In DLLME-SFO, extraction time is defined as interval time
between injecting the mixture of disperser solvent and extraction
solvent, before starting to centrifuge. The effect of extraction time
was studied over the range of 0–25 min, with the other experimental
conditions remaining constant. The obtained results showed
that the extraction time did not have significant influence on the
ICP signals of the metal ions. Because of the infinitely large surface
area between extraction solvent and aqueous phase after the formation
of cloudy solution, the complexes were formed instantly
and diffused into extraction solvent quickly. Subsequently, equilibrium
state is achieved quickly after injection of the extraction solvent
into the sample solution. Thus, the most important advantage
of DLLME-SFO is time independence of the method. In this method,
time-consuming steps are centrifuging of the sample solution in
the extraction procedure, which is about 5 min and solidification
of 1-undecanol, which is about 8 min.