2.4. Extraction procedure
A homogeneous sample solution (10.0 mL) containing the analytes
was placed in a 15 mL screw-cap conical-bottom graduated
plastic centrifugal tube. Using a 500 lL syringe, 350 lL of RTIL
was injected into the sample solution. Manual shaking (30 times
in 20 s) resulted in the formation of a turbid solution, which was
centrifuged for 8 min at a rate of 3500 rpm (1685g). The upper
aqueous solution was removed using a pipette, and the volume
of residual IL was almost 180 lL. Methanol was added to the IL residue
enriched with analytes to obtain a volume of 300 lL. Using a
25 lL HPLC microsyringe, 10 lL of the enriched solution was injected
directly into the HPLC system. All experiments were performed
in triplicate. The syringe was rinsed with methanol and
acetonitrile multiple times to remove residual analytes and IL.