Labconco FreeZone 1 Liter Benchtop Freeze Dry Systems 7740071 - Manual (Page 8)

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Chapter 1: Introduction
vacuum in the system may recover before adding another sample
to the system. If the vacuum does not recover, the capacity of the
freeze dry system has been exceeded and the sample should be
removed.
If there is a problem with a particular type of sample melting when
placed on the freeze dry system, dilution of the sample with more
water or providing some insulation around the flask to decrease the
rate of heat absorption by the sample may help. If the eutectic
temperature of the sample is –40 to –60°C, the freeze dry system
selected for use must be equipped with cascade type refrigeration
so that the collector temperature can be cooled to below –75°C, or
a dry ice/solvent trap may be used between the collector and the
vacuum pump.
Samples Containing Volatile
Substances
In certain cases the solvent in a sample to be freeze dried may
contain volatile components such as acetonitrile, methanol, acetic
acid, formic acid or pyridine. In addition to these substances
having an effect on the eutectic temperature, they may increase the
vapor pressure at the surface of the sample. Also, compared to
water, they will require the absorption of less heat for sublimation
to occur. Hence, samples that contain volatile substances will have
a greater tendency to melt, particularly when placed in flasks or
exposed to room temperature. If a sample containing a volatile
substance tends to melt when placed on a freeze dry system,
dilution of the sample with more water will help keep the sample
frozen. For example, a 0.2M solution of acetic acid is much easier
to freeze dry than a 0.5M solution.
About This Manual
This manual is designed to help you learn how to install, use, and
maintain your Freeze Dryer. Instructions for performing routine
maintenance and making minor modifications to your Freeze Dryer
are also included.
Chapter 1: Introduction provides a brief overview of the Freeze
Dryer, explains the organization of the manual, and defines the
typographical conventions used in the manual.