (Figure 1). Planetary motion causes a non-uniform acceleration field to act on the coil of tubing. A high centripetal acceleration field is generated at the distal part of the coil and a low one at the proximal point (Figure 2). Furthermore, this reciprocating acceleration field can subject a sample, injected with the mobile phase, to as many as 60,000 mixing and settling steps an hour as it passes along the length of tubing.

The very properties that make CCC work also produce dynamic forces that cause the coils of tubing to unwind. To avoid this problem, tubing has traditionally been wound on cylinders and rotated in a direction to have the effect of tightening the coils onto the cylinder. Research has shown the best chromatographic way to rotate a coil is in the same direction in which it is wound. This has the effect of unwinding the coils of tubing away from the cylinder.

Research has also shown that CCC efficiency (productivity) can be increased, using high flow rates, by maintaining stationary phase retention through running at high rotational

speeds. However, this has two effects: the higher flows significantly increase operating pressures beyond the limits of currently used (PTFE) tubing and high rotational speeds greatly increase the cyclical acceleration forces on the tubing. (A doubling of speed increases the forces fourfold.) The present invention seeks to provide improved chromatography apparatus.

According to an aspect of the present invention, there is provided chromatography apparatus including at least one cylinder, at least one carrier for providing rotation of the cylinder or cylinders, the or at least one cylinder being provided with a groove therein and at least one tube wound around the cylinder or cylinders and located substantially in the groove.

Advantageously, the cylinder or cylinders are provided with a plurality of grooves for accommodating a plurality of tubes.

The or each groove is preferably of a size closely related to the outside diameter of the tube accommodated therein.

The grooves may have any pitch, constant or variable and can follow any desired path, although may usually be substantially helical.

Advantageously, the tubing is substantially encapsulated, preferably in an adhesive resin.

Additionally or alternatively, there may be provided a sleeve over the cylinder and tubing assembly. These features can provide mechanical strength to the tubing and can provide external support for the tubing and resin.

In the preferred embodiment, the or at least one of the cylinders can act as the sleeve.

More specifically, there may be provided a plurality of cylinders of different diameters which can slide within one another, each cylinder being provided with at least one groove, a tube being located in the groove of the innermost cylinder and extending to the adjacent

outer cylinder in a continuous path. For this purpose, there is preferably provided an end slot in one or more of the cylinders for the passage of a tube from one cylinder to the other.

According to another aspect of the present invention, there is provided a method of providing a coil of tubing on a cylinder of chromatography apparatus including the steps of providing at least one cylinder, providing a groove in the or at least one cylinder, and winding at least one tube in the or at least one groove.

Advantageously, the cylinder or cylinders are provided with a plurality of grooves and a plurality of tubes are wound in the grooves.

Advantageously, the method includes the step of substantially encapsulating the tubing, preferably with an adhesive resin. Additionally or alternatively, there may be provided a sleeve over the cylinder and tubing assembly.

In the preferred embodiment, the method provides a plurality of cylinders of different diameters which can slide within one another, each cylinder being provided with at least one groove, a tube being located in the groove of the innermost cylinder and being extended to the adjacent outer cylinder in a continuous path.

The preferred embodiments can provide tubing which is stable under rapidly changing accelerations. Moreover, it is possible to permit a multitude of stable coil configurations using a variety of tubing material.

For process coils there will be a requirement to maximise throughput while maintaining stationary phase retention. The described preferred construction method provides the ability to increase the helix angle (creating higher Archimedean forces for better stationary phase retention) and, if desired, manifold multi-start coils to maintain capacity and reduce back pressure.

A bonus of this arrangement is that it is possible to wind a small bore analytical coil in parallel with the large bore tubing of a process coil.

An embodiment of the present invention is described below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram showing the geometry of planetary motion of a cylinder of a planetary carrier of chromatography apparatus; Figure 2 shows a section of tubing in coiled and unwound form to depict the non-uniform acceleration fields and mixing and settling zones in a coil of tubing rotated in planetary motion; and Figure 3 in a cross-sectional view of a chromatography cylinder having thereon a coil of tubing wound in a helical groove around the cylinder according to a preferred embodiment.

The following describes a method of winding any type of tubing in a predetermined pitch on any number of layers. A further important feature of this process is that, once wound, the tubing may be further restrained and protected, for example by encapsulating it within an adhesive resin. The resulting coil can withstand the high pressures and dramatic mechanical stresses associated with a CCC machine.

The prime elements of this assembly are the tubing 10 itself and a cylinder 12, or number of concentric cylinders, on which it is wound. These cylinders feature a groove 14 that conforms closely to the outside dimensions of the tubing 10 and holds the coiled tubing in its desired configuration. If a plurality of cylinders is used they fit closely over each other and are mechanically prevented from relative rotation.

An important feature of the grooves 14 is that they can have any pitch, constant, variable or indeed follow any desired path, limited only by the ability of the tube to deform during winding. Additionally, a cylinder 12 may have more than one groove, similar to a multi- start thread.

Lastly, to enhance the mechanical strength of the coil and stabilise the tubing 10 an adhesive resin (not shown) may be provided to encapsulate the tubing. The complete assembly is retained within an outer sleeve (not shown), to provide external support for the outer coil of tubing 10 and create an enclosure for the resin.

An example of a type of coil formed from a single continuous length of tubing wound over five concentric cylinders with an outer sleeve fitted and with the tubing encapsulated with a resin, can be formed as follows: 1. The tubing 10 is pre-formed to fit in the beginning of the groove 14 of the first cylinder 12.

2. The tubing 10 is wound into the helical groove 14 along the cylinder's length (Figure 3).

3. The next cylinder is fitted over and secured to the first.

4. The tubing 10 is then wound using the same rotation, but fed in the opposite direction to the previous layer. In this example the tubing 10 is lifted up onto the next cylinder, via the end slot 16 provided.

5. Steps 3 & 4 are then repeated for the next three layers.

6. The tubing 10 is then formed so it exits where required, in this example along the axis and opposite to where it enters the first cylinder.

7. The outer sleeve (not shown) is then fitted and secured to the outer, fifth cylinder.

8. The tubing 10 is then encapsulated, via the cylinder's end slots, with an adhesive resin.