WO2012087232A1

WO2012087232A1 - Apparatus and method for thin-film lyophilization

Info

Publication number: WO2012087232A1
Application number: PCT/SE2011/051541
Authority: WO
Inventors: Tobias NORDIN; Panagiotis Ioannidis
Original assignee: Biotage Ab
Priority date: 2010-12-23
Filing date: 2011-12-20
Publication date: 2012-06-28

Abstract

The present invention relates to an apparatus (1) for thin-film freeze-drying of a liquid mixture in a vessel (2), the apparatus (1) comprising a rotation unit (5) being operable to rotate the vessel (2) and a vacuum pump (6) adapted to reduce the pressure within the vessel (2). The apparatus further comprises a sealing unit (7) adapted to seal the opening (3) of the vessel (2) and to connect the vacuum pump (6) to the interior of the vessel (2), a heating unit (8), a sensor assembly (9) and a control unit (10). The apparatus (1 ) also comprises a cooling unit (12) configured to freeze the mixture in dependence on a cooling unit control signal generated by the control unit (10). The invention further relates to a method of thin-film freeze-drying, comprising performing in a single apparatus (1 ), (a) evaporating a mixture in a vessel (2), (b) freezing the mixture in the vessel (2), and (c) freeze-drying compound(s) in the vessel (2).

Description

APPARATUS AND METHOD FOR THIN-FILM LYOPHILIZATION

FIELD OF THE INVENTION

The present invention relates generally to the field of evaporating and lyophilizing of mixtures, and more particularly to an apparatus and a method for evaporation, concentration, freezing and lyophilization of a solution in a single vessel.

BACKGROUND OF THE INVENTION

Mixtures that comprise compounds having a fragile or complex structure, e.g. peptides, which do not easily crystallise, in protic and polar solvents having high boiling point, are not suitable to evaporate and isolate in a conventional way. The remaining compound(s) usually have a texture, which makes them hard to remove from the vessel and thus difficult to handle for further processing. Traditionally, conventional lyophilisation (or freeze-drying) must be applied to such a mixture to make it form a solid powder, which is easier to handle. This process involves solidifying (freezing) the solution in a vessel, applying appropriate vacuum and leaving it in vacuum for several hours. Traditional lyophilization often uses vials where the solution is frozen into a solid mixture at the bottom of the vial and then put into a vacuum chamber with a cold condenser for a long time, usually 8-10 hours for completion of a batch of multiple vials. The frozen solvent then sublimates into gas which leaves the frozen vessel and then condenses in a trap. This leaves the remaining compound(s) as a fluffy, solid powder, completely dried and easy to handle.

The terms evaporation, lyophilization, sublimation and freeze-drying usually have a specific meaning when used. All these terms used in the present application are intended to have the meaning usually given to them in the art.

Lyophilization or freeze-drying occurs when a solvent sublimates, i.e. undergoes a transition directly from solid phase into vapour phase without passing through an intermediate liquid phase. The freeze-drying process thus requires that the solution consists of a solvent that is able to sublimate. Suitable solvents used in traditional freeze-drying include water with a melting point at 0°C, DMSO with a melting point at 18°C and acetic acid with a melting point at 17°C. A mixture which is to be evaporated has often passed through a previous process step, such as a separation by High Performance Liquid Chromatography (HPLC), ion exchange chromatography, FPLC (Fast Protein Liquid Chromatography) or reversed phase chromatography. Evenbefore the separation, the compound(s) of interest have been dissolved in a mixture of water and acetonitrile or methanol. Such a mixture does not freeze and is thus not suitable for lyophilization, and the non-aqueous solvents must therefore be removed before the freezing process can be started. Usually, this is done in aconventional rotary evaporator with a manual judgement of when the volatile solvents have been removed from the sample. The aqueous part of the solution is then frozen, manually transferred into the freeze-dryer and lyophilised. This process often also involves, first, the transfer of the solution to another type of vessel. Depending on the volumes, it normally take several hours to lyophilise a mixture, and the risk of loosing material due to splashing is high, hence the vessel must be manually fitted with a splash cover while sublimation of the mixture proceeds.

