extracted twice with 2 mL of diethyl ether. The upper organic layer
(4 mL) was transferred into a clean tube after mixing. Afterwards,
the organic layer was evaporated to dryness in a stream of nitrogen.
The residue was dissolved in 1 mL of acetonitrile and 10-lL
aliquots were injected into the HPLC (Ozogul, 2004).