Freeze drying involves the removal of water or other solvents from a given product by a process called sublimation. This occurs when the ice of a frozen product converts directly to the gaseous state without passing through the liquid phase. This enables the preparation of a stable product that is easy to use and store at ambient temperatures.
The Essential 3 Stages of Freeze Drying:
1. Pre-Freezing – The sample is pre-frozen in preparation for the sublimation process.
2. Primary Drying – The start of the sublimation process – main drying.
3. Secondary Drying – The removal of all residual water from the sample.
How to Calculate the Size of the Freeze Dryer:
In order to choose the correct size of freeze dryer several questions have to be addressed:
• What condenser size (volume) is required?
• What condenser temperature is required?
• What is the maximum number of samples to be freeze dried at one time?
• What is the total volume of the samples?
• What is the size of the container/tray you want to use for the samples?
• What is the sample volume in each tube/vial?
If “bulk drying” on trays or shallow containers, the sample depth should ideally be less than 1.5 cm.
When all these questions have been answered the size and configuration of the freeze dryer can then be determined.
What Condenser Temperature is Needed?
The choice of condenser temperature is important. If the temperature is too high, then a correct freeze drying process cannot take place. In the table below are the freezing points/ collapsing temperatures of some commonly used solvents and known products. These are given for guidance purposes and to assist in deciding the condenser temperature for your application.
Collapsing temperatures of different products and temperatures:
-Apple Juice -42°C
-Citrate Buffer -40°C
-Coffee Extract -20°C
-Dextran -9°C
-Fruktose -48°C
-Gelatin -8°C
-Glucose -40°C
-Inisitol -27°C
-Lactose -32°C
-Lemon Juice -36°C
-Methocel -9°C
-MSG -50°C
-Orange Juice -24°C
-Ovalbumim -10°C
-Phosphate Buffer -8°C
-PVP -23°C
-Sorbitol -45°C
-Sucrose -32°C
-Solutions containing ethanol etc. -60°C to -110°C
-Trichlorethylene -86.4°C
Configuring the freeze dryer for your application:
Step 1 – Condenser Temperature and Chamber Volume:
I. Choose between -55°C, -95°C, -100°C and -110°C condenser temperatures.
II. Condenser volume options: 4L, 9L, 15L, 80L
| | -55°C | -95°C | -100°C | -110°C |
| 4 litre | x | | | x |
| 9 litre | x | | x | |
| 15 litre | x | x | | |
| 80 litre | x | x | | |
Step 2 – Chamber & Manifold Options:
I. 300 & 500mm diameter Acrylic chambers
II. Heated or Unheated shelves
III. 250 – 440mm stainless steel tray options.
IV. Manifolds with rubber valves for flask attachments
V. Micro-titre plate racks
VI. Stainless steel manifold with 12 x rubber valves
VII. Stoppering device – for sealing vials under vacuum?
VIII. Ampoule manifold with 16 connections
We offer a wide selection of chambers with electrical heated shelves that ensure uniform and faster drying, especially in the secondary drying stage. Giving increased recovery rates with controlled programmable energy input.
Step 3 – Freeze Dryer System Options:
I. Basic, Pro and Touch Model Options
II. Vacuum control and pressure regulation for primary drying
III. Digital readout of process parameters
IV. Touch screen diplay
V. Manual or fully automated operation
VI. Pre-freezing option
VII. Electrical de-icing
VIII. Vacuum release valve
IX. Teflon coated condensers for aggressive acids
For more information on this range of products please see the brochures provided:
If you would like to discuss your freeze drying application please contact our technical sales department who will be happy to discuss your process along with system options: sales@scientific-labs.com.