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Solvent
extraction is a method for separating mixtures by using the differences in
the solubilities of the components.
In
1879 German chemist, Franz von Soxhlet, pioneered extraction technology by
developing a solid-liquid extraction apparatus that carries his name.
Placing the sample in a paper thimble and placing the thimble in the
Soxhlet flask accomplishes Soxhlet extraction. Solvent in the reservoir
(round bottomed flask) is gently boiled. A water-cooled condenser from
which solvent drips into the thimble and contacts the solid sample
condenses vapors. When the siphon tube level is reached, solvent in the
thimble is returned to the reservoir. The solvent flask now contains
solvent and solute. In gravimetric analysis the solvent is driven off, the
solute is weighed, and the results are calculated.
A
century after Soxhlet developed his extraction system, Edward Randall, a
chemist from California, was attempting to make his laboratory more
responsive to his client’s needs. A major portion of his business came
from testing meat samples for fat, protein and moisture. His customers
were always looking for faster turn-around times. Fat analysis required
overnight Soxhlet extraction and thus delayed Randall’s reporting
results.
Randall
designed and patented a unique method, which physically lowered the
extraction thimble directly into the flask containing the boiling solvent.
Most of the extractable materials readily passed from the sample and
dissolved in the organic solvent (similar to a tea bag in hot water). To
remove the residual extractable material, it was necessary to raise the
sample- above the boiling solvent and then drip freshly condensed solvent
through it.
Randall’s
two-step extraction procedure reduced fat extraction time to less than one
hour per sample. His research publications showed that the Randall
extractor obtained results equivalent to Soxtec and Goldfisch with only 30
minutes of extraction time.
Tecator
subsequently acquired the rights to his patent and began production of the
Randall Fat Extractor Tecator engineers further developed a more advanced
system, the Soxtec, based on the Randall method.
Foss
has an extensive library of Soxtec Applications available.
A few of these applications are listed here for easy reference.
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Applications
