PP micropipette tips (0.5–10 mL, Part No. 959, Kartell, Noviglio,
Italy) were used as extraction units. For
filling purposes, the tips
were attached to a 2–20 mL micropipette (Biohit ProLine Plus,
Biohit, Helsinki, Finland). A detailed protocol describing the
procedures of extraction unit
filling, m-EME across FLMs and
analysis is given in Table 1. The tips were
filled successively with
appropriate volumes of aqueous donor solution, organic solvent
(acting as the FLM) and aqueous acceptor solution to form a threephase
extraction system. After
filling the tip with all respective
solutions, the tip was penetrated with a stainless steel needle
(0.45 mm OD) in its upper part (13 mm down the upper rim) and
was removed from the micropipette. This hole ensured equilibrium
of ambient air pressure on both sides of the system during the
removal of the tip from the micropipette and thus stability of the
three-phase microextraction system