An apparatus for the evaporation of solutions is disclosed in the patent application WO2005065799. Herein, said apparatus will be referred to as a conventional evaporator or VI 0 Solvent Evaporator. This conventional evaporator is an apparatus for concentrating solutions in a vaporising receptable having a mouth for the removal of vapour, the apparatus comprising support means for supporting the vaporising receptable with the mouth of the receptable facing upwards, rotation means being operable to rotate the vaporising receptable at high speed about a substantially vertical rotation axis, a vacuum pump to reduce the pressure within the vaporising receptable, and means for sealing the vaporising receptable to the apparatus to maintain the reduced pressure. WO2005065799 further discloses a method for concentrating a solution comprising the steps of dispensing the solution into a vaporising receptable having a mouth for removal of vapour, supporting the vaporising receptable with the mouth facing upwards, rotating the vaporising receptable about a substantially vertical rotational axis, reducing the pressure in the vaporising receptable to evaporate at least a portion of the sample, sealing the mouth of the receptable to the apparatus to connect a vacuum pump to the interior of the vaporising receptable and to maintain the reduced pressure, and maintaining the temperature of the vaporising receptable within a predetermined range.

In a traditional process of evaporating and freeze-drying a solution, a conventional evaporator as disclosed in WO2005065799 is normally used in two intermediate steps of the process, which are separated by other process steps utilising different instruments. In said traditional process, if a large surface area of the solution is wanted, it is created by shell freezing the solution in a conventional evaporator using a bath of dry-ice with alcohol, followed by a transfer to a separate freeze-drying apparatus. A whole batch of sample vials (e.g. around 30 vials) may need to be evaporated and then transferred to another instrument where freeze- drying takes place for the whole batch simultaneously, and evaporation is performed twice in the conventional evaporator due to the need of transferring the solutions to a different instrument and at the same time switching to different vessels.

The patent application WO2004073845 describes a stirred freeze dryer, where freezing and drying are performed in the same vessel. The vessel comprises a rotating mixing member that stirs the product to avoid lumps and which also improves the heat transfer and shortens the freezing and drying processes.

The patent publications US2010107437, US2007186437 and WO2010005021 also disclose different concepts related to freeze-drying processes.

Thus, as described above, the process of evaporation and freeze-drying involves a number of manual steps, which render the process time-consuming and thereby expensive.

SUMMARY OF THE INVENTION

The object of the present invention is to increase the efficiency of a process for evaporation and freeze-drying of liquid mixtures and to overcome the deficiencies of the known methods and apparatuses as described above. The present invention is based on the conventional evaporator as disclosed in WO2005065799 and as briefly described above. However, said apparatus has been further developed by the present inventors, thereby simplifying and speeding up the process of evaporating and freeze-drying of liquid mixtures. According to the present invention, the whole process of evaporation, concentration, freezing and freeze-drying (sublimation) of a solution is conducted by a single apparatus and the sample is kept in a single vessel during the entire process. The process may be performed continuously for one vial at a time, without the need to wait for a whole batch of vials to be evaporated first. Since the freezing and freeze-drying of the mixture may be performed in the same vessel as the evaporation and concentration, only one evaporation step is needed. Significant bottle-necks in the process are thereby avoided. The above-mentioned object is achieved by the present invention according to the independent claims. Preferred embodiments are set forth in the dependent claims.

The present invention relates to an apparatus for thin-film freeze-drying of a liquid mixture in a vessel provided with an opening, the apparatus comprising:

a support unit for supporting the vessel with the opening of the vessel facing upwards;

a rotation unit being operable to rotate the vessel about a substantially vertical rotation axis; a vacuum pump adapted to reduce the pressure within the vessel;

a sealing unit adapted to seal the opening of the vessel and to connect the vacuum pump to the interior of the vessel;

a heating unit configured to heat the vessel;

a sensor assembly adapted to measure parameters related to the sample and to generate sensor signals in dependence thereon;

a control unit adapted to receive and process said sensor signals and to operate the apparatus in accordance with the received signals and operating instructions.

