Labconco FreeZone and FreeZone Plus 6, 12 and 18 Liter Freeze Dry Systems 79600 Series - Manual (Page 32)

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Chapter 4: Using Your Freeze Dryer
Product Service: Domestic 1-800-522-7658, International 816-333- 8811
Setting the Operating Vacuum Level
The vacuum level may be set by the user to optimize the freeze dry
process. Normally, the sublimation rate will increase if there is less
vacuum (a higher pressure) in the Freeze Dryer. A good starting
place is to set the vacuum so its level is equivalent to about 10°C
colder than the eutectic or collapse temperature of the sample.
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
manifold 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, the ice
holding capacity of the collector may be decreased. This can be
improved in non-cascade models by installing a baffle in the collector.
See Appendix D Freeze Dryer Accessories for the baffle part number.
See the section titled Baffle in this chapter for proper installation.
Some guidelines for setting the Freeze Dryer are shown below.
These show pre-freezing temperatures and vacuum levels. 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 and Colder -50°C &
Colder
0.040 mBar &
Lower
Milk -5 to -13 -15 to -23 1.65 to 0.77
Fungi -40 and Colder -50 & Colder 0.04 and lower
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
Pre-Freezing Samples
Appropriate containers for freeze drying include ampules, serum
bottles, and wide mouth freeze drying flasks. Shell freezing of
samples is recommended for wide mouth freeze drying flasks.
Smaller samples in ampules and serum bottles may be frozen in a
freezer. The sample container size should always be at least two to
three times the sample size (i.e., 40 ml samples should be prepared
in 80 ml containers or larger). The temperature required for pre-
freezing is dependent on the characteristics of the sample. Pre-
freezing temperature typically is at least 10° to 20°C below the
eutectic or collapse temperature of the sample.