Traditional
Soxhlet Extraction
A Soxhlet
extractor is a piece of laboratory apparatus invented in 1879
by Franz von Soxhlet. It was originally designed for the extraction
of a lipid from a solid material. However, a Soxhlet extractor
is not limited to the extraction of lipids. Typically, a Soxhlet
extraction is only required where the desired compound has only
a limited solubility in a solvent, and the impurity is insoluble
in that solvent. If the desired compound has a high solubility
in a solvent then a simple filtration can be used to separate
the compound from the insoluble substance.
Normally a
solid material containing some of the desired compound is placed
inside a "thimble" made from thick filter paper, which
is loaded into the main chamber of the Soxhlet extractor. The
Soxhlet extractor is placed onto a flask containing the extraction
solvent. The Soxhlet is then equipped with a condenser.
The solvent
is heated to reflux. The solvent vapour travels up a distillation
arm, and floods into the chamber housing the thimble of solid.
The condenser, ensures that any solvent vapour cools and drips
back down into the chamber housing the solid material.
The chamber
containing the solid material slowly fills with warm solvent.
Some of the desired compound will then dissolve in the warm solvent.
When the Soxhlet chamber is almost full, the chamber is automatically
emptied by a siphon side arm, with the solvent running back down
to the distillation flask. This cycle may be allowed to repeat
many times, over hours or days.
During each
cycle, a portion of the non-volatile compound dissolves in the
solvent. After many cycles the desired compound is concentrated
in the distillation flask. The advantage of this system is that
instead of many portions of warm solvent being passed through
the sample, just one batch of solvent is recycled.
After extraction
the solvent is removed, typically by means of a rotary evaporator,
yielding the extracted compound. The non-soluble portion of the
extracted solid remains in the thimble, and is usually discarded.
Gerhardt Soxtherm
Soxhlet Extraction works on a similar principle with a few exceptions
and enhancements.
The Gerhardt
Soxtherm system does a hot extraction. By immersing the sample
in hot solvent the extractable materials are solubilzed much quicker
than in a cold extraction. The solvent is circulated to rinse
the extractable material into the bottom of the beaker. Finally
the solvent is removed by evaporation automatically and recovered
for safe disposal or reuse.
The Gerhardt Soxtherm has proved to be a fast, efficient and safe
method of soxhlet extraction for many hundreds of laboratories
all over the World.
The latest
development in the Soxtherm is the ability to control multiple
units from a PC using Soxtherm Manager.
Gerhardt supply
both traditional and automated extraction systems which can be
viewed on
our product pages.
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