The apparatus further comprises a cooling unit configured to freeze the mixture in dependence on a cooling unit control signal generated by said control unit.

According to an embodiment of the invention, said control unit comprises a timing unit adapted to control the duration of the freezing of the mixture. Said freezing may be controlled by said timing unit to have a duration of a predetermined time period.

According to a preferred embodiment of the invention, said cooling unit comprises a cooling medium and a nozzle for dispensing said cooling medium.

In one embodiment, said sensor assembly comprises a level sensor adapted to detect the liquid level of the mixture in the vessel and to generate a level signal in dependence thereon.

In another embodiment, said sensor assembly comprises a temperature sensor adapted to measure the temperature of the mixture in the vessel and to generate a temperature signal in dependence thereon. In yet another embodiment, said sensor assembly comprises a pressure sensor adapted to measure the pressure level surrounding the mixture in the vessel and to generate a pressure signal in dependence thereon.

In a preferred embodiment, said sensor assembly comprises a level sensor, a temperature sensor and a pressure sensor as described above.

According to one aspect of the invention, the rotation unit is operable to rotate the vessel at a speed at which centrifugal force flattens the mixture against side walls of the vessel.

In a preferred embodiment, said rotation unit is operable to rotate the vessel at speeds of 2000 rpm or higher, such as 3250 rpm or higher, more preferably 6000 rpm or higher, and ideally between 6000 and 10000 rpm.

According to another embodiment of the invention, the heating unit is a hot air blower arranged to direct hot air flow onto the outside of the vessel.

A further aspect of the invention provides a system for producing thin-film freeze-dried compound(s) including a first apparatus according to any embodiment as described above and a second apparatus adapted to perform a precursor process which supplies a liquid mixture, comprising compound(s) to be freeze-dried, to said first apparatus.

The precursor process may be selected from high performance liquid chromatography, purification of organic compounds by ion exchange chromatography, FPLC, reversed phase chromatography, preparative scale supercritical fluid chromatography and synthesis of organic compounds using continuous flow techniques.

A further aspect of the invention relates to a method of thin-film freeze-drying, comprising performing in a single apparatus:

(a) evaporating a mixture in a vessel;

(b) freezing the mixture in said vessel; and

(c) freeze-drying the mixture in said vessel.

In a preferred embodiment, (a) is performed by: (al) dispensing the mixture into a vessel having an opening;

(a2) supporting the vessel with the opening facing upwards;

(a3) rotating the vessel about a substantially vertical rotational axis;

(a4) sealing the opening of the vessel;

(a5) reducing the pressure in the vessel to evaporate at least a portion of the sample; and

(a6) applying heat to the vessel to maintain the temperature of the vessel within a predetermined range.

In another preferred embodiment, (b) is performed by applying a cooling medium to the outside of the vessel during a predetermined time period. Further, (b) preferably comprises rotating the vessel while freezing is performed.

According to yet another preferred embodiment, (c) is performed by reducing the pressure in the vessel to within a predetermined range. Further, (c) preferably comprises rotating the vessel while freeze-drying is performed, and/or (c) may comprise applying heat to the vessel.

According to one aspect of the invention, the vessel is rotated at a speed at which centrifugal force flattens the mixture against side walls of the vessel.

In a further aspect of the invention, the method further comprises measuring parameters related to the sample and generating sensor signals in dependence thereon before freezing of the mixture is initiated.

Preferably, measuring parameters related to the sample is performed by pausing the rotation of the vessel and detecting the liquid level of the mixture in the vessel.

Alternatively or additionally, measuring parameters related to the mixture is performed by measuring the temperature of the mixture and/or by measuring the pressure level in the vessel.

