The extraction unit was filled with 50L of a sodium hydroxide
solution (pH 13) which acted as acceptor phase. Later on, the polymeric
membrane was properly placed and fixed by displacing the
external body of the unit through the internal one as it is described
elsewhere [24]. In these conditions, the extraction unit remained
completely closed during the extraction. Afterwards, the pores of
the membrane were impregnated with octanol (forming the SLM)
and the unit was directly immersed in 20mL of the aqueous standard
or sample. The extraction vial was finally located in amagnetic
stirrer, the extraction of the analytes taking place at 500rpm during
45 min.