Microscale liquid-liquid extraction can be efficiently performed with a conical vial. The two phases are introduced into the conical vial, closed with the corresponding screw cap and the mixture is shaken vigorously for a couple of minutes.
The stopper is opened and the two phases are allowed to separate. Then, with the aid of a Pasteur pipette fitted with a teat, the separation is carried out as follows:
If the organic solvent is denser than water, e.g. CH2Cl2, the pipette is introduced directly to the bottom of the vial and the entire organic phase is carefully sucked into the pipette.
Then, it is transferred to another container, which can be another vial, and in this way, both phases are perfectly separated.
If the organic phase is less dense than water, proceed as follows: The organic (upper) layer is sucked out slowly taking care not to remove the mixture, almost in its entirety, and with another pipette the aqueous phase.
To avoid suctioning the possible interface that sometimes forms, a small cotton ball can be placed on the tip of the pipette, resting it on the bottom of the conical vial.
The aqueous phase is transferred to another vessel and thus the two phases are separated.
As an alternative to this procedure, centrifuge tubes that also have a conical bottom can be used, performing a similar manipulation.