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Lyophilizer Procedure and Theory |
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The lyophilizer is turned
off when it is not in use. Keeping the system turned off will
prolong the life of the system. Users must
avoid turning on the system and forgetting their sample for several
days. One unit is located in building 95 room W357 and other in W186.
All users must complete the notebook indicating their name, use time, and any problems.
Procedure
1. If the unit is on and in use place a sample in the system.
After the sample is in place close all valves from other samples
and open the valve for the specific sample. After the vacuum is reached
for the sample open valves to the other sample. If vacuum gauge
is not working the vacuum level is indicated by sound from the pump.
2. If the unit is turned off. Look inside to see if there is any
water in the bottom of the tank. If there is water,
drain it out by removing the rubber stopper by the compressor. Each unit has a slightly different protocol.
3. When the vacuum is adequate put a sample on the
system. Note that neither the temperature or vacuum gauges are
functioning on some units.
4. When finished, remove the
sample
a. If there are other sample drying
leave the system running.
b. If there are no other samples
on the system: Turn off the vacuum pump. Open a valve to bring the system
to atmospheric pressure. If the valve is not opened oil
will back flow from the pump
into the system. Turn off the refrigeration system.
What is Lypohilization --The first step in the lyophilization of a product is
to convert it into a frozen state. In obtaining the frozen state
the product must not be altered as a result of the process.
It is important that during the freezing process
that the solvent ( water) is crystallized. The formation of ice
crystals results in a separation of the solutes and the solvent.
Since the concentration of the solvent is generally greater than
that of the solutes, the formation of ice forces the solutes into
a region between the crystals known as the “interstitial”.
Thus the second function of the freezing process is to cause a
separation of the solutes and the solvent.
Sublimation:
Sublimation is a process in which a substance, such as ice, goes
from a solid to a gas without going
through a liquid phase. While sublimation can occur at atmospheric
pressures, the process is quite slow. We can increase the rate
at which the molecules sublimate from the surface by decreasing
the pressure above the ice surface. This is accomplished by placing
the frozen material into a chamber and removing the gases to create
a vacuum.
Desorption: While
the sublimation or primary drying process removes most of the
water from frozen matrix, there still can be greater that 5% moisture
in the product. Moisture contained within the cake is referred
to as “absorbed” water while water on the surface of
the cake is defined as adsorbed” water.
Vacuum System: The freeze-dryer is equipped with a mechanical pumping system
that removes the non-condensable gases. With oil sealed mechanical
pumps, one must be careful to operate the dryer so that no hydrocarbon
vapors from the pump can “backstream” into the drying
chamber. The user must also be certain to remove the sample
and vent the chamber to atmosphere before turning off the vacuum
pump. There are two more freeze-dryer systems.
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Manufacturer |
Date Purchase |
Cost |
Location |
| U303776 |
LabConco |
17-Mar-93 |
$3,694.00 |
225 |
| U303716 |
R. & S |
1-Aug-82 |
$6,661.00 |
W357 |
| U407453 |
LabConco |
30-Jul-05 |
$5,632.55 |
W357A |
