Labconco FreeZone 4.5 Liter Freeze Dry Systems 77510 Series - Manual (Page 23)

Chapter 4: Using Your Freeze Dryer
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will show the actual temperature of the collector. When the vacuum in the system
is above 5 mBar the vacuum display will indicate “HI.” At 5 mBar and below, the
display will show the actual vacuum.
When the system vacuum is between 0.450 and 0.133 mBar, the lower green
vacuum graph LED will flash. When the system vacuum level is <0.133 mBar, the
green LED will be lit steadily indicating that samples may be added.
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 by installing a baffle in
the collector. See Appendix D Freeze Dryer Accessories for the baffle part
number. Position the baffle with the notches in the tube downward straddling the
collector coil and fittings on the bottom of the chamber.
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