2.3.2. Back extraction procedure
A 1 mL aliquot of aqueous sodium hydroxide (0.1 M) was added
to the diethyl ether extracts. The resulting mixture was sonicated
for 1 min, and then allowed to separate into layers. The upper ether
layer was discarded, and the lower aqueous layer was placed in a
40 C water bath to evaporate any residual diethyl ether. Finally,
the residue was transferred to a 5 mL volumetric flask and diluted
with water to scale.