The conventional evaporator software and hardware does not allow for total control over vacuum or spin, and the apparatus is not suitable for freezing or freeze-drying. Consequently, new hardware and new software have been developed in order to provide evaporation and freeze-drying in a single apparatus in accordance with the present invention. Thus, the conventional evaporator has been provided with a cooling unit configured to freeze the mixture in dependence on a cooling unit signal generated by the control unit. Thereby there is no longer any need to transfer the mixture to another vessel and/or another apparatus.

The conventional evaporator has further been provided with an external vacuum pump, thereby rendering the apparatus capable of providing a vacuum level below 1 mbar, such as 0.4 to 0.5 mbar, making it suitable for freeze-drying.

The new software has been implemented in the control unit, thereby rendering the control unit adapted to receive and process sensor signals and to operate the apparatus in accordance with the received signals and operating instructions from the software.

Thereby, the present invention provides an increased efficiency of the process of evaporation and freeze-drying of liquid samples.

The terms "solution", "mixture" and "sample" shall be construed as meaning a mixture comprising at least two components. For the purposes of this invention, such a mixture preferably comprises at least three components, e.g. a volatile organic solvent, which is removed from the mixture by evaporation, a component (e.g. a second solvent), which is frozen and sublimated, and at least one compound of interest, which is freeze-dried and thereby isolated by use of the apparatus and method according to the invention. When used in this application, the terms "solution", "mixture" and "sample" may be used inter-changeably, without departing from the scope of the invention of the present invention, which is defined by the appended claims.

SHORT DESCRIPTION OF THE APPENDED DRAWINGS

Fig. 1 is a schematic view of the apparatus according to the invention.

Fig. 2 is a flow chart depicting the method according to the invention.

Fig. 3 is a flow chart depicting step (a) of the method according to the invention.

Fig. 4 is a flow chart depicting step (b) of the method according to the invention.

Fig. 5 is a flow chart depicting step (c) of the method according to the invention.

Fig. 6 is a flow chart depicting a preferred embodiment of the method according to the invention. DETAILED DESCRIPTION

The present invention will now be described by reference to the appended drawings, followed by examples of using the apparatus and method according to the invention.

With reference to fig. 1, the present invention relates to an apparatus 1 for thin-film fireeze- drying of a liquid mixture in a vessel 2 provided with an opening 3, the apparatus 1 comprising a support unit 4 for supporting the vessel 2 with the opening 3 of the vessel 2 facing upwards;

a rotation unit 5 being operable to rotate the vessel 2 about a substantially vertical rotation axis 13, and a vacuum pump 6 adapted to reduce the pressure within the vessel 2. The apparatus further comprises a sealing unit 7 adapted to seal the opening 3 of the vessel 2 and to connect the vacuum pump 6 to the interior of the vessel 2; a heating unit 8 configured to heat the vessel 2; a sensor assembly 9 adapted to measure parameters related to the mixture and/or to the vessel and to generate sensor signals in dependence thereon, and a control unit 10 adapted to receive and process said sensor signals and to operate the apparatus 1 in accordance with the received signals and operating instructions. In addition, the apparatus 1 comprises a cooling unit 12 configured to freeze the mixture in dependence on a cooling unit control signal generated by said control unit 10.

The apparatus is preferably controlled or operated by a user via an input and output unit 11, which is connected to the control unit 10. The input and output unit may for example include a display and a keyboard, handles and knobs.

The control unit 10 may comprise a timing unit (not shown) adapted to control the duration of the freezing of the mixture. The time of freezing is controlled by the timing unit to have a duration of a predetermined time period. The time period depends mainly on the thickness of the liquid thin-film, but to an extent also depends on the cooling medium used and the method used for freezing the sample. Normally, a mixture having a volume of 1-2 ml after evaporation will take from 10 seconds up to a maximum of 1-2 minutes to freeze.

