METHODS FOR MEASURING PRESSURE IN FREEZE DRYING SYSTEMS

Abstract

An improved method for determining pressure in a lyophilisation system containing a lyophilisation chamber and a condenser chamber wherein a freeze drying operation is being performed is provided for. The improved method uses a temperature measuring device such as a thermocouple or a temperature resistance device to measure temperature and from this measurement the pressure of the components in the lyophilisation chamber can be calculated using a predetermined relationship between temperature and pressure.

Claims

1. An improved method for determining pressure in a lyophilisation system wherein a freeze drying operation is being performed, the improvement comprising measuring temperature in the lyophilisation system and calculating pressure of the lyophilisation system therefrom using a predetermined relationship between temperature and pressure.

2. The method as claimed in claim 1 wherein the lyophilisation system comprises a lyophilisation chamber and a condenser chamber.

3. The method as claimed in claim 1 wherein the temperature is measured with a device selected from the group consisting of a thermocouple and a resistance temperature device.

4. The method as claimed in claim 1 wherein the pressure is calculated from the temperature according to the formula:

5. The method as claimed in claim 1 wherein water, nitrogen and air are present in the lyophilisation system.

6. The method as claimed in claim 2 wherein the condenser chamber contains a condenser coil.

7. The method as claimed in claim 2 wherein the condenser chamber is in fluid communication with a vacuum pump.

8. An improved freeze drying method in a lyophilisation system, the improvement comprising measuring temperature in the lyophilisation system and calculating pressure of the lyophilisation system therefrom.

9. The method as claimed in claim 8 wherein the lyophilisation system comprises a lyophilisation chamber and a condenser chamber.

10. The method as claimed in claim 8 wherein the temperature is measured with a device selected from the group consisting of a thermocouple and a resistance temperature device.

11. The method as claimed in claim 8 wherein the pressure is calculated from the temperature according to the formula:

12. The method as claimed in claim 8 wherein water, nitrogen and air are present in the lyophilisation system.

13. The method as claimed in claim 9 wherein the condenser chamber contains a condenser coil.

14. The method as claimed in claim 9 wherein the condenser chamber is in fluid communication with a vacuum pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The FIGURE is a schematic of a lyophilisation system showing the relationship between the lyophilisation chamber and the condenser chamber.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The FIGURE shows a schematic of a lyophilisation system where a lyophilisation chamber 1 is connected via a conduit 5 to a condenser chamber. The lyophilisation chamber 1 is where the freeze drying operation is performed. The lyophilisation chamber 1 will contain the shelves and the vials to be processed. Typically the lyophilisation chamber 1 will be a sterile environment.

[0026] The freeze drying operation will be performed at temperatures as low as 100 C. The pressure of the chamber is also reduced to below 0.01 mBar absolute. After the contents of the vials are frozen, the sublimation step occurs in the lyophilisation chamber 1. The water ice in the vials is converted into vapor in part due to the low pressure in the lyophilisation chamber 1. This low pressure is provided by the condenser chamber 2 operation whereby condenser coil 3 and a vacuum pump 4 operate to provide the vacuum to the lyophilisation chamber 1. The water vapor sublimating from the vials will condense on the condenser coil 3 and become frozen to its surface.

[0027] The temperature of the condenser chamber 2 will be measured by an instrument 6 which is typically a thermocouple or a resistance temperature device (RTD). Since there is a correlation between temperature and vapor pressure of compounds, the use of the instrument 6 will assist in determining the pressure of the gases present in the lyophilisation system.

[0028] While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of the invention will be obvious to those skilled in the art. The appended claims in this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the invention.