However, instead ofmagnetic stirring, ultrasonic
energy (UA-SFODME) [14], vortex mixing (VA-SFODME) [15]
or the addition of a dispersive solvent (DLLME-SFO) [16] can also
be used. We tested these modes of SFODME for determination of
1 × 10−8 mol phosphate using 1-undecanol as the extraction solvent.
In this step, the main criterion was the extraction time. The results obtained
(Fig. 1) indicate that conventional SFODME is the slowest
mode.We therefore excluded this technique from further studies. Similarly,
we also excluded ultrasound-assistedmode,which requiresmore
than 20 min. The vortex-assisted mode proved to be the fastest, but this
mode was more suitable for small sample volumes of 5–10 mL. Moreover,
due to the stability of the cloudy state formed, it is necessary to
use centrifugation for phase separation. Therefore, DLLME-SFOwas chosen
for further detailed study.