According to a preferred embodiment of the invention, the cooling unit 12 comprises a cooling medium in a container and a nozzle (not shown) for dispensing the cooling medium in the form of a cooling spray. The cooling spray may for example consist of tetrafluoroethane, dimethyl ether or carbondioxide. and may provide a temperature of approximately -50 °C when being sprayed onto the outside of the vessel 2. As an alternative, the cooling medium may consist of liquid nitrogen having a temperature of -196 °C, which is provided in a container. The liquid nitrogen is pressed out of the container via a tube and out of a nozzle.

In one embodiment, the sensor assembly 9 comprises a level sensor adapted to detect the liquid level of the mixture in the vessel 2 and to generate a level signal in dependence thereon. The level sensor may be a non-contacting optical device. Alternatively, the level sensor may be a contact sensing device employing the known principle of measuring changes in conductivity to detect the surface of the liquid.

In another embodiment, the sensor assembly 9 comprises a temperature sensor adapted to measure the temperature of the sample in the vessel 2 and to generate a temperature signal in dependence thereon. The temperature sensor may be a non-contact temperature sensor or a contact sensing device.

In yet another embodiment, the sensor assembly 9 comprises a pressure sensor adapted to measure the vacuum level in the vessel and to generate a vacuum signal in dependence thereon.

According to one aspect of the invention, the rotation unit 5 is operable to rotate the vessel 2 at a speed at which centrifugal force flattens the mixture against side walls of the vessel 2.

In a preferred embodiment, the rotation unit 5 is operable to rotate the vessel 2 at speeds of 2000 rpm or higher, such as 3250 rpm or higher, more preferably 6000 rpm or higher, and ideally between 6000 and 10000 rpm.

The heating unit 8 may for example be a hot air blower arranged to direct hot air flow onto the outside of the vessel 2. Alternatively, the heating unit may be a light source that emits infrared light/radiation.

In another embodiment, the vessel is removable from the apparatus. Conveniently, the removable vessel 2 is a standard clear glass vial of substantially cylindrical shape. Preferably, the vial has one closed end, the other end having an axially located opening of a diameter smaller than that of the cylinder. For example, the vessel 2 may be a 20 ml scintillation vial. Thus, the apparatus 1 can be used with standard vials, and there is no need to transfer the dried compound(s) from the vessel 2 to a further vessel for transport or storage.

The sensors, the heating unit, the vacuum pump, the rotation unit and other features as described above, may be designed and connected to each other in various manners, and we refer to the above-mentioned patent publication WO2005065799 for further constructional details.

A further aspect of the invention provides a system for producing thin-film freeze-dried compound(s) including an apparatus 1 according to any embodiment as described above and a second apparatus (not shown) adapted to perform a precursor process which supplies a liquid mixture to be freeze-dried to said apparatus 1.

With reference to fig. 2, the present invention further relates to a method of thin-film fireeze- drying, comprising performing in a single apparatus 1 :

(a) evaporating a mixture in a vessel 2;

(b) freezing the mixture in said vessel 2; and

(c) freeze-drying the mixture in said vessel 2.

Fig. 3 depicts a preferred embodiment of the evaporation step (a) of the method, in which (a) is performed by:

(al) dispensing the mixture into a vessel 2 having an opening 3;

(a2) supporting the vessel 2 with the opening 3 facing upwards;

(a3) rotating the vessel 2 about a substantially vertical rotational axis;

(a4) sealing the opening 3 of the vessel 2;

(a5) reducing the pressure in the vessel 2 to evaporate at least a portion of the sample; and (a6) applying heat to the vessel 2 to maintain the temperature of the vessel 2 within a predetermined range. When the liquid transforms into gas, energy is consumed, and therefore it is advantageous to apply heat to the outside of the vessel to maintain and accelerate the vaporization process. At the same time, the heat applied should be moderate in order not to damage the compound(s), and according to the invention, the heating unit applies a temperature of maximum 50 °C.

Fig. 4 illustrates a preferred embodiment of the freezing step (b) of the method, in which (b) is performed by applying a cooling medium to the outside of the vessel 2 during a predetermined time period, and at the same time rotating the vessel 2. In one embodiment, the cooling medium is applied in the form of a cooling spray, which is evenly distributed on the outside of the vessel 2 by use of a nozzle. As an example, when the inventors applied a cooling spray having a temperature of -50 °C, it took approximately 20 seconds to freeze a sample having a volume of 2 ml.

