Chapter 5: Using Your Freeze Dryer
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35
Original instructions
Vapor pressure above ice
Temp.
(°C)
Pressure
(mbar)
Temp.
(°C)
Pressure
(mbar)
Temp.
(°C)
Pressure
(mbar)
Temp.
(°C)
Pressure
(mbar)
Temp.
(°C)
Pressure
(mbar)
0
6.11
-11
2.37
-21
0.94
-31
0.34
-50
0.039
-1
5.63
-12
2.17
-22
0.85
-32
0.31
-60
0.011
-2
5.18
-13
1.98
-23
0.77
-33
0.28
-70
0.003
-3
4.76
-14
1.81
-24
0.70
-34
0.25
-80
0.001
-4
4.37
-15
1.65
-25
0.63
-35
0.22
-5
4.02
-16
1.50
-26
0.57
-36
0.20
-6
3.69
-17
1.37
-27
0.52
-37
0.18
-7
3.38
-18
1.25
-28
0.47
-38
0.16
-8
3.10
-19
1.13
-29
0.42
-39
0.14
-9
2.84
-20
1.03
-30
0.38
-40
0.13
Adjustments to the vacuum level must be made for various freeze drying
conditions. Factors that must be considered are whether the sample is freeze dried
on heated shelves or in glassware attached to sample valves, the volatility of the
sample itself, the size of the sample and the heat energy supplied to the sample.
When the vacuum control is set to operate at less vacuum (higher pressure), the ice
holding capacity of the collector may be decreased. Some guidelines for setting
the vacuum level are shown below. Exact protocols must be determined by the
user for the specific samples that are being freeze dried.
Material
Solidification/Eutectic
Temperature
Pre-Freeze
Temperatures
Vacuum Set Point
Bacteria, Virus
≤ -40°C
≤ -50°C
≤ 0.04 mbar
Milk
-5 to -13
-15 to -23
1.65 to 0.77
Fungi
≤ -40
≤ -50
≤ 0.04
Vegetable Tissue
-25 to -50
-35 to -60
0.22 to 0.01
Human Tissue
-30 to -40
-40 to -50
0.12 to 0.04
Blood Plasma
-10 to -25
-20 to -35
1.03 to 0.22
Vaccine
-30 to -40
-40 to -50
0.12 to 0.04
