Chapter 5: Using Your Freeze Dryer
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38
Original instructions
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.
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
≤ 0.040 mbar
Milk
-5 to -13
-15 to -23
1.65 to 0.77
Fungi
≤ -40
≤ -50
≤ 0.040
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
When the vacuum control is set to operate at less vacuum (higher pressure), the ice
holding capacity of the collector may be decreased. This can be improved by
installing a baffle in the collector. See
Appendix A Freeze Dry Components
for the
baffle part number. See
Chapter 3: Baffle Installation
for proper positioning of the
baffle in the collector chamber.
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 or in the center of the collector chamber. 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 is typically at least 10° to 20°C below the eutectic or collapse
temperature of the sample.
Adding Sample
The following procedure should be followed when using chambers or manifolds
with sample valves in the freeze dry process:
1.
Connect a pre-frozen sample to a sample valve on the drying chamber or manifold
using an adapter. Turn the plastic valve knob to the “VACUUM” position to open
the valve, which connects the attached sample to system vacuum. The bevel on the
knob should be positioned toward the sample port to apply vacuum to the sample.
