2.3.1. General procedure for carrier mediated HF-LPME
The HF was cut into 8-cm pieces and impregnated with 10%
Aliquat-336 in 1-octanol to fill the pores with the solvent. A 100-
mL Hamilton HPLC syringe (Bonaduz, Switzerland) was employed
to introduce the aqueous acceptor solution (25 mL 1 mol L1 NaOH
and NaCl) into the lumen and its needle was inserted into the
lumen of the HF. The other end of the HF was connected to a
medical syringe needle in order to support it. The ends of both
needles pierced through the silicon septum of a 20-mL glass vial
cap and the U-shaped membrane portion containing the acceptor
phase was immersed in 20 mL of the prepared real sample solution
(donor phase), which was adjusted to pH 8.0 in a 20-mL glass
vial containing a 10-mm magnetic stirrer. During the extraction
process, the sample solution was stirred magnetically at 800 rpm.
Once this time elapsed, the analyte-enriched acceptor phase was
withdrawn into the microsyringe and subsequently 20 mL of the
extracted solution was injected into the HPLC instrument