Fig. 5 depicts a preferred embodiment of the freeze-drying step (c) of the method, in which (c) is performed by reducing the pressure in the vessel to within a predetermined range, and at the same time rotating the vessel and applying heat to the vessel. The pressure level will determine how long time it takes before the sample is dry. The lower the pressure, the faster is the freeze-drying step. Preferably, the pressure is reduced to below 1 mbar, more preferably between 0.7 to 0.4 mbar.

According to one aspect of the invention, the vessel is rotated at a speed at which centrifugal force flattens the mixture against side walls of the vessel. Said rotation unit 5 is operable to rotate the vessel 2 at speeds of 2000 rpm or higher, such as 3250 rpm or higher, more preferably 6000 rpm or higher, and ideally between 6000 and 10000 rpm. The same speed may be used to rotate the vessel 2 during evaporation, freezing and freeze-drying of the mixture. The speed chosen should depend on the diameter of the vial; the smaller diameter, the higher speed in order to maintain high centrifugal force. Diameters around 30 mm benefit from 6000 rpm or higher speed. During evaporation and freeze-drying, the vial is rotated in order to avoid so-called bumping or splashing of material, thereby preventing loss of mixture and possible cross-contamination of compound(s). During freezing, the vial is rotated in order to maintain the thin-film created during evaporation, thereby speeding up the freezing of the mixture. With reference to fig. 6, the method of thin-film freeze-drying comprises performing in a single apparatus 1 :

(a) evaporating a mixture in a vessel 2;

(a') measuring parameters related to the mixture and generating sensor signals in dependence thereon before freezing of the mixture is initiated;

(b) freezing the mixture in said vessel 2; and

(c) freeze-drying the mixture in said vessel 2.

Preferably, measuring parameters related to the mixture is performed by pausing the rotation of the vessel and detecting the liquid level of the mixture in the vessel.

Alternatively or additionally, measuring parameters related to the mixture is performed by measuring the temperature of the mixture and/or by measuring the pressure level surrounding the mixture in the vessel.

According to a preferred embodiment, measuring parameters related to the mixture, and generating sensor signals in dependence thereon before freezing of the mixture is initiated, comprises pausing the rotation of the vessel and detecting the liquid level of the mixture in the vessel, measuring the temperature of the mixture and measuring the pressure level

surrounding the mixture in the vessel.

With regard to the method described herein, we further refer to applicable parts of the above- mentioned WO2005065799.

Examples

The conventional evaporator was tested with frozen vials in order to evaluate its possibilities to perform freeze-dry evaporation. Vials were frozen with liquid nitrogen, bottom-frozen as well as thin-film frozen by spinning the vial in liquid nitrogen. Vials were also frozen with standard freeze-spray used for electronic testing and cooling of muscle injuries in sports.

Both water and DMSO were frozen. Two different compounds were tested: l-42-P-amyloid (peptide) and a yellow aromatic halide. Freeze-drying was tested using both a still vial and a spinning vial, respectively. Using the external pump, the vacuum level was below 0.4 mbar and the condenser was at -25 °C or colder. To apply a small amount of heat onto the vial, a fan was started and gently blowing air having a temperature of 36 °C onto the outside of the vial. The vial was then spun to distribute the heat evenly. Spinning the vial seemed to have a positive impact on the result; both from a heat distributing point of view but also that the centrifugal force appears to stabilize the structure of the freeze-dried mixture, keeping the mixture along the inner side of the vial, thereby preventing bumping. Results proved positive and solvent was fully evaporated and the compound(s) had formed a structure that was easy to handle.

