Genevac HT-8 & HT-12 Series II Evaporating Systems
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Issue 1-9 – June 2008
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Getting the best from Auto Defrost Drain
What is Auto-Defrost & Drain?
Auto-Defrost and Drain is an option for the standard condensers on Genevac HT-4X, HT-8/12 series 2 and HT-
24 Workstation. Auto-Defrost and Drain enables the system to automatically drain the condenser of volatile
solvent(s) between stages in a method, and at the end of the method to fully defrost and drain the system with
no user intervention. When performing an intermediate drain (i.e. mid method) the system also does a short
defrost just in case residual solvent from the previous use has frozen in the outlet pipe of the condenser. The
intermediate drain can only be used to remove volatile solvents which do not freeze at temperatures above –
50°C.
Benefits of Auto-Defrost & Drain
The principal benefit of the Auto-Defrost and Drain function is to eliminate volatile solvent(s) from the
condenser. Volatile solvents boil off first from mixtures and are collected in the condenser. To remove the
higher boiling point solvents, low pressures must be achieved later in the process. However, dropping the
pressure causes the previously condensed volatile solvent to re-boil in the condenser, which generates a very
large volume of vapour which must exit through the pump. Until all this vapour has been pumped away (which
can take several hours) the system cannot achieve a lower pressure and so the higher boiling point solvents
cannot be boiled. The volatile solvents are therefore said to ‘spoil’ the vacuum level. Vacuum spoiling affects
final dryness of samples, or in the very worst cases, the ability to evaporate the higher boiling point solvent at
all. To overcome these problems the user always had to, until now, be present to drain the condenser after the
volatile solvents had been captured in the condenser. This draining operation can now be automated. An
additional benefit of Auto-Defrost and Drain is that volatile solvents are collected and can be safely disposed of,
reducing VOC emissions.
If your evaporator is equipped with the Auto-Defrost and Drain facility you will see the “Lyo Speed Enabled”
sign on your systems and the Auto-Defrost and Drain option will appear in the run menu when programming
methods.
Flexibility
A Genevac evaporator enhanced with Auto-defrost and Drain functionality can not only be used as part of the
LyoSpeed™ process, in addition it will also deliver improved results when working with any mixture of solvents
with differing boiling points.
When evaporating HPLC fractions, auto-defrost and drain will help achieve excellent final dryness. Mixtures of
DCM and DMSO or DMF, are almost impossible to evaporate without draining the cold trap once the DCM is
removed, and before tackling the higher boiling point solvent. This is now possible with a system which is Auto-
defrost and Drain enabled.
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