Understanding that PFAD still contains a
valuable amount of squalene, while the demand of this compound remains high in
the decreasing availability of its main source, shark liver oil, has heightened
the motivation to extract squalene from PFAD. Previous studies have shown that
extracting squalene from PFAD can be achieved using dichloromethane (DCM) as
the solvent (Yusuf, 2015)

The principle of liquid-liquid extraction
(LLE) is partitioning the sample between two immiscible liquids or phases
according to each compound solubility. The solvent used is mostly the
combination of water and an organic solvent due the difference in polarity in
water and most organic solvents. (Dean, 2010)

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The two combination of water and organic
solvent will form two separate layer of aqueous and organic phase. The solvent
of higher density will be at the bottom of the flask while the lighter solvent
will be at the top. Polar compounds will be attracted to the similarly polar
water molecule and ultimately absorbed in the aqueous phase. On the other hand,
non-polar compounds will be in the organic phase. This phenomenon is based on
the general principle of solubility “like dissolve like” where polar solutes can dissolve in polar solvents and non-polar solutes can dissolve
in non-polar solvents, but polar solutes rarely dissolve in non-polar solvents and vice

Polar molecules have a strong attraction between each other due to their
dipoles whereas non-polar molecules have none. Non-polar solute will never be
dissolved in polar solvent because polar molecules are attracted to each other
while there is none towards the non-polar molecules. However, non-polar solute
can dissolve in non-polar solute because it is not necessary to compete for
attraction between non-polar molecules as there is none.

In this study, soap, glycerol, ethanol and
other polar compounds were expected to be in the aqueous phase at the top layer
whereas squalene is expected to be at the bottom layer with the organic solvent
due to its low polarity.