Equipment:

Conventional evaporator (VI 0 Solvent Evaporator) system with external vacuum pump and cooling unit

Chemicals:

Liquid Nitrogen

l-42-P-amyloid peptide

Yellow aromatic halide

Example 1

A few mg of the l-42-P-amyloid peptide was dissolved in 2 ml water. Spinning the vial created a thin film of the mixture. Lowering the spinning vial into the liquid nitrogen froze the water within 10-15 seconds. The vial was placed in the instrument and vacuum applied. After the cycle the compound was completely dry and a fluffy thin film created on the inside of the vial thus making it easy to remove and use.

Example 2

Approximately 10 mg of Yellow aromatic halide was dissolved in 3 ml DMSO. Two vials were prepared to compare freeze-drying according to the present invention and conventional evaporation. One of the vials was freeze-dried as a thin film according to the invention and the other vial was evaporated using the conventional VI 0 Solvent Evaporator System. Freeze- dried compound came off as a powder while the evaporated compound crystallized onto the vial and was hard to scrape off. Example 3

Approximately 10 mg of the peptide was dissolved in a HPLC mixture of 4 ml water and 4 ml MeCN (ACN). The sample was first evaporated for about 4 min using 70 mbar vacuum (causing the MeCN to evaporate). Then the thin film was frozen by spraying freeze spray (-50 °C) for 30 sec onto the spinning vial and applying maximum vacuum. The mixture was then run for an additional time (at 1 mbar) completing the lyophilization cycle. The freeze-dried peptide was in the form of a fluffy powder that could be removed with minimum effort simplifying downstream processing.

According to the present invention, the evaporation of volatile solvent is automatically done and sensors detect when only a predetermined amount of water remains, i.e. the sample is concentrated to save time in the freeze-drying stage. High speed rotation is applied during the evaporation step to prevent bumping. The evaporation is then ended and the mixture is automatically and quickly frozen while the vessel is still spinning. The mixture is thus formed into a frozen thin-film with a large surface area. Vacuum is applied while still spinning. Sublimation occurs surprisingly quickly due to the large surface area of the thin-film, a temperature control (by use of a tempered air flow on the outside of the vessel), and the rotationally-created thin-film. The spinning also prevents splashing during sublimation and the result is a porous solid thin film that is ready for further processing. The time needed for the entire process is typically 30-40 minutes for an 8 ml (50% acetonitrile/water) solution. This should be compared to the traditional process, which for a similar sample would take up to several hours. Furthermore, the disclosed method and apparatus make the whole process fully automated.

The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

Claims

1. An apparatus (1) for thin-film freeze-drying of a liquid mixture in a vessel (2) provided with an opening (3), the apparatus (1) comprising:

a support unit (4) for supporting the vessel (2) with the opening (3) of the vessel facing upwards;

a rotation unit (5) being operable to rotate the vessel (2) about a substantially vertical rotation axis (13);

a vacuum pump (6) adapted to reduce the pressure within the vessel (2);

a sealing unit (7) adapted to seal the opening (3) of the vessel (2) and to connect the vacuum pump (6) to the interior of the vessel (2);

a heating unit (8) configured to heat the vessel (2);

a sensor assembly (9) adapted to measure parameters related to the sample and to generate sensor signals in dependence thereon;

a control unit (10) adapted to receive and process said sensor signals and to operate the apparatus (1) in accordance with the received signals and operating instructions;

characterised in that said apparatus (1) further comprises a cooling unit (12) configured to freeze the mixture in dependence on a cooling unit control signal generated by said control unit (10).

2. The apparatus (1) according to claim 1 wherein said control unit (10) comprises a timing unit adapted to control the duration of the freezing of the mixture.

3. The apparatus (1) according to claim 2 wherein said freezing is controlled by said timing unit to have a duration of a predetermined time period.

4. The apparatus (1) according to claim 3, wherein said predetermined time period has a duration in the range of 10-120 seconds.

5. The apparatus (1) according to any preceding claim wherein said cooling unit (12) comprises a cooling medium and a nozzle for dispensing said cooling medium.

6. The apparatus (1) according to any preceding claim wherein said sensor assembly (9) comprises a level sensor adapted to detect the liquid level of the mixture in the vessel (2) and to generate a level signal in dependence thereon.

