Thermo Scientific VARIOKLAV 25T Operating Manual page 24

Liquids in open or slightly closed vessels:
Sterilize liquids in open or slightly closed vessels.
DANGER
Do not sterilize pressure-sealed vessels.
Explosion hazard!
Watch for broken glass!
Scalding hazard!
CAUTION
When sterilizing liquids:
Do not fill the vessels more than two-thirds full,
as otherwise liquids may boil over.
Liquid volume may be lost when sterilizing liquids in open vessels.
During the heating phase, the volume of liquid in the vessels will increase.
Water vapour will condense off the surface of the vessels. The volume will
expand, and bubbles will form during boiling. During the cooling phase, the
volume of water will decrease. The loss of liquid will depend on the recooling
process, the cooling time, the shape of the vessel and the filling volume. Up
to 12 % of the liquid can be lost as a result of "evaporation", particularly if
liquids are held for a long time in the hot sterilizing chamber (8).
The loss involved is reproducible, providing the sterilizing conditions are the
same. For this reason, any loss can be compensated when producing
culture media by adding the appropriate amount of liquid.
Liquid loss can be reduced by covering vessels with aluminium foil or a
cellulose stopper. If you use laboratory flasks made of boron silicate glass
(such as DURAN
more than one turn.
For sterilizing liquids, a reference temperature is determined.
With media temperature control expansion option:
♦ Measure the media temperature in a reference flask using the flexible
temperature sensor (Chapter 5.2.3).
♦ Select the Liquids program.
Heat-sensitive culture media:
Culture media can discolour when subjected for too long to the effects of
temperature. There may also be a loss of quality, to the extent that the
culture medium becomes unusable. We therefore suggest you take note of
the following points to facilitate gentle treatment of culture media:
♦ Quickly preheat the liquid outside the sterilizer.
♦ Use small vessel sizes (max. 1,000 ml) and modest filling levels (vessels
max. half full).
♦ Do not make full use of the capacity of the sterilizer.
♦ Select the Liquids RM or Liquids RO program, if present.
This will keep heating time, equilibration time and the cooling phase as short
as possible.
Further remedies:
Expansion level with magnetic stirrers integrated into the sterilizing chamber,
separate steam generator or sterile steam for fast heating.
03/2007
5 Preparing for sterilization
®
), you may loosely fit the screw cap or screw it on by no
24
DA0621_a/