7. The apparatus (1) according to any preceding claim wherein said sensor assembly (9) comprises a temperature sensor adapted to measure the temperature of the sample in the vessel (2) and to generate a temperature signal in dependence thereon.

8. The apparatus (1) according to any preceding claim wherein said sensor assembly (9) comprises a pressure sensor adapted to measure the pressure level in the vessel (2) and to generate a pressure signal in dependence thereon.

9. The apparatus (1) according to any preceding claim wherein the rotation unit is operable to rotate the vessel at a speed at which centrifugal force flattens the mixture against side walls of the vessel.

10. The apparatus according to claim 9 wherein the rotation unit (5) is operable to rotate the vessel (2) at speeds of 2000 rpm or higher, such as 3250 rpm or higher, preferably between 6000 and 10000 rpm.

11. The apparatus (1) according to any preceding claim wherein the heating unit (8) is a hot air blower arranged to direct hot air flow onto the outside of the vessel (2).

12. A system (1) for producing thin-film freeze-dried compound(s) including the apparatus (1) according to any preceding claim and a second apparatus adapted to perform a precursor process which supplies a liquid mixture to be freeze-dried to said apparatus (1), wherein said precursor process is selected from high performance liquid chromatography, purification of organic compounds by ion exchange chromatography, FPLC, reversed phase

chromatography, preparative scale supercritical fluid chromatography and synthesis of organic compounds using continuous flow techniques.

13. A method of thin-film freeze-drying, comprising performing in a single apparatus (1):

(a) evaporating a mixture in a vessel (2);

(b) freezing the mixture in said vessel (2); and (c) freeze-drying the mixture in said vessel (2).

14. The method according to claim 13 wherein (a) is performed by:

(al) dispensing the mixture into a vessel (2) having an opening (3);

(a2) supporting the vessel (2) with the opening (3) facing upwards;

(a3) rotating the vessel (2) about a substantially vertical rotational axis;

(a4) sealing the opening (3) of the vessel (2);

(a5) reducing the pressure in the vessel (2) to evaporate at least a portion of the mixture; and (a6) applying heat to the vessel (2) to maintain the temperature of the vessel (2) within a predetermined range.

15. The method according to claim 13 or 14 wherein (b) is performed by applying a cooling medium to the outside of the vessel (2) during a predetermined time period.

16. The method according to claim 15, wherein the predetermined time period has a duration in the range of 10-120 seconds.

17. The method according to claim 15 wherein (b) further comprises rotating the vessel (2) while freezing is performed.

18. The method according to any of claims 13-17 wherein (c) is performed by reducing the pressure in the vessel (2) to within a predetermined range.

19. The method according to claim 18 wherein (c) further comprises rotating the vessel (2) while freeze-drying is performed.

20. The method according to claim 18 or 19 wherein (c) further comprises applying heat to the vessel (2).

21. The method according to any of claims 14, 17 or 19 wherein the vessel (2) is rotated at a speed at which centrifugal force flattens the mixture against side walls of the vessel (2).

22. The method according to any of claims 13-21 further comprising measuring parameters related to the mixture and generating sensor signals in dependence thereon before freezing of the mixture is initiated.

23. The method according to claim 22 wherein measuring parameters related to the mixture is performed by pausing the rotation of the vessel (2) and detecting the liquid level of the mixture in the vessel (2).

24. The method according to claim 22 or 23 wherein measuring parameters related to the mixture is performed by measuring the temperature of the mixture.

25. The method according to any of claims 22-24 wherein measuring parameters related to the mixture is performed by measuring the pressure level in the vessel (2).

26. Method according to any of claims 13-25, wherein a precursor process is performed prior to (a) and wherein the precursor process is selected from high performance liquid

chromatography, purification of organic compounds by ion exchange chromatography, FPLC, reversed phase chromatography preparative scale supercritical fluid chromatography and synthesis of organic compounds using continuous flow techniques.